What is the estimated blood loss of a 75 kg man who sustained a Class 2 shock?

Considerations in the Management of Shock in the Pediatric Trauma Patient

Authors: N. Ewen Wang, MD, Assistant Professor Surgery, Assistant Professor Pediatrics, Associate Director, Pediatric Emergency Medicine, Stanford University, Palo Alto, CA; Carmie Chan, MD, Stanford University, Palo Alto, CA; Shaun Anand, MD, Stanford University, Palo Alto, CA; Bernard Dannenberg, MD, FAAP, FACEP, Stanford University School of Medicine, Division of Emergency Medicine, Palo Alto, CA.

Peer Reviewer: Meta Carroll, MD, Pediatric Emergency Medicine, Northwest Acute Care Specialists, PC, Emanuel Children's Hospital and Salmon Creek Hospital, Legacy Health System, Portland, OR and Vancouver, WA.

In a child who is critically injured there is the potential for many serious or life-threatening injuries. The initial focus must always be to stabilize the child's airway and breathing and, then, rapidly identify shock and aggressively correct volume deficits. Failure to recognize and manage shock is a major cause of preventable deaths in pediatric trauma patients. Knowledge of the unique physiologic and anatomic features of children will allow the clinician to rapidly assess and effectively manage the pediatric trauma patient in shock. This article will review the unique aspects of children, pediatric anatomic and physiologic differences that affect recognition of shock in children versus adults, and how these differences translate into patient management strategies. — The Editor

Introduction

The care of a trauma patient must always proceed from assessing airway, breathing, and circulation to identification and delineation of all injuries and appropriate management. Although pediatric patients are far more likely to suffer problems with inadequate ventilation than circulatory failure,1 inappropriate resuscitation or unrecognized shock is a major cause of preventable death.2 The management of the pediatric trauma patient is a challenging clinical task, made more difficult with the emotional impact of an injured child on families and emergency department (ED) staff. A patient's vital signs must be considered in conjunction with age, as well as other factors. Age variations in vital signs and weight, as well as the presence of fever, crying, or an inappropriately sized blood pressure cuff can all affect vital signs, complicating the picture, and making shock challenging to recognize. Care of the pediatric patient requires knowledge of appropriately sized equipment for any given age, as well as excellent ED organization of supplies, so that immediate access to equipment is ensured.

Injury mechanisms for children differ from those of adults. The term "unintentional injury" was coined as an alternative to "accident" to emphasize that these injuries can be prevented. Unintentional injury represents the leading cause of death in all children except those younger than 1 year3 and accounts for more deaths than all other mechanisms combined. Childhood injury follows different patterns depending on age, sex, and developmental stage. In infants and toddlers, falls are a common cause of severe injury, while older children and adolescents experience severe injury from bicycle and motor vehicle accidents. Within the category of "unintentional injury," motor vehicle traffic accidents accounted for 30.9% of fatalities in the 1-to-4-year age group; the rate increased steadily and accounted for 72.3% of fatalities in patients aged 15 to 24 years from 1999-2003. Children aged 1 to 4 years had significant rates of death caused by drowning (26.7%) and fire/burns (14.7%); children aged 5 to 9 years had half the death rate by drowning (13.2%) and similar rates of death by fire/burns (12.6%). Homicide, often traumatic in nature, is the second cause of death in children and young adults aged 15 to 24 years. Suicide is the third ranked cause of death in children and young adults aged 10 to 14 years and 15 to 24 years.3

Definition of Shock

Shock is defined as inadequate perfusion and oxygen delivery to tissues to maintain their metabolic demand. Compensated shock is a clinical state in which patients maintain normal blood pressure by increasing cardiac output, resulting in tachycardia; however, organ perfusion is still insufficient for the metabolic demands of the body (Figure 1). Decompensated shock is a loss of compensatory mechanisms with resulting hypotension. Heart rate is no longer adequate to maintain perfusion to end organs. At this point blood pressure begins to drop (Figure 2).

Figure 1. Compensated Shock

Figure 1. Compensated shock occurs when blood is being lost and tachycardia results without hypotension. Although blood pressure is maintained, organ perfusion is inadequate for metabolic needs.

Figure 2. Decompensated Shock

Figure 2. Decompensated shock occurs when ongoing blood loss decreases stroke volume and the heart's ability to compensate. Blood pressure fails.

Differences in Vital Signs

Children are continually growing both physically and emotionally. They are different from adults with respect to their anatomy, physiology, and maturity. Before discussing these differences, it is important to review normal vital signs based on age. Even the approximate weight of a child can be challenging to estimate. A useful formula for calculating weight of a child younger than 8 years is as follows:

Weight (kg) = (2 x age (in yrs)) +8

The lower limits of normal blood pressure can be calculated from the following formula:

Systolic blood pressure = 70 + (age(in yrs) x 2).

See Table 1 for age-related normal vital sign values.

Table 1. Normal Vital Signs in Pediatric Patients

A length-based resuscitation tape and associated color-based code cart, such as the Broselow system, provides accurate information for a given weight.6 The Broselow tape is placed alongside the child and provides an approximate weight, based on length of the child, along with weight-appropriate medication doses and equipment sizes. Each weight range corresponds to a particular color, and when the Broselow tape is used in conjunction with a code cart with drawers also arranged by color, clinicians can find appropriate equipment quickly and easily. A standard pediatric code cart is often organized by intervention, so that one drawer has intubation supplies, while another has supplies for intravenous access. However, a study performed in 2005 found that in a simulated code scenario, practitioners were able to find equipment faster using a Broselow cart compared with a standard pediatric code cart.7

Differences in Physiology

Along with important anatomic differences between adults and children, there are also numerous physiologic differences. Some of these distinctions (e.g., increased physiologic reserve and vascular compliance in children) allow for increased likelihood of survival in times of severe stress. Other differences, such as decreased ability to regulate body temperature, make children more vulnerable to the environment. To effectively manage pediatric trauma, the differences in the cardiovascular system, blood volume, temperature regulation, and response to shock must be appreciated.

The compensatory cardiovascular mechanisms are greater in children compared with adults. Blood pressure is proportional to the cardiac output and systemic vascular resistance. Cardiac output is influenced by stroke volume and heart rate. Stroke volume is dependent on preload, afterload, and contractility. Blood loss decreases preload, or the circulating volume of blood. With no compensation for this, cardiac output will drop. Because stroke volume has been shown to be relatively fixed in children,2 the pediatric patient's compensatory mechanism to maintain cardiac output is increased heart rate.8 This is the first defense against blood loss. However, when blood loss reaches 25% to 30% of a child's blood volume, peripheral vasoconstriction occurs, due in part to the greater elasticity of children's vasculature. Vasoconstriction increases the venous blood return, bringing more blood back to the heart. The combination of tachycardia and vasoconstriction maintains blood pressure in the near normal range. Children can maintain their blood pressure until they lose a significant amount of blood.2 When compensatory mechanisms are overwhelmed by large losses, however, the heart rate increases and blood pressure begins to drop, quickly leading to decompensated shock. In children, hypotension is a late and ominous finding.

Blood pressure is influenced by cardiac output and the systemic vascular resistance. Cardiac output is influenced by the stroke volume and the heart rate. In children, the stroke volume is relatively fixed until circulating volume is decreased 30%-40%. Stroke volume is affected in turn by preload (or circulating volume), afterload, and contractility.5

The circulating blood volume of a child is significantly lower than an adult's. The blood volume of a child is estimated at 80mL/kg.2 In very young children this formula should be kept in mind because as little as 250 mL of blood loss in the field may represent an entire circulating volume.

A special consideration in the management of shock in children is the importance of temperature regulation. Children have a larger surface-area-to-weight ratio, less subcutaneous tissue than adults, and a decreased ability to regulate their core temperature.9 As a result, hypothermia can result. With the subsequent release of catecholamines and shivering, an existing metabolic acidosis will worsen. Confounding this problem is massive volume resuscitation with normal saline or lactated ringers.2 Warmed resuscitation fluids and environmental temperature control (e.g., use of a "bear hugger") is essential. Hypothermia, if not identified and treated, may lead to shock that is refractory to fluid resuscitation.

Recognition of Shock in a Child

It is often challenging to recognize signs of shock in a child. Children have tremendous physiologic reserve and may maintain a normal blood pressure until a substantial amount of blood is lost. Hypovolemic shock should be considered if the heart rate is greater than 10% of normal for age and blood pressure is less than the 5th percentile for their age (calculated by formula: 70 + (2 x age in years ).2 However, signs of shock present in adults, including hypotension and decreased urine output, may not occur in children until they lose up to 45% of their blood volume.2 In fact, the well-known signs of shock often manifest only when the state of compensated shock transitions to the state of decompensated shock. Once a patient progresses to decompensated shock, aggressive interventions must be undertaken to prevent progression to cardiac arrest.5 If decompensated shock is allowed to persist, ischemia and hypoxia will result in bradycardia and cardiac arrest.

The first indicator of hypovolemic shock in a child is tachycardia. Blood pressure is considered an inadequate measure of volumes status or resuscitation endpoint. The heart rate increases to maintain stroke volume as mentioned earlier. When this is inadequate, the systemic vascular resistance will increase. When both of these mechanisms are overwhelmed, the blood pressure will drop. If bradycardia develops, it may represent irreversible shock.8 The key is to maintain a high degree of suspicion early in patient management, and to constantly re-evaluate the effects of the resuscitation.

Mental status changes may also be an indicator of shock. It is not uncommon for children to regress to a younger developmental stage during the stress of trauma.2 For example, a 3-year-old child, previously speaking short sentences, may refuse to talk. This normal regression must be differentiated from a change in mental status due to CNS hypoperfusion. Knowledge of developmental milestones may help differentiate such behavioral regression from hypoperfusion. The heart, brain, and kidneys are organs that maintain their perfusion until significant hypovolemia has occurred. Analyzing how well these systems are affected and noting skin perfusion, may help determine the initial volume status of the patient upon arrival, as well as the effect of ongoing resuscitation efforts.8

Skin color, temperature, presence or absence of diaphoresis, and capillary refill are important to observe during a trauma resuscitation. Upon entering the trauma bay, a quick glance at the patient's appearance can provide immediate and useful information. Diaphoresis may be a warning sign that the child is physiologically stressed. Cool, clammy skin may be the first dermatologic manifestation of shock. The skin may become pale, cold, and cyanotic as shock worsens.4 Furthermore, capillary refill is normally less than two seconds in a well-perfused child. As peripheral perfusion decreases, the capillary refill becomes prolonged. Skin findings should be reassessed frequently throughout the resuscitation.

Urine output also can be used to monitor shock after the initial resuscitation. Adequate urine output is 0.5 mL/kg/hr in adults. In the pediatric patient population, the normal urine output is 2 mL/kg/hr in infants, 1 mL/kg/hr in children, and 0.5 mL/kg/hr in adolescents.4

Initial Resuscitation

Once the clinical signs and symptoms of shock are anticipated or have been recognized, resuscitation of the child should begin immediately. Obtaining venous access is, of course, essential in the resuscitation phase, and can prove challenging in children. The Advanced Trauma Life Support® (ATLS®) algorithm recommends two attempts at peripheral intravenous access. If no peripheral access can be established within 90 seconds, then an intraosseus (IO) catheter should be considered in the child with clinical evidence of shock. Although previous ATLS recommendations advised IO catheters only in children younger than 6 years, IO catheters may be considered for use in older children and even adults, but may be more difficult to place. If an IO catheter is not possible, then central venous access or peripheral venous cutdown is recommended.10

Intraosseous Catheters

IO lines can be used as temporizing measures during a resuscitation, but should not be considered as long-term access and should be replaced with more definitive intravenous access as soon as possible.11 In theory, any noninjured superficial bone can be considered for IO insertion. While the most common site is the proximal tibia, other possible sites include the distal tibia, distal femur, sternum, distal radius, os calcis, and shoulder.12 Resuscitation fluids and medications may be given in large volumes through an IO catheter. The only contraindications to IO insertion are fracture of the bone, prior IO insertion attempt, or infection at the insertion site.

IO catheters have proven to be useful in several studies, especially during trauma resuscitations when circulatory collapse makes intravenous access more difficult.12,13 In newborns, IO cannulation is accomplished more quickly than umbilical vein access. The documented complication rate of IO access is low; the most common reported long-term complication is osteomyelitis, with the risk of infection estimated around 0.6%.12 The most frequent complication is extravasation of fluid, due to incomplete cortex penetration with the needle, penetration through the second cortex, or extravasation through a bony defect or through a nutrient vessel foramen.14, 15 Extravasation may lead to compartment syndrome or skin necrosis, especially with infusion of catecholamines. The risk of such infiltration increases with prolonged use of the IO line and high-pressure infusion. Other potential complications include bony fracture, compartment syndrome, and difficulties with infusion due to a bent needle or bone marrow clogging the catheter. Any IO line placed during emergency resuscitation should be replaced as soon as possible and monitored frequently during the resuscitation.

The equipment needed for an IO line placement includes a sturdy needle with a stylet, and a syringe for aspiration. Multiple commercial needles and kits are available specifically for IO line insertion. These are listed in Table 2. Standard needles used to draw medications are not adequate because they are not strong enough to penetrate bone. The use of spinal needles should be avoided, as they are too long, bend too easily, and occlude with clotted blood. Some drills are also available to simplify penetration through the bony cortex. In many areas, prehospital personnel are trained to use IO needles in the field for injured children.

Table 2. IO Needles Available

When inserting an IO catheter at the proximal tibial site, place the catheter 1 to 3 cm distal to the tibial tuberosity and over the medial aspect of the tibia. The bevel of the needle should aim away from the joint space, toward the foot, to avoid the growth plate. As the needle penetrates the bony cortex and slides into the bone marrow, there will be a sudden decrease in resistance, and the needle will stand upright without support. When a syringe is attached to the catheter, bone marrow will be aspirated and can be sent for laboratory studies such as hemoglobin level, chemistry panels, coagulation studies, and type and cross. Verification of correct IO placement relies on ease of infusion, lack of infiltration of IV fluids, and radiographic confirmation. Steps for insertion of intraosseous line at the tibial site are as follows:

1. Locate landmarks.

2. Place towel behind knee.

3. Prep skin.

4. With nondominant hand, stabilize proximal tibia. Be sure not to place hands directly behind insertion site.

5. Grasp IO needle within palm of hand and direct perpendicular to bone.

6. Advance needle with twisting or rotary motion.

7. Advance until decreased resistance felt. You also may feel a "crunchy" texture as the needle moves into bone marrow. This distance is usually 1 cm in an infant or young child.

8. Remove stylet (not needle).

9. Aspirate using a 5-10 mL syringe.

10. Secure needle.

Central Venous Access

If peripheral venous access cannot be obtained or additional access is needed, then central sites should be considered. As in adults, the sites for central access include the femoral vein, internal jugular (IJ) vein, and subclavian vein. The most commonly used is the femoral vein, and it is recommended for several reasons. First, it is usually easily accessible even with ongoing resuscitative efforts at the head of the bed. Second, it is a large vein with easily identified anatomic landmarks. And third, the femoral vein is easily compressed with direct pressure in cases of bleeding. Some authors warn against use of the femoral vein in infants and children, except in situations of dire emergency, because of the high incidence of thrombosis and possible ischemic loss of the limb and growth discrepancies.10,18 In contrast, three studies performed in the intensive care unit setting, found no life- or limb-threatening complications from femoral central line placement, and all recommended femoral central venous catheterization as a feasible and preferred central line site.19-21 Another study performed in a pediatric ED documented only four cases of short-term, easily reversible complications from femoral central lines. These included leg swelling and hematoma formation. In this study, 83% of 121 patients had a femoral line placed, 10% had subclavian lines, and 6% had IJ lines.18 Research also has shown that femoral central lines do not have a higher incidence of complications than other sites, even with long-term use.14

In accessing the femoral vein, Roberts and Hedges recommend using the standard adult technique only in children weighing more than 1500 grams.16 If a child weighs less than 1500 grams, one should consider using a single-lumen catheter (either 3-French or 24-gauge) to prevent complete occlusion of blood flow through the femoral vein. If clinically feasible, the patient should be placed in a negative Trendelenburg position to increase flow through the femoral vein, keeping the leg straight and placing a roll of cloth under the hip to extend and straighten the vein, if possible. (See Figure 3.) Keeping the fingers on the femoral pulse, the needle should be introduced medial to the artery, about 1-2 cm below the inguinal ligament. In infants, the vein is about 4-5 mm medial to the artery; in adolescents, the vein lies 10-15 mm medially. Maintaining slight negative pressure on the syringe, the needle is advanced until venous blood flows freely into the syringe. The syringe must be carefully removed from the syringe while steadying the needle with the other hand. Then, the wire should pass easily through the needle; if any resistance is met, it may be necessary to withdraw and adjust the needle angle, or even re-attach the syringe to ensure placement in the vein. If there is any question about intra-arterial placement, remove the wire and hold firm pressure to prevent hematoma formation. In a less emergent situation, intra-arterial placement also can be identified by passing a small catheter over the wire to measure pressure.

Figure 3. Femoral Cental Venous Line

Figure 3. The landmarks for placement of a femoral cental venous line include the inguinal ligament and the femoral artery. In infants, the femoral vein lies 4-5mm medial to the artery; in adolescents, the vein lies 10-15mm medial to the artery. The vein should be entered 1-2 cm below the inguinal ligament. Reprinted with permission: O'Neill J. Principles of Pediatric Surgery. 2nd; Mosby;2003.

After passage of the wire, use a scalpel to make a small nick at the skin, then remove the needle only, keeping a firm grip on the wire and making sure not to change position. Pass the dilator over the wire, and remove the dilator while keeping the wire in place. Thread the catheter over the wire into the vein, making sure that the end of the wire has passed through the distal catheter tip, so the wire does not get lost inside the vein. Once the wire is removed, flush all ports. Assuming blood is easily aspirated and saline flushed easily through each port, the catheter then can be secured with sutures or staples, and a clean dressing applied.

The internal jugular is often the second choice for central venous lines, because the vein is the largest available for percutaneous access. (See Figure 4.) However, positioning can be difficult, and landmarks challenging to identify on a child's neck. These difficulties are compounded by the presence of a cervical collar in trauma patients. The internal jugular vein is located just lateral to the carotid artery, within the carotid sheath. There are several approaches to the internal jugular, including anterior, median or central, and posterior approaches. The median or central approach is recommended in pediatric patients because of easier identification of landmarks, especially given the shorter necks of infants. The internal jugular vein lies within the triangle formed by the sternal and clavicular heads of the sternocleidomastoid muscle. The median approach utilizes the apex of this triangle as the entry site. The landmarks may be difficult to identify in children, therefore, it may be helpful to imagine a line from the mastoid process to the sternal notch; the apex of the angle should lie along the middle third of that line.16 The needle should be introduced at a 30-degree downward angle, aiming toward the ipsilateral nipple. Once the vein has been punctured, line placement continues using the Seldinger technique as detailed above. When the procedure is completed, the tip of the line should lie at the junction of the superior vena cava and right atrium. A chest radiograph should be ordered to confirm placement, as well as to rule out pneumothorax.

Figure 4. Internal Jugular Central Venous Line

Figure 4. In accessing the internal jugular vein, the needle should be inserted at the apex of the triangle formed by the clavicular and sternal heads of the sternocleidomastoid muscle (SCM). If these landmarks are difficult to identify, imagine a line between the mastoid process and the sternal notch; the apex should lie within the middle third of that line. Enter just lateral to the carotid pulse, aiming toward the ipsilateral nipple. Reprinted with permission: O'Neill J. Principles of Pediatric Surgery. 2nd; Mosby;2003.

The subclavian line is considered most comfortable for the patient. (See Figure 5.) However, the risk of complications is higher and is recommended only if other central line sites are unobtainable, especially in an emergency situation.16 One study in 2002 showed that subclavian central lines in pediatric patients are safe, especially in experienced hands, and should be considered first-line approach for central access. The most common complication was arterial injury.22 However, subclavian lines are still more frequently used in adults than in children.16 In children, the subclavian vein may be more difficult to access than in adults, due to the smaller caliber and more cephalad location under the clavicle. The typical infraclavicular approach to the subclavian vein carries a risk of hemothorax and pneumothorax, especially in younger patients, and generally is reserved for emergency situations in which percutaneous and other central venous approaches have been unsuccessful. In addition, subclavian access may be hindered by resuscitative efforts at the head of the bed, as well as the cervical spine immobilization devices in a trauma patient.

Figure 5. Subclavian Central Venous Line

Figure 5. In accessing the subclavian vein, the needle should be inserted at the distal third of the clavicle, in the groove formed between the pectoralis major and deltoid muscles. The needle should be aimed toward a finger in the suprasternal notch. Reprinted with permission: O'Neill J. Principles of Pediatric Surgery. 2nd; Mosby;2003.

If possible, the patient should be placed in the Trendelenburg position, with a towel roll placed under the shoulders and the head turned away from the side to be accessed. In general, the right subclavian vein is easier to access because the dome of the left lung lies more cephalad than the right side. In children, the approach for subclavian access is more lateral than in adults, and should start at the distal one-third of the clavicle, within the depression made by the pectoralis major and deltoid muscles. The needle should remain parallel to the frontal plane and directed under the clavicle toward a finger placed in the sternal notch. The bevel of the needle must be aimed caudad to direct the guide wire into the superior vena cava. During insertion of the wire, the cardiac monitor must be watched for any rhythm disturbance that may occur if the wire is inserted too far. The catheter is inserted via the Seldinger technique as described above. As with the IJ line, a chest radiograph must be obtained to verify placement and look for pneumothorax.

The appropriate size of the venous catheter depends on the age and weight of the child. In general, children younger than 6 months require a 3 or 4 French catheter, while children older than 6 months require at least a 5 French catheter. The catheter should be inserted to a length estimated by external measurement prior to insertion, and the position of any subclavian or internal jugular central line should be verified by chest radiograph.

Ultrasound-guided Line Placement

In challenging cases, there may be a role for ultrasound-guided line placement at peripheral or central sites. Data from large studies of pediatric patients are not available, but studies in adults show that ultrasound-guided line placement is particularly useful in obese or intravenous drug-using patients.23-25 When using ultrasound guidance, the linear ultrasound probe (7.5-8 MHz) is held transversely, and the vein is located by its thin wall and easy compressibility, as compared with the artery. Then, needle and catheter can be placed under direct visual guidance of the ultrasound.

Peripheral Venous Cutdown

Another option for intravenous access in any patient is the peripheral venous cutdown. A mainstay in the teaching of emergency trauma care, it is a technique that is rarely used in the ED setting. Venous cutdowns carry a higher risk of infections and a relatively short patency, but can be useful in an emergency situation where other methods of intravenous access fail. The most common site for a cutdown is the area just anterior to the medial malleolus overlying the saphenous vein. Other potential sites include the antecubital, basilica, or femoral veins. The major complication of a venous cutdown is line dislodgement, which can occur inadvertently and quite easily. This causes leakage of the infused solution into surrounding tissues. Thus, any infusion into a cutdown catheter must be set at a lower infusion volume, and a low osmolarity solution should be used to avoid phlebitis and infiltration. If a hypertonic solution infiltrates into tissues, compartment syndrome and tissue necrosis may result.26

The technique for pediatric venous cutdowns is similar to that used in adults. The advantage of using the saphenous vein at the medial malleolus is the lack of any major nerves or tendons in this location. Once a small transverse incision has been made, the vein is isolated and secured. A venotomy is performed, and the catheter then inserted and secured.16 Another option is the mini-cutdown, in which a standard intravenous catheter is used to directly cannulate the exposed vein. The catheter will not be as secure, but this technique may prove faster and easier, and it preserves the vein.

Venous cutdowns, while still taught as part of the ATLS protocol, are rarely used. One disadvantage to the venous cutdown procedure is the time required. One study demonstrated an average of about 10 minutes to complete the procedure.27 Thus, other venous access attempts should be underway during the cutdown procedure. The procedure also may be dangerous in inexperienced hands. For these reasons, as well as the potential complications of venous cutdowns, some authors advocate for percutaneous central lines as the first choice for venous access if peripheral access is unsuccessful.28 However, if central venous access is unsuccessful, the cutdown may be an option.

Umbilical Vein Catheterization

In newborns, umbilical vein catheterization (UVC) may be the easiest and most accessible route for venous access in an emergency or trauma situation. The umbilical vein remains patent after birth for about 1 week to 1 month. Prior to inserting a UVC, purse string suture or a piece of umbilical tape should be placed at the base of the umbilical cord to provide hemostasis and to anchor the line (Figure 6). The cord should be cut with a scalpel about 1 cm from the skin, and the umbilical vessels identified. The umbilical vein usually lies at the 12 o'clock position, and can be distinguished from the two umbilical arteries by its thin wall and larger lumen. The catheter (3.5 French in preterm infants, 5 French in term infants) then is advanced gently through the lumen of the vein. It should be advanced only 1 to 2 cm beyond the point where good blood flow is obtained. This is only about 4 to 5 cm in a term infant. If the catheter is pushed further than this, it will either enter the ductus venosus and inferior vena cava, or enter a branch of the portal vein within the liver. In some situations, the catheter may be placed purposely in the inferior vena cava for central venous pressure monitoring. However, in a resuscitation situation, the catheter should be advanced only 4 to 5 cm total to avoid inadvertent placement into the portal venous system. If the catheter is placed in the portal vein, infusion of hyperosmolar fluids could lead to liver necrosis. Complications of UVCs include hemorrhage, infection, air embolism, catheter tip embolism, and vessel perforation.16

Figure 6. Umbilical Vein and Arteries, with Purse String Suture at the Base

Reprinted with permission from: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia: Saunders;2004;376.

Volume Resuscitation

The goal in pediatric trauma resuscitation is to improve tissue perfusion and hemodynamic stability as quickly as possible. Warmed isotonic crystalloid solution (lactated ringers or isotonic sodium chloride solution) should be administered in boluses of 20 mg/kg.10The estimated blood volume for children is 80mL/kg, so each bolus of 20mL/kg corresponds to 25% of the child's total blood volume.10 Infusion of packed red blood cells (type O-negative blood, assuming the blood type of the child is unknown) should be anticipated in a child that has received 40mL/kg prior to ED arrival or has evidence of decompensated shock, and blood should be requested from the laboratory at the start of the resuscitation. Following the administration of each fluid bolus, the child should have all cardiovascular parameters reassessed, including heart rate, pulses, perfusion and blood pressure. If the patient has persistent tachycardia, weak pulses and poor peripheral perfusion after three boluses, consider starting an infusion of packed red blood cells at 10 mL/kg. When a child requires blood transfusion close to his/her whole blood volume (75-80 mL/kg), replacement of clotting factors should be considered to avoid the coagulopathies associated with massive transfusions. These factors include fresh frozen plasma (FFP), platelets, and cryoprecipitate. Coagulopathy associated with massive transfusion is worsened by transfusing cold blood, therefore, all blood should be warmed prior to transfusion.

Special attention should be given to any signs and symptoms of disseminated intravascular coagulation (DIC) during the trauma resuscitation. Bleeding from sites of venipuncture, and the development of petechiae or ecchymoses, may be clues that DIC has developed. Laboratory values diagnostic of DIC include a prolonged prothrombin time (PT) and activated partial prothrombin time (aPTT), decreased fibrinogen level and platelet count, increased fibrin degradation products, and an elevated D-dimer. If bleeding is present and DIC is suspected, administration of FFP, cryoprecipitate, and platelets may be warranted. The definitive treatment for DIC is treatment of the underlying condition. The pediatric doses for blood products are listed in Table 4.

Table 4. Blood Products and Pediatric Doses

During the early resuscitation phase, an essential consideration is temperature regulation. In comparison with adults, children have a higher body-surface-area-to-volume ratio, leading to greater insensible heat and fluid losses, which can worsen the hypovolemic state. The resuscitation room should remain heated, with overhead and bed warmers utilized as needed. Fluids also should be warmed to prevent core cooling.11

Once resuscitative efforts have begun, certain parameters should be checked frequently to evaluate whether efforts are having a positive effect on organ perfusion and hemodynamic stability. These indicators include slowing of the heart rate, increased pulse pressure to greater than 20 mmHg, return of normal skin color, increased warmth of extremities, improvement in mental status and Glascow Coma Scale score, systolic blood pressure increased to greater than 80 mmHg, and improved urine output (2 mL/kg/hr in infants, 1 mL/kg/hr in adolescents).11 Following the trend of vital signs provides important insight into the adequacy of resuscitation efforts. For example, increasing heart rate with narrowing of pulse pressure may indicate a clinical progression to shock, even if the numbers are still within the "normal" range.

Diagnostic Studies During the Resuscitation

Resuscitation of any trauma patient also includes diagnostic studies to aid in management and treatment. As in adult patients, pediatric trauma victims, in many trauma centers, have routine initial laboratory tests performed during the trauma resuscitation, including complete blood count, chemistry panels, and coagulation studies, as well as type and cross match. However, studies have found that routinely obtaining these laboratory data is often of limited utility in the initial management of an acutely injured pediatric patient.29 Most suggest that laboratory testing be specifically directed to data that will be useful for the individual child's resuscitation. One important exception is the child with an acute head injury. Hyperglycemia and coagulopathy are often associated with intracranial injuries and may require intervention during initial management. If the initial assessment of the patient suggests brain injury, then routine lab testing may be useful.29

Measurement of the base deficit serves as an estimation of tissue acidosis due to inadequate tissue perfusion, and thus acts as an indicator for the degree of shock. Base deficit is used extensively in adult trauma patients as a prognostic indicator. Two studies of pediatric trauma patients demonstrated that the base deficit may be a useful measure during resuscitation in this population as well.30,31 Because shock can be more difficult to recognize in children due to the anatomic and physiologic differences previously discussed, following the base deficit may be useful in guiding patient management. While existing studies vary on the exact number, most conclude that a base deficit greater than -5 to -8 is a sign of significant shock and predictor of poor outcome.

Imaging studies remain an important part of the resuscitation of any trauma patient. In adult patients, bedside ultrasound and focused abdominal sonography for trauma (FAST) examination are widely used during trauma resuscitation. The FAST exam comprises four views to evaluate for free fluid in the right and left upper quadrants, the pelvic retrovesicular/retrouterine space, and around the heart. (See Table 5.)

Table 5. FAST Exam

The FAST exam is useful in many respects. The exam is non-invasive and does not require sedation, saves the patient from radiation exposure, and allows for direct supervision of the patient during the exam. Because shock in pediatric trauma patients can be difficult to assess, the FAST exam may help identify free peritoneal fluid or pericardial fluid quickly. In theory, children are easier to examine due to their smaller size, less body fat, and thinner abdominal walls. However, solid organ injuries to the liver and spleen are common in children, and may be missed if there is no intraperitoneal bleeding. Up to 31%-37% of solid organ injuries produce no free fluid in children.32 The clinical significance of this is uncertain, as children are managed nonoperatively in the majority of solid organ injuries.33

Studies have shown that the sensitivity and specificity of the FAST exam in children are slightly less than in adults (sensitivity 83%-87% for adults versus 71%-91% for children; specificity 97%-100% in adults versus 84%-100% in children).34-38 Based on these numbers, the utility of ultrasound in pediatric trauma patients has been debated. In a study describing pediatric emergency physicians' perception of ultrasound in the trauma patient, there was a marked drop in usage and perceived utility in the pediatric population.31 This may be explained in part by the fact that the surgical management of children with solid organ injury differs from adults. Most hemodynamically stable pediatric patients are treated non-operatively even if free fluid is noted on imaging, thus casting doubt on the added benefit of the FAST exam in stable patients. However, most authors agree that the FAST exam is useful in hypotensive patients because it allows for quick diagnostic evaluation at the bedside, and can aid trauma surgeons in further management. The FAST exam has been incorporated into ATLS guidelines.

Diagnostic peritoneal lavage (DPL) was formerly the gold standard for rapid identification of significant intra-abdominal injury in all trauma patients, including children. With the growing ease and popularity of ultrasound, however, DPL is performed less frequently in current practice. DPL has several disadvantages compared with ultrasound. These include DPL being an invasive procedure, as well as providing nonspecific results (i.e., DPL does not identify the injured organ or establish the severity of the injury.) In addition, DPL has been shown to be overly sensitive in cases of pediatric abdominal trauma. One study showed that a positive DPL (Table 6) was associated with a negative laparotomy rate as high as 85%.39 Given these considerations, DPL is useful only in select situations. For example, in a child with a severe head injury requiring an emergency neurosurgical procedure, the trauma surgeon may elect to proceed with DPL — concurrent with craniotomy — to determine if emergency laparotomy is warranted for significant intra-abdominal injury.33

The DPL technique for a child does not differ significantly from that of an adult patient. However, since a child's abdominal wall is much thinner, care must be taken to advance slowly and avoid iatrogenic injury to intra-abdominal organs. The closed technique is faster and easier than an open DPL, but does carry a higher risk of bowel perforation, and is more frequently associated with inadequate fluid return. The open technique is used most often for patients who have had prior surgical procedures to avoid bowel injury, but does carry the risk of incisional hernia in the future if the fascia is not properly closed.14

Prior to starting DPL, a nasogastric tube and urinary catheter should be placed to decompress the stomach and bladder. When performing the closed technique, the first step is to make a 2 to 3 mm incision in the midline just below the umbilicus. Then, an 18-gauge needle is inserted perpendicular to the abdominal wall of the supine child. Once the needle meets resistance from the fascia, it should be directed toward the pelvis and stabbed through the posterior fascia and peritoneum. Then, a J-wire is passed through the needle into the peritoneal cavity. The needle is removed over the wire, and the catheter is passed into the cavity. Next, aspiration of fluid and/or blood is attempted using a syringe. If the aspirate is negative for gross blood, then 15 mL/kg of warmed normal saline should be instilled and drained, and the lavage fluid sent for red cell count and microscopic evaluation (Table 6).

If the open technique is used, then an incision is made through the posterior fascia, clips are used to elevate the fascia, and a trocar is used to enter the peritoneal cavity. If a midline approach is contraindicated due to prior surgery, then the incision is placed in the left lower quadrant. The infraumbilical approach also is contraindicated if the patient has sustained a pelvic fracture, which increases the chance of a false-positive DPL result. In this case, a supraumbilical approach is indicated.14

The interpretation of fluid obtained by DPL is the same in children as for adults, and is listed in Table 6. Given the high false-positive rate in a child, however, the presence of blood in the peritoneum does not necessarily mandate a laparotomy in a child.

Once the child is hemodynamically stable, computerized tomography (CT) should be considered if intra-abdominal injury is a possibility. However, since CT imaging requires the child to be moved away from the resuscitation area and may require sedation, this should only be performed once hemodynamic stability has been achieved. The abdominal CT study is probably most useful in evaluation of solid organ injuries; it may provide important information about hollow viscous injury as well. The use of oral contrast in addition to intravenous contrast has been controversial. Some authors suggest that oral contrast helps to delineate pancreatic and intestinal injuries,33,39 whereas other studies refute this claim.40 Ultimately, the decision to add oral contrast may depend on the institution. CT may be particularly useful in helping to guide nonoperative management of injuries because it provides information on the grading of solid organ injuries. However, not every child with a normal abdominal examination following a car accident requires a CT study. The radiation exposure from CT imaging does increase a child's risk of developing cancer in the future. Thus, the need for a CT study must be carefully considered. If a child is too hemodynamically unstable to allow CT imaging, an emergent laparotomy may be needed to identify injury and control bleeding.

Management of Injuries

Because children are smaller than adults, a given force applied at impact is transmitted throughout a relatively larger area of the abdomen, making multi-organ injury more likely. In addition, children have thinner abdominal walls and a more compliant thoracic rib cage, leaving the spleen and liver exposed and more vulnerable to injury.33 The spleen is the most commonly injured intra-abdominal organ due to blunt trauma, and clinicians should maintain a high index of suspicion in the proper clinical scenario. Nonoperative management of splenic injuries has become the standard of care in pediatric patients because it avoids the complications of post-splenectomy infections. Most children are treated with observation and partial splenectomy or splenorrhaphy if laparotomy is required. The only true indication for total splenectomy is hemodynamic instability and irreparable damage to the spleen. Studies have shown that nonoperative management of splenic injuries results in full recovery in 90%-98% of cases.33

Hepatic injuries are the second most common intra-abdominal injury. As with splenic injuries, CT imaging and nonoperative management are recommended, unless hemodynamic instability requires exploratory laparotomy and repair. Other injuries, such as intestinal or pancreatic injuries, are less common and more difficult to diagnose in children. Oral contrast during imaging may be helpful in identifying these injuries, but maintaining vigilance and a high clinical suspicion is essential.33

Non-hypovolemic Shock

The most common type of shock resulting from trauma, in any patient, is hypovolemic shock due to hemorrhage. Most trauma patients have some degree of hypovolemic shock and should be fluid resuscitated. However, if a patient does not respond quickly to fluids, other types of shock must be considered.

Neurogenic shock in trauma patients is caused by loss of sympathetic tone due to spinal cord injury. In the absence of sympathetic innervation, neither tachycardia nor peripheral vasoconstriction occurs in response to the hypotension. This results in the classic presentation of neurogenic shock: hypotension and bradycardia. This is in contrast to Cushing's triad, which reflects increased intracranial pressure and is manifested by hypertension and bradycardia. If neurogenic shock is suspected, treatment should continue with aggressive fluid resuscitation and pharmacologic support, with vasopressor and/or atropine administration, as needed to stabilize the patient.

Cardiogenic shock also may occur after trauma, either from direct myocardial injury, cardiac tamponade, or tension pneumothorax. Appropriate treatment with a needle in the pericardium for tamponade, or the pleural space for tension pneumothorax, should improve hemodynamics.

Advances in Treatment/Therapy

Massive Transfusion. Massive transfusion is defined as the replacement of more than one blood volume in a 6-hour period. The risks of massive transfusion include citrate toxicity, electrolyte and acid-base abnormalities, hypothermia, and coagulopathy. In pediatric patients, citrate toxicity is the most serious concern with massive transfusion. Citrate binds divalent cations and thus causes hypocalcemia and hypomagnesemia. Patients should be monitored for signs of hypocalcemia, such as a prolonged QT interval, and treated symptomatically with intravenous calcium chloride (10-20 mg/kg). Other electrolyte disturbances include hyper- or hypokalemia. Hyperkalemia is caused by the leakage of potassium from stored red blood cells. Hypokalemia is more common and results from the metabolism of citrate to bicarbonate, causing alkalosis and an intracellular shift of potassium ions.14 In any patient undergoing massive transfusion, electrolyte levels should be rechecked regularly to identify abnormalities.

The coagulopathy caused by massive transfusion is usually attributed to thrombocytopenia. Controversy exists about the utility of prophylactic platelet transfusion, and no consistent recommendations exist regarding platelet infusion during massive transfusion.14, 41 Coagulopathy also is due to hypothermia, therefore any blood transfused must be warmed.

At our institution, a "Massive Transfusion Guideline" (MTG) exists, whereby any patient who meets massive transfusion criteria is quickly identified and the transfusion service and clinical laboratory is contacted immediately to expedite product preparation and blood testing. For the pediatric patient, the initial MTG "pack" includes four units of packed red blood cells, two units of FFP, and one pheresis pack of platelets. The actual administration of the products is based on initial laboratory values. If the INR is less than 1.5, platelets are given. Also, if the platelet count is less than 25,000, platelets are infused to increase the platelet count by 25,000 to 50,000.42 If there is continued bleeding and hemodynamic instability despite ongoing transfusion, the initial MTG pack is repeated. After two rounds of the MTG pack, the use of recombinant factor VII is considered. The use of such a protocol is postulated to improve survival by involving necessary personnel early and expediting testing and treatment.

Activated Recombinant Factor VII (rFVIIa). Although originally designed for the treatment of hemophilia patients with factor VIII or IX inhibitors, recombinant factor VII (rFVIIa) has been increasingly used for nonhemophilia patients with bleeding. rFVIIa is a unique clotting factor substitute that has been found to enhance thrombin formation on activated platelets. Thus, rFVIIa is thought to provide hemostasis in situations where profuse bleeding leads to impaired thrombin generation.43 rFVIIa has a rapid onset of action (about 10 minutes) and carries a low risk of thrombogenicity in patients who continue to bleed profusely. In addition, the low volume required allows for rapid administration without risk of fluid overload. Also, administration of this factor requires minimal preparation time and does not require thawing. To date, there are no reports of anaphylactic reactions, nor are there concerns about the transmission of infectious diseases because it is a recombinant product. Case reports have described success in patients with impaired liver function, and in trauma patients with bleeding. The research on nonhemophilia use of rFVIIa, especially in pediatrics, is limited. While case reports have shown promising results with rFVIIa in adult trauma victims, no controlled trials dedicated to pediatric trauma patients have been published.44

Because most of the research has been done in adult populations, the exact dosing for pediatric patients is yet to be established. The effective dose in adults is 90 g/kg, repeated every two hours. Some research has shown that clearance of rFVIIa in children is faster, requiring larger and more frequent doses in these patients to achieve equivalent plasma levels.44,45

The disadvantages of rFVIIa include a short half-life in children (about two hours) and the high cost of the product. The data on nonhemophilia use are limited, as are data concerning safety and optimal dosing. There is a theoretical risk of thromboembolic complications that has been described in the adult literature, although these complications occurred in patients with other predisposing risk factors, including cardiovascular disease and advanced age.44 In addition, there is no laboratory test to monitor the efficacy of the product to date. In general, rFVIIa should be considered only after other hemostatic products or other conventional therapy has been unsuccessful.

Hypertonic Saline in Severe Traumatic Brain Injury. Despite advances in pediatric trauma care, outcomes in severe traumatic brain injury have not improved. Early hypotension (within 24 hours of hospitalization) in head trauma patients is associated with poor neurologic outcome and longer hospital stays. This has been attributed to a disruption of normal cerebral autoregulation following trauma, leading to central hypotension and cerebral hypoperfusion, ischemia, and decreased cerebral perfusion pressure.46 Therefore, in any trauma patient in whom severe head injury is suspected, initial resuscitation should be aggressive and aimed at normalizing blood pressure and optimizing oxygen delivery.

Other therapies that may improve outcome in a patient with a traumatic brain injury include the use of hyperosmolar agents, such as mannitol or hypertonic saline. However, the efficacy of these therapies still relies on the maintenance of central blood pressure, and none should be considered until the patient is euvolemic.47 Hyperosmolar solutions decrease intracranial pressure (ICP) and cerebral edema by causing plasma expansion, leading to a lower hematocrit, reduced blood viscosity, and decreased cerebral blood volume. The resulting osmotic gradient draws fluid out of the brain tissue and decreases cerebral edema.48 Mannitol has been the traditional hyperosmolar agent used to reduce ICP. Recently, however, hypertonic saline has been gaining popularity as an adjunct in managing increased ICP in adult and pediatric head-injured patients.

The most commonly used concentration is 3% hypertonic saline, dosed from 0.1 to 1 mL/kg/hr. These solutions should be administered through a central line because of the extreme hypertonicity. Hypertonic saline has been shown to be effective in patients who have increased ICP that is unresponsive to mannitol. Unlike mannitol, hypertonic saline acts as a volume expander and appears to carry less risk of renal failure. Pediatric guidelines for the use of hyperosmolar therapy suggest that a serum osmolarity of 360 mOsm/L may be tolerated in these patients.48,49 Hypertonic saline effectively dehydrates cerebrovascular endothelial cells and erythrocytes, which reduces secondary ischemic injury because the smaller erythrocytes are able to deform more easily within capillaries, thereby, optimizing oxygen delivery. Hypertonic saline also may decrease the inflammatory response, thus reducing secondary injury to the brain.

One potential complication of hypertonic saline includes rebound elevation of ICP due to accumulation of sodium in the extracellular space. Central pontine myelinosis is another risk that is associated with rapid correction of hyponatremia with hypertonic solutions. This complication has not been observed in patients whose initial sodium concentrations were within normal limits. The use of hypertonic saline also may cause hematologic abnormalities, including bleeding, hypokalemia, and hyperchloremic acidosis. Electrolyte levels must be followed closely to prevent these complications.48,50

Summary

The recognition and prompt treatment of shock in pediatric trauma patients first requires an understanding of important anatomic and physiologic differences between adults and children. Children may present with more subtle signs of shock, such as agitation or tachycardia, long before becoming hypotensive. A color-coded, length-based tape measure, such as the Broselow tape, is essential in helping clinicians easily identify optimal equipment sizes and provide accurate medication doses. Venous access can be challenging in children, especially those in shock, and clinicians should be familiar with intraosseous catheters, central venous lines, and peripheral cutdown maneuvers. Diagnosis and appropriate disposition may require specific imaging or diagnostic techniques, and physicians must understand the utility and limitations to diagnostic testing in the pediatric trauma patient.

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What is the percent of blood loss in a patient with Class II hemorrhage?

What is the percentage of blood loss?

What happen if a person losses 40% of the total blood volume?

What are the 2 types of hypovolemic shock?