Shock

Holly Caretta-Weyer, MD and Jamie Hess, MD

University of Wisconsin School of Medicine and Public Health

Objectives

Upon completion of this self-study module, you should be able to:

• Describe the signs and symptoms of shock.
• List the different types of shock and how to differentiate each type.
• Discuss the initial management of shock.
  

Introduction

What exactly is shock? Shock is a term used to describe inadequate oxygen delivery to the tissues that cannot keep up with metabolic demand. This creates a state of hypoperfusion. It may be uncompensated, meaning there is hypotension and inability to maintain normal perfusion, or it may be compensated, meaning that blood pressure and perfusion are maintained for the time being.

There are several different types of shock (below) and shock is often thought of as being “warm” or “cold.” This can be useful in helping to differentiate the type of shock, but there are several other factors that need to be considered when defining the type of shock and there are often mixed pictures so take the “warm” and “cold” shock differentiation with a grain of salt.

Initial Actions Primary Survey

ABC’s are the critical first step in a patient with shock! The adage “IV, O2, monitor” is also a good thing to be thinking up front in a child presenting with what appears to be shock. Place the child on the monitor, pulse ox, and obtain blood pressure. Start supplemental oxygen and consider early intubation if the child will require ventilatory assistance, significant help with oxygenation, or airway protection. Obtain IV access – if you cannot after two attempts, an intraosseous line is appropriate as access is paramount in shock states.

Once you have managed the airway and breathing, circulation becomes key in shock. First, you must identify the type of shock, which may not always be easy in mixed shock states (see Differential Diagnosis). Once you have identified the type of shock and initiated measures for resuscitation such as managing the airway and obtaining vascular access, it is time to begin the true resuscitation.

The key component of resuscitation in patients presenting in shock is fluid administration. In most cases of decompensated distributive or hypovolemic shock, the most important first step is to give a 20 cc/kg bolus of IV crystalloid (normal saline or lactated ringers). This may be repeated twice up to a total fluid administration of 60 cc/kg. If the child remains in shock, this is considered refractory shock and it would then be prudent to consider adding vasopressor support, often in the form of norepinephrine or dopamine. If a child has risk factors for adrenal insufficiency, one should also consider administering stress-dose steroids as adrenal insufficiency can also lead to a refractory shock state.  If the child is suffering from hemorrhagic shock, blood should be administered after the initial crystalloid bolus and the site of hemorrhage should be managed appropriately.

Cardiogenic shock is a special type of shock in which there is failure of the pump due to malformation, overload, obstruction, or non-perfusing rhythm. Fluid may still be given in this instance but at a lower bolus (5-10 cc/kg) and over a longer period of time (up to 20 minutes) to prevent exacerbation of the failure state and worsening pulmonary edema.  You should closely monitor fluid and respiratory status during fluid administration in this instance. If you are suspicious for a ductal-dependent cardiac lesion or anomaly, which can cause an obstructive shock picture with cardiogenic shock, you should also consider administering prostaglandin in this instance to open the ductus arteriosus which can ease the amount of vascular congestion and fluid backing up into the lungs. You should also certainly at this point be in contact with a pediatric cardiologist and/or pediatric cardiothoracic surgeon and begin discussions about definitive management for this child.

Goals for Resuscitation should include:

• Blood pressure (systolic pressure at least fifth percentile for age: 60 mmHg <1 month of age, 70 mmHg + [2 x age in years] in children 1 month to 10 years of age, 90 mmHg in children 10 years of age or older)
• Quality of central and peripheral pulses (strong, distal pulses equal to central pulses)
• Skin perfusion (warm, with capillary refill <2 seconds)
• Mental status (normal mental status)
• Urine output (≥1 mL/kg per hour, once effective circulating volume is restored)
• Clearance of lactate (hope to see down trending and preferably cut in half after initial resuscitation)

Early Goal-Directed Therapy

Children in shock are critically ill and every moment counts in these situations. Thus, a significant amount of research has been done to this end and has resulted in goals of care referred to as “Early Goal-Directed Therapy.”

The basic focus of this algorithm involves the following:

• Initial management should focus on fluid resuscitation with isotonic crystalloid and specific pharmacologic therapies as indicated by the etiology/type of shock.
• Interventions should be administered in rapid sequence, with evaluation of physiologic indicators (as above) before and after each intervention.
• Once physiologic goals have been achieved and perfusion improved, the patient should continue to receive supportive treatment and careful monitoring. 
  

Differential Diagnosis

Hypovolemic Shock

This is the most common cause of shock worldwide in infants, most often secondary to diarrhea. Other examples of hypovolemic shock include blood loss, vomiting, heat stroke, or burns. It is important to realize the stages of shock, especially in children who can compensate for a larger percentage of losses than adults and then rapidly decompensate. Below is a chart that describes the stages of hypovolemic (traditionally thought about with hemorrhagic) shock and the physical exam findings and vital signs associated with each stage. Systemic vascular resistance is increased with initially stable to possibly decreased cardiac output at later stages. The extremities become cool, making this an example of “cold shock.”

Distributive Shock

Distributive shock often results from vasodilation and a decrease in systemic vascular resistance. It is associated with normal to increased cardiac output. Given the vasodilation, the extremities are warm, making this an example of “warm shock.”

Causes of distributive shock include:

• Sepsis
  • Most common etiology in children
  • Infection causes significant vasodilation
  • Think about in a child with fever and other signs of infection
• Anaphylaxis
  • Causes profound vasodilation secondary to an IgE-mediated immediate hypersensitivity reaction
  • Think about in a child with wheezing, urticaria, angioedema, or stridor
• Neurogenic
  • Spinal cord injury resulting in loss of sympathetic tone
  • This results in vasodilation as well as bradycardia
  • Think about in trauma patients with neurological deficits and paradoxical bradycardia in the setting of hypotension

Cardiogenic Shock

Cardiogenic shock results from pump failure and depressed cardiac output. This decreased cardiac output results in cool extremities, another example of “cold shock.”

The most common causes of cardiogenic shock in children are as follows:

• Structural Disorders – often present a picture of obstructive shock
  • Hypoplastic left heart syndrome, tetralogy of Fallot, coarctation of the aorta and other structural disorders can result in systolic heart failure
  • Some of these disorders are ductal dependent, meaning they will only manifest after closure of the while others are ductal independent and will present within the first day or two of life
  • Think about in children with hepatomegaly, signs of pulmonary edema, JVD, or murmur
• Cardiomyopathies
  • Infections such as myocarditis, familial causes such as hypertrophic obstructive cardiomyopathy, and infiltrative causes such as hemochromatosis can cause myocardial dysfunction and failure
  • Think about in children with recent infection, murmur, chest pain, or signs of heart failure
• Arrhythmias
  • Prolonged SVT or ventricular dysrhythmias can cause substantial decrease in stroke volume and thus cardiac output, also leading to failure.
    

Disposition

Most patients who present with shock will require admission to a pediatric ICU for close monitoring, frequent reassessment, and further management.  Early consultation with an intensivist is recommended and you may need to contact other specialists including surgeons in the case of trauma or cardiac defect.

Pearls and Pitfalls

In shock, don’t forget about the glucose! Pediatric patients are often hypoglycemic when critically ill and may require glucose supplementation.
Also remember the rule of 50s when dosing glucose in pediatric patients:

• 1 mg/kg of D50 (1×50=50)
• 2 mg/kg of D25 (2×25=50)
• 5 mg/kg of D10 (5×10=50)

Other pitfalls to be aware of in managing shock:

• It is often difficult to recognize – some shock is obvious, other times it is very subtle (compensated shock). Pay close attention to physical exam findings and vital signs as well as careful history taking.
• Inadequate monitoring of response to treatment – make sure you fully resuscitate the patient to the parameters outlined above but be careful not to under-fluid resuscitate those who are hypovolemic and not to over-fluid resuscitate those in cardiogenic shock. This is why identifying the type of shock is important!
• Always consider causes for lack of improvement such as other causes of shock or other contributing factors (adrenal insufficiency) in children who continue to do poorly despite your initial resuscitation.
  

References

1. Bell LM. Shock. In: Textbook of Pediatric Emergency Medicine, 6th, Fleisher GR, Ludwig S, Henretig FM, Lippincott Williams & Wilkins, Philadelphia 2010. p.46.
2. Carcillo JA, Davis AL, Zaritsky A. Role of early fluid resuscitation in pediatric septic shock. JAMA 1991; 266:1242.
3. Carcillo JA, Fields AI, American College of Critical Care Medicine Task Force Committee Members. Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock. Critical Care Medicine 2002; 30:1365.
4. Recognition of shock. In: Pediatric Advanced Life Support Provider Manual, Chameides L, Samson RA, Schexnayder SM, Hazinski MF, American Heart Association, 2011. p.69.
5. Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. New England Journal of Medicine 2001; 345:1368.
6. Stoner MJ, Goodman DG, Cohen DM, et al. Rapid fluid resuscitation in pediatrics: testing the American College of Critical Care Medicine guideline. Annals of Emergency Medicine 2007; 50:601.
7. Witte MK, Hill JH, Blumer JL. Shock in the pediatric patient. Advanced Pediatrics 1987; 34:139.