Clinical Practice Case 6

This child's appearance is very worrisome because she demonstrates a decreased response to her environment. Her history of chickenpox with these clinical changes suggests sepsis since the skin rash in children with chickenpox provides a portal for bacterial superinfection.

Once septic shock is considered, it is important to activate the appropriate emergency response system to obtain additional help in treating shock and stabilizing the child.

In the short term, this child appears to be breathing adequately, but oxygen should be administered in all children with shock to maximize oxygen delivery to the tissues. For any child with possible sepsis or septic shock, you should:

• complete your primary assessment
• direct appropriate help to place the child on a cardiac monitor and pulse oximeter
• establish vascular access
• administer rapid fluid bolus with isotonic crystalloid (eg, normal saline or lactated Ringer's)
• conduct clinical reassessment

While you complete your primary and secondary assessments, other providers can obtain appropriate laboratory studies, including a rapid bedside glucose test and blood cultures.

The child has significant tachycardia with adequate distal perfusion and an acceptable (low normal) systolic blood pressure on examination. These findings are consistent with compensated septic shock.

As soon as vascular access is established, administer a rapid fluid bolus with isotonic crystalloid (e.g, normal saline or lactated Ringer's) followed by clinical reassessment.

One of the characteristics of sepsis is a wide pulse pressure. (The pulse pressure is the difference between the systolic and diastolic blood pressures.

The advanced provider will remember that if the diastolic blood pressure is less than or equal to half of the systolic blood pressure, the pulse pressure is clearly increased or widened. This is a finding consistent with a reduced systemic vascular resistance. The most likely cause of this vasodilated state is sepsis.

The child is tachypneic without increased work of breathing. This is characteristic of shock with the increased respiratory rate representing a compensatory response to create a respiratory alkalosis to counteract the metabolic acidosis that characterizes shock.

In addition to sepsis, a wide pulse pressure is seen in children with spinal (neurogenic) and anaphylactic shock. A wide pulse pressure is also seen in children with significant anemia, such as the child with sickle cell anemia, and in children with high fever, especially when the temperature is coming down (i.e, when they are vasodilated as they attempt to eliminate heat).

In both situations, the vasodilation represents the need for low systemic vascular resistance to maintain a high cardiac output state. In sepsis, the vasodilation results from the effects of the inflammatory mediators. With anemia, the reduced oxygen-carrying capacity and oxygen content are compensated by a high cardiac output to maintain tissue oxygen delivery. Similarly, the increased metabolic demand produced by fever requires a high cardiac output to maintain adequate oxygen delivery.

Other less common clinical conditions that cause a vasodilated state occur in children with chronic or acute liver failure and thyrotoxicosis.

During the secondary assessment, you should look for evidence of cardiac dysfunction (listen for a gallop, assess the hepatic size, and look for venous distention in neck veins). Also look for evidence of purpura and petechia suggestive of disseminated intravascular coagulation or other coagulopathies that can complicate sepsis. During the focused history obtain any further information about the child (SAMPLE), including:

• the child's recent signs and symptoms
• if the child has any allergies to the antibiotics that you plan to administer
• if the child is receiving any medications
• if the child's past medical history is relevant to her current condition
• the time of the child's last meal in anticipation of the need for intubation
• additional details about this event or the most recent change in responsiveness.

A bedside glucose test is important because children with sepsis are at increased risk for hypoglycemia. Blood samples for other studies, 

such as electrolytes and blood counts (tertiary assessment), will provide additional information to help you determine the severity of shock and identify the etiology as well as identify complications resulting from shock or its cause.

Advanced providers will find it helpful to obtain an arterial or venous blood gas and measurement of serum lactate concentration. These results will help objectively determine the severity of shock. (These results are discussed further in the case presentation.) It is unlikely that arterial blood gases will be available in the physician's office, however.

The repeat assessment shows a slight improvement in the child's heart rate. Monitoring the change in heart rate is an important element of shock assessment. If the correct interventions are provided and are effective, the heart rate and systemic perfusion will improve.

The child remains quite tachypneic, and the pulse pressure is still wide with a fall in the systolic blood pressure. It is important to recognize that sepsis is a dynamic clinical state and that frequent reassessment and aggressive fluid resuscitation are commonly required. Therefore, this child requires another rapid fluid bolus with isotonic crystalloid (e.g, normal saline or lactated Ringer's) followed by clinical reassessment. If available, administer appropriate antibiotics.

In this patient staphylococcal sepsis is possible because the skin is the likely source for the infection. The advanced provider will know that vancomycin is appropriate in view of the increasing frequency of methicillin-resistant Staphylococcus aureus.

This child requires urgent transport as soon as possible to the nearest tertiary care centre with pediatric critical care capability.

Despite a total of 60 mL/kg administered in 3 fluid boluses in less than an hour, this child's systolic blood pressure indicates that she has a hypotensive shock that is fluid refractory.

Based on the PALS Management of Septic Shock Algorithm, she requires vasoactive drug support.

If possible, providers should establish a central venous line to safely administer a potent vasoconstrictor such as norepinephrine, high-dose dopamine, or vasopressin. If a central venous line cannot be established, a secure peripheral venous line or I0 line may be used. This requires a second access site because fluid boluses should not be given through the same site as the vasoactive drug infusion.

The child has vasodilated septic shock. Severe septic shock is a complex physiologic state with hypotension typically resulting from a combination of profound arterial and venous vasodilation combined with variable impairment of cardiac contractility and increased capillary permeability.

The veno-dilation results in pooling of blood in the venous circulation with a reduced venous return to the heart and therefore reduced cardiac output.

Impaired cardiac contractility may reduce the ejection fraction, contributing to a fall in cardiac output. Increased capillary permeability contributes to the relative hypovolemia despite fluid administration.

Sepsis is a form of distributive shock because it is characterized by a maldistribution of blood flow. There is often excessive blood flow to the skeletal muscle and inadequate blood flow to the intestines, liver, and kidney.

If the patient does not adequately respond to aggressive fluid resuscitation, you should administer vasoactive drugs. Potent vasoconstrictor agents may be helpful to maintain effective perfusion of the brain and heart and to reduce the excessive skeletal muscle flow and redirect blood flow to the splanchnic circulation.

If the child requires potent vasoactive agents, many experts now recommend the addition of a stress-dose of hydrocortisone.

Note that this is a small dose of steroids compared with the larger doses that were used in the treatment of sepsis in years past-typically only 2 mg/kg of hydrocortisone is given as a loading dose.

Some experts recommend obtaining a blood sample to determine cortisol concentration or performing an ACTH stimulation test before administration of hydrocortisone. Because many labs do not have a sufficiently rapid turnaround on cortisol concentrations, hydrocortisone may be started empirically.

The decision to intubate and place the child on mechanical ventilation requires that you weigh the need to maintain good oxygenation and ventilation and reduce the metabolic demand from the work of breathing against the potential detrimental effects of positive-pressure ventilation on intrathoracic pressure and potential reduction in venous return and cardiac output.

Moreover, sedative agents are typically needed to permit endotracheal intubation, but these agents may reduce the child's endogenous stress hormone response and result in sudden cardiovascular collapse. You may not realize how much the child depends on her intrinsic catecholamine response until a sedative agent is given.

Thus it is important that you provide adequate fluid resuscitation and, if possible, begin a vasopressor drug infusion (eg, norepinephrine, epinephrine, or dopamine) before intubation. Sedative agents should be titrated by giving small doses to achieve just the level of sedation required for intubation.

Although the peripheral venous administration is not ideal when the child has fluid-refractory shock, vasoactive drug support may be given through a peripheral venous catheter or I0 catheter. You should closely monitor the vascular infusion site to detect early signs of infiltration. You should infuse vasoactive medications through a central line when one is inserted.

As a detail for the advanced provider, when a central venous infusion site is established after beginning a peripheral venous vasoactive drug infusion, it is often preferable to start a second vasoactive infusion through the central line and then stop the peripheral infusion when additional drug effect is seen. If you simply switch the infusion tubing from the peripheral to a central line, the patient's blood pressure may rapidly fall because whenever a vasoactive infusion is added to an infusion catheter, it will take several minutes for the vasoactive infusion to infuse through the tubing to reach the patient.

Distributive shock is characterized by a maldistribution of blood flow due to inappropriate vasodilation. The latter is clinically characterized by a wide pulse pressure, as previously noted, and some evidence of organ ischemia.

In addition to sepsis, the distributive shock is seen in children with profound anemia, such as a child with new-onset leukemia, who may present with a hemoglobin as low as 3 g/dL or lower. In this case, even though the cardiac output is high, the low hemoglobin concentration reduces arterial oxygen content, so there is inadequate oxygen delivery to the tissues, leading to anaerobic metabolism and defining shock.

Distributive shock may also be seen in a child with spinal cord injury interrupting the sympathetic innervation to the vasculature, resulting in profound vasodilation and hypotension (also called "spinal shock").

Anaphylaxis may also produce histamine release that causes profound vasodilation and hypotension. The cardiac output in anaphylaxis is also compromised by an elevation of pulmonary vascular resistance, which may cause acute right heart strain and impaired delivery of blood from the right heart through the pulmonary circulation and to the left ventricle.