Shock and Hypotension in the Newborn Treatment & Management

In relatively recent years, there has been a movement away from defining hypotension in the newborn purely based on blood pressure lower than the infant's gestational age. ^{[4, 18, 19]} Rather, infants with hemodynamic instability require an individualized approach, in which the underlying pathophysiologic mechanisms should be stratified and management is adapted for appropriate intervention. ^{[4, 18, 20]}

Once shock is suspected in a newborn, appropriate supportive measures must be instituted as soon as possible. ^[3] These include securing the airway and assuring its patency, providing supplemental oxygen and positive-pressure ventilation, achieving intravascular or intraosseous access, and infusing 10 mL/kg of colloid or crystalloid solution (to repeat the same volume if needed). Use of crystalloid or colloid solutions is appropriate unless the source of hypovolemia is hemorrhage, in which case whole or reconstituted blood is more appropriate.

During the process of shock, production of chemical mediators may initiate disseminated intravascular coagulopathy (DIC), which requires careful monitoring of coagulation profiles and management with fresh frozen plasma, platelets, and/or cryoprecipitate.

Varying degrees of renal, myocardial, gastrointestinal (GI), hepatic, and brain damage may occur during shock as elaborated in Complications.

Surgical care

Structural heart disease and arrhythmias often require specific pharmacologic or surgical therapy. The liver and bowel may be damaged by shock, leading to GI bleeding and increasing the risk for necrotizing enterocolitis, particularly in the premature infant.

Diet

Infants in shock should not be fed via the oral route, and feedings should not be resumed until GI function has recovered. Initiate total parenteral nutrition as soon as possible.

Consultations

Depending on the type of shock, potential consultants include the following pediatric subspecialists: neonatologist, cardiologist, nephrologist, surgeon, infectious disease specialist, and hematologist.

Transfer

If deemed safe, infants presenting with evidence of shock should be transferred immediately to a full-service neonatal intensive care unit with adequate support, personnel, and expertise.

Monitoring

Infants recovering from neonatal shock are at risk of multiple sequelae and should be intensively screened for neurodevelopmental abnormalities using brain imaging and brainstem audiometric evoked responses. Other tests are determined by the individual infant's clinical course and complications.

Outpatient care should include neurodevelopmental follow-up and assessment, as indicated by the neonatal course.

The key to successful resuscitation is early recognition and controlled volume expansion with the appropriate fluid. The estimated blood volume of a newborn is 80-85 mL/kg of body weight. Clinical signs of hypovolemic shock depend on the degree of intravascular volume depletion, which is estimated to be 25% in compensated shock, 25-40% in uncompensated shock, and more than 40% in irreversible shock.

If blood loss is confirmed, initial resuscitation with 20 mL/kg of volume expansion should replace a quarter of the blood volume. Blood transfusion is preferred, but in an emergency, colloids or crystalloids can be used. If circulatory insufficiency persists, this dose can be repeated.

Once the first 10 mL/kg of blood volume is replaced, a decision to provide any further volume expansion should prompt the clinician to ascertain the cause of the hypotension and to evaluate the circulatory status. Information regarding central venous pressure (CVP) values in stable, ventilated newborns is limited; therefore, interpretation of readings in ill neonates is challenging. Its role in the management of systemic hypotension is uncertain, but serial measurements through an appropriately placed umbilical venous or other central venous catheter may help to guide volume expansion in suspected hypovolemia. ^[21] In the absence of CVP, titration against clinical parameters should be completed. Frequent and careful monitoring of the infant's vital signs with frequently repeated assessments and reexamination is mandatory. The use of crystalloid or colloid solutions is appropriate, unless the source of hypovolemia is hemorrhage, in which case whole or reconstituted blood is more appropriate. Commonly used agents include the following:

• Isotonic sodium chloride solution: A low-cost, readily available alternative

• Albumin: Useful for plasma volume expansion and the maintenance of cardiac output

• Lactated Ringer solution

Each fluid is essentially isotonic and has equivalent volume-restorative properties. Although some differences between metabolic changes are observed with the administration of large quantities of either fluid, for practical purposes and in most situations, the differences are clinically irrelevant. Importantly, there is no demonstrable difference in hemodynamic effect, morbidity, or mortality with resuscitation.

Inotropic agents, with or without peripheral vasodilators, are warranted in most circumstances of cardiogenic shock. Structural heart disease or arrhythmia often requires specific pharmacologic or surgical therapy. Excessive volume expansion may be potentially harmful. Table 1 summarizes the appropriate use of inotropes, lusitropes, or vasopressors in this situation (see Pharmacologic Therapy).

Newborns, who have little cardiac reserve, often present with hypotension and a picture of cardiovascular collapse. These critically ill infants represent a diagnostic and therapeutic challenge, and sepsis must be presumed and treated as quickly as possible. Survival from septic shock depends on the maintenance of a hyperdynamic circulatory state. In the early phase, volume expansion with agents that are likely to remain within the intravascular space is needed, whereas inotropic agents, with or without peripheral vasodilators, may be indicated later.

In early-onset neonatal sepsis, combined aminoglycoside and expanded-spectrum penicillin antibiotic therapy are the empiric antimicrobials of choice until a specific infectious agent is identified. Cephalosporins and vancomycin are often the antibiotics of choice in late-onset sepsis. Howver, concerns have been raised about the routine use of cephalosporins. In the face of renal failure, which may accompany shock, serum levels of gentamicin and vancomycin should be closely monitored to minimize iatrogenic renal toxicity.

The selection of drug for medical management of shock depends on the underlying cause. Table 1, below, lists agents commonly used in the treatment of neonatal shock.

Table 1. Agents Used to Treat Neonatal Shock (Open Table in a new window)

In circumstances in which volume expansion and the administration of vasoactive and inotropic agents have been unsuccessful, glucocorticoids (eg, dexamethasone, hydrocortisone) have been shown to be effective. The findings that steroids rapidly upregulate cardiovascular adrenergic receptor expression and serve as hormone replacement therapy in cases of adrenal insufficiency explain their effectiveness in stabilizing the cardiovascular status and lowering the requirement for pressure support in the critically ill newborn with volume-resistant and pressure-resistant hypotension.