Case Study

Cardiogenic shock

by Heidi E. Karpen, MD

Case presentation

Case presentation This 3292-gram female infant was born at 36 6/7 weeks’ gestation by spontaneous vaginal delivery to a 27-year-old gravida II, para I mother. Prenatal care started at 8 weeks and the pregnancy was complicated by diet-controlled gestational diabetes. At delivery, the maternal lab values were blood type O+, rubella immune, RPR NR, HBsAg negative, HIV negative, GBS positive. The mother received two doses of intrapartum antibiotics. The baby’s Apgar scores were 8, 9 at one and five minutes; she appeared well following birth and was allowed to room-in with the mother.

On the 2nd day of life, the baby was cyanotic during feeding. Pulse oximetry demonstrated oxygen saturation in room air of 74%. She also had moderate tachypnea with mild subcostal retractions. The infant initially was given oxygen by hood without improvement in pulse oximeter values. A full evaluation for bacterial septicemia, including blood and CSF analysis and culture, was undertaken and antibiotics were started. Because of continued hypoxemia, first nasal CPAP was instituted, then mechanical ventilatory support, again with marginal improvement in oxygen saturation. Physical examination now revealed a lethargic, grey, infant with markedly poor capillary refill. Prostaglandin E1 (PGE1) was begun presumptively for the suspicion of congenital heart disease, and oxygen saturations improved. Vital signs showed an HR ranging between 150 and 165 bpm, BP 62/33 mm Hg, RR 65 bpm, and O2 saturation of 93% to 94%.

The infant was transported to Texas Children’s Hospital for further evaluation and treatment. Upon arrival, an arterial blood gas demonstrated a marked metabolic acidosis. Cardiac ultrasonagraphy demonstrated hypoplastic left heart syndrome with mitral and aortic valve atresia, a hypoplastic aortic arch, a non-restrictive atrial septal defect, a moderate PDA, and dilation of the right ventricle with poor contractility. Blood chemistries showed evidence of end-organ ischemia, and the infant subsequently developed moderate renal and hepatic failure. The baby was treated medically until surgical intervention (ie, Norwood procedure) could be safely undertaken.

Denouement

The differential diagnosis of a term infant who initially appears well but deteriorates in the first few days of life includes bacterial or viral infection, idiopathic persistent pulmonary hypertension, inborn errors of metabolism, and ductal dependent congenital heart disease. A careful review of the prenatal birth history, physical examination, and selected laboratory data may help distinguish among these entities. This baby had a fairly unremarkable prenatal course until becoming ill. Marked metabolic acidosis was identified on an arterial blood sample: pH 7.20, pCO2 25 torr, pO2 60 torr with a calculated base deficit of –17. Arterial lactate value was 14 mmol/L. Tachypnea, acidosis, and high lactate values are associated with a variety of inborn metabolic errors and septicemia; they also are associated with profound cardiogenic shock caused by ductal dependent congenital heart disease. Serum pyruvate and ammonia levels help differentiate between these entities.

Unfortunately, findings on physical examination often are nonspecific. While infants with ductal dependent congenital heart disease frequently have systolic murmurs associated with tricuspid valve regurgitation and/or a closing ductus arteriosus plus diminished pulse pressures and prolonged capillary refill, similar findings may be present with other conditions. Presence of hepatosplenomegaly also is variable. In addition to ventilator support, evaluation for inborn errors of metabolism (eg, ammonia level) and administration of antibiotics, an empiric trial of PGE1 and referral to a NICU with cardiology and cardiovascular surgery capabilities may be indicated in a newborn infant who presents with acute cardiovascular collapse shortly after birth.