Neonatal decompensation before surgery in hypoplastic left heart syndrome: a case control study

Abstract

Objective: Prior to Norwood 1 surgery, neonates with hypoplastic left heart syndrome (HLHS) are at risk of decompensation from systemic underperfusion secondary to pulmonary overcirculation. We examined whether preoperative temporal profiles of physiological and laboratory variables differed between neonates who did and did not decompensate preoperatively.

Design: Case control study.

Setting: Paediatric Intensive Care Unit, 2002-2013.

Patients: Eighty-five neonates with HLHS, matched by birth weight and admission date.

Measurements: Decompensation was defined as the need for emergency intubation and ventilation due to clinically diagnosed impaired systemic oxygen delivery. The end point was time of decompensation (cases, n=33) or discharge for surgery (controls, n=52). Variable trajectories were modelled non-linearly using generalised estimating equations.

Results: Decompensation occurred on median (IQR) day 3 (2-4) of life in cases, with surgery occurring on day 4 (3-7) in controls. Oxygen saturation and blood pressure trajectories were identical between groups (p>0.2). Heart and respiratory rates increased with time overall, but significantly faster in cases than controls; by an average of 4.0 bpm/day versus 1.4 bpm/day (p=0.002) and 5.3 respirations/minute/day versus 1.5 respirations/minute/day, respectively, (p=0.003). Although metabolic blood gas components began to decline subtly 24 h before clinical decompensation, they remained in the normal range for much of this period.

Conclusions: Heart and respiratory rates, and metabolic acid base trajectories show subtle differences prior to decompensation in neonates with HLHS. These findings highlight the importance of evaluating rates of change rather than absolute values of physiological and laboratory variables.

Keywords: Cardiology; Intensive Care; Monitoring; Physiology.