Low-output is not the cause of death of neonatal piglets early after cardiopulmonary bypass.

The mortality rate of neonatal piglets after heart surgery is high. Searching for a possible explanation for the death of neonatal piglets early after cardiopulmonary bypass, we analyzed hemodynamic parameters regarding survival and non-survival. Initially, 10 neonatal piglets (younger than 7 days) were connected to cardiopulmonary bypass (CPB). The mean body weight was 2.98 ± 0.44 kg. Exposure of the heart was performed through a median sternotomy. After connection to the CPB, the piglets were cooled to 32°C core temperature before the ascending aorta was cross-clamped and the heart arrested (90 min). Thereafter, piglets were re-warmed to 37°C and separated from CPB. During follow-up, the piglets did not receive inotropic support or vasopressors. Piglets who survived at least 2 h after termination of CPB were included in the study for further data analysis (n = 9). Five piglets died 2.5 to 4.0 h (median: 3.5 h) after CPB; these piglets formed the non-survivors group. Four animals survived the complete follow-up of 6 h after CPB and formed the survivors group. Regarding contractility (dP/dt(max) , dP/dt(max) /P, and wall thickening) there were not statistically significant differences between the groups. Non-survivors showed prolonged decrease of mean arterial pressure of more than 20% of baseline values, corresponding with a value of below 30 mm Hg. In conclusion, the death of neonatal piglets early after cardiopulmonary bypass was not determined by low output.