Safety of heart-lung machines during prolonged standby

Coronary artery bypass surgery is increasingly performed without an extra-corporeal circuit. A heart-lung machine (HLM) is kept on standby for safety reasons, but rarely used. The tubes of the machines are currently discarded after every operation. Costs and waste would be avoided if HLMs could stay on standby for longer periods of time. We therefore investigated the sterility of intra-tube fluid over time.

Four machines were tested. The tube system was fixed and filled with priming solution. Samples of intra-tube fluid and fluid from the fluid bags were taken after 0, 12, 24, 36, 48 and 72 h. Microbiological cultures were performed by direct inoculation and membrane filtration and incubated up to 14 days. Endotoxin levels were also determined.

Bacteria were grown from two samples only and were considered as contaminants. Endotoxin concentrations never exceeded acceptable levels.

To keep HLMs on standby for 72 h is probably safe. The prolonged use of HLMs will contribute to cost and waste reduction in open heart surgery.