The effects of low flow, low pressure pulsatile bypass
Belcher, P.; Lennox, S.C.
Journal of Cardiovascular Surgery 26(3): 223-227
1985
ISSN/ISBN: 0021-9509 PMID: 3873461 Document Number: 252381
The effects of low flow, low pressure pulsatile bypass were studied in 90 consecutive patients undergoing coronary artery surgery. Overall pump flow rate (OFR) was 19-49 (mean 31 .+-. 7) ml/kg/min at all temperatures. Moderate (28.degree. C) hypothermia was used. When cross-clamped flow was 17-49 (mean 27 .+-. 7) ml/kg/min and mean perfusion pressure 50-60 mmHg, priming volume (PV) was reduced to 1.45 .+-. 0.02 l (range 1.2-2.0 l). PV, cardioplegia and volume additions were considered as total bypass crystalloid (TBC) and this correlated positively with increased postoperative positive water balance (r = 0.58, P < 0.001). Bypass urine output averaged 135 .+-. 24 ml (range 0-1000 ml) was unrelated to OFR and correlated only with TBC (r = 0.47, P < 0.001). In 86 a single cardioplegia dose of 0.7 l (range 0.4-0.8 l) sufficed for this ischemic period (mean 46 .+-. 16 min). Four required a further 0.2-0.3 l. Their ischemic times were 44-74 min (mean 59 .+-. 13 PNS). Inotropes were used in only 3 patients. Postoperatively 7 required diuretics for low h urine flow. Of the 76 with normal preoperative renal function urea rose transiently in 15. Three had raised urea for over 9 days. Creatinine rose transiently in 7 but persisted in only 1. Plasma cortisol (n = 78) rose in 67 and fell in 11, indicating, overall, an adequate metabolic response. Plasma free hemoglobin before and after bypass varied widely and did not correlate with flow rate or perfusion time. Three patients had early post-operative neurological dysfunction. One had focal signs. All recovered spontaneously; their OFR were at both ends of the range. Maximum ventilation time was 17 h. Low-flow low-pressure pulsatile bypass is a safe and useful adjunct to cardiac surgery.