Brain damage and mortality in dogs following pulsatile and non-pulsatile blood flows in extracorporeal circulation

Abstract

In a series of 20 dog experiments, total cardiac bypass was followed by a high rate of mortality during the first 12 postoperative hours. Only five dogs survived for one week, but a further three dogs were perfuse-fixed after shorter periods of survival. All dogs developed pulmonary alveolar haemorrhages and seven of the eight perfuse-fixed brains exhibited brain damage. Diffuse nerve cell changes were found in the brains of dogs subjected to non-pulsatile blood flow. Focal brain lesions were found following both pulsatile and non-pulsatile blood flows. The lesions varied from staining pallor and rarefaction of the neuropil to total nerve cell loss and glial infiltration depending upon the duration of survival. When considered in conjunction with a previous series of experiments, these results show that the diffuse nerve cell changes associated with roller pump perfusions can be avoided by using a new pulsatile pump, but focal brain damage was not eliminated, and lung damage and mortality were not reduced.

Effects of pulsatile and non-pulsatile perfusion on the isolated canine heart

“…However, the physiologic advantages of pulsatile flow to the heart are well supported [2,16,35]. There is evidence that pulsatile flow is superior to linear flow including hemodynamic [23,29], metabolic [27,[30][31][32]34], and histologic benefits particularly to the kidney [5] and brain tissues [36]. The use of non-pulsatile perfusion can even increase regional ischemia in the canine myocardium during cardiopulmonary bypass [3].…”

Brain damage and neurological outcome after open-heart surgery.

“…Cerebral perfusion inadequacy may be caused by hypothermia,24 hypoxia and hypotension6" or even by obstruction of the circulation due to malposition of the intravascular cannulae.2" Brain metabolic rate has been shown to fall during cardiopulmonary bypass both in clinical5 26 and in animal1827 studies. There have also been reports of significant and not immediately reversible depression of cerebral blood flow and metabolism when associated with even short periods of bypass and supposedly caused by microem,bolisation.…”

“…"8 On the other hand, fall of metabolic rate thought to be due to decreased oxygen availabillity caused by haemodilution or loss of pulsatile pressure has been described. 26 This study, part of a larger research programme investigating the effects of cardiac surgery on the central nervous system, was initiated to study the determinants and clinical characteristics of neurological complications related both to severe valvular disease and to open-heart surgery.…”

The assessment of pulsatile blood flow

“…[4][5][6]12 However, some of the evidence relating to specific organ damage has been disputed and clinical experience remains unconvincing. The principal reason for this continuing controversy may be that different investigators have used different kinds of pulsatile flow and this has followed from the lack of satisfactory working definitions for pulsatile and nonpulsatile flows, Indeed, in most published work, pulsatile flow is not defined and illustrated only by a peripheral artery blood pressure recording.…”