Effect of perfusionist technique on cerebral embolization during cardiopulmonary bypass

Abstract

Objective: To determine the association between high-intensity transient signals (HITS) and perfusionist interventions, purging techniques, pump flows and venous reservoir blood volume levels during cardiopulmonary bypass. Methods: Transcranial Doppler was used to detect HITS in the middle cerebral artery during the period of aortic crossclamping in patients undergoing coronary artery bypass grafting. Perfusionist-related interventions were recorded and included blood sampling (including the number of times that the oxygenator sampling manifold was purged), drug bolus injections and infusions (vasopressors, crystalloid and mannitol). Pump flows and venous reservoir volume levels were also documented. Results: There were 534 interventions in 90 patients [median number of interventions per patient: 6 (quartiles: 4, 8)]. The median total HITS count from all interventions was 17 (5, 37). This represented 38% of the total HITS counts during aortic crossclamping. Factors contributing to differences in the HITS count included type of intervention ( p<0.0001) and perfusionist (p=0.0012). Blood sampling ( p<0.001) and drug bolus injections (p=0.06) had higher HITS counts per patient than infusions. Repetitive purging significantly increased HITS counts (r=0.74; p<0.001). Purging perfusionists (purging: 1 - 10 times) had higher HITS counts per patient [5 HITS (1, 15) than nonpurgers [0 HITS (0, 1) p<0.0001]. HITS counts were significantly correlated with reservoir volumes (r=-0.20, p=0.017) and pump flow rates (r=0.21, p=0.008). Reservoir volume levels ≤ 800 mL were associated with higher HITS counts per intervention [11 HITS (2, 27)] during blood sampling compared with higher volume levels [3 HITS (1, 10), p=0.001]. Conclusions: Cerebral emboli associated with perfusionist interventions can be minimized by not purging the sampling manifold, using continuous infusions rather than bolus injections, and maintaining high blood-volume levels (>800 mL) in the venous reservoir.