Absence of association between whole blood viscosity and delirium after cardiac surgery: a case-controlled study.

Shokoufeh Cheheilisobbi,Wilson F Abdo,Linda Ceelen,Mark Van Den Boogaard,Henry A Van Swieten,Peter Pickkers,Gheorghe Pop,Arjen J C Slooter

doi:10.1186/s13019-016-0517-9

Abstract

BackgroundDelirium after cardiothoracic surgery is common and associated with impaired outcomes. Although several mechanisms have been proposed (including changes in cerebral perfusion), the pathophysiology of postoperative delirium remains unclear. Blood viscosity is related to cerebral perfusion and thereby might contribute to the development of delirium after cardiothoracic surgery. The aim of this study was to investigate whether whole blood viscosity differs between cardiothoracic surgery patients with and without delirium.MethodsIn this observational study postoperative whole blood viscosity of patients that developed delirium (cases) were compared with non-delirious cardiothoracic surgery patients (controls). Cases were matched with the controls, yielding a 1:4 case–control study. Serial hematocrit, fibrinogen, and whole blood viscosity were determined pre-operatively and at each postoperative day. Delirium was assessed using the validated Confusion Assessment Method for the Intensive Care Unit or Delirium Screening Observation scale.ResultsIn total 80 cardiothoracic surgery patients were screened of whom 12 delirious and 48 matched non-delirious patients were included. No significant difference was found between both groups in fibrinogen (p = 0.36), hematocrit (p = 0.23) and the area under curve of the whole blood viscosity between shear rates 0.02 and 50 s-1 (p = 0.80) or between shear rates 0.02 and 5 s-1 (p = 0.78).ConclusionIn this case control study in cardiothoracic surgery patients changes in whole blood viscosity were not associated with the development of delirium.

Highlights

Delirium after cardiothoracic surgery is common and associated with impaired outcomes
Other exclusion criteria were the use of blood cardioplegia, since this is associated with the development of postoperative neurological events [15], preoperative use of heparin, since heparin could decrease the blood viscosity [16], extracorporeal circulation (ECC) time exceeding 120 min, because ECC time is associated with neurological injury [17], or inability to screen for delirium
In this exploratory case–control study we did not find differences in the changes in hematocrit, fibrinogen levels or whole blood viscosity in postcardiothoracic surgery patients who did or did not develop delirium. These findings indicate that changes in viscosity during the postoperative phase do not play a role in the development of post-operative delirium in cardiothoracic surgery patients

Summary

Introduction

Delirium after cardiothoracic surgery is common and associated with impaired outcomes. Several mechanisms have been proposed (including changes in cerebral perfusion), the pathophysiology of postoperative delirium remains unclear. Blood viscosity is related to cerebral perfusion and thereby might contribute to the development of delirium after cardiothoracic surgery. The aim of this study was to investigate whether whole blood viscosity differs between cardiothoracic surgery patients with and without delirium. In cardiothoracic surgery the incidence of delirium during the postoperative on the ICU is reported to be between 13 % and 42 % [3, 4]. Apart from other possible pathways related to the development of delirium [8], reduced cerebral blood flow during delirium with normalization during recovery has been reported [9, 10]. Changes in blood viscosity could relate to occurrence of postoperative

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