Postoperative intubation time is associated with acute kidney injury in cardiac surgical patientsReport as inadecuate

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Critical Care

, 18:547

First Online: 03 October 2014Received: 16 May 2014Accepted: 17 September 2014


IntroductionAcute kidney injury AKI is a frequent complication after cardiac surgery and is associated with a poor prognosis. Mechanical ventilation is an important risk factor for developing AKI in critically ill patients. Ventilation with high tidal volumes has been associated with postoperative organ dysfunction in cardiac surgical patients. No data are available about the effects of the duration of postoperative respiratory support in the immediate postoperative period on the incidence of AKI in patients after cardiac surgery.

MethodWe performed a secondary analysis of 584 elective cardiac surgical patients enrolled in an observational trial on the association between preoperative cerebral oxygen saturation and postoperative organ dysfunction and analyzed the incidence of AKI in patients with different times to extubation. The latter variable was graded in 4 h intervals if below 16 h or equal to or greater than 16 h. AKI was staged according to the AKI Network criteria.

ResultsOverall, 165 28.3% patients developed AKI any stage, 43 7.4% patients needed renal replacement therapy. Patients developing AKI had a significantly P <0.001 lower renal perfusion pressure RPP in the first 8 hours after surgery 57.4 mmHg 95% CI: 56.0 to 59.0 mmHg than patients with a postoperatively preserved renal function 60.5 mmHg 95% CI: 59.9 to 61.4 mmHg. The rate of AKI increased from 17.0% in patients extubated within 4 h postoperatively to 62.3% in patients ventilated for more than 16 h P <0.001. Multivariate logistic regression analysis of variables significantly associated with AKI in the univariate analysis revealed that the time to the first extubation OR: 1.024-hour, 95% CI: 1.011 to 1.044-hour; P <0.001 and RPP OR: 0.963-mmHg; 95% CI: 0.934 to 0.992; P <0.001 were independently associated with AKI.

ConclusionWithout taking into account potentially unmeasured confounders, these findings are suggestive that the duration of postoperative positive pressure ventilation is an important and previously unrecognized risk factor for AKI in cardiac surgical patients, independent from low RPP as an established AKI trigger, and that even a moderate delay of extubation increases AKI risk. If replicated independently, these findings may have relevant implications for clinical care and for further studies aiming at the prevention of cardiac surgery associated AKI.

AbbreviationsAKIacute kidney injury

AKINAcute Kidney Injury Network

BIPAPbiphasic intermittent positive airway pressure

CABGcoronary artery bypass grafting

CIcardiac index

CPAPcontinuous positive airway pressure

CPBcardiopulmonary bypass

CSA-AKIcardiac surgery-associated acute kidney injury

CVPcentral venous pressure

eGFRestimated glomerular filtration rate

HDUhigh dependency unit

ICUintensive care unit

IPAPintermittent positive airway pressure

LVEFleft ventricular ejection fraction

MAPmean arterial blood pressure

NIRSnear-infrared spectroscopy

PAPmean pulmonary arterial pressure

PEEPpositive end-expiratory pressure

PSVpressure support ventilation

RPPrenal perfusion pressure

RRTrenal replacement therapy

ScO2cerebral oxygen saturation

ScvO2central venous oxygen saturation

Electronic supplementary materialThe online version of this article doi:10.1186-s13054-014-0547-4 contains supplementary material, which is available to authorized users.

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Author: Matthias Heringlake - Yvonne Nowak - Julika Schön - Jens Trautmann - Astrid Ellen Berggreen - Efstratios I Charitos - Hau


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