Humara Poonawala

The clinical utility of an index of global oxygenation for guiding red blood cell transfusion in cardiac surgery

BACKGROUND: This observational study explored the potential utility of oxygen extraction ratio (O2ER) as an adjunct to the hemoglobin (Hb) concentration for guiding red blood cell (RBC) transfusion decisions after cardiac surgery with cardiopulmonary bypass (CPB).

N-acetylcysteine is associated with increased blood loss and blood product utilization during cardiac surgery.

Objective:When used to prevent perioperative inflammation and ischemia–reperfusion injury, N-acetylcysteine may inadvertently impair hemostasis. We, therefore, performed a post hoc analysis of a recent randomized controlled trial in cardiac surgery to determine whether N-acetylcysteine was associated with increased blood loss and blood product transfusion. Design:Blinded (patients, caregivers, outcome assessors) placebo-controlled parallel group randomized trial (www.ClinicalTrials.gov ID NCT00188630). Setting:Tertiary care hospital in Toronto, Ontario, Canada (September 2003 to October 2005). Patients:A total of 177 patients with preexisting moderate renal insufficiency (estimated glomerular filtration rate ≤60 mL/min) and undergoing cardiac surgery. Interventions:Eighty-nine patients were randomized to receive intravenous N-acetylcysteine (100 mg/kg bolus; 20 mg·kg−1·hr−1 infusion until 4 hours after cardiopulmonary bypass), and 88 were randomized to receive placebo. Measurements and Main Results:We used laboratory markers (hemoglobin, platelets, coagulation), chest-tube blood loss, and blood product transfusion to evaluate hemostasis. Compared with placebo, patients who received N-acetylcysteine arm experienced a mean 24-hour chest-tube blood loss that was 261 mL higher (95% confidence interval [CI] 93–488 mL, p = 0.008), and were transfused 1.6 more units of red blood cells (95% CI 0.4–3.1 units, p = 0.02) during hospitalization. The risk of receiving ≥5 units of red blood cells within 24 hours of surgery was significantly higher with N-acetylcysteine (relative risk 1.85, 95% CI 1.06–3.21, p = 0.03; adjusted relative risk 2.09, 95% CI 1.24–3.83, p = 0.005). Conclusions:In patients who have preexisting moderate renal insufficiency and are undergoing cardiac surgery, N-acetylcysteine was associated with important effects on blood loss and blood product transfusion. Clinicians and researchers should, therefore, consider the potential for impaired hemostasis when using N-acetylcysteine in the perioperative setting. Further research is needed to elucidate mechanisms by which N-acetylcysteine may impair hemostasis, and the risk–benefit profile of N-acetylcysteine for perioperative organ protection.

Cerebral oximetry and postoperative delirium after cardiac surgery: a randomised, controlled trial

Postoperative delirium is associated with increased morbidity and mortality. We hypothesised that restoration of regional cerebral oxygen desaturation would reduce the incidence of postoperative delirium in elderly patients after cardiac surgery. After institutional ethics review board approval and informed consent, a double‐blinded, prospective, randomised, controlled trial was conducted in patients ≥ 60 years of age undergoing cardiac surgery with cardiopulmonary bypass. In the intervention group, an algorithm was commenced if regional cerebral oxygen saturation decreased below 75% of baseline value for 1 min or longer. In the control group, the cerebral oximetry monitor screen was electronically blinded. Assessment of delirium was performed with confusion assessment method for intensive care unit or confusion assessment method after discharge from intensive care unit at 12‐h intervals for seven postoperative days. Postoperative delirium was present in 30 out of 123 (24.4%) and 31 out of 126 (24.6%) patients in the intervention and control groups, respectively, odds ratio 0.98 (95%CI 0.55–1.76), p = 0.97. Postoperative delirium was present in 20 (71%) out of 28 and in 41 (18%) out of 221 patients with baseline regional cerebral oxygen saturation ≤ 50, or > 50%, respectively, p = 0.0001. Higher baseline regional cerebral oxygen saturation and body mass index were protective against postoperative delirium. Restoration of regional cerebral oxygen desaturation did not result in lower postoperative delirium after cardiac surgery. Pre‐operative regional cerebral oxygen saturation ≤ 50% was associated with increased postoperative delirium rates in elderly patients following cardiac surgery.

Delirium and organic brain injury after cardiac surgery

Rita Katznelson, Toronto General Hospital, University Health Network, Toronto, ON, Canada; Susan Abbey, Toronto General Hospital, University Health Network; W Scott Beattie, Toronto General Hospital, University Health Network; L Minkovich, Toronto General Hospital, University Health Network; Z Friedman, Mount Sinai Hospital, University Health Network; H Poonawala, Toronto General Hospital, University Health Network; J Karski, Toronto General Hospital, University Health Network; G Djaiani, Toronto General Hospital, University Health Network;