title: Prewarming neurosurgical patients to minimize hypotension on induction of anesthesia: a randomized trial.
abstract: OBJECTIVE
  Prewarming prior to surgery is effective in preventing perioperative hypothermia. There is a paucity of evidence, however, regarding the hemodynamic effects of prewarming. We hypothesized that the nadir mean arterial pressure during anesthesia induction would be higher after prewarming than after no prewarming.
  
  
  METHODS
  We randomized 32 patients prior to elective neurosurgery to receive either one hour of forced-air convective warming at 46°C or routine care (full body blanket with convective warmer attached but not turned on). All patients had invasive blood pressure, heart rate, and core temperature monitoring before and during warming and underwent a protocolized intravenous anesthetic induction with propofol and remifentanil target-controlled infusions. The primary endpoint was the nadir mean arterial blood pressure (MAP) during induction. Hypotension was defined as systolic blood pressure (SBP) < 90 mmHg, MAP < 60 mmHg, or a reduction in either SBP or MAP > 20% from baseline values.
  
  
  RESULTS
  No difference was found in the mean (SD) nadir MAP between the prewarmed group and the control group [64 (11) mmHg vs 68 (16) mmHg, respectively; mean difference, 5 mmHg; 95% confidence interval (CI), -6 to 15; P = 0.36]. Similarly, there was no difference between groups in the incidence of hypotension (100% of prewarmed vs 93% of control patients; relative risk, 1.07; 95% CI, 0.94 to 1.23; P = 0.32) or in the requirement for vasopressors during induction (four patients in each group required metaraminol; P = 1.00).
  
  
  CONCLUSIONS
  Prewarming with convective forced air for one hour prior to intravenous anesthetic induction did not prevent hypotension during the induction period (Australian New Zealand Clinical Trials Registry [ANZCTR] ACTRN12615000431527).
authors: Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne, Australia. jai.darvall@mh.org.au.|Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia. jai.darvall@mh.org.au.
authors: Jai
authors: http://orcid.org/0000-0003-0579-8931
authors: J
authors: Darvall
authors: Royal Melbourne Clinical School, University of Melbourne, Melbourne, Australia.
authors: Rukman
authors: R
authors: Vijayakumar
authors: Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne, Australia.|Anaesthesia, Perioperative and Pain Medicine Unit, University of Melbourne, Melbourne, Australia.|Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Australia.|Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors: Kate
authors: K
authors: Leslie
mesh_terms: D000328:Adult; D000368:Aged; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007022:Hypotension / Q000453:epidemiology / Q000517:prevention & control*; D007035:Hypothermia / Q000517:prevention & control*; D015994:Incidence; D008297:Male; D008680:Metaraminol / Q000008:administration & dosage; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D010880:Piperidines / Q000008:administration & dosage; D015742:Propofol / Q000008:administration & dosage; D000077208:Remifentanil
chemical_list: D018686:Anesthetics, Intravenous; D010880:Piperidines; D008680:Metaraminol; D000077208:Remifentanil; D015742:Propofol