A Warm Air Blanket is Superior to a Heated Mattress in Preventing Perioperative Hypothermia in Orthopedic Arthroplasties, a Time-Series Analyses.

BACKGROUND: Hypothermia is a common perioperative problem that can lead to severe complications. We evaluated whether a heated mattress (HM) is superior to a warm air blanket (WA) in preventing perioperative hypothermia in patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA). METHODS: A retrospective cohort study was performed in a teaching hospital and data were collected for all patients undergoing THA or TKA between January 1, 2015 and May 1, 2022. We used logistic and linear regressions to analyze hypothermia occurrence and important complications. Results were adjusted for confounders and time, and was present in all subgroups and after imputation of missing data. RESULTS: In total, 4,683 of 5,497 patients had information on type of heating. We found more perioperative hypothermia in patients treated with an HM compared to a WA for both THA (odds ratio-adjusted 1.42 [1.0 to 1.6] P = .06) and TKA (odds ratio-adjusted 2.10 [1.5 to 3.0] P < .01). There was no difference in postoperative infections between groups (all between 0.5% and 1.3%). Patients who had an HM significantly stayed longer in the postoperative ward (a mean difference of 4 [TKA] to 6 [THA] minutes, P < .01), but there was no difference in hospital stay. CONCLUSION: A WA is superior compared to an HM in preventing perioperative hypothermia, with no increased risk of complications. Patients who have an HM stayed longer at the postoperative ward, potentially because of higher hypothermia rates. Therefore, it is suggested to use a WA instead of an HM.

Mixed-effects modeling of the influence of alfentanil on propofol pharmacokinetics.

BACKGROUND: The influence of alfentanil on the pharmacokinetics of propofol is poorly understood. Therefore, the authors studied the effect of a pseudo-steady state concentration of alfentanil on the pharmacokinetics of propofol. METHODS: The pharmacokinetics of propofol were studied on two occasions in eight male volunteers in a randomized crossover manner with a 3-week interval. While volunteers breathed 30% O2 in air, 1 mg/kg intravenous propofol was given in 1 min, followed by 3 mg.kg(-1).h(-1) for 59 min (sessions A and B). During session B, a target-controlled infusion of alfentanil (target concentration, 80 ng/ml) was given from 10 min before the start until 6 h after termination of the propofol infusion. Blood pressure, cardiac output, electrocardiogram, respiratory rate, oxygen saturation, and end-tidal carbon dioxide were monitored. Venous blood samples for determination of the blood propofol and plasma alfentanil concentration were collected until 6 h after termination of the propofol infusion. Nonlinear mixed-effects population pharmacokinetic models examining the influence of alfentanil and hemodynamic parameters on propofol pharmacokinetics were constructed. RESULTS: A two-compartment model, including a lag time accounting for the venous blood sampling, adequately described the concentration-time curves of propofol. Alfentanil decreased the elimination clearance of propofol from 2.1 l/min to 1.9 l/min, the distribution clearance from 2.7 l/min to 2.0 l/min, and the peripheral volume of distribution from 179 l to 141 l. Scaling the pharmacokinetic parameters to cardiac output, heart rate, and plasma alfentanil concentration significantly improved the model. CONCLUSIONS: Alfentanil alters the pharmacokinetics of propofol. Cardiac output and heart rate have an important influence on the pharmacokinetics of propofol.

Propofol reduces perioperative remifentanil requirements in a synergistic manner: response surface modeling of perioperative remifentanil-propofol interactions.

BACKGROUND: Remifentanil is often combined with propofol for induction and maintenance of total intravenous anesthesia. The authors studied the effect of propofol on remifentanil requirements for suppression of responses to clinically relevant stimuli and evaluated this in relation to previously published data on propofol and alfentanil. METHODS: With ethics committee approval and informed consent, 30 unpremedicated female patients with American Society of Anesthesiologists physical status class I or II, aged 18-65 yr, scheduled to undergo lower abdominal surgery, were randomly assigned to receive a target-controlled infusion of propofol with constant target concentrations of 2, 4, or 6 microg/ml. The target concentration of remifentanil was changed in response to signs of inadequate anesthesia. Arterial blood samples for the determination of remifentanil and propofol concentrations were collected after blood-effect site equilibration. The presence or absence of responses to various perioperative stimuli were related to the propofol and remifentanil concentrations by response surface modeling or logistic regression, followed by regression analysis. Both additive and nonadditive interaction models were explored. RESULTS: With blood propofol concentrations increasing from 2 to 7.3 microg/ml, the C(50) of remifentanil decreased from 3.8 ng/ml to 0 ng/ml for laryngoscopy, from 4.4 ng/ml to 1.2 ng/ml for intubation, and from 6.3 ng/ml to 0.4 ng/ml for intraabdominal surgery. With blood remifentanil concentrations increasing from 0 to 7 ng/ml, the C(50) of propofol for the return to consciousness decreased from 3.5 microg/ml to 0.6 microg/ml. CONCLUSIONS: Propofol reduces remifentanil requirements for suppression of responses to laryngoscopy, intubation, and intraabdominal surgical stimulation in a synergistic manner. In addition, remifentanil decreases propofol concentrations associated with the return of consciousness in a synergistic manner.