Maximising patient comfort during and after surgery is a primary concern of anaesthetists and oth... more Maximising patient comfort during and after surgery is a primary concern of anaesthetists and other perioperative clinicians, but objective measures of what constitutes patient comfort in the perioperative period remain poorly defined. The Standardised Endpoints in Perioperative Medicine initiative was established to derive a set of standardised endpoints for use in perioperative clinical trials. We undertook a systematic review to identify measures of patient comfort used in the anaesthetic, surgical, and other perioperative literature. A multi-round Delphi consensus process that included up to 89 clinician researchers was then used to refine a recommended list of outcome measures. We identified 122 studies in a literature search, which were the basis for a preliminary list of 24 outcome measures and their definitions. The response rates for Delphi Rounds 1, 2, and 3 were 100% (n=22), 90% (n=79), and 100% (n=13), respectively. A final list of six defined endpoints was identified: p...
Little is known about the relationship between perioperative high-sensitivity troponin T (hsTnT) ... more Little is known about the relationship between perioperative high-sensitivity troponin T (hsTnT) measurements and 30-day mortality and myocardial injury after noncardiac surgery (MINS). To determine the association between perioperative hsTnT measurements and 30-day mortality and potential diagnostic criteria for MINS (ie, myocardial injury due to ischemia associated with 30-day mortality). Prospective cohort study of patients aged 45 years or older who underwent inpatient noncardiac surgery and had a postoperative hsTnT measurement. Starting in October 2008, participants were recruited at 23 centers in 13 countries; follow-up finished in December 2013. Patients had hsTnT measurements 6 to 12 hours after surgery and daily for 3 days; 40.4% had a preoperative hsTnT measurement. A modified Mazumdar approach (an iterative process) was used to determine if there were hsTnT thresholds associated with risk of death and had an adjusted hazard ratio (HR) of 3.0 or higher and a risk of 30-da...
Background:Core temperature patterns in patients warmed with forced air remain poorly characteriz... more Background:Core temperature patterns in patients warmed with forced air remain poorly characterized. Also unknown is the extent to which transient and mild intraoperative hypothermia contributes to adverse outcomes in broad populations.Methods:We evaluated esophageal (core) temperatures in 58,814 adults having surgery lasting >60 min who were warmed with forced air. Independent associations between hypothermic exposure and transfusion requirement and duration of hospitalization were evaluated.Results:In every percentile subgroup, core temperature decreased during the first hour and subsequently increased. The mean lowest core temperature during the first hour was 35.7 ± 0.6°C. Sixty-four percent of the patients reached a core temperature threshold of <36°C 45 min after induction; 29% reached a core temperature threshold of <35.5°C. Nearly half the patients had continuous core temperatures <36°C for more than an hour, and 20% of the patients were <35.5°C for more than ...
Background There is substantial variability in the perioperative administration of aspirin in pat... more Background There is substantial variability in the perioperative administration of aspirin in patients undergoing noncardiac surgery, both among patients who are already on an aspirin regimen and among those who are not. Methods Using a 2-by-2 factorial trial design, we randomly assigned 10,010 patients who were preparing to undergo noncardiac surgery and were at risk for vascular complications to receive aspirin or placebo and clonidine or placebo. The results of the aspirin trial are reported here. The patients were stratified according to whether they had not been taking aspirin before the study (initiation stratum, with 5628 patients) or they were already on an aspirin regimen (continuation stratum, with 4382 patients). Patients started taking aspirin (at a dose of 200 mg) or placebo just before surgery and continued it daily (at a dose of 100 mg) for 30 days in the initiation stratum and for 7 days in the continuation stratum, after which patients resumed their regular aspirin regimen. The primary outcome was a composite of death or nonfatal myocardial infarction at 30 days. Results The primary outcome occurred in 351 of 4998 patients (7.0%) in the aspirin group and in 355 of 5012 patients (7.1%) in the placebo group (hazard ratio in the aspirin group, 0.99; 95% confidence interval [CI], 0.86 to 1.15; P = 0.92). Major bleeding was more common in the aspirin group than in the placebo group (230 patients [4.6%] vs. 188 patients [3.8%]; hazard ratio, 1.23; 95% CI, 1.01, to 1.49; P = 0.04). The primary and secondary outcome results were similar in the two aspirin strata. Conclusions Administration of aspirin before surgery and throughout the early postsurgical period had no significant effect on the rate of a composite of death or nonfatal myocardial infarction but increased the risk of major bleeding.
Background Marked activation of the sympathetic nervous system occurs during and after noncardiac... more Background Marked activation of the sympathetic nervous system occurs during and after noncardiac surgery. Low-dose clonidine, which blunts central sympathetic outflow, may prevent perioperative myocardial infarction and death without inducing hemodynamic instability. Methods We performed a blinded, randomized trial with a 2-by-2 factorial design to allow separate evaluation of low-dose clonidine versus placebo and low-dose aspirin versus placebo in patients with, or at risk for, atherosclerotic disease who were undergoing noncardiac surgery. A total of 10,010 patients at 135 centers in 23 countries were enrolled. For the comparison of clonidine with placebo, patients were randomly assigned to receive clonidine (0.2 mg per day) or placebo just before surgery, with the study drug continued until 72 hours after surgery. The primary outcome was a composite of death or nonfatal myocardial infarction at 30 days. Results Clonidine, as compared with placebo, did not reduce the number of primary-outcome events (367 and 339, respectively; hazard ratio with clonidine, 1.08; 95% confidence interval [CI], 0.93 to 1.26; P = 0.29). Myocardial infarction occurred in 329 patients (6.6%) assigned to clonidine and in 295 patients (5.9%) assigned to placebo (hazard ratio, 1.11; 95% CI, 0.95 to 1.30; P = 0.18). Significantly more patients in the clonidine group than in the placebo group had clinically important hypotension (2385 patients [47.6%] vs. 1854 patients [37.1%]; hazard ratio 1.32; 95% CI, 1.24 to 1.40; P<0.001). Clonidine, as compared with placebo, was associated with an increased rate of nonfatal cardiac arrest (0.3% [16 patients] vs. 0.1% [5 patients]; hazard ratio, 3.20; 95% CI, 1.17 to 8.73; P = 0.02). Conclusions Administration of low-dose clonidine in patients undergoing noncardiac surgery did not reduce the rate of the composite outcome of death or nonfatal myocardial infarction; it did, however, increase the risk of clinically important hypotension and nonfatal cardiac arrest.
Introduction Mild therapeutic hypothermia has been shown to improve outcome for patients after ca... more Introduction Mild therapeutic hypothermia has been shown to improve outcome for patients after cardiac arrest and may be beneficial for ischaemic stroke and myocardial ischaemia patients. However, in the awake patient, even a small decrease of core temperature provokes vigorous autonomic reactionsvasoconstriction and shivering-which both inhibit efficient core cooling. Meperidine and skin warming each linearly lower vasoconstriction and shivering thresholds. We tested whether a combination of skin warming and a medium dose of meperidine additively would reduce the shivering threshold to below 34°C without producing significant sedation or respiratory depression. Methods Eight healthy volunteers participated on four study days: (1) control, (2) skin warming (with forced air and warming mattress), (3) meperidine (target plasma level: 0.9 μg/ml), and (4) skin warming plus meperidine (target plasma level: 0.9 μg/ ml). Volunteers were cooled with 4°C cold Ringer lactate infused over a central venous catheter (rate ≈ 2.4°C/hour core temperature drop). Shivering threshold was identified by an increase of oxygen consumption (+20% of baseline). Sedation was assessed with the Observer's Assessment of Alertness/ Sedation scale. Results Control shivering threshold was 35.5°C ± 0.2°C. Skin warming reduced the shivering threshold to 34.9°C ± 0.5°C (p = 0.01). Meperidine reduced the shivering threshold to 34.2°C ± 0.3°C (p < 0.01). The combination of meperidine and skin warming reduced the shivering threshold to 33.8°C ± 0.2°C (p < 0.01). There were no synergistic or antagonistic effects of meperidine and skin warming (p = 0.59). Only very mild sedation occurred on meperidine days. Conclusion A combination of meperidine and skin surface warming reduced the shivering threshold to 33.8°C ± 0.2°C via an additive interaction and produced only very mild sedation and no respiratory toxicity.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 2013
Purpose Perioperative hypothermia is still a common occurrence, and it can be difficult to measur... more Purpose Perioperative hypothermia is still a common occurrence, and it can be difficult to measure a patient's core temperature accurately, especially during regional anesthesia, with placement of a laryngeal mask airway device, or postoperatively. We evaluated a new disposable double-sensor thermometer and compared the resulting temperatures with those of a distal esophageal thermometer and a bladder thermometer in patients undergoing general and regional anesthesia, respectively. Furthermore, we compared the accuracy of the thermometer between regional and general anesthesia, since forehead microcirculation might differ between the two types of anesthesia. Methods We assessed core temperature in 36 general anesthesia patients and 20 patients having regional anesthesia for orthopedic surgery. The temperatures obtained using the double-sensor thermometer were compared with those obtained with the distal esophageal
Background. Accurate measurement of core temperature is a standard component of perioperative and... more Background. Accurate measurement of core temperature is a standard component of perioperative and intensive care patient management. However, core temperature measurements are difficult to obtain in awake patients. A new non-invasive thermometer has been developed, combining two sensors separated by a known thermal resistance ('double-sensor' thermometer). We thus evaluated the accuracy of the double-sensor thermometer compared with a distal oesophageal thermometer to determine if the double-sensor thermometer is a suitable substitute. Methods. In perioperative and intensive care patient populations (n=68 total), double-sensor measurements were compared with measurements from a distal oesophageal thermometer using Bland-Altman analysis and Lin's concordance correlation coefficient (CCC). Results. Overall, 1287 measurement pairs were obtained at 5 min intervals. Ninety-eight per cent of all double-sensor values were within +0.58C of oesophageal temperature. The mean bias between the methods was 20.088C; the limits of agreement were 20.668C to 0.508C. Sensitivity and specificity for detection of fever were 0.86 and 0.97, respectively. Sensitivity and specificity for detection of hypothermia were 0.77 and 0.93, respectively. Lin's CCC was 0.93. Conclusions. The new double-sensor thermometer is sufficiently accurate to be considered an alternative to distal oesophageal core temperature measurement, and may be particularly useful in patients undergoing regional anaesthesia.
Background The perioperative period is characterized by an intense inflammatory response. Periope... more Background The perioperative period is characterized by an intense inflammatory response. Perioperative inflammation promotes postoperative morbidity and increases mortality. Blunting the inflammatory response to surgical trauma might thus improve perioperative outcomes. We are studying three interventions that potentially modulate perioperative inflammation: corticosteroids, tight glucose control, and light anesthesia. Methods/Design The DeLiT Trial is a factorial randomized single-center trial of dexamethasone vs placebo, intraoperative tight vs. conventional glucose control, and light vs deep anesthesia in patients undergoing major non-cardiac surgery. Anesthetic depth will be estimated with Bispectral Index (BIS) monitoring (Aspect medical, Newton, MA). The primary outcome is a composite of major postoperative morbidity including myocardial infarction, stroke, sepsis, and 30-day mortality. C-reactive protein, a measure of the inflammatory response, will be evaluated as a seconda...
Study Objective: To evaluate the postoperative hemodynamic and thermoregulatory consequences of i... more Study Objective: To evaluate the postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia. Design: Prospective, randomized clinical trial. Setting: Operating room and postanesthesia care unit of a university hospital. Patients: 74 healthy, ASA status I, II, and III patients (average age 58 yrs) undergoing elective colon surgery. Interventions: Patients were randomly assigned to be kept normothermic or =Z.YC hypothermic during surgery. Anesthesia was maintained with isoflurane, nitrous oxide, and fentanyl. Postoperatively, surgical pain was treated with patient-controlled analgesia (PCA) opioid. Measurements and Main Results: An observer blinded to group assignment and core temperatures evaluated shivering, thermal comfort, surgical pain, heart rates (HRs), and blood p ressures (BPS) during the first six postoperative hours. Morphometric characteristics, oxygen saturation, fluid balance, PCA-administered opioid, and visual analog pain scores were comparable in the two groups. Hypothermic patients felt uncomfortably cold during recovery, and their postoperative core temperatures remained significantly less than in the normothermic patients for more than four hours. Peripheral vasoconstriction and shivering were common in the hypothermic patients but rare in those kept normothermic. HRs and BPS were comparable in the two groups. Conclusions: These data confirm that the effects of intraoperative hypothermia on postoperative HR and BP are modest in relatively young, generally healthy patients. In contrast, intraoperative hypothermia caused substantial postoperative thermal discomfort, and full recovery from hypothermia required many hours. Delayed return to core normothermia apparently resulted largely from postoperative thermoregulatory impairment.
Background Patients may require perioperative cooling for a variety of reasons including treatmen... more Background Patients may require perioperative cooling for a variety of reasons including treatment of a malignant hyperthermia crisis and induction of therapeutic hypothermia for neurosurgery. The authors compared heat transfer and core cooling rates with five cooling methods. Methods Six healthy volunteers were anesthetized with desflurane and nitrous oxide. The cooling methods were 1) circulating water (5 degrees C, full-length mattress and cover), 2) forced air (10 degrees C, full-length cover), 3) gastric lavage (500 ml iced water every 10 min), 4) bladder lavage (300 ml iced Ringer's solution every 10 min), and 5) ice-water immersion. Each method was applied for 40 min or until the volunteers' core temperatures approached 34 degrees C. The volunteers were rewarmed to normothermia between treatments. Core cooling rates were evaluated using linear regression. Results The first volunteer developed abdominal cramping and diarrhea after gastric lavage. Consequently, the tech...
Background Core hypothermia after induction of general anesthesia results from an internal core-t... more Background Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution. Methods Six minimally clothed male volunteers in an approximately 22 degrees C environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and...
Background Forced-air warming is sometimes unable to maintain perioperative normothermia. Therefo... more Background Forced-air warming is sometimes unable to maintain perioperative normothermia. Therefore, the authors compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34 degrees C. The volunteers were subsequently warmed for 2.5 h with either a circulating-water garment or a forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and "deep" hand and foot thermometers. Results Heat production (approximately 60 kcal/h) and loss (approximately 45 kcal/h) were similar with each treatment befor...
Background:Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) a... more Background:Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) and myocardial injury, but what blood pressures are unsafe is unclear. The authors evaluated the association between the intraoperative mean arterial pressure (MAP) and the risk of AKI and myocardial injury.Methods:The authors obtained perioperative data for 33,330 noncardiac surgeries at the Cleveland Clinic, Ohio. The authors evaluated the association between intraoperative MAP from less than 55 to 75 mmHg and postoperative AKI and myocardial injury to determine the threshold of MAP where risk is increased. The authors then evaluated the association between the duration below this threshold and their outcomes adjusting for potential confounding variables.Results:AKI and myocardial injury developed in 2,478 (7.4%) and 770 (2.3%) surgeries, respectively. The MAP threshold where the risk for both outcomes increased was less than 55 mmHg. Compared with never developing a MAP less than 55 mm...
We compared changes in core temperature and systemic heat balance with a new negative pressure/wa... more We compared changes in core temperature and systemic heat balance with a new negative pressure/warming device (Vital Heat) that uses negative pressure combined with heat to facilitate warming in vasoconstricted postoperative patients to those resulting from passive insulation or forced air. Seven healthy volunteers were anesthetized and cooled to a tympanic membrane temperature near 34°C. Anesthesia was discontinued and shivering was prevented by using meperidine. The vasoconstricted volunteers were rewarmed for 2 h using three randomly assigned methods: 1) Vital Heat plus cotton blanket; 2) one layer of cotton blanket; 3) forced-air warming. Thermal flux was recorded from 15 skin-surface sites; metabolic heat production was estimated from total body oxygen consumption. Metabolic heat production remained
Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effec... more Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effects are unknown. We tested the hypothesis that dantrolene reduces the threshold (triggering core temperature) and gain (incremental increase) of shivering. With IRB approval and informed consent, healthy volunteers were evaluated on two random days: control and dantrolene (≈2.5 mg/kg plus a continuous infusion). In study 1, 9 men were warmed until sweating was provoked and then cooled until arterio-venous shunt constriction and shivering occurred. Sweating was quantified on the chest using a ventilated capsule. Absolute right middle fingertip blood flow was quantified using venousocclusion volume plethysmography. A sustained increase in oxygen consumption identified the shivering threshold. In study 2, 9 men were given cold Ringer's solution IV to reduce core temperature ≈2°C/h. Cooling was stopped when shivering intensity no longer increased with further core cooling. The gain of shivering was the slope of oxygen consumption vs. core temperature regression. In Study
Maximising patient comfort during and after surgery is a primary concern of anaesthetists and oth... more Maximising patient comfort during and after surgery is a primary concern of anaesthetists and other perioperative clinicians, but objective measures of what constitutes patient comfort in the perioperative period remain poorly defined. The Standardised Endpoints in Perioperative Medicine initiative was established to derive a set of standardised endpoints for use in perioperative clinical trials. We undertook a systematic review to identify measures of patient comfort used in the anaesthetic, surgical, and other perioperative literature. A multi-round Delphi consensus process that included up to 89 clinician researchers was then used to refine a recommended list of outcome measures. We identified 122 studies in a literature search, which were the basis for a preliminary list of 24 outcome measures and their definitions. The response rates for Delphi Rounds 1, 2, and 3 were 100% (n=22), 90% (n=79), and 100% (n=13), respectively. A final list of six defined endpoints was identified: p...
Little is known about the relationship between perioperative high-sensitivity troponin T (hsTnT) ... more Little is known about the relationship between perioperative high-sensitivity troponin T (hsTnT) measurements and 30-day mortality and myocardial injury after noncardiac surgery (MINS). To determine the association between perioperative hsTnT measurements and 30-day mortality and potential diagnostic criteria for MINS (ie, myocardial injury due to ischemia associated with 30-day mortality). Prospective cohort study of patients aged 45 years or older who underwent inpatient noncardiac surgery and had a postoperative hsTnT measurement. Starting in October 2008, participants were recruited at 23 centers in 13 countries; follow-up finished in December 2013. Patients had hsTnT measurements 6 to 12 hours after surgery and daily for 3 days; 40.4% had a preoperative hsTnT measurement. A modified Mazumdar approach (an iterative process) was used to determine if there were hsTnT thresholds associated with risk of death and had an adjusted hazard ratio (HR) of 3.0 or higher and a risk of 30-da...
Background:Core temperature patterns in patients warmed with forced air remain poorly characteriz... more Background:Core temperature patterns in patients warmed with forced air remain poorly characterized. Also unknown is the extent to which transient and mild intraoperative hypothermia contributes to adverse outcomes in broad populations.Methods:We evaluated esophageal (core) temperatures in 58,814 adults having surgery lasting >60 min who were warmed with forced air. Independent associations between hypothermic exposure and transfusion requirement and duration of hospitalization were evaluated.Results:In every percentile subgroup, core temperature decreased during the first hour and subsequently increased. The mean lowest core temperature during the first hour was 35.7 ± 0.6°C. Sixty-four percent of the patients reached a core temperature threshold of <36°C 45 min after induction; 29% reached a core temperature threshold of <35.5°C. Nearly half the patients had continuous core temperatures <36°C for more than an hour, and 20% of the patients were <35.5°C for more than ...
Background There is substantial variability in the perioperative administration of aspirin in pat... more Background There is substantial variability in the perioperative administration of aspirin in patients undergoing noncardiac surgery, both among patients who are already on an aspirin regimen and among those who are not. Methods Using a 2-by-2 factorial trial design, we randomly assigned 10,010 patients who were preparing to undergo noncardiac surgery and were at risk for vascular complications to receive aspirin or placebo and clonidine or placebo. The results of the aspirin trial are reported here. The patients were stratified according to whether they had not been taking aspirin before the study (initiation stratum, with 5628 patients) or they were already on an aspirin regimen (continuation stratum, with 4382 patients). Patients started taking aspirin (at a dose of 200 mg) or placebo just before surgery and continued it daily (at a dose of 100 mg) for 30 days in the initiation stratum and for 7 days in the continuation stratum, after which patients resumed their regular aspirin regimen. The primary outcome was a composite of death or nonfatal myocardial infarction at 30 days. Results The primary outcome occurred in 351 of 4998 patients (7.0%) in the aspirin group and in 355 of 5012 patients (7.1%) in the placebo group (hazard ratio in the aspirin group, 0.99; 95% confidence interval [CI], 0.86 to 1.15; P = 0.92). Major bleeding was more common in the aspirin group than in the placebo group (230 patients [4.6%] vs. 188 patients [3.8%]; hazard ratio, 1.23; 95% CI, 1.01, to 1.49; P = 0.04). The primary and secondary outcome results were similar in the two aspirin strata. Conclusions Administration of aspirin before surgery and throughout the early postsurgical period had no significant effect on the rate of a composite of death or nonfatal myocardial infarction but increased the risk of major bleeding.
Background Marked activation of the sympathetic nervous system occurs during and after noncardiac... more Background Marked activation of the sympathetic nervous system occurs during and after noncardiac surgery. Low-dose clonidine, which blunts central sympathetic outflow, may prevent perioperative myocardial infarction and death without inducing hemodynamic instability. Methods We performed a blinded, randomized trial with a 2-by-2 factorial design to allow separate evaluation of low-dose clonidine versus placebo and low-dose aspirin versus placebo in patients with, or at risk for, atherosclerotic disease who were undergoing noncardiac surgery. A total of 10,010 patients at 135 centers in 23 countries were enrolled. For the comparison of clonidine with placebo, patients were randomly assigned to receive clonidine (0.2 mg per day) or placebo just before surgery, with the study drug continued until 72 hours after surgery. The primary outcome was a composite of death or nonfatal myocardial infarction at 30 days. Results Clonidine, as compared with placebo, did not reduce the number of primary-outcome events (367 and 339, respectively; hazard ratio with clonidine, 1.08; 95% confidence interval [CI], 0.93 to 1.26; P = 0.29). Myocardial infarction occurred in 329 patients (6.6%) assigned to clonidine and in 295 patients (5.9%) assigned to placebo (hazard ratio, 1.11; 95% CI, 0.95 to 1.30; P = 0.18). Significantly more patients in the clonidine group than in the placebo group had clinically important hypotension (2385 patients [47.6%] vs. 1854 patients [37.1%]; hazard ratio 1.32; 95% CI, 1.24 to 1.40; P<0.001). Clonidine, as compared with placebo, was associated with an increased rate of nonfatal cardiac arrest (0.3% [16 patients] vs. 0.1% [5 patients]; hazard ratio, 3.20; 95% CI, 1.17 to 8.73; P = 0.02). Conclusions Administration of low-dose clonidine in patients undergoing noncardiac surgery did not reduce the rate of the composite outcome of death or nonfatal myocardial infarction; it did, however, increase the risk of clinically important hypotension and nonfatal cardiac arrest.
Introduction Mild therapeutic hypothermia has been shown to improve outcome for patients after ca... more Introduction Mild therapeutic hypothermia has been shown to improve outcome for patients after cardiac arrest and may be beneficial for ischaemic stroke and myocardial ischaemia patients. However, in the awake patient, even a small decrease of core temperature provokes vigorous autonomic reactionsvasoconstriction and shivering-which both inhibit efficient core cooling. Meperidine and skin warming each linearly lower vasoconstriction and shivering thresholds. We tested whether a combination of skin warming and a medium dose of meperidine additively would reduce the shivering threshold to below 34°C without producing significant sedation or respiratory depression. Methods Eight healthy volunteers participated on four study days: (1) control, (2) skin warming (with forced air and warming mattress), (3) meperidine (target plasma level: 0.9 μg/ml), and (4) skin warming plus meperidine (target plasma level: 0.9 μg/ ml). Volunteers were cooled with 4°C cold Ringer lactate infused over a central venous catheter (rate ≈ 2.4°C/hour core temperature drop). Shivering threshold was identified by an increase of oxygen consumption (+20% of baseline). Sedation was assessed with the Observer's Assessment of Alertness/ Sedation scale. Results Control shivering threshold was 35.5°C ± 0.2°C. Skin warming reduced the shivering threshold to 34.9°C ± 0.5°C (p = 0.01). Meperidine reduced the shivering threshold to 34.2°C ± 0.3°C (p < 0.01). The combination of meperidine and skin warming reduced the shivering threshold to 33.8°C ± 0.2°C (p < 0.01). There were no synergistic or antagonistic effects of meperidine and skin warming (p = 0.59). Only very mild sedation occurred on meperidine days. Conclusion A combination of meperidine and skin surface warming reduced the shivering threshold to 33.8°C ± 0.2°C via an additive interaction and produced only very mild sedation and no respiratory toxicity.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 2013
Purpose Perioperative hypothermia is still a common occurrence, and it can be difficult to measur... more Purpose Perioperative hypothermia is still a common occurrence, and it can be difficult to measure a patient's core temperature accurately, especially during regional anesthesia, with placement of a laryngeal mask airway device, or postoperatively. We evaluated a new disposable double-sensor thermometer and compared the resulting temperatures with those of a distal esophageal thermometer and a bladder thermometer in patients undergoing general and regional anesthesia, respectively. Furthermore, we compared the accuracy of the thermometer between regional and general anesthesia, since forehead microcirculation might differ between the two types of anesthesia. Methods We assessed core temperature in 36 general anesthesia patients and 20 patients having regional anesthesia for orthopedic surgery. The temperatures obtained using the double-sensor thermometer were compared with those obtained with the distal esophageal
Background. Accurate measurement of core temperature is a standard component of perioperative and... more Background. Accurate measurement of core temperature is a standard component of perioperative and intensive care patient management. However, core temperature measurements are difficult to obtain in awake patients. A new non-invasive thermometer has been developed, combining two sensors separated by a known thermal resistance ('double-sensor' thermometer). We thus evaluated the accuracy of the double-sensor thermometer compared with a distal oesophageal thermometer to determine if the double-sensor thermometer is a suitable substitute. Methods. In perioperative and intensive care patient populations (n=68 total), double-sensor measurements were compared with measurements from a distal oesophageal thermometer using Bland-Altman analysis and Lin's concordance correlation coefficient (CCC). Results. Overall, 1287 measurement pairs were obtained at 5 min intervals. Ninety-eight per cent of all double-sensor values were within +0.58C of oesophageal temperature. The mean bias between the methods was 20.088C; the limits of agreement were 20.668C to 0.508C. Sensitivity and specificity for detection of fever were 0.86 and 0.97, respectively. Sensitivity and specificity for detection of hypothermia were 0.77 and 0.93, respectively. Lin's CCC was 0.93. Conclusions. The new double-sensor thermometer is sufficiently accurate to be considered an alternative to distal oesophageal core temperature measurement, and may be particularly useful in patients undergoing regional anaesthesia.
Background The perioperative period is characterized by an intense inflammatory response. Periope... more Background The perioperative period is characterized by an intense inflammatory response. Perioperative inflammation promotes postoperative morbidity and increases mortality. Blunting the inflammatory response to surgical trauma might thus improve perioperative outcomes. We are studying three interventions that potentially modulate perioperative inflammation: corticosteroids, tight glucose control, and light anesthesia. Methods/Design The DeLiT Trial is a factorial randomized single-center trial of dexamethasone vs placebo, intraoperative tight vs. conventional glucose control, and light vs deep anesthesia in patients undergoing major non-cardiac surgery. Anesthetic depth will be estimated with Bispectral Index (BIS) monitoring (Aspect medical, Newton, MA). The primary outcome is a composite of major postoperative morbidity including myocardial infarction, stroke, sepsis, and 30-day mortality. C-reactive protein, a measure of the inflammatory response, will be evaluated as a seconda...
Study Objective: To evaluate the postoperative hemodynamic and thermoregulatory consequences of i... more Study Objective: To evaluate the postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia. Design: Prospective, randomized clinical trial. Setting: Operating room and postanesthesia care unit of a university hospital. Patients: 74 healthy, ASA status I, II, and III patients (average age 58 yrs) undergoing elective colon surgery. Interventions: Patients were randomly assigned to be kept normothermic or =Z.YC hypothermic during surgery. Anesthesia was maintained with isoflurane, nitrous oxide, and fentanyl. Postoperatively, surgical pain was treated with patient-controlled analgesia (PCA) opioid. Measurements and Main Results: An observer blinded to group assignment and core temperatures evaluated shivering, thermal comfort, surgical pain, heart rates (HRs), and blood p ressures (BPS) during the first six postoperative hours. Morphometric characteristics, oxygen saturation, fluid balance, PCA-administered opioid, and visual analog pain scores were comparable in the two groups. Hypothermic patients felt uncomfortably cold during recovery, and their postoperative core temperatures remained significantly less than in the normothermic patients for more than four hours. Peripheral vasoconstriction and shivering were common in the hypothermic patients but rare in those kept normothermic. HRs and BPS were comparable in the two groups. Conclusions: These data confirm that the effects of intraoperative hypothermia on postoperative HR and BP are modest in relatively young, generally healthy patients. In contrast, intraoperative hypothermia caused substantial postoperative thermal discomfort, and full recovery from hypothermia required many hours. Delayed return to core normothermia apparently resulted largely from postoperative thermoregulatory impairment.
Background Patients may require perioperative cooling for a variety of reasons including treatmen... more Background Patients may require perioperative cooling for a variety of reasons including treatment of a malignant hyperthermia crisis and induction of therapeutic hypothermia for neurosurgery. The authors compared heat transfer and core cooling rates with five cooling methods. Methods Six healthy volunteers were anesthetized with desflurane and nitrous oxide. The cooling methods were 1) circulating water (5 degrees C, full-length mattress and cover), 2) forced air (10 degrees C, full-length cover), 3) gastric lavage (500 ml iced water every 10 min), 4) bladder lavage (300 ml iced Ringer's solution every 10 min), and 5) ice-water immersion. Each method was applied for 40 min or until the volunteers' core temperatures approached 34 degrees C. The volunteers were rewarmed to normothermia between treatments. Core cooling rates were evaluated using linear regression. Results The first volunteer developed abdominal cramping and diarrhea after gastric lavage. Consequently, the tech...
Background Core hypothermia after induction of general anesthesia results from an internal core-t... more Background Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution. Methods Six minimally clothed male volunteers in an approximately 22 degrees C environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and...
Background Forced-air warming is sometimes unable to maintain perioperative normothermia. Therefo... more Background Forced-air warming is sometimes unable to maintain perioperative normothermia. Therefore, the authors compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34 degrees C. The volunteers were subsequently warmed for 2.5 h with either a circulating-water garment or a forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and "deep" hand and foot thermometers. Results Heat production (approximately 60 kcal/h) and loss (approximately 45 kcal/h) were similar with each treatment befor...
Background:Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) a... more Background:Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) and myocardial injury, but what blood pressures are unsafe is unclear. The authors evaluated the association between the intraoperative mean arterial pressure (MAP) and the risk of AKI and myocardial injury.Methods:The authors obtained perioperative data for 33,330 noncardiac surgeries at the Cleveland Clinic, Ohio. The authors evaluated the association between intraoperative MAP from less than 55 to 75 mmHg and postoperative AKI and myocardial injury to determine the threshold of MAP where risk is increased. The authors then evaluated the association between the duration below this threshold and their outcomes adjusting for potential confounding variables.Results:AKI and myocardial injury developed in 2,478 (7.4%) and 770 (2.3%) surgeries, respectively. The MAP threshold where the risk for both outcomes increased was less than 55 mmHg. Compared with never developing a MAP less than 55 mm...
We compared changes in core temperature and systemic heat balance with a new negative pressure/wa... more We compared changes in core temperature and systemic heat balance with a new negative pressure/warming device (Vital Heat) that uses negative pressure combined with heat to facilitate warming in vasoconstricted postoperative patients to those resulting from passive insulation or forced air. Seven healthy volunteers were anesthetized and cooled to a tympanic membrane temperature near 34°C. Anesthesia was discontinued and shivering was prevented by using meperidine. The vasoconstricted volunteers were rewarmed for 2 h using three randomly assigned methods: 1) Vital Heat plus cotton blanket; 2) one layer of cotton blanket; 3) forced-air warming. Thermal flux was recorded from 15 skin-surface sites; metabolic heat production was estimated from total body oxygen consumption. Metabolic heat production remained
Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effec... more Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effects are unknown. We tested the hypothesis that dantrolene reduces the threshold (triggering core temperature) and gain (incremental increase) of shivering. With IRB approval and informed consent, healthy volunteers were evaluated on two random days: control and dantrolene (≈2.5 mg/kg plus a continuous infusion). In study 1, 9 men were warmed until sweating was provoked and then cooled until arterio-venous shunt constriction and shivering occurred. Sweating was quantified on the chest using a ventilated capsule. Absolute right middle fingertip blood flow was quantified using venousocclusion volume plethysmography. A sustained increase in oxygen consumption identified the shivering threshold. In study 2, 9 men were given cold Ringer's solution IV to reduce core temperature ≈2°C/h. Cooling was stopped when shivering intensity no longer increased with further core cooling. The gain of shivering was the slope of oxygen consumption vs. core temperature regression. In Study
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Papers by Andrea Kurz