scholarly journals Efficacy of forced-air and inhalation rewarming by using a human model for severe hypothermia

1997 ◽  
Vol 83 (5) ◽  
pp. 1635-1640 ◽  
Author(s):  
M. S. L. Goheen ◽  
M. B. Ducharme ◽  
G. P. Kenny ◽  
C. E. Johnston ◽  
John Frim ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Core Temperature ◽  
Cumulative Dose ◽  
Thermal Model ◽  
Human Model ◽  
The Core ◽  
Severe Hypothermia ◽  
Forced Air Warming ◽  
Forced Air

Goheen, M. S. L., M. B. Ducharme, G. P. Kenny, C. E. Johnston, John Frim, Gerald K. Bristow, and Gordon G. Giesbrecht.Efficacy of forced-air and inhalation rewarming by using a human model for severe hypothermia. J. Appl. Physiol. 83(5): 1635–1640, 1997.—We recently developed a nonshivering human model for severe hypothermia by using meperidine to inhibit shivering in mildly hypothermic subjects. This thermal model was used to evaluate warming techniques. On three occasions, eight subjects were immersed for ∼25 min in 9°C water. Meperidine (1.5 mg/kg) was injected before the subjects exited the water. Subjects were then removed, insulated, and rewarmed in an ambient temperature of −20°C with either 1) spontaneous rewarming (control), 2) inhalation rewarming with saturated air at ∼43°C, or 3) forced-air warming. Additional meperidine (to a maximum cumulative dose of 2.5 mg/kg) was given to maintain shivering inhibition. The core temperature afterdrop was 30–40% less during forced-air warming (0.9°C) than during control (1.4°C) and inhalation rewarming (1.2°C) ( P< 0.05). Rewarming rate was 6- to 10-fold greater during forced-air warming (2.40°C/h) than during control (0.41°C/h) and inhalation rewarming (0.23°C/h) ( P< 0.05). In nonshivering hypothermic subjects, forced-air warming provided a rewarming advantage, but inhalation rewarming did not.

Efficacy of Two Methods for Reducing Postbypass Afterdrop

2000 ◽  
Vol 92 (2) ◽  
pp. 447-447 ◽  
Author(s):  
Angela Rajek ◽  
Rainer Lenhardt ◽  
Daniel I. Sessler ◽  
Gabriele Brunner ◽  
Markus Haisjackl ◽  
...  
Keyword(s):  
Sodium Nitroprusside ◽  
Core Temperature ◽  
Heat Content ◽  
Tissue Temperature ◽  
Control Group ◽  
Peripheral Tissues ◽  
The Core ◽  
Forced Air Warming ◽  
Forced Air ◽  
Body Heat

Background Afterdrop, defined as the precipitous reduction in core temperature after cardiopulmonary bypass, results from redistribution of body heat to inadequately warmed peripheral tissues. The authors tested two methods of ameliorating afterdrop: (1) forced-air warming of peripheral tissues and (2) nitroprusside-induced vasodilation. Methods Patients were cooled during cardiopulmonary bypass to approximately 32 degrees C and subsequently rewarmed to a nasopharyngeal temperature near 37 degrees C and a rectal temperature near 36 degrees C. Patients in the forced-air protocol (n = 20) were assigned randomly to forced-air warming or passive insulation on the legs. Active heating started with rewarming while undergoing bypass and was continued for the remainder of surgery. Patients in the nitroprusside protocol (n = 30) were assigned randomly to either a control group or sodium nitroprusside administration. Pump flow during rewarming was maintained at 2.5 l x m(-2) x min(-1) in the control patients and at 3.0 l x m(-2) x min(-1) in those assigned to sodium nitroprusside. Sodium nitroprusside was titrated to maintain a mean arterial pressure near 60 mm Hg. In all cases, a nasopharyngeal probe evaluated core (trunk and head) temperature and heat content. Peripheral compartment (arm and leg) temperature and heat content were estimated using fourth-order regressions and integration over volume from 18 intramuscular needle thermocouples, nine skin temperatures, and "deep" hand and foot temperature. Results In patients warmed with forced air, peripheral tissue temperature was higher at the end of warming and remained higher until the end of surgery. The core temperature afterdrop was reduced from 1.2+/-0.2 degrees C to 0.5+/-0.2 degrees C by forced-air warming. The duration of afterdrop also was reduced, from 50+/-11 to 27+/-14 min. In the nitroprusside group, a rectal temperature of 36 degrees C was reached after 30+/-7 min of rewarming. This was only slightly faster than the 40+/-13 min necessary in the control group. The afterdrop was 0.8+/-0.3 degrees C with nitroprusside and lasted 34+/-10 min which was similar to the 1.1+/-0.3 degrees C afterdrop that lasted 44+/-13 min in the control group. Conclusions Cutaneous warming reduced the core temperature afterdrop by 60%. However, heat-balance data indicate that this reduction resulted primarily because forced-air heating prevented the typical decrease in body heat content after discontinuation of bypass, rather than by reducing redistribution. Nitroprusside administration slightly increased peripheral tissue temperature and heat content at the end of rewarming. However, the core-to-peripheral temperature gradient was low in both groups. Consequently, there was little redistribution in either case.

Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature

2018 ◽  
Vol 128 (5) ◽  
pp. 903-911 ◽  
Author(s):  
Lijian Pei ◽  
Yuguang Huang ◽  
Yiyao Xu ◽  
Yongchang Zheng ◽  
Xinting Sang ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Temperature Change ◽  
Core Temperature ◽  
Negative Slope ◽  
Anesthesia Induction ◽  
Temperature Changes ◽  
Ambient Temperatures ◽  
Forced Air Warming ◽  
Factorial Trial ◽  
Forced Air

Abstract Background The effect of ambient temperature, with and without active warming, on intraoperative core temperature remains poorly characterized. The authors determined the effect of ambient temperature on core temperature changes with and without forced-air warming. Methods In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was core temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient temperature, warming method, and their interaction. Results A 1°C increase in ambient temperature attenuated the negative slope of core temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °Ccore/(h.°Cambient) (P &lt; 0.001), for patients who received passive insulation, but not for those warmed with forced-air (–0.01 [98.3% CI, –0.03 to 0.01] °Ccore/[h.°Cambient]; P = 0.40). Final core temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P &lt; 0.01) per degree increase in ambient temperature with passive insulation, but was unaffected by ambient temperature during forced-air warming (0.02 [98.3% CI, –0.04 to 0.09] °Ccore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, core temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients. Conclusions Ambient intraoperative temperature has a negligible effect on core temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient temperature can thus be set to comfortable levels for staff in patients who are actively warmed.

scholarly journals Comparison of Three Warming Devices for the Prevention of Core Hypothermia and Post-Anaesthesia Shivering

2008 ◽  
Vol 36 (5) ◽  
pp. 923-931 ◽  
Author(s):  
CH Ihn ◽  
JD Joo ◽  
HS Chung ◽  
JW Choi ◽  
DW Kim ◽  
...  
Keyword(s):  
Core Temperature ◽  
Total Abdominal Hysterectomy ◽  
Abdominal Hysterectomy ◽  
Upper Body ◽  
Double Blind Study ◽  
Double Blind ◽  
Circulating Water ◽  
Surgical Access ◽  
Forced Air Warming ◽  
Forced Air

The efficacy of forced air warming with a surgical access blanket in preventing a decrease in core temperature during anaesthesia and post-anaesthesia shivering (PAS) was compared with two widely used interventions comprising forced air warming combined with an upper body blanket, and a circulating water mattress, in a prospective, randomized double-blind study. A total of 90 patients undergoing total abdominal hysterectomy were studied, 30 in each group. Core temperature was measured 15, 30, 45, 60, 90 and 120 min after induction of anaesthesia. PAS was evaluated every 5 min after emergence from anaesthesia over a period of 1 h. Core temperature fell in all three groups compared with the baseline, but forced air warming using a surgical access blanket was more effective than the other warming methods in ameliorating the temperature decrease. The surgical access blanket was also superior to the circulating water mattress in reducing PAS.

Forced-air warming is no more effective than conventional methods for raising postoperative core temperature after cardiac surgery

1997 ◽  
Vol 11 (6) ◽  
pp. 708-711 ◽  
Author(s):  
Frank J. Villamaria ◽  
Clinton E. Baisden ◽  
Argye Hillis ◽  
M.Hasan Rajab ◽  
Phillip A. Rinaldi
Keyword(s):  
Cardiac Surgery ◽  
Core Temperature ◽  
Forced Air Warming ◽  
Conventional Methods ◽  
Forced Air

Body Morphology and the Speed of Cutaneous Rewarming

2001 ◽  
Vol 95 (1) ◽  
pp. 18-21 ◽  
Author(s):  
Peter Szmuk ◽  
Mary F. Rabb ◽  
James E. Baumgartner ◽  
James M. Berry ◽  
Andrew M. Sessler ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Surface Area ◽  
Body Mass ◽  
Core Temperature ◽  
Infants And Children ◽  
Metabolic Heat ◽  
Duration Of Surgery ◽  
Forced Air ◽  
Dural Opening ◽  
Full Body

Background Infants and children cool quickly because their surface area (and therefore heat loss) is large compared with their metabolic rate, which is mostly a function of body mass. Rewarming rate is a function of cutaneous heat transfer plus metabolic heat production divided by body mass. Therefore, the authors tested the hypothesis that the rate of forced-air rewarming is inversely related to body size. Methods Isoflurane, nitrous oxide, and fentanyl anesthesia were administered to infants, children, and adults scheduled to undergo hypothermic neurosurgery. All fluids were warmed to 37 degrees C and ambient temperature was maintained near 21 degrees C. Patients were covered with a full-body, forced-air cover of the appropriate size. The heater was set to low or ambient temperature to reduce core temperature to 34 degrees C in time for dural opening. Blower temperature was then adjusted to maintain core temperature at 34 degrees C for 1 h. Subsequently, the forced-air heater temperature was set to high (approximately 43 degrees C). Rewarming continued for the duration of surgery and postoperatively until core temperature exceeded 36.5 degrees C. The rewarming rate in individual patients was determined by linear regression. Results Rewarming rates were highly linear over time, with correlations coefficients (r2) averaging 0.98+/-0.02. There was a linear relation between rewarming rate (degrees C/h) and body surface area (BSA; m2): Rate (degrees C/h) = -0.59 x BSA (m2) + 1.9, r2 = 0.74. Halving BSA thus nearly doubled the rewarming rate. Conclusions Infants and children rewarm two to three times faster than adults, thus rapidly recovering from accidental or therapeutic hypothermia.

scholarly journals Effects of Combined Warmed Preoperative Forced-air and Warmed Perioperative Intravenous Fluids on Maternal Temperature During Cesarean Section: a prospective, randomized, controlled clinical trial

2020 ◽  
Author(s):  
tingting Ni ◽  
Zhen-feng Zhou ◽  
Bo He ◽  
Qing-he Zhou
Keyword(s):  
Clinical Trial ◽  
Cesarean Section ◽  
Thermal Comfort ◽  
Core Temperature ◽  
Intervention Group ◽  
Control Group ◽  
Intravenous Fluids ◽  
Cesarean Sections ◽  
The Core ◽  
Forced Air

Abstract Background: Preventing the frequent perioperative hypothermia incidents that occur during elective caesarean deliveries would be beneficial. This trial aimed at evaluating the effect of preoperative forced-air warming alongside perioperative intravenous fluid warming in women undergoing cesarean sections under spinal anesthesia.Methods: We randomly allocated135 women undergoing elective cesarean deliveries to either the intervention group (preoperative forced-air and intravenous fluid warmings, n = 69) or the control group (no active warming, n = 66). The primary outcome measure was the change from the core baseline temperature to that at the end of the procedure. Secondary outcomes included thermal comfort scores, the incidences of shivering and hypothermia (<36℃), the core temperature on arrival at the post-anesthesia care unit, neonatal axillary temperature at birth, and Apgar scores.Results: Two-way repeated measures ANOVA revealed significantly different core temperature changes (from the pre-spinal temperature to that at the end of the procedure) between groups (F = 13.022, P <0.001). The thermal comfort scores were also higher in the intervention group than in the control group (F = 9.847, P = 0.002). The overall incidence of perioperative hypothermia was significantly lower in the intervention group than in the control group (20.6% vs. 51.6%, P <0.0001).Conclusions: Warming preoperative forced-air and perioperative intravenous fluids may prevent maternal hypothermia, reduce maternal shivering, and improve maternal thermal comfort for patients undergoing cesarean sections under spinal anesthesia.Trial registration: The study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800019117) on October26, 2018. Keywords: Cesarean section, Spinal anesthesia, Warming

Influence of Thermoregulatory Vasomotion and Ambient Temperature Variation on the Accuracy of Core-temperature Estimates by Cutaneous Liquid-crystal Thermometers

1997 ◽  
Vol 86 (3) ◽  
pp. 603-612 ◽  
Author(s):  
Takehiko Ikeda ◽  
Daniel I. Sessler ◽  
Danielle Marder ◽  
Junyu Xiong
Keyword(s):  
Liquid Crystal ◽  
Ambient Temperature ◽  
Skin Temperature ◽  
Temperature Variation ◽  
Core Temperature ◽  
Temperature Difference ◽  
Capillary Flow ◽  
The Core ◽  
Neck Temperature ◽  
Body Heat

Background Recently, liquid crystal skin-surface thermometers have become popular for intraoperative temperature monitoring. Three situations during which cutaneous liquid-crystal thermometry may poorly estimate core temperature were monitored: (1) anesthetic induction with consequent core-to-peripheral redistribution of body heat, (2) thermoregulatory vasomotion associated with sweating (precapillary dilation) and shivering (minimal capillary flow), and (3) ambient temperature variation over the clinical range from 18-26 degrees C. Methods The core-to-forehead and core-to-neck temperature difference was measured using liquid-crystal thermometers having an approximately 2 degrees C offset. Differences exceeding 0.5 degree C (a 1 degree C) temperature range) were a priori deemed potentially clinically important. Seven volunteers participated in each protocol. First, core-to-peripheral redistribution of body heat was produced by inducing propofol/desflurane anesthesia; anesthesia was then maintained for 1 h with desflurane. Second, vasodilation was produced by warming unanesthetized volunteers sufficiently to produce sweating; intense vasoconstriction was similarly produced by cooling the volunteers sufficiently to produce shivering. Third, a canopy was positioned to enclose the head, neck, and upper chest of unanesthetized volunteers. Air within the canopy was randomly set to 18, 20, 22, 24, and 26 degrees C. Results Redistribution of body heat accompanying induction of anesthesia had little effect on the core-to-forehead skin temperature difference. However, the core-to-neck skin temperature gradient decreased approximately 0.6 degree C in the hour after induction of anesthesia. Vasomotion associated with shivering and mild sweating altered the core-to-skin temperature difference only a few tenths of a degree centigrade. The absolute value of the core-to-forehead temperature difference exceeded 0.5 degree C during approximately 35% of the measurements, but the difference rarely exceeded 1 degree C. The core-to-neck temperature difference typically exceeded 0.5 degree C and frequently exceeded 1 degree C. Each 1 degree C increase in ambient temperature decreased the core-to-fore-head and core-to-neck skin temperature differences by less than 0.2 degree C. Conclusions Forehead skin temperatures were better than neck skin temperature at estimating core temperature. Core-to-neck temperature differences frequently exceeded 1 degree C (a 2 degrees C range), whereas two thirds of the core-to-forehead differences were within 0.5 degree C. The core-to-skin temperature differences were, however, only slightly altered by inducing anesthesia, vasomotor action, and typical intraoperative changes in ambient temperature.

Thermoregulatory Vasoconstriction Does Not Impede Core Warming during Cutaneous Heating

1996 ◽  
Vol 85 (2) ◽  
pp. 281-288 ◽  
Author(s):  
David Clough ◽  
Andrea Kurz ◽  
Daniel I. Sessler ◽  
Richard Christensen ◽  
Junyu Xiong
Keyword(s):  
Heat Transfer ◽  
Core Temperature ◽  
Heat Content ◽  
Healthy Male ◽  
Core Flow ◽  
Arteriovenous Shunts ◽  
Forced Air Warming ◽  
Core Tissue ◽  
Forced Air ◽  
Skin Temperatures

Background Although forced-air warming rapidly increases intraoperative core temperatures, it is reportedly ineffective postoperatively. A major difference between these two periods is that arteriovenous shunts are usually dilated during surgery, whereas vasoconstriction is uniform in hypothermic postoperative patients. Vasoconstriction may decrease efficacy of warming because its major physiologic purposes are to reduce cutaneous heat transfer and restrict heat transfer between the two thermal compartments. Accordingly, we tested the hypothesis that thermoregulatory vasoconstriction decreases cutaneous transfer of applied heat and restricts peripheral-to-core flow of heat, thereby delaying and reducing the increase in core temperature. Methods Eight healthy male volunteers anesthetized with propofol and isoflurane were studied. Volunteers were allowed to cool passively until core temperature reached 33 degrees C. On one randomly assigned day, the isoflurane concentration was reduced, to provoke thermoregulatory arteriovenous shunt vasoconstriction; on the other study day, a sufficient amount of isoflurane was administered to prevent vasoconstriction. On each day, forced-air warming was then applied for 2 h. Peripheral (arm and leg) tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. Core (trunk and head) heat content was determined from core temperature, assuming a uniform compartmental distribution. Time-dependent changes in peripheral and core tissue heat contents were evaluated using linear regression. Differences between the vasoconstriction and vasodilation study days, and between the peripheral and core compartments, were evaluated using two-tailed, paired t tests. Data are presented as means +/-SD; P &lt; 0.01 was considered statistically significant. Results Cutaneous heat transfer was similar during vasoconstriction and vasodilation. Forced-air warming increased peripheral tissue heat content comparably when the volunteers were vasodilated and vasoconstricted: 48 +/- 7 versus 53 +/- 10 kcal/h. Core compartment tissue heat content increased similarly when the volunteers were vasodilated and vasoconstricted: 51 +/- 8 versus 44 +/- 11 kcal/h. Combining the two study days, the increase in peripheral and core heat contents did not differ significantly: 51 +/- 8 versus 48 +/- 10 kcal/h, respectively. Core temperature increased at essentially the same rate when the volunteers remained vasodilated (1.3 degrees C/h) as when they were vasoconstricted (1.2 degrees C/h). Conclusions The authors failed to confirm their hypothesis that thermoregulatory vasoconstriction decreases cutaneous transfer of applied heat and restricts peripheral-to-core flow of heat in anesthetized subjects. The reported difference between intraoperative and postoperative rewarming efficacy may result from nonthermoregulatory anesthetic-induced vasodilation.

Sign in / Sign up

Export Citation Format

Share Document