Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature

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 before warming. The increases in heat transfer across anterior portions of the skin surface were similar with each warming system (approximately 65 kcal/h). Forced-air warming had no effect on posterior heat transfer, whereas circulating-water transferred 21+/-9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 degrees +/- 0.7 degrees C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4 degrees C/h faster than forced air. A substantial peripheral-to-core tissue temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer.

Download Full-text

Efficacy of Two Methods for Reducing Postbypass Afterdrop

Anesthesiology ◽

10.1097/00000542-200002000-00027 ◽

2000 ◽

Vol 92 (2) ◽

pp. 447-447 ◽

Cited By ~ 27

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.

Download Full-text

Thermoregulatory Vasoconstriction Does Not Impede Core Warming during Cutaneous Heating

Anesthesiology ◽

10.1097/00000542-199608000-00009 ◽

1996 ◽

Vol 85 (2) ◽

pp. 281-288 ◽

Cited By ~ 26

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 < 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.

Download Full-text

Comparison of the efficacy of a forced-air warming system and circulating-water mattress on core temperature and post-anesthesia shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia

Korean Journal of Anesthesiology ◽

10.4097/kjae.2014.66.5.352 ◽

2014 ◽

Vol 66 (5) ◽

pp. 352 ◽

Cited By ~ 15

Author(s):

Hye Young Kim ◽

Kyu Chang Lee ◽

Myeong Jong Lee ◽

Mi-Na Kim ◽

Ji-Sub Kim ◽

...

Keyword(s):

Total Knee Arthroplasty ◽

Elderly Patients ◽

Spinal Anesthesia ◽

Core Temperature ◽

Knee Arthroplasty ◽

Circulating Water ◽

Forced Air Warming ◽

Total Knee ◽

Forced Air

Download Full-text

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

Journal of International Medical Research ◽

10.1177/147323000803600508 ◽

2008 ◽

Vol 36 (5) ◽

pp. 923-931 ◽

Cited By ~ 14

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.

Download Full-text

Tissue Heat Content and Distribution during and after Cardiopulmonary Bypass at 31 [degree sign]C and 27 [degree sign]C

Anesthesiology ◽

10.1097/00000542-199806000-00015 ◽

1998 ◽

Vol 88 (6) ◽

pp. 1511-1518 ◽

Cited By ~ 46

Author(s):

Angela Rajek ◽

Rainer Lenhardt ◽

Daniel I. Sessler ◽

Andrea Kurz ◽

Gunther Laufer ◽

...

Keyword(s):

Cardiopulmonary Bypass ◽

Temperature Gradient ◽

Heat Content ◽

Peripheral Tissue ◽

Tissue Temperature ◽

Peripheral Compartment ◽

Peripheral Tissues ◽

The Core ◽

Total Body ◽

Body Heat

Background Afterdrop following cardiopulmonary bypass results from redistribution of body heat to inadequately warmed peripheral tissues. However, the distribution of heat between the thermal compartments and the extent to which core-to-peripheral redistribution contributes to post-bypass hypothermia remains unknown. Methods Patients were cooled during cardiopulmonary bypass to nasopharyngeal temperatures near 31 degrees C (n=8) or 27 degrees C (n=8) and subsequently rewarmed by the bypass heat exchanger to approximately 37.5 degrees C. 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 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. Results In the 31 degrees C group, the average peripheral tissue temperature decreased to 31.9+/-1.4 degrees C (means+/-SD) and subsequently increased to 34+/-1.4 degrees C at the end of bypass. The core-to-peripheral tissue temperature gradient was 3.5+/-1.8 degrees C at the end of rewarming, and the afterdrop was 1.5+/-0.4 degrees C. Total body heat content decreased 231+/-93 kcal. During pump rewarming, the peripheral heat content increased to 7+/-27 kcal below precooling values, whereas the core heat content increased to 94+/-33 kcal above precooling values. Body heat content at the end of rewarming was thus 87+/-42 kcal more than at the onset of cooling. In the 27 degrees C group, the average peripheral tissue temperature decreased to a minimum of 29.8 +/-1.7 degrees C and subsequently increased to 32.8+/-2.1 degrees C at the end of bypass. The core-to-peripheral tissue temperature gradient was 4.6+/-1.9 degrees C at the end of rewarming, and the afterdrop was 2.3+/-0.9 degrees C. Total body heat content decreased 419+/-49 kcal. During pump rewarming, core heat content increased to 66+/-23 kcal above precooling values, whereas peripheral heat content remained 70+/-42 kcal below precooling values. Body heat content at the end of rewarming was thus 4+/-52 kcal less than at the onset of cooling. Conclusions Peripheral tissues failed to fully rewarm by the end of bypass in the patients in the 27 degrees C group, and the afterdrop was 2.3+/-0.9 degrees C. Peripheral tissues rewarmed better in the patients in the 31 degrees C group, and the afterdrop was only 1.5+/-0.4 degrees C.

Download Full-text

Heat Transfer to Blood Vessels

Journal of Biomechanical Engineering ◽

10.1115/1.3138205 ◽

1980 ◽

Vol 102 (2) ◽

pp. 110-118 ◽

Cited By ~ 224

Author(s):

J. C. Chato

Keyword(s):

Heat Transfer ◽

Blood Vessels ◽

Internal Heat ◽

Absolute Magnitude ◽

Skin Surface ◽

Tissue Temperature ◽

Single Vessel ◽

Controlling Parameter ◽

Order Of Magnitude ◽

Linear Effects

Heat transfer to individual blood vessels has been investigated in three configurations: a single vessel, two vessels in counterflow, and a single vessel near the skin surface. For a single vessel the Graetz number is the controlling parameter. The arterioles, capillaries, and venules have very low Graetz numbers, Gz < 0.4, and act as perfect heat exchangers in which the blood quickly reaches the tissue temperature. The large arteries and veins with Graetz numbers over 103 have virtually no heat exchange with the tissue, and blood leaves them at near the entering temperature. Heat transfer between parallel vessels in counterflow is influenced most strongly by the relative distance of separation and by the mass transferred from the artery to the vein along the length. These two effects are of the same order of magnitude, whereas the film coefficients in the blood flow are of significant but lesser importance. The effect of a blood vessel on the temperature distribution of the skin directly above it and on the heat transfer to the environment increases with decreasing depth-to-radius ratio and decreasing Biot number based on radius. The absolute magnitude of these effects is independent of other linear effects, such as internal heat generation or a superimposed one-dimensional heat flux.

Download Full-text

Forced-Air Warming Maintains Intraoperative Normotherrnia Better Than Circulating-Water Mattresses

Anesthesia & Analgesia ◽

10.1213/00000539-199307000-00018 ◽

1993 ◽

Vol 77 (1) ◽

pp. 89???95 ◽

Cited By ~ 91

Author(s):

Andrea Kurz ◽

Martin Kurz ◽

Gerald Poeschl ◽

Barbara Faryniak ◽

Gerhard Redl ◽

...

Keyword(s):

Circulating Water ◽

Forced Air Warming ◽

Forced Air ◽

Better Than

Download Full-text

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

Journal of Applied Physiology ◽

10.1152/jappl.1997.83.5.1635 ◽

1997 ◽

Vol 83 (5) ◽

pp. 1635-1640 ◽

Cited By ~ 59

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.

Download Full-text