Should we rely on nasopharyngeal temperature during cardiopulmonary bypass?

Perfusion ◽  
2002 ◽  
Vol 17 (2) ◽  
pp. 145-151 ◽  
Author(s):  
R Ian Johnson ◽  
Mark A Fox ◽  
Antony Grayson ◽  
Mark Jackson ◽  
Brian M Fabri
Keyword(s):  
Cardiopulmonary Bypass ◽  
Temperature Measurement ◽  
Temperature Control ◽  
Controlled Study ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Normothermic Group ◽  
Control Limits ◽  
Arterial Blood Temperature ◽  
Hypothermic Group

A potential morbidity of incomplete re-warming following hypothermic cardiopulmonary bypass (CPB) is cardiac arrest. In contrast, attempts to fully re-warm the patient can lead to cerebral hyperthermia. Similarly, rigid adherence to 37.0°C during normothermic CPB may also cause cerebral overheating. The literature demonstrates scant information concerning the actual temperatures measured, the sites of temperature measurement and the detailed thermal strategies employed during CPB. A prospective, randomized, controlled study was undertaken to investigate the ability to manage perfusion temperature control in a group of hypothermic patients (28°C) and a group of normothermic patients (37°C). Eighty patients presenting for first-time, elective coronary artery bypass graft surgery (CABG) were randomly allocated to the hypothermic and normothermic groups. All surgery was performed by one surgeon and the anaesthesia managed by one anaesthetist. Temperature measurements were made at the nasopharyngeal (NP) site, as well as in the arterial line of the CPB circuit. The hypothermic group had the arterial blood temperature lowered to 25.0°C to maintain the NP temperature at 28.0-28.5°C. During re-warming, the arterial blood was raised to 38.0°C. Meanwhile, in the normothermic group, the arterial blood temperature was raised to a maximum of 37.0°C to maintain NP temperature at 36.5-37.0°C. Despite strict guidelines, some patients transgressed the temperature control limits. Two patients in the hypothermic group failed to reach an NP temperature of 28.5°C. Twenty-six patients were managed entirely within the control limits. During re-warming in both groups, control of both arterial and NP temperature was well managed with only 25% patients breaching the respective upper control limits. During the re-warming phases of CPB, we were unable to make any correlation between NP temperature and arterial blood temperature, using body weight or body mass index as predictors. Based on the results obtained, we recommend that strict criteria should be implemented for the management of temperature during CPB, in conjunction with more emphasis being placed on monitoring arterial blood temperature as a marker of potential cerebral hyperthermia. We should, therefore, not rely on NP temperature measurement alone during CPB.

Comparison of Normothermic Cardiopulmonary Bypass with Conventional Hypothermic Bypass

1997 ◽  
Vol 5 (4) ◽  
pp. 199-202
Author(s):  
Sandeep Chauhan ◽  
Gaurishankar Ramesh ◽  
Nita Saxena ◽  
Shiv Kumar Choudhary ◽  
Lokendra Kumar ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Blood Loss ◽  
Heart Surgery ◽  
Sinus Node ◽  
Open Heart Surgery ◽  
Postoperative Blood Loss ◽  
Arterial Blood ◽  
Early Return ◽  
Normothermic Group ◽  
Hypothermic Group

In a prospective randomized study from October to December 1996 at the All India Institute of Medical Sciences, we compared normothermic cardiopulmonary bypass with conventional hypothermic bypass. Sixty patients undergoing open-heart surgery for valvular heart disorders were assigned to undergo either normothermic bypass (35°C to 37°C, n = 30) or moderate hypothermic bypass (28°C, n = 30). Bypass time, pump flow, urine output, need for vasopressors, arterial blood gases on bypass, duration of cardioplegia, need for defibrillation, postoperative blood loss, rewarming time to a peripheral (toe) temperature above 35°C, awakening time, and neurologic outcome were studied. Mean bypass time in the normothermic patients (67.33 ± 23.5 minutes) was 23% less (p < 0.05) than in the hypothermic group (89.6 ± 49.26 minutes). Higher flows were required initially in the normothermic group due to low systemic vascular resistance. Early return of sinus node electrical activity in patients (70%) in the normothermic group required more frequent use of topical ice slush and cardioplegia administration. Postoperative blood loss was similar in both groups but fluid and blood requirements in the normothermic group (514 ± 220 mL·m−2) was significantly less (p < 0.05) than in the hypothermic group (722.3 ± 383 mLm−2). Normothermic patients rewarmed earlier (4.25 ± 1.79 hours) to peripheral (toe) temperatures above 35 °C and awoke earlier compared with the hypothermic group, which took a mean time of 6.1 ± 2.3 hours to rewarm. We concluded that normothermic bypass is more physiologic and significantly reduces bypass time while avoiding the deleterious effects of hypothermia.

Rectal temperature measurement results in artifactual evidence of selective brain cooling

2001 ◽  
Vol 281 (1) ◽  
pp. R108-R114 ◽  
Author(s):  
Shane K. Maloney ◽  
Andrea Fuller ◽  
Graham Mitchell ◽  
Duncan Mitchell
Keyword(s):  
Rectal Temperature ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Arterial Blood ◽  
The Status ◽  
Conscious Sheep ◽  
Surrogate Measures ◽  
Arterial Blood Temperature

Selective brain cooling (SBC) is defined as a brain temperature cooler than the temperature of arterial blood from the trunk. Surrogate measures of arterial blood temperature have been used in many published studies on SBC. The use of a surrogate for arterial blood temperature has the potential to confound proper identification of SBC. We have measured brain, carotid blood, and rectal temperatures in conscious sheep exposed to 40, 22, and 5°C. Rectal temperature was consistently higher than arterial blood temperature. Brain temperature was consistently cooler than rectal temperature during all exposures. Brain temperature only fell below carotid blood temperature during the final few hours of 40°C exposure and not at all during the 5°C exposure. Consequently, using rectal temperature as a surrogate for arterial blood temperature does not provide a reliable indication of the status of the SBC effector. We also show that rapid suppression of SBC can result if the animals are disturbed.

Influence of skin temperature on central thermoregulatory control of leg blood flow

1981 ◽  
Vol 50 (5) ◽  
pp. 974-978 ◽  
Author(s):  
D. W. Proppe
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Skin Temperature ◽  
Major Influence ◽  
Papio Anubis ◽  
Vascular Conductance ◽  
Leg Blood Flow ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Arterial Blood Temperature

This study examined the influence of elevated skin temperature (Tsk) on the central thermoregulatory control of leg blood flow in five unanesthetized, chronically instrumented, resting baboons (Papio anubis and P. cynocephalus). In each experiment, mean iliac blood flow (MIBF), mean arterial blood pressure, arterial blood temperature (Tbl), and Tsk were measured, and iliac vascular conductance (IVC) was calculated. A heat exchanger was incorporated into a chronic arteriovenous femoral shunt to control Tbl. The protocol consisted of raising Tbl approximately 2.6 degrees C in thermoneutral environment (cool Tsk) an then again after Tsk had been elevated by environmental heating. A major influence of raising Tsk was the lowering of threshold Tbl at which the rise in MIBF and IVC commenced. This threshold Tbl was lowered at least 0.8 degrees C on the average. Also, over the whole range of Tbl studied (37.0-39.6 degrees C), MIBF and IVC were higher at high Tsk than at cool Tsk. Thus an elevation of Tsk significantly influences the control of skin blood flow by central thermoreceptors.

Thermal Modeling of the Normal Woman’s Breast

1984 ◽  
Vol 106 (2) ◽  
pp. 123-130 ◽  
Author(s):  
M. M. Osman ◽  
E. M. Afify
Keyword(s):  
Venous Blood ◽  
Tissue Perfusion ◽  
3 Dimensional ◽  
Metabolic Heat ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Dimensional Finite Element ◽  
Element Technique ◽  
Arterial Blood Temperature ◽  
Good Agreement

A comprehensive thermal model of the normal woman’s breast is presented. The model is developed taking into consideration metabolic heat production, tissue perfusion with capillary blood, arterial and venous blood thermal interaction and change of arterial blood temperature with position. A series of computer programs are written using a 3-dimensional finite-element technique to evaluate the surface temperature distribution of the breast. Comparison between the results obtained for the model and those from thermograms of a woman’s breast are in good agreement.

Blood and brain temperatures of free-ranging black wildebeest in their natural environment

1994 ◽  
Vol 267 (6) ◽  
pp. R1528-R1536 ◽  
Author(s):  
C. Jessen ◽  
H. P. Laburn ◽  
M. H. Knight ◽  
G. Kuhnen ◽  
K. Goelst ◽  
...  
Keyword(s):  
Brain Temperature ◽  
Natural Habitat ◽  
Radiant Heat ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Data Loggers ◽  
Free Ranging ◽  
Arterial Blood Temperature

Using miniature data loggers, we measured the temperatures of carotid blood and brain in four wildebeest (Connochaetes gnou) every 2 min for 3 wk and every 5 min, in two of the animals, for a further 6 wk. The animals ranged freely in their natural habitat, in which there was no shelter. They were subject to intense radiant heat (maximum approximately 1,000 W/m2) during the day. Arterial blood temperature showed a circadian rhythm with low amplitude (< 1 degree C) and peaked in early evening. Brain temperature was usually within 0.2 degrees C of arterial blood temperature. Above a threshold between 38.8 and 39.2 degrees C, brain temperature tended to plateau so that the animals exhibited selective brain cooling. However, selective brain cooling sometimes was absent even when blood temperature was high and present when it was low. During helicopter chases, selective brain cooling was absent, even though brain temperature was near 42 degrees C. We believe that selective brain cooling is controlled by brain temperature but is modulated by sympathetic nervous system status. In particular, selective brain cooling may be abolished by high sympathetic activity even at high brain temperatures.

Cold or warm start of cardiopulmonary bypass- influence on microcirculatory blood flow

Perfusion ◽  
1994 ◽  
Vol 9 (1) ◽  
pp. 11-18 ◽  
Author(s):  
J. Boldt ◽  
Ch. Knothe ◽  
H. Hammermann ◽  
W.A. Stertmann ◽  
G. Hempelmann
Keyword(s):  
Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Cold Start ◽  
Laser Doppler ◽  
Microcirculatory Perfusion ◽  
Doppler Flowmetry ◽  
Warm Start ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Baseline Values

In a randomized study of 30 patients undergoing elective aortocoronary bypass grafting, either cold start of cardiopulmonary bypass (CPB) (prime: room temperature [approximately 20°C], n = 15) or normothermic start of CPB (prime: warmed up to the patients' blood temperature, n = 15) were performed. After warm start, CPB was continued using almost normothermia (lowest nasopharyngeal temperature: 35.8 ± 0.4°C), after cold start hypothermia was used (lowest nasopharyngeal temperature: 28.8 ± 0.2°C). Changes in microcirculatory perfusion were assessed by measuring skin capillary blood flow at the patient's forearm and forehead using laser Doppler technique. Laser Doppler flow (LDF) was continuously monitored before onset of CPB (=baseline values), 30 seconds, one, five, 10, 15 and 20 minutes after start of CPB. Mean arterial blood pressure (MAP) and systemic vascular resistance (SVR) were reduced by CPB in both groups, with the more pronounced reduction in the normothermic patients. Haemoglobin and plasma viscosity were without differences between the groups. The lowest blood temperature in the hypothermic patients was 21.0 ± 0.3°C, and the lowest rectal temperature in these patients was 29.0 ± 0.3°C (20 minutes after start of CPB). Forehead- and forearm-LDF increased significantly in both groups by start of CPB. In the hypothermic patients, this increase was significantly lower, and LDFs were already reduced below baseline values five to 10 minutes after onset of CPB (LDF-forehead -18%, LDF-forearm -72%). In the normothermic patients, LDFs remained elevated during the first 20 minutes after the beginning of bypass (LDF- forehead +38%; LDF-forearm +35%) and were significantly higher than baseline ' even after CPB (hypothermia: LDF-forehead -34%; LDF-forearm -31%). Except for the blood temperature, none of the measured haemodynamic and laboratory values could be related significantly to changes of LDFs (analyses of covariance). It is concluded that skin microcirculatory perfusion as assessed by laser Doppler flowmetry was less altered when using warm start and maintenance of perfusion than after cold start and hypothermic CPB. Whether this improvement in microperfusion after warm start of CPB takes place also in other (more vital) organs has to be elucidated in further studies.

scholarly journals The treatment of arterial blood temperature in bioheat transfer equation

1989 ◽  
Vol 5 (1) ◽  
pp. 67-74
Author(s):  
Hirokazu Kato ◽  
Masahiko Furukawa ◽  
Nobue Uchida ◽  
Toshifumi Kasai ◽  
Yasuhiko Fujita ◽  
...  
Keyword(s):  
Transfer Equation ◽  
Bioheat Transfer ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Arterial Blood Temperature ◽  
Bioheat Transfer Equation
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