Effects of heat acclimation on atropine-impaired thermoregulation

The effects of saline or atropine injection (2 mg, im) on eccrine sweating and performance time in seven healthy male subjects were evaluated during treadmill walking (1.34 m X s-1) in a hot-dry environment (Ta = 49 degrees C, Tdp = 20.5 degrees C) before and after heat acclimation (HA). Mean skin temperature (Tsk), rectal temperature (Tre), and heart rate (HR) were continuously measured. Sweat loss from the skin (Msw) was calculated by changes in body weight. HA resulted in decreased (p less than 0.05) Tre (0.4 degrees C) and HR (17 b X min-1), and increased (p less than 0.05) Msw (16 g X m-2 X h-1) during the saline experiments. Pre-acclimation, Msw was reduced (p less than 0.01) 65% (151 g X m-2 X h-1) with atropine, which resulted in higher (p less than 0.01) Tre (0.4 degrees C) and Tsk (2.8 degrees C). HR was increased 48% (53 b X min-1) by atropine pre-acclimation (p less than 0.01). Post-acclimation, atropine reduced (p less than 0.01) Msw 33% (100 g X m-2 X h-1) and increased (p less than 0.01) HR 63% (62 b X min-1) compared to saline exposures. The change in Tre X min-1 (delta Tre/delta t) was lower (p less than 0.05) in atropine-injected subjects following heat acclimation, and their worktime was improved by an average of 23.5 min (p = 0.08). These data demonstrate that heat acclimation improves the endurance time of atropine-treated subjects in a hot-dry environment. This improvement was, in part, due to the potentiation of sweat gland activity enabling greater evaporative cooling for the same dose of atropine.     

The hydration and electrolyte maintenance properties of an experimental sports drink.

Seven highly trained subjects underwent exercise dehydration without fluid replacement (X), resulting in approximately 1.9% and approximately 3.5% body weight (fluid) losses at one and two hours, respectively. Subsequently, subjects underwent two identical exercise trials with isovolumetric fluid replacement of water (W) and an experimental formulation (Q). An anti-dehydration schedule was initiated prior to, and continued throughout the exercise, with W and Q supplied every 15 minutes at 16 degrees C in volumes related to each subject's fluid loss estimate derived from trial X. A rehydration schedule was maintained for two hours of recovery, with total fluid replacement equivalent to the body weight decrement due to fluid losses. In both W and Q trials, selected physiological indices of work performance were maintained closer to homeostatic levels during exercise, with a more rapid return to pre-exercise resting levels during recovery than during that trial X. Furthermore, W and Q were equally effective in preventing plasma volume changes during exercise and restoration to pre-exercise levels during recovery, as well as in preventing plasma osmolality disturbances during exercise and recovery, although minimal plasma electrolyte changes were associated with Q.     

Influence of a new vapor protective clothing layer on physical work tolerance times at 40 degrees C.

The purpose of the present study was to examine the influence of a new vapor protective clothing on physical work performance in a hot environment (40 degrees C and 25% relative humidity). Eleven unacclimatized males (28 +/- 6 years, 79 +/- 8 kg, 1.76 +/- 0.06 m) were assigned to exercise at either a light intermittent (L) (N = 6), or heavy continuous (H) (N = 5) metabolic rate. Group L alternated between 15 min of walking on a treadmill at 1.11 m.s-1 with a 0% grade and 15 min of rest. Group H walked continuously at 1.33 m.s-1 with a 3% grade. Subjects were tested wearing three clothing configurations: full nuclear, biological and chemical (NBC) protection (TOPP High) with the combat clothing worn under the NBC garment (TH + CC); full NBC protection without combat clothing (TH - CC); the new vapor protective clothing together with the NBC gloves, boots, and respirator (NPC). WTT was the time-period until rectal temperature (Tre) reached 39.3 degrees C, heart rate reached 95% maximum, dizziness or nausea precluded further exercise, or 3 h had elapsed. For group L, WTT was similar for TH + CC (113 +/- 12 min) and TH - CC (139 +/- 18 min). WTT was significantly increased for NPC where all subjects completed the 3 h in the climatic chamber. The rate of increase for Tre was significantly reduced for NPC (0.3 +/- 0.1 degree C.h-1) compared with both TH + CC (0.9 +/- 0.1 degree C.h-1) and TH - CC (0.8 +/- 0.2 degree C.h-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise thermoregulation in men after 6 hours of immersion

Rectal (Tre) and mean skin (Tsk) temperature, skin heat conductance (Ksk), heart rate, and total body sweat rate were measured in 6 men (20-35 years) during 70 min of supine leg exercise (Ta = 23.5 degrees C, rh = 40%) at 50% of their peak O2 uptake (VO2 peak); these data were taken after a 6-h control (C) period in air and after immersion to the neck (NI) in water (34.5 degrees C) for 6 h after overnight food and fluid restriction. After NI mean (+/- S.E.) water balance was -1,285 +/- 104 ml for the 6 h and plasma volume (delta Hb and Hct) decreased by 5.2%. End exercise heart rates after C (141 +/- 3 b X min-1) increased to 148 +/- 3 b X min-1 (p less than 0.05) after NI while Vo2 were both 2.2 L X min-1 Tre increased by 0.5 C degrees (p less than 0.05) between the end of NI and the start of exercise. During exercise following C and NI, delta Tre were +1.0 degrees C and +0.9 degrees C (NS), Ksk were 44 +/- 2 and 43 +/- 1 kcal X m-2 X hr-1 X degrees C-1 (NS), while sweat rates increased from 248 +/- 19 to 366 +/- 52 g X h-1 (p less than 0.05), respectively. Both the total integrated Tre and Tsk curves after NI were higher (p less than 0.05) than for C. These results suggest that, compared with control responses, the equilibrium level of core temperature during submaximal exercise is regulated at a higher level after immersion.     

Comparison of four noninvasive rewarming methods for mild hypothermia.

Four noninvasive rewarming techniques for mildly hypothermic subjects were compared. Seven subjects were cooled in a water bath of 15 degrees C for 2 h to an average esophageal temperature (Tes) of 36 degrees C. Thereafter, the subjects were rewarmed by immersion of the body in a water bath of 42 degrees C (Method 1), the body but not the extremities in water of 42 degrees C (Method 2), only the extremities in water of 42 degrees C (Method 3), or spontaneous rewarming in blankets (Method 4). Method 1 showed the highest rewarming rate in Tes (10.1 degrees C/h) and an afterdrop in Tes of 0.18 degrees C. Method 2 showed the same afterdrop, but a lower rewarming rate (7.5 degrees C/h). In Method 3, the heat uptake of the extremities was too low to rewarm the subjects effectively. The afterdrop and rewarming rate were 0.38 degrees C and 0.8 degrees C/h, respectively. Method 4 had the lowest rewarming rate (0.2 degrees C/h), and an afterdrop (0.14 degrees C) which was not significantly lower than that of Method 1 or 2. Therefore, Method 1 is recommended for rewarming mild hypothermic subjects because of its high rewarming rate and small afterdrop.     

Comparison of rewarming by radio wave regional hyperthermia and warm humidified inhalation

Anesthetized random source dogs were cooled by ice water immersion to a stable core temperature of 25 degrees C and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation X kg-1) or radio-frequency induction hyperthermia (4-6 watts X kg-1). The mean time required for core rewarming to 30 degrees C was 280 +/- 114 min for ventilation and 58 +/- 13 min for radio wave therapy (p less than 0.001). There was no evidence of tissue damage with either modality. These data suggest radio wave heating is superior to warm humidified inhalation therapy for core rewarming of rapidly induced immersion hypothermia.     

Hypothermia and electromagnetic rewarming in the rhesus monkey

Five male rhesus monkeys (Macaca mulatta) were subjected, under ketamine anesthesia, to repeated hypothermia treatments that produced an average rectal temperature of 28.3 degrees C. Following hypothermia induction, the subjects were rewarmed using either a ventrally applied surgical heating pad supplied with 35 degrees C water or a radio-frequency (RF) induction coil operating at 13.56 MHz with an average specific absorption rate (SAR) calculated to be approximately 5.5 W X kg-1. A special temperature probe, nonperturbing to RF, was used in the RF rewarming experiments. Control experiments were also conducted in which only ketamine was administered over a 3-h period. RF rewarming to 35 degrees C typically required only 50 min; whereas, an average of 137 min was required for heating-pad rewarming. Analyses of blood serum collected during and up to 48 h after hypothermia treatments showed elevations at 24 h in creatine phosphokinase (CPK), lactic dehydrogenase (LDH), and glutamic oxaloacetic transaminase (GOT), and these elevations were highest for the ketamine controls and lowest for the RF rewarming experiments. The subjects have been periodically examined since these experiments, and all appear to be in good health. It is concluded that the careful application of RF energy to the central core of the body can successfully be used for rewarming purposes, is more effective than externally applied rewarming techniques, and is potentially useful in remote locations.     

Temperature and metabolic responses to inhalation and bath rewarming protocols

Rewarming of mildly hypothermic subjects was compared using three different techniques that have been suggested for use in field situations. Eight subjects were cooled for up to 1 h, on four occasions, in a filled whole-body water calorimeter controlled at 22 degrees C. Following cooling, rewarming was initiated by one of four procedures: inhalation of warmed and humidified air at 40 degrees C or 45 degrees C, immersion in 40 degrees C water, or spontaneously by shivering. Deep body temperature was recorded simultaneously at three different sites: rectal, esophageal, and auditory canal. Skin temperatures were recorded from four sites: chest, forearm, thigh, and calf. Results showed that rapid external rewarming in 40 degrees C water produced the quickest rate of rewarming and smallest magnitude and duration of afterdrop. Regardless of which rewarming protocol was followed, the esophageal site always showed the smallest afterdrop. Although there were no differences in the rewarming rates calculated for each of the three core temperature sites during inhalation and spontaneous rewarming, both auditory canal and esophageal sites rose significantly quicker than rectal during the rapid rewarming in 40 degrees C water. Inhalation rewarming led to a depressed metabolic rate, compared to spontaneous rewarming, which was not compensated by heat provided through the respiratory tract. It was concluded that for mildly hypothermic subjects, rapid rewarming in 40 degree C water was the most efficient procedure and that esophageal temperature--the closest approximation of aortic blood or cardiac temperature--is the most sensitive to change during rewarming by any procedure.(ABSTRACT TRUNCATED AT 250 WORDS)     

An improved method for inducing hypothermia and rewarming.

A hypothermia and rewarming system combining body surface and ventilatory heat exchange is described. The method utilizes body surface heat exchange through conduction, convection, and black body radiation, and ventilatory heat exchange across the lung surface through conduction, convection, and water evaporation. The system consisted of a chamber in which the temperature was maintained at a desired level (+/- 2.5 degrees C) using a refrigeration-heat pump unit. Chamber temperatures during cooling and rewarming were -15.5 +/- 2.7 degrees C and 43.2 +/- 2.3 degrees C, respectively. Inhalate temperatures during cooling were -8.2 +/- 6.5 degrees C and during rewarming they were 41.5 +/- 0.3 degrees C. Helium (100%) was supplied to the chamber, while the animal was ventilated with 20% O2 + 80% He. Under these conditions, the cooling and rewarming rates were 0.33 +/- 0.06 degrees C/min and 0.20 +/- 0.04 degrees C/min, respectively, at 38--21 degrees C. The system provided for rapid cooling and rewarming with no evidence of any untoward effects.     

Fluid-electrolyte losses in uniforms during prolonged exercise at 30 degrees C.

The effects of several uniform configurations on fluid and electrolyte losses in a hot environment (30 degrees C db, 18 degrees C wb) were studied in 15 healthy males, during 6 h of intermittent treadmill exercise (1.56 m.s-1, 0% grade, 50 min.h-1, 28 km total distance). The uniforms were: the temperate battle dress uniform (BDU), two variants (C and F) of full military oriented protective posture (MOPP IV), and MOPP IV with no mask or hood (M). Sweat rate, urine volume, electrolyte losses (Na+, Cl-, K+, Mg++, Ca++) in sweat and urine, rectal temperature, mean skin temperature, heart rate, and temperature/humidity inside uniforms were measured. Observations indicated that both MOPP IV configurations (C and F) resulted in significantly greater (p. less than 0.05) fluid losses and physiological strain than BDU and M. However, there were no between-uniform differences in the total loss of any electrolyte. Total body fluid losses (kg.6h-1) and electrolyte losses in sweat (mEq.6h-1) were consistently greater than in urine. It was concluded that 6 h of exercise in uniforms at 30 degrees C can result in losses of Na+ and Ca++ which exceed the normal daily intake of these electrolytes. Supplementation of fluid, Na+, and Ca++ appears to be warranted when scenarios require 6 h or more of uniformed exposure to heat.     

Variability in intake and dehydration in young men during a simulated desert walk

Voluntary dehydration was examined in young unacclimatized men walking under simulated desert conditions. Thirty-three subjects (20-33 years) walked on a treadmill (4.82 km.h-1, 5% grade) for 30 min.h-1 for 6 h in a hot environment (40 degrees C db/26 degrees C wb, 4.02 km.h-1 windspeed). Cool (15 degrees C) water was provided ad libitum in canteens. Because thirst is stimulated and drinking should occur at about 2% body weight loss as body water, we used this criterion to identify two groups of individuals. Individuals who maintained body weight (BW) loss at less than 2% (0.44-1.88%) were defined as avid drinkers (D, n = 20) and those who exceeded the 2% BW loss (2.07-3.51%) despite the continual availability of cool (15 degrees C) water were called reluctant drinkers (RD, n = 13). RD consumed 31% less water (2.05 +/- 0.14 L) than D (2.98 +/- 0.12 L), and this resulted in a significantly greater BW loss in RD (2.65 +/- 0.11%) than D (1.16 +/- 0.11%). However, the only statistically significant differences in plasma indices of dehydration were the higher final plasma Na+ and protein levels in RD. Rectal temperature was higher in the RD, whereas final heart rates were unaffected. In the current study, about 40% of the young adult male subjects were reluctant to drink, and thus voluntarily dehydrated even when given cool water ad libitum during intermittent exercise in the heat. The reduced intake of these reluctant drinkers may be critical in predisposing them to increased risk of dehydration and heat injury.     

Effect of rewarming at various water bath temperatures in experimental frostbite

Studies have been conducted on 72 rats to determine the most suitable temperature at which rapid rewarming should be done as an immediate treatment for frostbite. Animals were put in a harness containing arrangements for warming the body. Their hind limbs were left out of the harness. They were then exposed to -15 degrees +/- 1 degrees C in a deep freeze for 60 min, during which paw temperature was recorded every 5 min. After this, the animals were taken out, the left hind limb was rapidly rewarmed in a water bath maintained at 35 degrees, 37 degrees, 39 degrees, 41 degrees, 43 degrees, or 45 degrees C for different batches and the right hind limb was left free for slow rewarming at room temperature (27 degrees -29 degrees C). The severity of cold injury in the two limbs was compared. The paw temperature showed a drop on cold exposure, followed by a rapid rise and then a second fall. The degree of injury was related to the duration of exposure after the rise in the paw temperature. The rapid rewarming was effective only at water bath temperature of 37 degrees-39 degrees C and was harmful at 45 degrees C. This shows that rewarming at about body temperature is most effective as immediate treatment for frostbite.     

An atropinized heat-stressed rat model: dose response effects and pharmacokinetics

Atropine and other anticholinergic drugs are widely used in common medications and in the treatment of organophosphate poisoning. Man dissipates heat by the evaporation of sweat. Analogously, rats spread saliva over their bodies for evaporative cooling. Atropine inhibits both sweating and salivation. Therefore, we sought to quantitate the effects of atropine in our rat heatstroke model. While heat-stressing adult male rats of 500 or 250 g at 41.5 degrees C, we measured the effects of i.v. atropine (10-4000 micrograms X kg-1) on the following: heating rate (HR), % wt loss (saliva production), and fecal loss (intestinal motility). HR (degree C X min-1) was the most sensitive index of drug activity with a 200 micrograms X kg-1 dose (equivalent to 2 mg in man for organophosphate poisoning) eliciting an increased HR from 0.022 degrees C (saline) to 0.087 degrees C X min-1 (atropine). Atropine (200 micrograms X kg-1) increased HR even if administered 3 h prior to heat exposure. Large (500 g) rats showed an increase in HR with 25 micrograms X kg-1 of atropine, but 250 g rats required 50 micrograms X kg-1. This model could be used to assess the relative effects of other anticholinergic drugs and as a non-dehydrated heatstroke model.     

右旋美托咪定用于下肢骨折手术临床疗效观察

目的观察右旋美托咪定（DEX）持续泵注对下肢骨折手术患者血流动力学和寒颤反应的影响。方法择期下肢骨折手术患者60例,随机分为两组,右旋美托咪定组（D组,n=32）和对照组（C组,n=28）。所有患者均采用L3～4间隙硬膜外-蛛网膜下腔联合麻醉（CSEA）,麻醉平面固定后开始持续泵注DEX0.4～0.6μg·kg-1·h-1,C组泵注等体积生理盐水,记录两组患者从入室到术毕6个时点（T0～T5）的MAP、HR、SpO2及术中寒颤情况。结果 MAP组间比较无差异（P〉0.05）;组内与T0比较有差异（P〈0.05）。D组HR显著低于C组（P〈0.05）;组内与T0比较有差异（P〈0.05）。SpO2组间比较无差异（P〉0.05）,组内与T0比较有差异（P〈0.05）。D组寒颤发生率低于C组（P〉0.05）。结论 DEX持续泵注用于下肢骨折手术可提供良好的镇静效应及血流动力学稳定,减少术中寒颤发生。     

Guidelines for optimal replacement beverages for different athletic events.

During exercise, especially endurance exercise in the heat, vital body fluids and essential ions are lost in sweat, and the body may deplete its glycogen stores. Unless essential body fluids are restored, these conditions can produce hypovolemia, hypoglycemia, hyponatremia, hyperthermia, and dehydration. Performance may also be reduced. This paper briefly reviews pertinent aspects of gastric emptying and intestinal absorption and proposes the formulation of beverages for ingestion both pre-event and during exercise. For events lasting less than 1 h, 300-500 ml of a 6-10% CHO beverage is recommended pre-event (0-15 min), and cool (5-15 degrees C) water in a volume approximately half the subjects sweat rate is recommended during exercise. For events between 1-3 h long, 300-500 ml of water is recommended pre-event, and 800-1600 ml.h-1 of a 6-8% CHO solution with 10-20 mEq Na+ is recommended during exercise. For events longer than 3 h, 300-500 ml of water is recommended pre-event, and 500-1000 ml.h-1 of a 6-8% CHO beverage with 20-30 mEq Na+ is recommended during exercise. In recovery, a beverage containing 5-10% CHO with 30-40 mEq Na+ should be ingested to achieve euhydration. A minimum of 50 g.h-1 of CHO should be ingested in the first 2 h to maximize glycogen repletion. Guidelines to follow in formulating these beverages are reviewed and the rationale for each formulation is provided.     

Immersion of distal arms and legs in warm water (AVA rewarming) effectively rewarms mildly hypothermic humans

INTRODUCTION: Active rewarming of hypothermic victims for field use, and where transport to medical facilities is impossible, might be the only way to restore deep body temperature. In active rewarming in warm water, there has been a controversy concerning whether arms and legs should be immersed in the water or left out. Further, it has been suggested in the Royal Danish Navy treatment regime, that immersion of hands, forearms, feet, and lower legs alone might accomplish rapid rates of rewarming (AVA rewarming). METHODS: On three occasions, six subjects (one female) were cooled in 8 degrees C water, to an esophageal temperature of 34.3+/-0.8 (+/-SD) degrees C. After cooling the subjects were warmed by shivering heat production alone, or by immersing the distal extremities (hands, forearms, feet and lower legs) in either 42 degrees C or 45 degrees C water. RESULTS: The post cooling afterdrop in esophageal temperature was decreased by both 42 degrees C and 45 degrees C water immersion (0.4+/-0.2 degrees C) compared with the shivering alone procedure (0.6+/-0.4 degrees C; p < 0.05). The subsequent rate of rewarming was significantly greater with 45 degrees C water immersion (9.9+/-3.2 degrees C x h(-1)) than both 42 degrees C water immersion (6.1+/-1.2 degrees C x h(-1)) and shivering alone (3.4+/-1.5 degrees C x h(-1); p < 0.05). CONCLUSION: The extremity rewarming procedure was experienced by the subjects as the most comfortable as the rapid rise in deep body temperature shortened the period of shivering. During the extremity rewarming procedures the rectal temperature lagged considerably behind the esophageal and aural canal (via indwelling thermocouple) temperatures. Thus large gradients may still exist between body compartments even though the heart is warmed.     

Effect of altitude acclimatization on thermoregulation efficiency of man

A study has been conducted on 20 sojourners (SJs) at a high altitude (HA) of 3500 m to evaluate the changes in thermoregulation efficiency (ThE) during acclimatization for 3 weeks, by observing the rate and pattern of rewarming of palm skin temperature (Tsk) after dipping the hand in water of 10 +/- 1 degrees C for 2 min (Tromp's water bath test). The ThE of the SJs was compared to that of 10 acclimatized lowlanders (ALs) staying at the same altitude for about 1 year and 10 high-altitude natives (HANs). In SJ, at sea level (SL), the effect of seasonal variation and ambient temperature on ThE was also studied. The initial Tsk of the palm (29.9 degrees C) was lower at altitude as compared to SL value (32.2 degrees C) in SJs inspite of similar ambient temperature (21 +/- 1 degrees C). There was a prolongation of rewarming time in all the subjects during stay at altitude. The rewarming curve showed a shift towards the right, indicating slower rewarming. The rewarming response of ALs and SJs was comparable at altitude. In HANs, the rewarming at altitude was faster and resembled those of SJs at SL. The rewarming improved in the season following cold months, and at higher ambient temperature in the same season, on the plains. It may be concluded that thermoregulation efficiency of man deteriorates at high altitude, and the peripheral vascular responses to local cold stress do not reach the level attained by natives even after 1 year of acclimatization. General cold acclimatization improves the rewarming response.     

Contribution of exercise and shivering to recovery from induced hypothermia (31.2 degrees C) in one subject

The ability of a modestly hypothermic victim to exercise, and indeed shiver, and thereby generate sufficient heat to rewarm has been questioned. One fit healthy subject was cooled in stirred water (7.7 degrees C) to a core temperature (Tc) of 32 degrees C. Tc by esophageal probe, cardiac rhythm, blood pressure (BP) and oxygen consumption (VO2) were monitored pre-, intra-, and postcooling (exercise). The subject rewarmed spontaneously as well as by exercising on a treadmill at speeds from 0.7 to 3.5 mph. Amount of Tc afterdrop (AD) was measured and rate of Tc increase (RI) and exercise and shivering contributions to heat production were calculated. The AD was 0.8 degrees C and the RI was 5.2 degrees C.h-1. VO2 values at the onset of hypothermic exercise indicated an approximate 4-fold increase in heat production from the normothermic resting value. A small portion of this heat production resulted from exercise while the majority was from shivering. Maximal heat production occurred at the lowest Tc (31.2 degrees C.). This represented an approximate 5-fold increase over the resting normothermic value. Shivering continued to provide the majority of the heat. As Tc increased, however, although heat production remained relatively constant, the contribution of exercise increased and that of shivering decreased. It was possible for this man to do a slight exercise at a Tc as low as 31.2 degrees C and the rewarming rate from shivering was substantial. Significant heat production is initially primarily by shivering thermogenesis, but soon, at a higher Tc, by exercise as well.     

Cranial-neck and inhalation rewarming failed to improve recovery from mild hypothermia

INTRODUCTION: Rewarming from hypothermia in a field setting is a challenge due to the typical lack of significant power or heat source, making the targeted application of available heat critical. The highly vascular area of the head and neck may allow heat to be rapidly transferred to the core via blood circulation. At the same time, the warming of only a small skin surface may minimize the rapid rise in skin temperature proposed to attenuate shivering and endogenous heat production. Therefore, we investigated the efficacy of targeting the head and neck for rewarming from mild hypothermia. METHODS: There were 16 participants (9 men, 24.1 +/- 4.5 yr, 15.5 +/- 3.9% body fat; 6 women, 23.0 +/- 5.4 yr, 20.8 +/- 3.2% body fat) who were cooled in 15 degrees C water until rectal or esophageal temperature reached 35.5 degrees C, whereupon they were removed and provided passive (PASS), cranial-neck (CN), or cranial-neck and inhalation (CNIR) rewarming. Heart rate and skin temperature were also measured. RESULTS: The mean cooling times were PASS=83 min (range: 22-295 min), CN=94 min (range: 28-314 min), CNIR=97 min (range: 22-285 min). No significant differences (p > 0.05) were found for magnitude of after-drop (PASS = 0.33 +/- 0.24 degrees C, CN = 0.31 +/- 0.18 degrees C, CNIR = 0.29 +/- 0.28 degrees C esophageal temperature) and duration of afterdrop (PASS = 15.4 +/- 10.2 min, CN = 13.0 +/- 10.1 min, CNIR = 8.8 +/- 6.9 min). No significant differences (p > 0.05) were found for rewarming rate (PASS = 1.85 +/- 1.33 degrees C x h(-1), CN = 1.45 +/- 1.04 degrees C x h(-1), CNIR = 2.24 +/- 1.51degrees C x h(-1) esophageal temperature). DISCUSSION: In summary, neither cranial-neck nor cranial-neck and inhalation rewarming combined have an advantage in reducing the magnitude and duration of after-drop or increasing the rewarming rate over passive rewarming.     

右美托咪定用于体外循环下心脏瓣膜置换术患者临床观察

目的评价右美托咪定用于体外循环(CPB)下心脏瓣膜置换术患者的临床效果。方法选择我院2013年1月至2014年1月择期拟在全麻及CPB下行心脏瓣膜置换术患者60例为研究对象。采用随机数字表法,将患者随机分为两组:右美托咪定组(D组)和生理盐水对照组(C组),每组30例。麻醉诱导后,D组经10 min静脉输注右美托咪定1μg/kg,随后以0.5μg/(kg·h)速度输注至术毕;C组以同样方法静脉输注等容量生理盐水。分别于麻醉诱导前(T_0)、停CPB后10 min(T_1)、术毕(T_2)、术后6 h(T_3)和术后24 h(T_4)时采集静脉血样,采用ELISA法测定血清肿瘤坏死因子(TNF-α)、白细胞介素-6(IL-6)和白细胞介素-10(IL-10)以及肌酸激酶同工酶(CK-MB)、血清肌钙蛋白Ⅰ(CTnI)的水平;并记录两组患者主动脉开放后心脏自动复跳情况和术中血管活性药物(多巴胺、去甲肾上腺素和肾上腺素)使用情况。结果与T_0时比较,T_1~T_4时两组患者血清TNF-α、IL-6、IL-10及CK-MB、CTnI浓度升高(P<0.05);与C组比较,D组T_1~T_4时血清TNF-α及IL-6浓度降低,IL-10浓度升高,T_3~T_4时血清CK-MB及CTnI浓度降低,主动脉开放后心脏自动复跳率升高,术中多巴胺用量、去甲肾上腺素用量及肾上腺素使用率降低(P<0.05)。结论右美托咪定可减轻CPB下心脏瓣膜置换术患者围术期炎性反应,并可产生一定的心肌保护作用。