Nonpharmacologic approach to minimizing shivering during surface cooling: A proof of principle study

Purpose

This study had 2 objectives: (1) to quantify the metabolic response to physical cooling in febrile patients with systemic inflammatory response syndrome (SIRS) and (2) to provide proof for the hypothesis that the efficiency of external cooling and the subsequent shivering response are influenced by site and temperature of surface cooling pads.

Methods

To quantify shivering thermogenesis during surface cooling for fever, we monitored oxygen consumption (VO₂) in 6 febrile patients with SIRS during conventional cooling with cooling blankets and ice packs. To begin to determine how location and temperature of surface cooling influence shivering, we compared 5 cooling protocols for inducing mild hypothermia in 6 healthy volunteers.

Results

In the patients with SIRS, core temperature decreased 0.67°C per hour, all patients shivered, VO₂ increased 57.6%, and blood pressure increased 15% during cooling. In healthy subjects, cooling with the 10°C vest was most comfortable and removed heat most efficiently without shivering or VO₂ increase. Cooling with combined vest and thigh pads stimulated the most shivering and highest VO₂ and increased core temperature. Reducing vest temperature from 10°C to 5°C failed to increase heat removal secondary to cutaneous vasoconstriction. Capsaicin, an agonist for the transient receptor potential cation channel subfamily V member 1 (TRPV1) warm-sensing channels, partially reversed this effect in 5 subjects.

Conclusions

Our results identify the hazards of surface cooling in febrile critically ill patients and support the concept that optimization of cooling pad temperature and position may improve cooling efficiency and reduce shivering.     

术前预先使用布托啡诺鼻喷剂对腰硬联合麻醉后寒战反应的影响

目的观察预先使用布托啡诺鼻喷剂对经皮肾镜手术（PCNL）腰硬联合麻醉后寒战反应的影响。方法选择94例ASA Ⅰ—Ⅱ级经皮肾镜手术腰硬联合麻醉患者,随机分为两组布托啡诺鼻喷剂组（观察组）、安慰剂组（对照组）,布托啡诺鼻喷剂组在腰硬联合麻醉前15min用2mg布托啡诺喷鼻;对照组用安慰剂生理盐水喷鼻。观察麻醉后两组患者寒战发生的情况及镇静评分。结果观察组寒战反应发生率明显低于对照组（P〈0．01）,镇静评分满意率观察组显著高于对照组（P〈0．05）。结论预先使用布托啡诺鼻喷剂能够有效地预防经皮肾镜镜（PCNL）手术腰硬联合麻醉后寒战的发生,且镇静效果满意。     

Increase in oxygen consumption induced by selective spinal cord cooling in the exercising pigeon

Six domestic pigeons with chronically implanted spinal thermodes were exercised on a treadmill at neutral ambient temperature. During the exercise the spinal cord was cooled to 34.7±0.4°C (mean±S.E.M.). Oxygen consumption of the pigeons increased from 28.3 ±2.1 to 61.2±3.7 ml·min^–1·kg^–1 due to exercise per se, and superimposed cooling of the spinal cord during exercise induced an additional increase in oxygen consumption to 84.9±4.5 ml·min^–1·kg^–1. The result demonstrates that cooling of the spinal cord elicits shivering in exercising pigeons at thermoneutral conditions.     

哌氟合剂及红外线热幅射应用于防治硬膜外麻醉中寒战

随机选择硬膜外麻醉择期手术病人160例,分为三组,即治疗组、药物预防组和药物加红外线热幅射预防组。分别应用哌氟合剂(哌替啶25～50mg及氟哌啶2.5～5mg)及哌氟合剂加红外线热幅射防治硬膜外麻醉中寒战反应。结果表明哌氟合剂静滴消除寒战有效率达96.6%,预防有效率94%。哌氟合剂加红外线热幅射保温均无寒战发生。     

Effects of acclimatization to cold baths on men's responses to whole-body cooling in air

Summary The purpose of this study was to investigate the thermoregulatory mechanisms underlying artificial acclimatization to cold and to compare them with those of naturally acclimatized men. Six white men were cooled, nude, in air at 10°C for 2 h before and after they had been acclimatized by ten daily cold (15°Q baths of 30–60 min followed by rapid rewarming in hot (38–42° C) water, and again 4 months later after acclimatization had decayed. Six control subjects also underwent the same tests, providing an opportunity to discriminate between changes caused by the immersions and those caused by extraneous influences. Acclimatization significantly reduced heat production and heat loss (P < 0.05) but did not change heat debt. The reduced heat production was accompanied by reductions in shivering (P < 0.10) and in cold-induced muscle tenseness; no evidence of nonshivering thermogenesis or active brown fat was found. These findings are attributed to increased tissue insulation, mediated by an enhanced vascular response to cold that did not involve the cutaneous circulation and was probably located in skeletal muscle. Thermal sensation and discomfort did not change, although perceived strain tended to increase (P = 0.08). Acclimatization was accompanied by, but was unrelated to, slower cooling of the finger and toe. The main conclusions, and many specific findings, agree with those of two previous studies made by the same techniques in naturally acclimatized men wintering in Antarctica. Other significant findings included changes — in particular reduced thermoneutral rectal temperature and a delayed onset of shivering — that are commonly regarded as evidence of acclimatization but were in fact unrelated to it as they also occurred in the control group. They are attributed to extraneous influences, in particular the relaxation of heightened arousal (first-time effects) found in the baseline tests.     

The thermogenic effect of a carbohydrate feeding during exposure to 8,12 and 27° C

The increased metabolic heat production in humans exposed to cold stress results from an increased oxidation of both carbohydrate and fat to provide energy to sustain temperature homeostasis. Research suggests that dietary manipulations may enhance metabolic heat production, thereby delaying hypothermia. Therefore, the present investigation examined the thermogenic effect of a sequential timed feeding regime of either a carbohydrate (CHO) or a placebo beverage (PL) before and again midway through 120 min of exposure to 8, 12 and 27° C in well-nourished men. The following were examined: tissue insulation (I), rectal temperature (T _re), mean skin temperature , metabolism (M), time-weighted heat production and respiratory exchange ratio (R).T _re, T _re, M, M,I and time-weighted heat production revealed no significant differences between treatment (PL vs CHO) at any temperature (8, 12 and 27° C). However,T _re decreased (P < 0.05) as time increased at 8, 12 and 27° C while M increased (P < 0.05) andI decreased (P < 0.05) at 8 and 12° C. At 8 and 27° C,R differed (P < 0.05) between the PL and CHO treatments. In addition, at 8 and 12° C,R increased (P < 0.05) across time reflecting the feeding. From these data it appears that while substrate utilization differed between dietary treatment (8 and 27° C) and across time, this feeding regime did not differentially affectT,T _re, andI during 120 min of exposure to 8, 12 and 27° C.     

Passive temperature lability in the elderly

Thermoregulatory responses of nine healthy elderly [seven men and two women; mean age (SD) 73.9 (4.8) years] were compared to those of nine young adult men [26.6 (5.2) years]. They exercised on a cycle ergometer for 20 min at an intensity inducing a heart rate equivalent to 65% of their predicted maximum, and were thereafter immersed in 28°C water. The exercise was conducted to elevate tympanic temperature (T _ty) and initiate a steady rate of sweating. The post-exercise immersion period induced gradual cooling ofT _ty, and changes inT _ty relative to resting levels (ΔT _ty) at which sweating abated and shivering commenced were defined as the ΔT _ty thresholds for the cessation of sweating (T _sw) and onset of shivering (T _sh), respectively. In addition toT _ty, oxygen uptake ( ; 1 · min⁻¹), sweating rate (g · m⁻² · min⁻¹), and forehead skin blood perfusion were also measured during the trials. The mean (SD)T _sw occurred at a significantly (P <0.005) higher ΔT _ty [0.48 (0.18)°C] in the elderly than in the young adults [0.21(0.06)°C], while the Tsh occurred at significantly (P < 0.005) lower ΔT _ty in the elderly [ −0.64 (0.34)°C] than in young adults [−0.22 (0.10)°C]. Decreases in ΔT _ty below the shivering threshold were met with a significantly (P <0.01) reduced . The range of temperature lability between Ts, andT _sh, defined as the null-zone, was significantly greater in the elderly [1.12 (0.39)°C] than in the young adults [0.43 (0.12)°C], and the slope of the vasoconstrictor response in the null-zone was significantly (P <0.001) lower in the elderly subjects. The present study demonstrates a greater passive core temperature lability in older individuals, since the effector responses of sweating and shivering were initiated at higher and lower levels ofT _ty, respectively. The magnitudes of the effector responses beyond the thresholds were also significantly reduced, suggesting that the elderly may be more susceptible to hypo-/hyperthermia during periods of endogenous and/or exogenous thermal stress.     

Shivering and nonshivering thermogenesis in exercised cold-deacclimated rats

Summary Norepinephrine (NE)-induced increase in oxygen consumption ( ) and colonic temperature (Tc) was greater in cold-acclimated rats housed at 4° C for 4 weeks (CA) than warm-acclimated controls housed at 24° C for 4 weeks (WA). On the other hand, shivering activity measured at 4° C was less in CA than in WA, while propranolol administration eliminated the difference between these two groups by enhancing shivering in CA. Wet weight and protein content of interscapular brown adipose tissue (IBAT) were greater in CA than in WA. Following cold acclimation, CA were deacclimated at 24° C for 5 weeks. During deacclimation, half of this latter group were forced to run (15 m·min^–1 for 1 h) every day (CD-T) while the remaining rats remained sedentary (CD-S). Shivering activity assessed at 4° C 4 weeks after commencing cold deacclimation was significantly less in CD-T than in CD-S and the difference disappeared following propranolol injection. and Tc responses to NE injection measured 1, 2 and 5 weeks after commencing cold deacclimation did not differ between CD-S and CD-T. Although IBAT weight was lighter in CD-T than in CD-S, its total protein content was not different between the latter two groups of rats. These results suggest that a greater degree of NE-independent nonshivering thermogenesis (NST) is retained in rats that are exercised during the process of deacclimation as compared with animals that are sedentary. This difference in NST would not seem to be directly related to BAT thermogenic capacity.     

高热大鼠不同程度寒颤模型的构建

目的探索高热大鼠降温处理过程中发生寒颤的体温阈值,构建不同程度寒颤大鼠模型。方法使用20%干酵母混悬液将体重为(200±20)g、基础体温为36.8℃~38.3℃的雄性SD大鼠致热,选取致热成功的大鼠40只,随机分为4组,每组10只,分别使用10、20、40 m L冰袋对高热大鼠施行颈部和腋下探索性降温处理30 min,对照组不进行降温。观察大鼠寒颤的表现、监测大鼠发生寒颤的肛温阈值。结果高热大鼠在降温处理30 min内,对照组和10 m L冰袋组大鼠身体任一部位均未发生寒颤;20 m L冰袋组大鼠发生轻度寒颤,表现为竖毛,头、颈部颤抖,伴或不伴上肢颤抖,发生轻度寒颤的平均肛温阈值为37.25℃,轻度寒颤发生率为100%;40 m L冰袋组大鼠发生重度寒颤,表现为竖毛,头、颈部、四肢和躯干均剧烈颤抖,尾巴肌张力增强,发生重度寒颤的平均肛温阈值为37.07℃,重度寒颤发生率为90%。结论对高热大鼠进行冰袋降温干预可以构建出较为理想的无寒颤、轻度寒颤、重度寒颤模型。     

盐酸萘福泮与芬太尼治疗椎管内麻醉期寒战效果比较

目的研究比较盐酸萘福泮与芬太尼治疗椎管内麻醉期寒战效果。方法回顾性分析2011年6月—2012年9月期间,该院收治的48例剖宫产患者的临床资料,按照患者采用麻醉药物的不同,将其分为两组,对照组24例,采用芬太尼治疗,观察组24例,采用盐酸萘福泮治疗。比较两组患者治疗后的寒战发生情况和副作用情况。结果观察组患者的寒战缓解情况明显优于对照组,两组比较差异具有统计学意义(P<0.05),两组治疗后的副作用比较差异无统计学意义(P>0.05)。结论盐酸萘福泮在椎管内麻醉期寒战的治疗中疗效显著,安全性高,值得临床推广。