全身麻醉术后患者苏醒室内低体温发生率及其影响因素的Logistic回归分析

摘要 目的：统计全身麻醉术后患者苏醒室内低体温发生率,并分析其影响因素。方法：以2020年5月~2020年10月我院收治的110例接受全身麻醉手术的患者为研究对象,采用回顾性分析方法,整理患者的病历资料。观察全身麻醉术后患者苏醒室内低体温发生率,发生低体温的列为低体温组,未发生低体温的列为正常体温组,采用多因素Logistic回归分析低体温的相关因素。结果：全身麻醉术后患者苏醒室内低体温患者为15例,低体温发生率为13.64%（15/110）。单因素分析发现,全身麻醉术后患者苏醒室内低体温发生与年龄、麻醉时间、手术时间、美国麻醉医师协会（ASA）分级、苏醒延迟、术中输液量有关（P<0.05）,而与性别、体质量指数、术中环境温度、术前血红蛋白无关（P>0.05）。多因素Logistic回归分析结果显示,手术时间>4h、ASA分级为Ⅲ~Ⅳ级、术中输液量>1300 mL、年龄>60岁为全身麻醉术后患者苏醒室内低体温发生的影响因素（P<0.05）。结论：全身麻醉术后患者苏醒室内低体温的发生不可避免,且受多种因素影响,需尽量缩短手术时间,做好输入液体保温,特别做好老年患者保温工作,以减少低体温的发生风险。     

The efficacy of pre-warming on reducing intraprocedural hypothermia in endovascular coiling of cerebral aneurysms

Background

The anesthetic management of patients undergoing endovascular treatment of cerebral aneurysms in the interventional neuroradiology suite can be challenged by hypothermia because of low ambient temperature for operating and maintaining its equipments. We evaluated the efficacy of skin surface warming prior to induction of anesthesia to prevent the decrease in core temperature and reduce the incidence of hypothermia.

Methods

Seventy-two patients were randomized to pre-warmed and control group. The patients in pre-warmed group were warmed 30 minutes before induction with a forced-air warming blanket set at 38°C. Pre-induction tympanic temperature (Tpre) was measured using an infrared tympanic thermometer and core temperature was measured at the esophagus immediately after intubation (T0) and recorded at 20 minutes intervals (T20, T40, T60, T80, T100, and T120). The number of patients who became hypothermic at each time was recorded.

Results

Tpre in the control and pre-warmed group were 36.4 ± 0.4°C and 36.6 ± 0.3°C, whereas T0 were 36.5 ± 0.4°C and 36.6 ± 0.2°C. Core temperatures in the pre-warmed group were significantly higher than the control group at T20, T40, T60, T80, T100, and T120 (P < 0.001). Compared to T0, core temperatures at each time were significantly lower in both two groups (P = 0.007 at T20 in pre-warmed group, P < 0.001 at the other times in both groups). The incidence of hypothermia was significantly lower in the pre-warmed group than the control group from T20 to T120 (P = 0.002 at T20, P < 0.001 at the other times).

Conclusion

Pre-warming for 30 minutes at 38°C did not modify the trends of the temperature decrease seen in the INR suite. It just slightly elevated the beginning post intubation base temperature. The rate of decrease was similar from T20 to T120. However, pre-warming considerably reduced the risk of intraprocedural hypothermia.

Trial registration

Clinical Research Information Service (CRiS) Identifier: KCT0001320. Registered December 19th, 2014.     

Peripheral nerve at extreme low temperatures 1: Effects of temperature on the action potential

Hypothermia is an important means of neuroprotection. Understanding the effects of temperature on a physiologic measurement such as the nerve action potential (NAP) is important in monitoring its effects. The effects of hypothermia on the NAP amplitude, conduction velocity, and response to paired pulse stimulation were quantified in a rat sciatic nerve preparation from 37 to 10 °C. The time course of temperature related changes and the effect of repeated cycles of cooling and rewarming are explored using the following measures of the NAP: peak-to-peak amplitude, conduction velocity, duration, area under the curve and response to paired pulse stimuli. The NAP amplitude initially increases as temperature is reduced to 27 °C and then drops to roughly 50% of its baseline value by 16 °C while the area under the curve increases gradually until it begins to decline at 16 °C. Permanent loss of the NAP appears only after cooling below 10 °C for extended periods. Although the dependence of amplitude on temperature is approximately sigmoidal, the conduction velocity declines linearly at a rate of 2.8 m/s/°C. The response to paired pulse stimulation is strongly dependent on both temperature and the interstimulus interval with the responses at shorter interstimulus intervals being more temperature sensitive. With repetitive cycles of cooling and rewarming, the NAP amplitude declines by roughly 4% with every cycle without changes in the temperature at which the NAP amplitude reaches 50% of baseline. Only minor differences in conduction velocity are seen during cooling and rewarming.     

Body temperatures during three long-distance polar swims in water of 0–3 °C

1.

We report body temperature responses in a single individual to 3 swims of 1000 m or longer in ice-cold water (0–3 °C) during which he swam the normal crawl stroke with his face in the water whilst wearing only a swimming costume, swimming cap and goggles.     

Short-term preservation of canine preantral follicles: Effects of temperature, medium and time

The use of the large pool of preantral follicles is a promising alternative to provide high numbers of fertilizable oocytes to reproductive biotechnology. This issue is particularly important to canids, since current rates of success of in vitro techniques using oocytes are very limited, and many species within this family are threatened by extinction. The aim of this study was to evaluate effects of temperature, medium and time on morphology and viability of canine preantral follicles during short-term preservation. Canine ovaries were cut into fragments which were incubated in 0.9% NaCl solution or in minimum essential medium (MEM) at 4, 20 or 38 °C for 2, 6, 12 or 24 h. Afterwards, preantral follicles were analyzed by histology, transmission electron microscopy and viability testing using trypan blue, calcein-AM and ethidium homodimer-1. Percentages of morphological normal and viable follicles were maintained similar to control (time 0 h) after incubation in 0.9% NaCl at 4 or 20 °C for up to 6 h and at 38 °C for 2 h. Using MEM, such preservation was possible for 12 h at 4 or 20 °C, and for 6 h at 38 °C. These results indicate that preservation of canine preantral follicles might be better accomplished through hypothermic (4 or 20 °C) storage in MEM, which ensures maintenance of morphology and viability for up to 12 h.     

Influence of temperature on ischemic brain: basic and clinical principles

In the last decades, the interest in the association between body temperature and stroke outcome has reemerged, and the use of animal models has made it possible to know the underlying pathogenic mechanisms involved, most of them with pending confirmation in human clinics. In this work, we will review the effects of hyperthermia and hypothermia and its pathogenesis on ischemic stroke, and the evidence of the efficacy and safety of anti-hyperthermic and hypothermic treatments. We will describe how treatment of hyperthermia on ischemic stroke patients, improves patient comfort and outcome, both in the short and the long term, but new clinical studies are needed in this field. Despite the theoretical and experimental bases in favor of hypothermia for the treatment of brain ischemia, there is no definitive clinical evidence that has proved its benefits, so far. With current knowledge, an objective of a body temperature between 35.5 and 36.5 °C seems an optimal therapeutic target for both hyperthermic and normothermic patients.     

Physiological blocking of the mechanisms of cold death: theoretical and experimental considerations

The cold inhibited functions of skin thermoreceptors, of the thermoregulation centre, and the respiration centre during deep hypothermia can be restored without rewarming the body. The methods used were developed to test the hypothesis that during deep hypothermia calcium ion concentration [Ca²⁺]_i in the cytoplasm increases. This causes a perturbation of cell metabolism, the impairment of cell membrane function that cause the inhibition of cell functioning, resulting in cell death. Such an increase in [Ca²⁺]_i most likely would result from an energy deficit in a deeply cooled cell, which would compromise the processes that maintain the [Ca²⁺]_i at about 10⁻⁷ M. These processes require large amounts of energy since they occur against a large concentration gradient. With the use of EDTA the extracellular concentration of Ca²⁺ has been lowered by 15–27%, so reducing the concentration gradient for Ca²⁺ between the cell and the medium and in consequence facilitated the process the extrusion of cell Ca²⁺.

During a period of cooling, sufficient to impair normal functioning, the experimental lowering of blood Ca²⁺ allowed the restoration of normal function without the need to rewarm. In such cases the animals survived after cooling the body to temperatures at which they would normally have succumbed. The data presented support the stated hypothesis that the impairment of cellular function in mammals by low temperatures is the result of an uncorrected rise in [Ca²⁺]_i.     

Acid-base buffering in organ preservation solutions as a function of temperature: new parameters for comparing buffer capacity and efficiency

Control of acidity and preventing intracellular acidosis are recognized as critical properties of an effective organ preservation solution. Buffer capacity and efficiency are therefore important for comparing the relative merits of preservation fluids for optimum hypothermic storage, but these parameters are not available for the variety of organ preservation solutions of interest in transplantation today. Moreover, buffer capacity is dependent upon both concentration and pH such that buffer capacity is not easily predicted for a complex solution containing multiple buffer species. Using standard electrometric methods to measure acid dissociation constants, this study was undertaken to determine the maximum and relative buffer capacities of a variety of new and commonly used hypothermic preservation solutions as a function of temperature. The reference data provided by these measurements show that comparative buffer capacity and efficiency vary widely between the commonly used solutions. Moreover, the fluids containing zwitterionic sulfonic acid buffers such as Hepes possess superior buffering for alpha-stat pH regulation in the region of physiological importance.     

The influence of temperature on contractile properties of motor units in rat medial gastrocnemius

The effects of hypothermia and hyperthermia on mammalian skeletal muscle function have previously been reported. However, their effects on the contractile properties of different motor unit (MU) types were not described. This study aimed to explore the effect of temperature on contractile properties of MUs in rat medial gastrocnemius kept at 25 °C (hypothermia), 37 °C (normothermia), and 41 °C (hyperthermia). Hypothermia prolonged the twitch time parameters of all MU types, shifting the steep part of the force-frequency curve towards lower frequencies and increasing its steepness. In addition, it reduced the rate of force development but not the twitch and tetanus forces of slow-twitch (S) MUs. Moreover, it reduced the tetanic force of fast-twitch fatigable (FF) MUs and increased the twitch force of fast-twitch fatigue-resistant (FR) MUs. In contrast, hyperthermia had opposite effects on twitch time properties and the force-frequency relationship. The twitch-to-tetanus ratio decreased for FF and FR MUs, and the steep part of the force-frequency curve shifted towards higher frequencies and decreased in steepness. Our findings indicate that FF MUs are the most sensitive and S MUs are the least sensitive to temperature. Furthermore, force control processes involving changes in motoneuronal firing frequency were radically modified for fast MUs, especially FF MUs.