EMG activity in pectoral and femoral muscles during spinal cord cooling in exercising pigeons

Adult domestic pigeons, with thermodes chronically implanted in the vertebral canal, were trained to walk on a treadmill. In the first series of experiments, EMG activity in a pectoral (M. pectoralis) and a femoral muscle (M. biceps femoris) was measured to determine if shivering could occur during exercise. When the spinal cord was cooled (36.2±0.5°C) during exercise (0.6 km/h), pectoral muscle EMG activity increased by 80%, while femoral muscle EMG activity did not change significantly. EMG activity remained unchanged during exercise in control experiments where the spinal cord was not cooled.In the second series of experiments, the spinal cord was first cooled (36.1±0.5°C) for 5 min in resting pigeons and then the treadmill was started. Spinal cord cooling during rest significantly increased pectoral muscle EMG activity but not that of the femoral muscle. Within 1 s after the onset of exercise, EMG activity in the pectoral muscle decreased by 74%.In both series of experiments, shivering was not induced in the femoral muscle. The level of pectoral muscle EMG activity stimulated by spinal cord cooling during exercise in the first series of experiments corresponded to the level to which EMG activity was reduced by exercise during spinal cord cooling in the second series of experiments (192% and 186% in relation to the post-cooling level, respectively).It is concluded that shivering can be induced in the pectoral muscle by spinal cord cooling during exercise in the pigeon. The level of shivering induced in the pectoral muscle is well balanced according to the degree of spinal cord cooling (thermal information) and the running speed of exercise (non-thermal information possibly from active muscles and joints).     

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.     

曲马多预防麻醉后寒战的临床研究

目的 :旨在研究曲马多对全麻苏醒期寒战的预防作用及对苏醒时间的影响。方法 :将 15 0例病人随机分为两组 ,曲马多组 70例 ,对照组 80例。曲马多组于术毕给予曲马多 1mg kg静注 ,观察其术毕、给药后 5min、15min三个时间的血压及心率 ,同时记录两组病人苏醒期发生寒战的例数及术毕至拔除气管导管的时间。结果 :曲马多组术后寒战发生率为 1 43% ,对照组为 13 75 % ,两者比较p <0 0 1,其差异有非常显著性 ;两组术毕至拔管的时间分别为 ,曲马多组 (110 0 1± 6 4 6 2 )min ,对照组 (10 1 43± 5 4 48)min ,两者比较p>0 0 5 ,无统计学差异 ;曲马多组术毕、给药后 5min、15min血压及心率的变化无统计学差异。结论 :全麻病人术毕时静注 1mg kg曲马多 ,可有效地预防苏醒期寒战的发生 ;且对心血管系统无影响 ;亦不延长拔管的时间。     

昂丹西酮复合曲马多用于腰硬联合麻醉后寒颤的临床观察

目的探讨昂丹西酮复合曲马多用于腰硬联合麻醉后寒颤的临床效果。方法ASAⅠ-Ⅱ级择期在腰硬联合麻醉下行下腹部或下肢手术患者100例，随机分为4组，生理盐水组（N组），昂丹西酮组（0组），曲马多组（T组），昂丹西酮复合曲马多组（O＋T组）。N组静脉注射生理盐水10mL，O组静脉注射昂丹西酮4 mg，T组静脉注射曲马多1mg／kg，O＋T组是在O组的基础上患者行麻醉穿刺后于平卧位后静脉注射曲马多1mg／kg。观察术中寒颤和恶心、呕吐等的发生情况。结果寒颤发生率N组与O组、T组、O＋T组比较有显著性差异（P〈0．01），恶心、呕吐发生率O＋T组、O组与N组、T组比较有显著性差异（P〈0．05）。结论麻醉前静脉注射昂丹西酮4mg，平卧位后静脉注射曲马多1mg，kg，对麻醉后寒颤起到很好地预防和治疗作用，并大大降低了恶心、呕吐的发生率。     

Thermoregulatory model for prediction of long-term cold exposure

A multi-segmental mathematical model has been developed for predicting shivering and thermoregulatory responses during long-term cold exposure. The present model incorporates new knowledge on shivering thermogenesis, including the control and maximal limits of its intensity, inhibition due to a low core temperature, and prediction of endurance time. The model also takes into account individual characteristics of age, height, weight, % body fat, and maximum aerobic capacity. The model was validated against three different cold conditions i.e. water immersion up to 38 h and air exposure. The predictions were found to be in good agreement with the observations.     

Effect of postoperative skin-surface warming on oxygen consumption and the shivering threshold

Cutaneous warming is reportedly an effective treatment for shivering during epidural and after general anaesthesia. We quantified the efficacy of cutaneous warming as a treatment for shivering. Unwarmed surgical patients (final intra-operative core temperatures approximately 35 degrees C) were randomly assigned to be covered with a blanket (n = 9) or full-body forced-air cover (n = 9). Shivering was evaluated clinically and by oxygen consumption. Forced-air heating increased mean-skin temperature (mean (SD) 35.7 degrees C (0.4) vs. 33.2 degrees C (0.8); p < 0.0001) and lowered core temperature at the shivering threshold (35.7 degrees C (0.2) vs. 36.4 degrees C(0.2); p < 0.0001). Active warming improved thermal comfort and significantly reduced oxygen consumption from 9.7 (4.4) ml x min(-1) x kg(-1) to 5.6 (1.9) ml x min(-1) x kg(-1) (p = 0.038). However, the duration of shivering was similar in the unwarmed (37 min (11)) and active warming (36 min (10)) groups. Core temperature contributed about four times as much as skin temperature to control of shivering. Cutaneous warming improved thermal comfort and reduced metabolic stress in postoperative patients, but did not quickly obliterate shivering.     

Effect of Pethidine, Fentanyl and Morphine on Post-Operative Shivering in Man

One hundred consecutive patients who shivered following general or regional anesthesia and a surgical procedure were randomly treated with 25 mg pethidine, 2.5 mg morphine, 25 micrograms fentanyl or sodium chloride 0.9%, given in equal intravenous volumes over a 15-min period. The effects were evaluated every 5 min after the first injection. There was a spontaneous, time-related disappearance of shivering in the sodium chloride-treated patients. In the pethidine-treated group, shivering disappeared more than twice as fast as in the control group. The difference was highly significant at 15 and 20 min (P less than 0.001) and was unrelated to weight, body temperature or duration of anesthesia. Women responded sooner than men, reaching significance at 10 min (P less than 0.05), while men did so only at 20 min. Morphine or fentanyl had no effect. Nausea and vomiting were minimal and of equal incidence in narcotic- and placebo-treated patients.     

The postures of catecholamine-depletion catalepsy: their possible adaptive value in thermoregulation

Our view of the cataleptic akinesia induced by the disruption of catecholaminergic systems is that it is a state in which the postural and motor subsystems organized to maintain static stable equilibrium (e.g., standing or bracing, and righting) are functioning, whereas other subsystems such as those involved in exploration (walking, scanning, or orienting) and eating are inoperative. In addition to their role in actively maintaining stable equilibrium, the postures of cataleptic akinesia appear also to be related to thermoregulation. Slight skin warming in animals made cataleptic and akinetic following lateral hypothalamic lesions or intraventricular 6-hydroxydopamine causes a dramatic inactivation of tonic support (the subsystem involved in standing and bracing) and the animal subsides into a prone position. So profound is the torpor induced by warming that if the animal is slowly rolled over onto its back, it no longer rights itself. Furthermore, otherwise untreated normal rats made severely hypothermic by a period of immersion in cold water assume the crouched immobile postures of cataleptic akinesia seen in the uncooled, normothermic catecholamine-depleted animal. After a few minutes, shivering is superimposed on these postures. We suggest that the seemingly bizarre condition of cataleptic-akinesia can be viewed as a very simplified neural state organized to permit not only the regulation of stable equilibrium, but also shivering thermogenesis.     

Quinine-induced hypothermia in cold-exposed rats

Quinine HCl in doses from 10–50 mg/kg lowered the body temperatures of nonfebrile rats in the cold, primarily by suppressing shivering. However, if given an opportunity to turn on a heat lamp the rats worked much more than normal after a quinine injection and were thereby able to counteract the hypothermia to some extent. The effect of quinine is interpreted as an action on effector mechanisms rather than as an alteration of the thermal setpoint.     

胸段硬膜外阻滞复合全麻中轻度低温的临床观察

目的:研究胸段硬膜外阻滞复合全身麻醉中轻度低温的形成规律及其对麻醉恢复期寒冷应激反应的影响。方法:选择ASAⅠ-Ⅱ食管癌根治术患者20例,均采用胸段硬膜外阻滞复合全身麻醉。诱导前20min开始每间隔10min记录鼓膜温度。观察记录所有患者术后1h时的热舒适度评分和术后3h内的寒战反应发生情况。结果:麻醉诱导后鼓膜温度呈进行性降低趋势,鼓膜温度的降温速度、降低值在各时间点之间的差异有统计学意义(P<0.05)。术后1h时的热舒适度评分为25±8,术后3h内有13例患者发生了寒战反应。结论:胸段硬膜外阻滞复合全身麻醉中会导致轻度低温,麻醉后第1h降温较快,此后相对缓慢但仍呈持续性下降趋势。轻度低温可导致术后寒战和寒冷不适感。