Prevention of post-anaesthesia shivering

Underbody blankets have a higher heating effect than overbody blankets in lithotomy position endoscopic surgery under general anesthesia: a randomized trial

BACKGROUND

Surgery under general anesthesia results in temperature decrease due to the effect of anesthetics and peripheral vasodilation on thermoregulatory centers. Perioperative temperature control is therefore an issue of high importance. In this study, we aimed to compare the warming effect of underbody and overbody blankets in patients undergoing surgery in the lithotomy position under general anesthesia.

METHODS

From September 2018 to October 2019, 99 patients undergoing surgery for colorectal cancer in the lithotomy position were included in this randomized controlled trial and assigned to the intervention group (underbody blanket) or control group (overbody blanket).

RESULTS

The central temperature was significantly higher in the underbody blanket group than in the overbody blanket group at 90 min after the beginning of the surgery (p = 0.02); also in this group, the peripheral temperature was significantly higher 60 min after the beginning of the surgery (p = 0.02). Regarding postoperative factors, the underbody blanket group had a significantly lower frequency of postoperative shivering (p < 0.01) and a significantly shorter postoperative hospital stay (p = 0.04) than the overbody blanket group.

CONCLUSIONS

We recommend the use of underbody blankets for intraoperative temperature control in patients undergoing surgery in the lithotomy position under general anesthesia. Underbody blankets showed improved rise and maintenance of central and peripheral temperature, decreased the incidence of postoperative shivering, and shortened the postoperative length of hospital stay.

Disorders of Temperature Control: Hypothermia, Part III

Hypothermia, defined as a body core temperature below 35°C, results from exposure to cold, drugs, metabolic dysfunction, or nervous system or skin disorders. The diagnosis and clinical assessment of patients with hypothermia should be based on a thorough knowledge of the characteristic physiologic changes that accompany hypothermia and affect all organ systems. Morbidity and mortality resulting from hypothermia may be reduced when physicians anticipate the well-known complications of hypothermia and carefully rewarm the patient. The rate and method of rewarming must be individualized, taking into account available resources and the patient's cardiopulmonary status and underlying disease.

Postoperative Management of Shivering: A Comparison of Pethidine vs. Ketamine

Background:

One of the unpleasant side effects of general anesthesia is shivering in the process of recovery. It is an involuntary oscillatory mechanical movement that can be classified as clonic movements. These movements can affect one or several groups of skeletal muscles beginning from 5 to 30 minutes after the discontinuation of anesthesia.

Objectives:

We aimed to study ketamine’s effect on shivering after operation compared to pethidine as a way for treatment of postoperative shivering.

Patients and Methods:

In this study, 60 patients who underwent ENT surgery with general anesthesia and had shivering during recovery were randomly divided into two groups of 30 patients each receiving ketamine (0.2 mg/kg IV) and pethidine (0.5 mg/kg).

Results:

There was no statistically significant difference between the shivering intensity in both groups. Only regarding the shivering in the first minute after entering the recovery room, there was an obvious difference between ketamine and pethidine groups which was again not statistically significant (P = 0.07).

Conclusions:

The results of this study showed that ketamine and pethidine are both equally effective in the reduction of postoperative shivering.

Intrathecal Meperidine Plus Lidocaine for Prevention of Shivering during Cesarean Section

Background

Shivering related to spinal anesthesia may interfere with monitoring and is uncomfortable. The aim of the present study was to investigate low-dose intrathecal meperidine for the prevention of shivering after induction of spinal anesthesia in parturients with cesarean section.

Methods

This was a prospective randomized, double-blind, placebo-controlled trial including 100 parturients, of American Society of Anesthesiologists (ASA) physical status I or II, scheduled for elective cesarean section under spinal anesthesia who were randomly assigned to a meperidine (0.2 mg/kg) plus hyperbaric lidocaine (5%, 75 mg, n = 50; group M) group or a placebo plus hyperbaric lidocaine (5%, 75 mg, n = 50; group L) group. Demographic and surgical data, adverse events, and the mean intensity for each parturient were assessed during the entire study period by a blinded observer.

Results

There were no significant differences between the two study groups regarding the demographic and surgical data (P > 0.05). The incidence of shivering during the entire study period significantly decreased in the group of parturients who received intrathecal meperidine (P = 0.04). There were no significant differences in nausea and vomiting between the two groups.

Conclusions

Low-dose intrathecal meperidine (10 mg) is safe and effective in reducing the incidence and severity of shivering associated with spinal anesthesia in parturients with cesarean section.

Postoperative shivering in children and causative factors

BACKGROUND

The aim of this study is to investigate the incidence of shivering in children and to reveal the causative factors as well as any possible clinical implications.

METHODS

This study was conducted on 1507 children who underwent surgery under general anesthesia. The patients were admitted to the postanesthesia care unit after the operation and their body temperatures measured from the tympanic membrane. The type of operation, operative time, method of anesthesia induction, age, and number of cases in which caudal block had been used were recorded.

RESULTS

Of the 1507 children, 53 (3.5%) experienced shivering. The use of intravenous induction agents, age older than 6 years, and prolonged duration of surgery were associated with shivering. The type of the operation and gender had no effect. The frequency of shivering was lower in children who underwent caudal block with a statistical significance (P < 0.05).

CONCLUSIONS

The overall incidence of shivering in children is low (3.5%). Use of intravenous induction agents, age older than 6 years, and prolonged duration of surgery were associated with shivering; prophylaxis is not necessary in children, treatment is given only when shivering occurs.

Postanaesthetic shivering: epidemiology, pathophysiology, and approaches to prevention and management

Along with nausea and vomiting, postanaesthetic shivering is one of the leading causes of discomfort for patients recovering from general anaesthesia. The distinguishing factor during electromyogram recordings between patients with postanaesthetic shivering and shivering in fully awake patients is the existence of clonus similar to that recorded in patients with spinal cord transection. Clonus coexists with the classic waxing and waning signals associated with cutaneous vasoconstriction (thermoregulatory shivering). The primary cause of postanaesthetic shivering is peroperative hypothermia, which sets in because of anaesthetic-induced inhibition of thermoregulation. However, shivering associated with cutaneous vasodilatation (non-thermoregulatory shivering) also occurs, one of the origins of which is postoperative pain. Apart from causing discomfort and aggravation of pain, postanaesthetic shivering increases metabolic demand proportionally to the solicited muscle mass and the cardiac capacity of the patient. No link has been demonstrated between the occurrence of shivering and an increase in cardiac morbidity, but it is preferable to avoid postanaesthetic shivering because it is oxygen draining. Prevention mainly entails preventing peroperative hypothermia by actively rewarming the patient. Postoperative skin surface rewarming is a rapid way of obtaining the threshold shivering temperature while raising the skin temperature and improving the comfort of the patient. However, it is less efficient than certain drugs such as meperidine, clonidine or tramadol, which act by reducing the shivering threshold temperature.

Tramadol for postoperative shivering: a double-blind comparison with pethidine

In most operating and recovery rooms, shivering is controlled by the use of humidifiers, warming blankets, and inhalation of humidified heated oxygen. However, pharmacological control is an effective alternate treatment modality. This randomized, double-blind trial, conducted in 30 ASA Grade 1 or 2 patients, was designed to explore the efficacy of tramadol and pethidine in the treatment of post-anaesthetic shivering. Tramadol is an inhibitor of the re-uptake of serotonin (5-hydroxytryptamine) and norepinephrine in the spinal cord. This facilitates 5-hydroxytryptamine release, which influences thermoregulatory control. We compared the efficacy of tramadol with that of pethidine, presently a widely used drug for the control of shivering. Patients received either tramadol 1 mg/kg or pethidine 0.5 mg/kg intravenously and the grade of shivering, pulse rate, blood pressure and respiratory rate were observed every 10 minutes after injection for one hour Shivering was significantly more likely to have ceased in the tramadol group (12 of 15 versus 4 of 15 cases, P<0.05) at 10 minutes after drug administration and this control was better sustained. No patients receiving tramadol had a recurrence of shivering. It is concluded that intravenous tramadol 1 mg/kg is more effective for the treatment of postoperative shivering than pethidine 0.5 mg/kg.

Control of shivering under regional anesthesia in obstetric patients with tramadol

PURPOSE

Tramadol in a dose of 1 mg x kg(-1) iv is effective in the treatment of shivering after general anesthesia. The current study aimed to investigate (1) whether tramadol was equally effective for shivering under regional anesthesia in obstetric patients and (2) whether effective treatment could be achieved with lower doses.

METHODS

In a randomised, double-blind study, 36 obstetric patients who shivered during Cesarean section under regional anesthesia and who requested anti-shivering treatment were allocated to one of three groups for iv treatment: Group T0.5 received tramadol 0.5 mg x kg(-1) (n = 12), Group T0.25 tramadol 0.25 mg x kg(-1) (n = 13) and Group NS normal saline 0.05 ml x kg(-1) (n = 11). Treatment efficacy was evaluated subjectively by the parturient as no improvement, slight improvement, or marked improvement. The attending anesthesiologist who was blinded also independently noted the time elapsed from treatment to the time shivering subsided. Side effects such as nausea, vomiting or sedation and Apgar scores of the newborn were also noted.

RESULTS

Eighty percent of parturients in Group T0.5 and 92% in Group T0.25 were judged by observers to have shivering controlled compared with 27% in Group NS (P < 0.001). The response rates of Group T0.5 and Group T0.25 were not different. There was no increased incidence of side effects in the treatment groups.

CONCLUSION

We conclude that tramadol iv was effective in the treatment of intraoperative shivering during regional anesthesia for Cesarean section. There was no demonstrable difference in response rate or incidence of side effects between the two doses of 0.5 mg x kg(-1) and 0.25 mg x kg(-1).

Dystrophia myotonica: combined spinal-epidural anaesthesia for caesarean section

Patients with dystrophia myotonica requiring caesarean section pose significant problems for the anaesthetist. This report describes the successful use of a combined spinal-epidural technique for anaesthesia and postoperative analgesia in such a patient.

Postanaesthetic shivering in children

This study was designed to assess the incidence, severity and possible aetiological factors of postanaesthetic shivering in children. Three hundred and seventy-six children undergoing general anaesthesia were enrolled in the study. Tympanic membrane temperatures were recorded pre-operatively and every 15 min postoperatively in the recovery room until discharge to the ward. Also recorded were all anaesthetic data including fluid administration, methods of temperature preservation used, sedation scores and shivering (using a four-point scale). The overall incidence of shivering was 14.4%. Multiple regression analysis identified three factors that were significantly related to shivering: age, the administration of atropine and peri-operative temperature changes. Children who shivered rewarmed faster in the recovery room.

The treatment of postanaesthetic shivering: a double blind comparison between alfentanil and pethidine

It has been postulated that pethidine may mediate its effects on postanaesthetic shivering (PAS) via kappa-opioid receptors. However, clinical evidence indicates that alfentanil, a pure mu-agonist, may also have beneficial effects on PAS. In order to assess whether opioid effects on PAS are effected via kappa receptors, fifty-one patients were randomised to receive alfentanil 250 micrograms (n = 18), pethidine 25 mg (n = 18) or placebo (n = 15) on a double-blind basis for the treatment of established postanaesthesia shivering (PAS). Both drugs proved significantly better in treating PAS than placebo (P < 0.005). Following treatment, blood pressure fell and oxygen saturation increased in patients in the two treatment groups when compared with the control group (P < 0.05). There was a highly significant incidence of reshivering in the alfentanil treated group (P < 0.005). In conclusion, the high incidence of reshivering indicates that alfentanil is unlikely to supercede pethidine in the treatment of PAS, but its initial success rate implies that pethidine's anti-shivering effect is unlikely to be mediated via kappa-opioid receptors.

Propofol and postanaesthetic shivering

Sixty ASA grade 1 unpremedicated patients scheduled for minor elective surgery were randomly allocated to receive general anaesthesia consisting of either propofol-nitrous oxide in oxygen or a conventional technique of thiopentone-isoflurane-nitrous oxide-oxygen. Baseline axillary temperature readings, duration of operation and intra-operative decrease in axillary temperature were similar in both groups. The patients who received propofol-nitrous oxide-oxygen anaesthesia had a significantly lower incidence of postanaesthetic shivering than the control group. A propofol-nitrous oxide-oxygen technique may be preferable when postanaesthetic shivering is deemed undesirable.

Control of post anaesthetic shivering with nefopam hydrochloride in mildly hypothermic patients after neurosurgery

Postoperative shivering may be prevented by maintaining normothermia intraoperatively or it may be treated using specific drugs. The aim of this study was to compare the efficacy of nefopam hydrochloride (nefopam) to that of clonidine and meperidine in patients undergoing elective neurosurgical procedures. Three groups of patients were included in the study. Patients in group A (60) received i.v., at random, 20 mg of nefopam, 50 mg of meperidine or 150 micrograms of clonidine in the immediate postoperative period. The incidence of shivering and the time at which shivering ceased were noted, along with central temperature and main haemodynamic changes. Group B (20) received i.v., at random, either 10 mg of nefopam or saline before awakening from anaesthesia. The effects of nefopam on central temperature, oxygen consumption (Vo2), carbon dioxide production (VcO2), basal metabolic rate (BMR) and energy expenditure (EE) were investigated. Group C (10) received i.v. 20 mg of nefopam during surgery: cerebrospinal fluid pressure (CSFP), cerebral perfusion pressure (CPP) and electroencephalogram (EEG) were monitored. In group A nefopam stopped shivering in 95% of patients when compared to meperidine and clonidine, which were effective in 32% and 40% of patients respectively. In group B, only 10% of patients receiving nefopam had postoperative shivering, Vo2, VcO2 and EE were significantly lower in patients treated with nefopam than those in the control group. No changes in CSFP, CPP or EEG were observed in group C. In conclusion, nefopam seems to be more effective than clonidine or meperidine in quickly suppressing shivering, without producing significant adverse reactions.

A comparison of thiopentone and propofol with respect to the incidence of postoperative shivering

One hundred patients (69 female) undergoing surgical excision of three or more wisdom teeth were randomly allocated to receive either thiopentone or propofol for induction of anaesthesia. Other than the induction agent, the anaesthetic regimen was standardised for all cases. All patients were observed for 15 min after entry into the recovery area to assess the presence and intensity of shivering. Twenty-five patients in the thiopentone group (n = 50) and 11 patients in the propofol group shivered postoperatively (p < 0.005). There was no statistically significant difference in axillary temperature between shivering and non-shivering patients. The use of propofol as an induction agent is associated with a lower incidence of postoperative shivering than thiopentone.

The intensity of postoperative shivering is unrelated to axillary temperature

The relationship between axillary temperature and postoperative shivering was examined in 302 patients who entered one recovery room in the Derbyshire Royal Infirmary over a one-month period. No relationship was found between temperature and the occurrence of shivering, or between conscious level and the occurrence of shivering.

Effects of surgical site and inspired gas warming devices on body temperature during lower abdominal and thoracic surgery

To evaluate the effects of surgical site and inspired gas warming and humidifying devices on body temperature, we studied rectal, tympanic membrane, and esophageal temperature changes in 48 patients. The patients were divided into 4 groups (n = 12), according to surgical site, lower abdominal surgery and thoracic surgery, and according to the warming device used, heat and moisture exchanger (ThermoVent 600) and heated humidifier (Cascade 1). The heated humidifier was controlled to warm inspired gases to about 35 degrees C. All body temperatures fell significantly during surgery. There was no difference in the tympanic membrane and esophageal temperature declines between the two surgical sites, but the decline in rectal temperature was larger in the lower abdominal surgery than in the thoracic surgery. At the end of surgery, all temperatures returned to the value before surgery, and the rectal and tympanic membrane temperatures even exceeded them. There was no difference between the effects of the ThermoVent 600 and Cascade 1. These results suggest that rectal temperature is influenced by the ambient temperature during lower abdominal surgery and that warming and humidifying devices for inspired gases do not prevent, but can restore the decline in body temperature during lower abdominal and thoracic surgery. The heated humidifier showed no advantage over the heat and moisture exchanger in our study.

[Postoperative shivering: analysis of main associated factors]

This study was carried out in 75 female patients, ranked ASA 1 or 2, during recovery from balanced general anaesthesia. It aimed to find out the main determinants of postoperative shivering and its thermal effects. Skin and oesophageal temperature were recorded every ten minutes. Mean skin and body temperatures, and the intraoperative energy balance were calculated. There was no additional source of heating. Shivering was ranked from 0 to 2. Statistical analysis showed that the starting mean core and body temperatures were the only factors correlated with shivering and its intensity, whereas mean skin temperatures, age and opioid doses were not. Between 33.5 and 36.5 degrees C, there was a linear relationship between the oesophageal temperature at the end of anaesthesia and the incidence of shivering. A decrease of 1 degrees C in core temperature increased the probability of shivering by 33%. At 35.4 degrees C, 50% of patients shivered. There was a homogenous group of patients whose oesophageal temperature at the end of anaesthesia was between 35 and 36 degrees C. In this group, there was no significant difference between starting skin temperatures, whether the patient shivered or not. However, the core temperature of those within that group that did shiver returned to normal levels more quickly than in those that did not shiver. These data underlined the essential role played by core temperature at the end of anaesthesia in postoperative shivering and its intensity, as well as the heat producing value of shivering. It would therefore seem logical to prevent postoperative shivering by avoiding intraoperative hypothermia.

Prevention of Postanesthetic Shivering with Intravenous Administration of Aspirin

There have been many reports of postanesthetic shivering (PAS); however, the causes have not been defined clearly, and the reported methods of inhibiting PAS are not always available clinically. In the present study, we assessed the effect of the intravenous administration of aspirin on the prevention of PAS in 62 patients undergoing oral or maxillofacial surgery, anesthetized with enflurane-nitrous oxide. Thirty of the patients were randomly selected, and received intravenous aspirin DL-lysine 900 mg (equivalent to aspirin 495 mg) before the end of surgery. No significant differences were noted in the rectal temperatures between the group given aspirin and the control group. Shivering was observed in 17 of the 32 patients of control group. In contrast, shivering was observed in 5 of the 30 patients who received aspirin. This was a statistically significant difference ( P < 0.01). These data indicate that intravenous administration of aspirin significantly inhibited PAS. The finding suggests that PAS is related to prostaglandin synthesis or to the formation of derivatives of arachidonic acid, since aspirin inhibits both the synthesis of prostaglandins and the formation of derivatives of arachidonic acid.

Postoperative ventilatory and circulatory effects of extended rewarming during cardiopulmonary bypass

Postoperative effects of extended rewarming (ECR) after hypothermic cardiopulmonary bypass (CPB) were studied. All (n = 28) patients were rewarmed to a nasopharyngeal temperature exceeding 38 degrees C before terminating CPB. In 12 patients (control group) the rectal temperature (Tre) was 33.8 +/- 1.7 degrees C (mean +/- sd) at termination of CPB. In sixteen patients (ECR group) rewarming during CPB was continued to a Tre of 36.8 +/- 0.5 degrees C. Postoperative body temperatures, heat content, shivering, oxygen uptake, CO2 production and haemodynamic variables were measured. ECR reduced the heat gain required to complete core rewarming to 665 +/- 260 kJ, compared with 1037 +/- 374 kJ in the control group (p less than 0.01). The incidence of shivering was reduced (p less than 0.05) as well as shivering intensity and duration. In seven non-shivering ECR group patients this coincided with significantly reduced metabolic and ventilatory demands but these improvements were not valid for the group as a whole. The required ventilation temporarily during postoperative rewarming in both groups increased to 250 per cent of the basal need. Extending CPB rewarming (to at least 36 degrees C Tre) was inefficient when used as the sole measure to reduce the untoward effects of residual hypothermia during recovery after cardiac surgery with hypothermic CPB.

Intravenous meperidine for control of shivering during caesarean section under epidural anaesthesia

To determine the efficacy of meperidine in controlling shivering during epidural anaesthesia for Caesarean section, forty-six parturients were studied. After delivery of the infant, shivering patients received either a single dose of intravenous meperidine 50 mg, or saline in a randomized double-blind fashion. Shivering was classified on a scale of 0 to 3 (grade 0 = none, grade 3 = severe shivering that was distressing to the patient and interfered with monitoring). Shivering and other variables were recorded at epidural placement, skin incision, delivery, and 2, 5, 15, 30 and 60 minutes following injection. Administration of meperidine resulted in a significant decrease in both the overall incidence of shivering (87 to 35 per cent, p less than 0.01) and severity of shivering (grade 3:57 to 0 per cent, p less than 0.01), compared with saline (incidence: 87 to 83 per cent, grade 3:57 per cent, no change). This effect was apparent within two minutes of drug injection and persisted throughout the study period. There were no differences in vital signs, oxygen saturation or temperature between groups. The incidence of nausea was similar, although patients receiving meperidine were more drowsy at two and five minutes following injection (p less than 0.01) compared with patients in the saline group. There were no differences in level of consciousness at the later intervals. The mechanism of action of meperidine on shivering remains to be elucidated.

[Humidification of the respiratory tract in anesthesia]

The upper airways humidify, warm and purify the air breathed in. When these are bypassed by an endotracheal intubation catheter, cold dry air goes straight to the bronchi; this leads to local and generalized changes, which are all the more pronounced the longer the intubation lasts. Drying of the tracheobronchial mucosa leads to an early decrease in mucus production, with an increase in its viscosity, a progressive arrest of ciliary function with, finally, a destruction of the vibratory cilia. These lesions create a build-up of thick mucus which hinders humidification of the gas flow and increases bronchial resistances. The disturbed VA/Q relationship leads to a decreased secretion of surfactant. The usual loss of water by way of the lungs is about 30 mg.l-1 of air. Evaporation of this water uses up calories. Most authors suggest that, so as to compensate for the heat and water loss, inhaled gases should be warmed to between 25 and 30 degrees C and be saturated with water to 100%, i.e. 23-30 mg water per litre of air. The water and heat loss can be reduced by using either partial or total rebreathing of expired gases, or a device for heat and moisture exchange, or a humidifier. The most efficient circuits are those which include a soda lime canister. They can be made even more efficient by using different devices. Although this humidification is sufficient for large tidal volumes and a surrounding temperature greater than 22 degrees C, it is not enough for Bain's circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of intraoperative hypothermia during abdominal surgery

Heat balance and core and skin temperatures were studied in 111 patients during abdominal surgery. In minor surgical procedures the effects of heating of inspired humidified gases (n = 23) and of a heating mattress (n = 21) were compared with the conditions in an unwarmed control group (n = 24). These two methods were about equally effective in preserving total body heat, although the major effect of the heating mattress was to conserve heat which had been redistributed to the surface, and such heat could subsequently be lost to the environment. During major abdominal surgery 18 unwarmed control patients were compared with patients (n = 25) provided with a heat supply. The combined measures of heated humidified inspired gases, a heating mattress, insulation by a heat-reflecting blanket, warming of all infusions and transfusions and a warm operating room were all needed to balance the great heat losses during the major surgical procedures. With such massive heat supply it was possible to prevent heat loss and a fall in core temperature.

Shivering following cardiac surgery: hemodynamic changes and reversal

The effects of shivering on hemodynamics and systemic oxygenation, as well as the effectiveness of therapeutic interventions in decreasing shivering and increasing mixed venous oxygen saturation, were studied. Thirty adult patients undergoing cardiopulmonary bypass with systemic hypothermia were observed for 1 1/2 to 5 hours postoperatively for signs of shivering associated with a simultaneous decrease in oxygen transport. Systemic and pulmonary hemodynamic measurements were made, blood temperature and mixed venous oxygen saturation were monitored via the pulmonary arterial catheter, and oxygen consumption and delivery were calculated. Shivering was graded by a single investigator on scale of 0 to 4, with 0 = no shivering and 4 = continuous violent muscle activity. Therapy was instituted when shivering reached grade 4 or when SvO2 decreased to less than two thirds of its value on arrival in the intensive care unit (ICU). Patients were randomly assigned to receive either morphine sulfate, 5 to 10 mg, or meperidine, 25 to 50 mg intravenously (IV), followed by the other narcotic if the initial drug failed to improve SvO2 or decrease shivering within ten minutes. The end-point for successful treatment was a return of SvO2 to within 5% to 10% of its value upon arrival in the ICU or a cessation of shivering that did not recur within 45 minutes. Twenty of the thirty patients shivered sufficiently to decrease SvO2 by more than one third of its initial value, thus requiring pharmacologic therapy. As shivering increased from a score of 0.8 +/- 1.1 to 3.4 +/- 0.9, SvO2 decreased from 74 +/- 6% to 57 +/- 12%.(ABSTRACT TRUNCATED AT 250 WORDS)

An investigation of factors affecting postoperative rewarming of adult patients

Aural canal temperature was measured for one hour after arrival in the recovery room in 200 adult patients who underwent one of the following types of major surgery: abdominal, pelvic, vascular, orthopaedic or prostatic. One group of 100 patients was studied in the recovery room of Hammersmith Hospital which was not equipped with a controlled system for constant ventilation and humidification, while the other 100 patients were studied in the recovery room of Edgware General Hospital, which had a constant ambient temperature and controlled relative humidity with 20 air changes/hour. The rate of rewarming was found to be similar in both groups. Within the range of ambient temperatures and relative humidities measured, patients over 60 years of age rewarmed more slowly than did patients under 60 years (p less than 0.05). General anaesthesia was associated with significantly faster rewarming than was local anaesthesia (p less than 0.01).

Anesthesia for neonatal foals

A brief discussion of those aspects of neonatal physiology that pertain to anesthetic risk and selection of anesthetic techniques is followed by discussion of suggested techniques for anesthetic management in healthy foals. Preoperative preparation and management of foals with selected serious surgical conditions are also considered.

Peroperative hypothermia

Heat loss during anesthesia and operation and subsequent hypothermia will increase the postoperative oxygen demand and may endanger patients with restricted cardiopulmonary reserves. Forty patients scheduled for intra-abdominal aortic surgery and 40 patients scheduled for peripheral vascular surgery on the lower limbs were investigated using a warming blanket, humidified heated inspired anesthetic gases at 37-40 degrees C, or both these methods together. A fourth group of patients received no active warming. A warming blanket used alone gave no protection against hypothermia when compared with no active warming. In the abdominal surgical group, there was a steady fall in temperature throughout the operation if no warming method was employed. In this group the use of humidified, heated inspired gases was significantly better than no treatment after 2 h of anesthesia (P less than 0.05). The combination of humidified and heated inspired gases and a warming blanket gave significantly better heat preservation after 40 min (P less than 0.05). Patients undergoing peripheral vascular surgery had similar but smaller drops in temperature with the different types of warming procedures employed. The differences in temperature between the intra-abdominal and extra-abdominal operations were statistically significant after 3 h (P less than 0.05).

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.

Anaesthetic considerations for microsurgical repair of limbs

With the advent of surgery under the operating microscope microvascular surgical techniques requiring prolonged anaesthesia have greatly increased in number. Local anaesthetic techniques, whilst often producing excellent surgical conditions, are limited by the duration of action of the anaesthetic agents and by the ability of the patient to remain still, often in uncomfortable positions, for periods of up to twenty hours. The use of indwelling catheters as a means of prolonging the duration of nerve blocks is discussed along with methods of sedation or general anaesthesia to enable the patient to tolerate lengthy surgical intervention. Present general anaesthetic techniques may not be ideally suited to long surgical procedures. The problems and possible alternatives are discussed. Sympathetic ganglion blockade, intravenous regional blockade and systemic vasodilator therapy are discussed as a means of improving the success rate of these procedures. The general principles of patient management such as fluid balance, temperature control, patient positioning and control of the operating room environment assume a much greater significance when related to the provision of prolonged general anaesthesia, whilst the effect of extended periods of work on operating personnel must also be considered.

Postoperative spasticity and shivering. A review with personal observations of 500 patients

The cause of postoperative shivering is not known. The theories and possible remedies are reviewed. Five hundred patients were observed for the possible effect of lissive doses of gallamine, and of analgesic or benzodiazepine premedication. Diazepam premedication appeared to reduce the incidence of post-halothane shivering.