POSOPERATIVE SHVERING AND HYPOXAEMIA AFTER HALOTHANE, NITROUS OXIDE AND OXYGEN ANAESTHESIA

"The magnitude and associated factors of intraoperative shivering after cesarean section delivery under Spinal anesthesia'': A cross sectional study

Background

Shivering is an involuntary, spontaneous, and repetitive contraction of the skeletal muscle and increases patients’ discomfort, oxygen-consuming, wound infection; increased surgical bleeding, and morbid cardiac events. The aim of this study was to determine the magnitude and associated factors of intraoperative shivering after cesarean section delivery

Methodology

An institution-based cross-sectional study was conducted. A total of 326 willing patients were included in the study after obtaining ethical consent and we have used consecutive sampling techniques. Axillary temperature was recorded preoperatively and in the intra-operative period every 5 min. Descriptive statistics, cross-tabs, and binary logistic regression analysis were performed to identify the association shivering and independent variables. The strength of the association was presented using an adjusted odds ratio with a 95% confidence interval and a p-value<0.05 was considered as statistically significant.

Results

The overall incidence of intraoperative shivering after cesarean section delivery under spinal anesthesia was 51.8% (95% CI: 46.3, 57.1). The majority of the patients who developed shivering were after 20 min of spinal anesthesia. In this study body temperature, mean arterial pressure of the patient, and duration of surgery were significantly associated with shivering.

Conclusion

In this study duration of surgery, hypothermia and hypotension were the independent associated risk factors for intraoperative shivering.

•

The incidence of post spinal anesthesia shivering after cesarean section delivery was 51.8% in the study area.

•

More than 45% patients were developed Grade III shivering.

•

Hypothermia, hypotension and duration of surgery were affected shivering.

•

Most patients were developed shivering after 20 min of spinal anesthesia.

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.

Comparison of the efficacy of a forced-air warming system and circulating-water mattress on core temperature and post-anesthesia shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia

Background

In the present study, we compared changes in body temperature and the occurrence of shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia during warming with either a forced-air warming system or a circulating-water mattress.

Methods

Forty-six patients were randomly assigned to either the forced-air warming system (N = 23) or circulating-water mattress (N = 23) group. Core temperature was recorded using measurements at the tympanic membrane and rectum. In addition, the incidence and intensity of post-anesthesia shivering and verbal analogue score for thermal comfort were simultaneously assessed.

Results

Core temperature outcomes did not differ between the groups. The incidence (13.0 vs 43.5%, P < 0.05) and intensity (20/2/1/0/0 vs 13/5/3/2/0, P < 0.05) of post-anesthesia shivering was significantly lower in the forced-air system group than in the circulating-water mattress group.

Conclusions

The circulating-water mattress was as effective as the forced-air warming system for maintaining body temperature. However, the forced-air warming system was superior to the circulating-water mattress in reducing the incidence of post-anesthesia 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.

Pre-induction low dose pethidine does not decrease incidence of postoperative shivering in laparoscopic gynecological surgeries

OBJECTIVES

The incidence of shivering in patients undergoing a laparoscopic procedure is stated to be about 40%. A majority of laparoscopic gynecological procedures are taken up on an outpatient basis. Postoperative shivering may delay hospital discharge and is a common cause of discomfort in patients recovering from anesthesia.

AIMS

To determine the effect of pre-induction, low-dose pethidine on postoperative shivering in patients undergoing laparoscopic gynecological surgeries.

SETTING AND DESIGN

Sixty females between 25 and 35 years of age, of American Society of Anesthesiologists (ASA) class 1 and 2, were randomly divided into three groups of 20 patients each. Group I and II patients received i.v. pethidine 0.3 mg/kg and 0.5 mg/kg, respectively, while Group III received i.v. 0.9% normal saline just before induction of general anesthesia. Temperature of the Operating Room and the Post Anesthesia Care Unit was standardized and all fluids given during the study period were warmed to 37°C.

MATERIALS AND METHODS

Temperature, measured with a tympanic membrane probe, was recorded preoperatively, after induction of anesthesia, on arrival at the Post Anesthesia Care Unit, and postoperatively at 15 minutes and 30 minutes. Shivering was graded (0 - 4 scale) at arrival of the patients to the PACU and every five minutes thereafter, up to 30 minutes.

STATISTICAL ANALYSIS

ANOVA, Chi-square test, Kruskal-Wallis ANOVA and Mann-Whitney U tests were used. A P-value of less than 0.05 was considered significant.

RESULTS

Core body temperatures were statistically insignificant between groups at pre-induction, post-induction, and in the PACU (P > 0.05). At the end of surgery, shivering was present in 18 patients (30%). In groups I, II, and III, six (30%), three (15%), and nine (45%) patients shivered, respectively. The differences in incidence and grading of shivering among groups was found to be statistically insignificant (P > 0.05). The core body temperature of shiverers and non-shiverers were compared. In the PACU at 0, 15, and 30 minutes, the temperature among shiverers was significantly lower than that in the non-shiverers. Rescue drug i.v. pethidine 20 mg was given to patients with shivering grade ≥2. None of the patients had shivering after 10 minutes.

CONCLUSIONS

Prophylactic pre-induction, low-dose pethidine does not have major role in preventing postoperative shivering.

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.

Prolonged anesthetic recovery

Failure to awaken, delayed awakening, and blunted responsiveness following anesthesia constitute a continuum which must be recognized, diagnosed accurately, and responded to appropriately. One must determine whether it is a normal recovery for this animal or a pathological delay. A delayed recovery results in continued depression of many organ systems. The possible etiologic factors, some obvious, others quite obscure, must be considered quickly to provide the patient with the best possible care. Diminished responsiveness is usually the result of a complex interaction between multiple factors. A systematic approach to treatment first begins by ensuring cardiac output, oxygenation, ventilation, and supportive care in all patients. Then consider the potential causes for prolonged recovery and either rule them out or treat them. First consider the potential causes for central nervous system depression. Several commonly encountered medical conditions enhance sensitivity to or decrease the elimination of anesthetic and sedative agents. The astute clinician will be aware of the medical condition and its impact on anesthetic drug effect and elimination to avoid prolonged recoveries.

Hypoxemia decreases the shivering threshold in rabbits anesthetized with 0.2 minimum alveolar anesthetic concentration isoflurane

Shivering has been proposed as an etiology of postoperative hypoxemia. The difficulty with this theory is that hypoxemia inhibits shivering in unanesthetized cats, rats, and humans. However, anesthesia inhibits many protective reflexes, including the ventilatory response to hypoxemia. We therefore tested the hypothesis that arterial hypoxemia fails to inhibit shivering in lightly anesthetized rabbits. Rabbits were intubated and instrumented during exposure to surgical concentrations of anesthesia, and anesthesia was then maintained with 0.2 minimum alveolar anesthetic concentration isoflurane. The core was cooled at a rate of 2-3 degrees C/h by perfusing water at 10 degrees C through a colonic thermode. Core temperatures were recorded from the distal esophagus. Sustained, vigorous shivering was considered physiologically significant. The core temperature that triggering significant shivering identified the thermoregulatory threshold for this response. Arterial blood was sampled for gas analysis at the shivering threshold in each rabbit. Hypoxemia linearly reduced the shivering threshold from 36.7 degrees C at 130 mm Hg to 35.4 degrees C at 50 mm Hg (threshold = PaO2.0.019 + 34.3; r2 = 0.49). We failed to confirm our hypothesis: instead, even mild hypoxemia reduced the shivering threshold >1 C. A 1 C decrease in the shivering threshold is likely to prevent or stop most postoperative shivering because it exceeds the reduction produced by many effective anti-shivering drugs. These data do not support the theory that shivering causes postoperative hypoxemia.

IMPLICATIONS

Shivering has been proposed as an etiology of postoperative hypoxemia. Our data, in contrast, show that mild hypoxemia inhibits shivering. Shivering is thus unlikely to be a cause of postoperative hypoxemia.

[Efficacy of ketanserin on postanesthetic shivering]

OBJECTIVE

To evaluate the clinical and electromyographic (EMG) effects of ketanserin (K), a serotoninergic receptor antagonist (5-HT2), on postoperative shivering (POS).

STUDY DESIGN

Prospective, randomised, double-blind study.

PATIENTS

Fifty ASA class 1 and 2 patients with major clinical postoperative tremor were studied.

METHODS

POS was assessed clinically (0 = nil, 1 = moderate, 2 = severe). Inclusion criterion was a POS of 2 at admission in the recovery room. The mean arterial blood pressure, rectal temperature, SpO2 were recorded at admission (T0) and subsequently at T5, T10, T15, T30 and T60 minutes. Either 10 mg of K (n = 25) or a corresponding volume of a placebo (P) (n = 25) were intravenously injected. The EMG activity of the deltoid and quadriceps muscles was recorded continuously. Blood lactic acid concentration was measured at the end of POS. Results are expressed as mean +/- SEM. Parametric values were analysed with unpaired Student's t-test, and nonparametric values with chi 2 analysis. P < 0.05 was accepted.

RESULTS

Demographic data, duration of anaesthesia, postoperative temperature, oxygen saturation, blood pressure and blood lactate concentration were similar between groups. The POS duration in the K group was significantly shorter than in the P group: 8.8 +/- 1.5 min and 15.5 +/- 1.5 min respectively (P < 0.01). The number of patients in the K group experiencing POS at T5 and T10 was significantly lower, when compared with those who had received the P (P < 0.05).

CONCLUSION

At a dose of 10 mg, K administered in patients with POS during recovery, reduced significantly the duration and intensity of the shivering without noticeable side effects. This study suggests that this 5-HT2 antagonist is an efficient therapeutic tool for POS in adults.

Appropriate thermal manipulations eliminate tremors in rats recovering from halothane anesthesia

Tremors are common in mammals emerging from anesthesia. To determine whether appropriate thermal manipulations immediately before emergence from anesthesia are sufficient to eliminate these tremors, electroencephalographic (EEG) and electromyographic (EMG) activities, hypothalamic temperature (Thy), and O2 consumption were monitored in 12 rats recovering from halothane anesthesia under three thermal regimes. EEG and EMG activities were recorded throughout anesthesia and served as feedback signals for controlling anesthetic depth. During anesthesia, Thy was either 1) allowed to fall to 32-34 degrees C, 2) maintained at 37-39 degrees C, or 3) allowed to fall to 32-34 degrees C and then raised to 37-39 degrees C. When hypothermic on emergence from anesthesia, all of the animals exhibited postanesthetic tremors that persisted until Thy values returned to normothermia. None of the animals expressed postanesthetic tremors when normothermic on emergence from anesthesia. In addition, the time between emergence from anesthesia (as determined by EEG/EMG parameters) and the initiation of coordinated motor activities was significantly decreased in the normothermic animals.

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.

Isoflurane and sevoflurane produce a dose-dependent reduction in the shivering threshold in rabbits

All general anesthetics markedly impair thermoregulatory responses; nonetheless, sufficient hyperthermia or hypothermia will trigger most protective reflexes. Shivering, however, remains an exception among thermo-regulatory responses: it is common during postanesthetic recovery, but is rare at typical anesthetic concentrations. This observation suggests that general anesthesia impairs shivering far more than other thermoregulatory defenses. Accordingly, we tested the hypothesis that low concentrations of isoflurane and sevoflurane would virtually obliterate shivering. Japanese white rabbits were anesthetized with isoflurane or sevoflurane at end-tidal concentrations of 0.2, 0.3, and 0.4 minimum alveolar anesthetic concentration (MAC) (n = 6 in each group); the normal core temperature for these rabbits is approximately 39 degrees C. Core temperatures were subsequently reduced by a water-perfused thermode positioned in the colon. The core temperature triggering shivering identified the threshold for this response. Five of the six rabbits given 0.2 MAC isoflurane shivered at a mean core temperature of 36.3 +/- 0.3 degrees C (mean +/- SD), and one rabbit failed to shiver at a minimum core temperature of 35.0 degrees C. Four of the six rabbits given 0.3 MAC isoflurane shivered at a mean core temperature of 36.2 +/- 0.6 degrees C, and two of these rabbits failed to shiver at a minimum core temperature of 35.0 degrees C. However, no rabbit given 0.4 MAC isoflurane shivered, even at minimum core temperatures of 35.0 degrees C. All of the rabbits given 0.2 MAC sevoflurane shivered at a mean core temperature of 36.6 +/- 0.7 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of different end-tidal volatile agent and carbon dioxide concentrations upon the incidence of postoperative shivering

Sixty patients (47 female) undergoing surgical excision of three or more wisdom teeth were randomly allocated into three groups with differing end-tidal carbon dioxide and volatile agent concentrations during maintenance of anaesthesia. The anaesthetic techniques employed were identical in all other respects. All patients were observed for 10 min after arrival in the recovery area to assess the presence and severity of shivering, axillary temperature and oxygen saturation. There were no significant differences in axillary temperatures between groups or between shivering and non-shivering patients, although there was a significant difference (p = 0.001) in duration of anaesthesia between shivering and non-shivering patients. There was no significant difference between groups with respect to the incidence of shivering (p = 0.96).

Post-anaesthetic shaking

Although shaking in the post-anaesthetic period is common, the cause of this phenomenon is obscure. Many predisposing factors have been identified, but the medical treatments and measures of care for patients with post-anaesthetic shaking are as controversial as the causes.

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.

Six months of shivering in a district general hospital

Of 2595 patients admitted to a recovery room in Derbyshire Royal Infirmary over a 6-month period, 164 (6.3%) shivered postoperatively. Data regarding the anaesthetic techniques to which these patients had been subjected were gathered from the Derby Anaesthetic Audit System. Subsequent analysis demonstrated the importance of a number of factors that led to shivering, including male gender, anaesthetic techniques involving spontaneous ventilation, and anticholinergic premedication. The administration of pethidine, alfentanil or morphine intra-operatively reduced the incidence of shivering postoperatively.

Doxapram after general anaesthesia. Its role in stopping shivering during recovery

A group of patients who developed postoperative shivering after receiving inhalational anaesthesia were assigned, at random, to receive either doxapram or a placebo under double-blind conditions. A significantly higher proportion of patients stopped shivering after being given doxapram than after the placebo.

Anesthetic complications in the horse

The basis for management of all complications is early recognition, preparation, and a problem-solving approach. Some anesthetic complications, such as equipment malfunction and injuries from endotracheal intubation or misplaced drug injections, are common to all animals and can be prevented almost entirely by careful management. Other problems, such as pulmonary dysfunction and cardiovascular depression, seem to occur more often in healthy horses than in healthy members of other domestic species. Postoperative myopathy-neuropathy, sometimes a devastating complication, seems to be peculiar to the horse, and its incidence has been linked to hypotensive inhalant anesthesia. Careful positioning and padding, monitoring of anesthetic depth, and treating of cardiovascular depression may prevent most cases of postanesthetic myopathy. Idiosyncratic drug reactions, such as MH, are entirely unpredictable and can be rapidly fatal unless recognized early and treated vigorously and specifically.

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.

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).

Adverse effects of hypothermia in postoperative patients

The effect of intraoperative and postoperative temperature on morbidity, mortality, and other clinical risk factors was evaluated in 100 consecutive general surgical patients admitted postoperatively to a surgical intensive care unit. Hypothermia (temperature less than 97 degrees F) was present in 77 percent of the patients intraoperatively, in 53 percent at the end of surgery, and in 21 percent at 4 hours. Mortality was increased with patient age greater than 55 years, emergency surgery, operative blood pressure less than 100 mm Hg, operative fluid requirements greater than 1,500 ml/hour, temperature less than 97 degrees F at 2, 4, and 8 hours postoperatively, and presence of postoperative complications. Intraoperative fluid requirements were significantly greater for patients with mortality risk factors. Patients over 55 years of age were more often hypotensive and hypothermic than younger patients, but mortality was increased only for patients less than 55 years of age with a temperature of less than 97 degrees F at 8 hours or an operative blood pressure of less than 100 mm Hg. Mortality after general surgical procedures is increased with operative hypotensive and prolonged postoperative hypothermia. Hypothermic patients with mortality risk factors should be aggressively rewarmed postoperatively.

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.

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.

Morphine and postoperative rewarming in critically ill patients

Morphine sulfate (MSO4) has been demonstrated to attenuate the stress response. MSO4 might be useful in minimizing the stress associated with the perioperative period, particularly that due to awakening from anesthesia and rewarming. Two groups of critically ill patients who developed hypothermia (35.8 degrees C) during a surgical procedure were studied. The control group was observed during routine medical management. Group II received 1 or 4 mg/kg MSO4 followed by an infusion of 0.2 or 0.5 mg/kg/hr. During the postoperative rewarming period the control group patients demonstrated a major increase in metabolic demand and myocardial work. In group II patients the infusion of MSO4 resulted in a lower metabolic rate. This was associated with a significantly longer rewarming time and a significant reduction in shivering, heat loss, heart rate, mean arterial pressure, and rate-pressure product. Infusion of MSO4 in critically ill patients during the perioperative period suppressed metabolic demands and myocardial work while preserving cardiovascular function.

Anaesthesia for patients undergoing prolonged reconstructive and microvascular plastic surgery

The anaesthesiological problems related to prolonged reconstructive plastic surgery in 22 patients were investigated in retrospect. Surgery consisted mainly of reconstructions, including microvascularization (7 emergency reimplantations, 15 plastic reconstructions), and the duration of the balanced anaesthesias varied between 5 h 10 min and 15 h 35 min. As the patients were relatively young and healthy, no serious cardiovascular complications occurred. Blood loss was intentionally replaced with dextran, in most instances, and in a group of 15 elective patients, mean haematocrit level decreased from 0.41 to 0.31 during surgery. In about half of the material, the central temperature was monitored; it remained within 35.8-38 degrees C. In the longest anaesthesia (15 h 35 min) the temperature stayed within 0.4 degrees C, the patient placed on a heating mattress. In 2 patients, transient paresis of the muscles of the hand, which was exposed and abducted for i.v. infusion and blood pressure recording, was observed. A questionnaire was sent to the patients and 19 of 20 responded. The predominant subjective complaint was nausea, while sensations following catheterization of the bladder were also a common untoward recollection. One patient developed laryngeal oedema after extubation and about a third experienced breathing difficulties on awakening from the anaesthesia. Postoperative pain appeared not to be a significant problem.

Hypoxaemia in elderly patients suffering from fractured neck of femur

The purpose of this study was to assess the degree and frequency of hypoxaemia in elderly patients with fractured neck of femur and to note the effect of manipulation and internal fixation on these measurements. Twenty-seven patients aged between 44 and 93 were studied for 5 days after the fracture and for 5 days after surgery. The fractures were treated by internal fixation under either general anaesthesia or spinal analgesia. The arterial oxygen tension following the fracture but before surgery was low relative to the ages of the patients, and the arterial carbon dioxide tension was low in twenty-five out of twenty-seven patients. There was also a significant increase in the dead space/tidal volume ratio (VD/VT) and the alveolar-arterial oxygen tension difference, (A--a)DO2 in eight out of nine patients in the first 5 days following the fracture. The mean arterial oxygen tension was still reduced up to 5 days postoperatively. The VD/VT ratio returned to normal postoperatively although the (A-a)DO2 remained elevated. The haemoglobin and platelet levels following the fracture and before surgery were low, although not remarkably so, and there was no significant change post-operatively. There were no significant changes in the electrocardiograph or the chest radiographs. These results and their implications are discussed.