Comparison between alfentanil, pethidine and placebo in the treatment of post-anaesthetic shivering.

We have compared the effects of pethidine, alfentanil and placebo in the treatment of post-anaesthetic shivering. Ninety patients who shivered after routine surgery were allocated randomly to receive normal saline (n = 30), alfentanil 250 micrograms (n = 30) or pethidine 25 mg (n = 30). After 10 min, 26 patients had stopped shivering in the pethidine group which was significantly more than the incidence in the two other groups (placebo = 7; alfentanil = 12) (P < 0.0002). Alfentanil was not significantly different from normal saline in affecting shivering. We conclude that alfentanil 250 micrograms was not effective in the treatment of post-anaesthetic shivering.

The minimum effective doses of pethidine and doxapram in the treatment of post-anaesthetic shivering.

This study was designed to find the minimum effective doses of doxapram and pethidine to stop post-anaesthetic shivering. Two hundred and twenty healthy patients who shivered following routine surgery were allocated randomly to receive one of 10 doses of doxapram (0.18, 0.23, 0.29, 0.35, 0.41, 0.47, 0.7, 0.93, 1.17 and 1.4 mg.kg-1), one of five doses of pethidine (0.12, 0.18, 0.23, 0.29 and 0.35 mg.kg-1) or saline. Probit analysis demonstrated that the number of patients who stopped shivering with doxapram was independent of the amount of drug given in this dose range. The lowest dose of doxapram (0.18 mg.kg-1) was significantly more effective than placebo (p < 0.01). For pethidine there was a dose-dependent effect on shivering to a maximum of 95% of patients successfully treated with 0.35 mg.kg-1. We conclude that 0.35 mg.kg-1 of pethidine is the minimum dose required to treat post-anaesthetic shivering effectively. We also conclude that 0.18 mg.kg-1 of doxapram is as effective as 1.4 mg.kg-1 in the treatment of post-anaesthetic shivering. Further study is required to find the minimum effective dose of doxapram.

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).

An assessment of morphine requirement after wisdom tooth extraction under general anaesthesia.

The use of morphine delivered by a patient-controlled analgesia system was studied in 20 patients who had undergone surgical extraction of three or four wisdom teeth as inpatients. Whilst 64.3% of the patient requests were made in the first 8 postoperative hours, use of the system continued throughout the night in the majority of patients. The implications for analgesic regimens in day-case surgery are discussed.

The characteristics of the inhibition of serum cholinesterase by metoclopramide.

The inhibition of serum cholinesterase by metoclopramide has been previously characterised in vitro at high dilution of the enzyme. We examined the effect of varying enzyme dilution over a range of 1000 fold dilution, and assay temperature at 25 degrees C and 37 degrees C on the fractional inhibition of enzyme activity by metoclopramide. Neither enzyme concentration nor reaction temperature affected this fractional inhibition. Concentrations of metoclopramide producing 50% inhibition of enzyme activity were in the range 1.0-1.9 x 10(-6) M. Lineweaver-Burk analysis of the enzyme reaction suggests that the pattern of this inhibition is competitive.

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.

Anticholinergic premedication influences the incidence of postoperative shivering.

We studied 225 healthy adult patients undergoing ENT, dental or orthopaedic surgery; they were allocated randomly to receive one of three different premedications, all given i.m. 1 h before operation. Group 1 received morphine 0.15 mg kg-1 and metoclopramide 10 mg; group 2 received morphine 0.15 mg kg-1 and glycopyrronium 5 micrograms kg-1; group 3 received morphine 0.15 mg kg-1 and hyoscine 5 micrograms kg-1. Patients who were premedicated with an anticholinergic had a significantly greater incidence and severity of postoperative shivering than those in the metoclopramide group. There was no difference in core temperature between patients who shivered and those who did not, either before or during the shivering episode. Shivering did not cause any clinically significant changes in heart rate, arterial pressure, ventilatory frequency or oxygen saturation. As this effect occurred with both glycopyrronium and hyoscine, it suggests that the mechanism by which postoperative shivering is influenced is peripheral to the central nervous system.

Double-blind comparison between doxapram and pethidine in the treatment of postanaesthetic shivering.

Sixty patients who shivered after routine surgery under general anaesthesia were allocated randomly to receive normal saline (n = 20), doxapram 1.5 mg kg-1 (n = 20) or pethidine 0.33 mg kg-1 (n = 20). Both doxapram and pethidine were effective in treating postoperative shivering 2-3 min after i.v. administration. In the group who received normal saline, 15 patients were still shivering 10 min after treatment, whilst in the doxapram group only three patients were shivering at that time. In the pethidine group, all patients had stopped shivering by 7 min after treatment. We conclude that both doxapram and pethidine were effective in the treatment of postoperative shivering.

Postoperative shivering.

Shivering is common during recovery from anaesthesia. Factors in the aetiology include the use of volatile anaesthetic agents, prolonged anaesthesia, gender and age. The relationship between postoperative shivering and thermoregulation is not clear. Management should include measurement of the patient's temperature.

Repetitive elastance measurement as a means of recording pharmacological responses in vascular smooth muscles.

We describe a method of recording pharmacological responses in isolated arterial segments, based on the direct measurement of vascular wall elastance. The segment outflow is intermittently occluded, and the elastance determined from the subsequent pressure-flow relationship. Since the measurement cycle can be repeated 12 times per minute, rapid pharmacological responses can be studied. The method is capable of demonstrating a sigmoid dose-response relationship to noradrenaline added to the perfusate.

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.

Radiographic study of intercostal nerve blockade in healthy volunteers.

The spread of solutions injected to the intercostal space was studied in 10 healthy volunteers. Up to 20 ml of a 50:50 mixture of local anaesthetic solution and a radiopaque dye was injected through a modified extradural catheter placed in an intercostal space at the posterior angle of the rib. Radiographic films demonstrated spread by an extrapleural route into adjacent intercostal spaces and this was confirmed by the occurrence of analgesia in the corresponding dermatomes. The relevance of these results to clinical practice is discussed.