Epidural anaesthesia and analgesia do not affect energy expenditure after major abdominal surgery.

Our objective was to determine the effect of perioperative epidural anaesthesia and analgesia on the increase in energy expenditure which accompanies major elective abdominal surgery in a prospective, randomized study. Eight patients undergoing elective resections of the colon and/or rectum received general anaesthesia alone (nitrous oxide, oxygen, and isoflurane, supplemented with intravenous fentanyl to a maximum of 10 micrograms.kg-1), and 12 patients received perioperative epidural anaesthesia and analgesia using lidocaine (carbonated lidocaine 2% with epinephrine 1:200,000, 20 ml over 30 min) and morphine (preservative-free morphine 0.10 mg.kg-1 after catheter insertion and 0.05 to 0.10 mg.kg-1 every 12 hr as needed until the morning following surgery) via a lower lumbar catheter in addition to general anaesthesia. Respiratory gas exchange was measured using a metabolic cart and canopy system early on the morning of surgery, six hours postoperatively, and on the first and second postoperative mornings. Parenteral analgesic administration (P < 0.001) and visual analogue pain scores (P < 0.05) were lower in the patients receiving epidural anaesthesia and time to first parenteral analgesia was longer (P < 0.005). Oxygen consumption, carbon dioxide production, and energy expenditure increased after surgery (all P < 0.001) but were very similar in the two groups (all P > or = 0.8) before and after surgery. Despite substantial effects on postoperative pain, we conclude that oxygen consumption and energy expenditure following major abdominal surgery are not diminished by perioperative epidural anaesthesia and analgesia.

The prevalence and impact of pain after day-care tubal ligation surgery.

Empirical data from controlled studies using standardized, reliable measures on the amount and quality of pain after laparoscopic tubal ligation and the consequences of this pain on the activities of daily living are extremely scarce. In a study of 54 women admitted to a day-care unit for this procedure, validated measures were utilized to assess the incidence, intensity and duration of pain after tubal ligation (McGill Pain Questionnaire) and the impact of pain on the activities of daily living (Modified Functional Assessment Inventory). Psychological measures (Brief Symptom Inventory, Kranz Health Opinion Survey, and the State-Trait Anxiety Inventory) were employed to test their use as possible predictors for pain, analgesic usage and the time taken to resume a normal activity level after tubal ligation surgery. The results showed that pain is a significant problem after tubal ligation although pain rating scores over the 7-day study period were lower than those reported after major abdominal surgery. Eighty-five percent of our sample reported that pain and/or fatigue impacted on their recovery and contributed to an average delay of return to normal activity level of 4.4 days, not including the day of surgery. The psychological measures did not prove to be strong predictors of postoperative pain, time of return to normal activity level or analgesic usage. The most powerful predictor of return to normal activity was the total amount of pain experienced, as measured by the McGill Pain Questionnaire, during the 7 day post-operative period.

Measuring gastric contents during general anaesthesia: evaluation of blind gastric aspiration.

Various medications have been reported to decrease gastric content volume and thus risk for pulmonary aspiration. The majority of studies have used blind gastric tube aspiration of stomach contents as the method of measuring the volume of gastric contents. This study evaluated the accuracy of this method by first measuring gastric content volume using blind gastric aspiration and then aspirating residual content in the stomach, using a visually guided flexible fiberoptic gastroscope. Ten obese patients undergoing elective surgery were studied. Gastric contents were collected using a multi-orificed gastric tube and blind aspiration. Immediately after this was completed, residual gastric volume was collected using a visually guided gastroscope. The sum of these two aspirate volumes (true total gastric volume) was statistically compared with the blind aspirate volume. The blind aspirate volume underestimated true total gastric volume by an average of 14.7 ml and was significantly different from true total gastric volume (p less than 0.05). Blind gastric aspiration was thus demonstrated only to approximate true gastric volume. Its use to measure precisely gastric volume cannot, therefore, be recommended.

Naloxone infusion after prophylactic epidural morphine: effects on incidence of postoperative side-effects and quality of analgesia.

There have been conflicting reports of the value of naloxone infusions to prevent the side-effects associated with epidural morphine. In our study, 29 patients undergoing thoracotomies for pulmonary surgery received epidural morphine (0.1 mg.kg-1) shortly after induction of anaesthesia. One hour after arrival in the Recovery Room, one of four naloxone bolus and infusion sequences was administered: saline bolus followed by saline infusion; 0.4 microgram.kg-1 naloxone bolus followed by 0.4 microgram.kg-1.hr-1 naloxone infusion; 2.0 micrograms.kg-1 naloxone bolus followed by 2.0 micrograms.kg-1.hr-1 naloxone infusion; and 4.0 micrograms.kg-1 naloxone bolus followed by 4.0 micrograms.kg-1.hr-1 naloxone infusion. Although with the number of patients studied, there were no statistically significant differences among groups, clinically, there was a trend toward decreased analgesia with all three naloxone infusion doses as determined by analgesic requirements, longest analgesic-free period and visual analogue pain scores. In addition, side-effects occurred in all groups. We conclude that prophylactic naloxone, used in this manner, is not an appropriate technique for the prevention of side-effects associated with epidural morphine used for the prevention of pain after thoracotomy.

Femoral nerve block with bupivacaine 0.25 per cent for postoperative analgesia after open knee surgery.

An assessment was made, in a randomised double-blind fashion, of the pain relief afforded by femoral nerve block (FNB) performed at the end of ligament reconstruction of the knee, using 0.25 per cent bupivacaine in ten patients, and normal saline in ten patients. All patients commenced "continuous passive motion" (CPM) of the operated knee after arrival in the Recovery Room. The postoperative analgesic requirement, both for intravenous fentanyl in the Recovery Room, and intramuscular and oral analgesia on the ward, was then studied. The time interval between FNB and first dose of analgesia was significantly longer in the bupivacaine group than in the control group. The bupivacaine group also required significantly less intravenous fentanyl in the Recovery Room. On the ward, there was no difference between the two groups in the total dose of intramuscular meperidine given in the first 12 hours postoperatively. We conclude that femoral nerve block is a useful adjunct in pain management after ligament reconstruction of the knee, especially in the early postoperative period, but does not decrease the total intramuscular dose of analgesia in the first 12 postoperative hours.

Epidural morphine prophylaxis of postoperative pain: report of a double-blind multicentre study.

In a double-blind placebo-controlled trial, 154 subjects, having intraperitoneal surgery or Caesarean section, and 53 patients undergoing lower limb orthopaedic surgery, received epidural morphine, 5 mg in 10 ml 0.9 per cent NaCl, or placebo, 10 ml 0.9 per cent NaCl, intraoperatively to determine duration of action and efficacy in preventing postoperative pain. Epidural morphine gave significantly longer postoperative analgesia (greater than 11 h) than placebo (3-6 h) in both groups (p less than 0.05) and patients who received morphine required less postoperative analgesic. Obstetric subjects experienced longer pain relief (18.3 +/- 1.3 h) than patients undergoing non-obstetric intraperitoneal surgery (9.2 +/- 1.2 h) (p less than 0.001). Generally mild pruritus affected more than 40 per cent of those receiving morphine, but over 90 per cent of obstetric patients receiving morphine. Respiratory depression occurred in 2-7 per cent of subjects who received morphine; unpredictable in onset, it responded rapidly to naloxone. Epidural bupivacaine, if employed for the surgical procedure, appeared to prolong epidural morphine analgesia. We consider epidural morphine useful in preventing postoperative pain, but its use demands close observation of respiratory rate in a high density nursing area.

Premedication with meperidine and atropine does not prolong recovery to street fitness after out-patient surgery.

The effect of premedication with meperidine and atropine on recovery to street fitness after out-patient surgery under general anaesthesia was assessed. The subjects of this study were 100 female patients undergoing therapeutic abortion. Two anaesthetic techniques were used; thiopentone-enflurane-nitrous oxide and thiopentone-fentanyl-nitrous oxide. The patients were comparable in age, weight, length of anaesthesia and time for recovery to street fitness after anaesthesia. The amount of thiopentone administered to the thiopentone-fentanyl-nitrous oxide groups was significantly greater than that administered to the thiopentone-enflurane-nitrous oxide groups. It is concluded that premedication with meperidine and atropine did not significantly prolong recovery to street fitness after out-patient surgery. Fear of prolonged recovery should not affect the decision to use premedication.

Influence of alcohol and tobacco use on sodium thiopental requirements in general anesthesia: a retrospective study of 700 patients.

Hospital charts of 700 patients who had undergone upper gastrointestinal surgery were reviewed to examine the relationship between alcohol abuse and dose of intravenous sodium thiopental (Pentothal) required to induce general anesthesia. Patients who required a high sodium thiopental dose (greater than 6.08 mg/kg) exhibited a higher incidence of alcoholism, heavy drinking, and heavy smoking, compared to patients who required low sodium thiopental dose (greater than 3.42 mg/kg and less than 4.75 mg/kg). Alcoholics and heavy drinkers, the majority of whom were heavy smokers, required a greater mean sodium thiopental dose than heavy smokers who were neither alcoholics nor heavy drinkers. Possible future research into the apparent cross tolerance between alcohol and sodium thiopental is discussed, particularly the possibility that the family physician may be able to use sodium thiopental dose requirement as a marker for early detection and diagnosis of alcoholism.

Reduction of hypoxic pulmonary vasoconstriction by nitrous oxide administration in the isolated perfused cat lung.

Local pulmonary vasconstriction in response to alveolar hypoxia is a protective mechanism reducing blood flow to poorly oxygenated areas of lung. Pulmonary blood flow is thereby directed to better oxygenated lung units and venous admixture and the resulting arterial hypoxaemia is reduced. The effect of nitrous oxide on the pulmonary pressor response to alveolar hypoxia was assessed in the isolated perfused cat lung preparation under conditions of constant flow and constant left atrial and airway pressures. Nitrous oxide, in concentrations of 50 per cent and 75 per cent, was found to produce a reversible depression of the hypoxic pulmonary pressor response. The importance of hypoxia pulmonary vasconstriction and the possible implications of its reduction by anaesthetic agents are discussed.

Reduction of hypoxic pulmonary vasoconstriction by diethyl ether in the isolated perfused cat lung: the effect of acidosis and alkalosis.

Hypoxic pulmonary vasoconstriction is a protective mechanism diverting pulmonary blood flow away from hypoxic areas toward more optimally oxygenated lung units. Venous admixture is reduced and arterial oxygenation improved. Hypoxic pulmonary vasoconstriction was demonstrated during acidosis, alkalosis and normal pH in the isolated perfused cat lung under conditions of constant flow and constant left atrial and airway pressures. Two per cent diethyl ether markedly reduced hypoxic vasoconstriction under all acid-base conditions, the hypoxic pressor response returning after wash-out of diethyl ether. Modification of hypoxic pulmonary vasoconstriction during acid-base disturbances and possible implications of concurrent anaesthetic administration are discussed.

Reduction of hypoxic pulmonary vasoconstriction during diethyl ether anaesthesia in the dog.

The activity of the pulmonary vasoconstrictor response to alveolar hypoxia was assessed by measuring the redistribution of pulmonary blood flow in response to the ventilation of one lung with nitrogen. The vasoconstrictor response was depressed during the administration of 5% diethyl ether but returned when the ether was withdrawn. It is suggested that depression of the hypoxic vasoconstrictor mechanism may be one cause of the increased alveolar-arterial Po2 difference noted during ether anaesthesia.

Reduction of hypoxic pulmonary vasoconstriction in the dog during administration of nitrous oxide.

The pulmonary vasoconstrictor response to alveolar hypoxia was assessed by measuring the redistribution of blood flow in response to the unilateral administration of nitrogen or nitrous oxide. The response was diminished when nitrous oxide was administered and returned to previous levels when hypoxia was produced again by nitrogen. It is postulated that depression of the hypoxic vasoconstrictor response by nitrous oxide may contribute to the increased alveolar-arterial Po2 difference during anaesthesia.

Reduction of hypoxic pulmonary vasoconstriction during trichloroethylene anesthesia.

A double-lumen tube was inserted into the trachea of dogs anesthetized with intravenous pentobarbital (30-40 mg/kg). Blood flow/unit lung volume in each lung was measured with 133Xe. Both lungs were initially ventilated with oxygen and measurements of pulmonary blood flow, CO2 output, cardiac output, and blood gases were made. When nitrogen was administered to one lung blood flow was diverted to the opposite lung. The diversion of flow was reduced by the inhalation of 1% trichloroethylene but returned after withdrawal of the anesthetic. There were no significant changes in cardiac output. Changes in CO2 output and arterial Po2 were compatible with the xenon results. It is concluded that trichloroethylene may increase arterial hypoxemia by reducing vasoconstriction in hypoxic areas of lung.