Plethysmography during aorto-iliac surgery.

Cardiac output, arterial and central venous pressures and calf blood flow were used to monitor patients undergoing abdominal aortic surgery. Measurement of calf blood flow by means of venous occlusion plethysmography showed that measurable blood flow to the legs persisted after clamping of the aorta in patients with occlusive aortoiliac lesions and that the hyperaemic response following release of the clamp was reduced. Arterial hypotension after clamp release was of the same time course as the hyperaemia. Leg blood flow measurement was a valuable monitoring procedure.

Respiratory effects of extradural analgesia after lower abdominal surgery.

Blood-gas tensions, FRC and volume of trapped gas (VTG) in the lung were measured in patients on the day before lower abdominal gynaecological surgery, and twice on the day following surgery, before and after establishing lumbar extradural block (EDB) using 0.5% bupivacaine to provide analgesia after operation. FRC and VTG were measured with the closed-circuit helium-dilution technique. Mean VTG was 175 ml before operation and 275 ml after operation. PaO2 decreased significantly after operation, and the changes in FRC and VTG that occurred were related qualitatively. EDB did not significantly alter FRC, VTG or PaO2. Individual changes in FRC could not be related to changes in VTG or PaO2. Although EDB provided effective analgesia, the variables measured did not indicate that EDB conferred an immediate respiratory advantage.

Influence of obesity on spinal analgesia with isobaric 0.5% bupivacaine.

In an unblinded study 50 patients undergoing cystoscopic procedures received a spinal anaesthetic of plain 0.5% bupivacaine 4 ml administered in the sitting position at the L3-4 space. There was a correlation between the height of blockade assessed by pinprick analgesia and the degree of obesity of the patients measured by weight, weight/height, and weight/height2. Using this dose of spinal anaesthetic agent, high blockade may be anticipated in obese patients.

Spinal anesthesia with hyperbaric bupivacaine: effect of added vasoconstrictors.

The effect of adding 0.2 ml of 1:1000 epinephrine or 0.5 ml of 1% phenylephrine to 3 ml of 0.5% bupivacaine in 8% dextrose for spinal anesthesia was assessed in 30 patients in a double-blind study. The addition of phenylephrine gave a small prolongation of the block which was not statistically significant. Although epinephrine produced a greater prolongation, this only reached statistical significance with regard to total duration. Three patients who received solutions that contained a vasopressor had prolonged blocks, but these solutions could not be relied upon to produce consistently a clinically significant increase in duration in individual patients.

Spinal anesthesia with tetracaine--effect of added vasoconstrictors.

The effect of adding 0.2 ml of 1:1000 epinephrine or 0.5 ml of 1% phenylephrine to 1.5 ml of 1% tetracaine for spinal anesthesia was assessed in 30 patients in a double-blind study. Phenylephrine but not epinephrine produced a significant prolongation of sensory loss in the T12 dermatome. Both vasoconstrictors produced a significant prolongation of the total duration of sensory and motor blockade. These findings differ from those in previous studies in which lidocaine and bupivacaine were used.

Effect of dextrose concentration on the intrathecal spread of amethocaine.

Effects of solutions of 0.5% amethocaine, containing different concentrations of dextrose (0%, 1.25%, 2.5% and 5%) were studied after intrathecal injection. The cephalad extent of block was greater with all three dextrose-containing solutions (T6), compared with the isobaric solution which contained no dextrose (T11). The variability of maximum level of block within each group was similar (seven dermatomes), and the rate of onset to maximum extent of block was the same in all groups. The rate of onset to the T12 dermatome was more rapid in the patients who received solutions containing dextrose. The initial onset of effect of the solution containing 1.25% dextrose was more like that of the isobaric solution than of those containing higher concentrations of dextrose.

Spinal anaesthesia with hyperbaric bupivacaine: effects of concentration and volume when administered in the sitting position.

In a double blind study, solutions of 0.5% or 0.75% bupivacaine containing 8% dextrose were compared with regard to the effect of varying concentration and volume when administered intrathecally to patients in the sitting position. Ten patients received 3 or 4 ml of 0.5% bupivacaine or 2 or 3 ml of 0.75% bupivacaine. Nine patients received 0.5% bupivacaine 2 ml and another nine received 0.75% bupivacaine 1.3 ml. The use of the 10-mg dose of both solutions was abandoned after nine patients in each group because of insufficient cephalad spread. With both solutions, the smallest volumes (bupivacaine 10 mg) had significantly shorter durations of action than both the larger ones (15-20/22.5 mg), between which there were no significant differences.

Gastric emptying following hysterectomy with extradural analgesia.

Using the rate of absorption of paracetamol following oral administration of the drug, gastric emptying was measured in 21 patients following hysterectomy. Gastric emptying was inhibited markedly in patients receiving narcotic analgesia after operation, but only a moderate delay was observed in patients undergoing extradural analgesia.

Effects of adrenaline and the concentration of solution on extradural block with etidocaine.

Forty patients allocated to four groups received extradural injections of etidocaine for the performance of lower abdominal surgery. Twenty millilitre of the 1% or 1.5% solutions with or without adrenaline (1:200 000) was given in a double-blind manner. The addition of adrenaline to etidocaine did not significantly prolong the duration of analgesia, but it produced significant more motor block. Etidocaine 1.5% caused significantly longer durations of analgesia and more motor block than the 1% solution. The spread of sensory analgesia was similar with all four solutions of local anaesthetic agent.

Effect of added epinephrine on spinal anesthesia with lidocaine.

The effect of adding 0.1, 0.2, or 0.3 ml of 1:1000 epinephrine to 1.5 ml of 5% lidocaine in 7.5% dextrose for spinal anesthesia was assessed in 40 patients in a double-blind study. The addition of epinephrine produced little or no clinically useful prolongation of block. There was a small reduction in the speed of decay of nerve block, but this only reached statistical significance with regard to total recovery, which took 40 to 50 minutes longer with the epinephrine-containing solutions. No difference could be seen between the three doses of epinephrine.

Interaction between baricity (glucose concentration) and other factors influencing intrathecal drug spread.

The effects of intrathecal injection of 0.5% bupivacaine in solutions containing various concentrations of glucose have been studied in four groups of 20 patients. When solutions containing 0.8% glucose were injected at the L3-4 interspace the median maximum extent of block was higher, and the range of blocks wider, with the 8% solutions. All patients receiving 0.8% glucose had blocks between the T5 and T10 dermatomes, confirming previous work on the benefits of this concentration of glucose. In the two other groups 0.5% bupivacaine containing 0 or 0.8% glucose was injected at the L2-3 interspace. In both groups of patients a wider range of blocks, with a median maximum extent that was higher, was produced. These results demonstrate how glucose concentration may be used to influence the spread of intrathecal solutions and how other factors can obscure the effect of glucose concentration.

Spinal anaesthesia with hyperbaric bupivacaine: effects of concentration and volume administered.

A double-blind study was carried out using hyperbaric solutions of bupivacaine to compare the effects of varying the concentration of bupivacaine and the volume of solution administered intrathecally. Fifty-seven patients were studied. Ten patients received each volume of each concentration: 0.5% bupivacaine in 8% dextrose, 2 ml, 3 ml or 4 ml and 0.75% bupivacaine in 8% dextrose, 1.3 ml or 2 ml. A further seven patients received 3 ml of the 0.75% solution. Both solutions consistently produced good nerve blockade. With the 0.5% solution, increases in the volume administered had no effect on the spread of sensory loss, whereas with the 0.75% solution, increasing the volume administered resulted in a significantly greater cephalad spread. The use of 3 ml of this solution was abandoned after seven patients had received it because of the excessive spread. With both solutions, increasing the volume produced a longer duration of action. The use of a 0.75% solution of hyperbaric bupivacaine for spinal anaesthesia did not appear to confer any advantage over the 0.5% solution.

Plasma lignocaine concentrations following endotracheal spraying with an aerosol.

Plasma concentrations of lignocaine were measured in three groups of anaesthetized patients following spraying of the trachea and larynx with a lignocaine 10% aerosol spray. Greater venous plasma concentrations occurred in patients who were paralysed with suxamethonium. A mean plasma concentration of 0.1 mug/ml of lignocaine resulted from each 10 mg of lignocaine used in spontaneously breathing patients, and 0.15 mug/ml in paralysed patients. In individual patients a concentration 50% in excess of the mean value may occur. The use of lignocaine 100 mg as a 10% aerosol spray can be considered safe.

Comparative anaesthetic properties of various local anaesthetic agents in extradural block for labour.

Various concentrations of lignocaine, etidocaine and bupivacaine in 10-ml doses of plain solutions were studied in a double-blind manner as agents for extradural analgesia to relieve the pain of labour. In 67 patients in established labour the onset time and duration of analgesia were assessed by the abolition and recurrence of the pain of uterine contractions, motor block on a 0-2 scale, dermatomal spread by pinprick testing, and arterial pressure by standard sphygmomanometry. Increasing the drug concentration reduced the onset times and increased both the duration of analgesia and the degree of motor block, but had little effect on dermatomal spread or on the frequency of hypotension. Based on the results the agents have been classified with regard to onset and duration of analgesia and degree of motor blockade.

Circulatory effects of labetalol during halothane anaesthesia.

Labetalol is a drug possessing both alpha and beta adrenergic receptor blocking properties. Its possible use in induced hypotension during halothane anaesthesia has been investigated. It causes a satisfactory decrease in arterial pressure unaccompanied by tachycardia. The circulatory effects of the drug during halothane anaesthesia, both with spontaneous and controlled respiration, have been measured and compared with those of halothane alone. In patients anaesthetised with 1% halothane, labetalol, with both spontaneous and controlled ventilation, was associated with a reduction in MAP from 71.5 mmHg to 54.0 mmHg (P less than 0.001) and 66.8 mmHg to 50.4 mmHg (P less than 0.001) respectively. This reduction was associated with decreases in Qt of 18% and 12% respectively. In the presence of labetalol, with 3% halothane and spontaneous respiration, the depressant effects of the anaesthetic on the heart became rapidly apparent: Qt was reduced by a further 28%. In patients not receiving labetalol, the depressant effects of 3% halothane were frequently countered by the positive inotropic effects of hypercarbia.

Modification of the circulatory effects of extradural block combined with general anaesthesia by the addition of adrenaline to lignocaine solutions.

The cardiovascular changes associated with extradural block were measured in two groups of patients who were also receiving light general anaesthesia. In the first two group (five patients) 2% plain lignocaine 20 ml was used and decreases occurred in mean arterial pressure, cardiac output, stroke volume and peripheral resistance. In the second group (10 patients) 2% lignocaine 20 ml to which adrenaline 1:200,000 had been added was used. Decreases in arterial pressure and peripheral resistance occurred in all patients, but the responses of the cardiac output and heart rate were variable, decreasing in three patients and remaining stable or increasing in seven patients. A high segmental block was presumed to have occurred in those patients who developed bradycardia and a decreased cardiac output. The differences between these studies in anaesthetized patients and those previously reported in conscious volunteers are discussed.