Efficacy of adrenaline, lignocaine-adrenaline and isoprenaline as a test dose in halothane-anaesthetized lambs.

It has been shown that an epidural test dose with adrenaline does not always detect an intravascular injection in halothane-anaesthetized children. To ascertain whether test dosing with other agents might be more useful, we sought to determine if and at what dose levels three different intravenous drugs (adrenaline, isoprenaline and 1% lignocaine with 1/200,000 adrenaline) produced an increase in heart rate (HR) in halothane-anaesthetized lambs. Eight 2-week-old lambs were anaesthetized with 1% halothane in oxygen. The lambs were intubated and ventilated in order to maintain end-tidal and arterial CO2 within normal limits; HR and blood pressure before and 15-180 s after the injection of four increasing doses of each drug were recorded. The same set of measurements was repeated after the intravenous injection of atropine 10 micrograms kg-1. Adrenaline-containing doses produced a more sustained increase in HR (P less than 0.05, ANOVA) at lower doses of adrenaline when atropine was injected first. This increase did not occur in all lambs, and dysrhythmias were manifest in some. Isoprenaline always produced a significant increase in HR without dysrhythmias whether atropine was given or not. We conclude that in halothane-anaesthetized lambs, isoprenaline is a more reliable indicator of intravascular injection than adrenaline.

Efficacy of an epidural test dose in children anesthetized with halothane.

The effect of an intravenous (iv) injection of lidocaine with epinephrine was studied to determine if such a test dose would cause a reliably detectable increase in heart rate and systemic blood pressure in children anesthetized with halothane and nitrous oxide. The effect of the injection of atropine before the test dose on these parameters was also determined. Sixty-five children 1 month to 11 yr of age and weighing 3.9-35 kg were studied. The children were assigned to one of four groups, each of which was anesthetized with 1% halothane and 50% nitrous oxide. Group 1 (n = 20) received 10 micrograms/kg atropine followed 5 min later by an iv dose of 0.1 ml/kg 1% lidocaine with 1/200,000 epinephrine (0.5 micrograms/kg) to simulate an intravascularly administered epidural test dose. Group 2 (n = 21) was identical to group 1 but did not receive atropine prior to the simulated intravascular test dose. Groups 3 (n = 12) and 4 (n = 11) were identical to groups 1 and 2, but the simulated intravascular test dose did not contain epinephrine: group 3 received atropine prior to the test dose and group 4 did not. The simulated intravascular test dose increased heart rate in group 1 (with atropine) at each time period from 15 to 120 s, but only at 45 and 60 s in group 2 (without atropine). Following the iv test dose, 6 of 21 children in group 2 had an increase in heart rate of less than 10 beats/min, while only one child in group 1 had an increase in heart rate of less than 10 beats/min. Intravenous test doses that did not contain epinephrine (groups 3 and 4) had no effect on heart rate or blood pressure. Atropine, 10 micrograms/kg, improves the reliability of an epidural test dose in children anesthetized with halothane and nitrous oxide but does not ensure total reliability in detecting an intravascular injection.

[Caudal anesthesia in children: two-year retrospective study]. / Anesthésie caudale chez l'enfant: étude rétrospective sur deux ans.

Caudal anesthesia has been used on a daily basis for two years in the Department of Anesthesia of Saint-Vincent-de-Paul Hospital. A retrospective study on 231 children was done to specify the procedures, the indication and the dosage of local anesthetics.

Pharmacokinetics of lignocaine in children following caudal anaesthesia.

The time course of the plasma lignocaine concentration, following caudal anaesthesia, was studied in 11 healthy children (3.5-9 yr). Plasma lignocaine concentrations were measured for up to 6 h after administration (5 mg kg-1). Peak plasma concentration was 2.05 +/- 0.08 micrograms ml-1 and occurred at 28.2 +/- 2.9 min after administration. Pharmacokinetic parameters determined from a two-compartmental model were similar to those observed after the i.v. or extradural administration of lignocaine in adults, except for a longer half-life of elimination (155 +/- 32 min). Since the total body clearance of lignocaine was similar in children (15.4 +/- 1.2 ml min-1 kg-1) to that in adults, the longer half-life of elimination was attributed to a larger volume of distribution in the children (3.05 +/- 0.40 litre kg-1).