Anaesthesia, 1979, Volume 34, pages 1052-1055

Forum Coarctation in children. Controlled hypotension using labetalol and halothane

Sirsun E.F. Jones, M B , BS, FFA RCS. Consultant Anaesthetist, Birmingham Children's Hospital, Birmingham, 16

A hypotensive anaesthetic technique is normally employed during operation for the correction of coarctation of the aorta. Children may be resistant to the usual methods and induced hypotension is frequently accompanied by tachycardia. Recent work, in adults, with labetalol (Trandate) an agent with alpha and beta adrenergic blocking properties, suggests a marked synergism with halothane. Scott c f a/.' showed that after the intravenous administration of labetalol, alterations in halothane concentration produced rapid responses in blood pressure and hypotension was unaccompanied by tachycardia. This study was undertaken to determine whether a similar response was obtained in children and to see if satisfactory conditions could be achieved during operation for coarctation.


Nine children undergoing correction of post-ductal coarctation of the aorta were studied. Their ages,

weights, and pre-operative mean arterial pressures and heart rates are shown in Table 1. The arterial pressure in each patient was measured from the ascending aorta during a recent cardiac catheterisation (A in Fig. I). None of the patients was in heart failure, or receiving therapy for hypertension. One of the children (Patient no. 4) had a small atrial septa1 defect, but it was thought that this was unlikely to affect the haemodynamics to any degree. Thirty minutes before operation, the patients received phenoperidine 0.03 mg/kg and droperidol 0.3 mg/kg by intra-muscular injection, up to a maximum of 0.5 and 5 mg respectively. In addition, patients weighing over 20 kg received 5 mg of oral diazepam 90 min before operation. Anaesthesia was induced with thiopentone 5 me/ kg. followed by tubocurarine 0.6 mg/kg. After intubation anaesthesia was maintained with nitrous oxide and oxygen (2:l) and 1% halothane. Artificial ventilation was instituted using a Blease 5000 Pulmoflator, with tidal volumes of 10 ml/kg and

Table 1. Pre-operativedetails of the patients studied

Patient no. 1 2 3 4 5 6 7 8 9


Age (years)


Mean arterial pressure



1 3 4 6 8 9 11 11 14

8.1 13 19.5 23 24.5 28 31.4 30 26

88 113 110 96 88 100 108 111 86

0003-2409/79/1200-1052 502.00

Heart rate (beatslmin) 125 110

I14 82 106 89 88 93 84

0 1979 Blackwell Scientific Publications


rates varying with age. 3-5 cm H 2 0 positive endexpiratory pressure was applied. Ventilation was subsequently adjusted to maintain the Paco, between 5 and 5.3 kPa. The right radial or axillary artery was cannulated with a 20- or 22-gauge cannula, and direct readings of systolic, diastolic and mean arterial pressure were monitored continuously. The heart rate was obtained from a digital reading from the electrocardiograph. The arterial pressure was allowed to stabilise whilst 1% halothane was administered and then 1 mg/kg labetalol was given intravenously. (Patient no. 1 was given an initial dose of 0.5 mg/kg.) The halothane concentration was maintained as far as possible at l%, but this was reduced if the mean arterial pressure fell below 70% of the pre-operative value. Halothane was finally discontinued shortly before release of the aortic clamps and a. single dose of fentanyl was then given. Increments of tubocurarine were given as required. and blood was transfused to cover losses greater than 10% of the blood volume Recordings of the mean arterial pressure and


heart rate were made at six stages during the procedure (see Fig. 1). Results Mean arterial pressure (MAP) (Fig. 1). There was a significant decrease in average MAP from the preoperative value with the introduction of halothane. Further significant falls occurred 10 and 20 min after labetalol. During this period the halothane was reduced in concentration in five patients and turned off in one. After the application of the aortic clamp and cessation of halothane, the MAP rose but it never increased significantly above the pre-operative level. There was an expected fall and recovery following release of the crossclamp. Heart rate (HR) (Fig. 1). With the introduction of halothane the mean HR rose, but decreased soon after labetalol was given. The lowest rate 20 min after labetalol was 61 beatslmin. Cross-clamping of the aorta and cessation of halothane produced little change, but release of the crossclamp resulted in a small mean rise to 101 beatslmin. This, however, was not statistically significant. Discussion


















Flp. 1. Mean values (+s.e. mean) of (a) Mean arterial pressure (MAP) and (b) heart rate (HR). Asterisks indicate the values which differ significantly from the pre-operative level (A) (*P

Coarctation in children. Controlled hypotension using labetalol and halothane.

Anaesthesia, 1979, Volume 34, pages 1052-1055 Forum Coarctation in children. Controlled hypotension using labetalol and halothane Sirsun E.F. Jones,...
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