Clinical pharmacology of clonidine

The effect on post-operative pain of intravenous clonidine given before induction of anaesthesia

Background:

Treatment of acute post-thoracotomy pain is particularly important not only to keep the patient comfortable but also to minimize pulmonary complications.

Aim:

This study was designed to test the effect of pre-induction administration of clonidine, given as a single intravenous dose, on post-operative pain scores and fentanyl consumption in patients after thoracic surgery.

Setting and Design:

Tertiary referral centre. Prospective, randomised, double-blind, placebo-controlled trial.

Methods:

Sixty patients were randomly allocated to receive clonidine (3 mcg/kg) or saline pre-operatively before induction of anaesthesia. The primary endpoint was pain on coughing (visual analogue scale (VAS) 0–100 mm) 120 min after surgery, time to first analgesic injection in the post-anaesthesia care unit (PACU) and 24-h fentanyl consumption.

Statistical Analysis:

For between-group comparisons, t-test and U-test were used as appropriate after checking normality of distribution. The incidence of complications between the groups was compared by Fisher's exact test.

Results:

The post-operative VAS for the first 120 min and the fentanyl consumption at 24 h was significantly greater in the placebo group compared with the clonidine group (P<0.05). The sedation score was increased in the clonidine group during study drug infusion, but did not differ significantly on admission to the PACU.

Conclusions:

A single intravenous dose of clonidine (3 mcg/kg) given before induction of anaesthesia significantly reduced the post-operative VAS score in the initial period and fentanyl consumption during 24 h after thoracic surgery.

Effects of intravenous and oral clonidine on hemodynamic and plasma-catecholamine response due to endotracheal intubation

STUDY OBJECTIVE

To investigate the effects of intravenous (IV) versus oral clonidine on alterations of heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), and plasma-catecholamines due to endotracheal intubation.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

University hospital surgery operating room.

PATIENTS

33 ASA physical status I patients were randomly assigned to either receive clonidine 3 micrograms/kg IV immediately prior to anesthesia induction, clonidine 4 micrograms/kg orally 90 minutes prior to anesthesia induction, or placebo.

INTERVENTIONS

Insertion of a 14 G cannula in a large cubital vein for the determination of plasma-catecholamines using local anesthesia. Insertion of a radial artery catheter for measuring blood pressure (BP) using local anesthesia. Transthoracic echocardiography determined CO.

MEASUREMENTS AND MAIN RESULTS

Heart rate, MAP, CO, and plasma-catecholamine concentrations were measured. Measurements were performed prior to induction, during intubation, and 10 minutes after intubation. During endotracheal intubation, MAP was significantly lower in the IV clonidine group compared with the placebo and the oral clonidine groups. Cardiac output was significantly lower in the IV clonidine group only. In contrast to the placebo group, norepinephrine plasma concentrations did not increase in either clonidine group. Significant alterations of epinephrine plasma concentrations due to intubation were not observed in either group. Hemodynamics after intubation were not impaired by clonidine treatment.

CONCLUSIONS

In conclusion, IV clonidine reduced stress response to endotracheal intubation compared with placebo. Oral clonidine at the dose used was less effective in blunting hemodynamic stress response than IV clonidine.