Addition of oral clonidine to postoperative patient-controlled analgesia with i.v. morphine

Using a randomized, double-blind, placebo-controlled design,we have investigated, in 40 patients undergoing major abdominalsurgery, the effect of oral clonidine 300 µg, 1 h beforeand 12 h after surgery on postoperative morphine requirements(evaluated by PCA). During the 24 h of the study, pain scoresmeasured every 6h did not differ significantly. Morphine requirementstended to be reduced in the clonidine group but the differencewas not significant. There were no significant differences alsoin mean arterial pressure, ventilatory frequency and the incidenceof pruritus and nausea. Heart rate was significantly lower until18 h after surgery and sedation was significantly more pronouncedin patients receiving clonidine. We cannot recommend routineoral administration of clonidine before surgery to improve postoperativeanalgesia. (Br. J. Anaesth. 1994; 72: 537–540)     

HEART RATE RESPONSE TO AN I.V. TEST DOSE OF ADRENALINE AND LIGNOCAINE WITH AND WITHOUT ATROPINE PRETREATMENT

In order to evaluate the sensitivity of an adrenaline test dosefor detecting intravascular injection and the effect of atropinepretreatment, 90 ASA physical status I and II patients wereallocated randomly to two groups, to receive i.v. saline 1 ml(n = 46) or i.v. atropine 0.5 mg (n = 44). Five minutes later,all patients received an i.v. test does of 2% lignocaine 3 mlwith adrenaline 15 µg at a rate of 1 ml s^–1. Thegroups were similar with respect to basal heart rate (HR). HRremained unchanged after saline injection, but increased slightly5 min after atropine injection (mean 78 (SD 15) beat min^–1vs 87 (20) beat min^–1 (P <0.05). After the test doseof lignocaine with adrenaline, HR increased significantly inboth groups at 30 s, 1 and 2 min, and remained increased at3 min in the atropine group. The maximum increase in HR wasgreater in the atropine group than in the saline group (31 (4)beat min^–1 vs 26 (11) beat min^–1 (P < 0.05).However, when individual maximum HR changes are considered,five patients in the saline group and four in the atropine grouphad an increase 10 beat min^–1, and three patients in thesaline group had no change or a decrease in HR. Defining a positiveresult to a test dose as an increase in HR of > 10 beat min^–1,the sensitivity of the adrenaline test dose was 83 (5.5)% inthe saline group and 91 (3.5)% in the atropine group (ns). Thusa test dose containing 2% lignocaine 3 ml and adrenaline 15µg was not very sensitive for detecting intravascularinjection, as moderate or false negative responses occurredfrequently.