[Effect of increasing amounts of clonidine during hyperbaric tetracaine spinal anesthesia]

The effect of adding clonidine to hyperbaric tetracaine spinal anesthesia was investigated in 60 ASA class I-II patients scheduled for orthopedic and lower abdominal surgery. The subjects were randomly allocated into 4 groups. All patients received tetracaine 10 mg in 10% glucose solution 2 mL. Patients in group 1 received above medication and were the control group, patients in the other groups received tetracaine plus increasing dosages of clonidine: 15 microgram (Gr.2), 30 microgram (Gr.3), and 45 microgram (Gr.4). The segmental level of sensory loss was tested by the pinprick method using a 23 G needle. The three clonidine groups had significantly increased in the sensory regression time to L1 level (by 42, 47, 60% respectively), and also had significantly increased motor complete recovery time (by 48, 70, 74% respectively), but the incidence of hypotension and bradycardia was increased in the clonidine 0.045 mg group. It is concluded that addition of 15 or 30 microgram clonidine may be useful as a means of increasing the duration of hyperbaric tetracaine spinal anesthesia.