Effect of i.v. diamorphine on the regression of spinal block

Twenty patients undergoing transurethral prostatectomy under spinal anaesthesia were allocated randomly in one of two groups. After operation dermatomal levels to cold were measured every 30 min until they had receded to T10. Patients in group 1 were then given diamorphine 5 mg in 0.9% saline 5 ml i.v. and in group 2 0.9% saline 5 ml i.v. Block level to cold and degree of motor block were assessed at 15-min intervals for 1 h after injection. Block regression continued in the control group while there was no decrease in the diamorphine group for 30 min (P < 0.01) after which it then receded at a similar rate as the control group. There was no significant difference in motor block between the two groups.