the opioid requirements of patients recovering from herniorrhaphy in this study the surgical wound was infiltrated with anaesthetic before closure a low concentration of 0 25 was used with levobupivacaine higher levels could result in improved clinical benefit four sheep weighing 39 49 kg mean 44 sd 4 kg were given increasing bolus doses from 40 mg of racbupivacaine hcl these were administered at least 1 day apart via a pvc cannula until a fatal outcome resulted the heart and brain were removed within 20 min of death to be analysed for bupivacaine concentration the heart was removed by transection through the great vessels approximately 20 mm above the level of the aortic valve and 20 mm below the caudal border of the right atrium blood was immediately expressed from the cardiac chambers and representative samples of the left and right atrium and ventricle were obtained blotted and stored frozen 20 u00b0 c until assay the brain was removed by transection at the level of the lower border of the pons blotted and stored frozen as for the heart tissue tissue concentrations of the bupivacaine enantiomers are presented in table 2 the variability in the fatal doses 80 200 mg was.