Cardiovascular effects of epidural morphine or ropivacaine in isoflurane-anaesthetised pigs during surgical devascularisation of the liver

Abstract

The cardiovascular effects of non-abdominal and abdominal surgery during isoflurane anaesthesia (A-group) or isoflurane anaesthesia supplemented with either epidural ropivacaine (AR-group; 0.75 % solution, 0.2 mℓ/kg) or morphine (AM-group; 0.1 mg/kg diluted in saline to 0.2mℓ/kg) were evaluated in 28 healthy pigs with a mean body weight of 30.3 kg SD ± 4.1 during surgical devascularisation of the liver. Anaesthesia was induced with the intramuscular injection of midazolam (0.3 mg/kg) and ketamine (10 mg/kg). Anaesthesia was deepened with intravenous propofol to enable tracheal intubation and maintained with isoflurane on a circle rebreathing circuit. The vaporiser was set at 2.5% for the A-group and 1.5% for the AR- and AM-groups. Differences between treatment groups were not statistically significant (P>0.05) for any of the variables. Differences between AM- and AR-groups were marginally significant heart rate (HR) (P = 0.06) and mean arterial blood pressure (MAP) (P = 0.08). Within treatment groups, differences for the A-group were statistically significant (P<0.05) between non-abdominal and abdominal surgery for HR, systolic blood pressure, diastolic blood pressure (DIA) and MAP. Within the AM-group differences were statistically significant (P < 0.05) for DIA and MAP, and within the AR group differences for all variables were not statistically significant (P > 0.05). It was concluded that in isoflurane-anaesthetised pigs, the epidural administration of ropivacaine decreased heart rate and improved arterial blood pressure during surgery.