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 0.2 ml/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 MAE 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.
Highlights
Adverse effects associated with surgery with particular reference to the stress response may be reduced by the use of either spinal/epidural anaesthesia[8,9,28] or the local infiltration of lidocaine and bupivacaine before laparotomy[16]
Possible measures to reduce perioperative hypotension were to replace the local anaesthetic with an opioid during epidural anaesthesia and pre-induction fluid administration[18]
Each treatment was administered in a block, i.e. 10 pigs for isoflurane anaesthesia only (A-group), 10 pigs for anaesthesia plus ropivacaine epidural (AR-group) and 8 pigs for anaesthesia plus morphine epidural (AM-group)
Summary
Adverse effects associated with surgery with particular reference to the stress response may be reduced by the use of either spinal/epidural anaesthesia[8,9,28] or the local infiltration of lidocaine and bupivacaine before laparotomy[16]. Possible measures to reduce perioperative hypotension were to replace the local anaesthetic with an opioid during epidural anaesthesia and pre-induction fluid administration[18]. Epidural local anaesthetics block nociceptive (sensory), motor and autonomic (sympathetic) pathways whereas opioids such as morphine only affect the nociceptive component of sympathetic activation[18]. Analgesic effects of local anaesthetics may result from the spinal root blockade of sensory nerves and from systemic effects after epidural absorption[8]
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