Abstract
In humans the combined administration of epidural anaesthesia and inhalation anaesthesia may result in cardiovascular instability associated with decreases in heart rate and blood pressure. Anaesthesia was induced with a combination of midazolam/ketamine in 18 female pigs with a mean body weight of 24.9 +/- 5.9 kg scheduled for surgical removal of the liver. After tracheal intubation, anaesthesia was maintained on a circle rebreathing circuit with isoflurane. Epidural anaesthesia was administered with ropivacaine (AL-group, n = 8) at 0.2 ml/kg of a 7.5 mg/ml solution to the anaesthetised animals. The A-group (n = 10) received isoflurane anaesthesia only. The vaporiser was set at 2.5% for the A-group and 1.5% for the AL-group. Heart rate, invasive systolic, diastolic, and mean arterial blood pressure were monitored. Comparisons were made between treatments and within treatments comparing variables during surgical preparation and abdominal surgery. Differences between treatments were not statistically significant (P > 0.05) during surgical preparation or during abdominal surgery. For within treatment groups, the differences between surgical preparation and abdominal surgery were statistically significant (P < 0.05) for heart rate in the A-group, but not statistically significant (P > 0.05) for the other variables. It is concluded that abdominal surgery may be associated with statistically significant changes in heart rate in isoflurane-anaesthetised pigs and that the combined administration of epidural ropivacaine may prevent statistically significant changes in HR during abdominal surgery.
Highlights
In a research project aimed at the development of a bioartificial liver support system using the pig as model, it became essential to ensure optimal perioperative cardiovascular stability[12]
To meet the aim of the study, i.e. to assess differences associated with surgical preparation and abdominal surgery, as well as comparing changes in the 4 cardiovascular variables during abdominal surgery in pigs anaesthetised with isoflurane, and isoflurane combined with epidural ropivacaine, the following line of investigation was followed: 1. To evaluate differences between procedures within each treatment group, the slopes of the regression lines during surgical preparation and during abdominal surgery were compared for each of the 4 cardiovascular variables (HR, systolic blood pressure (SYS), diastolic blood pressure (DIA) and mean arterial blood pressure (MAP))
The last set of results, evaluating whether the change before and during surgery between the 2 treatment groups was different, showed no statistically significant results at the 5 % level for any of the 4 cardiovascular variables; Heart rate (HR) was statistically significant at the 10 % level (HR P = 0.07), but not SYS P = 0.32; DIA P = 0.97 and MAP P = 0.57. The purpose of this investigation was to compare changes in cardiovascular variables during abdominal surgery in pigs anaesthetised with either isoflurane
Summary
In a research project aimed at the development of a bioartificial liver support system using the pig as model, it became essential to ensure optimal perioperative cardiovascular stability[12]. Surgery may activate the neuro-endocrine (stress) response that is associated with sympathetic stimulation and increases in heart rate and blood pressure[17]. Inhalation anaesthesia may alter the response to surgery but it is not completely blocked[2] and isoflurane anaesthesia may be associated with decreases in blood pressure when compared with halothane anaesthesia[9]. A possible management strategy to improve cardiovascular stability is the combined use of inhalation anaesthesia and epidural anaesthesia[7,14]. The epidural administration of local anaesthetics results in a reduction in the Received: October 2007.
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