Abstract
The diaphragm is the main inspiratory muscle and the main indicator of diaphragmatic contractility is the trans-diaphragmatic pressure (Pdi). The aim of this clinical study was to determine the effect of four different anaesthetic protocols on Pdi in anaesthetized healthy dogs. Eighty client-owned dogs were recruited in this clinical study. All the animals received dexmedetomidine and morphine as premedication and propofol for induction. Anaesthesia was maintained with one of four protocols: isoflurane (I), isoflurane with CRI of propofol (IP), isoflurane with CRI of fentanyl (IF), and isoflurane with CRI of ketamine (IK). When the surgical plane of anaesthesia was achieved, two balloon catheters were inserted, one into the stomach and one into the mid-third of the oesophagus for Pdi measurement. Pdi value was the highest in groups I (14.9±4.7 mmHg) and IK (15.2±3.5 mmHg) and the lowest in groups IP (12.2±3.2 mmHg) and IF (12.0±5.9 mmHg). There was a statistically significant difference (p = 0.029) between groups IK and IF. PE’CO2 was statistically significantly higher (p<0.0005) in group IF (7.7±0.8 kPa) than in group IK (6.5±0.7 kPa). Isoflurane alone or isoflurane with ketamine for the maintenance of anaesthesia seem to better preserve the respiratory function and the diaphragmatic contractility than isoflurane with either propofol or fentanyl in dogs. Therefore, the use of isoflurane or isoflurane with ketamine may be of benefit when animals with respiratory problems have to be anaesthetized.
Highlights
It is well known that general anaesthesia depresses respiratory function
The effects of many inhalation and injectable anaesthetics on the respiratory function and on diaphragmatic contractility have already been studied in animals and humans [5,6,7,8], whereas few data exist on the influence of opioids and methylxanthines [9,10]
Obese animals were excluded from the study as it has been shown that obesity may decrease diaphragmatic contractility in humans [26,27,28]
Summary
It is well known that general anaesthesia depresses respiratory function. Anaesthetic drugs interfere centrally with the regulation of ventilation and with the function of the respiratory muscles [1,2]. The effects of many inhalation (enflurane, halothane, isoflurane, sevoflurane) and injectable (propofol, thiopentone) anaesthetics on the respiratory function and on diaphragmatic contractility have already been studied in animals and humans [5,6,7,8], whereas few data exist on the influence of opioids and methylxanthines [9,10]. In all these studies, the diaphragmatic contractility was evaluated experimentally by measuring the transdiaphragmatic pressure (Pdi) after electrical stimulation of the phrenic nerves. It has been shown that halothane depresses Pdi and the electrical activity of the diaphragm in spontaneously breathing dogs [5]
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