The effects of thiopentone and propofol on oesophageal pressures were examined in 39 bitches. The dogs were premedicated with either atropine (n = 13), acepromazine maleate (n = 13) or a combination of atropine and acepromazine. Anaesthesia was induced with either thiopentone (15 dogs) or propofol (24 dogs), both given intravenously. Immediately following the induction of anaesthesia, gastric pressure and lower oesophageal sphincter pressure (LOSP) were measured and oesophageal barrier pressure determined. There were no significant differences attributable to the premedication regimens used but both LOSP and barrier pressure were significantly lower in the dogs anaesthetised with propofol compared to the animals given thiopentone (LOSP 12‐2 ± 4‐2 cm H2O propofol group versus 26‐8 ± 6‐5 cm H2O thiopentone group).

Fifty dogs were investigated in order to correlate the length and position of the lower oesophageal sphincter (LOS) with external measurements. Various external measurements were taken while the dogs were anaesthetised and positioned in lateral recumbency. An oesophageal tube was then introduced into the oesophagus and thoracic radiographs were taken. The 'real internal length of the oesophagus' was calculated as the length from the lower jaw incisor tooth to the position of the oesophageal tube at the costal border of the diaphragm. A highly significant linear correlation was found between this internal length and the external length from lower jaw incisor tooth to the anterior border of the head of the 10th rib. Using oesophageal manometry, the length and position of the LOS was also studied in 25 clinically normal bitches. The mean length of the LOS was found to be 4.6 +/- 0.92 cm. The position of the LOS was a mean of 4.4 +/- 1.69 cm cranial to the costal border of the diaphragm. The findings of this study indicate that the external measurements can be used to position catheters for accurate oesophageal manometry in the dog.

The anaesthetic induction agents thiopentone, propofol and alphaxalone-alphadolone were administered to cats intravenously and ketamine and xylazine-ketamine-atropine were administered intramuscularly in order to determine their effects on gastric pressure, lower oesophageal sphincter pressure, and barrier pressure. Manometric measurements were made with a non-perfused catheter tip pressure transducer. All the anaesthetic induction agents decreased the tone of the lower oesophageal sphincter but the reduction was least with ketamine. Lower oesophageal sphincter tone was significantly higher in cats anaesthetised with either xylazine-ketamine-atropine or propofol than in cats anaesthetised with either thiopentone or alphaxalone-alphadolone. Despite a higher gastric pressure in the cats anaesthetised with ketamine rather than with the other drugs except propofol, the barrier pressure was also significantly higher in cats anaesthetised with ketamine than in cats anaesthetised with any of the other drugs except xylazine-ketamine-atropine. The risk of gastrooesophageal reflux seemed to be higher with alphaxalone-alphadolone than with thiopentone if the lower oesophageal sphincter pressure and gastric pressure are used as indicators of likely reflux.

Combinations of acepromazine maleate, pethidine hydrochloride and atropine sulphate (0.05 mg/kg) or acepromazine maleate and pethidine hydrochloride and acepromazine maleate alone or atropine sulphate (0.1 mg/kg) alone were used to premedicate cats before they were anaesthetised with thiopentone, to investigate their effects on gastric pressure, lower oesophageal sphincter pressure and barrier pressure under anaesthesia. Manometric measurements were made by using a non-perfused manometric technique. The lower oesophageal sphincter pressure was lowest in the cats premedicated with atropine sulphate alone. The difference in barrier pressure between the atropine (0.1 mg/kg) and acepromazine treated cats was highly significant. The risk of gastro-oesophageal reflux appeared to be highest with atropine (0.1 mg/kg) if barrier pressure is used as an indicator of the likelihood of reflux.

The effect of body position on lower oesophageal sphincter pressure (LOSP), gastric pressure and barrier pressure (BrP) was investigated in 40 dogs anaesthetised for neutering procedures. The dogs were placed in lateral recumbency followed by dorsal recumbency (group 1) or vice versa (group 2). LOSP decreased significantly in the animals which were positioned initially in lateral recumbency, when they were then placed in dorsal recumbency, while those initially positioned in dorsal recumbency showed no significant change in their LOSP or BrP when their position was altered to lateral recumbency. When the data from both groups were pooled, LOSP and BrP were significantly lower when the dogs were in dorsal compared to lateral recumbency (P < 0.05).