Effect of endogenous progesterone and oestradiol-17β on the incidence of gastro-oesophageal reflux and on the barrier pressure during general anaesthesia in the female dog

Abstract

ObjectiveTo investigate the potential effect of increased blood progesterone (P4) and oestradiol-17β (E2) concentrations on the barrier pressure (BrP) and the incidence of gastro-oesophageal reflux (GOR) in female dogs under general anaesthesia. Study designProspective, blinded experimental trial. AnimalsSeven female, adult, healthy dogs weighing 14–21 kg and aged 1–7 years. MethodsEach of the animals was studied under the influence of high blood E2 and basal P4 (study O), basal E2 and high P4 (study P) and basal E2 and P4 (study C) concentrations. Animals were premedicated with acepromazine and anaesthesia was induced with thiopental and maintained with halothane. Lower oesophageal pH was monitored continuously for 1 hour after induction. GOR was defined as oesophageal pH >7.5 or <4. Manometry of the posterior oesophageal sphincter (POS) was then performed using the slow pull-through technique. ResultsAcid GOR was detected in only one animal of study O. The three studies did not differ significantly in GOR. Mean BrP was 11.2 (study O), 9.1 (study P) and 11.6 mmHg (study C). No significant differences were detected with respect to mean BrP, intra-gastric pressure and POS pressure. ConclusionsIt is unlikely that the increased concentrations of E2 or P4 during the normal ovarian cycle influence the functional efficiency of the POS as a major barrier to GOR in healthy, female dogs under general anaesthesia. Clinical relevanceThe fact that female dogs undergoing obstetrical surgery represented a substantial sub-group of the animals which developed postoperative benign oesophageal stricture, should probably not be attributed to the effects of increased concentrations of female sex steroid hormones.