The effect of the stage of the ovarian cycle (anoestrus or dioestrus) and of pregnancy on the incidence of gastro-oesophageal reflux in dogs undergoing ovariohysterectomy.

Abstract

OBJECTIVE: To investigate the potential association of increased blood progesterone (P4 ) concentrations and/or late pregnancy with the incidence of gastro-oesophageal reflux (GOR), in healthy bitches undergoing ovariohysterectomy under general anaesthesia during anoestrus or dioestrus or during the second half of pregnancy. STUDY DESIGN: Prospective observational study. ANIMALS: Ninety-four healthy, female, dogs, aged 1-8&#xa0;years presented for elective ovariohysterectomy. METHODS: Non-pregnant animals were classified into group A (anoestrus) (n&#xa0;=&#xa0;35) if blood P4 concentration was sufficiently low or group D (dioestrus) (n&#xa0;=&#xa0;26) if blood P4 concentration was sufficiently high. All animals in the second half of pregnancy were classified into group P (n&#xa0;=&#xa0;33). Acepromazine (0.05&#xa0;mg&#xa0;kg(-1) ) was administered intramuscularly as preanaesthetic medication, and sodium thiopental (10&#xa0;mg&#xa0;kg(-1) , with additional doses if needed) was administered intravenously (IV) for induction of anaesthesia. After endotracheal intubation, halothane (1.1-1.3% end-tidal concentration) in oxygen was used for maintenance of anaesthesia. Lower oesophageal pH was monitored continuously throughout surgery using a pH-measuring probe. Reflux was considered to have occurred whenever pH values of >7.5 (alkaline reflux) or <4 (acid reflux) were recorded. On completion of surgery, carprofen (4&#xa0;mg&#xa0;kg(-1) ) was administered IV. Further administration of analgesics post-operatively was dictated by visual analogue scale pain scoring. RESULT: Acid GOR was observed in five of 26 dogs in group D, six of 35 group A, and 12 of 33 group P (p&#xa0;=&#xa0;0.152). The incidence of GOR in group P approached statistical significance and was higher than the incidence in the combined group A&#xa0;+&#xa0;D (one sided p&#xa0;=&#xa0;0.044, two sided p&#xa0;=&#xa0;0.077). CONCLUSIONS: In dogs undergoing ovariohysterectomy, GOR during anaesthesia occurs with a high incidence in dogs in the second half of pregnancy compared to non-pregnant animals during anoestrus or dioestrus. CLINICAL RELEVANCE: Measures could be taken in such cases to avoid the consequences of potential reflux.