Does salivary pH affect postoperative sore throat in the head-down position of general anesthesia?

Tracheal intubation sometimes causes postoperative sore throat (POST) due to laryngeal damage. However, clinical observations suggest that the environment of the oral cavity may also affect POST.

The purpose of this study was to investigate whether salivary pH in the oral cavity affects POST.

After obtaining ethical approval, informed consent was obtained from all patients. Patients who underwent surgery in the supine position were enrolled as the control group. Patients who underwent laparoscopic surgery in the head-down position were enrolled as the intervention group. Immediately before both groups of patients were anaesthetised, expelled saliva was collected, and salivary pH was measured. Immediately postoperatively, the same measurement was carried out before the patient regained consciousness. The primary outcome was the change in salivary pH. The secondary outcome was POST. In our study, POST was defined as pharyngeal and swallowing pain in the glossopharyngeal and superior laryngeal nerves. The normal distribution of pH was tested using the Shapiro-Wilk test followed by analysis using repeated-measurements and one-way analysis of variance. Statistical significance was set at p < .05.

A total of 62 patients were enrolled, of whom two were excluded based on the exclusion criteria. Salivary pH in the intervention group was significantly lower than that in the control group. Five patients had POST in the intervention group, whereas none had POST in the control group had POST.

Acidotic-shifted saliva is considered one of the causes of POST.