Postoperative sore throat is the eighth most undesirable outcome in the postoperative period. Postextubation coughing not only causes considerable patient discomfort itself but also leads to a number of undesirable side effects.1
A study performed in 2009 by Agarwal et al.2 showed that gargling liquorice 5 min before anaesthesia decreased the incidence and intensity of postoperative sore throat.
The present study was designed to evaluate the effect of different doses of liquorice gargling (0.25, 0.5 and 1 g) on the incidence and severity of sore throat and cough after operation under general anaesthesia with endotracheal intubation in comparison with the control group.
This clinical trial study was conducted in 2013 and 2014 in the university hospital after written informed consent signed by the patients. Ethical approval for this study (Ethical Committee IUMS, Project number 391132) was provided by the Ethical Committee IUMS of Isfahan University of Medical Sciences, Isfahan, Iran (Chairperson Prof K. Adibi) on 15 September 2013.
The patients were randomised into four groups of 36 using a computer-generated table of random numbers: Group 0.25 g: gargled 0.25 g of liquorice in 30 ml of water; Group 0.5 g: gargled 0.5 g of liquorice in 30 ml of water; Group 1 g: gargled 1 g of liquorice in 30 ml of water; Group 0.0 g: the control group, gargled 30 ml of water. The estimation of sample size was based on the hypothesis that gargling of liquorice would decrease the incidence of postoperative sore throat from 60% in the control group to 30% in the study group. It was calculated that with α = 0.05 and β = 0.80, 36 patients in each group were needed for the results to be of clinical significance.
The patients gargled the solution for 30 seconds without swallowing 5 min before induction of general anaesthesia. The incidence of postoperative sore throat was assessed by asking the patients about the presence or absence of sore throat at rest and on swallowing. The severity of postoperative sore throat was measured using a visual analogue scale (VAS) between 0 (no sore throat) and 100 (worst imaginable sore throat). Postoperative sore throat was measured just after extubation and at 2, 4 and 24 h after the operation. The postextubation coughing was evaluated immediately after extubation. At 24 h after surgery, the patients’ satisfaction was recorded on a 5 point scale: the 1, very satisfied; 2, satisfied; 3, no opinion; 4, dissatisfied; 5, very dissatisfied.
After the evaluation of patients for eligibility, two were excluded from the study due to needing more than one attempt at intubation. There were no significant differences among the four groups with respect to the age, sex, height, weight, American Society of Anesthesiologists (ASA) score, duration of operation, duration of anaesthesia, duration of extubation and duration of stay at PACU Post-Anesthesia Care Unit (P > 0.05). The incidence and severity of postoperative sore throat at rest and while swallowing was significantly lower in Group 1 g than Group 0.25 g and Group 0.0 g at all times of evaluation after operation (P < 0.05) (Table 1). The incidence of postextubation coughing in Group 1 g was significantly less than Group 0.25 g, Group 0.5 g and Group 0.0 g (P < 0.05). Patient satisfaction was significantly greater in Group 1 g than Group 0.25 g, Group 0.5 g and Group 0.0 g (P < 0.05). There ware no significant complications in any Group.
Glycyrrhizin has anti-inflammatory and antiallergic effects.3 Glycyrrhizic acid inhibits cyclooxygenase activity and prostaglandin formation, and also inhibits platelet aggregation. These effects result in retardation of the inflammatory process.4 Liquilitin and liquiritigenin have peripheral and central antitussive effects.5 Glabridin has antioxidant and ulcer-healing effects, which is helpful for minimising the severity of ischemic injury to the mucosa of the pharynx and trachea and hasten their healing.6 Moghadamnia et al.7 showed that liquorice bioadhesive decreases the pain and the inflammatory halo and necrotic centre of aphthous ulcers.
The postoperative sore throat can be due to patient factors, anaesthetic technique and type of surgery.2 One of the causes of sore throat and cough after extubation is injury to the mucosa of the pharynx and trachea secondary to laryngoscopy, tracheal intubation and endotracheal tube cuff inflation. The efficacy of liquorice in decreasing the incidence and intensity of postoperative sore throat may be due to the above mechanisms in isolation or as additive or synergistic effects. It can be presumed from our study that the efficacy of liquorice is dose dependent because gargling with 1 g liquorice was more effective than gargling with 0.25 or 0.5 g liquorice.
In conclusion, compared with lower doses of liquorice (0.0, 0.25 or 0.5 g) gargling 1 g of liquorice in 30 ml of water for 30 seconds 5 min before induction of anaesthesia significantly decreased the incidence and intensity of sore throat at rest and while swallowing without having adverse effects. Also, gargling with 1 g of liquorice significantly reduced the incidence of cough after extubation compared with lower doses.
Acknowledgements relating to this article
Assistance with the study: none.
Financial support and sponsorship: none
Conflicts of interest: none
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