Abstract
Background
Post-operative nausea and vomiting (PONV) is an unpleasant and one of the most distressing symptoms for any patient undergoing surgery. The anaesthetist is usually blamed, despite evidence that PONV results from a variety of factors including patient characteristics, anaesthetic techniques, and the type of surgery and post-operative care. This study had been conducted to find out the current prevalence and to assess various risk factors for PONV in the Indian population.
Methods
All patients above 18 years undergoing non-cardiac surgery under anaesthesia were selected from the daily operation theatre list by a systematic random sampling method. Koivuranta score was used to predict PONV in first 24 h post-operatively.
Results
Prevalence of PONV in the study population was found to be 25.6%. There was association detected between female gender, non-smokers and occurrence of PONV (CI 95%, p ≤ 0.001, 0.005, respectively). PONV was seen to be more common in patients with history of PONV in prior surgeries, in patients who underwent surgery under general anaesthesia and in patients where opioids were used in the post-operative period (95% CI, p ≤ 0.001, 0.001 and 0.001 respectively). General, laparoscopic, abdominal, orthopaedic, obstetric, breast and urological surgeries showed a significant association with occurrence of PONV (95% CI, p ≤ 0.05).
Conclusion
Inspite of use of antiemetics (single or dual) being given as part of the institutional protocol, the incidence of PONV was still high. There is a need to update our knowledge regarding newer antiemetics and their inclusion in PONV management guidelines. There is need for further research to study various other possible risk factors which may contribute to occurrence of PONV.
Keywords: Post-operative nausea vomiting, General anaesthesia, Emesis
Introduction
Post-operative nausea and vomiting (PONV) is an unpleasant and one of the most distressing symptoms frequently appearing in 30% of unselected inpatients and up to 70% of “high-risk” inpatients during the first 24 h after surgery.1 Despite continuing advances in anaesthetic and surgical techniques, both the incidence and severity of post-operative nausea vomiting have remained relatively unchanged. In the current scenario, antiemetic therapy is being used routinely during intraoperative and post-operative periods, but its use has not completely eliminated the incidence of PONV, which still remains a pressing problem.2 Literature revealed emesis as the most unacceptable and nausea as the fourth most unwanted symptom among ten negative post-operative outcomes in a preoperative survey.3 It results in electrolyte imbalance, dehydration, increased intracranial pressure, aspiration of gastric contents, bleeding and suture dehiscence. In addition, it raises hospital costs, discharge time and is a frequent concern voiced by patients in the preanaesthetic check-up setting.
The anaesthetist is usually blamed, despite evidence that PONV results from a variety of factors including patient characteristics, anaesthetic techniques, and the type of surgery and post-operative care. However, current understanding of risk factors for PONV is incomplete, in part because much remains to be elucidated about the pathophysiology of these symptoms, particularly their molecular biology. However, no study had been conducted among the Indian population prompting us to undertake this study to find the current prevalence and to assess various risk factors for PONV in the Indian population.
Materials and methods
This observational study was carried out at a tertiary-level hospital in India. After approval from the institutional ethics committee, written informed consent was obtained. All patients above 18 years undergoing non-cardiac surgery under anaesthesia were enrolled for this observational study. Patients undergoing emergency surgery, requiring post-operative mechanical ventilation, receiving local anaesthesia, being discharged on the same day and having communication difficulties were excluded from the study. During the study period, patients were selected from daily operation theatre (OT) list by systematic random sampling method. All enrolled patients were followed post-operatively for 24 h in the ward and assessed for presence or absence of PONV. The patients were considered as having nausea if “subjective sensation of an urge to vomit, in the absence of expulsive muscular movements”, vomiting if “forcible expulsion of the gastric contents through the mouth” and retching if “unproductive effort to vomit”. Presence of any one of the above symptoms was taken as a positive outcome. All data about patient characteristics and general anaesthesia (GA) technique were noted. The standard anaesthesia technique with an inhalation agent was used in all patients. Koivuranta score4 was used to predict PONV in which one point each were given if duration of surgery was more than 60 min, for female sex, history of motion sickness, history of PONV and being non-smoker. Suggested prophylaxis based on the risk score was given (score 0 = ± ondansetron 4 mg, 1 = ondansetron 4 mg ± dexamethasone 4 mg, 2 = ondansetron 4 mg + dexamethasone 4 mg ± propofol infusion, 3 = ondansetron 4 mg + dexamethasone 4 mg + propofol infusion ± scopolamine patch, 4 = ondansetron 4 mg + dexamethasone 4 mg + propofol infusion + scopolamine patch). Patients with 0–1, 2 or 3, and more risk factors were considered as “low,” “medium,” and “high” risk categories, respectively.
Statistical analysis was carried out using SPSS 20 software. The sample size was calculated based on previous research studies on PONV.5, 6, 7 For the risk factors being considered in this study, the power of study was taken as more than 80% and an alpha error of 5%; a sample size of 826 was calculated. Statistical analysis was done by using the Pearson's chi square test and Fisher's exact test.
Results
Prevalence of PONV was studied in 1000 patients from Dec 2015 to Feb 2017. Of a total of 3585 patients listed for surgery during the study period, 1495 patients did not meet inclusion criteria and 1090 patients were not included because of refusal or unavailability of investigator. Prevalence of PONV in the study population was 25.6%. There was no association between age group (years) and occurrence of PONV (Table 1).The odds ratio (OR) was 1.11, which was calculated for age group 18–50 years and >50 years. There was association between female gender and occurrence of PONV (OR: 2.29). We also found strong association between non-smokers and occurrence of PONV (95% CI, p ≤ 0.005, OR: 1.94). No association was found between the incidence of PONV and different American Society of Anesthesiologists (ASA) physical statuses of patients (95% CI, p ≤ 0.624, OR: 1.07) (Table 2). Four hundred sixty-six patients received antiemetic prophylaxis as per risk assessment (low: 307, medium: 154, high: 05) (Table 2). PONV was found to be more common in patients with history of PONV in prior surgeries (p ≤ 0.001, OR 3.27). PONV was more common in patients who underwent surgery under GA (p ≤ 0.001). The OR between GA and regional anaesthesia (RA) was calculated to be 3.15, for the occurrence of PONV. However no association was found between duration of anaesthesia and occurrence of PONV. The OR for two groups (<60 min and> 60 min) was calculated to be 1.13. PONV was found significantly more in patients where opioids were used in the post-operative period (p ≤ 0.001, OR: 2.7). There was no change in incidence of PONV in patients where prophylactic antiemetic were used (95% CI, p ≤ 0.13, OR: 1.68). General, laparoscopic, abdominal, orthopaedic, obstetric, breast and urology surgeries showed a significant association with occurrence of PONV (p ≤ 0.05). However, gynaecologic surgery, dental surgery, neurosurgery, oncosurgery and head and neck surgery showed no significant association with the occurrence of PONV (Table 2).
Table 1.
PONV in different gender and age groups.
| Sex | PONV |
Total | p-value | |
|---|---|---|---|---|
| Present | Absent | |||
| Male | 93 | 422 | 515 | 0.001 |
| Female | 163 | 322 | 485 | |
| Age group (years) | ||||
| ≤20 | 14 | 23 | 37 | 0.72 |
| 21–30 | 64 | 181 | 245 | |
| 31–40 | 54 | 154 | 208 | |
| 41–50 | 42 | 129 | 170 | |
| 51–60 | 43 | 137 | 180 | |
| 61–70 | 34 | 88 | 122 | |
| 71–80 | 5 | 28 | 33 | |
| >80 | 0 | 5 | 5 | |
| Total | 256 | 744 | 1000 | |
PONV, post-operative nausea and vomiting.
Table 2.
Clinical characteristics and occurrence of post-operative nausea vomiting.
| Clinical characteristics of patients | PONV |
p-value | Odds ratio | ||
|---|---|---|---|---|---|
| Present | Absent | ||||
| Non-smoker | Yes | 235 | 634 | 0.005 | 1.94 |
| No | 21 | 110 | |||
| ASA grade | I | 164 | 493 | 0.62 | 1.07 |
| II | 90 | 251 | |||
| III | 2 | 0 | |||
| History of PONV | Yes | 31 | 30 | 0.001 | 3.27 |
| No | 225 | 714 | |||
| Type of anaesthesia | GA | 173 | 296 | 0.001 | 3.15 |
| RA | 83 | 448 | |||
| Duration of anaesthesia | ≤60 min | 72 | 191 | 0.12 | 1.13 |
| 61–120 min | 111 | 376 | |||
| >120 min | 73 | 177 | |||
| Use of post-operative opioids | Yes | 107 | 156 | 0.001 | 2.7 |
| No | 149 | 588 | |||
| Use of prophylactic antiemetic | Yes | 144 | 322 | 0.13 | 1.68 |
| No | 112 | 422 | |||
| Type of surgery | General surgery | 31 | 221 | 0.001 | |
| Gynaecology | 49 | 121 | 0.36 | ||
| Laparoscopy | 46 | 73 | 0.001 | ||
| Orthopaedics | 12 | 103 | 0.001 | ||
| Abdominal | 52 | 40 | 0.001 | ||
| Urology | 13 | 71 | 0.01 | ||
| Obstetrics | 32 | 29 | 0.001 | ||
| Reconstructive surgery | 6 | 36 | 0.086 | ||
| Breast surgery | 17 | 21 | 0.006 | ||
| Dental | 6 | 31 | 0.20 | ||
| Neurosurgery | 12 | 21 | 0.14 | ||
| Oncosurgery | 9 | 24 | 0.52 | ||
| ENT, head and neck | 9 | 22 | 0.47 | ||
| Ophthalmology | 0 | 1 | 0.99 | ||
ASA, American Society of Anesthesiologists; GA, general anaesthesia; PONV, post-operative nausea and vomiting; RA, regional anaesthesia..
Multivariate analysis using binary logistic regression showed significant association with the history of PONV, ASA grade, use of post-operative opioids, general surgery, obstetric surgery and abdominal surgery with significant outcome (p ≤ 0.05) (Table 3). However, multivariate analysis showed no association for certain risk factors such as female gender, non-smoker status, use of GA, laparoscopic surgery and orthopaedic surgery which was at variance from results of this study, when the risk factors were considered independently for the occurrence of PONV. This is an interesting finding which suggests that more studies are required in this field.
Table 3.
Multivariate analysis by using binary logistic regression with the response variable as occurrence of PONV and adjusted odds ratios.
| Parameters | B | S.E. | Wald | df | p-value | odds ratio | 95% C.I. for OR |
|
|---|---|---|---|---|---|---|---|---|
| Lower | Upper | |||||||
| Age | 0.005 | 0.008 | 0.51 | 1 | 0.47 | 1.005 | 0.99 | 1.02 |
| Gender | 0.06 | 0.22 | 0.08 | 1 | 0.76 | 1.06 | 0.68 | 1.65 |
| History of PONV | 0.99 | 0.30 | 10.95 | 1 | 0.001 | 2.70 | 1.50 | 4.88 |
| Non-smoker | 0.39 | 0.30 | 1.72 | 1 | 0.18 | 1.48 | 0.82 | 2.68 |
| ASA grade | −0.51 | 0.22 | 5.16 | 1 | 0.02 | 0.59 | 0.38 | 0.93 |
| GA/RA | 0.60 | 1.24 | 0.23 | 1 | 0.63 | 1.82 | 0.15 | 20.94 |
| Duration of anaesthesia | 0.001 | 0.002 | 0.16 | 1 | 0.68 | 1.001 | 0.99 | 1.006 |
| Post-operative opioids | 0.65 | 0.17 | 13.38 | 1 | 0.001 | 1.92 | 1.35 | 2.72 |
| Prophylactic antiemetics | 0.05 | 1.24 | 0.002 | 1 | 0.96 | 1.05 | 0.09 | 12.05 |
| Laparoscopy | −0.28 | 0.29 | 0.95 | 1 | 0.32 | 0.75 | 0.42 | 1.33 |
| Orthopaedics | −0.57 | 0.36 | 2.50 | 1 | 0.11 | 0.56 | 0.27 | 1.14 |
| General surgery | −0.57 | 0.25 | 4.97 | 1 | 0.02 | 0.56 | 0.34 | 0.93 |
| Gynaecology | 0.30 | 0.28 | 1.19 | 1 | 0.27 | 1.35 | 0.78 | 2.35 |
| Obstetrics | 1.28 | 0.36 | 12.12 | 1 | 0.001 | 3.59 | 1.75 | 7.40 |
| Abdominal | 1.28 | 0.31 | 17.1 | 1 | 0.001 | 3.61 | 1.96 | 6.62 |
| Breast | 0.39 | 0.40 | 0.98 | 1 | 0.32 | 1.48 | 0.67 | 3.26 |
| Constant | −6.61 | 2.34 | 7.99 | 1 | 0.005 | 0.001 | ||
ASA, American Society of Anesthesiologists; B, coefficient of variable need to take exponential of B so that we can explain; df, degree of freedom; GA, general anaesthesia; p-value, probability value; OR, odds ratio; PONV, post-operative nausea vomiting; RA, regional anaesthesia; S.E., standard error; Wald, Wald statistics used to find linear correlation in variable outcomes and risk factor.
Discussion
Very few studies have been conducted based on the Indian population on prevalence of PONV and its association with known risk factors. In our scenario institutes have been following various guidelines based on studies done in foreign countries by many researchers. However, because of dearth of research based on Indian demographics and population, it was decided to conduct the study on this problem. Previous studies have noted the incidence of PONV ranging from 18 to 30%.8 In our study, in a given period of time, the PONV prevalence observed was 25.6% with nausea, vomiting and retching being 13.7%, 4.5% and 7.4%, respectively. Cohen et al. 9 found a higher incidence of PONV in patients less than 50 yrs. Literature revealed adulthood as an independent risk factor for PONV. Surprisingly we recorded no association of age with occurrence of PONV (p ≤ 0.72). Similar to our result, Purkis10, Stadler et al.11 and Apfel et al.12 revealed that adult females are 2–4 times more prone for PONV than men.10, 11, 12 It was probably linked to the luteal/follicular phase of the menstrual cycle.13,14 Chimbira and Sweeney15 found that non-smoker status was an important independent factor contributing to occurrence of PONV with smokers having significantly lesser incidence. They also concluded that protective effect of smoking may be due to induction of liver enzymes by polyaromatic hydrocarbons. In our study, 86.9% patients were observed to be non-smokers, and we found out there was significant association between non-smoker status of patient and occurrence of PONV (p ≤ 0.005).
Stadler et al.11 and Apfel et al.12 suggested that previous histories of PONV, motion sickness and migraine are also a strong risk factor for occurrence of PONV. Their study also revealed that history of motion sickness suggested a more susceptible vestibular component. In this study, there was significant association between histories of PONV to occurrence of PONV (p ≤ 0.001). The ASA physical status (I–II) as an independent risk factor for occurrence of PONV was suggested by Pierre et al.16 in their study. Sinclair et al.17 found that there was a significantly lower PONV rate among ASA III patients than among healthier patients. In this study, we did not find significant association between ASA physical status and occurrence of PONV (p ≤ 0.624) which is different to findings based on previous studies. The OR between ASA grade I and II was calculated to be 0.93, showing similar risk of occurrence of PONV in both the groups.
Literature revealed PONV results from a variety of factors including patient characteristics, anaesthetic techniques and drugs used for induction and maintenance during anaesthesia.18,19 Rüsch et al.20 in their evidence-based review study concluded that after GA the incidence of PONV was up to 30% when inhalational anaesthetics were used without any prophylaxis. In addition, uses of volatile anaesthetics is associated with a two-fold increase in the risk of PONV, with risk increasing in a dose-dependent manner, and no significant difference in incidence was seen with different volatile anaesthetics. Pierre et al.16 also found use of volatile anaesthetics as the single most important factor for predicting emesis in the first two post-operative hours. In our study also, we found a significant association between GA/use of volatile anaesthetics and occurrence of PONV (p ≤ 0.001). The incidence was about 36% and OR between the two groups (GA and RA) was 3.15, showing much higher risk of occurrence of PONV among patients undergoing surgery under GA.
Apfel et al.12 in their study concluded that there was increased risk of PONV as duration of anaesthesia progressed >60 min. In this study, no significant association was found between duration of anaesthesia and occurrence of PONV (p ≤ 0.12). The OR for two groups (<60 min and 61–120 min, 61–120 min and 120 min) was calculated to be 1.2 and 0.71, respectively, indicating similar risk of occurrence of PONV in both the groups.
Like our study, larger studies have demonstrated that use of post-operative opioids approximately doubles the risk of PONV.12 This study, however, shows the use of prophylactic antiemetics made no difference to the outcome. This surprising finding suggests that a possible reassessment of prophylactic antiemetic measures and multimodal regimens in institutional protocols for PONV management is required.
There are some limitations in our study. In this study, patient's comorbidities were not taken into consideration which could have had significant impact on the outcome. In addition, the number of patients who were in ASA grade III were limited (only two). Other known associated risk factors such as conditions leading to delayed gastric emptying, hydration status, known emetogenic medications, obesity, use of nitrous oxide, post-operative pain and so on were not taken into account. Since all the cases were taken from the daily elective OT list, no patients undergoing emergency surgeries were studied.
Conclusion
Inspite of antiemetics (single or dual) being given as part of the institutional protocol, the incidence of PONV is still high. In patients with history of PONV in prior surgeries or those who underwent surgery under GA, a newer agent like granisetron may be added along with commonly used antiemetic drugs. For patients who have undergone surgeries such as abdominal, laparoscopic, orthopaedic, obstetric, breast and urological surgeries, acupressure at the Nei-Guan (P.6) point might be helpful along with routine antiemetics. There is a need to update our knowledge regarding newer antiemetics and their inclusion in PONV management guidelines. There is need for revision of institutional protocols with PONV management guidelines and more stress is to be laid on a multimodal approach to prophylaxis. There is need for further studies to research on various other possible risk factors which may contribute to occurrence of PONV. In addition, we believe that further studies are required to create a new predictive risk score based on the Indian population.
Disclosure of competing interest
The authors have none to declare.
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