Incidence and prophylaxis of nausea and vomiting in post-anesthetic recovery in a tertiary teaching hospital

Abstracts

JUSTIFICATIVA E OBJETIVOS: Náuseas e vômitos pós-operatórios (NVPO) constituem complicação freqüente e potencialmente grave que aumenta o tempo de recuperação pós-anestésica (RPA) e implica insatisfação dos pacientes. Avaliação do risco para NVPO e instituição de profilaxia visando ao bem-estar dos pacientes e à redução de custos têm sido freqüentes em publicações médicas. Este estudo observacional avaliou a incidência, fatores de risco e adequação e efetividade da profilaxia para NVPO na RPA de um hospital-escola terciário. MÉTODO: As informações obtidas a partir de prontuários e questionários aplicados aos pacientes incluíram idade, fatores preditivos maiores para NVPO (sexo feminino, história prévia, não-tabagismo, uso pós-operatório de opióides), profilaxia administrada, ocorrência de NVPO, tipo de cirurgia e anestesia, utilização de óxido nitroso, estado clínico e tempo de permanência na RPA. RESULTADOS: Observou-se incidência de 18,5% de náuseas e 8,5% de vômitos no pós-operatório imediato. Observou-se, ainda, correlação entre fatores maiores de risco e ocorrência de NVPO. Não se observou correlação entre tais fatores e a utilização de medicação antiemética profilática, bem como entre sua utilização e a ocorrência de NVPO. Contudo, observou-se tendência à administração de medicação profilática em pacientes jovens do sexo feminino. CONCLUSÕES: A preocupação dos anestesiologistas da instituição com NVPO ficou estabelecida. Contudo, a ausência de correlação entre risco e profilaxia sugere realização empírica e pouco efetiva. Fatores não-avaliados são sugeridos pela ausência de correlação entre NVPO e o uso de antieméticos. Orientação dos anestesiologistas quanto a condutas profiláticas mais eficientes pode aprimorar os cuidados à população atendida.

COMPLICAÇÕES; DROGAS; RECUPERAÇÃO PÓS-ANESTÉSICA

SCIENTIFIC ARTICLE

Incidence and prophylaxis of nausea and vomiting in post-anesthetic recovery in a tertiary teaching hospital^*

Incidencia y profilaxis de náuseas y vómitos en la recuperación postanestésica de un hospital -escuela terciario

César Augusto Martins Patti^I; Joaquim Edson Vieira, TSA^II; Fábio Ely Martins Benseñor^III

^IMédico Anestesiologista (ex-Residente do CET HC/FMUSP)

^IIMédico Assistente, Divisão de Anestesia do HC/FMUSP, Doutor em Patologia da FMUSP; Coordenador, Centro de Desenvolvimento de Educação Médica "Professor Eduardo Marcondes", FMUSP

^IIIMédico Assistente, Disciplina de Anestesiologia HC/FMUSP; Doutor em Ciências da Saúde

Correspondence to

SUMMARY

BACKGROUND AND OBJECTIVES: Postoperative nausea and vomiting (PONV) is frequent and potentially a severe complication that increases the length of anesthetic recovery and causes patient dissatisfaction. The evaluation of the risk of PONV and institution of prophylactic measures aiming the well-being of patients and cost reduction are frequent in the medical literature. This observational study evaluated the incidence, risk factors, and adjustment and effectivity of the prophylaxis of PONV in the recovery room of a tertiary teaching school.

METHODS: Information obtained from patients' records and questionnaires answered by patients included age, major predictive factors for PONV (female gender, history, absence of smoking, and postoperative use of opioids), prophylactic drugs administered, development of PONV, type of surgery and anesthesia, use of nitrous oxide, clinical status, and length of stay in the recovery room.

RESULTS: An incidence of 18.5% of nausea and 8.5% of vomiting in the immediate postoperative period was observed. A correlation between major risk factors and the development of PONV was also observed. A correlation between those factors and prophylactic anti-emetic drugs, as well as between their use and the development of PONV, was not observed. However, a tendency to administer prophylactic medication to young female patients was observed.

CONCLUSIONS: The concerns of the anesthesiologists of the institution with PONV were evident. However, the absence of correlation between risk and prophylaxis suggests an empirical and ineffective procedure. Factors that were not evaluated were suggested by the absence between PONV and the use of anti-emetic drugs. The orientation for anesthesiologists regarding more effective prophylactic measures can improve care of the population assisted.

Key Words: COMPLICATIONS: nausea and vomiting; DRUGS: anti-emetics; POSTANESTHETIC RECOVERY.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: Náuseas y vómitos postoperatorios (NVPO) constituyen una complicación frecuente y potencialmente grave que aumenta el tiempo de recuperación postanestésica (RPA) e implica en una insatisfacción de los pacientes. Evaluación del riesgo para NVPO e institución de profilaxis para alcanzar el bienestar de los pacientes, y la reducción de los costes has sido frecuentes en publicaciones médicas. Este estudio de observación evaluó la incidencia, los factores de riesgo y la adecuación y efectividad de la profilaxis para NVPO en la RPA de un hospital-escuela terciario.

MÉTODO: Las informaciones obtenidas a partir de historias clínicas y cuestionarios aplicados a los pacientes incluyeron la edad, factores predictibles mayores para NVPO (sexo femenino, historial previo, no tabaquismo, uso postoperatorio de opioides), profilaxis administrada, incidencia de NVPO, tipo de cirugía y anestesia, utilización de óxido nitroso, estado clínico y tiempo de permanencia en la RPA.

RESULTADOS: Se observó incidencia de un 18,5% de náuseas y un 8,5% de vómitos en el postoperatorio inmediato. También se observó una correlación entre los factores mayores de riesgo e incidencia de NVPO. No se observó correlación entre tales factores y la utilización de medicación antiemética profiláctica, como tampoco en su utilización y en la incidencia de NVPO. Sin embargo, se observó una tendencia a la administración de medicación profiláctica en pacientes jóvenes del sexo femenino.

CONCLUSIONES: La preocupación de los anestesiólogos de la institución con NVPO quedó establecida. Pero la falta de una correlación entre el riesgo y la profilaxis sugiere la realización empírica y poco efectiva. Factores no evaluados se sugieren por la falta de correlación entre NVPO y el uso de antieméticos. Orientación de los anestesiólogos en cuanto a las conductas profilácticas más eficientes puede perfeccionar los con la población atendida.

INTRODUCTION

Postoperative nausea and vomiting (PONV) is a frequent complication during the post-anesthetic recovery with an estimated prevalence of 20 to 30% ^1-6. Qualified in some occasions as a "small-big problem" ², they can cause suture dehiscence, aspiration pneumonitis, electrolyte imbalances, dehydration, increased intracranial and intra-ocular pressure, and even esophageal rupture ^1-4,7. They can also increase the length of stay in the recovery room, increase the risk of re-hospitalization in outpatient procedures, increase hospital costs, and decrease patient satisfaction with the received care ^6-9.

The multifactorial etiology of PONV is secondary to the compromise of several neurotransmitters in neural pathways, including serotoninergic, dopaminergic, histaminergic, and cholinergic pathways ^1,34. This is reflected in the diversity of the drugs available for prophylaxis and treatment ^3-5. Although frequently analyzed together, nausea is defined as an unpleasant subjective feeling, while vomiting represents a complex motor action that culminates with the expulsion of gastric contents through the mouth ⁴.

Studies from the decade of 1990 on were concerned with the rational use of anti-emetic medications, especially regarding prophylaxis of PONV, aiming at decreasing side effects and optimizing hospital costs ^6,10,23.

Attempts to establish predictive scores proposed and to organize them by analyzing a large population and several risk factors involved have been made ^{3,4,6,7,12,13}. However, other proposals with the same objective tried to organize simplified scores applicable in the clinical setting without losing their predictive power ^2,11,13,23. Apfel et al. proposed a simplified score based on four factors: female gender, history of a tendency to develop nausea and vomiting, abstinence from smoking, and use of intraoperative opioids. Such score presented satisfactory validation for clinical use ^13,19-22. According to the authors, each factor adds, independently, approximately 20% of chance of developing PONV.

In 2003, a consensus conference suggested the establishment of directives to evaluate the risk, prophylaxis, and treatment of PONV, suggesting pharmacologic prophylaxis based on risk stratification. This consensus did not define a specific score for such stratification; however, it mentioned Apfel's score due to its clinical applicability and validity. Several measures have been proposed including non-pharmacologic strategies; pharmacologic treatment would not be indicated for low risk patients. The consensus also delegated to each hospital the definition of moderate risk, since some institutions consider 20% a high index ²³.

The present study evaluated the incidence of PONV in the recovery room of a tertiary teaching hospital - Instituto Central do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo - according to risk factors established, to stratify them in patients seen in this institution. It also evaluated the pharmacologic prophylactic strategy used intraoperatively by the anesthesiology team, its adequacy to the risk groups, and its effectiveness in preventing PONV. Based on the data gathered, we intend to create guidelines to orient the anesthesiologists of our institution to ensure the use of adequate treatment and prophylaxis according to the risk factors of each patient.

METHODS

After approval by the Ethics on Research Commission of the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (CAPPesq-HCFMUSP), and after signing an informed consent, patients were evaluated during their stay in the recovery room of the Surgical Center of the Instituto Central of the HC-FMUSP. This was an observational study and, therefore, we did not interfere with the perioperative conduct.

Data were gathered from April 17 to June 21, 2006, i.e., during ten weeks. We attempted to distribute homogenously the days of the week and times of the day patients were assessed; questionnaires were applied from Monday to Friday to minimize the possible discrepancy secondary to the greater number of certain surgeries in specific days. It was established an ideal number of up to six questionnaires per day, three in each period (morning/afternoon). Patients older than 18 years who underwent elective surgeries were included in the study; inclusion in the study was done according to the moment the patient was admitted in the recovery room (distributed throughout the day).

Evaluation of patients' records, including the recovery room admission form, allowed the gathering information on weight, age, gender, type of anesthesia (inhalational, intravenous, combined intravenous-inhalational, or regional block), intraoperative use of nitrous oxide, intra- or postoperative use of opioids, intraoperative prophylaxis of PONV, development of PONV, and length of stay in the recovery room. To avoid compromising the observation, researchers did not have direct contact with the anesthesiologist responsible for the patient during the intraoperative period; information in the recovery room admission form was gathered by the physician on call responsible for the unit.

Through the questionnaire applied to patients immediately before their discharge from the recovery room, information on the patients' propensity for the development of nausea and vomiting and smoking habits were gathered. The presence of clinical conditions that could predispose patients to PONV, including diabetes mellitus, chronic renal failure, and prior or current radiotherapy or chemotherapy, was also evaluated.

Patients 12 years old or younger were also excluded due to the peculiarities of the incidence of PONV and risk factors in this age group reported in the literature ^1,2,6,13,23 and probable difficulty to apply the evaluation questionnaire. Patients undergoing emergency surgeries were excluded to avoid possible interference caused by the absence of fasting ^1,2,4,13.

In this study, it was considered that vomiting is always preceded by nausea; therefore in this study the presence of vomiting indicated the prior or concurrent development of nausea.

Data are presented as mean ± standard deviation (SD) or frequency. The Student t test was used to compare means and odds ratio (OR) with a 95% confidence index.

RESULTS

One hundred and eighty-seven patients were evaluated during their staying in the recovery room. Postoperative nausea and vomiting were diagnosed in 35 patients (18.7%). Of those, 81 (43.3%) were male and 106 (56.7%) females. The mean age of the study population was 48.2 ± 14.3 years, being 50.9 ± 16.5 for males and 46.2 ± 12.3 for females. The mean weight of the sample was 68.2 ± 11.18 kg.

One hundred and forty-four patients received pharmacological prophylaxis of PONV (77%). Female patients received prophylaxis more often than male patients, 89 (47.6%) and 55 (29.4%) patients, respectively. There was also a significant predilection to administer prophylaxis to younger patients (46 ± 16 years) when compared to older patients (55 ± 18 years), p = 0.0002.

As for the presence of the risk factors described by Apfel, two concomitant factors were observed in 79 patients (42.3%), followed by the presence of one factor (59 patients, 31.6%), three factors (30 patients, 16% of the cases), and four factors (4 patients, 2.14%). Fifteen patients (8%) did not present any risk factors. Smoking abstinence was the risk factor more prevalent (149 patients, 79.7%), followed by female gender (106 patients, 56.7%), use of opioids in the recovery room (35 patients, 18.7%), and history of PONV (33 patients, 17.7%). When compared regarding the risk of developing PONV, the low risk group (without risk factors or with one) had an incidence of 9.5% (n = 7), and the group with moderate or high risk (two or more factors) had an incidence of 24.8% (n = 28). This difference was significant (odds ratio = 3.15 [1.30 - 7.66]). Table I shows the incidence of the different combinations of those risk factors.

Regarding other risk factors evaluated, 18 patients (9.6%) underwent intravenous general anesthesia, 128 (68.4%) underwent general combined intravenous-inhalational anesthesia, and 41 patients (21.9%) underwent regional blockade. No cases of inhalational anesthesia were recorded. Nitrous oxide was used in 71 anesthesias (55.5% of general balanced anesthesias and 38% of total anesthesias). Prior clinical conditions with a possible impact on the development of PONV were detected in 49 (26.2%) patients and included diabetes mellitus in 20 patients (10.7% of the cases), chronic renal failure in 9 patients (4.8%), and chemo- or radiotherapy in 20 patients (10.7%). As for patient distribution according to the type of surgery, 49 patients (26.2%) underwent urologic surgeries, 31 (16.6%) open gynecologic surgeries, 25 (13.4%) plastic surgeries, 24 (12.8%), videolaparoscopies (gastro/gynecologic), 17 (9.1%) opened gastroenterologic surgeries, 12 (6.4%) general surgeries, 12 (6.4%) ENT, and 17 (9.1%) of other types including vascular, thoracic, neurologic, ophthalmologic, and bone marrow transplant.

As for the perioperative prophylaxis, one drug was used in 76 patients (40.6%), two drugs in 60 cases (32.1%), and three drugs in eight patients (4.3%). Forty-three patients (23%) did not receive any pharmacological prophylaxis.

When one drug was used, ondansetron (38 cases, 20.4%) was used more often, followed by metochlopramide hydrochloride (24 cases, 12.8%). Less frequent choices included dexamethasone sodium phosphate (9 cases, 4.8%) and dimenidrinate (5 patients, 2.7%). When two drugs were used, there was a preference for the combination of metochlopramide hydrochloride and dexamethasone sodium phosphate (25 patients, 13.4%), followed by ondansetron and dexamethasone sodium phosphate (17 patients, 9.1%), ondansetron and dimenidrinate (9 patients, 4.8%), metochlopramide hydrochloride and ondansetron (3 patients, 1.6%), and metochlopramide and dimenidrinate (1 patient, 0.5%). Prophylaxis with three drugs used metochlopramide hydrochloride, ondansetron and dexamethasone (4 patients, 2.1%), and ondansetron, dexamethasone sodium phosphate and dimenidrinate (4 patients, 2.1%). Regarding the institution of prophylaxis related to the presence of the factors described by Apfel, 54 patients (73%) in the low risk group (absence of risk factors or the presence of only one) received some form of prophylaxis, while 90 patients (79.7%) in the high risk group (two or more factors) received some form of prophylaxis. A statistically significant difference between the groups was not observed (OR = 1.45 [0.73 - 2.88]).

Regarding the use of prophylaxis and the development of PONV, 20.1% (29 patients) who received prophylaxis developed PONV, while 14% (6 patients) who did not receive prophylaxis developed PONV; this difference was not statistically significant (OR = 1.56 [0.60 - 4.04]).

The mean length of stay in the recovery room for patients who did not develop PONV was 80 ± 105 minutes and 75 ± 45 minutes for those who developed PONV, which does not configure a statistically significant difference (p = 0.914). There were also no significant differences in the length of stay between patients who received prophylaxis and those who did not (88 ± 40 and 98 ± 45 minutes, respectively) (p = 0.449).

DISCUSSION

The present study evaluated the incidence of postoperative nausea and vomiting (PONV) in the population admitted to the recovery room of a tertiary teaching hospital. It also evaluated the prophylactic therapy administered by the anesthesiologists in the operating room to prevent PONV.

The incidence of PONV in the patients in this study was similar to that reported in the literature ^1-4. Initially, we suspected that this incidence would be higher since it involved a tertiary hospital with a higher prevalence of patients with severe disease and, therefore, more susceptible to complications, which did not prove to be true. It is possible that more severe patients were transferred to the intensive care unit and only those who underwent simple surgical procedures or with better control of concomitant diseases and other risk factors were admitted to the recovery room ^12,13,19. Besides, it should be mentioned that one fourth of the patients had some disease or predisposing factor of PONV.

As expected, the presence of a greater number of risk factors resulted in a higher incidence of PONV. Approximately 60% of patients were at moderate or high risk for the development of PONV, characterized by the presence of two or more of the factors described by Apfel. This is similar to the reports in the literature, as well as the incidence three times higher of PONV in this population when compared with the low risk population^11-13. Note that the distribution of the study population, despite the predominance of female patients, which is in itself a risk factor, was considered normal.

The predominance of balanced general anesthesia showed the preference of the anesthesiologists of the institution. Although the use of nitrous oxide was not a specific subject of this study, its use in one third of the surgeries can be considered relevant, since anesthetic agents with the same efficacy but with a lower incidence of side effects are available. One should remember that the risk of PONV increases significantly with the use of nitrous oxide ^24,6,13.

The use of prophylactic medication for PONV in three quarters of the patients in the study demonstrated that the anesthesiologists in the operating room are aware of this risk, which is a positive factor. However, a correlation between risk factors for PONV and the use of prophylaxis was not observed. The increased number of patients with low risk who received prophylactic treatment, which was probably an unnecessary increase in cost, confirms that anesthesiologists are aware of this problem. Prophylactic treatment was more frequent in young female patients, which has been described in the literature as the group with greater risk for the development of PONV ^19,23. However, since a difference between the use of prophylactic medication in patients with high and low risk was not detected, it demonstrated that the degree of concern about solving this problem was not followed by an effective treatment in each case. For example, metochlopramide chloride was used prophylactically, as a single drug or in association with other drugs, in 30.5% of the cases, although its therapeutic actions are well-established and its lack of prophylactic efficacy is widely known ^1-3.

The present study did not detect increased in length of stay in the recovery room due to PONV, which does not agree with the results reported in the literature ^1,6,13,23. Adequate pharmacologic treatment in the immediate postoperative period might explain this difference. Since it was demonstrated that anesthesiologists are concerned with the development of PONV, one can assume that the same happens among the professionals in the recovery room. The difference might rely on the fact that this small team follows a more uniform, and therefore more effective routine than the large team of anesthesiologists who work in the operating room probably with a less homogenous routine.

The incidence of and the risk factors for PONV were similar in the study population when compared with the information available in the literature ^1-6. The establishment of guidelines for the treatment of nausea and vomiting would lead to an increased effectivity of the management of this worrisome occurrence, not only for patients, but also anesthesiologists, as has been demonstrated by this study. The data presented here suggest that, a priori, prophylaxis should not be instituted, but only when two or more of the risk factors described are present.

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*

Recebido da Divisão de Anestesia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HC/FMUSP), São Paulo, SP

Publication Dates

• Publication in this collection
  04 Sept 2008
• Date of issue
  Oct 2008

History

• Received
  26 June 2007
• Accepted
  13 June 2008