Prophylactic ondansetron does not improve patient satisfaction in women using PCA after Caesarean section

V. T. Cherian1 and I. Smith*,2

1Department of Anaesthesia, Christian Medical College and Hospital, Vellore 632 004, India and 2Department of Anaesthesia, North Staffordshire Hospital, Stoke-on-Trent, Staffordshire ST4 6QG, UK*Corresponding author

Accepted for publication: March 15, 2001


    Abstract
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
Eighty-one consenting women undergoing elective Caesarean section under spinal anaesthesia were randomly divided into two groups. In Group O patients, ondansetron 4 mg was given intravenously at the end of the surgery and 8 mg added to the morphine solution in the PCA syringe. Patients in Group P received only morphine via PCA syringe. Analgesia and nausea were measured until PCA was discontinued 24 h after the operation. Women in the two groups were similar with respect to age, duration of use of the PCA, amount of morphine used, previous history of PONV, and incidence of motion sickness and morning sickness during the current pregnancy. The number of women who complained of nausea and those needing rescue antiemetic medication was significantly less in Group O. However, there was no statistically significant difference between the two groups in the patient’s perception of the control of nausea and their overall satisfaction. It was noted that PONV was more frequent among women who had significant morning sickness during early pregnancy and ondansetron was beneficial in reducing PONV in these women. Although the ondansetron reduced the incidence of PONV and the need for further antiemetic medication, this did not affect patient’s satisfaction regarding their postoperative care.

Br J Anaesth 2001; 87: 502–4

Keywords: vomiting, nausea, postoperative; analgesia, patient-controlled; vomiting, antiemetics, ondansetron; anaesthesia, obstetric


    Introduction
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
Patient-controlled analgesia (PCA) with i.v. opioids provides effective postoperative analgesia, but may be limited by nausea and vomiting (PONV). Adding droperidol (0.05–0.2 mg ml–1) to morphine in the PCA syringe reduces the incidence of PONV,16 but is associated with increased sedation and extrapyramidal side effects. Ondansetron, a 5HT3 receptor antagonist, may be preferable in the postpartum period because it lacks sedative effects that may delay bonding with the baby. Although most studies on ondansetron have shown that it reduces the incidence of PONV, some workers regard this as only a ‘surrogate’ endpoint.7 8 Few investigators have examined the patient’s satisfaction with their treatment of PONV, which may be regarded as the more important outcome.7 8

The aim of our study was to evaluate whether administering prophylactic ondansetron along with morphine via PCA decreased PONV in obstetric patients and patient satisfaction.


    Methods and results
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
This double-blind, placebo-controlled study was approved by the local research ethics committee. Eighty-one women undergoing elective Caesarean section at term under spinal subarachnoid block were selected and gave written informed consent. The sample had 80% power to detect a halving of PONV from our baseline value of 60%, found in an earlier audit. Patients with hepatic, renal, psychiatric or neurological diseases and those with pre-eclampsia were excluded. History of PONV, motion sickness, smoking, and morning sickness were noted. Subarachnoid anaesthesia was administered using 2.5–2.8 ml of hyperbaric 0.5% bupivacaine, through a 25-G pencil-point needle. All patients received co-amoxyclav 1.2 g and oxytocin 10 units i.v. after the baby was delivered and diclofenac 100 mg p.r. at the end of the operation.

Women were randomly allocated into two groups by computer-generated random numbers in sequentially-numbered envelopes. Group P received a PCA with morphine (1 mg ml–1), while Group O received ondansetron 4 mg intravenously at the end of surgery plus 8 mg added to the PCA morphine syringe (60 ml) (final ondansetron concentration 0.13 mg ml–1). The PCA pump was programmed to deliver 1 ml per demand with a 3 min lockout and no background infusion. Prochlorperazine 12.5 mg i.m. was available as a rescue antiemetic to any patient who requested it.

The incidence and severity of pain, sedation, nausea and vomiting were assessed using four-point scales at 15 min intervals in the immediate recovery period and then 4 hourly until the PCA pump was discontinued. A midwife, unaware of the contents of the PCA syringe, made all postoperative assessments. Twenty-four hours later, one of the investigators assessed the patient for her perception regarding overall satisfaction with her care, control of nausea and vomiting and analgesia, using a scale of good, moderate or poor.

Data were analysed using the StatView® statistical package. Discrete variables were analysed using an unpaired t-test or non-parametric tests. Categorical variables were analysed using the chi squared or Fisher’s exact test, as appropriate. In all cases a P value of <0.05 was considered significant.

Patient characteristics between the two groups were similar except that the women in Group O were slightly heavier. There were no significant differences in the amount of morphine used, history of motion sickness, morning sickness, smoking, and PONV. The incidence of intraoperative hypotension and the requirement for an infusion of oxytocin to assist postoperative uterine contraction did not differ between the groups. There were no differences in the degree of pain between the two treatment groups at any time. Most patients were either pain-free or had only mild pain. All patients were awake or arousable to voice at all times.

The incidence of nausea and vomiting was significantly lower in the ondansetron group (Table 1). Twenty-three (57%) patients in Group P experienced severe nausea or vomiting compared with 10 (24%) in Group O (P<0.01). Eighteen women from Group P needed rescue antiemetic, compared with only five from Group O (P<0.01). Ondansetron was effective in reducing the incidence of PONV in those patients who had previously experienced morning sickness but not in those who had not (Table 1). There was no differential efficacy of ondansetron in patients with and without previous PONV, smoking or motion sickness, although the number of patients with these risk factors was relatively small. Six patients in Group P and two in Group O felt that the control of nausea and vomiting was ‘poor’, the difference was not significant. One patient in each group felt their overall care was unsatisfactory (Table 1).


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Table 1 Severity of postoperative nausea and vomiting and patient satisfaction with their control of nausea and vomiting and their overall level of care in the two treatment groups. Values represent the most severe score recorded in the postoperative period (during PCA use) and are number (%) of occurrences or responses
 

    Comment
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
In post-Caesarean section patients, we found that adding ondansetron to morphine in the PCA syringe reduces the incidence of PONV and the requirement for antiemetic rescue without increasing sedation. However, it seemed to make little difference to the patient’s perception of the control of their nausea or her feeling of satisfaction with the overall quality of care. This is consistent with other workers who reported that reducing the incidence of PONV did not improve patient satisfaction.9

There are various factors that may contribute to PONV.10 The most important predictors are female gender, previous PONV, prolonged surgery, non-smoking, and motion sickness.10 We found that the incidence of PONV was higher among women who had significant morning sickness during early pregnancy. Ondansetron was beneficial in reducing PONV in these women, but appeared to make little difference in patients who did not experience significant morning sickness.

Prophylaxis of PONV is usually administered once or intermittently. There are a few studies where the antiemetic was added into the PCA syringe.16 Droperidol was used in most of these and was found to be effective, but caused increased sedation, a side effect that we felt was undesirable in the postpartum period. Postoperative sedation was rare in our patients and was not increased by the use of ondansetron. Alexander and colleagues showed that a bolus of ondansetron 4 mg plus 0.13 mg ml–1 in the PCA syringe was effective in reducing PONV after orthopaedic surgery.2 This technique has not previously been investigated in postpartum patients.

When questioned about their perception of nausea and overall care, the responses of the two groups were similar, despite considerable differences in the incidence of PONV and request for rescue antiemetics. The high level of satisfaction could partly be a result of the euphoria of having a newborn baby and to the extra attention given by a sympathetic investigator who spent extra time with them. However, this should have applied equally to both groups.

Ondansetron is safe and effective, with a low incidence of adverse effects such as headache, dizziness, and increased liver enzymes. It has also been shown to be compatible with morphine sulphate.2 There are no reports of adverse effects of ondansetron in women who are breast feeding, although the manufacturer cautions against its use in this situation. However, similar advice applies to droperidol and prochlorperazine.


    Acknowledgement
 
This study was conducted at the North Staffordshire Hospital, Stoke-on-Trent, and was not funded by the pharmaceutical industry.


    References
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
1 Kaufmann MA, Rosow C, Schnieper P, Schneider M. Prophylactic antiemetic therapy with patient-controlled analgesia: a double-blind, placebo-controlled comparison of droperidol, metoclopramide and tropisetron. Anesth Analg 1994; 78: 988–94[Abstract]

2 Alexander R, Lovell AT, Seingry D, Jones RM. Comparison of ondansetron and droperidol in reducing postoperative nausea and vomiting associated with patient-controlled analgesia. Anaesthesia 1995; 50: 1086–8[ISI][Medline]

3 Russell D, Duncan LA, Frame WT, Higgins SP, Asbury AJ, Millar K. Patient-controlled analgesia with morphine and droperidol following caesarean section under spinal anaesthesia. Acta Anaesthesiol Scand 1996; 40: 600–5[ISI][Medline]

4 Williams OA, Clarke FL, Harris RW, Smith P, Peacock JE. Addition of droperidol to patient-controlled analgesia: effect on nausea and vomiting. Anaesthesia 1993; 48: 881–4[Abstract/Free Full Text]

5 Roberts CJ, Millar JM, Goat VA. The antiemetic effectiveness of droperidol during morphine patient-controlled analgesia. Anaesthesia 1995; 50: 559–62[ISI][Medline]

6 Walder AD, Aitkenhead AR. A comparison of droperidol and cyclizine in the prevention of postoperative nausea and vomiting associated with patient-controlled analgesia. Anaesthesia 1995; 50: 654–6[ISI][Medline]

7 Fisher DM. ‘The big little problem’ of postoperative nausea and vomiting. Do we know the answer yet? (Editorial). Anesthesiology 1997; 87: 1271–3[ISI][Medline]

8 Fisher DM. Surrogate outcomes: meaningful not! (Editorial). Anesthesiology 1999; 90: 355–6[ISI][Medline]

9 Scuderi PE, James RL, Harris L, Mims GR, III. Antiemetic prophylaxis does not improve outcomes after outpatient surgery when compared to symptomatic treatment. Anesthesiology 1999; 90: 360–71[ISI][Medline]

10 Watcha MF, White PF. Postoperative nausea and vomiting. Its etiology, treatment, and prevention. Anesthesiology 1992; 77: 162–84[ISI][Medline]





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