Anaesthesia and emesis. II: Prevention and management

Genetic and environmental influences on one-trial conditioned context aversion in mice

Anticipatory nausea (AN) is caused by an association between contextual cues and the experience of nausea (the side effects of chemotherapy or radiation treatment) and it develops predominantly in female patients undergoing chemotherapy. Preclinical studies in rodents show that the administration of an illness-inducing agent in the presence of novel contextual cues can cause conditioned context aversion (CCA) and this has been proposed to model AN. The literature also suggests that brief pre-exposure to a novel context prior to shock delivery is critical in the development of contextual fear conditioning in rodents (a phenomenon known as Immediate Shock Deficit), but this has not been assessed in CCA. The aim of present study was to develop a CCA paradigm to assess this in outbred (CD1) and inbred (C57BL/6J) mice and evaluate potential sex differences. The results revealed that a single conditioning trial in which a distinctive context was paired with LiCl-induced illness was sufficient to elicit a conditioned response in both female and male CD1 outbred mice, but not in C57BL/6J inbred mice. In addition, CCA was facilitated when animals had prior experience with the context. Finally, outbred female mice showed longer and more robust retention of CCA than male mice, which parallels clinical findings. The results indicate the importance of using CD1 outbred mice as an animal model of AN as well as examining sex differences in the CCA paradigm. Similar findings in humans encourage the future use of this novel CCA preclinical mouse model.

Drugs for preventing postoperative nausea and vomiting in adults after general anaesthesia: a network meta-analysis

BACKGROUND

Postoperative nausea and vomiting (PONV) is a common adverse effect of anaesthesia and surgery. Up to 80% of patients may be affected. These outcomes are a major cause of patient dissatisfaction and may lead to prolonged hospital stay and higher costs of care along with more severe complications. Many antiemetic drugs are available for prophylaxis. They have various mechanisms of action and side effects, but there is still uncertainty about which drugs are most effective with the fewest side effects.

OBJECTIVES

• To compare the efficacy and safety of different prophylactic pharmacologic interventions (antiemetic drugs) against no treatment, against placebo, or against each other (as monotherapy or combination prophylaxis) for prevention of postoperative nausea and vomiting in adults undergoing any type of surgery under general anaesthesia • To generate a clinically useful ranking of antiemetic drugs (monotherapy and combination prophylaxis) based on efficacy and safety • To identify the best dose or dose range of antiemetic drugs in terms of efficacy and safety SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, and reference lists of relevant systematic reviews. The first search was performed in November 2017 and was updated in April 2020. In the update of the search, 39 eligible studies were found that were not included in the analysis (listed as awaiting classification).

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing effectiveness or side effects of single antiemetic drugs in any dose or combination against each other or against an inactive control in adults undergoing any type of surgery under general anaesthesia. All antiemetic drugs belonged to one of the following substance classes: 5-HT₃ receptor antagonists, D₂ receptor antagonists, NK₁ receptor antagonists, corticosteroids, antihistamines, and anticholinergics. No language restrictions were applied. Abstract publications were excluded.

DATA COLLECTION AND ANALYSIS

A review team of 11 authors independently assessed trials for inclusion and risk of bias and subsequently extracted data. We performed pair-wise meta-analyses for drugs of direct interest (amisulpride, aprepitant, casopitant, dexamethasone, dimenhydrinate, dolasetron, droperidol, fosaprepitant, granisetron, haloperidol, meclizine, methylprednisolone, metoclopramide, ondansetron, palonosetron, perphenazine, promethazine, ramosetron, rolapitant, scopolamine, and tropisetron) compared to placebo (inactive control). We performed network meta-analyses (NMAs) to estimate the relative effects and ranking (with placebo as reference) of all available single drugs and combinations. Primary outcomes were vomiting within 24 hours postoperatively, serious adverse events (SAEs), and any adverse event (AE). Secondary outcomes were drug class-specific side effects (e.g. headache), mortality, early and late vomiting, nausea, and complete response. We performed subgroup network meta-analysis with dose of drugs as a moderator variable using dose ranges based on previous consensus recommendations. We assessed certainty of evidence of NMA treatment effects for all primary outcomes and drug class-specific side effects according to GRADE (CINeMA, Confidence in Network Meta-Analysis). We restricted GRADE assessment to single drugs of direct interest compared to placebo.

MAIN RESULTS

We included 585 studies (97,516 randomized participants). Most of these studies were small (median sample size of 100); they were published between 1965 and 2017 and were primarily conducted in Asia (51%), Europe (25%), and North America (16%). Mean age of the overall population was 42 years. Most participants were women (83%), had American Society of Anesthesiologists (ASA) physical status I and II (70%), received perioperative opioids (88%), and underwent gynaecologic (32%) or gastrointestinal surgery (19%) under general anaesthesia using volatile anaesthetics (88%). In this review, 44 single drugs and 51 drug combinations were compared. Most studies investigated only single drugs (72%) and included an inactive control arm (66%). The three most investigated single drugs in this review were ondansetron (246 studies), dexamethasone (120 studies), and droperidol (97 studies). Almost all studies (89%) reported at least one efficacy outcome relevant for this review. However, only 56% reported at least one relevant safety outcome. Altogether, 157 studies (27%) were assessed as having overall low risk of bias, 101 studies (17%) overall high risk of bias, and 327 studies (56%) overall unclear risk of bias. Vomiting within 24 hours postoperatively Relative effects from NMA for vomiting within 24 hours (282 RCTs, 50,812 participants, 28 single drugs, and 36 drug combinations) suggest that 29 out of 36 drug combinations and 10 out of 28 single drugs showed a clinically important benefit (defined as the upper end of the 95% confidence interval (CI) below a risk ratio (RR) of 0.8) compared to placebo. Combinations of drugs were generally more effective than single drugs in preventing vomiting. However, single NK₁ receptor antagonists showed treatment effects similar to most of the drug combinations. High-certainty evidence suggests that the following single drugs reduce vomiting (ordered by decreasing efficacy): aprepitant (RR 0.26, 95% CI 0.18 to 0.38, high certainty, rank 3/28 of single drugs); ramosetron (RR 0.44, 95% CI 0.32 to 0.59, high certainty, rank 5/28); granisetron (RR 0.45, 95% CI 0.38 to 0.54, high certainty, rank 6/28); dexamethasone (RR 0.51, 95% CI 0.44 to 0.57, high certainty, rank 8/28); and ondansetron (RR 0.55, 95% CI 0.51 to 0.60, high certainty, rank 13/28). Moderate-certainty evidence suggests that the following single drugs probably reduce vomiting: fosaprepitant (RR 0.06, 95% CI 0.02 to 0.21, moderate certainty, rank 1/28) and droperidol (RR 0.61, 95% CI 0.54 to 0.69, moderate certainty, rank 20/28). Recommended and high doses of granisetron, dexamethasone, ondansetron, and droperidol showed clinically important benefit, but low doses showed no clinically important benefit. Aprepitant was used mainly at high doses, ramosetron at recommended doses, and fosaprepitant at doses of 150 mg (with no dose recommendation available). Frequency of SAEs Twenty-eight RCTs were included in the NMA for SAEs (10,766 participants, 13 single drugs, and eight drug combinations). The certainty of evidence for SAEs when using one of the best and most reliable anti-vomiting drugs (aprepitant, ramosetron, granisetron, dexamethasone, ondansetron, and droperidol compared to placebo) ranged from very low to low. Droperidol (RR 0.88, 95% CI 0.08 to 9.71, low certainty, rank 6/13) may reduce SAEs. We are uncertain about the effects of aprepitant (RR 1.39, 95% CI 0.26 to 7.36, very low certainty, rank 11/13), ramosetron (RR 0.89, 95% CI 0.05 to 15.74, very low certainty, rank 7/13), granisetron (RR 1.21, 95% CI 0.11 to 13.15, very low certainty, rank 10/13), dexamethasone (RR 1.16, 95% CI 0.28 to 4.85, very low certainty, rank 9/13), and ondansetron (RR 1.62, 95% CI 0.32 to 8.10, very low certainty, rank 12/13). No studies reporting SAEs were available for fosaprepitant. Frequency of any AE Sixty-one RCTs were included in the NMA for any AE (19,423 participants, 15 single drugs, and 11 drug combinations). The certainty of evidence for any AE when using one of the best and most reliable anti-vomiting drugs (aprepitant, ramosetron, granisetron, dexamethasone, ondansetron, and droperidol compared to placebo) ranged from very low to moderate. Granisetron (RR 0.92, 95% CI 0.80 to 1.05, moderate certainty, rank 7/15) probably has no or little effect on any AE. Dexamethasone (RR 0.77, 95% CI 0.55 to 1.08, low certainty, rank 2/15) and droperidol (RR 0.89, 95% CI 0.81 to 0.98, low certainty, rank 6/15) may reduce any AE. Ondansetron (RR 0.95, 95% CI 0.88 to 1.01, low certainty, rank 9/15) may have little or no effect on any AE. We are uncertain about the effects of aprepitant (RR 0.87, 95% CI 0.78 to 0.97, very low certainty, rank 3/15) and ramosetron (RR 1.00, 95% CI 0.65 to 1.54, very low certainty, rank 11/15) on any AE. No studies reporting any AE were available for fosaprepitant. Class-specific side effects For class-specific side effects (headache, constipation, wound infection, extrapyramidal symptoms, sedation, arrhythmia, and QT prolongation) of relevant substances, the certainty of evidence for the best and most reliable anti-vomiting drugs mostly ranged from very low to low. Exceptions were that ondansetron probably increases headache (RR 1.16, 95% CI 1.06 to 1.28, moderate certainty, rank 18/23) and probably reduces sedation (RR 0.87, 95% CI 0.79 to 0.96, moderate certainty, rank 5/24) compared to placebo. The latter effect is limited to recommended and high doses of ondansetron. Droperidol probably reduces headache (RR 0.76, 95% CI 0.67 to 0.86, moderate certainty, rank 5/23) compared to placebo. We have high-certainty evidence that dexamethasone (RR 1.00, 95% CI 0.91 to 1.09, high certainty, rank 16/24) has no effect on sedation compared to placebo. No studies assessed substance class-specific side effects for fosaprepitant. Direction and magnitude of network effect estimates together with level of evidence certainty are graphically summarized for all pre-defined GRADE-relevant outcomes and all drugs of direct interest compared to placebo in http://doi.org/10.5281/zenodo.4066353.

AUTHORS' CONCLUSIONS

We found high-certainty evidence that five single drugs (aprepitant, ramosetron, granisetron, dexamethasone, and ondansetron) reduce vomiting, and moderate-certainty evidence that two other single drugs (fosaprepitant and droperidol) probably reduce vomiting, compared to placebo. Four of the six substance classes (5-HT₃ receptor antagonists, D₂ receptor antagonists, NK₁ receptor antagonists, and corticosteroids) were thus represented by at least one drug with important benefit for prevention of vomiting. Combinations of drugs were generally more effective than the corresponding single drugs in preventing vomiting. NK₁ receptor antagonists were the most effective drug class and had comparable efficacy to most of the drug combinations. 5-HT₃ receptor antagonists were the best studied substance class. For most of the single drugs of direct interest, we found only very low to low certainty evidence for safety outcomes such as occurrence of SAEs, any AE, and substance class-specific side effects. Recommended and high doses of granisetron, dexamethasone, ondansetron, and droperidol were more effective than low doses for prevention of vomiting. Dose dependency of side effects was rarely found due to the limited number of studies, except for the less sedating effect of recommended and high doses of ondansetron. The results of the review are transferable mainly to patients at higher risk of nausea and vomiting (i.e. healthy women undergoing inhalational anaesthesia and receiving perioperative opioids). Overall study quality was limited, but certainty assessments of effect estimates consider this limitation. No further efficacy studies are needed as there is evidence of moderate to high certainty for seven single drugs with relevant benefit for prevention of vomiting. However, additional studies are needed to investigate potential side effects of these drugs and to examine higher-risk patient populations (e.g. individuals with diabetes and heart disease).

A History of Drug Discovery for Treatment of Nausea and Vomiting and the Implications for Future Research

The origins of the major classes of current anti-emetics are examined. Serendipity is a recurrent theme in discovery of their anti-emetic properties and repurposing from one indication to another is a continuing trend. Notably, the discoveries have occurred against a background of company mergers and changing anti-emetic requirements. Major drug classes include: (i) Muscarinic receptor antagonists-originated from historical accounts of plant extracts containing atropine and hyoscine with development stimulated by the need to prevent sea-sickness among soldiers during beach landings; (ii) Histamine receptor antagonists-searching for replacements for the anti-malaria drug quinine, in short supply because of wartime shipping blockade, facilitated the discovery of histamine (H1) antagonists (e.g., dimenhydrinate), followed by serendipitous discovery of anti-emetic activity against motion sickness in a patient undergoing treatment for urticaria; (iii) Phenothiazines and dopamine receptor antagonists-investigations of their pharmacology as "sedatives" (e.g., chlorpromazine) implicated dopamine receptors in emesis, leading to development of selective dopamine (D2) receptor antagonists (e.g., domperidone with poor ability to penetrate the blood-brain barrier) as anti-emetics in chemotherapy and surgery; (iv) Metoclopramide and selective 5-hydroxytryptamine3(5-HT3) receptor antagonists-metoclopramide was initially assumed to act only via D2 receptor antagonism but subsequently its gastric motility stimulant effect (proposed to contribute to the anti-emetic action) was shown to be due to 5-hydroxytryptamine4 receptor agonism. Pre-clinical studies showed that anti-emetic efficacy against the newly-introduced, highly emetic, chemotherapeutic agent cisplatin was due to antagonism at 5-HT3 receptors. The latter led to identification of selective 5-HT3 receptor antagonists (e.g., granisetron), a major breakthrough in treatment of chemotherapy-induced emesis; (v) Neurokinin1receptor antagonists-antagonists of the actions of substance P were developed as analgesics but pre-clinical studies identified broad-spectrum anti-emetic effects; clinical studies showed particular efficacy in the delayed phase of chemotherapy-induced emesis. Finally, the repurposing of different drugs for treatment of nausea and vomiting is examined, particularly during palliative care, and also the challenges in identifying novel anti-emetic drugs, particularly for treatment of nausea as compared to vomiting. We consider the lessons from the past for the future and ask why there has not been a major breakthrough in the last 20 years.

Prophylactic antiemetics in oral and maxillofacial surgery: a requiem?

PURPOSE

To determine the incidence of postoperative nausea and vomiting (PONV) after oral and maxillofacial surgical procedures and to evaluate the rationale behind prophylactic antiemetic medications.

MATERIALS AND METHODS

A total of 167 patients, irrespective of age and gender, undergoing oral and maxillofacial surgical procedures under general anesthesia/dissociative anesthesia, were included. Risk factors associated with PONV such as gender, type of anesthetic agent used, nature of surgical procedure, surgical approach used, and duration of surgery and postoperative use of opioids were assessed. A "watch and wait" policy was adopted in all cases of recorded PONV with gastric lavage (GL) to be performed in patients with more than 2 episodes of PONV in the 6-hour postoperative period. The efficacy of such an intervention was also assessed. Antiemetic medications were given in only those cases which did not respond favorably to GL. A chi(2) test was performed using SPSS software (Chicago, IL) to determine statistical significance.

RESULTS

Of the 167 patients included, 19 patients experienced episodes of PONV. GL was performed in 3 patients, and all showed cessation of emesis after this intervention. No antiemetic medications were administered. A significant association was observed between PONV and female gender, duration of surgery, type of anesthetic agent used, and specific surgical procedures such as oncologic and temporomandibular joint surgeries. The role of surgical approach and the use of opioids in the postoperative period on the incidence of PONV were found to be insignificant.

CONCLUSIONS

Information regarding the incidence of PONV after oral and maxillofacial surgical procedures remains scanty. We conclude that there does not appear to be a rationale for the prophylactic administration of antiemetic drugs in such surgical procedures. A watch-and-wait policy and simple GL may provide significant relief. Antiemetic medications are to be considered only in case of non-responders and intractable PONV.

Susceptibility to nausea and motion sickness as a function of the menstrual cycle

PURPOSE

The present study examined whether susceptibility to nausea and other symptoms of vection-induced motion sickness vary as a function of phase of the menstrual cycle, as research findings in this area are sparse and contradictory.

DESIGN

Ninety young women (42 current users of oral contraceptives) were exposed to a rotating optokinetic drum during the peri-menses or peri-ovulatory phase of the menstrual cycle in an independent-groups, quasi-experimental design. Nausea and motion sickness symptoms were assessed using the Nausea Profile (NP) and the Subjective Symptoms of Motion Sickness (SSMS) questionnaire.

RESULTS

Among women not on oral contraceptives, reports of nausea and motion sickness by women in the peri-menses phase were more severe than reports by women in the peri-ovulatory phase. By contrast, among women taking oral contraceptives, reports of nausea and motion sickness did not differ by the same categorical phase of the menstrual cycle.

CONCLUSIONS

We speculate that fluctuating estrogen levels over the course of the menstrual cycle may influence the experience of or susceptibility to nausea and motion sickness during illusory self-motion and other nauseogenic contexts.

Low-dose haloperidol prevents post-operative nausea and vomiting after ambulatory laparoscopic surgery

BACKGROUND

We evaluated the prophylactic effect of low-dose haloperidol (1 mg) on post-operative nausea and vomiting (PONV) in women undergoing ambulatory laparoscopic surgery. Droperidol (0.625 mg) and saline were controls.

METHODS

One hundred and fifty women undergoing ambulatory laparoscopic surgery under general anaesthesia were enrolled in this randomized, double-blind, and placebo-controlled study. After tracheal intubation, the haloperidol group (n=50) received intravenous haloperidol (1 mg), the droperidol group (n=50) received intravenous droperidol (0.625 mg), and the saline group (n=50) received intravenous saline.

RESULTS

Haloperidol- and droperidol-group patients reported a lower incidence of PONV [24% and 23% vs. 49% (saline group); P<0.05] and requested fewer doses of rescue antiemetics [13% and 16% vs. 38% (saline group); P<0.05] during the first four post-operative hours. During the 24-h post-operative period, haloperidol- and droperidol-group patients also reported a lower incidence of PONV [31% and 32% vs. 62% (saline group); P<0.01]. No differences were found between the haloperidol and droperidol groups.

CONCLUSION

Like droperidol (0.625 mg), prophylactic intravenous haloperidol (1 mg) significantly reduced the incidence of PONV in women undergoing ambulatory laparoscopic surgery.

Postoperative nausea and vomiting (PONV) after orthognathic surgery: a retrospective study and literature review

PURPOSE

Postoperative nausea and vomiting (PONV) is the most common postoperative complication after surgery and general anesthesia. PONV occurs primarily within the first 24 hours and can lead to significant morbidity, delayed hospital discharge, increased hospital costs and perhaps most importantly, poor patient satisfaction. We sought, in this study, to determine the prevalence of PONV and to identify risk factors in patients who underwent orthognathic surgery.

PATIENTS AND METHODS

We conducted a retrospective cross-sectional analytic survey of 553 consecutive patients over 14 years of age, who underwent maxillary and/or mandibular osteotomies at Kaiser Permanente Hospital (Oakland, CA), between January 2003 and March 2004. Patient-, anesthesia- and surgery-related factors that were considered to have a possible effect on the prevalence of PONV events were evaluated.

RESULTS

A total of 514 patients met the inclusion criteria. Among these patients, 40.08% experienced PONV during the first 24 hours after surgery. The most important predictive factors associated with an increased risk of PONV were female gender, young patients (15 to 25 years old), nonsmoking status, presence of predisposing factors (ie, prior history of motion sickness and/or PONV, vertigo or migraine headaches), use of volatile general anesthetics, maxillary surgery, postoperative pain level (PACU) and the use of postoperative analgesic opioid drugs. We found a directly proportional relationship between the number of risk factors and the prevalence of PONV.

CONCLUSION

We found PONV had a high prevalence among patients undergoing orthognathic surgery. Further studies are needed to develop effective protocols for preventing this common and unpleasant problem.

Effects of menstrual cycle on postoperative analgesic requirements, agitation, incidence of nausea and vomiting after gynecological laparoscopy

BACKGROUND

Several studies have suggested that the menstrual cycle has an impact on postoperative nausea and vomiting (PONV). No previous study has evaluated the effect of the menstrual cycle on the incidence of postoperative agitation and analgesic/antiemetic requirements.

METHODS

On the basis of the phase of the menstrual cycle [pre+/-menstrual (Pd 25-6), early follicular phase (Pd 8-12), ovulatory phase (Pd 13-15), and luteal phase (Pd 20-24)], 67 patients enrolled in this blinded, prospective study. Anesthesia was standardized. Fentanyl was given to the patients who had severe pain in the recovery room. The patients who had agitation were given midazolam. When pain intensity was >5 on the Visual Analog Scale, metamizol was administered in the Gynecology Department. A blinded anesthesiologist recorded episodes of PONV in the recovery room, and 2 and 24 h postoperatively.

RESULTS

The opioid requirement and the frequency of agitation were similar in each group. Metamizol consumption was highest in the luteal phase (p < 0.05). The follicular and luteal phases were predictors for vomiting at recovery (p < 0.05 and p < 0.001, respectively). At the postoperative 2nd hour, nausea was higher in the follicular phase than in the other phases (p < 0.05) and the luteal phase was a predictor for retching (p < 0.001). At the postoperative 24th hour, nausea was the common symptom in the luteal phase (p < 0.05). The need for ondansetron was highest in the luteal phase (p < 0.01).

CONCLUSIONS

In conclusion, we suggest that the scheduling of all surgical procedures according to the menstrual phase may serve to reduce the incidence of PONV and metamizol/ondansetron consumption and hospital costs.

A comparison of cyclizine, ondansetron and placebo as prophylaxis against postoperative nausea and vomiting in children

Nausea and vomiting is a relevant and common problem with unfavourable sequelae in children undergoing some plastic surgery procedures. There is a lack of anti-emetic trials performed in children, with only a few investigating the roles of the older anti-emetic agents such as cyclizine compared with newer ones such as ondansetron. This randomised, controlled, double-blind study examined the effectiveness of a single dose of ondansetron (0.1 mg x kg-1), cyclizine (20 mg) and placebo (normal saline) in the prevention of postoperative nausea and vomiting in 150 children (mean age 3.6 years) undergoing plastic genitourinary procedures. Rates of previous postoperative nausea and vomiting and motion sickness were comparable across the groups. Postoperative vomiting was significantly reduced with ondansetron prophylaxis (p = 0.006) but there was no detectable anti-emetic effect with cyclizine. Furthermore, cyclizine caused pain on injection (p < 0.001).

The efficacy of acupressure to prevent nausea and vomiting in post-operative patients

BACKGROUND

Post-operative nausea and vomiting is a common complication following general anaesthesia. Traditional Chinese medicine indicates that acupressure therapy may reduce nausea and vomiting in certain ailments.

AIM(S) OF THE STUDY

The aim of this study was to examine the effect of stimulating two acupressure points on prevention of post-operative nausea and vomiting.

DESIGN AND METHODS

A randomized block experimental design was used. The Rhodes Index of Nausea, Vomiting and Retching (INVR) questionnaire was used as a tool to measure incidence. To control the motion sickness variable, the subjects who underwent functional endoscopic sinus surgery (FESS) under general anaesthesia were randomly assigned to a finger-pressing group, a wrist-band group, and a control group. There were 150 subjects in total with each group consisting of 50 subjects. The acupoints and treatment times were similar in the finger-pressing group and wrist-band pressing group, whereas only conversation was employed in the control group.

RESULTS

Significant differences in the incidence of the post-operative nausea and vomiting were found between the acupressure, wrist-band, and control groups, with a reduction in the incidence rate of nausea from 73.0% to 43.2% and vomiting incidence rate from 90.5% to 42.9% in the former. The amount of vomitus and the degree of discomfort were, respectively, less and lower in the former group.

CONCLUSION

In view of the total absence of side-effects in acupressure, its application is worthy of use. This study confirmed the effectiveness of acupressure in preventing post-operative nausea and vomiting.

Ondansetron/promethazine combination or promethazine alone reduces nausea and vomiting after middle ear surgery

STUDY OBJECTIVES

To determine the incidence of postoperative nausea and vomiting when a combination of ondansetron and promethazine is given prophylactically, and to ascertain the effect of postoperative nausea and vomiting on recovery room duration and patient satisfaction.

DESIGN

Prospective, randomized, placebo-controlled, double-blind study.

SETTING

University-affiliated tertiary-care hospital.

PATIENTS

87 ASA physical status I and II adult patients scheduled for middle ear surgery.

INTERVENTIONS

Patients were randomly assigned to receive one of the following interventions intravenously: ondansetron 4 mg (Group 1), promethazine 25 mg (Group 2), ondansetron 2 mg plus promethazine 12.5 mg (Group 3, combination), or placebo (Group 4).

MEASUREMENTS AND MAIN RESULTS

Independent, study blinded observers recorded complaints of nausea and number of episodes of vomiting for 24 hours following the patient's first response to commands. All patients were contacted the day after discharge to inquire about nausea and vomiting. The awakening time, postanesthesia care unit and day surgery unit durations, opioid use, and side effects were recorded. At the end of the 24-hour period, the study blinded observers asked patients for an overall assessment of their global anesthesia experience using an 11-point scale. During the 24-hour period, the incidence of postoperative nausea and vomiting was reduced from 74% (placebo) to 39% (promethazine; p = 0.03) and 29% (combination; p = 0.003). Compared with placebo, the severity of vomiting was significantly less in the combination group (p = 0.04). The number of very satisfied patients correlated negatively with the incidence of postoperative nausea and vomiting (p < 0.0001) and with the severity of vomiting (p = 0.003).

CONCLUSION

The prophylactic use of an antiemetic with middle ear surgery may reduce postoperative nausea and vomiting over 24 hours, and the ondansetron/promethazine combination or promethazine alone are cost-effective choices. Finally, the combination reduced significantly the severity of vomiting.

An alternative method to alleviate postoperative nausea and vomiting in children

STUDY OBJECTIVE

To evaluate whether isopropyl alcohol vapor is an effective treatment for postoperative nausea and vomiting.

DESIGN

Double-blind, randomized, controlled study.

SETTING

Pediatric surgery center.

PATIENTS

91 ASA physical status I and II children age 6-16 years, scheduled to undergo general anesthesia and elective outpatient surgery.

INTERVENTIONS

Subjects were randomized to inhale isopropyl alcohol or saline. The intervention was repeated up to three times. If postoperative nausea or vomiting persisted after three sequences, intravenous ondansetron was administered as rescue therapy.

MEASUREMENTS AND MAIN RESULTS

Improvement in nausea was assessed using a visual analog scale, and improvement in vomiting was assessed using categorical analysis. After three treatment sequences, 65% of the children in the treatment group and 26% of the children in the control group had a significant reduction in the severity of either nausea or vomiting (p = 0.03). However, 54% of subjects in the treatment group and 80% of subjects in the control group had recurrent nausea or vomiting within 20 to 60 minutes.

CONCLUSIONS

Under the conditions of this study, repetitive inhaled isopropyl alcohol only achieved a transient antiemetic effect in children with established postoperative nausea or vomiting following general anesthesia and surgery.

Tropisetron for treating established postoperative nausea and vomiting: a randomized, double-blind, placebo-controlled study

Tropisetron can prevent postoperative nausea and vomiting (PONV) at doses smaller than those used to control chemotherapy-induced nausea and vomiting. In this placebo-controlled study, the efficacy and tolerability of three different doses of tropisetron were compared for the treatment of established PONV after surgical procedures in general anesthesia. Of 1513 patients who satisfied inclusion criteria, 314 experiencing PONV during the first 2 h after recovery from anesthesia were treated with one of three different doses of tropisetron (0.5, 2, or 5 mg) or placebo, administered i.v. as a single dose. Patients were then observed during 24 h for efficacy and tolerability. All three doses of tropisetron were significantly better than placebo in controlling emetic episodes and in reducing the need for rescue treatment. There were no significant differences among the three doses. However, in the subgroup of patients who had previous PONV, and in those randomized for nausea alone, the 2-mg and 5-mg doses controlled emetic episodes better than the 0.5-mg dose. All studied doses of tropisetron were well tolerated and did not affect vital signs. We conclude that a single i.v. administration of tropiestron significantly reduces the recurrence of emetic episodes in patients with established PONV after elective surgery with general anesthesia. Its optimal dose seems to be 2 mg.

IMPLICATIONS

Three hundred-fourteen patients suffering from postoperative nausea and vomiting received different i.v. doses of a new antiemetic drug, tropisetron, to determine the lowest effective dose. We found that a single i.v. administration of tropisetron significantly reduced postoperative nausea and vomiting after elective surgery with general anesthesia.

Postoperative nausea and vomiting. 1: Physiology and aetiology

There is a vast amount of research available relating to postoperative nausea and vomiting (PONV). This research has been analyzed and summarized in a series of two articles which draw out the main factors influencing the incidence and affecting the treatment of the condition. This, the first article, will describe the physiological processes that result in PONV. An analysis will then follow of the many factors that contribute to the complex multifactorial aetiology of PONV. These factors include personal, preoperative, intraoperative and postoperative variables which affect differing neurotransmitter centres in the chemoreceptor trigger zone (CTZ) which is situated in the brainstem. These variables will then be related to the appropriate neurotransmitter centre allowing a greater understanding of the most likely physiological pathways involved in specific cases of PONV. The second article will explore the management and treatment of PONV.

Angioedema associated with droperidol administration

Angioedema, also known as angioneurotic edema or Quincke's disease, is a well-demarcated, localized edema involving the subcutaneous tissues that may cause upper-airway obstruction. We report the case of a previously healthy 19-year-old man with no known drug allergies in whom angioedema with significant tongue swelling and protrusion developed within 10 minutes of the administration of a single IV dose of droperidol.

A double-blind randomized controlled trial of ginger for the prevention of postoperative nausea and vomiting

The efficacy of ginger for the prevention of postoperative nausea and vomiting was studied in a double-blind, randomized, controlled trial in 108 ASA 1 or 2 patients undergoing gynaecological laparoscopic surgery under general anaesthesia. Patients received oral placebo, ginger BP 0.5g or ginger BP 1.0g, all with oral diazepam premedication, one hour prior to surgery. Patients were assessed at three hours postoperatively. The incidence of nausea and vomiting increased slightly but nonsignificantly with increasing dose of ginger. The incidence of moderate or severe nausea was 22, 33 and 36%, while the incidence of vomiting was 17, 14 and 31% in groups receiving 0, 0.5 and 1.0g ginger, respectively (odds ratio per 0.5g ginger 1.39 for nausea and 1.55 for vomiting). These results were essentially unchanged when adjustment was made for concomitant risk factors. We conclude that ginger BP in doses of 0.5 or 1.0 gram is ineffective in reducing the incidence of postoperative nausea and vomiting.

A prospective survey of postoperative nausea and vomiting with special regard to incidence and relations to patient characteristics, anesthetic routines and surgical procedures

We performed a prospective study on 421 patients subjected to routine general-, orthopaedic-, urologic-, gynecological and paediatric surgery to estimate the current incidences of nausea and vomiting during the first 24 hours after surgery. The overall incidences of postoperative nausea or vomiting were 17% and 28%, respectively. Postoperative emetic symptoms were not related to age in adults. Women had more often emetic symptoms than men (P < 0.01). In general, opiate premedication was more frequently associated with postoperative nausea and vomiting than benzodiazepines (P < 0.01), but in otherwise comparable subgroups of patients undergoing major surgery, this difference was not confirmed. Balanced general anaesthesia caused more nausea (23%) and vomiting (53%) than face-mask anaesthesia (13% and 15%, respectively) or regional blocks (12% and 7%, respectively) (P < 0.001). There was a positive correlation between the duration of anaesthesia and the incidence of postoperative emetic symptoms (P < 0.001). The incidences of postoperative nausea and vomiting after abdominal surgery were 23% and 58% respectively. Corresponding figures for orthopaedic surgery were 25% and 34%, other kinds of extra-abdominal surgery 18% and 32% and for laparoscopy 21% and 25%. After minor gynecological-, urological- and paediatric surgery the incidences were less than 20%. In conclusion female gender, balanced anaesthesia, lengthy duration of anaesthesia, and abdominal and orthopaedic operations appeared to be most frequently associated with postoperative emetic symptoms.

Prevention of nausea and vomiting after day case gynaecological laparoscopy. A comparison of ondansetron, droperidol, metoclopramide and placebo

We have compared the efficacy of ondansetron, metoclopramide, droperidol and placebo in the prevention of postoperative nausea and vomiting in 118 day stay patients undergoing laparoscopic gynaecological procedures. All received a standardised general anaesthetic of fentanyl, propofol, nitrous oxide in oxygen and isoflurane. Three to five min before induction of anaesthesia, patients were allocated to receive ondansetron 4 mg, metoclopramide 10 mg, droperidol 1 mg or placebo in a randomised, double-blind manner. Visual analogue scores for nausea, the incidence of emetic episodes, and analgesic and antiemetic consumption were recorded for 48 h postoperatively. The scores for nausea were significantly lower in the ondansetron group (p < 0.01) compared with the other three groups at 1, 2 and 4 h after operation; thereafter there was no difference. The incidence of emesis was lower (p = 0.063) and time to first oral fluids was shorter (p < 0.05) in the ondansetron group. Oral analgesic requirements were significantly greater in the ondansetron group over the 48 h study period. Two patients, one each in the placebo and metoclopramide groups, had to remain in hospital overnight because of persistent emetic symptoms.

Antiemetic efficacy of a droperidol-morphine combination in patient-controlled analgesia

STUDY OBJECTIVES

To evaluate the antiemetic effectiveness and side effects of adding low-dose droperidol to morphine delivered via a patient-controlled analgesia (PCA) device.

DESIGN

Randomized, double-blind, clinical study.

SETTING

University-affiliated women's hospital.

PATIENTS

60 healthy women, 18 to 60 years of age, who underwent total abdominal hysterectomy with a standardized anesthetic regime.

INTERVENTIONS

After surgery, the control group (n = 20) had access via PCA to two cartridges, each containing morphine 1 mg/ml and saline 1 ml. The two treated groups (n = 20 each) had access via PCA to either droperidol 0.5 mg or droperidol 1 mg added to two cartridges containing morphine 1 mg/ml.

MEASUREMENTS AND MAIN RESULTS

Preoperative data, including each patient's history of nausea and vomiting with and without previous anesthesia, motion sickness, smoking, and alcohol intake, and date of her last menstrual period, were obtained. All patients received a standardized anesthetic with droperidol 0.5 mg given at closure of the peritoneum. Among those patients who received droperidol added to morphine for their postoperative analgesic regimen, fewer required rescue antiemetic medication (p < 0.05, test of trend in proportions), and they had a lower incidence of vomiting (p < 0.05, test of trend in proportions), as well as a decrease in the number of times a rescue antiemetic was needed during the 24-hour postoperative period (linear trend, p = 0.013).

CONCLUSIONS

An intermittent intake of low-dose droperidol with morphine given via a PCA delivery system in two treatment groups gave evidence for a dose-response relation between the amount of droperidol added and the proportion of patients needing a rescue antiemetic. The same result applied to the proportion of patients having an emetic episode and the number of times a rescue antiemetic had to be administered. There was no evidence that the low dose of droperidol added to morphine delivered via a PCA device increased unwanted side effects.

Comparison of the efficacy, safety, and pharmacokinetics of controlled release and immediate release metoclopramide for the management of chronic nausea in patients with advanced cancer

BACKGROUND

The short elimination half-life of metoclopramide necessitates frequent administration for optimal relief of nausea. This study compares a newly developed controlled release preparation of metoclopramide (CRM) and immediate release metoclopramide (IRM) with respect to efficacy, safety, and pharmacokinetics in patients with chronic nausea associated with advanced cancer.

METHODS

Thirty-four patients with advanced cancer with nausea lasting more than 1 month and with no evidence of involvement of the gastrointestinal tract, peptic ulcer or gastritis, brain metastases, or metabolic abnormalities were randomized, in a double-blind cross-over study, to receive 40 mg of CRM every 12 hours or 20 mg of IRM every 6 hours for 3 days. Nausea, food intake, and side effects were assessed four times daily. On Day 3, sequential venous samples were taken (12 patients) to determine plasma metoclopramide concentrations.

RESULTS

In 29 evaluable patients, the intensity of nausea on Day 3, measured by a 0-100-mm visual analogue scale and 0-3 categoric scale was 15 +/- 17 and 0.6 +/- 0.6 after IRM, versus 8 +/- 9 (P = 0.033) and 0.4 +/- 0.5 (P = 0.055) after CRM, respectively. Visual analogue scale nausea scores recorded by time of day and by day for the 3 treatment days were significantly lower for patients who received CRM compared with those who received IRM (P = 0.047 and P = 0.043, respectively), but categoric nausea scores were not significantly different between treatments by time of day and by day across the 3 treatment days. No differences were observed in caloric intake or side effects between treatments. In a pharmacokinetic analysis, the CRM/IRM ratio for area under the curve0-12 (microgram x hours x L-1), Cmax (microgram/L), and Tmax (hours) was 100%, 98%, and 2.3 fold, respectively.

CONCLUSION

Controlled release metoclopramide is safe and effective in managing chronic nausea in patients with advanced cancer. Future studies should focus on characterizing this syndrome more clearly and on determining the optimal dose of metoclopramide and the effects of drug combinations that have proven to be useful in managing chemotherapy-induced emesis (i.e., metoclopramide plus corticosteroids).

Zingiber officinale (ginger)--an antiemetic for day case surgery

The effect of powdered ginger root was compared with metoclopramide and placebo. In a prospective, randomised, double-blind trial the incidence of postoperative nausea and vomiting was measured in 120 women presenting for elective laparoscopic gynaecological surgery on a day stay basis. The incidence of nausea and vomiting was similar in patients given metoclopramide and ginger (27% and 21%) and less than in those who received placebo (41%). The requirement for postoperative antiemetics was lower in those patients receiving ginger. The requirements for postoperative analgesia, recovery time and time until discharge were the same in all groups. There was no difference in the incidence of possible side effects such as sedation, abnormal movement, itch and visual disturbance between the three groups. Zingiber officinale is an effective and promising prophylactic antiemetic, which may be especially useful for day case surgery.

Zingiber officinale does not affect gastric emptying rate. A randomised, placebo-controlled, crossover trial

The effect of the powdered rhizome of Zingiber officinale (ginger root) on the gastric emptying rate was investigated. In a double-blind crossover trial, 16 healthy volunteers were randomly allocated to receive either 1 g of ginger or placebo. Gastric emptying was measured using the oral paracetamol absorption model. Ingestion of ginger did not effect gastric emptying. The antiemetic effect of ginger is not associated with an effect on gastric emptying. No adverse effects were noted.

Perioperative gastric aspiration increases postoperative nausea and vomiting in outpatients

The efficacy of aspiration of gastric contents to reduce postoperative nausea and vomiting was investigated in a controlled randomized, double-blind study of 265 outpatients. Patients in the treated group had their stomachs aspirated with an orogastric tube. In the control group no tube was inserted. Data on the incidence of nausea and vomiting were collected in the recovery room, the day surgery unit and the day after surgery. The overall incidence of postoperative nausea and vomiting was comparable in the two groups. It was also comparable in the recovery room and the day surgery unit. However, treated patients had a higher incidence of both nausea (26.5% vs 12.0%, P < 0.005) and vomiting (16.7% vs 6.8%, P < 0.02) after their discharge from the day surgery unit. We conclude that aspiration of gastric contents with an orogastric tube does not decrease postoperative nausea and vomiting in outpatients and may increase it after discharge of the patient.

Postoperative Nausea and Vomiting: A Comparison of Anti-Emetic Drugs Used Alone or in Combination

Drugs with anti-emetic properties can exert their actions at more than one receptor site, histamine H1, muscarinic cholinergic or dopaminergic D2 receptors. This study was designed to test the hypothesis that a combination of drugs acting at different receptor sites in lower than standard doses would be at least as effective as a standard therapeutic dose of a single anti-emetic agent. A combination of droperidol, hyoscine and metoclopramide in subtherapeutic doses has been shown to be at least as effective as droperidol (1.25 mg) alone. In both groups there was a low incidence of emetic sequelae in the first 3 hours postoperatively.

[Prevention of postoperative nausea and vomiting by ondansetron]

This study was carried out to assess the efficacy of oral ondansetron, a new 5HT3 receptor antagonist, in patients undergoing thyroid surgery. It included 60 patients, randomly assigned to two groups, and receiving orally, 1 h before induction of anaesthesia, either 8 mg of ondansetron (n = 29) or a placebo (n = 30). One patient was excluded. The same anaesthetic protocol, consisting of 3 to 5 micrograms.kg-1 of fentanyl, 4 to 6 mg.kg-1 of thiopentone, and 0.5 mg.kg-1 of atracurium, was used in all. Anaesthesia was maintained with 50% nitrous oxide in oxygen with 0.8 to 1% endtidal concentration of isoflurane and additional boluses of 0.1 mg of fentanyl as required. The incidence and intensity of nausea, graded mild, moderate or severe, and the incidence of vomiting were recorded postoperatively. During the first twelve hours after surgery, 40% of patients in the placebo group had nausea (16.7% mild, 20% moderate and 6.7% severe), and 50% vomited. In the ondansetron group, nausea and vomiting occurred in 13.8% and 20.4% of patients respectively. The 4 patients in the latter group complained of major nausea. The differences between the groups were statistically significant: p = 0.025 for nausea and p = 0.042 for vomiting. It is concluded that oral ondansetron, 8 mg taken orally 1 h before surgery, significantly reduces the incidence of nausea and vomiting during the first twelve postoperative hours. As it is easy to use and has no side-effects, it might be of interest in day-case surgery patients, despite its high cost.

The incidence of postoperative nausea and vomiting in women undergoing laparoscopy is influenced by the day of menstrual cycle

Postoperative nausea and vomiting is a major cause of postoperative morbidity. It can lead to increased recovery time, delaying patient discharge and an increase in hospital costs. Past studies have shown that postoperative nausea and vomiting is more frequent in women than men, appears to elevate around the time of menarche and is reduced around the time of menopause. This retrospective review of a one-year experience of laparoscopic tubal ligation at our institute examined the effect of menstrual cycle on postoperative nausea and vomiting. The anaesthetic and surgical techniques were consistent for all patients. Patient data included age, weight, last day of menstrual cycle, the length of anaesthetic, the dose of inhalational agent, the dose of narcotic, emesis on emergence and whether or not droperidol was used. Of the the 235 patients in the study, the incidence of nausea and vomiting was 28%. One hundred fifty-eight had had no preoperative antiemetic and 77 had received droperidol. These two groups were analyzed separately. The incidence in the group not receiving droperidol was 33.5% and in the droperidol group, 16.9% (P less than 0.01). The incidence of nausea and vomiting was higher on the first eight menstrual days (51.6 vs 21.6, P less than 0.001), was highest on day five of the menstrual cycle and lowest on days 18, 19, and 20 where there was no nausea and vomiting. Droperidol reduced the incidence of postoperative nausea and vomiting but the variation in postoperative nausea and vomiting during the cycle persisted.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous alfentanil infusion in pediatric patients undergoing general anesthesia for complete oral restoration

STUDY OBJECTIVE

To study the safety and efficacy of continuous alfentanil infusions in children.

DESIGN

Randomized open study.

SETTING

Outpatient pediatric anesthesia at a university medical center.

PATIENTS

Forty pediatric patients aged 2 to 12 years about to undergo anesthesia for complete oral restoration.

INTERVENTIONS

Twenty patients were anesthetized with halothane and nitrous oxide (N2O), and 20 patients were anesthetized with N2O and a 100 micrograms/kg bolus of alfentanil followed by a continuous alfentanil infusion.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic measurements, emergence times, and postoperative side effects were measured. Hemodynamic stability was maintained in both groups. Although children emerged faster and were extubated earlier when anesthetized with alfentanil, they required longer times until they could be discharged from the outpatient anesthesia area. Children anesthetized with alfentanil had a higher occurrence of postoperative emesis compared with children anesthetized with halothane. These differences, however, were not statistically significant.

CONCLUSIONS

Alfentanil appears to be a safe anesthetic. The reason for prolonged discharge time in the alfentanil-anesthetized patient is unclear, but it may be related to postoperative vomiting.

Antiemetic prophylaxis with promethazine or droperidol in paediatric outpatient strabismus surgery

This randomized, double-blind study evaluated the antiemetic efficacy and the side-effects of promethazine pretreatment (0.5 mg.kg-1 IV + 0.5 mg.kg-1 IM) versus droperidol + placebo pretreatment (droperidol, 0.075 mg.kg-1 IV + physiological saline, 0.02 ml.kg-1 IM). One hundred unpremedicated ASA physical status I children ranging from two to ten years, and undergoing outpatient strabismus surgery were studied. All children received inhalational anaesthesia with halothane, nitrous oxide and oxygen. Neither opioids nor muscle relaxants were used. The incidence of vomiting and/or retching and the incidence of side-effects were determined in the post-anaesthesia recovery room (PARR), in the short-stay surgical unit (SSSU), and after discharge from the hospital (including the journey and the stay at home during the first postoperative day). Promethazine and droperidol were equally effective in reducing the incidence of vomiting before discharge to two and eight per cent respectively. On the contrary, the incidence of vomiting after discharge and overall were significantly less with promethazine (ten and ten per cent) than with droperidol pretreatment (54 and 56 per cent) (P less than 0.0001). Promethazine permitted the time to discharge from the hospital to be reduced to an average of three hours, without increasing the incidence of vomiting postdischarge. Promethazine pretreatment is much less expensive than droperidol pretreatment. The incidence of restlessness was significantly less with droperidol (eight per cent) than with promethazine (36 per cent) (P less than 0.001). Promethazine pretreatment demands the use of an analgesic like acetaminophen in order to reduce the incidence of postoperative pain and restlessness.(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative emesis after pediatric strabismus surgery: the effect of dixyrazine compared to droperidol

Sixty-one children, ASA physical status I, aged 2-14 years, admitted for strabismus surgery were studied. All were premedicated with diazepam and atropin rectally. Anesthesia was induced with thiopental or with halothane on a facemask, and succinylcholine was given to facilitate tracheal intubation. Anesthesia was maintained with halothane and nitrous oxide. Each child was randomly assigned to receive either no antiemetic prophylaxis (control), droperidol 0.075 mg/kg, or dixyrazine 0.25 mg/kg. The drugs were injected intravenously at the end of surgery. The incidence of vomiting during the following 24 h was 65% in the control group, 48% in the droperidol group, and 25% in the dixyrazine group (P less than 0.05 as compared to the control group). Four hours after the operation, six children in the droperidol group and none in the dixyrazine group (P less than 0.05) were difficult to arouse. It is concluded that dixyrazine reduces the incidence of postoperative vomiting without causing heavy sedation.

Double-blind comparison of transdermal scopolamine, droperidol and placebo against postoperative nausea and vomiting

Since transdermal scopolamine (TS) seems effective against seasickness, we compared its antiemetic effect with intravenous droperidol (DHBP), our routine antidote for postoperative emesis. Ninety-six female patients (ASA I-II) scheduled for short-stay surgery were randomly allocated to three study groups after giving their informed consent. The three groups were as follows: TS adhesive, delivering 140 micrograms initially and 5 micrograms/h thereafter + placebo 0.5 ml i.v. 5 min before the end of surgery; transdermal placebo adhesive preoperatively + DHBP 0.5 ml (1.25 mg) i.v. 5 min before the end of surgery; transdermal placebo + 0.5 ml placebo i.v. as indicated above. Oxycodone i.m. and glycopyrrolate i.v. were given for premedication together with the test adhesive. Anaesthesia was induced with thiopental and maintained with nitrous oxide and oxygen, enflurane, vecuronium and fentanyl. Neostigmine and glycopyrrolate were administered for reversal. In the recovery room no differences in nausea or vomiting were observed between the groups. Sedation was significantly more marked (P less than 0.15-0.0001) after DHBP than after either TS or the given DHBP and 6% of those given the placebo (P less than 0.05). During the following 24 h nausea was reported more by the placebo patients (25) than by those on TS (20) or DHBP (15) (P less than 0.05). However, actual vomiting on the ward did not differ between the groups. Visual disturbances were more frequent after TS (P less than 0.01). We conclude that prophylactic transdermal scopolamine does not diminish postoperative emetic sequelae.

The effect of droperidol on fentanyl-influenced gastric emptying in man

The effect of droperidol on gastric emptying was determined from the rate of paracetamol absorption in seven healthy adult volunteers who received fentanyl, each acting as his/her own control. On each occasion the subjects were given droperidol 2.5 mg or normal saline (placebo) i.v. in double-blind fashion. On both occasions, 20 and 50 min later a dose of 0.0015 mg kg-1 fentanyl was given. Ten minutes after the first fentanyl dose, the subjects ingested 20 mg kg-1 paracetamol with 200 ml of water. Our findings demonstrate that droperidol was not able to accelerate gastric emptying in subjects receiving subsequent small doses of fentanyl. Furthermore, the delayed absorption pattern of paracetamol on both occasions suggests that gastric emptying is retarded with or without droperidol.

Postoperative vomiting following strabismus surgery in paediatric outpatients: spontaneous versus controlled ventilation

The study was designed to compare the frequency and severity of postoperative vomiting in paediatric out-patients receiving controlled ventilation (IPPV) or breathing spontaneously (SV) during anaesthesia for strabismus repair. One hundred and twenty unpremedicated children (ages 2-12 years) were studied in a randomized fashion. After intravenous induction of anaesthesia and tracheal intubation, patients breathed halothane 1-1.5 per cent inspired and N2O 66 per cent in O2 spontaneously (n = 60), or received IPPV, halothane 0.5-1 per cent, N2O 66 per cent, and pancuronium 0.05 mg.kg-1, which was reversed with neostigmine and atropine (n = 60). The incidence of vomiting with SV was 50 per cent (95 per cent confidence limits: 34.5-65.5 per cent) compared with 40 per cent (24.5-55.5 per cent) with IPPV (p greater than 0.25). Patients in the SV group experiencing emesis had longer operations than those not vomiting (mean +/- SEM = 1.5 +/- 0.1 vs 1.2 +/- 0.1 hours, p less than 0.005). This was not the case with IPPV. There was no correlation between age, sex, duration of surgery, or number of extraocular muscles repaired, and frequency or severity of vomiting or time to discharge. No significant advantage was afforded by IPPV over SV in the present study.

Nitrous oxide anaesthesia and vomiting. The effect of nitrous oxide anaesthesia on the incidence of vomiting following gynaecological laparoscopy

Eighty-seven patients undergoing routine laparoscopy were divided randomly into two groups to study the effect of nitrous oxide anaesthesia on the incidence of postoperative vomiting. Patients in group A received nitrous oxide as part of their anaesthetic, while in group B nitrous oxide was omitted. Significantly fewer patients in group B vomited when compared with group A (17 percent and 49 percent respectively; p less than 0.005). We suggest that an anaesthetic technique which avoids nitrous oxide may be especially indicated in patients undergoing laparoscopy.

Intraocular pressure--physiology and implications for anaesthetic management

The major factors controlling intraocular pressure during surgery are the dynamic balance between aqueous humour production in the ciliary body and its elimination via the canal of Schlemm; the auto-regulation and chemical control of choridal blood volume; the extraocular muscle tone and vitreous humour volume. Prior to surgical incision of the anterior chamber in open intraocular procedures, a low-normal intraocular pressure is mandatory to avoid the hazards of iris or lens prolapse and vitreous loss associated with sudden decompression. In general, the central nervous system depressant drugs, hypnotics, narcotics, major tranquillizers, volatile anaesthetic agents are associated with a reduction in intraocular pressure, with the exception of ketamine and possibly trichloroethylene. The mechanism of action of anaesthetic agents in reducing intraocular pressure may involve a direct effect on central diencephalic control centres, reduction of aqueous production, facilitation of aqueous drainage or relaxation of extraocular muscle tone. Succinylcholine administration is associated with a significant rise in intraocular pressure, with a peak increase between two to four minutes following administration and a return to base line values after six minutes. The intraocular hypertensive effect may be due to a tonic contraction of the extraocular muscles, choroidal vascular dilatation or relaxation of orbital smooth muscle. Despite many claims to the contrary, no reported method to date has been shown to consistently prevent the intraocular hypertensive response to intravenous succinylcholine administration. Because the non-depolarizing relaxants are associated with a reduced intraocular pressure, a barbiturate-non-depolarizing relaxant technique utilizing preoxygenation and cricoid pressure has evolved as the most commonly employed induction technique for the emergency repair of a penetrating eye injury. The alternative non-depolarizing relaxant pretreatment-barbiturate-succinylcholine technique may offer the advantages of more rapid onset of relaxation with only minor increases in intraocular pressure and in a carefully controlled rapid sequence induction technique may be the most acceptable method of handling emergency penetrating eye injuries.

Transdermal hyoscine and postoperative nausea and vomiting

Forty-two patients, undergoing major gynaecological surgery, were randomly allocated to have a patch applied to the skin behind one ear, containing either hyoscine or placebo. They were followed up at 24-hour intervals for 3 days postoperatively and divided into matched pairs for statistical analysis. There was a significant (p less than 0.01) reduction in nausea and vomiting in the first 24 hours postoperatively, but no difference thereafter. There was an increased incidence of visual disturbance in the hyoscine group at 48 hours, but no other differences in the side effects studied at any other time. However, despite receiving hyoscine there was still a high incidence (68%) of severe nausea and vomiting.