SUMMARY The prevalence of methane production in an adult population of 256 subjects was 41%, but it was significantly higher in females (49 %), than males (33 %). When the population was subdivided into ethnic groups, Caucasians (48 %) and Blacks (45 %) had significantly more methane producers than Orientals (24%) and Indians (32 %). When the ethnic groups were analysed by sex, female Caucasians had the highest prevalence (58 %), significantly more than Caucasian males, Oriental males, and females and Indian males. In contrast with previous studies, a single dose of lactulose was found to significantly increase breath methane concentrations in six out of 12 methane producers, but not in 25 non-methane producers from the population study. In conclusion, any studies on breath methane must take into consideration the ethnic origin of the subjects and, contrary to previous advice, substrate intake, especially undigestible carbohydrates. Furthermore, a single breath sample may miss up to one-fifth of methane producers.A proportion of intestinal methane produced by anaerobic methanobacteria in the colon is excreted into the breath.' In one series methane was found in the breath in only one-third of a population of 280 adults.' There appeared to be a familial tendency and environmental factors were also thought to play a part. The ingestion of non-absorbable carbohydrates, such as lactulose and raffinose,' 2 appeared not to influence methane production. In this paper we report a study on the prevalence of methane production in a population consisting of four different ethnic groups, together with the acute effect of a single dose of the non-absorbable disaccharide, lactulose, on methane production. Methods SUBJECTSThe pulmonary excretion of methane was studied in a population of 256 healthy volunteers from the staff of two hospitals. The subjects were enrolled by two of us (PP, MFB) touring wards and laboratories asking for volunteers. One hundred and eighteen *Address for reprint requests: Dr L M Blendis, 9th Floor, Eaton Wing, Toronto General Hospital, 585 University Avenue, Toronto, Ontario, M5G 1L7, Canada.Received for publication 29 July 1980 were male and 138 female, with ages ranging from 19 to 59 years with an average of 34 years. None of these subjects was taking antibiotics or laxatives for at least seven days before the sampling. The group was investigated as a whole and then divided into subgroups according to their ethnic origin. This was established by the ethnic characteristics of their appearance and their place of birth. Only three of the 256 subjects (Indians) were related. Duplicate endexpiratory breath samples were collected via a modified Haldane-Priestly tube into 20 ml plastic syringes attached to the side arm of the tube by a three-way stopcock.3 The methane content of both syringes was measured by gas chromatography, using a Carle AGC-311 equipped with a hydrogen flame detector. Breath components were separated at room temperature on a 2 m X 6-10-3 m (length X inner diameter) column, packed ...

SUMMARY Eight stable cirrhotic patients with mild or subclinical portal-systemic encephalopathy (PSE) were studied after shunt surgery when they were off all antiencephalopathic therapy. Equal amounts of mixed proteins were alternated with animal or vegetable protein in a crossover protocol under metabolic conditions for five consecutive, one week periods. The different dietary periods were not associated with either a change in the neurological impairment score or the Trailmaking Tests, which showed a learning effect. The peak frequencies of the computer analysed EEG (CAEEG) were lower during the animal (6.58±0.42 Hz) than the vegetable (7.10±0.44 Hz) diet (p 0.01). Neither arterial ammonia levels nor plasma amino acid ratios changed with the diets, whereas urinary 3-methyl-histidine excretion increased during the animal diet. During the vegetable diet the apparent nitrogen balance tended to be more positive than during either the mixed or animal diets associated with a decrease in the urinary nitrogen excretion. The peak frequency of the CAEEG is the most sensitive test to monitor methods of treatment in portal-systemic encephalopathy. A vegetable protein diet, rather than overall protein restriction, should be considered in the management of this disorder, particularly when the nutritional state is poor.Treatment of mild portal-systemic encephalopathy focuses on prevention of symptoms by protein restriction and, if necessary, by adding lactulose or neomycin. Recently Greenberger1 showed that not only the quantity but also the quality of the dietary protein may be important in the management of the chronic condition. Vegetable derived protein was claimed to be superior to animal protein. Only three patients were studied, however, and two received additional anti-encephalopathic treatment with neomycin, lactulose, or sorbitol. Furthermore, the protocol of the protein administration varied.To investigate the role of dietary protein in portal-systemic encephalopathy we undertook a controlled trial with elimination of all variables apart from the source of protein in the diet. The ' Present address: Karel M de Bruijn, Helpersoon 125, 9722 B7,

In a double-blind study, we have compared the prophylactic antiemetic effect of tropisetron 5 mg (Navoban, a 5-HT3 receptor antagonist) with that of placebo, both given as a short i.v. infusion approximately 15 min before wound closure in patients undergoing gynaecological surgery. Perioperative anaesthetic care was standardized and patients were observed for at least 24 h after operation. The 35 patients given tropisetron and 34 given placebo treatment were well matched for characteristics. Vomiting occurred in 26% of tropisetron-treated patients, compared with 59% of placebo-treated patients (P = 0.006); 69% of tropisetron-treated patients suffered nausea, compared with 88% of placebo-treated patients (P = 0.05). In addition, patients judged the antiemetic treatment with tropisetron as more effective than the placebo treatment (visual analogue score 71 vs 51 mm (P = 0.003)).

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