Metabolic effects of prostatectomy.

Transurethral resection syndrome (TURS), complicating transurethral resection of the prostate (TURP) has been ascribed to hyponatraemia but reports have indicated that hyperammonaemia following metabolism of glycine can be the main cause. Prospective data has been collected on 96 prostatectomy patients (82 TURP and 14 retropubic). The retropubic group showed no significant postoperative change in the serum sodium or plasma ammonia. Of the TURP group, no TURS occurred although hyponatraemia was noted in 32 patients. The weight of prostate resected, the volume of glycine used, the time taken and the plasma ammonia levels were not significantly different in the normonatraemic or hyponatraemic groups. In severely hyponatraemic patients (13 out of 32 with a 10 mmol/l, or greater, decrease in serum sodium) there was a significant rise (P less than 0.05) in plasma ammonia, 1 or 4 h post TURP, which had decreased by 24 h. There was a highly significant increase in serum glycine level in the hyponatraemic compared with the normonatraemic group (P less than 0.001). There was no correlation between serum glycine and plasma ammonia levels in the normonatraemic or hyponatraemic group. There were nine patients with post TURP plasma ammonia levels greater than 100 mumol/l (mean 254) who experienced no mental confusion: six of these patients were hyponatraemic. The weight of prostate resected (mean 26 g), volume of glycine used (mean 181) and operation time (mean 39 min) were all relatively low. Subsequently, TURS has occurred in a patient, with severe hyponatraemia and hyperglycinaemia but no hyperammonaemia. This study shows that hyperammonaemia does not always correlate with hyponatraemia or hyperglycinaemia, and high plasma ammonia levels can occur in the absence of TURS.

Three direct spectrophotometric methods for determination of total bilirubin in neonatal and adult serum, adapted to the Technicon RA-1000 analyzer.

We adapted three bichromatic spectrophotometric methods for determining total bilirubin in serum, for use with the Technicon RA-1000 analyzer. The borate buffer (BOR) of Hertz et al. (Scand J Clin Invest 1974;33:215-30), the caffeine buffer (CAF) of Vink et al. (Clin Chem 1988;34:67-70), and the combined borate-caffeine buffer (B-C) of Franzini and Cattozzo (Clin Chem 1987;33:597-9) were compared. All methods required only 10 microL of serum, were precise (between-batch CVs less than 4.2%, analyte range 64-310 mumol/L), linear to 1000 mumol/L, and insensitive to interference from hemoglobin to 5 g/L. Lipemia, carotene, and methemalbumin interfered positively with each method but insignificantly unless in supranormal concentrations. Only the BOR method was sensitive to protein matrix effect. Neonates' results obtained with all three methods compared well with a Jendrassik-Gróf-based technique. However, samples from adults with cholestasis were overestimated, particularly by the CAF method, but the BOR and B-C methods would be suitable for "stat" bilirubin analysis in these samples.

Evaluation of the Technicon Chem-1.

We evaluated the performance of 15 colorimetric and three ion-selective electrode assays in the Technicon Chem-1 serum analyzer and briefly assessed the suitability of plasma and urine for analysis in the system. Within- and between-batch precision, accuracy, correlation, and linearity of all methods was acceptable but some assays, notably those for bicarbonate and creatinine, were susceptible to interferences. Except for the total bilirubin and lactate dehydrogenase assays, plasma can be assayed successfully in the instrument. Urine samples can also be assayed but specimens for phosphate analysis must be diluted in a polyvinylpyrrolidone solution before analysis, and the calcium method is sensitive to variations in urinary pH.

Obviating interferences in the assay of urinary oxalate.

Evaluation of the Sigma Kit for determination of urinary oxalate highlighted two major limitations of which users must be aware: the pH of urine samples before extraction is critical, and ascorbic acid interferes positively. I give details, and describe simple modifications to the manufacturer's protocol that overcome these problems.