[Utility of a CO2 micro-system for diagnosis of acid-base equilibrium disorders in cows with abomasal displacement]

The so-called Harleco apparatus, a micro-system for determination of total CO2, was tested on samples from 200 cows with abomasal displacements. Plasma bicarbonate concentration (pbc) determined with blood gas analysors were used as the reference method.

(1) The pbc of 38.0% of the cows was considered normal (22-28 mmol/l), 51.5% of the cows had metabolic alkalosis (pbc > 20 mmol/l), while 10.5% were acidotic (pbc < 22 mmol/l). (2) Values for pbc determined by the reference method correlated well with values obtained with the Harleco apparatus using plasma (coefficient of correlation 0.804) or whole blood (cc = 0.565). (3) On the basis of sensitivity and specificity, the Harleco apparatus diagnosed alkalosis as reliably as acidosis. (4) The values determined in whole blood were not accurate. (5) The amount of plasma required can be obtained in practice using a micro-centrifuge. (6) Results obtained using a self-prepared reagent were not significantly different from those obtained using the commercially available reagent. (7) Use of a second standard with a bicarbonate concentration close to the sample value did not yield significantly different results than use of a single standard of 25 mmol/l. (8) Increasing the reaction time from 30 sec (according to instructions) to 60 or 90 sec did not yield significantly better results. It is concluded that the Harleco apparatus is a simple, quick, cheap, sufficiently reliable and practical alternative to convential methods for the determination of total CO2 in plasma of cattle.