Sources of error in acid-base analysis from a blood gas analyser result: a narrative review.

Preservation of blood pH within a narrow range is essential to optimal physiological function. This narrow pH range is maintained via the interactions of various buffer systems. Blood gas analysis is thus essential in the diagnosis and management of disorders affecting blood pH. Common methods of acid-base interpretation in veterinary science are the traditional approach, the physicochemical approach and the semiquantitative approach. However, blood gas analysis is prone to error during the preanalytical, analytical and post-analytical phases of the laboratory process. The pre-analytical phase incorporates steps in obtaining the sample, thus sources of pre-analytical error are related to operator technique. Most errors occur during the pre-analytical phase. Pre-analytical errors include entrainment of air bubbles into the sample and delays between sampling and analysis, both of which cause inaccurate measurement of oxygen and carbon dioxide tensions. The analytical phase outlines processes within the analyser. Common analytical errors are related to substances confounding analyte measurements. The post-analytical phase mainly describes interpretation of the results. Some of the approaches to acid-base interpretation require extensive post-analytical calculations, thus lending themselves to error. Errors occurring during the prior phases will be amplified. Errors in the measurement of the carbon dioxide tension (from which bicarbonate concentration and base excess are calculated) will introduce error into all three methods of acid-base interpretation. Furthermore, errors occurring in the measurements of electrolytes and lactate will result in incorrect interpretations if the physicochemical and semiquantitative approaches are applied. The potential sources of error during the various phases are reviewed.

Clinical assessment alone will not benefit patients with coronary heart disease: failure to achieve cholesterol targets in 12,045 patients--the Healthwise II study.

Healthwise II, a nurse-led audit programme in primary care during 1999-2002, assessed the uptake of secondary preventative measures for coronary heart disease (CHD). Risk factors, cardiovascular medications and blood cholesterol were recorded; 'at risk' patients were invited for a review after 6 months. Of 17,570 patients assessed, CHD was clinically present in 12,045 (69%); in these, aspirin usage was high (78%) but fewer patients were on a beta-blocker (40%), angiotensin-converting enzyme inhibitor (27%) or statin (49%). Blood pressure (BP) was controlled (<140/90) in only 41% of patients. Total cholesterol was >5 mmol/l in 49% of all CHD patients, half of whom were taking a statin. In the statin users, total cholesterol was uncontrolled (>5 mmol/l) in 38%. At follow-up, BP control remained at 42%, statin use increased to 57% and cholesterol remained elevated in 46%. Simple assessment in an audit programme fails to trigger change, and risk-factor modification for CHD remains inadequate.

Referral to hospital: perceptions of patients, general practitioners and consultants about necessity and suitability of referral.

A sample of new referrals from general practitioners to hospital specialists was examined from the points of view of the patient, general practitioner and consultant concerned with regard to the adequacy of the general practitioners' performance before referral, his ability to have managed without referral and the suitability of the specialist seen. Little agreement was found between the opinions expressed by the three groups, although some of the opinions expressed within the groups were found to be associated with characteristics of the groups.

Reasons for referral to hospital: extent of agreement between the perceptions of patients, general practitioners and consultants.

A sample of referrals to hospital out-patient clinics by general practitioners was examined from the points of view of the patient, general practitioner and consultant with regard to the perceived reason for the referral. A considerable degree of disagreement was found between the opinions of the three parties involved. Possible explanations for, and the consequences of this lack of agreement are considered and certain remedies suggested.

General practice management of childhood urinary tract infection.

The incidence of urinary tract infections (UTI) in the paediatric population of a group practice was recorded. A questionnaire involving two case studies was sent to general practitioners and paediatric consultants in the region to assess the management of children suspected of having UTI and the attitudes to referral of these cases to the paediatrician. Disturbing inconsistencies in the management plans were found among both general practitioners and consultants. The reasons for these inconsistencies and the implications arising from them are discussed.

An examination of the prescribed therapeutic experience of five-year-olds in general practice.

The number and therapeutic grouping of prescriptions given to children before reaching their fifth birthday were examined. The records of 92 children were looked at. Between them they had received 1,241 individual prescriptions of which 33 per cent were for antibiotics, and 31 per cent for an antihistamine or cough linctus. Ninety-six per cent of the children had received at least one course of antibiotics and the average child 4.5 courses (SD +/- 3.9); 89 per cent had received an antihistamine or cough linctus, and 50 per cent a skin preparation.