Validation and application of single breath cardiac output determinations in man

Cardiac outputs by single breath (Qsb) and Fick (Qf) procedures were compared in five healthy males during supine rest and exercise with Qf ranging from 6-19 L X min-1. The prolonged exhalation (SB) was not controlled. The Qsb calculations incorporated an equation of the CO2 dissociation curve and a "moving spline" sequential curve-fitting technique to calculate the instantaneous R from points on the original expirogram. The resulting linear regression equation for all 38 comparisons obtained (r = +0.76, p less than 0.001, mean difference +/- S.D. = 2.93 +/- 2.72 L X min-1) indicated a 24% underestimation of Qf. A substantial portion of the variability during exercise (n = 28) was due to a difference in alveolar ventilation between the time of the mixed expired (E) gas collection and the SB maneuver. When Qsb was corrected (Qsb) by a linear regression based on the difference between Re and Rsb during exercise and by adding 2.44 L X min-1 at rest (the mean difference), the relationship was greatly improved (Qsb = 0.14 + 0.99 Qf, r = +0.93, mean difference +/- S.D. = 0 +/- 1.47 L X min-1). A subsequent study during upright rest and exercise to 80% of VO2max in 6 subjects indicated a close linear relationship between Q'sb and VO2 for all 95 values obtained (r = +0.94), with slope and intercept close to published studies utilizing invasive cardiac output measurements. Considerations of measured blood gases in relation to estimated values suggested that underestimates of Qf arose, at least in part, from arterial desaturation during the SB maneuver. Detailed computational procedures are provided for implementing this improved Qsb procedure.     

The complications of extracorporeal shockwave lithotripsy: management and prevention

Extracorporeal shockwave lithotripsy has been shown to be a safe and effective method of treating most upper urinary tract stones. Major complications, although few, include haemorrhage, septicaemia, "Steinstrasse" formation and cardiac arrhythmias. The experience from 600 consecutive cases is reviewed and methods of prevention are discussed.     

Quality-of-life instruments in hypertension

This review considers the choice of dimensions to be assessed and the practical problems of measuring quality of life in hypertensive patients. The dimensions of symptomatic well-being, psychological well-being, sleep, sexual function and cognitive function should be assessed. Symptomatic well-being may be measured by many different instruments, and that devised by the authors has been used extensively. The results in different trials may therefore be examined for consistency and sensitivity. Psychological well-being has been assessed by the Psychological General Well-Being Index, the Symptom Rating Test and the Profile of Mood States. The response of these instruments is discussed. The assessment of sleep, sexual function and cognitive function is also described. It is recommended that quality-of-life instruments to be employed in trials of antihypertensive drugs are known to be sensitive to the effects of such drugs.     

Urine colour as an index of hydration in critically ill patients

In order to test the hypothesis that urine colour can be used as an index of hydration in critically ill patients, we selected 40 intensive care and high-dependency patients and correlated urine colour (scored on an eight-point scale) with various indices of hydration: urine:plasma sodium, osmolality and urea ratios, urine output and central venous pressure. In addition, we compared the colour-chart score with scores made by intensive care nurses (without the benefit of a colour chart) in order to test subjective assessment of urine colour. There were weak but statistically significant correlations between urine colour and urine output (Spearman's r = - 0.555) and between urine colour and urine:plasma sodium ratio (Spearman's r = - 0.459). Subjective assessment of urine colour appeared to be reliable. Thus, although urine colour does vary with hydration in the critically ill, assessment of urine colour adds little to the overall assessment of hydration in this group of patients.