A simple spectrophotometric method for the quantification of residual haemoglobin in platelet concentrates

BACKGROUND AND OBJECTIVES: High levels of residual haemoglobin (Hb 0.1 g/l) are known to decrease the efficiency of pathogen-inactivation systems. We evaluated three separate methods to quantify Hb in platelet concentrates (PC). MATERIALS AND METHODS: Nine PC prepared in platelet additive solution (PASIII) (median platelet yield of 283 x 10(9)/unit, range 46-353) were spiked to known Hb concentrations with whole blood and the samples were measured by using each of three methods: the 3,3',5,5'-tetramethylbenzidine (TMB) oxidation method (Sigma Diagnostics, 527-A); the Harboe spectrophotometric method; and the HemoCue plasma low-Hb photometer (PLHP). RESULTS: The TMB and Harboe methods showed linear results compared to expected Hb (r2 > or = 0.981, P < 0.001) over the range tested (0.09-0.28 g/l) when the samples were haemolysed. The TMB method underestimated by an average of 6%, at and around 0.1 g/l Hb, compared to a 4% overestimation by the Harboe method and a threefold overestimation by the PLHP. The Harboe intra-assay coefficient of variation was < or = 1.85% across all concentrations, which contrasted with 30% at and around 0.1 g/l for the TMB method. CONCLUSIONS: The Harboe spectrophotometric method is convenient, safe, accurate and reproducible, and outperforms the TMB and PLHP methods for quantification of residual Hb in PC.     

A simple method of exercise testing patients with ventilatory impairment on the bicycle ergometer

The relationship between symptoms and objective findings is often poor in patients with ventilatory impairment and reduction in exercise tolerance. It is often difficult to know at what level to set the task, when attempting to do submaximal exercise evaluation in such patients. A method for assessing whether performance is appropriate for ventilation, which would also predict a reasonable level to set a submaximal exercise test, would be of value. A test has been devised to satisfy these requirements and is described in this paper. Patients were exercised on a bicycle ergometer using a rapidly progressive geometrical scale increasing the load at 10-second intervals. In 760 patients with airflow obstruction the work done was correlated with the forced vital capacity (r = 0.80). In 169 subjects the test was used to predict a satisfactory level for submaximal testing. Using two thirds of the maximum load achieved 70% of subjects achieved the task exercising for more than 5 min and reaching a pulse of greater than 130. The test has proved to be a satisfactory method for assessing whether performance is appropriate for measured ventilation and as an indicator of the right level at which to set a submaximal exercise test.     

A simple biological way to screen dopaminergic agonists

The velocity of propagation of thein vitro retinal model of spreading depression is very sensitive to changes in the ionic composition of the extracellular medium and also to the the addition of different drugs. 10 .M of SKF 38393, a D1 agonist, increases the velocity of propagation of the wave while 10 M of Quinpirole, a D2 agonist, decreases it. Both changes are blocked by their specific antagonists, SCH 23390 and 1 -sulpiride respectively. This assay can biologically screen potential dopaminergic drugs indicating its physiological D1 and/or D2 preferred effect in the tissue for future analysis by other different methodolgies.     

A simple method of anorectal manometry

Anorectal manometry is usually performed with an open-tipped tube or a closed balloon system. To overcome the well known measurement problems and errors associated with fluid-filled catheter systems and balloons, a pressure tranducer was used to perform anorectal manometry. This method, performed on more than 200 individuals with different anorectal disorders, is described. This was found to be a simple, reliable and reproducible method for anorectal manometry.     

A simple method of checking the ECG paper speed

A simple method of determining accurate rates on ECG machines has been described. A short-wave radio, capable of tuning station WWV (5, 10 or 15 MHz) and a telephone amplifier may be used to place the precise 1 second intervals pulses on the ECG, from which exact paper speed is determined. This information may then be used to calculate the precise rate of an implanted pacemaker stimulus for evaluating pacemaker battery life.