Blood gas analysis: effect of air bubbles in syringe and delay in estimation

Two common sources of error in blood pH and blood gas analysis were studied. The effect of delay in estimation was studied in 10 volunteers and 40 patients. Syringes were stored at 0 degree C, (crushed ice), 4 degrees C (refrigerator) and 22 degrees C (room temperature). The pressure of oxygen (PO2) fell significantly by 20 minutes at 4 degrees C and 22 degrees C but did not change significantly at 0 degree C for up to 30 minutes. Blood pH, pressure of carbon dioxide (PCO2), and base excess did not change significantly for up to 30 minutes at 4 degrees C and 22 degrees C and up to 60 minutes at 0 degrees C. The effect of air bubbles in the syringe was studied by leaving a single bubble or froth in contact with the blood for one to five minutes in 40 patients. Po2 rose significantly after two minutes' contact with froth and two minutes' contact with the air bubble, and PCO2 fell significantly after three minutes' contact with the air bubble. Size of the bubble had little effect on rates of change. Blood pH, bicarbonate, TCO2, and base excess did not change significantly after up to five minutes' contact. For accurate estimation of PO2 and PCO2 it is necessary to avoid frothing, to expel all air bubbles within two minutes, and to inject the sample into the machine within 10 minutes or store the syringe in crushed ice. The requirements for blood pH and base excess measurement are less exacting.

Effect of aluminium hydroxide on serum ionised calcium, immunoreactive parathyroid hormone, and aluminium in chronic renal failure

According to the Bricker-Slatopolsky theory, secretion of parathyroid hormone (PTH) is switched on in chronic renal failure by hypocalcaemia due to phosphate retention. In an attempt to reverse this process 20 patients in preterminal renal failure (plasma creatinine 569 +/- 195 mumol/l) were given aluminium hydroxide, 3.8 g daily. They were studied for four weeks and all measurements were made at the start and weekly, except measurements of serum aluminium concentration, which were made at the start and at the end of the fourth week. Mean serum phosphate fell from 1.89 to 1.47 mmol/l (5.9 to 4.6 mg/100), mean serum calcium rose from 2.07 to 2.24 mmol/l (8.3 to 9.0 mg/100 ml), and serum ionised calcium rose from 1.07 to 1.20 mmol/l (4.3 to 4.8 mg/100 ml), but serum immunoreactive PTH did not fall. Thirteen patients had initial serum immunoreactive PTH concentrations at or near to normal and 11 were taking beta-blockers but even in those with neither explanation, PTH concentrations did not fall. Serum aluminium concentrations rose from 0.4 to 1.02 mumol/l (10.9 to 27.4 microgram/l). Aluminium hydroxide corrects serum phosphate, total calcium, and ionised calcium at the price of a rise in serum aluminium concentration; in this study it did not affect serum immunoreactive PTH. The Bricker-Slatopolsky theory still needs verification in studies of patients with chronic renal failure.

Heparin effect on ionised calcium concentration

The effect of heparin on plasma ionised calcium was studied by adding it in increasing amounts to whole blood from 10 normal subjects. There was no significant change in ionised calcium from the addition of 1 U/ml but a significant fall of 0.02 mmol/l when 2 U/ml were added and a progressive further fall with increasing concentrations. Heparin from three different manufacturers produced similar results. The effect of heparinisation in vivo was studied during regular haemodialysis on 10 patients with chronic renal failure. Following intravenous injection of 10 000 U of heparin there was a consistent and significant fall averaging 0.03 mmol/l.

"Eosinophilic" peritonitis in continuous ambulatory peritoneal dialysis (CAPD)

Three cases of "sterile" peritonitis in CAPD patients are discussed, where the predominant white cell type in the peritoneal dialysis fluid was the eosinophil. No bacterial or fungal organism was isolated on repeated culture of the dialysis fluid and all had a benign course. The eosinophilic response appears to occur very soon after starting CAPD, is relatively asymptomatic and does not require antibiotic therapy. It is suggested that the eosinophilia is related to allergy to some constituent of the peritoneal dialysis system.

Renal transplantation in patients on continuous ambulatory peritoneal dialysis

Over a two year period 15 patients on CAPD and 65 patients predominantly treated by haemodialysis received first grafts. There was no difference in graft survival in these two groups. In the continuous ambulatory peritoneal dialysis (CAPD) patients there were no post operative episodes of peritonitis, apart from one patient who had peritonitis at the time of transplantation. No technical difficulties were encountered at the time of grafting. CAPD is not a contraindication to transplantation.