Plasma Volume Determination in the Hypovolemic State Produced by Intraperitoneal Injection of a Non-Electrolyte Solution

It was noted in previous work(1), that following the subcutaneous injection of non-electrolyte containing fluids there were certain discrepancies in plasma volumes as determined by the RIHSA∗ method. These were manifested by failure to obtain reduction in plasma volume commensurate with the rise in hematocrit, and clinical signs of hypotension and dehydration. One of the possible factors considered was an abnormal rate of disappearance of the radioactive albumin in this pathophysiologic state. It was thought to be worthwhile to investigate the disappearance of radioactive iodinated protein under controlled conditions in the dog when a non-electrolyte carbohydrate solution was given intraperitoneally.

Methods. Six mongrel dogs weighing 18 to 20 kg on the standard kennel diet were studied. Control plasma volumes were obtained utilizing the radioactive iodinated albumin method previously described(2). The radioactive I¹³¹ protein was prepared from dog plasma according to the method of Fine and Seligman(3). In unanesthetized animals a polyvinyl catheter was introduced into the external jugular vein through a No. 13 needle and taped in position. A short No. 18 needle was wedged into the lumen of the catheter for convenience in sampling. Twenty cc of the radioactive plasma were injected into the opposite external jugular vein and periodic samples were withdrawn from the catheter for 30 minutes. The blood samples were placed in heparinized tubes and centrifuged at 2500 rpm for 30 minutes. The radioactivity of the supernatant plasma was determined and expressed as counts per minute. Plasma volumes were calculated from the 10 minute sample(2). After 30 minutes a 10% invert sugar solution† 25 ml/kg, was introduced into the peritoneal cavity through a No. 18 needle. This infusion required 10 to 15 minutes. At 1, 2, 3, and 4 hours after the intraperitoneal injection simultaneous blood and peritoneal fluid samples were obtained. The radioactivity of one cc aliquot of these samples was determined as described above. In addition, the following chemical determinations were made on the samples: sodium and potassium concentration using a Barclay flame photometer and chloride concentration by the method of Schales and Schales(4). Four hours after the intraperitoneal infusion, 20 cc of radioactive plasma were again injected into the external jugular vein after obtaining a control blood sample, and periodic blood samples were collected from the polyvinyl catheter for 30 minutes.