Central venous catheters are being used with increasing frequency to administer drugs, and as a result, catheter obstruction caused by precipitation of poorly soluble fluid components has become a common problem. We report our first experience using 0.1 N hydrochloric acid to restore patency to central venous catheters obstructed from insolubility-induced precipitation. Precipitation was caused by drug as well as calcium and phosphorus incompatibilities. The initial use of urokinase in two cases was unsuccessful in restoring catheter patency. In all four cases, the instillation of 0.2-1.0 ml of HCl cleared the catheters. Catheter patency usually was gained immediately. No side effects were noted. Our experience supports preliminary data (JPEN 9 (suppl):255, 1985) which suggest that 0.1 N HCl is effective in clearing insolubility-induced precipitation in central venous catheters.

The addition of cysteine (as cysteine HCl) to a total parenteral nutrition (TPN) solution enhances calcium and phosphate solubility because cysteine lowers the pH of the solution. To determine whether adding cysteine to TPN solutions affected the acid-base homeostasis of infants and increased their need for acetate to obviate acidosis, we studied two groups of neonates--those receiving TPN before (group C) and after (group NC) the addition of cysteine. Measurements were made before and during the first 2 wk of TPN administration. We measured the pH of our standard TPN solution with and without the addition of cysteine. Serum carbon dioxide was significantly lower in group C despite a significantly greater intake of acetate in group NC. In the in vitro study the addition of cysteine to the TPN solution lowered the pH from 5.5 to 5.1. Newborns who received TPN solutions to which cysteine was added had lower serum carbon dioxide values and a greater need to receive acetate than did newborns who received TPN solutions without cysteine.