Heparin Lock Research Articles

Heparin lock as a secondary iv line.

From The Department of Surgery, Maimonides Medical Center and Coney Island Hospital, Brooklyn, N. Y. 11219.

Technical pitfalls in measurement of venous plasma NH3 concentration.

Measurement of venous plasma NH3 in normal subjects by the ion-exchange method of Forman [Clin. Chem. 10, 497 (1964)] in a hospital clinical laboratory gave a mean value of 640 mug/liter (range, 300-1320 mug/liter; intraassay, intra-individual, and inter-individual coefficients of variation, 8, 47, and 47%, respectively). The following conditions adversely affect the reproducibility of the test: pollution of laboratory atmosphere and glassware by NH3-containing detergents; smoking by patient or analyst; delay, turbulence, or use of heparin lock in venipuncture; delay or warming of plasma above degrees C before mixing it with resin; and delay in colorimetric analysis of resin eluate. When these sources of error were eliminated, the mean value for normals was reduced to 330 mug/liter, the range was narrowed to 220-470 mug/liter, and the above-mentioned CV's were 5, 16, and 17%, respectively. With the precautions cited, furthermore, the intra-assay and intra-individual CV's for fasting NH3 concentration in cirrhotic patients were similarly reduced. An NH3 tolerance test was done by administering a standard dose of NH4Cl to patients and measuring venous plasma NH3 at 0, 15, 30, 60, and 90 min; the NH3 tolerance was quantified from the area under the curve relating concentration to time (mug - min/liter). As measured in the clinical laboratory, NH3 tolerance of cirrhotic patients showed intra-assay and intra-individual CV's of 50 to 90%. When the tolerance tests were repeated in the same subjects with the laboratory precautions listed above, these CV's were reduced to 8-15%.

Keys to using the heparin lock.

Keys to using the heparin lock.

The plastic heparin lock

A technic for heparin lock, utilizing a plastic needle for decreased vein irritation, is reported. All materials are from those presently in stock in most hospitals or are readily available from suppliers.

Heparin Lock-Induced Alterations in the Activated Partial Thromboplastin Time

The placement of heparin locks can result in marked transient alterations in the activated partial thromboplastin time (APTT). This is noteworthy because of the current interest in mini-dose heparin regimens for preventing venous thrombosis and the recommendation that base line values for the APTT be obtained before starting therapy.

Use of a "heparin lock" in the intermittent administration of intravenous drugs. A technical advance in intravenous therapy.

Use of a "heparin lock" in the intermittent administration of intravenous drugs. A technical advance in intravenous therapy.