Effect of antibody specificity on results of selected digoxin immunoassays among various clinical groups.

We examined the specificity of three automated digoxin immunoassays (Abbott TDxFLx Digoxin II assay, Baxter-Dade Stratus II Digoxin assay, and Ciba Corning ACS Digoxin assay) applied without modification to (a) sera from 229 digoxin-free patients in 12 cohorts associated with nonspecific or endogenous digoxin-like immunoreactive factor (DLIF) interference, and (b) drug-free serum supplemented with the major metabolites and analogs of digoxin. We observed three patterns of apparent digoxin results among the DLIF samples: one common to kidney and liver failure patients, where TDx and Stratus assays showed significant positive results; one common to newborns and cord blood, where only the TDx assay had significant interference; and one from cardiac surgery patients, where the Stratus assay alone showed interference. Of the three assays, the ACS had the least interference from DLIF. The assays also behaved differently with respect to cross-reactivity with digoxin metabolites, digitoxin, and digitoxin metabolites. The ACS assay again had the least analog or metabolite cross-reactivity. The three methods agreed well on digoxin-positive specimens, with a mean bias of <0.15 microgram/L digoxin for each and discrepancies (defined as >3 SD between the assay pairs compared) of only 3-5%.

Citrate anticoagulation during in vivo simulation of slow hemofiltration.

Citrate anticoagulation has been used as an alternative to heparin for hemodialysis in high-risk patients; however, its use in hemofiltration has not been well studied. We examined citrate in 6 patients placed on slow hemofiltration for up to 6 h duration. During the experiments, the systemic citrate level increased from a baseline average of 0.15 to 0.55 mmol/l, and then decreased to 0.27 mmol/l. The citrate was freely filtered. The systemic total and ionized calcium decreased very slightly and no untoward effects were noted. Anticoagulation was successful. This preliminary study suggests that citrate anticoagulation can be used in slow hemofiltration.

Correlation of hemodynamic variables with transcutaneous PO2 measurements in critically ill adult patients.

Transcutaneous oxygen (PtcO2) monitoring with miniaturized heated electrodes has been shown to continuously track arterial oxygen tension (PaO2) noninvasively in stable infants. However, the correlation between the two is less marked in unstable adults, and PtcO2 appears to be additionally influenced by perfusion. The ability of PtcO2 to detect alterations in cardiac index (CI) was evaluated in 19 critically ill adult patients. The PtcO2 was found to be influenced by the PaO2, the CI, and local vascular tone, with a rapid response time to changes in these variables. All instances of improvement in PtcO2 readings were associated with improvement in PaO2 or hemodynamic status. Because of its high sensitivity, continuous noninvasive PtcO2 monitoring should allow reduction in routine PaO2 and CI determinations. However, a decrease in PtcO2 requires immediate in-depth evaluation of the patient's PaO2 and CI because of its lack of specificity.

Transcutaneous bilirubin monitoring of newborns.

Using skin jaundice measurements as an index of infant bilirubin status is subject to a number of uncertainties as described by many investigators. They are illustrated by the experience with a commercial device described here. In view of the widespread need for a quantitative measurement that can replace the visual inspections and subjective evaluations of jaundice being routinely used in clinical settings, such jaundice meters are likely to gain increasing acceptance. We expect future research to include more studies on: (1) reflectance spectra or multiple wavelength measurements for SBI; (2) quality control needed for SBI determinations; (3) the relative significance of physiological factors that influence tissue bilirubin deposits; and (4) the comparative significance of blood versus tissue bilirubin concentrations as true indicators of potential nervous tissue damage.