John Krahn

Transcutaneous bilirubinometry: Its role in the assessment of neonatal jaundice

OBJECTIVE To review the literature on transcutaneous bilirubinometry so that its exact role in the prevention of kernicterus or bilirubin encephalopathy could be determined. DESIGN AND METHODS Literature searches were done in Medline and Current Contents. RESULTS It is estimated that about 50% of newborns have an episode of jaundice in the first few days of life. Six percent of newborns may develop hyperbilirubinemia (> 220 mumol/L), which can potentially cause bilirubin encephalopathy or kernicterus, a severe neonatal disease. In the past, serum bilirubin (SB) has been the preferred method of detecting hyperbilirubinemia in newborns. The ordering of SB in neonates is based on visual evaluation by either physicians or nursing staff. Skin puncture collection of blood exposes the neonate to trauma and risk of infection. A noninvasive device for predicting serum bilirubin levels in newborns diminishes the need to do skin punctures. One such device that has been very extensively studied is the Minolta AirShields Jaundice Meter. It is a portable light-weight instrument that uses reflectance measurements on the skin to determine the amount of yellow color present in the skin, namely transcutaneous bilirubin (TcB). Although the TcB measurements correlate well with serum bilirubin (SB) levels, they cannot accurately predict serum bilirubin because of error related to a variety of factors. CONCLUSIONS TcB cannot be used directly to make decisions about transfusions or phototherapy in neonates. It is a good tool for screening neonates to determine when a laboratory measurement of serum bilirubin is needed. Such a practice requires careful selection of the decision level so that false-negative TcB values do not prevent appropriate serum bilirubin tests from being done.

CLINICAL IMPACT OF TRANSCUTANEOUS BILIRUBINOMETRY AS AN ADJUNCTIVE SCREEN FOR HYPERBILIRUBINEMIA

OBJECTIVE To determine what the clinical impact would be of implementing a jaundice meter for use in a busy neonatal service as an adjunctive screening tool for hyperbilirubinemia. DESIGN AND METHODS Test utilization data was collected for a 6-month period to determine how neonatal bilirubin was utilized in this hospital. The jaundice meter was evaluated in a study population of healthy term infants. The performance characteristics of the meter and the test utilization data were used to predict the clinical impact a meter could have on screening for hyperbilirubinemia. RESULTS Utilization data indicated that about 60% of all single bilirubin neonatal testing (i.e., bilirubin only ordered) was done by normal nurseries. A jaundice meter cutoff decision reading of 17 was shown to have a sensitivity of 100% and a specificity of 68% for hyperbilirubinemia (> 260 mumol/L) in a study population of healthy term infants. From this data, it was estimated that use of a jaundice meter could eliminate 43% of the single (i.e., not combined with other tests) bilirubin tests done on healthy term neonates with no prior exposure to phototherapy. This constitutes an overall 20% reduction in bilirubin testing in normal nurseries when testing done on babies exposed to phototherapy and combined bilirubin testing are taken into consideration. Additionally, it was shown that there would be an improvement of 9% in the prediction of hyperbilirubinemia without loss of 100% sensitivity. CONCLUSION Use of a jaundice meter in normal nurseries as an adjunctive screening tool enhances patient care by reducing the overall blood procurement rate in normal nurseries by 20% and increasing screening efficiency for significant hyperbilirubinemia by 5%.

Troponin I testing in dialysis patients presenting to the emergency room: does troponin I predict the 30-day outcome?

Background: Troponins are often measured in acutely ill chronic dialysis patients admitted to the emergency room, irrespective of their clinical presentation. The significance of an elevated troponin level in this setting is unclear. Methods: We identified all chronic dialysis patients presenting over 1 year to a tertiary care hospital emergency room who also had at least one cardiac troponin I (cTnI) level determination. We evaluated presenting complaints, risk factors for cardiac disease, cTnI levels, and major cardiac events (MCE; occurrence of cardiovascular death, myocardial infarction, de novo heart failure, or coronary revascularization) within 30 days by chart review in 149 patients (79 on hemodialysis, 70 on peritoneal dialysis). Results: Chest pain was documented in only 29% of the patients. Twenty-two patients (15%) experienced an MCE. The incidence of an MCE was the same in patients with and without chest pain. A cTnI level >0.1 ng/l was a significant predictor of an MCE (odds ratio 15.2, 95% confidence interval CI 5.26, 43.6). The likelihood ratios for MCEs were 0.32 (CI 0.16, 0.63) for a cTnI level <0.1 ng/l, 0.72 (CI 0.09, 5.5) for cTnI concentrations 0.1–0.3 ng/l, 7.8 (CI 4.2, 15) for a cTnI level >0.3, and 11.7 (CI 4.4, 31) for a cTnI concentration >2.0 ng/l. Conclusion: In acutely ill chronic dialysis patients presenting to a hospital emergency room, an elevated cTnI level indicates an increased 30-day cardiac risk, regardless of their clinical presentation.

Tobramycin clearance during continuous arteriovenous hemofiltration

Abstract Tobramycin concentrations during continuous arteriovenous hemofiltration (CAVH) were measured in the blood and ultrafiltrate of an anuric critically ill patient. Tobramycin pharmacokinetics demonstrated first order decline. Drug clearance was 0.9 of the ultrafiltration rate. Strategies for calculating dosing intervals of tobramycin in patients on CAVH are described.