Extent of agreement in gentamicin concentration between serum that is drawn peripherally and from central venous catheters

A comparison of aminoglycoside antibiotic serum concentrations collected by peripheral veins and peripherally inserted central catheters in adults with cystic fibrosis

BACKGROUND

People with cystic fibrosis (PwCF) are frequently hospitalized for treatment of pulmonary exacerbation. The Cystic Fibrosis Foundation Pulmonary Guidelines support the use of intravenous aminoglycosides with therapeutic drug monitoring for the treatment of pulmonary exacerbation due to Pseudomonas aeruginosa. Serum intravenous tobramycin concentrations are commonly collected by peripheral venipuncture (PV). Discomfort associated with collection of samples by PV prompts collection via PICC, but the accuracy of intravenous tobramycin serum levels collected by PICC has not been documented in adult PwCF. The primary study objective was to evaluate the difference between intravenous tobramycin serum levels collected by PV and PICC in adult PwCF.

METHODS

The authors conducted a prospective case-control study of adult PwCF admitted to University of Utah Health for a pulmonary exacerbation receiving tobramycin by a single lumen PICC. The authors compared tobramycin peak and random serum levels collected by PV and PICC using a detailed flush and waste protocol.

RESULTS

The authors analyzed a total of 19 patients with peripheral and PICC samples. The mean tobramycin peak collected by PV (27.2 mcg/mL) was similar to the mean peak collected by PICC (26.9 mcg/mL) (paired samples Wilcoxon signed-rank test, p = .94). The correlation coefficient was 0.88 (95% CI = 0.85-0.91, p < .001).

CONCLUSION

Tobramycin serum samples collected by PICC appear to be similar in value to PV collections. Collecting aminoglycoside levels by PICC rather than PV may reduce patient discomfort and improve quality of life. Additional multicenter studies are needed to confirm these results.

Aminoglycoside dosing and monitoring for Pseudomonas aeruginosa during acute pulmonary exacerbations in cystic fibrosis

Aminoglycosides are commonly used for the treatment of Pseudomonas aeruginosa (PsA) in the setting of acute pulmonary exacerbations (PEx) in pediatric patients with cystic fibrosis (CF). There are controversies and practice differences between institutions related to aminoglycoside dosing and monitoring strategies. The purpose of this review article is to summarize the currently available literature and identify gaps in the literature related to pharmacokinetic parameter goals, aminoglycoside dosing strategies, and methods for monitoring serum aminoglycoside concentrations for treatment of PsA in CF PEx, and throughout will discuss anticipated changes with the increasing availability of highly effective CF transmembrane conductance regulator modulators. This review focuses on tobramycin, as it is the most commonly used aminoglycoside in CF PEx, and will briefly discuss special circumstances surrounding use of amikacin and gentamicin.

Review of the Preanalytical Errors That Impact Therapeutic Drug Monitoring

PURPOSE

Preanalytical errors comprise the majority of testing errors experienced by clinical laboratories and significantly impact the accuracy of therapeutic drug monitoring (TDM).

METHODS

Specific preanalytical factors in sample timing, collection, transport, processing, and storage that lead to errors in TDM were reviewed. We performed a literature search using several scientific databases including PubMed, ScienceDirect, Scopus, Web of Science, and ResearchGate for human studies published in the English language from January 1980 to February 2021, reporting on TDM and the preanalytical phase.

RESULTS

Blood collection errors (ie, wrong anticoagulant/clot activator used, via an intravenous line, incorrect time after dosing) delay testing, cause inaccurate results, and adversely impact patient care. Blood collected in lithium heparin tubes instead of heparin sodium tubes produce supertoxic lithium concentrations, which can compromise care. Specimens collected in serum separator gel tubes cause falsely decreased concentrations due to passive absorption into the gel when samples are not processed and analyzed quickly. Dried blood spots are popular for TDM as they are minimally invasive, allowing for self-sampling and direct shipping to a clinical laboratory using regular mail. However, blood collection techniques, such as trauma to the collection site, filter paper fragility, and hematocrit (Hct) bias, can adversely affect the accuracy of the results. Volumetric absorptive microsampling is a potential alternative to dried blood spot that offers fast, volume-fixed sampling, low pain tolerance, and is not susceptible to Hct concentrations.

CONCLUSIONS

The identification of preanalytical factors that may negatively impact TDM is critical. Developing workflows that can standardize TDM practices, align appropriate timing and blood collection techniques, and specimen processing will eliminate errors.

Complete Blood Count Collected Via Venipuncture Versus Peripherally Inserted Central Catheter in Hematological Patients: A Comparison of 2 Methods

BACKGROUND

The use of peripherally inserted central catheters (PICCs) in cancer care is increasing over traditional central venous catheters. Nurses frequently collect blood by venipuncture when a PICC is inserted, as there is no available evidence to confirm the reliability of blood tests collected through PICCs in adults.

OBJECTIVE

The aim of this study was to assess the reliability of blood samples for complete blood count (CBC) obtained through PICCs as an alternative to venipuncture.

METHODS

A cross-sectional design was used to recruit adult hematological patients. The blood samples were collected within 5 minutes of each other by a specialist nurse. Hemoglobin, hematocrit, and platelet count were evaluated. To determine method comparison, Passing-Bablok regression, test of linearity, Pearson product-moment correlation coefficient, and Bland-Altman plots were used.

RESULTS

Thirty paired blood samples were collected in 29 hematological patients with a mean age of 66.8 years. A statistical difference was found for hemoglobin (P = .001) and hematocrit (P = .001) levels, but no clinical difference. The regression models revealed no systematic differences and no proportional differences with a linear relationship between the methods. Bland-Altman plots highlighted a good agreement between methods.

CONCLUSION

Blood samples for CBC drawn by PICCs are as reliable as those collected via venipuncture. Blood sampling via PICC could be recommended in people with hematological malignancies in needs of frequent blood tests.

IMPLICATIONS FOR PRACTICE

Sampling through a PICC provides reliable laboratory results for CBC, and it could reduce patients' discomfort and increase the safety of professionals reducing the risk of accidental percutaneous needlestick injuries.

An investigation of enzymatic creatinine interference in a patient receiving dopamine and dobutamine

BACKGROUND

A laboratory investigation was initiated after a renal failure patient had a 2.18 mg/dL decrease in serum creatinine, which was not explained through medical intervention. The investigation revealed specimens providing questionably low results had been collected from a peripherally inserted central catheter (PICC) line.

METHODS

Patient specimens and serum pools were analyzed by the Siemens Vista enzymatic creatinine measurement procedure. A simulation of the patient's infusion protocol examined potential PICC line carryover and specimen collection technique.

RESULTS

A simultaneously collected specimen set, arterial line and PICC line, yielded a difference of 1.86 mg/dL. Infusion and collection simulation studies suggested the most likely scenario was the infusion pump was not shut off while the specimen collection occurred and contaminated the specimen.

CONCLUSION

Providers should be aware of erroneously low creatinine results when administering catecholamine drugs and collecting specimens through the same catheter. The mechanism of specimen contamination is consistent with a siphoning effect from one lumen to the other during collection with the infusion pumps still running.

Therapeutic antibiotic serum concentrations by two blood collection methods within the pediatric patient: A comparative effectiveness trial

Repeated venipunctures and fingersticks to confirm serum drug concentrations cause pain and dissatisfaction for pediatric patients and their families. In many organizations, the standard of care to obtain therapeutic serum drug concentrations by peripheral venipuncture or capillary fingerstick, even when the patient has an existing peripheral intravenous catheter (PIV) or central venous catheter (CVC). The primary objective of this study was to assess agreement between serum tobramycin/vancomycin concentrations collected from a CVC or PIV, versus venipuncture or fingerstick. Among hospitalized pediatric patients (age 3 months to 22 years), 36 paired blood samples were collected. Serum trough vancomycin and random tobramycin concentrations were compared between peripheral intravenous or CVC samples, and venipuncture or fingerstick samples within the same patient. A strict sampling protocol for obtaining the samples was followed, that included collection of the CVC/PIV sample before the venipuncture or fingerstick, less than 2 min between collections of samples from the different sites, and a strict volume-based flush and waste protocol. Concordant correlation coefficients demonstrated substantial agreement between CVC/PIV and venipuncture/fingerstick concentrations for vancomycin (n = 17) and tobramycin (n = 19) (Rc = 0.982 for both). Bland-Altman analyses demonstrated good overall between-method agreement within subjects and minimal bias. Consequently, using a lumen volume-based flush and waste protocol, children with indwelling catheters may not require additional venipunctures and/or fingersticks for confirmation of drug concentrations while hospitalized, improving the quality of care and patient satisfaction.

Peripherally inserted central catheters for calcium requirements after successful parathyroidectomy: a comparison with centrally inserted catheters

BACKGROUND Intravenous calcium supplements are often required following parathyroidectomy to avoid postoperative hypocalcaemia. The aim of this study was to compare application effect of a femoral central venous catheter (CVC) and peripherally inserted central catheter (PICC) on intravenous calcium supplements after parathyroidectomy. METHODS We retrospectively reviewed the hospital records of 73 patients with secondary hyperparathyroidism who underwent a successful parathyroidectomy at the Huashan Hospital attached to Fudan University between 1 April 2011 and 1 February 2016. RESULTS Of the 73 study participants, 39 (53.4%) had a PICC and 34 (46.6%) had a CVC, respectively. Patients in the CVC group needed 6-7 days of intravenous calcium supplements, while patients in PICC group needed only 2-3 days to achieve normal serum calcium concentration (2.2-2.6 mmol/L). Furthermore, the duration of calcium supplementation was 71.62 ± 4.48 hours in PICC group and 100.4 ± 5.43 hours in CVC group (P < 0.05). Of the patients in PICC group, the incidence of catheter occlusion, operation failure and hypocalcaemia was 0%, which was significantly lower than those in CVC group (2.56%, 7.69% and 7.69%, respectively). CONCLUSIONS PICC is a safe and efficient alternative in contrast to CVC for providing venous access for calcium supplementation in surgical patients after parathyroidectomy.

A Comparison of Antibiotic Serum Concentrations Drawn Simultaneously from Peripherally Inserted Central Catheters and Peripheral Veins in Children with Respiratory Infection

The purpose of the study was to evaluate serum concentration of antibiotics drawn from a peripherally inserted central catheter (PICC) compared with a peripheral venipuncture. This prospective comparative study included patients with ages 1month to 21years admitted with a respiratory infection requiring IV vancomycin or IV tobramycin via a newly placed PICC. The difference between the antibiotic levels from the venipuncture and PICC samples was statistically significant for both the peak and trough levels. However, the difference in values was not enough to impact antibiotic dosing and therefore was not clinically significant.

Sources of preanalytical error in pharmacokinetic analyses - focus on intravenous drug administration and collection of blood samples

INTRODUCTION

Pharmacokinetic (PK) studies for long-established drugs are generally performed outside the well-standardized settings of pharmaceutical industry trials. Instead, such studies are usually performed within daily clinical practice of hospitals.

AREAS COVERED

This article describes aspects of intravenous (i.v.) drug administration and blood sampling that contribute to potential sources of preanalytical errors for PK investigations. Parameters that bias determination of start and end time of i.v. infusions, as well as consistent rate of drug delivery, are discussed. Causes for drug loss in the infusion device, including adsorption and insufficient flushing, are outlined. The advantages and disadvantages of different blood sampling techniques are reviewed, with an emphasis on pediatric studies.

EXPERT OPINION

For PK studies that are integrated into the general hospital routine, a variety of potential sources of error exist. Potential pitfalls depend on the specific drug and trial characteristics and they must be anticipated and discussed in advance. Working procedures need to be developed that address the anticipated problems and in detail describe procedures that need compliance between bed and bench.

Clinical impact of laboratory error on therapeutic drug monitoring of once-daily tobramycin in cystic fibrosis: Case series

Once-daily dosing intravenous tobramycin is commonly used to treat cystic fibrosis pulmonary exacerbations. Clinicians often utilize historical therapeutic drug monitoring data to individualize the dose among patients who have been treated with tobramycin previously. This case series involves three patients with cystic fibrosis who had supra-therapeutic tobramycin levels despite use of a once-daily dosing that produced therapeutic drug levels during a previous hospital admission, raising questions about the validity of these levels. Investigation into several potential sources of error led to the discovery of an analyzer error in the laboratory. Once the laboratory’s tobramycin analyzer was recalibrated, the reported levels were comparable to historical levels. This case series emphasizes the clinical importance of critically analyzing reported levels, and specifically, the importance of utilizing past therapeutic drug monitoring data, if available, for all patients treated with intravenous tobramycin. If a patient was therapeutic on a similar dose of tobramycin during a previous admission, a dose adjustment may not be necessary, and clinicians should consider repeating levels while pursuing alternative explanations for the discrepant serum levels.

Comparison of central venous catheter and peripheral vein samples of antibiotics in children with cystic fibrosis

PURPOSE.: To determine if accurate serum antibiotic levels can be obtained from central venous catheters (CVCs) in pediatric patients with cystic fibrosis. DESIGN AND METHODS.: Fifty paired CVC-peripheral vancomycin or tobramycin specimens were collected within 5 min of each other following a 5-ml flush and discard. Specimen samples were randomized by first site drawn. RESULTS.: CVC-peripheral antibiotic levels were highly correlated (r =.97, p <.001), with no statistically significant difference (t = 1.18, p =.25). Bland-Altman plot analysis revealed a bias of.47, with limits of agreement ranging from -4.20 to 6.87. PRACTICE IMPLICATIONS.: Accurate antibiotic concentrations can be obtained from CVCs, reducing pediatric patient trauma and stress.

Minimization of the preanalytical error in plasma samples for pharmacokinetic analyses and therapeutic drug monitoring--using doxorubicin as an example

BACKGROUND

There are many sources of variability in plasma samples drawn for pharmacokinetic analyses or therapeutic drug monitoring. In this article, methods are proposed on how to prevent sample dilution (Part I) and contamination effects (Part II) in plasma samples, using doxorubicin as an example.

METHODS

Experiments were performed in the laboratory setting to identify factors that could influence plasma samples in clinical practice. In part I, it was hypothesized that saline solution left in a catheter could lead to a dilution of samples drawn through this catheter. The impact of 2 different sampling techniques, the "discard method" and the "push-pull method", was examined. In part II, an infusion system was filled with a 1 mg/mL solution of doxorubicin. After rinsing the system with increasing volumes of saline solution, the drug concentration of the fluid left in the system was analyzed. Furthermore, plasma samples were drawn through the drug administration catheter, and the contamination of these samples with doxorubicin left in the catheter was measured.

RESULTS

In part I, a discard volume of plasma equal to 4 dead volumes of the sampling line was necessary to avoid dilution of a sample taken from a port or double-lumen catheter filled with saline solution ("discard method"). Pulling up and down the same volume through the catheter 5 times ("push-pull method") was proved to be an alternative with no need to discard blood. In part II, after rinsing the infusion system with a volume of saline solution corresponding to 4 dead volumes of the system and after discarding a volume of plasma corresponding to 4 sampling line volumes, the doxorubicin contamination in the samples was negligibly small.

CONCLUSIONS

Under the described conditions, the push-pull method delivered the same results as the discard method to prevent sample dilution. To avoid contamination in plasma samples, development of standardized sampling procedures seems to be essential and feasible.

A reliable and safe method of collecting blood samples from implantable central venous catheters for determination of plasma gentamicin concentrations

STUDY OBJECTIVE

To evaluate the extent of agreement between plasma gentamicin concentrations determined from samples collected by using implantable subcutaneous central venous catheters (ports) with the push-pull method and those collected by finger lancet punctures in children with febrile neutropenia.

DESIGN

Prospective, randomized study.

SETTING

University-affiliated, tertiary care hospital.

PATIENTS

Sixty-two children with cancer who had single- or double-lumen ports and who received gentamicin for treatment of febrile neutropenia between February 2008 and October 2009.

INTERVENTION

One blood sample was collected from the port by using the push-pull method at the same time one blood sample was collected by finger lancet puncture for determination of plasma gentamicin concentrations.

MEASUREMENTS AND MAIN RESULTS

Forty-four pairs of samples were available for assessment of agreement, and 43 were available for pharmacokinetic analysis. Agreement between plasma gentamicin concentrations determined from blood samples from ports and finger lancet punctures was assessed by the intraclass correlation coefficient (ICC), Bland-Altman analysis, and comparison of simulated dosage adjustments. Changes in port patency were monitored for 1 week after port sampling. Differences in simulated dosage adjustments calculated by using either the port or finger lancet puncture samples that differed by greater than 20% were considered clinically significant. Agreement between the 44 finger lancet puncture and port sample pairs was excellent (ICC 0.991, 95% confidence interval 0.984-0.995). Port plasma gentamicin concentrations were 4.7% lower than those concentrations determined in blood from finger lancet punctures. The observed limits of agreement ranged from -20.5% to 11%. Differences in dosage adjustments calculated by using port and finger lancet puncture plasma gentamicin concentrations were not clinically significant in 38 (88%) of 43 cases. No changes in port patency were observed in the week after port sampling.

CONCLUSION

The push-pull method of blood sampling is a reliable and safe option for determining plasma gentamicin concentrations in children with ports.

Double-lumen central venous port catheters: simultaneous application for chemotherapy and parenteral nutrition in cancer patients

PURPOSE

This study was designed to evaluate the clinical benefit of low-profile double-lumen port catheters in patients receiving simultaneous chemotherapy and parenteral nutrition (PN). Potential advantages, complications, and the durations of simultaneous and single use of the catheter were assessed.

METHODS

At a university teaching hospital, 10 patients received a double-lumen port catheter (5 men, 5 women; mean age 61.5 ± 12 years). All port implantations were performed under ultrasonographic and fluoroscopic guidance in the radiologic interventional suite. Procedure-related immediate, early, and late complications were recorded until removal of the device, patient's death, or completion of follow-up period. Application times and durations for chemotherapy or PN were determined.

RESULTS

No immediate complications were observed. First use of the port system for chemotherapy was within 12 days (± 25 days, range 0-84 days) and within 17 hours (± 22 hours, range 0-72 hours) for PN on average. During the application of PN, no delay or interruption of chemotherapy was observed. The port catheter was used for the simultaneous application of chemotherapy and PN for a total of 1,216 hours. One port catheter was removed after 30 days due to suspected port infection.

CONCLUSION

Central venous double-lumen port systems as a therapeutic option in patients requiring chemotherapy and PN can increase safety during those simultaneous applications, while offering improved patient comfort.

Approaches to clear residual chemotherapeutics from indwelling catheters in children with cancer

OBJECTIVES

To develop a method for drug dosing and pharmacokinetic (PK) sampling in children with cancer from a single indwelling central venous catheter that minimized drug contamination.

METHODS

A benchtop system was designed to simulate dosing and clearing actinomycin-D (AMD) and vincristine (VCR) from central venous catheters. The authors evaluated the effects of flush volume, composition and pH, timed drug instillation, and number of blood-draw return cycles on residual drug concentrations. A proof-of-principle study was conducted in three pediatric patients with cancer with paired PK samples obtained by both central and peripheral catheters.

RESULTS

Nearly complete removal of drug from the catheter was obtained after five blood-draw return cycles consisting of 5 mL of whole blood. Residual concentration of AMD was 0.18 ± 0.02 ng/mL or 0.16% of the initial infusion concentration. VCR exhibited lower propensity for catheter adsorption than AMD with residual concentrations undetectable after three blood-draw return cycles. In patients in which the clearance procedure was used, higher drug concentrations were generally observed from centrally cleared samples at most time points, but differences relative to peripherally obtained samples were not statistically significant for either AMD or VCR. Two of three patients had higher exposure for AMD based on PK samples obtained from central catheters, whereas exposure for VCR was similar for both sampling catheters in all patients.

CONCLUSIONS

A reliable procedure to efficiently reduce AMD and VCR contamination during PK sampling has been established and is currently being used in a PK study being conducted by the Children's Oncology Group.