Stability of YKL-40 concentration in blood samples

The stability of YKL-40, a mammalian member of the family of 18 glycosyl-hydrolases, in blood samples handled under different temperatures and different time intervals before centrifugation was studied in paired serum and plasma samples from 25 healthy premenopausal Danish women. Significant elevations of YKL-40 were found in 8 paired serum samples left on the clot for more than 3 h at room temperature compared to paired serum samples left on the clot for 3 h or less. Significant elevations of YKL-40 were found in 8 paired plasma (EDTA) samples left on the blood cells for more than 8 h at room temperature compared to paired plasma (EDTA) samples left on the blood cells for 8 h or less. No elevations were found in YKL-40 levels in serum samples left on the clot at 4°C for 24 h or in plasma (EDTA) samples left on the blood cells for 72 h before centrifugation. Significantly lower concentrations of YKL-40 were measured in plasma (EDTA) compared with paired serum samples with a serum/plasma ratio of 1.4 in samples left on the clot or on blood cells at 4°C for up to 24 h. Repetitive freezing and thawing had no significant effect on the measured YKL-40 concentrations. In conclusion, we have shown that YKL-40 is very dependent on the handling procedures. All the blood samples must be processed into plasma (EDTA) within 8 h at room temperature or into serum in less than 3 h at room temperature. If this is not possible, the blood samples must be stored at 4°C until processed.     

Stability of YKL-40 concentration in blood samples

The stability of YKL-40, a mammalian member of the family of 18 glycosylhydrolases, in blood samples handled under different temperatures and different time intervals before centrifugation was studied in paired serum and plasma samples from 25 healthy premenopausal Danish women. Significant elevations of YKL-40 were found in 8 paired serum samples left on the clot for more than 3 h at room temperature compared to paired serum samples left on the clot for 3 h or less. Significant elevations of YKL-40 were found in 8 paired plasma (EDTA) samples left on the blood cells for more than 8 h at room temperature compared to paired plasma (EDTA) samples left on the blood cells for 8 h or less. No elevations were found in YKL-40 levels in serum samples left on the clot at 4 degrees C for 24 h or in plasma (EDTA) samples left on the blood cells for 72 h before centrifugation. Significantly lower concentrations of YKL-40 were measured in plasma (EDTA) compared with paired serum samples with a serum/plasma ratio of 1.4 in samples left on the clot or on blood cells at 4 degrees C for up to 24 h. Repetitive freezing and thawing had no significant effect on the measured YKL-40 concentrations. In conclusion, we have shown that YKL-40 is very dependent on the handling procedures. All the blood samples must be processed into plasma (EDTA) within 8 h at room temperature or into serum in less than 3 h at room temperature. If this is not possible, the blood samples must be stored at 4 degrees C until processed.     

Assessment of the stability of N-terminal pro-brain natriuretic peptide in vitro: implications for assessment of left ventricular dysfunction.

Plasma concentrations of N-terminal pro-brain natriuretic peptide (NT-proBNP) are raised in patients with left ventricular dysfunction. Measurement of this peptide has a potential diagnostic role in the identification and assessment of patients with heart failure. The stability of this peptide over time periods and conditions pertaining to routine clinical practice has not been reported previously. Blood samples were obtained from 15 subjects. One aliquot was processed immediately, and the remaining portions of the blood samples were stored for 24 h or 48 h at room temperature or on ice prior to processing. Plasma concentrations of NT-proBNP were measured with a novel immunoluminometric assay developed within our laboratory. Mean plasma concentrations of NT-proBNP were not significantly different whether blood samples were centrifuged immediately and stored at -70 degrees C or kept at room temperature or on ice for 24 h or 48 h. The mean percentage differences from baseline (reference standard) were +5.2% (95% confidence interval +18.2 to -7.8%) and +0.8% (+15.2 to -13.7%) after storage for 24 h at room temperature or on ice respectively, and +8.9% (+24.2 to -6. 5%) and +3.2% (+15.1 to -0.9%) for storage for 48 h at room temperature or on ice respectively. Pearson correlation coefficients for baseline NT-proBNP concentrations compared with levels at 48 h at room temperature or on ice were r=0.89 and r=0.83 respectively (both P<0.0001). Thus NT-proBNP extracted from plasma samples treated with EDTA and aprotinin is stable under conditions relevant to clinical practice.     

Effect of anticoagulants and storage temperatures on stability of plasma and serum hormones

OBJECTIVES: To determine the effect of different anticoagulants and storage conditions on the stability of hormones in plasma and serum. DESIGN AND METHODS: Human blood samples were collected from volunteers into EDTA, lithium heparin, sodium fluoride/potassium oxalate, or tubes without anticoagulant, plasma and serum left at -20 degrees C, 4 degrees C or 30 degrees C for 24 and 120 hours then assayed for ACTH, aldosterone, alpha-subunit, AVP, CRH, C-peptide, estradiol, FSH, glucagon, GH, IGF-1, IGFBP-3, insulin, leptin, LH, PPP, PTH, prolactin and VIP, or at room temperature for 0 to 72 hours (BNP, NT-BNP)(n = 6 per condition). RESULTS: The anticoagulant altered the measured concentrations for 9 hormones when compared to EDTA. All hormones except ACTH were stable for > 120 hours in EDTA or fluoride at 4 degrees C, but only 13 hormones were stable in all anticoagulants. At 30 degrees C, 8 hormones were stable for > 120 hours in EDTA, and 3 hormones in all anticoagulants. BNP and NT-BNP were stable for < 24 hours when stored in EDTA or heparin at room temperature. DISCUSSION: Storage of samples in EDTA plasma at 4 degrees C is suitable for most hormones (except ACTH) for up to 120 hours.     

Influence of time and storage conditions on plasma HIV viral load measurements

Quantification of human immunodeficiency virus (HIV) RNA in plasma from HIV-infected patients is now widely used as a clinical indicator of disease prognosis and of response to antiretroviral therapy. However, controversy exists as to whether values obtained under different testing conditions could vary significantly, thus jeopardizing the appropriate interpretation of data. Herein, we demonstrate that results obtained after testing plasma versus whole blood, or immediate versus deferred processing, do not appear to influence viral load measurements significantly. Thirty blood samples from HIV-infected patients were analysed. The second generation branched-DNA assay was used for quantification of plasma viral load. HIV RNA remained stable for at least 24 h at room temperature, either in plasma or in whole blood, in 72.4% of the samples (< 0.2 log difference in viral load values) although lower levels of HIV RNA tend to be seen in samples after being stored as whole blood at room temperature. Only 3.4% of samples showed a decline > 0.5 log when they were left as whole blood at room temperature for 24 h in comparison with testing after immediate plasma separation. Although immediate separation and refrigeration of plasma samples may reduce the chance of significant falls in viral load measurements, this level of processing can be limited in regions where clinical blood samples cannot be processed rapidly. Our data provide confidence in the results obtained when testing specimens, either plasma or whole blood, 24 h after venepuncture and storage at room temperature, mimicking the conditions in the transport of blood samples to reference centres.     

Long-term stability of human immunodeficiency virus viral load and infectivity in whole blood

BACKGROUND: We intended to evaluate the stability of human immunodeficiency virus (HIV) type 1 virions in whole blood and in culture medium. MATERIALS AND METHOD: EDTA whole-blood samples taken from 12 patients were left at room temperature for up to 7 days, and aliquots of a laboratory virus stock spiked in EDTA, in heparinized or in citrated whole blood, with or without the addition of Triton X-100, or spiked in culture medium were left at room temperature for up to 120 days before plasma was separated and frozen at -80 degrees C. Viral load was measured for all frozen plasma samples using different viral load assays. p24 antigen and infectivity were also measured in the spiked samples. RESULTS: The patient whole-blood samples did not show any decrease in viral load during this 7-day period. The spiked samples decayed by not more than 1 log after 120 days (about 4 months), with the fastest decay in medium. Virus infectivity decayed very slowly from 20,000 units mL-1 to undetectable amounts after 56 days. CONCLUSIONS: These results indicate that HIV-1 virions in whole blood possess a long-term stability in terms of viral load, p24 antigen level and infectivity, which is not sufficiently recognized by laboratory and health care workers.     

Serum cystatin C in renal transplant patients

BACKGROUND: Waiting temperature before centrifugation and anticoagulants used, markedly effect total homocysteine concentrations. The aim of this study was to investigate the effect of different anticoagulants and temperature on plasma homocysteine levels. METHODS: We studied total homocysteine concentrations in 23 healthy subjects. Blood was drawn in K(3)EDTA, sodium citrate- or sodium fluoride-containing tubes, and kept at 0 degrees C or 22 degrees C for 3 h. Total homocysteine measurements were performed with fluorescence polarization immunoassay (FPIA) method. We compared all results with baseline EDTA values (samples put on crushed ice and centrifuged immediately) recommended in literature for reference handling. RESULTS: At 22 degrees C, the tubes containing sodium citrate and sodium fluoride showed significantly higher total homocysteine concentrations than their respective baseline values (p=0.000). However, sodium fluoride tubes were not significantly different than baseline EDTA levels. Waiting 3 h at 0 degrees C did not effect sodium citrate and EDTA plasma total homocysteine concentrations when compared to baseline EDTA, but sodium fluoride-containing plasma levels were significantly decreased (p=0.000). CONCLUSIONS: According to our results, the most available and practical temperature and anticoagulant for total homocysteine determination is sodium fluoride at room temperature up to 3 h.     

Whole blood samples for adrenocorticotrophic hormone measurement can be stored at room temperature for 4 hours

Introduction: The aim of this study was to investigate and compare the stability of adrenocorticotrophic hormone (ACTH) in whole blood stored on ice and at room temperature for up to 48?hours. This study differs from previous studies by a larger data material.

Materials and methods: EDTA-blood samples from 30 patients were collected, aliquoted and stored on ice or at room temperature for 0, 2, 4, 24, or 48?h before centrifugation, and the plasma was stored frozen until analysis. All samples were analyzed using an automated electrochemiluminescence immunoassay on cobas 6000 e601. The change in ACTH concentration was illustrated as ACTH recovery compared to standard conditions defined as samples stored immediately on ice, centrifuged and plasma frozen within 1?h. A change in ACTH concentration of more than 10% was considered to be of clinical relevance.

Results: The results showed no clinically relevant change in ACTH recovery for up to 4?h compared to standard conditions. For samples stored at room temperature for 4?h, a significant (p?Conclusion: The comparison between samples stored at room temperature for up to 4?h and standard conditions showed that ACTH samples do not require cooling until centrifugation, if a mean difference in ACTH concentration of ?4.3%, between the individual results, can be accepted.     

Stability of prothrombin time and activated partial thromboplastin time tests under different storage conditions

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are common laboratory tests that are useful in the diagnosis of coagulation disorders and monitoring anticoagulant therapy. Recent expansions in the outreach laboratory services at our institution prompted us to investigate the shipping limitations for some tests, including PT and aPTT. Although we followed NCCLS guidelines for the collection of blood specimens, we observed falsely elevated PT and aPTT values due to the different storage conditions. The objective of this study is to determine the effect of conditions and duration of storage on PT and aPTT tests using plasma and whole blood samples, respectively. For this study, 36 plasma samples with normal and prolonged PT and aPTT were exposed to different storage conditions. Blood was centrifuged immediately and plasma was stored at room temperature (RT), refrigerated at 4°C, or frozen at −20°C. The samples were analyzed at 0 h and repeated at 6, 12 and 24 h under various conditions. Although statistically significant differences were observed for plasma samples for normal PT tests after 12 h at refrigerated and frozen storage conditions, the differences would not change the clinical interpretation of the results. On the other hand, samples stored refrigerated or at RT showed significant differences for aPTT at 24 h. These differences would change clinical interpretation, especially for samples with normal or near normal aPTT times. Interestingly, aPTT was significantly higher for samples stored frozen when compared to refrigerated and RT conditions at 6 h. Similar patterns were also observed on ten whole blood samples with normal PT and aPTT values. In conclusion, either plasma or whole blood samples can be accepted for PT testing up to 24 h and for aPTT testing up to 12 h only, when transported either at RT or at 4°C.     

存放时间和温度对凝血功能指标检测结果的影响

目的 探讨标本放置时间和温度对凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、凝血酶时间(TT)、纤维蛋白原(FⅠB)等凝血指标检测结果的影响.方法 选取抗凝静脉血标本50例,血浆用于立即测定凝血4项指标和在室温放置2 h、4 h、6 h和24 h后测定凝血4项指标;并分别于室温、-4 ℃和-20 ℃下保存24 h后测定凝血4项指标.抗凝血室温放置2 h,离心分离血浆后即刻进行凝血指标检测.采用血液凝固仪测定研究指标,采用随机单位组设计资料方差分析比较各组间差异.结果 与留取即刻检测相比,血浆放置2 h APTT、PT、TT和FⅠB等各种指标水平均无明显差异;血浆标本放置4 h开始,APTT、PT和TT等指标出现明显延长,且变化程度随放置时间延长加重,FⅠB水平无明显改变;抗凝血标本放置2 h留取的血浆标本各指标均有明显变化.-4 ℃下血浆标本保存24 h APTT、PT、TT和FⅠB等指标测定结果未出现明显改变,-20 ℃下24 h APTT出现明显延长.结论 对于凝血功能4项指标的测定,采集标本后应及时送检和尽快分离血浆.常温下血浆标本应在2 h内完成测定;-4 ℃下血浆标本保存24 h PT、APTT、TT和FⅠB等指标测定结果未受影响,低温保存应注意避免标本冻融过程.     

Stability of 5-fluorouracil in whole blood and plasma

We studied the stability of 5-fluorouracil (5-FU) in plasma and whole blood kept at room temperature and on ice for 1 to 24 h. At room temperature, there was a steady loss of 94% of the parent drug over 24 h in whole blood and 52% in plasma. In the presence of an excess of uracil, 5-FU was stable for 24 h, suggesting that the loss of 5-FU is the result of enzymatic degradation. 5-FU is more stable in whole blood and plasma when samples are kept cold. For blood and plasma samples maintained on ice, the loss was only 30% and 10% of the parent drug in the respective samples over 24 h. Frozen plasma samples (-20 degrees C) were stable for five weeks. Blood specimens collected for quantifying 5-FU should be immediately placed on ice, and the plasma should be separated and frozen as promptly as possible.     

Evaluation of hepatitis C virus RNA stability in room temperature and multiple freeze–thaw cycles by COBAS AmpliPrep/COBAS TaqMan HCV

To assess the stability of various sample types and storage conditions for quantitative detectability of hepatitis C virus (HCV) RNA viral loads, we studied serum and EDTA/citrate plasma samples obtained from 10 patients known to be positive for HCV RNA. Samples were subjected to the following conditions: 1) 10 freeze–thaw (FT) cycles, and 2) storage at room temperature for 24, 48, and 72 h. Detection of HCV RNA was performed by COBAS AmpliPrep/COBAS TaqMan HCV. The following conclusions were reached: 1) no significantly different viral loads were observed in different blood compartments; 2) no significantly different viral loads were observed after 24, 48, and 72 h at room temperature; 3) no significantly different viral loads were observed after 10 FT cycles in serum and plasma samples; and 4) HCV RNA is quite stable in serum and plasma (EDTA/citrate) samples.     

Critical study of common conditions of storage of glucocorticoids and catecholamines in 24-h urine collected during resting and exercising conditions

BACKGROUND: Except immediate freezing of the samples, no practical method has been validated for preservation of glucocorticoids and catecholamines in 24-h urine collection. Furthermore, the influence of urine storage at bladder temperature during periods of different lengths and the effect of prior exercise on preservation of these hormones in the bladder have not been investigated until now. METHODS: Ten healthy volunteers collected their urine both after a resting and after an exercise session. Urine was aliquoted into tubes which were stored during 24 h in the presence or in the absence of preservatives and at different temperatures. Two samples were stored either 3 or 9 h at 37 degrees C (bladder temperature) without additive. RESULTS AND CONCLUSIONS: When collecting 24-h urine samples for glucocorticoids determination, sample can be stored at room temperature during the 24-h collection period without compromising glucocorticoids preservation. When collecting 24-h urine samples for catecholamines determination, samples have to be chilled without preservative during the whole of the collection period. If the samples have to be stored at room temperature, HCl should be used. Moreover, we report for the first time that catecholamines can be degraded in the bladder and therefore that subjects should urinate every 3 h during either a resting or an exercising day.     

Stability of urinary fractionated metanephrines and catecholamines during collection, shipment, and storage of samples

BACKGROUND: Measurements of 24-h fractionated urinary metanephrines and catecholamines are used for the diagnosis of pheochromocytoma, but adequate information is needed regarding collection, storage, and shipment conditions. METHODS: Spot urine samples were collected from 8 healthy volunteers. Aliquots were immediately frozen at -20 degrees C, or acidified to pH 4 and then frozen either directly or after 24 h at room temperature. The remaining urine was left at room temperature for 24 h and then split into one portion that was acidified and one portion that was not. Aliquots were either frozen or allowed to stand at room temperature for an additional 24, 48, 72, 96, and 168 h before freezing. We also tested the efficacy of adding Na(2)EDTA and Na(2)S(2)O(5), as an alternative to acidification for preservation of the catecholamines. RESULTS: No clinically relevant degradation (<5%) was observed for the fractionated metanephrines under any of the storage conditions. In contrast, in approximately 50% of the untreated samples catecholamines were partially degraded during the first 24 h at room temperature. Immediate acidification, however, prevented degradation, whereas acidification after 24 h prevented further decay. Addition of Na(2)EDTA and Na(2)S(2)O(5) fully prevented degradation of catecholamines during the first 24 h in 4 of 5 cases. In the remaining case, degradation did not exceed 10%. CONCLUSION: Preservation of samples for measurements of urinary fractionated metanephrines is not necessary if samples are assayed or frozen within 1 week, which is an important advantage if transport of samples is necessary. In contrast, urinary catecholamines require preservation measures during collection.     

Plasma ascorbic acid preparation and storage for epidemiological studies using TCA precipitation

Objectives:To introduce a procedure to validate an ascorbic acid method using trichloroacetic acid (TCA) for plasma stabilization at different storage temperatures.Methods:EDTA and heparin plasma were precipitated with TCA (1:5) containing 0.54 mol/L EDTA, or without. Samples were stored at ? 20 °C and ? 70 °C and their stability was tested at room temperature for 24 h.Results:A significant 40% loss (p < 0.001) of plasma ascorbic acid was found when EDTA samples with added EDTA were stored at ? 20 °C for 2–4 weeks compared with storage at ? 70 °C. Ascorbic acid in heparin plasma without added EDTA was most unstable and samples left at room temperature for 24 h lead to almost a total loss of ascorbic acid. Addition of EDTA to the TCA solution improved stability of samples of both plasma types at room temperature.Conclusion:The recommended procedure for ascorbic acid determination in plasma stabilized with TCA is immediate storage at ? 70 °C and inclusion of EDTA into the TCA solution.     

Better stability of total homocysteine measurement with sodium fluoride than with EDTA

The total homocysteine (tHcy) plasma concentration increases 10% per hour when whole blood is collected on ethylene diamine tetraacetate (EDTA) and stored at room temperature. The aim of this study was to investigate the stability of tHcy plasma concentration during 24 hours of storage at room temperature in two different collection tubes: EDTA and sodium fluoride (NaF). The evolution of tHcy plasma concentration was also compared in two different populations: healthy individuals (controls) and patients with end-stage renal failure, known to have increased plasma tHcy concentrations. Plasma was separated from erythrocytes at 0, 2, 6 and 24 hours. tHcy was measured with a competitive immunoassay on Immulite 2000 (Diagnostic Products Corporation). Plasma tHcy concentration started to rise significantly on EDTA after two hours of storage in patients and controls in comparison to baseline (defined as time: 0 hour). It remained stable on NaF during the first two hours and started to rise significantly after six hours of storage for both populations. In conclusion, NaF tubes should be preferred to EDTA tubes for tHcy determination in routine clinical chemistry laboratories.     

Stabilization of ascorbic acid in human plasma, and its liquid-chromatographic measurement

We describe two independent HPLC procedures for the rapid, accurate analysis for ascorbic acid in human plasma. No sample extraction or phase separation is required. We also describe a procedure for preparing a human plasma reference material for use in clinical laboratory analysis for ascorbic acid. The ascorbic acid in plasma can be determined in 15 min, with as little as 50 microL of sample. Analytical recoveries are near 100% with direct injection of deproteinized plasma. Extensive stability data under several conditions, with dithiothreitol as a preservative (antioxidant), indicate that ascorbic acid remains stable in stored plasma for as long as 57 weeks. CVs for round-robin analysis of 11 normal human blood samples by two independent methods were between 0.1% and 5.3%. These clinical samples appear to be stable for at least 50 days under the described conditions of stabilization and sample treatment. Finally, because ascorbic acid prepared by the described procedures is stable at room temperature for at least 18 h, these methods can be readily adapted to clinical laboratory automation at room temperature.     

标本类型和储存条件对促肾上腺皮质激素检测结果稳定性的影响

目的探讨标本类型和储存条件对促肾上腺皮质激素(ACTH)检测结果稳定性的影响。方法将标本分成血浆组和血清组,每组各57例,并在抽血后1h内检测ACTH浓度。在血浆组中选取30例血浆量充足的标本分成室温组、冷藏组和冷冻组,每组各30例,其中室温组和冷藏组在2、24、121h时检测ACTH浓度,冷冻组在24、121h时检测ACTH浓度。检测结果与设定的标准值进行比较分析。结果血清组ACTH水平明显低于血浆组,差异有统计学意义(P0.05)。室温组在2、24、121h时的检测结果与标准值比较差异有统计学意义(P0.05);冷藏组在2、24h时的检测结果与标准值比较差异无统计学意义(P0.05),而在121h时的检测结果与标准值比较差异有统计学意义(P0.05);冷冻组在24、121h时的检测结果与标准值比较差异无统计学意义(P0.05)。结论采用乙二胺四乙酸二钾抗凝标本检测ACTH时,在低温下应于1h内完成检测;若24h内不能完成检测时,应将分离的血浆冷冻储存于-20℃,其在121h内检测结果变化相对稳定。     

Estimation of in vivo capillary or venous blood glucose concentration from analysis on stored venous blood or its plasma and use in quality control of near-patient glucose tests

Glucose concentrations were determined in capillary and venous blood and in venous plasma from 100 consecutive patients referred to an oral glucose tolerance test. The capillary blood was immediately transferred to a haemolysing and glucose stabilizing solution and frozen within 4h. Venous blood was drawn in heparin-sodium fluoride tubes and stored for 0, 4 or 24h at 4 or 20 degrees C. Aliquots of the venous blood were then treated in the same way as the capillary blood. The primary tubes were centrifuged, and aliquots of the plasma were stabilized, as described. All specimens from the same sampling event were analysed in the same analytical series on EBIO compact. Deming linear regression equations y = a + bx were calculated to estimate the glucose concentration in one specimen from that in a differently treated specimen e.g.: B(cB:fPt)---Glucose (0h) = 0.61 + 0.897*P(vB;fPt)-Glucose (24h. 20 C). n = 100, SD(y/x) = 0.25 mmol/L and B(vB) Glucose (0h) = 0.53 + 0.897*P(vB)--Glucose (24h. 20 degrees C), n = 196, SD(y/x) = 0.26 mmol,/L. The non-analytical part of the standard deviation of the ratio between the near-patient test result and its predicted value was 0.038 for both of the above predictions. In conclusion, the analytical (including sampling) variation of near-patient tests of glucose can be assessed by laboratory analysis on mailed, heparin-fluoride stabilized venous blood or on plasma samples made from the mailed blood.     

A Multicenter Study Evaluating the Effects of Sevoflurane on Renal Function in Patients With Renal Insufficiency

BACKGROUND: This multicenter study was undertaken to compare the effect of sevoflurane with that of isoflurane on renal function in 26 patients with pre-existing renal insufficiency. Sevoflurane undergoes hepatic metabolism, with release of inorganic fluoride. Elevated fluoride levels have been associated with renal impairment in patients undergoing methoxyflurane anesthesia raising concerns about the nephrotoxic potential of sevoflurane. METHODS: Patients were ASA II or III class, with renal insufficiency defined by a preoperative serum creatinine concentration of 1.5-3.0 mg/dl. A standardized anesthetic regimen was used consisting of intravenous induction with propofol, vecuronium for muscle relaxation, and fentanyl for analgesia. Patients were randomized to receive either isoflurane or sevoflurane with 100% oxygen. Blood samples were obtained preoperatively and at 24, 48, and 72 h postoperatively for renal/electrolyte determinations. Blood samples for plasma fluoride measurement were obtained preoperatively. RESULTS: Plasma fluoride levels were significantly higher in patients receiving sevoflurane at all measurement points from 0 to 72 h postanesthesia. Mean peak fluoride concentration was 33.4 μM. The maximum fluoride value measured was 51.2 μM. There were no significant differences in postoperative serum creatinine values at any time between patients receiving sevoflurane or isoflurane. CONCLUSIONS: Sevoflurane metabolism produces elevations in plasma fluoride concentrations relative to isoflurane. Despite the increase in plasma fluoride levels, the administration of sevoflurane to patients with renal insufficiency did not produce any adverse effects on renal function as measured by serum creatinine concentration when compared with isoflurane.