Determination by LC-MS/MS of colistins A and B in plasma and ultrafiltrate from critically ill patients undergoing continuous venovenous hemodiafiltration.
BACKGROUND
Colistin is a 50-year-old antibiotic, the use of which was ceased in the 70s and recently resumed as a "salvage therapy" against multidrug-resistant gram-negative bacteria, such as Pseudomonas aeruginosa and Acinetobacter baumannii. The narrow therapeutic range of colistin makes the choice of its correct dosage crucial, and monitoring of blood concentration is occasionally necessary for critically ill patients, including intensive care patients subjected to continuous renal replacement therapy.


METHODS
Two LC-MS/MS methods were developed and fully validated for the quantitative determination of colistins A and B in plasma and dialysis ultrafiltrate (UF) samples, ultimately arising from 4 patients undergoing continuous venovenous hemodiafiltration (CVVHDF).


RESULTS
The developed methods proved to be both specific and selective. They showed good fit and linearity over the entire range of interest. Trueness and accuracy proved satisfactory. Both methods have excellent intraassay precision (percent coefficient of variations were lower than 10%) and limit of detection values in the range 20-100 ng/mL, about 1-2 orders of magnitude below the concentrations commonly detected in real samples. The mean sieving coefficient (SC) values, measured after 10 minutes of CVVHDF, were 0.42 for colistin A and 0.48 for colistin B. SC values proved to be quite stable for 24 hours, but then declined to 0.24 for colistin A and 0.32 for colistin B, respectively, after 48 hours. At the median blood flow and effluent flow rate of 120 and 28 mL/min, clearance values for colistin B were higher than 15 mL/min. During the entire duration of CVVHDF sessions, the SC and clearance values for colistin A were significantly lower than colistin B.


CONCLUSIONS
Two simple methods for the simultaneous determination of colistins A and B have been developed and validated. Their application in the clinical setting demonstrates that CVVHDF treatment lasting 48 hours produces a relatively constant and efficient removal of the drug.
*Centro Regionale Antidoping e di Tossicologia "Alessandro Bertinaria," Orbassano; †Dipartimento di Chimica Analitica, Università degli Studi di Torino; ‡Dipartimento di Area Medica, Azienda Ospedaliera "Città della Scienza e della Salute di Torino," Ospedale CTO; §Dipartimento di Emergenza, S. C. Anestesia e Rianimazione, Azienda Ospedaliera "Città della Scienza e della Salute di Torino," Ospedale CTO; ¶Dipartimento di Chirurgia Plastica, Centro Grandi Ustionati, Azienda Ospedaliera "Città della Scienza e della Salute di Torino," Ospedale CTO; and ‖Dipartimento di Medicina Interna, Azienda Ospedaliera "Città della Scienza e della Salute di Torino," Università di Torino, Turin, Italy.
Marta
M
Leporati
Rosaria Ornella
RO
Bua
Filippo
F
Mariano
Paola
P
Carignano
Maurizio
M
Stella
Luigi
L
Biancone
Marco
M
Vincenti
D000900:Anti-Bacterial Agents / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods*; D003091:Colistin / Q000031:analogs & derivatives / Q000097:blood* / Q000493:pharmacokinetics; D016638:Critical Illness; D017583:Hemodiafiltration; D006801:Humans; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000379:methods*; D012680:Sensitivity and Specificity
D000900:Anti-Bacterial Agents; C579082:colistin A, Paenibacillus polymyxa JB05-01-1; C579083:colistin B, Paenibacillus polymyxa JB05-01-1; C004691:colistinmethanesulfonic acid; D003091:Colistin