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Pharmacokinetic analysis of cloxacillin loss in children undergoing major surgery with massive bleeding
1Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Massive blood loss during surgery significantly reduces cloxacillin levels, potentially below effective concentrations. Standard dosing is inadequate, requiring adjustments to maintain therapeutic antibiotic levels in patients undergoing extensive procedures.
Area of Science:
- Pharmacology
- Surgical Medicine
- Pediatric Anesthesiology
Background:
- Craniomaxillofacial surgery can involve extreme blood loss, potentially exceeding total blood volume.
- High-volume fluid and blood product replacement during surgery dilutes drug concentrations.
- Maintaining adequate antibiotic levels is critical for preventing surgical site infections.
Purpose of the Study:
- To quantify cloxacillin loss during craniomaxillofacial surgery with substantial blood loss and fluid replacement.
- To compare cloxacillin pharmacokinetics in pediatric surgical patients versus healthy adults.
- To assess the adequacy of standard cloxacillin dosing in this surgical context.
Main Methods:
- Pharmacokinetic analysis of cloxacillin in children undergoing craniomaxillofacial surgery.
- Comparison with cloxacillin disposition in healthy adult volunteers.
- Estimation of drug loss based on serum concentration changes and known administration.
Main Results:
- An estimated mean cloxacillin loss of 71% was observed in surgical patients.
- Serum cloxacillin concentrations frequently fell below the minimum inhibitory concentration (MIC) for Staphylococcus aureus.
- Drug loss was significantly higher compared to healthy volunteers with normal hemodynamics.
Conclusions:
- Traditional cloxacillin dosing is insufficient during prolonged surgeries with massive blood loss.
- Frequent redosing or drug-primed replacement fluids may be necessary to achieve therapeutic levels.
- Massive blood loss dramatically impacts drugs with small distribution volumes, necessitating prompt replacement of essential medications.
Abstract:
To determine the magnitude of cloxacillin loss during surgical procedures involving significant blood loss and high fluid replacement, we compared the pharmacokinetics of cloxacillin in children during craniomaxillofacial surgery with the disposition of the drug in healthy young adult volunteers with intact circulation. Blood loss during craniofacial operations may exceed blood volume, in some cases by as much as three times. Hemodynamic replacement with electrolyte solutions and blood products, which do not contain the drug, further dilute cloxacillin concentrations. In the patients that we studied, mean drug loss was estimated at 71%. Cloxacillin concentrations in serum fell below the lower range of the MIC for Staphylococcus aureus during significant portions of the surgical procedures. Thus, the traditional dosing of cloxacillin during prolonged operations with massive blood loss is inadequate. A more frequent dosing interval or priming of all replacement fluids with the drug may be required to maintain therapeutic levels. Our findings suggest that massive blood loss is likely to have a dramatic effect on the level of any drug with a small distribution volume. If such a drug is essential to the patient's well-being (e.g., antibiotics, antiarrhythmics, and anticonvulsants), it must be replaced promptly.