Accuracy of Spinal Anesthesia Drug Concentrations in Mixtures Prepared by Anesthetists

OBJECTIVE

Medication errors include the indirect dosing of drugs. For spinal anesthesia mixtures of local anesthetics, opioids are drawn from ampoules and combined in a syringe, according to clinical practice. We set out to determine the accuracy of the drug mixtures.

METHODS

Physicians of our department were invited to prepare the mixture used for spinal anesthesia for cesarean section, consisting of 10-mg hyperbaric bupivacaine (2-mL volume), 20-μg fentanyl (0.4-mL volume), and 100-μg morphine (0.1-mL volume). Concentrations of these drugs were determined by means of high performance liquid chromatography. Interindividual and intraindividual variations were assessed.

RESULTS

We analyzed 96 samples from 31 physicians. Fifty-one percent of the measured bupivacaine concentrations were in ±10% deviation range of the intended concentration; 17% of the fentanyl and 24% of the morphine concentrations were in this range. A total of 2.1% of the samples had a bupivacaine concentration corresponding to a dose of 8 mg or less, and 11.5% of the samples had a morphine concentration corresponding to a dose of 150 μg or greater. Intraindividual variations were 10.9% for bupivacaine, 24.7% for fentanyl, and 38.9% for morphine.

CONCLUSIONS

Our results show a high deviation of the obtained from the intended concentrations. Two percent of the samples had bupivacaine concentrations that probably resulted into an insufficient analgesia, and 11% of the samples had morphine concentrations that, according to guidelines, would require a longer monitoring period than with the intended dose.

Opioid-Free Anesthesia: Physico Chemical Stability Studies on Multi-Analyte Mixtures Intended for Use in Clinical Anesthesiology

Objectives: Opioid-free anesthesia is used increasingly often in hospitals around the world. In this type of anesthesia, opioids are replaced by other analgesics, such as ketamine, lidocaine, dexmedetomidine, and magnesium sulfate. Many clinicians prepare these agents as dual, triple, or quadruple admixtures within a single syringe. However, data on the stability of the individual substances within these preparations over time and in different storage conditions is very limited. Here, we aim to investigate various admixture of dexmedetomidine, ketamine, lidocaine, and magnesium sulfate with respect to the stability of the individual agents over time at different storage conditions. Methods: An ultra-high performance liquid chromatography method coupled to mass spectrometric detection was developed and validated to determine the stability of lidocaine, ketamine, and dexmedetomidine. Quantification of magnesium was carried out in parallel by potentiometric titration. Results: Our results demonstrate the stability of dual, triple or quadruple mixtures of selected substances in 0.9% saline under different storage conditions. Under all conditions, analyzed admixtures remain stable for at least 8 weeks. The quadruple mixture of lidocaine, ketamine, dexmedetomidine, and magnesium sulfate was storable for as long as 148 days without a significant loss of analyte. Conclusion: A new chromatographic method was successfully developed to analyze the stability of various pharmacological agents commonly used by clinicians in opioid-free anesthesia. The data we obtained indicate that mixing these agents together in a single syringe is safe and reliable and suggest that hospital pharmacies may prepare these solutions in advance of planned surgeries.