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Physical Stability of Propofol-Ketamine Mixture Used For Inadequate Neuraxial Anesthesia During Cesarean Section
Abstract Number: T 31
Abstract Type: Original Research
Background: Administering propofol and ketamine mixed in the same syringe is gaining popularity as a supplemental sedative and analgesic for inadequate neuraxial anesthesia during cesarean sections (1). Propofol-Ketamine mixture is believed to provide both sedation and analgesia, with less unwanted side effects such as injection pain, and cardiovascular and respiratory depression due to the opposing effects of each drug (2). However, propofol is formulated as an emulsion. Propofol’s labeling cautions against mixing with other drugs prior to administration because of the potential instability of the emulsion. We have previously shown no visual and chemical incompatibility of the propofol-ketamine mixture (3). However, a physicochemical compatibility study of propofol-lidocaine mixture suggests that the addition of lidocaine to propofol results in coalescence of oil droplets (≥ 5000 nm) with potential risk of pulmonary embolism (4). The purpose of this study is to detect change in the size of oil droplets in the propofol-ketamine mixture (1:1).
Methods: 20 ml of Propofol (1%, TEVA, North Wales, PA) and 2 ml of ketamine HCl (10%, Hospira, Lake Forest, IL) were mixed in 30 ml plastic syringe. Propofol alone was drawn up separately and used as control. Aliquots of the mixture were taken at different time-points (0, 60, 120, 240, 300, 360 minutes), and droplet size was measured. The droplet size was determined by photon correlation spectroscopy using Zetasizer Nano ZS Zen3600 (Malvern Instruments Inc., Westborough, MA, USA). The measurements were obtained using a He-Ne laser of 633 nm and the droplet size analysis data were evaluated using volume distribution.
Results: The mean oil droplets size of the mixture did not change significantly (≤ 200 nm). See Figure 1.
Conclusions: The addition of ketamine to propofol did not result in significant change of the oil droplets size. The propofol-ketamine mixture used in clinical practice is stable and may not pose risk of pulmonary embolism.
1. Calimaran A, et al. A1336. ASA 2008.
2. Camu F, et al. Best Pract Res Clin Anaesthesiol. 2002;16:475-488.
3. Calimaran A, et al. A694. ASA 2008.
4. Masaki Y, et al. Anesth Analg. 2003;97:1646-51.