Dr. Steven Zeichner of the Colorado Society of Anesthesiologists (CSA) raised a number of issues on behalf of CSA concerning the use of ketamine in the prehospital setting. (See Appendix H) Among them, Dr. Zeichner argued that the dose of ketamine authorized by CDPHE and administered by paramedics in the prehospital setting exceeds any amount of anesthesia he has administered for general anesthesia. He also contended that paramedics are administering ketamine doses that exceed the “recommended dose” of 3-5 mg/kg IM. Dr. Zeichner relied on CDPHE data from 2019 to conclude that intubation and complications rates for prehospital administration of ketamine for “excited delirium'' indicate either that paramedics are administering excessive ketamine doses, or that patients who received ketamine suffered from medical conditions or drug complications that predisposed them to respiratory depression. Dr. Zeichner suggested that paramedics should titrate ketamine doses to avoid these adverse events.
Some of CSA’s concerns mirrored issues the panel has addressed in this report, such as the appropriateness of using ketamine in the prehospital setting, dosing levels, and the effect of implicit and explicit bias on ketamine recipients. Panel members, including two anesthesiologists, addressed CSA’s outstanding issues during their discussions. Some of CSA’s concerns stem from differences in practice settings. For example, the anesthesia suite allows doctors to exercise significantly more control over the patient. Hospital providers typically have ample personnel support and know the patient’s weight, pre-existing medical conditions, medication history, and vital signs. This knowledge allows doctors to administer a more calibrated amount of ketamine. Moreover, intravenous injection of anesthetic is almost exclusively the mode of administration in the hospital setting. Unlike in a hospital setting, it is not practical to titrate ketamine with an agitated prehospital patient requiring chemical restraint. The different environment in which providers administer ketamine not only accounts for the distinct methods by which ketamine is administered, but also explains why dosing amounts differ.
PANEL RECOMMENDATIONS
Paramedics should administer a standard, fixed dose of ketamine in the prehospital setting based on the patient’s body stature, rather than a dose defined strictly by mg/kg and an estimate of the patient’s weight.
Dosing of 300/400/500 mg IM is a safe dose for the small/average/large male patient, respectively, assuming appropriate patient-side monitoring and trained personnel to manage any complications that may arise. Similarly, dosing of 250/350/450 mg IM is safe for the small/average/large female, respectively, again assuming appropriate patient-side monitoring and trained personnel to manage any potential complications. Estimating a person's weight is therefore simplified to determine if a patient is of small (< 25th percentile), average (25th - 75th percentile) or large (>75th percentile) size.
CDPHE should consider modifying these recommendations as better scientific evidence arises that clarifies the appropriate dosing of ketamine for chemical restraint. More research on appropriate dosing of ketamine is needed, including whether a higher dose may lead to better first dose sedation, whether the risk of respiratory depression is higher with such an intervention, and whether a single standard dose, rather than a three-level standard, is safe and effective across all body sizes.