MSM 004 Ketamine for everyone

Science is, if nothing else an ever-evolving and changing field. Often we find ourselves looking back on interventions that were shunned by the medical community and wonder why we stopped using them. In the past decade we have seen advancements in medical treatment for drugs that were shunned from medical culture and the population writ large as useless or ineffective (see: Marijuana), only to find that the substance in question may actually have some very important medical uses. Ketamine is a drug that has been getting a lot of attention in the emergency medicine community since 2014. Let’s take a closer look.

Ketamine’s storied history began as a simple molecule that the pharmaceutical company Parks-Davis was looking to monetize. Originally developed as the compound phencyclidine and marketed as Sernyl, the drug was used as an anesthetic for animals. When the drug found favor in the medical community for human consumption, it was found that patients would remain awake under the anesthetic, but would experience profound hallucinations. The drug would eventually be used illicitly under the street name “angel dust” and would be classified as a Class A drug, and its used diminished. Ketamine has a similar chemical structure to phencyclidine, but has milder effects. The drug, like phencyclidine would eventually be abused as a club drug and would lead to fatalities when combined with other drugs.[1] This led to the bad name that Ketamine has received despite emerging evidence that the drug has important medical uses.

The mechanism of action of Ketamine is not fully understood, but it is known that a widespread block of NMDA and HCN1 receptors achieves analgesia and sedation. This mechanism is useful in emergency medicine as Ketamine is one of the few anesthesia medications that also produce an analgesic effect. When given in doses of 1-2mg per kg, it has been found that patients will experience sedation and pain control, while maintaining airway patency and systolic blood pressure.  Evidence suggests that Ketamine is an effect treatment for chronic pain, and there is also evidence supporting the use of Ketamine as an anti-depressant, administered weekly. [2]

In the emergency department and in the pre-hospital setting, we are primarily concerned with achieving pain control and airway control in the setting of rapid sequence induction for intubation. It has been found that when used as an adjunct medication for opioid medications such as morphine that the use of Ketamine reduces total doses of medications, as well as superior pain control when compared to opiates alone. [3] Further studies exploring the pain control qualities of Ketamine have been produced, however it can be difficult to establish the efficacy of pain control in studies that involve patient surveys. The most commonly referenced study is by Beaudoin et al in 2014[4] which analyzed different doses of low-dose Ketamine for pain control (0.15 mg/kg and 0.3 mg/kg) and found similar results to studies that have been produced since. The more data that is published about low-dose Ketamine for pain control, the more evidence there is to support the use of Ketamine for pain control.

As with many other drugs, Ketamine may be used through various routes of administration, primarily IV and IM. The IM dose of the drug tends to 4 mg/kg, which may seem like a shockingly high dose for many people that are reluctant to use the drug. However, it has been found that there is no significant difference in complications after giving the drug IV or IM[5], and there is some anecdotal evidence that administering 4 mg/kg IV to facilitate an awake intubation or RSI may be clinically appropriate and effective.

To summarize, Ketamine is a drug that has a terrible reputation for its past. However it is becoming more and more clear as more research becomes available that we are beginning to run out of reasons to not give the drug. In fact, in the near future, we may have more reasons to administer Ketamine than we will have to withhold it.

[1] Cotton, Simon Ketamine Chemistry World February 19 2014

[2] J. Sleigh et al. / Trends in Anesthesia and Critical Care 4 (2014) 76-81

[3] Bowers et. al. Academy of Emergency Medicine Feb. 8 2017

[4] Beaudoin FL, Lin C, Guan W, Merchant RC. Low-dose ketamine improves pain relief in patients receiving intravenous opioids for acute pain in the emergency department: results of a randomized, double-blind, clinical trial. Acad Emerg Med. 2014;21(11):1193-202

[5] Momeni et al Int J Crit Illn Inj Sci. 2014 Jul-Sep; 4(3): 191–194