Ketamine for Analgesia Dosing

Firstly, let’s look at Ketamine as a medication and how it works. Ketamine interferes with incoming signals containing noxious stimulus, or nociception, from the spinal cord and depresses the emotional response that comes with pain perception. Within the brain, ketamine allows impulses to reach the part of the brain that recognizes sensory inputs, but not the part of the brain that associates this with pain. It’s thought to be the reason for ketamine’s dissociative effects, and it is what gives ketamine its analgesic properties, making it effective in the management of acute pain. Chemically, Ketamine is an NMDA receptor antagonist (glutamate is one of the body’s most prominent excitatory neurotransmitters, and NMDA is a glutamate receptor). Blocking NMDA receptors is thought to give ketamine its unique anesthetic properties, as well as amnesia and psychedelic effects. It’s what makes ketamine a useful drug for pain management and conscious sedation where pain needs to be controlled but the patient remains hemodynamically stable and the airway and breathing remain intact.

With this knowledge we can further apply it to the new medical directive that is set to come out in the new ALSPCS 5.4. It is important to look at the dosing regimen based on route of administration that is associated with Ketamine. For both age groups, intravenous administration, ≥ 1 year to < 18 years and for ≥ 18 years the regimen is 0.25mg/kg and for intranasal administration, ≥ 1 year to < 18 years and for ≥ 18 years the regimen is 1.0mg/kg. However, as you mentioned, the maximum single dose for the different age groups varies significantly. Looking through the literature there is not a lot surrounding maximum dosing surrounding Ketamine and it is more centered along weight-based dosing and paying attention to timing intervals whilst still managing the patient’s pain.

It is also important to note the mandatory patch point for all patients < 18 years of age requiring Ketamine. The RPPEO believes in patient-centered care regarding the dosing of Ketamine if it remains within the weight-based dosing regimen for your patient. For example, if your patient is 17 years of age and weighs 80kg and requires pain management with Ketamine and therefore utilizing the 0.25mg/kg IV dosing regimen or 1mg/kg IN dosing. Still, that patch to a BHP is required, simply based on age. Based on the current literature, there’s no strong evidence that clearly justifies the discrepancy between the maximum doses of ketamine. However, children younger than 6 years are vulnerable to the sedating medication’s effects on respiratory drive, airway patency, and protective airway reflexes. Also, prolonged sedation and respiratory depression requiring assisted ventilation were reported in pediatric patients who received high doses of ketamine. Those side effects may justify the conservative maximum dose of ketamine for pediatric patients.

As mentioned, the maximum doses that exist help create a margin of safety for our patients. While the scenario that you speak to is very specific and challenges special circumstances, a boundary for safety is important to consider and utilize.

We would also like to highlight the importance of documentation for this type of call. It is imperative that appropriate weight and age are documented along with pre and post medication assessments. And as always, to consider multi-modal analgesia.

In conclusion, understanding the mechanism of action, effects, and side-effects of the medications that we use are essential in their safe and appropriate use. With accurate history gathering and patient assessment, paramedics can make an informed clinical decision that is patient-centered and safe. Following the Advanced Life Support Patient Care Standards (ALS PCS) regarding Ketamine dosing ensures safe as well as effective patient care and optimized pain control, in specific situations, in the prehospital settings.