Low dose ketamine analgesia is for opioid tolerant patients or severe trauma Ketamine is best used as a adjuvant analgesic for opioid tolerant patients or in patients with persistent pain despite standard multi-modal treatments. Potentially unstable patients with severe trauma related pain are ideal for ketamine. In some particularly painful conditions such as burns, addition of ketamine may help significantly as well. Ketamine can be given IV, IM, IN, and orally.
Potentially negative pyschoactive reactions are common No awake patient should ever be given ketamine without a detailed and honest warning of possible hallucinations, bizarre thoughts, and emotions that can occur. We find a much reduced incidence of bothersome experiences if the patients are warned ahead of time. Never, ever, "surprise" a patient with ketamine (even at low doses). An infusion or slow push helps reduce the psychoactive effects.
The antidepressant effect is real Many patients will experience a significant elevation in mood (acute antidepressive ) that can last for days to weeks. This raises the possibility to use ketamine as respite for chronic pain patients with depressed mood. Ideally the window of decreased pain, increased functionality, and improved mood is used to advance in treatment (decrease or discontinue opioid, advance in daily functioning, engage in rehabilitation etc...)
While ketamine does not hold near the abuse potential of an opioid, ketamine abuse and seeking clearly occur. Stewardship of its use in the ED is paramount. The general principle is that if pain and suffering can be controlled without the use of a psychoactive medication--opioid, benzodiazepine, ketamine--that should be the preferred strategy.
The Highland guideline is below:
Background on Ketamine
In some form or another cyclooxygenase inhibitors and opioids have been the primary analgesics in medicine for centuries and in the case of opioids, millennia. Ketamine is was only first described in 1965 as a novel general anesthetic with much of the early work on ketamine focused on its role in sedation and general anesthesia. More recently, ketamine at low doses in the 0.1-0.3 mg/kg IV range has gain widespread acceptance as a primary analgesic or adjuvant to opioid analgesia for acute pain. In particular, ketamine has emerged as a first-line agent for severely injured patients at risk of hemorrhagic shock or respiratory depression in emergency and pre-hospital settings. The popularity of ketamine in pre-hospital and emergency settings stems from consistent analgesia with maintenance of the both respiratory drive and reflexes and preservation of cardiovascular stability in all but the most critically ill patients. Importantly, recent evidence suggest that ketamine does not increase intraoccular or intracranial pressure in a clinically significant manner and its many advantages make it the ideal agent for situations such as induction of intubation for head injured patients.
Ketamine is a pharmacologically complex drug with an analgesic pathway totally unique from either opioids or NSAIDs. As such, pain scores do not adequately provide a measure for comparing ketamine analgesia with that of opioids. Importantly, ketamine subjectively provides a local anesthetic quality to the analgesia making it ideal for severely painful injuries that opioids alone would not likely manage without significant sedation. Examples might be burn injuries or fracture reductions. The effects of a ketamine bolus come on quickly (<60 seconds) and are relatively brief (peak within 10 minutes), anesthesia can be prolonged with an infusion.
Like opioids, ketamine analgesia is coupled with sedation. However, the sedation has, even at very low doses, a dissociative quality tending toward hallucinations and complex emotional states. If unexpected, this effect can be unsettling and even frightening. Conversely, with clear coaching before hand, patient satisfaction is very high and unpleasant experiences unusual. Ketamine is an excellent intervention for the agitated and confused traumatically injured patient given the rapid onset of sedation and analgesia with preservation of cardiopulmonary status.
The unique qualities of ketamine analgesia are thought to primarily result from N-methyl-D-aspartate receptor antagonism through which ketamine provides potent analgesia without the respiratory and cardiovascular depression associated with opioids. Interestingly, the clinical analgesic potency of ketamine is clearly strongest in opioid tolerant patients and patients with chronic pain associated with central sensitization. This has lead some authors to conjecture that ketamine is primarily an "anti-hyperalgesic" versus an analgesic per se however, some recent studies of acute pain do suggest a potent primary analgesic effect.
Ketamine is highly lipid soluble with rapid onset of analgesia within 1 minute when given IV or 5 minutes when given IM or intranasally. Ketamine is a mild sympathomimetic that directly stimulates the brain stem and promotes catecholamine release as well as an inhibition of norepinephrine reuptake; this typically results in a moderate increase in heart rate, stroke volume and blood pressure. Additionally, ketamine is both a potent bronchodilator and does not affect respiratory drive or airway reflexes making it ideal for patients in respiratory distress. In summary, ketamine's potent analgesia, synergistic potentiation of opioids, and wide safety margin make it an ideal agent for pain control in trauma patient. Laryngospasm is very rare, but does occur at higher doses.
Agitated delirium ( 4-5mg/kg IM ) Green
Alcohol withdrawal wong et al.
Status epilepticus Zeiler et al.
Acute depression Murrough et al.
Asthma Goyal et al.