The Aussie Anesthetic: Why the U.S. should consider equipping medics with ketamine

 

 
 
 

Stephen Rashford , MBBS, FACEM | From the March 2009 Issue | Thursday, March 12, 2009


Models of prehospital care differ across the globe, but the provision of adequate analgesia, particularly for extremely painful and complicated orthopaedic injury, should be a universal goal for all contemporary EMS systems. For many years, this expectation has been met in hospitals with ketamine. Now, the ketamine tide is coming in for paramedics in Australia, with a number of

services trying it out. The drug was introduced to my own agency, Queensland Ambulance Service (QAS), six months ago. I_ll explain why your service should consider adding it to your protocols.

Ketamine Basics

Developed in the 1960s, ketamine is best described as a dissociative anesthetic agent that, in small doses, provides potent analgesia, well beyond the level offered by narcotic agents. It_s an NMDA receptor antagonist that acts primarily within the limbic system. It essentially disrupts ascending pain stimuli and affects the brain_s ability to interpret, thus disconnecting the person from the outside world. This effect doesn_t come without consequence, and a small number of patients experience an unpleasant perceptual disturbance often labeled as "emergence." This may involve weird dreams and dysphoria. Higher doses produce full anesthesia.

Ketamine is the most widely used anesthetic agent in the world (with a large share of use in non-western societies), because the patient continues to breathe and maintain airway reflexes under most circumstances. This is not a "get out of jail free" card; careful attention to airway and ventilation is still mandatory. In addition, ketamine generally maintainshemodynamic stability even in the presence of mild to moderate hypovolemia, secondary to its sympathomimetic-like properties.

Traditionally, ketamine has been thought to be contraindicated in patients with head injury, primarily due to a study in the 1970s that showed it increased intracranial pressure (ICP). Recent analysis has actually refuted this assessment for the acute head-injury patient, where the mild rise in ICP is countered by an increased cerebral perfusion pressure. Ketamine also has a number of potential neuro-protective effects for severely injured brain cells and an overall benefit of improved brain tissue perfusion, which make it an ideal agent for patients with multiple injuries and associated head injury.



The Australian Way

QAS has 2,400 frontline operational paramedics, all of whom use inhaled methoxyflurane and parenteral morphine with no on-line medical control. Fire and rescue play no role in frontline patient care, apart from occasional BLS support. A smaller group of critical care paramedics have the ability to administer midazolam, in addition to narcotics, when procedural sedation is required. This combination of narcotic and benzodiazepine has been found to be suboptimalƒit either causes cardiorespiratory instability or is inadequate to establish the conditions to undertake the required procedure, despite extremely high dosages.

Although one service in Australia uses ketamine as a primary analgesic agent, most services utilize the drug as an adjunct to morphine or similar narcotic agent. This approach avoids the risk of perception disturbance in all but the most significantly injured. This also restricts the overuse of the drug by self-selection to those most significantly injured and in need of more advanced treatment.

Currently, we allow ketamine to be used in patients with complex orthopaedic injuries requiring reduction and splinting and for facilitation of complex extrication scenarios. We use doses of 0.1Ï0.2 mg/kg via titrated IV after 0.2 mg/kg of morphine. My experience in this area is that the early administration of small doses of ketamine facilitates more rapid extrication, without the risk of cardiorespiratory compromise often seen with escalating doses of narcotic and perhaps other sedatives. This year major burn injury will also be introduced as an indication to use ketamine.

Procedural Sedation

I believe the most beneficial effects occur when ketamine is used as part of a "procedural sedation" program. Our service introduced the training and concepts of procedural sedation well before the introduction

of ketamine. Initial training was centered on the use of morphine and midazolam. In the past 10 years, procedural sedation by emergency physicians with ketamine, propofol and now "ketofol" (i.e., ketamine and propofol combined) is commonplace in virtually all major emergency departments in Australia.

It_s a natural progression for the extension of such practice beyond hospital walls for carefully selected patients. Procedural sedation isn_t a process suited to all EMS agencies, especially those that rely on direct on-line medical control. This is because much of the risk assessment involves the skills and experience of the treating clinician, in this case a highly trained paramedic, and it_s often the intangibles of past experience and "gut feeling" that sway the final decision of whether to use the procedure.

Learning the pharmacology of any drug is easy, but the overall clinical management of the patient is the key. Safe procedural sedation relies on excellent training, careful patient selection, rigorous quality assurance and support from the receiving physicians. Our program has been almost unanimously supported by the statewide emergency medicine faculty.

A Note About Scene Time

Minimizing scene time for trauma and the use of procedural sedation by paramedics in poly-traumatized patients would appear incongruous. A number of jurisdictions have analyzed blunt trauma outcomes matched

for scene time. QAS found that, over a five-year period in a cohort of 23,500 trauma patients, there was no increased mortality from blunt trauma as a consequence of response times in excess of 10 minutes or scene times in excess of 20 minutes.

We need to match scene time with the clinical needs of the patient. That is, not every situation needs an express service that responds at warp speed.

The scenario of a hypotensive patient with multiple sites of injury requires accurate clinical and risk assessment, with the priorities changing to a more pragmatic approach of rapid scene extrication to definitive care. Very few blunt trauma patients require instantaneous direct transport to the operating room on arrival at the hospital; therefore, an extra 10Ï15 minutes in appropriately selected patients would seem reasonable.

Certainly, we still want to minimize total scene time when possible. All cases of major trauma are audited by the ambulance service, and inappropriate delays are managed aggressively. Blindly accepting statistically invalid key performance indicators regarding scene time is inappropriate because the issues are far more complex.

Conclusion

So far, the doses of ketamine used by QAS paramedics are at least 50% less than the amount a physician would administer. This may represent a lack of familiarity with the drug or patient complexity, but I suspect this is the result of paramedics being trained to stay within their clinical algorithms. There_s no role for cavalier behavior with procedural sedation. To date, we haven_t had any major complications, and the rate of intubations needed in the hospital has remained static, mainly due to careful patient selection.

Using ketamine as part of a procedural sedation program in the field could be a major advancement, but its use must be restricted toa select cohort of trauma patients. Introduction requires a high level of commitment to training and quality assurance, augmented by acceptance from the receiving trauma services. For agencies already committed to such programs, there_s a duty to research and publish the outcomes.JEMS

Stephen Rashford, MBBS, FACEM, is the medical director of Queensland Ambulance Service in Australia. Contact him atsrashford@emergency.qld.gov.au.




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Related Topics: Administration and Leadership, Leadership and Professionalism, Airway and Respiratory, Operations and Protcols, Pain Management, Jems Features

 

Stephen Rashford , MBBS, FACEMStephen Rashford , MBBS, FACEM, is the medical director of Queensland Ambulance Service in Australia. Contact him at srashford@emergency.qld.gov.au.

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