Case report of ketamine sedation during aeromedical retrieval

Case report

By Dr Adam Pritchard and Dr Minh Le Cong

A 32yo man with a history of illicit drug use, was brought in by police to a remote hospital in far northAustralia at 5pm. He was displaying signs of acute delirium, severe agitation, attempted self-harm, paranoid delusion and violent behaviors towards police and hospital staff.  He was placed under the State Mental Health Act. He was physically restrained and given IM sedation of 5mg Midazolam and 5mg Diazepam, and once an IV was placed, further sedation was required, consisting of 20mg IV Diazepam and 5mg IV Haloperidol.  The patient was referred to the regional referral hospital for psychiatric assessment and the process of retrieval was initiated through the central coordinating agency.

After about 1 hour, ongoing agitation and violent behaviors, a bolus of IV ketamine was given followed by a ketamine infusion.  Adequate sedation was achieved with a rapid titration up to 100mg/hr of ketamine.  Accepting the limits of sedation, neurological examination was normal as were results of available blood tests.  Blood alcohol was 30mmol/L equivalent to BAC 0.138.

The patient remained in the remote hospital, with close monitoring and under Ketamine sedation overnight.  Retrieval was initiated the next morning and first contact by the retrieval team with the patient was made at midday.  By this time, the patient had received 100mg/hr of ketamine for 15hrs, 200mg/hr of Ketamine for 1 hour plus intermittent boluses of ketamine and diazepam, as required.

On examination prior to loading, the patient remained agitated to a Richmond agitation Sedation Score (RASS) of +2.  He had a GCS of 10 (E3V2M5) with vital signs within normal limits apart from a mild tachycardia (110).  On one occasion he sat up, pulled of his Hudson mask, coughed and spat.

The regional referral hospital is 800km away via a short helicopter flight and a 2 hour fixed wing flight. Due to the remoteness of the hospital, it was necessary to retrieve the patient by the regions fixed-wing aeromedical service, the Royal Flying Doctor Service.

Prior to takeoff, the patient received 2x50mg boluses of Ketamine around the time of taxi and takeoff and the Ketamine infusion was increased to 500mg/hr with a view to decreasing it once stabilized in flight.  The effect on the patient was limited.

In flight, he continued to display agitation to a RASS +1 to +2. A bolus of 10mg IV Droperidol was administered with little effect.  Adequate sedation of RASS -1 to -2 was achieved with titrated bolus of Midazolam to a total of 12mg.

The ketamine infusion was 500mg/hr for the 3 hour flight and transfer to hospital.  This is in addition to the 15 hours of Ketamine at 100mg/hr, 200mg/hr for 1 hr and boluses doses.  A total of 3335mg of Ketamine was administered over 19 hrs.

Apart from a mild tachycardia, there appeared to be no complications or unwanted side effects of this level of administration.  Airway reflexes were retained as was demonstrated by the patient sitting up and coughing.

The patient was observed in the regional hospital emergency department overnight and was assessed by the psychiatry service the next morning.  He was promptly discharged with a diagnosis of alcohol intoxication.

We believe that this is the largest recorded dose and duration of Ketamine sedation used in an aeromedical retrieval from a remote hospital.  It demonstrates the effectiveness and safety profile of Ketamine when used for this purpose.

Discussion

Psychiatric presentations of acute psychosis and delirium to remote hospitals create a broad range of difficult management issues.  Inadequate staffing, unsuitable facilities and unavailability of security or police mean that the reliance on chemical restraint is more of a necessity compared to larger hospitals.  Remote practitioners’ skill and familiarity with intravenous sedation and airway protection is variable.

The legislative requirements of psychiatric specialist assessment mean that movement of these patients to regional centers is commonly undertaken and with increasing remoteness comes longer duration in the remote hospital and increasing reliance on aeromedical retrieval.

The aeromedical environment can be particularly confronting for those suffering delirium or psychosis.  Factors such as noise, vibration, turbulence and the necessary restraints for aviation and medical requirements can precipitate or worsen severe anxiety and agitation.  Flight medical crew need to be restrained themselves for takeoff and landing so are generally unable to interact with the patient for some minutes.  As such, the patient needs to be adequately sedated to allow smooth transition from the ground to the air and allow the safe transportation for the duration of the flight.

As a choice of sedative in this situation, Ketamine has many advantages.  It causes sedation, amnesia and analgesia and avoids respiratory depression and maintains airway reflexes and cardiovascular tone.   It has a wide safety profile and as such, has been used extensively in prehospital environments.

The reported contraindication to using Ketamine in psychosis has been challenged(1).

This case demonstrates the safety and effectiveness of large doses of Ketamine for extended periods in patients requiring emergency sedation. We believe it should be considered as an adjunct to the current pharmacological techniques used in this scenario in the prehospital, aeromedical and remote environments.

References

1.      M Le Cong, B Gynther, E Hunter, P Schuller. Ketamine sedation for patients with acute agitation and psychiatric illness requiring aeromedical retrieval. Emerg Med J.2012, 29:335-337.

Note: This case report has been peer reviewed and published in Air Medical journal here.

We are able to publish this  free text version of the article under author copyright with Elsevier. We do so in the spirit of FOAMEd and to encourage our prehospital and aeromedical colleagues to do more research into this area of patient care.