Can Ketamine Cause SVT?

                     We review all uses of Ketamine under our medical control, with any doses over 10mg.  Recently I reviewed a case of Ketamine used for severe combative encephalopathy which included kicking punching and attacking everyone near this patient.  The squad was using Ketamine at 250mg IM to control this situation.   The patient was successfully sedated.  However shortly after the use of medication the patient went into spontaneous paroxysmal SVT at 170 BPM.  The squad recognized the event and gave 6mg of Adenosine with only a brief response.  They then administered 12mg IV and again only a transient response was noted.  On arrival at the ED the 12 lead was still showing narrow complex tachycardia with no obvious P-waves.  After 15 minutes in the ED, the patient spontaneously converted to sinus rhythm.  The medic called me inquiring if Ketamine can induce SVT? 

                     This was an excellent question, especially since the time of administration and the onset of SVT seemed to correlate.  I did a literature search and was utilizing this month’s Up To Date review of arrythmias with anesthesia.  The article reviewed Etomidate, Propofol, and Ketamine.  The article seemed to focus on pre-existing EKG abnormalities and structural heart defects as the higher risks for arrhythmic events with these agents.  Specifically, baring stimulant agents of abuse, Ketamine may cause mild to moderate sinus tachycardia but not SVT.  It seems that SVT requires accessory tracts that move physiologically down the same path, orthodromic or moving opposite the normal electrical path antidromic.  Deciding which is which requires an electrophysiologist so I simply report this as using antiarrhythmics like Amiodarone, Calcium Channel Blockers or even Beta Blockers can be very dangerous in the orthodromic patient and degenerate into a fatal rhythm.  Adenocard in these situations is usually very safe, and the squad made an excellent decision to try this.  If the patient was unstable, as in shock, then synchronized cardioversion would be very appropriate.

                     To answer the original question, after searching and reviewing the possibility of SVT induced using Ketamine the answer is simply, no.  I would continue to use this drug under the safe uses of our protocol.  We have safe uses for Ketamine depending on the route and dose.  The simple 10mg, maximum total of 3 dose, not to exceed 30mg IV is a very safe effective non-narcotic analgesic.   Doses of 1mg/kg IV minimum of 100mg given IV for chemical assisted intubation or as part of the RSI protocol requires extensive monitoring to include, capnography, pox, monitor, glucose frequent vitals and airway management.  The same monitoring and extensive ongoing evaluation is required for behavioral dangerous emergencies.  Events occurred and as this squad from Madison in Ashland County did so well, they simply safely treated the patient and provided outstanding care!  Well, done Madison Fire.  As always, our EMS Medical Directors look forward to all your inquiries as we partner with all of you to provide excellent pre-hospital care.

Sincerely,

Don Spaner MD