IV Ketamine – Pain Rescue For Refractory Pain Flareups

Not a Pain Meeting Goes By Without someone extolling the virtues of IV Ketamine in refractory patients. Its use has been thwarted by preceived side effects. Now it appears these fears have been over-rated.  Here are some protocols I have encountered .

IV Ketamine – Effective Treatment for Refractory Pain in and Outpatient Clinic
John Krusz et al
IASP Poster PM 378 Montreal 2010

• 174 cases – 450 infusions
• Included:
  CRPS (n=37)
  TN (n=30)
  lumbar/cervical nerve root pain (n=99)
  post-herpetic neuralgia (n=3)
  abdominal visceral pain including interstitial cystitis (n= 5)
•  I.V. ketamine dosage was begun at 0.35 mg/kg. = 25 mg for 70 kg – This is more than suggested by colleagueDr. H. Pollett – Medical Director at Pollett Pain Management – He finds some pain patients can be overly sensitive and starts at 10 mg first time.
• “Some patients received up to 4 infusions on a daily basis” – no reaction to one, another one tacked on the same day, of increased dose and over same period.
• After gauging tolerance, 0.3-0.4 mg/kg was given over 90 minutes
• “If there were no side effects, another 0.6 mg/kg was administered over the same time”
• 3rd and 4th doses if OK and still symptoms – dose/time same as second
• Average dose of I.V. ketamine was 115 mg per infusion = 1.4 mg/kg for an 80 kg person – average time 2.8 hours  – sounds like many had 2 doses.
• Some people give IV midazolam pre-ketamine to ward off any dysphoria and hallucinations. They gave either midazolam( I presume about 0.5 mg IV) or IV metochlopramide (I presume 10 mg) for agitation or nausea in only 9% of cases.
• 141/174 developed transient spaciness; No hallucinations or dysphoria.
• pulse oximetry monitoring –  and careful nursing care – I presume the meant someone to watch them…
• “96% of patients treated (n=167) had a better than 50% decrease in pain scores, with 51% (n=85) reporting abolition of pain after 1 or more infusions”

How long did it last?- Never did catch the author at the poster but a combination of ketamine and lidocaine has been promoted by Dr. Eileen Thompson from Ottawa – she would get 4 weeks relief and shames others for using dangerous NSAIDS instead to a simple once monthly infusion.

Comment – They used alot more than what  Dr. Stanley J. Antolak, (Centre for Urologic and Pelvic Pain, Lake Elmo, MN, USA )used in resistent pudental neuralgia – he would give (if I recall correctly from Canadian Pain Society meeting Calgary 2010) 20 mg over 20 minutes and was pleaased with those results…

Anyone had any experience with it?