Background: Severe postoperative pain is principally managed by opioids. While effective,
opioids do not provide adequate relief in many patients and cause many side effects, including
antinociceptive tolerance and opioid-induced hyperalgesia. To evaluate if a combination of intravenous
Magnesium, Lidocaine, Ketorolac (MLK cocktail) is a useful rescue therapy through synergistic
pharmacological mechanisms for acute pain relief. We present the intravenous combination of
magnesium, lidocaine, and ketorolac (MLK cocktail) as a possible rescue for opioid insensitive severe
Materials and Methods: The principal settings were the post-operative care unit (PACU) and the
surgical ward. We retrospectively analyzed the electronic medical record and anesthesia documents
of 14 patients experiencing severe postoperative pain, >7/10 visual-analogue pain score (VAS), despite
receiving at least 8 mg of intravenous morphine milligram equivalents (MME) after arrival in
the LAC+USC Medical Center PACU between September 2012 and January 2013. The data reviewed
included patients’ demographics, disease etiology, surgical procedure, opioids received perioperatively,
and visual-analogue pain scores before and after each analgesic received, and after
the MLK cocktail. The a priori primary outcome and a posteriori secondary outcome of this study
are mean visual-analogue pain score and morphine milligram equivalent dose administered per
hour, respectively. The main tool evaluated has been VAS score.
Results: In patients who failed to respond to opioid analgesics, administration of the MLK cocktail
improved the VAS pain scores immediately from 9.4 ± 1.0 to 3.6 ± 3.5. The MLK cocktail also decreased
the MME doses/hour in the immediate 12 hours postoperative period from 12.4 ± 5.6 to
1.1 ± 0.9.
Conclusion: In patients experiencing opioid-resistant severe postoperative pain, the magnesium,
lidocaine, and ketorolac combination may be an effective nonopioid rescue therapy. Additionally,
magnesium, lidocaine, and ketorolac may be utilized in cases complicated by either antinociceptive
tolerance or opioid-induced hyperalgesia and can restore opioid responsiveness.