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 postoperative pain.
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 is 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.
Conclusions:
In patients experiencing opioid-resistant severe postoperative pain, the magnesium, lidocaine, and ketorolac
combination may be an effective non opioid 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.