Thoracotomy for lung tumor or for minimally invasive direct coronary artery bypass (MIDCAB) surgery, may be associated with debilitating pain. Ketamine was shown to enhance opioid antinociception and prevent opioid resistance. We hypothesize that ketamine given with morphine would lower morphine consumption and narcotic related side effects after thoracotomy and provide superior analgesia to morphine given alone.

We planned a prospective, randomomized, double blind study of 2 pain management protocols in consecutive patients undergoing thoracotomy for MIDCAB or lung tumor resection over a 6 month period. After patients emerged from a standardized general anesthetic and when objectively awake and complaining of pain >5/10 on a visual analogue pain scale, they were connected to an intravenous patient controlled analgesia regimen. The regimen was assigned randomly to be either morphine alone (1.5 mg per dose, lockout interval of 7 minutes) or morphine plus ketamine (1.0 mg morphine plus 5 mg ketamine per dose, same lockout interval). Rescue diclofenac was available to both groups. Follow-up lasted 4 hours.

We planned to monitor and compare pain scores, wakefulness scores, hemodynamic and respiratory parameters as well as total morphine consumption and incidence of side effects and complications. All monitoring and recording was done by blinded nurses and intensive care physicians.

Inclusion Criteria:

• Consecutive patients scheduled for elective minimally invasive direct coronary artery bypass (MIDCAB) or for lung resection via anterolateral thoracotomy during a 6-month period (Sep 2001-March 2002)

Exclusion Criteria:

Exclusion criteria were:

• American Society of Anesthesiologists (ASA) physical class ≥3, Emergency operations,
• Q-wave myocardial infarct occurring during the previous 3 weeks, or poor left ventricular function (e.g., ejection fraction [EF] <30% by echocardiography or angiography).

Other exclusion criteria were:

• A body mass index >35 kg/m2,
• Past or current neuropathy or psychological disturbances,
• The use of centrally active drugs,
• Chronic liver or renal failure requiring dialysis,
• A FEV1/FVC <70%,
• Allergy to ketamine, morphine or non steroidal anti inflammatory drugs (NSAIDs),
• Clotting abnormalities,
• A platelets count <70000/mm3,
• A white blood count <3000>14000/mm3,
• Uncontrolled diabetes mellitus or fasting blood glucose >250 g/dl,
• Evidence of sepsis or infection up to one week prior to randomization.