Using a retrospective review of records, we will conduct a multivariate analysis to examine the relationship between exposure to ketamine, as an analgesic agent in combat related trauma care, the use of additional opioid pain medications, and patient reported pain levels.

This is a retrospective study to determine if there is a relationship between intravenous infusion of ketamine given for analgesia and the use of additional opioid pain medications and patient reported pain levels before and during ketamine usage. The investigator anticipates that records of up to 700 subjects will be reviewed for eligibility. The time period 24 hours before the initial ketamine therapy is initiated along with 24 & 48 hours after the start of ketamine therapy will be the time periods examined. The average/minimum/maximum pain scores during these time periods will be used. Medication usage will be calculated over the 24 hour time periods.

This protocol is presented as an initial step in exploring the possible relationship between the administration of ketamine as an analgesic agent, the potential reduction in pain medications, and the potential reduction of pain levels. With this the goals/objectives are as follows:

Objectives

1. To compare morphine consumption in battlefield injured patients with acute pain 24 hours before the initiation of a ketamine infusion to the subsequent 48 hours following the start of infusion.
2. To compare average/minimum/maximum pain scores in battlefield injured patients with acute pain 24 hours before the initiation of a ketamine infusion to the subsequent 48 hours following the start of infusion.
3. To describe the pain trajectory in battlefield injured patients with acute pain after the initiation of ketamine infusions.
4. To measure the absolute and proportional incidence of ketamine associated side effects in battlefield injured patients with acute pain following the initiation of ketamine infusions.

Inclusion Criteria:

• Battlefield injured from January 2007 to December 2013
• Prescribed a ketamine infusion for acute pain
• Awake, alert (non intubated/sedated), and able to report pain scores 24 hours prior to the start of infusion and up to 48 hours following infusion

Exclusion Criteria:

• Patients who did not receive an injury in theater and did not receive ketamine while being treated by the APS or WRNMMC/WRAMC hospital staff
• No continuous perineural catheter or epidural placement while on ketamine infusion
• Less than 18 years old

Male and female military health care beneficiaries age 18 years and older