The correlation between ketamine and posttraumatic stress disorder in burned service members

This observational study (n=241) investigated the prevalence of PTSD with respect to perioperative low-dose ketamine use in burned soldiers undergoing surgery. Results indicate that PTSD was less prevalent amongst soldiers who were treated with ketamine, despite having larger burns, higher injury severity score, undergoing more operations, and spending more time in the ICU compared to soldiers who did not receive it as a treatment.

Abstract

“Background: Predisposing factors for posttraumatic stress disorder (PTSD) include experiencing a traumatic event, threat of injury or death, and untreated pain. Ketamine, an anesthetic, is used at low doses as part of a multimodal anesthetic regimen. However, since ketamine is associated with psychosomatic effects, there is a concern that ketamine may increase the risk of developing PTSD. This study investigated the prevalence of PTSD in Operation Iraqi Freedom/Operation Enduring Freedom (OIF/OEF) service members who were treated for burns in a military treatment center.

Methods: The PTSD Checklist-Military (PCL-M) is a 17-question screening tool for PTSD used by the military. A score of 44 or higher is a positive screen for PTSD. The charts of all OIF/OEF soldiers with burns who completed the PCL-M screening tool (2002–2007) were reviewed to determine the number of surgeries received, the anesthetic regime used, including amounts given, the total body surface area burned, and injury severity score. Morphine equivalent units were calculated using standard dosage conversion factors.

Results:  The prevalence of PTSD in patients receiving ketamine during their operation(s) was compared with patients not receiving ketamine. Of the 25,000 soldiers injured in OIF/OEF, United States Army Institute of Surgical Research received 603 burned casualties, of which 241 completed the PCL-M. Of those, 147 soldiers underwent at least one operation. Among 119 patients who received ketamine during surgery and 28 who did not; the prevalence of PTSD was 27% (32 of 119) versus 46% (13 of 28), respectively (p = 0.044).

Conclusions:  Contrary to expectations, patients receiving perioperative ketamine had a lower prevalence of PTSD than soldiers receiving no ketamine during their surgeries despite having larger burns, higher injury severity score, undergoing more operations, and spending more time in the ICU.”

Authors: Laura L. McGhee, Christopher V. Maani, Thomas H. Garza, Kathryn M. Gaylord & Ian H. Black

Summary

PTSD is a psychological disorder characterized by reliving stressful events. This study investigated the prevalence of PTSD in OIF/OEF service members who were treated for burns in our military treatment center and also investigated the potential relationship between ketamine and PTSD prevalence.

PTSD arises after a traumatic experience in which the participant is threatened with harm or death. It affects almost half of the burn patient population.

METHODS

The PTSD Checklist-Military is a screening tool for PTSD that consists of 17 questions rated on a scale of 1 to 5. A score of 44 or higher yields a diagnostic efficiency of 0.900.

The study population was US military soldiers who had sustained thermal injuries during OIF/OEF deployments. The prevalence of PTSD was examined in burn patients receiving ketamine during their operation(s) compared with those not receiving ketamine.

This study included patients who had been screened for PTSD using the PCL-M from years 2002 through 2007. The data was analyzed using the Mann-Whitney test, Spearman correlation test, and ROC analysis.

DISCUSSION

Mechanisms to predict PTSD development are not well-developed. Burn size is not a good marker for PTSD development in OIF/OEF soldiers, and PTSD prevalence in burned soldiers is similar to the prevalence found in civilian burn populations.

Ketamine is used in total intravenous anesthesia where it functions as both an analgesic and an anesthetic depending on plasma concentration. Ketamine blocks NMDA receptors and thus does not activate downstream signaling. Ketamine is used in a multimodal anesthetic regime, and is associated with dissociative, psychotic, and psychodyslectic effects similar to those associated with PTSD. However, in this study, patients receiving ketamine during operative procedures had a lower prevalence of PTSD than soldiers receiving no ketamine.

Ketamine may decrease the prevalence of PTSD in combat burned patients, and further research may help to elucidate practical perioperative approaches in decreasing the prevalence of PTSD in the combat wounded as well as the civilian population.

CONCLUSION

Ketamine use during surgery in burned soldiers seems to decrease the prevalence of PTSD.

DISCUSSION

Ketamine is widely used in low doses to control pain, but it has been linked to increases in psychosomatic and psychotic symptoms. Burn patients who received ketamine were at lower risk for screening positive for posttraumatic stress disorder than burn patients who did not receive ketamine. McGhee’s findings remind me of the movie Total Recall, where we have the scientific and technical expertise to erase someone’s memory and implant “false” memories. Ketamine might be disrupting the memories of unpleasant events associated with burn treatment and surgeries or combat experiences.

Researchers have conducted experiments with animals to disrupt memory consolidation and retrieval. They have even suggested giving pharmacologic agents as mental health prophylactics to Soldiers/Marines immediately after combat.

McGhee et al. found that it might be possible to target unpleasant memories that lead to debilitating illnesses such as PTSD and then “erase” these memories pharmacologically. However, there are ethical and moral issues surrounding “erasing” someone’s memory.

Dr. Laura McGhee (US Army Institute of Surgical Research, Fort Sam Houston, TX): We don’t know the mechanism of ketamine action on PTSD prevalence. It may be better pain control, neuronal protection, and antagonism of the NMDA receptor, or it may expose potential deleterious effects of other drugs.