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Pharmacologically Dosed Oral Glutamine Reduces Myocardial Injury in Patients Undergoing Cardiac Surgery: A Randomized Pilot Feasibility Trial
Study Question: Is the administration of pharmacologically dosed preoperative oral glutamine (GLN) safe and feasible as an option to attenuate myocardial injury in cardiac surgery patients?
Study Description: This study was designed as a randomized pilot feasibility study at U.S. hospitals to determine if the use of pharmacologically dosed GLN was both safe and feasible to administer. Study inclusion criteria included undergoing elective cardiac surgery (CABG, valvular surgery, or pulmonary vein repair) in which cardiopulmonary bypass (CPB) was utilized. Notable study exclusion criteria included patients with preexisting kidney or liver dysfunction, history of HIV, hepatitis B or C or ongoing signs of myocardial ischemia. Subjects were randomized to either GLN or maltodextrin control (CONT) taken at home starting 3 days prior to surgery. GLN was dosed at 25 grams orally twice daily, with a final dose 2 hours prior to induction of anesthesia. Patients in the CONT group received a corresponding dose of maltodextrin. Patient compliance was assessed using daily reminder calls from the study nurse and required empty package returns. Investigators and clinical caregivers were blinded to study assignment. Myocardial injury markers (Troponin I and CKMB), plasma glutamine and heat shock protein (HSP) levels were assessed at baseline (time of consent), 6, 24, 48 and 72-hours postoperatively. Blood was also collected for HSP and plasma glutamine levels prior to anesthesia.
Results: A total of 14 patients met study inclusion criteria and were enrolled. Four patients were not included in the analysis (3 withdrawn consent [GLN] and 1 intraoperative death [CONT]) leaving a total of ten patients included in the study analysis (GLN-4, CONT-6). Plasma troponin I levels peaked in both groups 6-hours postoperatively. Patients in the GLN group had significantly decreased troponin I levels at 24, 48 and 72-hours postoperatively, compared to patients in the control group. The GLN group also had decreased CK-MB levels at 24 and 48-hours. There were no differences noted in HSP levels throughout the study period. Plasma glutamine levels were similar between the 2 groups prior to anesthesia. Additionally, both groups demonstrated a statistically significant decrease in plasma glutamine levels postoperatively compared to prior to anesthesia.
Conclusion(s): The use of GLN is both feasible and safe when given in pharmacologic doses to preoperative cardiac surgery patients. These data support the need for a larger, definitive, randomized controlled trial of GLN therapy to reduce myocardial injury and improve clinical outcome in cardiac surgery.
Perspective: The use of pharmacologically dosed GLN preoperatively in cardiac surgery appears to be safe and feasible, perhaps paving the way for larger, randomized studies. While not designed to deliver definitive answers on the topic, the study did offer insight about the potential benefits of a pharmacologically dosed regimen of GLN in cardiac surgery patients.