1. No significant difference between patients who underwent the intervention and patients who underwent the sham intervention in death, MI, stroke, or acute renal failure could be identified.
2. The study draws strength from its double-blind design. However, subgroup analyses did not indicate and significant outcomes either.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Ischemic injury to the vital organs and reperfusion injury are predictable risks of cardiac surgery. A technique known as Remote Ischemic Preconditioning (RIPC) has been postulated to enhance the ability of end organs to tolerate prolonged ischemia and minimize reperfusion injury. This study examined this theory.
This was a double-blinded study and the participants were recruited from patients scheduled for elective cardiac surgery that would require cardiopulmonary bypass under general anesthesia with IV propofol. The study group underwent four cycles of 5 minute upper limb ischemia (BP cuff inflated to ≥200 mmHg), whereas the sham group had the intervention performed on a dummy arm. There was no significant difference between patients who underwent the intervention and patients who underwent the sham intervention in regards to number of death, MI, stroke, or acute renal failure. Secondary clinical outcomes such as troponin and creatinine release, duration of mechanical ventilation, length of hospital or ICU stay, new onset atrial fibrillation, and incidence of postoperative delirium also did not differ significantly.
This is one of only a few studies of RIPC where clinical outcomes were used as primary endpoints. The large, randomized sample size was important in identifying whether this simple intervention would convey a benefit to cardiac surgery outcomes.
Relevant Reading: The therapeutic potential of ischemic conditioning: an update
In-Depth [ randomized controlled trial]: In this prospective, multicenter, double-blind, randomized control trial, 1403 patients that were scheduled to undergo elective cardiac surgery requiring cardiopulmonary bypass under total anesthesia with IV propofol were randomized into an RIPC group (n=692) and a sham-RIPC group (n=693). This study’s RIPC method consisted of inflating the BP cuff to ≥200 mmHg (at least 15 mmHg higher than the patient’s systolic arterial pressure) for five minutes followed by five minutes of cuff deflation for a total of four cycles of upper limb ischemia.
There was no significant between-group differences in death (1.3% in the RIPC group vs. 0.6% in the sham group, p = 0.21), myocardial infarction (6.8% in the RIPC group vs. 9.1% in the sham group, p = 0.12), stroke (2.0% in the RIPC group vs. 2.2% in the sham group, p = 0.79), acute renal failure (6.1% vs. 5.1%, p = 0.45) or the composite of these (p = 0.89) up to the time of hospital discharge (maximum of 14 days). Kaplan-Meier estimates of event-free survival in the RIPC group and the sham-RIPC group were 85.2% and 85.0%, respectively, at 90 days after surgery.
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