To systematically evaluate the clinical effect of indirect calorimetry (IC)-guided nutritional support therapy in critically ill patients.

Electronic databases CNKI, Wanfang data, VIP, PubMed, Embase, Springer, Ovid, CINAHL and the Cochrane Library were searched using the following key words: indirect calorimetry, resting energy measurement, metabolic car, resting energy expenditure, predictive equations, prediction formula, energy delivery, nutritional support therapy, and Harris-Benedict. All databases were published from January 2002 to August 2022. The experimental group was guided by the IC method, and the control group was guided by the PE method. We used the Cochrane risk-of-bias tool to assess the quality of the included studies. The main outcome indicators were the 90-day mortality, 180-day mortality, mechanical ventilation time, intensive care unit(ICU)stays, total length of hospital stays, and infection incidence of critically ill patients admitted to the ICU. The secondary outcome indicators were average energy delivery levels and protein delivery levels. The literature search was conducted independently by 2 researchers using standardized methods. Meta-analysis was performed using RevMan 5.4.

A total of 931 patients were enrolled in 7 RCTs, including 468 patients in the IC group and 463 patients in the PE group. The summary results showed that compared with the PE group, the 90-day mortality rate (RR=0.77, 95%CI=0.60 to 0.98, P=0.03)of the IC group patients was significantly lower, and the 180-day mortality rate had no significant change(RR=0.95, 95%CI=0.71 to 1.27, P=0.73), which did not shorten the mechanical ventilation time (MD=0.87, 95%CI=-0.81 to 2.56, P=0.31), and ICU hospital stays(MD=-0.46, 95%CI=-2.84 to 1.92, P=0.70) and total length of hospital stays(MD=0.23, 95%CI=-3.27 to 3.72, P=0.90), and the incidence of infection did not decrease(MD=1.18, 95%CI=0.73 to 1.91, P=0.51). The average energy delivery in the IC group was significantly higher than that in the PE group (MD=619.91, 95%CI=407.81 to 832.02, P<0.01) and the protein delivery level was also significantly higher than that in the PE group(MD=14.13, 95%CI=2.45 to 25.61, P=0.02).

This meta-analysis indicates that IC-guided energy delivery reduces 90-day mortality and increases mean daily energy intake and protein intake in critically ill patients; mechanical ventilation time, ICU stays, and total length of stays are not prolonged; it has no significant effect on infection incidence and 180-day mortality. This finding encourages the use of IC-guided energy delivery during critical nutrition support. But more high-quality studies are still needed to confirm these findings.