Effect of amino acid infusion on body temperature during anaesthesia

Perioperative Amino Acid Infusion for Preventing Hypothermia and Improving Clinical Outcomes During Surgery Under General Anesthesia: A Systematic Review and Meta-analysis

Amino acid (AA) infusion is sometimes selected to avoid hypothermia during general anesthesia. However, the widespread clinical use of AA infusion therapy has not been established. This study aimed to clarify the evidence that AA infusion can increase patient body temperature and improve clinical outcomes using the Grading of Recommendations Assessment, Development, and Evaluation system. We searched MEDLINE (PubMed), Cochrane Central Register of Controlled Trials, and Igaku Chuo Zasshi (Japana Centra Revuo Medicina) in November 2015. Studies were reviewed by 2 independent assessors to identify randomized controlled trials (RCTs) involving AA infusion compared with placebos during surgery under general or combined general/epidural anesthesia. Study quality was assessed using the Grading of Recommendations Assessment, Development, and Evaluation system and the Cochrane methodology. The primary outcome was difference in body temperature before and after perioperative AA infusion. Shivering frequency, blood loss volume, postoperative intubation time, and hospitalization period were also assessed as clinical outcomes. We analyzed the outcome data using a random effect model. From 298 screened titles, 14 RCTs met our inclusion criteria, including 626 patients (327 in AA and 299 in placebo groups). In 626 participants from 14 RCTs, AA infusion increased body temperature by a mean difference (MD) of 0.46°C (95% confidence interval [CI], 0.31-0.62, low-quality evidence). Regarding other outcomes, AA infusion decreased shivering frequency by a risk ratio of 0.34 (95% CI, 0.12-0.94; 7 RCTs, 248 participants, very low-quality evidence), shortened postoperative intubation time by MD of -125 minutes (95% CI, -210 to -38.8; 2 RCTs, 158 participants, moderate-quality evidence), and shortened the hospitalization period by MD of -1.81 days (95% CI, -2.07 to -1.55; 3 RCTs, 230 participants, low-quality evidence) compared with placebo. There was no significant difference in the volume of blood loss between the 2 groups (standardized MD, -0.20, 95% CI, -0.44 to 0.04; low-quality evidence). There was no publication bias. AA infusion in the perioperative period increased patient body temperature and improved clinical outcomes compared with placebo. However, the evidence to support the use of AA infusion is limited, and further large-scale RCTs are required.

Intravenous nutrients for preventing inadvertent perioperative hypothermia in adults

BACKGROUND

Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because normal temperature regulation is disrupted during surgery, mainly because of the effects of anaesthetic drugs and exposure of the skin for prolonged periods. Many different ways of maintaining body temperature have been proposed, one of which involves administration of intravenous nutrients during the perioperative period that may reduce heat loss by increasing metabolism, thereby increasing heat production.

OBJECTIVES

To assess the effectiveness of preoperative or intraoperative intravenous nutrients in preventing perioperative hypothermia and its complications during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; November 2015) in the Cochrane Library; MEDLINE, Ovid SP (1956 to November 2015); Embase, Ovid SP (1982 to November 2015); the Institute for Scientific Information (ISI) Web of Science (1950 to November 2015); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCO host; 1980 to November 2015), as well as the reference lists of identified articles. We also searched the Current Controlled Trials website and ClincalTrials.gov.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of intravenous nutrients compared with control or other interventions given to maintain normothermia in adults undergoing surgery.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data and assessed risk of bias for each included trial, and a third review author checked details if necessary. We contacted some study authors to request additional information.

MAIN RESULTS

We included 14 trials (n = 565), 13 (n = 525) of which compared intravenous administration of amino acids to a control (usually saline solution or Ringer's lactate). The remaining trial (n = 40) compared intravenous administration of fructose versus a control. We noted much variation in these trials, which used different types of surgery, variable durations of surgery, and different types of participants. Most trials were at high or unclear risk of bias owing to inappropriate or unclear randomization methods, and to unclear participant and assessor blinding. This may have influenced results, but it is unclear how results might have been influenced.No trials reported any of our prespecified primary outcomes, which were risk of hypothermia and major cardiovascular events. Therefore, we decided to analyse data related to core body temperature instead as a primary outcome. It was not possible to conduct meta-analysis of data related to amino acid infusion for the 60-minute and 120-minute time points, as we observed significant statistical heterogeneity in the results. Some trials showed that higher temperatures were associated with amino acids, but not all trials reported statistically significant results, and some trials reported the opposite result, where the amino acid group had a lower core temperature than the control group. It was possible to conduct meta-analysis for six studies (n = 249) that provided data relating to the end of surgery. Amino acids led to a statistically significant increase in core temperature in comparison to those receiving control (MD = 0.46°C 95% CI 0.33 to 0.59; I2 0.0%; random-effects; moderate quality evidence).Three trials (n = 155) reported shivering as an outcome. Meta-analysis did not show a clear effect, and so it is uncertain whether amino acids reduce the risk of shivering (RR 0.36, 95% CI 0.13 to 1.00; I2 = 93%; random-effects model; very low-quality evidence).

AUTHORS' CONCLUSIONS

Intravenous amino acids may keep participants up to a half-degree C warmer than the control. This difference was statistically significant at the end of surgery, but not at other time points. However, the clinical importance of this finding remains unclear. It is also unclear whether amino acids have any effect on the risk of shivering and if intravenous nutrients confer any other benefits or harms, as high-quality data about these outcomes are lacking.

The effects of amino acid infusions on core body temperature during the perioperative period: a systematic review

The aim of this systematic review was to determine the effect of amino acid infusions on core body temperature and shivering. We searched the PubMed, EMBASE, CINAHL, and Cochrane Register of Controlled Trials databases to identify randomized controlled trials that met the inclusion criteria. A total of 11 eligible trials involving 506 participants were identified. Amino acid infusions were associated with shorter periods of mechanical ventilation and hospitalization and less perioperative shivering, mechanical intubation, and hospitalization in surgical patients without hepatic, renal, or severe metabolic disorders. It is recommended that infusions are warmed before administration to avoid further decrease in core body temperature.