Heated CO(2) with or without humidification for minimally invasive abdominal surgery

Intraoperative Patient Warming Instead of Gas on the Management of Postoperative Pain in Laparoscopic Colectomy and Cholecystectomy: A Randomized Controlled Trial

INTRODUCTION

Blurred lines remain in details of the association between patient warming with postoperative pain and a proper analgesic requirement. Therefore, the present study proposes to observe the effects of intraoperative patient warming and carbon dioxide insufflation duration in laparoscopic colectomy (LCol) and laparoscopic cholecystectomy (LChol) procedures on postoperative pain, analgesic requirements, and hemodynamics.

METHODS

The present study involved 80 cases aged 18-80 years with the American Society of Anesthesiologists I-III classification, possessing two initial groups primarily, one for LCol and one for LChol. Subsequently, each was divided into two through randomization for intraoperative warming. Postoperatively, pain perception, per se, was evaluated using the visual analog scale (VAS) score at the 30 minutes, 1st, 6th, 12th, and 24th hours, along with the impact of pain on hemodynamic parameters and side effects such as nausea/vomiting and the dosage of analgesics used.

RESULTS

Groups actively heated with warm air-blowing devices detected significantly higher intraoperative core and skin temperature measurements, and postoperative early pain perception was significantly lower in the warmed ones. Furthermore, a significant decrease in the VAS scores and the analgesic at the 12th and 24th hours compared to the first six hours was recognized between them.

CONCLUSION

Consequently, herewith, we postulate that so-called patient warming positively affects the VAS scores.

Effects of Intraoperative Insufflation With Warmed, Humidified CO2 during Abdominal Surgery: A Review

PURPOSE

During a laparotomy, the peritoneum is exposed to the cold, dry ambient air of the operating room (20°C, 0%-5% relative humidity). The aim of this review is to determine whether the use of humidified and/or warmed CO2 in the intraperitoneal environment during open or laparoscopic operations influences postoperative outcomes.

METHODS

A review was performed in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed, OVID MEDLINE, Cochrane Central Register of Controlled Trials and Embase databases were searched for articles published between 1980 and 2016 (October). Comparative studies on humans or nonhuman animals that involved randomized controlled trials (RCTs) or prospective cohort studies were included. Both laparotomy and laparoscopic studies were included. The primary outcomes identified were peritoneal inflammation, core body temperature, and postoperative pain.

RESULTS

The literature search identified 37 articles for analysis, including 30 RCTs, 7 prospective cohort studies, 23 human studies, and 14 animal studies. Four studies found that compared with warmed/humidified CO2, cold, dry CO2 resulted in significant peritoneal injury, with greater lymphocytic infiltration, higher proinflammatory cytokine levels and peritoneal adhesion formation. Seven of 15 human RCTs reported a significantly higher core body temperature in the warmed, humidified CO2 group than in the cold, dry CO2 group. Seven human RCTs found lower postoperative pain with the use of humidified, warmed CO2.

CONCLUSION

While evidence supporting the benefits of using humidified and warmed CO2 can be found in the literature, a large human RCT is required to validate these findings.

Warm and Humidified Versus Cold and Dry CO2 Pneumoperitoneum in Minimally Invasive Colon Resection: A Randomized Controlled Trial

INTRODUCTION

Peritoneal insufflation with warm-humidified (WH) CO₂ gas during minimally invasive surgical procedures is purported to prevent hypothermia and peritoneal desiccation and is associated with decreased postoperative IL-6 levels. This randomized study's purpose was to determine the clinical impact of WH versus cold-dry (CD) CO₂ in minimally invasive colon resection (MICR), and to assess perioperative plasma levels of IL-6, TIMP-1, sVEGF-R1, and HSP-70 after MICR.

METHODS

Operative and short-term clinical data plus perioperative blood samples were collected on MICR patients randomized to receive either WH (36.7°C, 95% humidity) or CD (room temperature, 0% humidity) CO₂ perioperatively. Peritoneal biopsies were taken at the start and end of surgery. Outcomes tracked included core temperature, postoperative in-hospital pain levels, analgesia requirements, and standard recovery parameters. Preoperative and postoperative days (PODs) 1 and 3 plasma protein levels were determined via ELISA.

RESULTS

A total of 101 patients were randomized to WH CO₂ (50) or CD CO₂ (51). The WH group contained more diabetics ( P = .03). There were no differences in indication, minimally invasive surgical method used, or core temperature. Pain scores were similar; however, the WH patients required less narcotics on PODs 1 to 3 ( P < .05), and less ketorolac on PODs 1 and 2 ( P < .03). No differences in length of stay, complication rates, or time to flatus/diet tolerance were noted. Plasma levels of the 4 proteins were similar postoperatively. Though insignificant, the WH group had less marked histologic changes on "end-of-case" peritoneal biopsies.

CONCLUSION

This study found significantly lower pain medication requirements for PODs 1 to 3 for the WH group; however, because there were no differences in the pains scores between the groups, firm conclusions regarding WH CO₂ cannot be made.

Warmed, humidified CO2 insufflation benefits intraoperative core temperature during laparoscopic surgery: A meta-analysis

BACKGROUND

Intraoperative hypothermia is linked to postoperative adverse events. The use of warmed, humidified CO₂ to establish pneumoperitoneum during laparoscopy has been associated with reduced incidence of intraoperative hypothermia. However, the small number and variable quality of published studies have caused uncertainty about the potential benefit of this therapy. This meta-analysis was conducted to specifically evaluate the effects of warmed, humidified CO₂ during laparoscopy.

METHODS

An electronic database search identified randomized controlled trials performed on adults who underwent laparoscopic abdominal surgery under general anesthesia with either warmed, humidified CO₂ or cold, dry CO₂ . The main outcome measure of interest was change in intraoperative core body temperature.

RESULTS

The database search identified 320 studies as potentially relevant, and of these, 13 met the inclusion criteria and were included in the analysis. During laparoscopic surgery, use of warmed, humidified CO₂ is associated with a significant increase in intraoperative core temperature (mean temperature change, 0.3°C), when compared with cold, dry CO₂ insufflation_. CONCLUSION: Warmed, humidified CO₂ insufflation during laparoscopic abdominal surgery has been demonstrated to improve intraoperative maintenance of normothermia when compared with cold, dry CO_2.

Prevention of hypothermia in patients undergoing orthotopic liver transplantation using the humigard® open surgery humidification system: a prospective randomized pilot and feasibility clinical trial

Background

Perioperative thermal disturbances during orthotopic liver transplantation (OLT) are common. We hypothesized that in patients undergoing OLT the use of a humidified high flow CO₂ warming system maintains higher intraoperative temperatures when compared to standardized multimodal strategies to maintain thermoregulatory homeostasis.

Methods

We performed a randomized pilot study in adult patients undergoing primary OLT. Participants were randomized to receive either open wound humidification with a high flow CO₂ warming system in addition to standard care (Humidification group) or to standard care alone (Control group). The primary end point was nasopharyngeal core temperature measured 5 min immediately prior to reperfusion of the donor liver (Stage 3 − 5 min). Secondary endpoints included intraoperative PaCO₂, minute ventilation and the use of vasoconstrictors.

Results

Eleven patients were randomized to each group. Both groups were similar for age, body mass index, MELD, SOFA and APACHE II scores, baseline temperature, and duration of surgery. Immediately prior to reperfusion (Stage 3 − 5 min) the mean (SD) core temperature was higher in the Humidification Group compared to the Control Group: 36.0 °C (0.13) vs. 35.4 °C (0.22), p = 0.028. Repeated measured ANOVA showed that core temperatures over time during the stages of the transplant were higher in the Humidification Group compared to the Control Group (p < 0.0001). There were no significant differences in the ETCO₂, PaCO₂, minute ventilation, or inotropic support.

Conclusion

The humidified high flow CO₂ warming system was superior to standardized multimodal strategies in maintaining normothermia in patients undergoing OLT. Use of the device was feasible and did not interfere with any aspects of surgery. A larger study is needed to investigate if the improved thermoregulation observed is associated with improved patient outcomes.

Trial registration

ACTRN12616001631493. Retrospectively registered 25 November 2016.

Cost-utility analysis of the insufflation of warmed humidified carbon dioxide during open and laparoscopic colorectal surgery

BACKGROUND

An evaluation was conducted to estimate the cost-effectiveness of insufflation of warmed humidified CO₂ during open and laparoscopic colorectal surgery compared with usual care from a UK NHS perspective.

METHODS

Decision analytic models were developed for open and laparoscopic surgery. Incremental costs per quality-adjusted life year (QALY) were estimated. The open surgery model used data on the incidence of intra-operative hypothermia and applied risks of complications for hypothermia and normothermia. The laparoscopic surgery model utilised data describing complications directly. Sensitivity analyses were conducted.

RESULTS

Compared with usual care, insufflation of warmed humidified CO₂ dominated. For open surgery, savings of £20 and incremental QALYs of 0.013 were estimated per patient. For laparoscopic surgery, savings of £345 and incremental QALYs of 0.001 per patient were estimated. Results were robust to most sensitivity analyses.

CONCLUSIONS

Considering the current evidence base, the intervention is likely to be cost-effective compared with usual care in patients undergoing colorectal surgery.

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.

Five year follow-up of a randomized controlled trial on warming and humidification of insufflation gas in laparoscopic colonic surgery--impact on small bowel obstruction and oncologic outcomes

Warming and humidification of insufflation gas has been shown to reduce adhesion formation and tumor implantation in the laboratory setting, but clinical evidence is lacking. We aimed to test the hypothesis that warming and humidification of insufflation CO2 would lead to reduced adhesion formation, and improve oncologic outcomes in laparoscopic colonic surgery. This was a 5-year follow-up of a multicenter, double-blinded, randomized, controlled trial investigating warming and humidification of insufflation gas. The study group received warmed (37°C), humidified (98%) insufflation carbon dioxide, and the control group received standard gas (19°C, 0%). All other aspects of patient care were standardized. Admissions for small bowel obstruction were recorded, as well as whether management was operative or nonoperative. Local and systemic cancer recurrence, 5-year overall survival, and cancer specific survival rates were also recorded. Eighty two patients were randomized, with 41 in each arm. Groups were well matched at baseline. There was no difference between the study and control groups in the rate of clinical small bowel obstruction (5.7% versus 0%, P 0.226); local recurrence (6.5% versus 6.1%, P 1.000); overall survival (85.7% versus 82.1%, P 0.759); or cancer-specific survival (90.3% versus 87.9%, P 1.000). Warming and humidification of insufflation CO2 in laparoscopic colonic surgery does not appear to confer a clinically significant long term benefit in terms of adhesion reduction or oncological outcomes, although a much larger randomized controlled trial (RCT) would be required to confirm this. ClinicalTrials.gov Trial identifier: NCT00642005; US National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894, USA.

Heated insufflation with or without humidification for laparoscopic abdominal surgery

BACKGROUND

Intraoperative hypothermia during both open and laparoscopic abdominal surgery may be associated with adverse events. For laparoscopic abdominal surgery, the use of heated insufflation systems for establishing pneumoperitoneum has been described to prevent hypothermia. Humidification of the insufflated gas is also possible. Past studies on heated insufflation have shown inconclusive results with regards to maintenance of core temperature and reduction of postoperative pain and recovery times.

OBJECTIVES

To determine the effect of heated gas insufflation compared to cold gas insufflation on maintaining intraoperative normothermia as well as patient outcomes following laparoscopic abdominal surgery.

SEARCH METHODS

We searched Cochrane Colorectal Cancer Specialised Register (September 2016), the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library 2016, Issue 8), Ovid MEDLINE (1950 to September 2016), Ovid Embase (1974 to September 2016), International Pharmaceutical Abstracts (IPA) (September 2016), Web of Science (1985 to September 2016), Scopus, www.clinicaltrials.gov and the National Research Register (1956 to September 2016). We also searched grey literature and cross references. Searches were limited to human studies without language restriction.

SELECTION CRITERIA

Only randomised controlled trials comparing heated (with or without humidification) with cold gas insufflation in adult and paediatric populations undergoing laparoscopic abdominal procedures were included. We assessed study quality in regards to relevance, design, sequence generation, allocation concealment, blinding, possibility of incomplete data and selective reporting. Two review authors independently selected studies for the review, with any disagreement resolved in consensus with a third co-author.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed screening of eligible studies, data extraction and methodological quality assessment of the trials. We classified a study as low-risk of bias if all of the first six main criteria indicated in the 'Risk of Bias Assessment' table were assessed as low risk. We used data sheets to collect data from eligible studies. We presented results using mean differences for continuous outcomes and relative risks for dichotomous outcomes, with 95% confidence intervals. We used Review Manager (RevMan) 5.3 software to calculate the estimated effects. We took publication bias into consideration and compiled funnel plots.

MAIN RESULTS

We included 22 studies in this updated analysis, including six new trials with 584 additional participants, resulting in a total of 1428 participants. The risk of bias was low in 11 studies, high in one study and unclear in the remaining studies, due primarily to failure to report methodology for randomisation, and allocation concealment or blinding, or both. Fourteen studies examined intraoperative core temperatures among heated and humidified insufflation cohorts and core temperatures were higher compared to cold gas insufflation (MD 0.31 °C, 95% CI, 0.09 to 0.53, I2 = 88%, P = 0.005) (low-quality evidence). If the analysis was limited to the eight studies at low risk of bias, this result became non-significant but remained heterogeneous (MD 0.18 °C, 95% CI, -0.04 to 0.39, I2= 81%, P = 0.10) (moderate-quality evidence).In comparison to the cold CO2 group, the meta-analysis of the heated, non-humidified group also showed no statistically significant difference between groups. Core temperature was statistically, significantly higher in the heated, humidified CO2 with external warming groups (MD 0.29 °C, 95% CI, 0.05 to 0.52, I2 = 84%, P = 0.02) (moderate-quality evidence). Despite the small difference in temperature of 0.31 °C with heated CO2, this is unlikely to be of clinical significance.For postoperative pain scores, there were no statistically significant differences between heated and cold CO2, either overall, or for any of the subgroups assessed. Interestingly, morphine-equivalent use was homogeneous and higher in heated, non-humidified insufflation compared to cold insufflation for postoperative day one (MD 11.93 mg, 95% CI 0.92 to 22.94, I2 = 0%, P = 0.03) (low-quality evidence) and day two (MD 9.79 mg, 95% CI 1.58 to 18.00, I2 = 0%, P = 0.02) (low-quality evidence). However, morphine use was not significantly different six hours postoperatively or in any humidified insufflation groups.There was no apparent effect on length of hospitalisation, lens fogging or length of operation with heated compared to cold gas insufflation, with or without humidification. Recovery room time was shorter in the heated cohort (MD -26.79 minutes, 95% CI -51.34 to -2.25, I2 = 95%, P = 0.03) (low-quality evidence). When the one and only unclear-risk study was removed from the analysis, the difference in recovery-room time became non-significant and the studies were statistically homogeneous (MD -1.22 minutes, 95% CI, -6.62 to 4.17, I2 = 12%, P = 0.66) (moderate-quality evidence).There were also no differences in the frequency of major adverse events that occurred in the cold or heated cohorts.These results should be interpreted with caution due to some limitations. Heterogeneity of core temperature remained significant despite subgroup analysis, likely due to variations in the study design of the individual trials, as the trials had variations in insufflation gas temperatures (35 ºC to 37 ºC), humidity ranges (88% to 100%), gas volumes and location of the temperature probes. Additionally, some of the trials lacked specific study design information making evaluation difficult.

AUTHORS' CONCLUSIONS

While heated, humidified gas leads to mildly smaller decreases in core body temperatures, clinically this does not account for improved patient outcomes, therefore, there is no clear evidence for the use of heated gas insufflation, with or without humidification, compared to cold gas insufflation in laparoscopic abdominal surgery.

Active body surface warming systems for preventing complications caused by inadvertent perioperative hypothermia in adults

BACKGROUND

Inadvertent perioperative hypothermia is a phenomenon that can occur as a result of the suppression of the central mechanisms of temperature regulation due to anaesthesia, and of prolonged exposure of large surfaces of skin to cold temperatures in operating rooms. Inadvertent perioperative hypothermia has been associated with clinical complications such as surgical site infection and wound-healing delay, increased bleeding or cardiovascular events. One of the most frequently used techniques to prevent inadvertent perioperative hypothermia is active body surface warming systems (ABSW), which generate heat mechanically (heating of air, water or gels) that is transferred to the patient via skin contact.

OBJECTIVES

To assess the effectiveness of pre- or intraoperative active body surface warming systems (ABSW), or both, to prevent perioperative complications from unintended hypothermia during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; Issue 9, 2015); MEDLINE (PubMed) (1964 to October 2015), EMBASE (Ovid) (1980 to October 2015), and CINAHL (Ovid) (1982 to October 2015).

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared an ABSW system aimed at maintaining normothermia perioperatively against a control or against any other ABSW system. Eligible studies also had to include relevant clinical outcomes other than measuring temperature alone.

DATA COLLECTION AND ANALYSIS

Several authors, by pairs, screened references and determined eligibility, extracted data, and assessed risks of bias. We resolved disagreements by discussion and consensus, with the collaboration of a third author.

MAIN RESULTS

We included 67 trials with 5438 participants that comprised 79 comparisons. Forty-five RCTs compared ABSW versus control, whereas 18 compared two different types of ABSW, and 10 compared two different techniques to administer the same type of ABSW. Forced-air warming (FAW) was by far the most studied intervention.Trials varied widely regarding whether the interventions were applied alone or in combination with other active (based on a different mechanism of heat transfer) and/or passive methods of maintaining normothermia. The type of participants and surgical interventions, as well as anaesthesia management, co-interventions and the timing of outcome measurement, also varied widely. The risk of bias of included studies was largely unclear due to limitations in the reports. Most studies were open-label, due to the nature of the intervention and the fact that temperature was usually the principal outcome. Nevertheless, given that outcome measurement could have been conducted in a blinded manner, we rated the risk of detection and performance bias as high.The comparison of ABSW versus control showed a reduction in the rate of surgical site infection (risk ratio (RR) 0.36, 95% confidence interval (CI) 0.20 to 0.66; 3 RCTs, 589 participants, low-quality evidence). Only one study at low risk of bias observed a beneficial effect with forced-air warming on major cardiovascular complications (RR 0.22, 95% CI 0.05 to 1.00; 1 RCT with 12 events, 300 participants, low-quality evidence) in people at high cardiovascular risk. We found no beneficial effect for mortality. ABSW also reduced blood loss during surgery but the magnitude of this effect seems to be irrelevant (MD -46.17 mL, 95% CI -82.74 to -9.59; I² = 78%; 20 studies, 1372 participants). The same conclusion applies to total fluids infused during surgery (MD -144.49 mL, 95% CI -221.57 to -67.40; I² = 73%; 24 studies, 1491 participants). These effects did not translate into a significant reduction in the number of participants being transfused or the average amount of blood transfused. ABSW was associated with a reduction in shivering (RR 0.39, 95% CI 0.28 to 0.54; 29 studies, 1922 participants) and in thermal comfort (standardized mean difference (SMD) 0.76, 95% CI 0.29 to 1.24; I² = 77%, 4 trials, 364 participants).For the comparison between different types of ABSW system or modes of administration of a particular type of ABSW, we found no evidence for the superiority of any system in terms of clinical outcomes, except for extending systemic warming to the preoperative period in participants undergoing major abdominal surgery (one study at low risk of bias).There were limited data on adverse effects (the most relevant being thermal burns). While some trials included a narrative report mentioning that no adverse effects were observed, the majority made no reference to it. Nothing so far suggests that ABSW involves a significant risk to patients.

AUTHORS' CONCLUSIONS

Forced-air warming seems to have a beneficial effect in terms of a lower rate of surgical site infection and complications, at least in those undergoing abdominal surgery, compared to not applying any active warming system. It also has a beneficial effect on major cardiovascular complications in people with substantial cardiovascular disease, although the evidence is limited to one study. It also improves patient's comfort, although we found high heterogeneity among trials. While the effect on blood loss is statistically significant, this difference does not translate to a significant reduction in transfusions. Again, we noted high heterogeneity among trials for this outcome. The clinical relevance of blood loss reduction is therefore questionable. The evidence for other types of ABSW is scant, although there is some evidence of a beneficial effect in the same direction on chills/shivering with electric or resistive-based heating systems. Some evidence suggests that extending systemic warming to the preoperative period could be more beneficial than limiting it only to during surgery. Nothing suggests that ABSW systems pose a significant risk to patients.The difficulty in observing a clinically-relevant beneficial effect with ABSW in outcomes other than temperature may be explained by the fact that many studies applied concomitant procedures that are routinely in place as co-interventions to prevent hypothermia, whether passive or active warming systems based in other physiological mechanisms (e.g. irrigation fluid or gas warming), as well as a stricter control of temperature in the context of the study compared with usual practice. These may have had a beneficial effect on the participants in the control group, leading to an underestimation of the net benefit of ABSW.

Warmed and humidified carbon dioxide for abdominal laparoscopic surgery: meta-analysis of the current literature

BACKGROUND

The creation of a pneumoperitoneum for laparoscopic surgery is performed by the insufflation of carbon dioxide (CO₂). The insufflated CO₂ is generally at room temperature (20-25 °C) and dry (0-5 % relative humidity). However, these physical characteristics could lead to alterations of the peritoneal cavity, leading to operative and postoperative complications. Warming and humidifying the insufflated gas has been proposed to reduce the iatrogenic effects of laparoscopic surgery, such as pain, hypothermia and peritoneal alterations. Two medical devices are currently available for laparoscopic surgery with warm and humidified CO₂.

METHODS

Clinical studies were identified by searching PubMed with keywords relating to humidified and warmed CO₂ for laparoscopic procedures. Analysis of the literature focused on postoperative pain, analgesic consumption, duration of hospital stay and convalescence, surgical techniques and hypothermia.

RESULTS

Bibliographic analyses reported 114 publications from 1977 to 2015, with only 17 publications of clinical interest. The main disciplines focused on were gynaecological and digestive surgery ). Analysis of the studies selected reported only a small beneficial effect of warmed and humidified laparoscopy compared to standard laparoscopy on immediate postoperative pain and per procedure hypothermia. No difference was observed for later postoperative shoulder pain, morphine equivalent daily doses, postoperative body core temperature, recovery room and hospital length of stay, lens fogging and procedure duration.

CONCLUSIONS

Only few beneficial effects on immediate postoperative pain and core temperature have been identified in this meta-analysis. Although more studies are probably needed to close the debate on the real impact of warmed and humidified CO₂ for laparoscopic procedures.

Warming of intravenous and irrigation fluids for preventing inadvertent perioperative hypothermia

BACKGROUND

Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs, exposure of skin for prolonged periods and receipt of large volumes of intravenous and irrigation fluids. If the temperature of these fluids is below core body temperature, they can cause significant heat loss. Warming intravenous and irrigation fluids to core body temperature or above might prevent some of this heat loss and subsequent hypothermia.

OBJECTIVES

To estimate the effectiveness of preoperative or intraoperative warming, or both, of intravenous and irrigation fluids in preventing perioperative hypothermia and its complications during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE Ovid SP (1956 to 4 February 2014), EMBASE Ovid SP (1982 to 4 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 4 February 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost (1980 to 4 February 2014) and reference lists of identified articles. We also searched the Current Controlled Trials website and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomized controlled trials or quasi-randomized controlled trials comparing fluid warming methods versus standard care or versus other warming methods used to maintain normothermia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from eligible trials and settled disputes with a third review author. We contacted study authors to ask for additional details when needed. We collected data on adverse events only if they were reported in the trials.

MAIN RESULTS

We included in this review 24 studies with a total of 1250 participants. The trials included various numbers and types of participants. Investigators used a range of methods to warm fluids to temperatures between 37°C and 41°C. We found that evidence was of moderate quality because descriptions of trial design were often unclear, resulting in high or unclear risk of bias due to inappropriate or unclear randomization and blinding procedures. These factors may have influenced results in some way. Our protocol specified the risk of hypothermia as the primary outcome; as no trials reported this, we decided to include data related to mean core temperature. The only secondary outcome reported in the trials that provided useable data was shivering. Evidence was unclear regarding the effects of fluid warming on bleeding. No data were reported on our other specified outcomes of cardiovascular complications, infection, pressure ulcers, bleeding, mortality, length of stay, unplanned intensive care admission and adverse events.Researchers found that warmed intravenous fluids kept the core temperature of study participants about half a degree warmer than that of participants given room temperature intravenous fluids at 30, 60, 90 and 120 minutes, and at the end of surgery. Warmed intravenous fluids also further reduced the risk of shivering compared with room temperature intravenous fluidsInvestigators reported no statistically significant differences in core body temperature or shivering between individuals given warmed and room temperature irrigation fluids.

AUTHORS' CONCLUSIONS

Warm intravenous fluids appear to keep patients warmer during surgery than room temperature fluids. It is unclear whether the actual differences in temperature are clinically meaningful, or if other benefits or harms are associated with the use of warmed fluids. It is also unclear if using fluid warming in addition to other warming methods confers any benefit, as a ceiling effect is likely when multiple methods of warming are used.

Insufflation with humidified and heated carbon dioxide in short-term laparoscopy: a double-blinded randomized controlled trial

Background. We tested the hypothesis that warm-humidified carbon dioxide (CO₂) insufflation would reduce postoperative pain and morphine requirement compared to cold-dry CO₂ insufflation. Methods. A double-blinded, randomized, controlled trial was conducted to compare warm, humidified CO₂ and cold-dry CO₂. Patients with benign uterine diseases were randomized to either treatment (n = 48) or control (n = 49) group during laparoscopically assisted vaginal hysterectomy. Primary endpoints of the study were rest pain, movement pain, shoulder-tip pain, and cough pain at 2, 4, 6, 24, and 48 hours postoperatively, measured by visual analogue scale. Secondary outcomes were morphine consumption, rejected boli, temperature change, recovery room stay, and length of hospital stay. Results. There were no significant differences in all baseline characteristics. Shoulder-tip pain at 6 h postoperatively was significantly reduced in the intervention group. Pain at rest, movement pain, and cough pain did not differ. Total morphine consumption and rejected boli at 24 h postoperatively were significantly higher in the control group. Temperature change, recovery room stay, and length of hospital were similar. Conclusions. Warm, humidified insufflation gas significantly reduces postoperative shoulder-tip pain as well as morphine demand. This trial is registered with Clinical Trial Registration Number   DRKS00003853 (German Clinical Trials Register (DRKS)).

Interventions for treating inadvertent postoperative hypothermia

BACKGROUND

Inadvertent postoperative hypothermia (a drop in core body temperature to below 36°C) occurs as an effect of surgery when anaesthetic drugs and exposure of the skin for long periods of time during surgery result in interference with normal temperature regulation. Once hypothermia has occurred, it is important that patients are rewarmed promptly to minimise potential complications. Several different interventions are available for rewarming patients.

OBJECTIVES

To estimate the effectiveness of treating inadvertent perioperative hypothermia through postoperative interventions to decrease heat loss and apply passive and active warming systems in adult patients who have undergone surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE (Ovid SP) (1956 to 21 February 2014), EMBASE (Ovid SP) (1982 to 21 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 21 February 2014) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL), EBSCO host (1980 to 21 February 2014), as well as reference lists of articles. We also searched www.controlled-trials.com and www.clincialtrials.gov.

SELECTION CRITERIA

Randomized controlled trials of postoperative warming interventions aiming to reverse hypothermia compared with control or with each other.

DATA COLLECTION AND ANALYSIS

Three review authors identified studies for inclusion in this review. One review author extracted data and completed risk of bias assessments; two review authors checked the details. Meta-analysis was conducted when appropriate by using standard methodological procedures as expected by The Cochrane Collaboration.

MAIN RESULTS

We included 11 trials with 699 participants. Ten trials provided data for analysis. Trials varied in the numbers and types of participants included and in the types of surgery performed. Most trials were at high or unclear risk of bias because of inappropriate or unclear randomization procedures, and because blinding of assessors and participants generally was not possible. This may have influenced results, but it is unclear how the results may have been influenced. Active warming was found to reduce the mean time taken to achieve normothermia by about 30 minutes in comparison with use of warmed cotton blankets (mean difference (MD) -32.13 minutes, 95% confidence interval (CI) -42.55 to -21.71; moderate-quality evidence), but no significant difference in shivering was noted. Active warming was found to reduce mean time taken to achieve normothermia by almost an hour and a half in comparison with use of unwarmed cotton blankets (MD -88.86 minutes, 95% CI -123.49 to -54.23; moderate-quality evidence), and people in the active warming group were less likely to shiver than those in the unwarmed cotton blanket group (Relative Risk=0.61 95% CI= 0.42 to 0.86; low quality evidence). There was no effect on mean temperature difference in degrees celsius at 60 minutes (MD=0.18°C, 95% CI=-0.10 to 0.46; moderate quality evidence), and no data were available in relation to major cardiovascular complications. Forced air warming was found to reduce time taken to achieve normothermia by about one hour in comparison to circulating hot water devices (MD=-54.21 minutes 95% CI= -94.95, -13.47). There was no statistically significant difference between thermal insulation and cotton blankets on mean time to achieve normothermia (MD =-0.29 minutes, 95% CI=-25.47 to 24.89; moderate quality evidence) or shivering (Relative Risk=1.36 95% CI= 0.69 to 2.67; moderate quality evidence), and no data were available for mean temperature difference or major cardiovascular complications. Insufficient evidence was available about other comparisons, adverse effects or any other secondary outcomes.

AUTHORS' CONCLUSIONS

Active warming, particularly forced air warming, appears to offer a clinically important reduction in mean time taken to achieve normothermia (normal body temperature between 36°C and 37.5°C) in patients with postoperative hypothermia. However, high-quality evidence on other important clinical outcomes is lacking; therefore it is unclear whether active warming offers other benefits and harms. High-quality evidence on other warming methods is also lacking; therefore it is unclear whether other rewarming methods are effective in reversing postoperative hypothermia.

Thermal insulation for preventing inadvertent perioperative hypothermia

BACKGROUND

Inadvertent perioperative hypothermia occurs because of interference with normal temperature regulation by anaesthetic drugs and exposure of skin for prolonged periods. A number of different interventions have been proposed to maintain body temperature by reducing heat loss. Thermal insulation, such as extra layers of insulating material or reflective blankets, should reduce heat loss through convection and radiation and potentially help avoid hypothermia.

OBJECTIVES

To assess the effects of pre- or intraoperative thermal insulation, or both, in preventing perioperative hypothermia and its complications during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 2), MEDLINE, OvidSP (1956 to 4 February 2014), EMBASE, OvidSP (1982 to 4 February 2014), ISI Web of Science (1950 to 4 February 2014), and CINAHL, EBSCOhost (1980 to 4 February 2014), and reference lists of articles. We also searched Current Controlled Trials and ClinicalTrials.gov.

SELECTION CRITERIA

Randomized controlled trials of thermal insulation compared to standard care or other interventions aiming to maintain normothermia.

DATA COLLECTION AND ANALYSIS

Two authors extracted data and assessed risk of bias for each included study, with a third author checking details. We contacted some authors to ask for additional details. We only collected adverse events if reported in the trials.

MAIN RESULTS

We included 22 trials, with 16 trials providing data for some analyses. The trials varied widely in the type of patients and operations, the timing and measurement of temperature, and particularly in the types of co-interventions used. The risk of bias was largely unclear, but with a high risk of performance bias in most studies and a low risk of attrition bias. The largest comparison of extra insulation versus standard care had five trials with 353 patients at the end of surgery and showed a weighted mean difference (WMD) of 0.12 ºC (95% CI -0.07 to 0.31; low quality evidence). Comparing extra insulation with forced air warming at the end of surgery gave a WMD of -0.67 ºC (95% CI -0.95 to -0.39; very low quality evidence) indicating a higher temperature with forced air warming. Major cardiovascular outcomes were not reported and so were not analysed. There were no clear effects on bleeding, shivering or length of stay in post-anaesthetic care for either comparison. No other adverse effects were reported.

AUTHORS' CONCLUSIONS

There is no clear benefit of extra thermal insulation compared with standard care. Forced air warming does seem to maintain core temperature better than extra thermal insulation, by between 0.5 ºC and 1 ºC, but the clinical importance of this difference is unclear.

Gases for establishing pneumoperitoneum during laparoscopic abdominal surgery

BACKGROUND

Laparoscopic surgery is now widely performed to treat various abdominal diseases. Currently, carbon dioxide is the most frequently used gas for insufflation of the abdominal cavity (pneumoperitoneum). Many other gases have been introduced as alternatives to carbon dioxide for establishing pneumoperitoneum.

OBJECTIVES

To assess the safety, benefits, and harms of different gases for establishing pneumoperitoneum in patients undergoing laparoscopic abdominal surgery.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and Chinese Biomedical Literature Database (CBM) until September 2012.

SELECTION CRITERIA

We only included randomized controlled trials comparing different gases for establishing pneumoperitoneum in patients undergoing laparoscopic abdominal surgery under general anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors identified the trials for inclusion, collected the data, and assessed the risk of bias independently. We performed the meta-analyses using Review Manager 5. We calculated the risk ratio (RR) for dichotomous outcomes and the mean difference (MD) or standardized mean difference (SMD) for continuous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

Carbon dioxide pneumoperitoneum versus nitrous oxide pneumoperitoneum Three trials randomized 196 participants (the majority with low anaesthetic risk) to carbon dioxide pneumoperitoneum (n =96) or nitrous oxide pneumoperitoneum (n =100). All of the trials were of high risk of bias. Two trials (n=143) showed lower pain scores in nitrous oxide pneumoperitoneum at various time points on the first post-operative day. One trial (n=53) showed no difference in the pain scores between the groups. There were no significant differences in cardiopulmonary complications, surgical morbidity, or cardiopulmonary changes between the groups. There were no serious adverse events related to either carbon dioxide or nitrous oxide pneumoperitoneum. Carbon dioxide pneumoperitoneum versus helium pneumoperitoneum Four trials randomized 144 participants (the majority with low anaesthetic risk) to carbon dioxide pneumoperitoneum (n =75) or helium pneumoperitoneum (n =69). All of the trials were of high risk of bias. Fewer cardiopulmonary changes were observed with helium pneumoperitoneum than carbon dioxide pneumoperitoneum. There were no significant differences in cardiopulmonary complications, surgical morbidity, or pain scores. There were three serious adverse events (subcutaneous emphysema) related to helium pneumoperitoneum. Carbon dioxide pneumoperitoneum versus any other gas pneumoperitoneum There were no randomized controlled trials comparing carbon dioxide pneumoperitoneum to any other gas pneumoperitoneum.

AUTHORS' CONCLUSIONS

1. Nitrous oxide pneumoperitoneum during laparoscopic abdominal surgery appears to decrease post-operative pain in patients with low anaesthetic risk.2. Helium pneumoperitoneum decreases the cardiopulmonary changes associated with laparoscopic abdominal surgery. However, this did not translate into any clinical benefit over carbon dioxide pneumoperitoneum in patients with low anaesthetic risk.3. The safety of nitrous oxide and helium pneumoperitoneum has yet to be established. More randomized controlled trials on this topic are needed. Future trials should include more patients with high anaesthetic risk. Furthermore, such trials need to use adequate methods to reduce the risk of bias.

Guidelines for perioperative care in elective colonic surgery: Enhanced Recovery After Surgery (ERAS®) Society recommendations

BACKGROUND

This review aims to present a consensus for optimal perioperative care in colonic surgery and to provide graded recommendations for items for an evidenced-based enhanced perioperative protocol.

METHODS

Studies were selected with particular attention paid to meta-analyses, randomised controlled trials and large prospective cohorts. For each item of the perioperative treatment pathway, available English-language literature was examined, reviewed and graded. A consensus recommendation was reached after critical appraisal of the literature by the group.

RESULTS

For most of the protocol items, recommendations are based on good-quality trials or meta-analyses of good-quality trials (quality of evidence and recommendations according to the GRADE system).

CONCLUSIONS

Based on the evidence available for each item of the multimodal perioperative-care pathway, the Enhanced Recovery After Surgery (ERAS) Society, International Association for Surgical Metabolism and Nutrition (IASMEN) and European Society for Clinical Nutrition and Metabolism (ESPEN) present a comprehensive evidence-based consensus review of perioperative care for colonic surgery.

Benchtop evaluation of pressure barrier insufflator and standard insufflator systems

BACKGROUND

Previous experimental research has reported minimal differences in pressure maintenance between different versions of standard insufflators (SI). However, a recent report identified potential clinical benefits with a valveless pressure barrier insufflator (PBI). We sought to perform a benchtop objective evaluation of SI and PBI systems.

METHODS

A rigid box system with continuous pressure manometry was used to evaluate a PBI (Surgiquest Airseal) and two SIs (SI1 = Stryker PneumoSure High Flow Insufflator and SI2 = Storz SCB Thermoflator). Pressure maintenance of 15 mmHg was evaluated during experimental conditions of leakage from a 5 mm port site, leakage from a 12 mm port site, and continuous suction.

RESULTS

With leakage from the 5 mm port site, the PBI maintained pressure of >13 mmHg whereas the pressures dropped moderately with the SI1 (7-13 mmHg) and SI2 insufflators (3-7 mmHg) and did not regain goal pressure until leakage was stopped. With leakage from 12 mm port site, the PBI pressure decreased to 9-11 mmHg, whereas the SI1 and SI2 lost insufflation pressures completely. The PBI maintained pressure of >11 mmHg during continuous suction while the SI1 and SI2 lost pressure entirely, and actually showed negative pressure from air suction into the rigid box system. When evaluated statistically with the mixed model repeated measures ANOVA, the SI1 and SI2 performed similarly while the PBI maintained increased pressure.

CONCLUSIONS

In the experimental rigid box system, the PBI more successfully maintained pressure in response to leakage and suction than SIs.