Peri-operative warming devices: performance and clinical application

Incidence of Unintentional Intraoperative Hypothermia and Its Risk Factors in Oral and Maxillofacial Surgery: A Prospective Study

PURPOSE

Unintentional intraoperative hypothermia is a common complication in patients who undergo open surgery, increasing the risk of adverse outcomes. However, few studies have focused on intraoperative hypothermia during oral and maxillofacial surgery. Our study aimed to analyze the prevalence and risk factors of hypothermia in patients who underwent oral and maxillofacial surgery.

DESIGN

A prospective cohort study was conducted on 128 patients who underwent oral and maxillofacial surgery.

METHODS

This prospective study was conducted at West China Hospital of Stomatology between December 2020 and May 2021, and each patient was followed for at least 1-month postoperatively. Patients who underwent oral and maxillofacial surgery under general anesthesia, with at least 1-month follow-up were analyzed. The primary variable was intraoperative hypothermia, defined as core body temperature less than 36°C, measured using a tympanic thermometer during the surgery. We performed univariate and multivariate logistic regression analyses to identify the risk factors of unintentional intraoperative hypothermia.

FINDINGS

The mean age of the 128 patients was 31.0 ± 20.9 years, and there was a male predominance (53.1%), with male to female ratio of 1.13:1. Thirty-one patients (24.2%) developed hypothermia intraoperatively. Older age (OR = 1.068, 95% CI: 1.028-1.110, P = .001), lower weight (OR = 0.878, 95% CI: 0.807-0.955, P = .002), greater blood loss (OR = 1.003, 95% CI: 1.000-1.006, P = .034), and undergoing cancer surgery (OR = 0.210, 95% CI: 0.067-0.656, P = .007) were associated with intraoperative hypothermia.

CONCLUSIONS

Unintentional intraoperative hypothermia is common in patients who undergo surgery for oral cancer. Warming interventions to prevent intraoperative hypothermia for high-risk patients (older, lower weight, or more intraoperative bleeding) should be considered. Meanwhile, with careful nursing and rehabilitation instructions, intraoperative hypothermia does not lead to serious perioperative complications.

Comparative Efficacy of Six Active Warming Systems for Intraoperative Warming in Adult Patients Undergoing Laparoscopic Surgery: A Systematic Review and Network Meta-Analysis

Intraoperative hypothermia is very common and harmful in adult patients undergoing laparoscopic surgery. A variety of active warming systems has received close attention and has been researched by related scholars. However, the relative efficacy of these systems and which active warming system is preferred for such patients remain unclear. The aim of this study was to compare and rank six active warming systems regarding intraoperative warming efficacy in adult patients undergoing laparoscopic surgery. Following the PRISMA 2020 guidelines, relevant randomized controlled trials (RCTs) on the efficacy of different active warming systems in warming adult patients undergoing laparoscopic surgery were searched from five English databases and three Chinese databases. The quality of the studies was assessed using the Cochrane Risk of Bias tool (RoB2). The outcome was the final intraoperative core temperature. We estimated direct effects by using pairwise meta-analysis, estimated relative effects and ranking with the consistency model to conduct an NetworkMeta-Analysis (NMA). We used GRADE (Grading of Recommendations Assessment, Development, and Evaluation) to assess the certainty of the evidence. Sensitivity analysis was performed to test the robustness of the results. This study is registered with PROSPERO, with number CRD42022309057. In total, 19 RCTs involving 6 active warming systems and comprising 1364 patients were included in this NMA. The NMA once again confirmed the validity of forced-air warming (FAW) systems compared with other active warming systems, and further showed that underbody FAW was associated with more remarkable warming efficacy in different types of FAW systems. NMA was used to perform an exhaustive comparison of the warming efficacy of six active warming systems and indicated that underbody FAW was most likely to be the most effective warming system in adult patients undergoing laparoscopic surgery; however, considering the sparsity of the network, our results should be cautiously interpreted. Furthermore, a large number of high-quality RCTs comparing the warming efficacy of different competitive active warming systems are needed.

Bleeding, Hemorrhagic Shock, and the Global Blood Supply

Hemorrhage is responsible for at least 40% of deaths after trauma and 27% of maternal deaths worldwide. Patients with hemorrhagic shock require attentive critical care and transfusion of blood products. Access to a safe and affordable blood supply is critical to providing safe surgical care. Traumatic injury, obstetric hemorrhage, and upper gastrointestinal bleed are the main causes of severe bleeding requiring transfusion. This article discusses the presentation and management of these causes across the world and provides a brief overview of the current challenges in maintaining a global blood supply.

Bioheat Transfer Basis of Human Thermoregulation: Principles and Applications

Thermoregulation is a process that is essential to the maintenance of life for all warm-blooded mammalian and avian species. It sustains a constant core body temperature in the face of a wide array of environmental thermal conditions and intensity of physical activities that generate internal heat. A primary component of thermoregulatory function is the movement of heat between the body core and the surface via the circulation of blood. The peripheral vasculature acts as a forced convection heat exchanger between blood and local peripheral tissues throughout the body enabling heat to be convected to the skin surface where is may be transferred to and from the environment via conduction, convection, radiation, and/or evaporation of water as local conditions dictate. Humans have evolved a particular vascular structure in glabrous (hairless) skin that is especially well suited for heat exchange. These vessels are called arteriovenous anastomoses (AVAs) and can vasodilate to large diameters and accommodate high flow rates. We report herein a new technology based on a physiological principle that enables simple and safe access to the thermoregulatory control system to allow manipulation of thermoregulatory function. The technology operates by applying a small amount of heating local to control tissue on the body surface overlying the cerebral spine that upregulates AVA perfusion. Under this action, heat exchangers can be applied to glabrous skin, preferably on the palms and soles, to alter the temperature of elevated blood flow prior to its return to the core. Therapeutic and prophylactic applications are discussed.

Development and Validation of a Questionnaire of the Perioperative Nursing Competencies in Patient Safety

(1) Background: This research presents the CUCEQS© (Spanish acronym for Questionnaire of Perioperative Nursing Safety Competencies), which evaluates the perception of perioperative nurses about their competencies related to surgical patient safety. The aim of the present study was to design, validate, and analyze the psychometric properties of the CUCEQS©. (2) Methods: We devised an instrumental, quantitative, and descriptive study divided into two phases: in the first, the questionnaire was designed through a Delphi method developed by perioperative nurses and experts in patient safety. In the second, the reliability, validity, and internal structure of the tool were evaluated. (3) Results: In the first phase, the items kept were those that obtained a mean equal to or higher than four out of five in the expert consensus, and a Content Validity Index higher than 0.78. In the second phase, at the global level, a Stratified Cronbach's Alpha of 0.992 was obtained, and for each competency, Cronbach's Alpha values between 0.81 and 0.97 were found. A first-order confirmatory factor analysis of the 17 subscales (RMSEA 0.028, (IC 90% = 0.026-0.029) and its observed measures was performed for the 164 items, as well as a second-order analysis of the four competencies (RMSEA = 0.034, (IC90% = 0.033-0.035). (4) Conclusions: The questionnaire is a valid tool for measuring the perceived level of competency by the perioperative nurses in surgical patient safety. This is the first questionnaire developed for this purpose, and the results obtained will facilitate the identification of areas to be improved by health professionals in patient safety.

Impact of parylene coating on heating performance of intravenous fluid warmer: a bench study

BACKGROUND

Perioperative hypothermia is a common occurrence, particularly with the elderly and pediatric age groups. Hypothermia is associated with an increased risk of perioperative complications. One method of preventing hypothermia is warming the infused fluids given during surgery. The enFlow™ intravenous fluid warmer has recently been reintroduced with a parylene coating on its heating blocks. In this paper, we evaluated the impact of the parylene coating on the new enFlow's fluid warming capacity.

METHODS

Six coated and six uncoated enFlow cartridges were used. A solution of 10% propylene glycol and 90% distilled H2O was infused into each heating cartridge at flow rates of 2, 10, 50, 150, and 200 ml/min. The infused fluid temperature was set at 4 °C, 20 °C, and 37 °C. Output temperature was recorded at each level. Data for analysis was derived from 18 runs at each flow rate (six cartridges at three temperatures).

RESULTS

The parylene coated fluid warming cartridge delivered very stable output of 40 °C temperatures at flow rates of 2, 10, and 50 ml/min regardless of the temperature of the infusate. At higher flow rates, the cartridges were not able to achieve the target temperature with the colder fluid. Both cartridges performed with similar efficacy across all flow rates at all temperatures.

CONCLUSIONS

At low flow rates, the parylene coated enFlow cartridges was comparable to the original uncoated cartridges. At higher flow rates, the coated and uncoated cartridges were not able to achieve the target temperature. The parylene coating on the aluminum heating blocks of the new enFlow intravenous fluid warmer does not negatively affect its performance compared to the uncoated model.

A comparison of the warming capabilities of two Baragwanath rewarming appliances with the Hotline fluid warming device

Background

Accidental intraoperative hypothermia is a common and avoidable adverse event of the perioperative period and is associated with detrimental effects on multiple organ systems and postoperative patient outcomes. In a resource-limited environment, prevention of intraoperative hypothermia is often challenging. Resourceful clinicians overcome these challenges through creative devices and frugal innovations.

Objectives

To investigate the thermal performance of two Baragwanath Rewarming Appliances (BaRA) against that of the Hotline device to describe an optimal setup for these devices.

Methods

This was a quasi-experimental laboratory study that measured the thermal performance of two BaRA devices and the Hotline device under a number of scenarios. Independent variables including fluid type, flow rate, warming temperature and warming transit distance were sequentially altered and temperatures measured along the fluid stream. Change in temperature (ΔT) was calculated as the difference between entry and exit temperature for each combination of variables for each warming device.

Results

A total of 219 experiments were performed. At a temperature of 43.0°C and a transit distance of 200 cm, the BaRA A configuration either matched or exceeded the ΔT of the Hotline over all fluid type and flowrate combinations. The BaRA B configuration does not provide comparable thermal performance to the Hotline. Measured flowrates were noticeably slower than manufacturer-quoted values for all intravenous (IV) cannulae used.

Conclusion

A warm-water bath at 43.0°C with 200 cm of submerged IV tubing provides thermal performance comparable to the Hotline device, with all fluid type and flowrate combinations.

Contributions of the study

The present study provides an evidence-based method for warming intravenous fluid in resource-limited scenarios.

Resistant fabric warming is a viable alternative to forced-air warming to prevent inadvertent perioperative hypothermia during hemiarthroplasty in the elderly

BACKGROUND

Surgical site infection (SSI) is associated with inadvertent perioperative hypothermia (IPH). This can be prevented by active patient warming. However, results from comparisons of warming techniques are conflicting. They are based mostly on elective surgery, are from small numbers of patients, and are dominated by the market leader, forced-air warming (FAW). Furthermore, the definition of hypothermia is debatable and systematic reviews of warming systems conclude that a stricter control of temperature is required to study the benefits of warming.

AIM

To analyse core temperatures in detail in a large subset of elderly patients who took part in a randomized trial of patient warming following hemiarthroplasty who had received constant zero-flux thermometry to record their temperature.

METHODS

Regression models with a fixed effect for warming group and covariates related to temperature were compared for 257 participants randomized to FAW or resistant fabric warming (RFW) from a prior clinical trial.

FINDINGS

Those in the RFW group were -0.08°C cooler and had a cumulative hypothermia score -1.87 lower than those in the FAW group. There was no difference in the proportion of hypothermic patients at either <36.5°C or <36.0°C.

CONCLUSIONS

This is the first study to provide accurate temperature measurements in patients undergoing a procedure predominantly under regional rather than general anaesthetic. It shows that RFW is a viable alternative to FAW for preventing IPH during hemiarthroplasty. Further studies are needed to measure the benefits of patient warming in terms of clinically important outcomes.

Warming of blood and intravenous fluids using low-power infra-red light-emitting diodes

Non-contact warming of blood and intravenous (IV) fluids with temperature drop compensation is an unmet clinical need till now, for management of hypothermia in patients with urgent requirement of blood. Currently available technologies provide wet warming or dry warming with direct contact using hot water or with a hot plate, respectively. These conventional technologies need disposable cartridges to be used in conjunction with the warmer. The warmed fluids lose their temperature when passing through long IV lines and fails in its purpose at low flow rates. In this paper, a distributed non-contact warming method is introduced using infra-red radiations. The method incorporates a bag warming unit and an inline cartridge unit. Bag warming unit provides uniform distribution of infra-red thermal energy liberated from low cost infra-red light emitting diodes (IR LEDs) in horizontal and vertical planes of the fluid carrying bag. An inline cartridge, through which the IV line passes, reduces the drop in temperature just before the transfusion site using a cluster of IR LEDs. As per the In Vitro tests are carried out in to establish the safety and efficacy, the bag warming unit steadily rises the temperature to attain the cut off value with a temperature rise coefficient of 0.7 °C/min and the inline cartridge warms the fluid within 10 min at a thermal transfer rate of more than 1.5 °C/min. The fluid temperature is uniformly distributed within a narrow range of 36-38 °C. When the inline warmer is powered on, the drop-in temperature is reduced to zero for flow up to 5 ml/min. For flow rates more than 8 ml/min, the temperature drop is reduced more than half. For massive transfusion range, the temperature of the fluid remains within 38.5 ± 1.2 °C for flow rates in the range of 100-1500 ml/min.

Bioinspired Microstructured Materials for Optical and Thermal Regulation

Precise optical and thermal regulatory systems are found in nature, specifically in the microstructures on organisms' surfaces. In fact, the interaction between light and matter through these microstructures is of great significance to the evolution and survival of organisms. Furthermore, the optical regulation by these biological microstructures is engineered owing to natural selection. Herein, the role that microstructures play in enhancing optical performance or creating new optical properties in nature is summarized, with a focus on the regulation mechanisms of the solar and infrared spectra emanating from the microstructures and their role in the field of thermal radiation. The causes of the unique optical phenomena are discussed, focusing on prevailing characteristics such as high absorption, high transmission, adjustable reflection, adjustable absorption, and dynamic infrared radiative design. On this basis, the comprehensive control performance of light and heat integrated by this bioinspired microstructure is introduced in detail and a solution strategy for the development of low-energy, environmentally friendly, intelligent thermal control instruments is discussed. In order to develop such an instrument, a microstructural design foundation is provided.

Forced-Air Convection Versus Underbody Conduction Warming Strategies to Maintain Perioperative Normothermia in Patients Undergoing Total Joint Arthroplasty

Background

Forced-air warming is an established strategy for maintaining perioperative normothermia. However, this warming strategy can potentially contaminate the surgical field by circulating nonsterile air. This study aimed to determine whether changing practice away from this method resulted in non-inferior rates of perioperative hypothermia.

Methods

We performed a chart review of primary total hip and knee arthroplasty patients from 2014 to 2017, when the strategy of intraoperative forced-air warming (FAW) was changed to preoperative FAW along with intraoperative underbody conduction warming (CW) with an underbody warming mattress. Data included patient temperatures throughout all phases of care, blood loss and transfusion requirements, length of postanesthesia care unit (PACU) and hospital stays, and 30-day infection and mortality.

Results

A total of 769 charts were reviewed; 349 patients underwent surgery before the practice change and 420 after. Mean (SD; 95% CI) body temperatures at the time of incision were lower for group 1 than for group 2 (34.55 vs 35.52 °C [0.97 °C; 95% CI, 0.72-1.23 °C]). The average nadir of intraoperative body temperature was lower for group 1 than for group 2 (difference of means, 0.44 °C; 95% CI, 0.18-0.71 °C). Group 2 had a higher percentage of patients who presented hypothermic (temperature <36.0 °C) on arrival in the PACU (12.9% vs 7.7%).

Conclusion

Preoperative convective warming combined with intraoperative underbody conductive warming maintains normothermia during primary total joint arthroplasty and is non-inferior to forced-air intraoperative warming alone.

Perioperative nurses' experiences in relation to surgical patient safety: A qualitative study

Surgical patient safety remains a concern worldwide as, despite World Health Organization recommendations and implementation of its Surgical Safety Checklist, adverse events continue to occur. The aim of this qualitative study was to explore the views and experiences of perioperative nurses regarding the factors that impact surgical patient safety. Data were collected through five focus groups involving a total of 50 perioperative nurses recruited from four public hospitals in Spain. Content analysis of the focus groups yielded four main themes: personal qualities of the perioperative nurse, the surgical environment, safety culture, and perioperative nursing care plans. One of the main findings concerned barriers to the exercise of leadership by nurses, especially regarding completion of the Surgical Safety Checklist. Some of the key factors that impacted the ability of perioperative nurses to fulfil their duties and ensure patient safety were the stress associated with working in the operating room, time pressures, and ineffective communication in the multidisciplinary team. Targeting these aspects through training initiatives could contribute to the professional development of perioperative nurses and reduce the incidence of adverse events by enhancing the surgical safety culture.

Effect of Perioperative Active Body Surface Warming Systems on Analgesic and Clinical Outcomes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Inadvertent perioperative hypothermia is a common complication of surgery, and active body surface warming (ABSW) systems are used to prevent adverse clinical outcomes. Prior data on certain outcomes are equivocal (ie, blood loss) or limited (ie, pain and opioid consumption). The objective of this study was to provide an updated review on the effect of ABSW on clinical outcomes and temperature maintenance.

METHODS

We conducted a systematic review of randomized controlled trials evaluating ABSW systems compared to nonactive warming controls in noncardiac surgeries. Outcomes studied included postoperative pain scores and opioid consumption (primary outcomes) and other perioperative clinical variables such as temperature changes, blood loss, and wound infection (secondary outcomes). We searched Ovid MEDLINE daily, Ovid MEDLINE, EMBASE, CINHAL, Cochrane CENTRAL, and Web of Science from inception to June 2019. Quality of evidence (QoE) was rated according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Subgroup analysis sought to determine the effect of preoperative + intraoperative warming versus intraoperative warming alone. Metaregression evaluated the effect of year of publication, use of neuromuscular blockers, anesthesia, and surgery type on outcomes.

RESULTS

Fifty-four articles (3976 patients) were included. Pooled results demonstrated that ABSW maintained normothermia compared to controls, during surgery (30 minutes postinduction [mean difference {MD}: 0.3°C, 95% confidence interval {CI}, 0.2-0.4, moderate QoE]), end of surgery (MD: 1.1°C, 95% CI, 0.9-1.3, high QoE), and up to 4 hours postoperatively (MD: 0.3°C, 95% CI, 0.2-0.5, high QoE). ABSW was not associated with difference in pain scores (<24 hours postoperatively, moderate to low QoE) or perioperative opioid consumption (very low QoE). ABSW increased patient satisfaction (MD: 2.2 points, 95% CI, 0.9-3.6, moderate QoE), reduced blood transfusions (odds ratio [OR] = 0.6, 95% CI, 0.4-1.0, moderate QoE), shivering (OR = 0.2, 95% CI, 0.1-0.4, high QoE), and wound infections (OR = 0.3, 95% CI, 0.2-0.7, high QoE). No significant differences were found for fluid administration (low QoE), blood loss (very low QoE), major adverse cardiovascular events (very low QoE), or mortality (very low QoE). Subgroup analysis and metaregression suggested increased temperature benefit with pre + intraoperative warming, use of neuromuscular blockers, and recent publication year. ABSW seemed to confer less temperature benefit in cesarean deliveries and neurosurgical/spinal cases compared to abdominal surgeries.

CONCLUSIONS

ABSW is effective in maintaining physiological normothermia, decreasing wound infections, shivering, blood transfusions, and increasing patient satisfaction but does not appear to affect postoperative pain and opioid use.

Effect of warming and infusion of red blood cell concentrates on markers of haemolysis: An ex vivo simulation study

BACKGROUND

Transfusion of red blood cell (RBC) concentrates is a common procedure to restore blood volume and tissue oxygen delivery in patients with trauma. Although RBC warmers may prevent hypothermia, some warming or infusion equipment may lead to haemolysis and patient injury.

OBJECTIVES

The aim of this study was to test the effect of (i) RBC warming and (ii) administration via manual vs. pump infusion on haemolysis.

METHODS

This experimental ex vivo study studied haemolysis markers of RBC injury. The sample consisted of 90 RBC infusions in two simulations, randomly, 45 warmed RBC infusions and 45 nonwarmed RBC infusions, in two or three stages: before the intervention (baseline-warming, N= 45; nonwarming, N= 45), after water bath warming at 42 °C (warmed, N= 45), and then after the warmed or nonwarmed RBCs were infused by manual or pump infusion at a rate of 100 mL/h (infusion-warming, N= 45; nonwarming, N= 45).

RESULTS

Warmed RBCs showed significantly lower total haemoglobin (Hb) and haematocrit levels and increase in free Hb levels, haemolysis levels, and lactate dehydrogenase (LDH) activity (all p<0.05) than baseline RBCs. Pump infusion RBCs were associated with reduced total Hb and increased free Hb, haemolysis, and potassium (K) levels (all p<0.05) compared with warmed RBCs. In contrast, manual infusion of warmed RBCs resulted in significantly reduced total Hb levels and increased LDH activity (both <0.05). After infusion, total Hb, free Hb, haematocrit, haemolysis, and LDH values were significantly different for warmed vs. nonwarmed RBCs (p<0.05).

CONCLUSIONS

Haemolysis biomarkers increase with RBC warming and infusion, especially when using infusion pumps. Critically ill patients should be carefully monitored for possible complications during and after RBC infusion.

Effectiveness of application of carbon-fibre polymer-fabric resistive heating compared with forced-air warming to prevent unintentional intraoperative hypothermia in patients undergoing elective abdominal operations: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Unintentional intraoperative hypothermia was regarded as a common intraoperative symptom with serious complications. The active warming strategies of forced-air warming (FAW) and carbon-fibre polymer-fabric resistive heating were considered to be effective interventions for preventing hypothermia. However, the effectiveness of them was not reported consistently.

AIM

To evaluate the effectiveness of carbon-fibre polymer-fabric resistive heating compared with FAW in preventing hypothermia in patients undergoing elective surgeries.

DESIGN

Systematic review and meta-analysis.

METHODS

A rigorous systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis reporting checklist. Searching strategy was undertaken on the electronic databases of Cumulative Index to Nursing and Allied Health Literature, MEDLINE, PubMed, EMBASE and Medical Literature Retrieval Service. The assessment of study quality was performed through risk of bias of Cochrane handbook of systematic review of interventions. Data synthesis was conducted through meta-analysis with sensitive analysis. The quality of evidence was graded using Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS

A total of five randomised controlled trials with 282 patients undergoing elective surgeries were included in the quantitative synthesis. Four studies concluded that FAW was as effective as carbon-fibre polymer-fabric resistive heating in preventing hypothermia. However, one study yielded a different conclusion that the efficacy of FAW was superior to carbon-fibre polymer-fabric resistive heating with small incidence of hypothermia. Meta-analysis found that FAW was more effective than carbon-fibre polymer-fabric resistive heating in preventing hypothermia.

CONCLUSIONS

In the elective abdominal surgery, carbon-fibre polymer-fabric resistive heating was less effective than FAW on the prevention of hypothermia. However, hypothermia still occurred in the FAW group. It was more objective to assess the efficacy of warming technology combining the incidence of hypothermia and the core body temperature together, which was suggested for further research.

Nurse Anesthetists' and Operating Theater Nurses' Experiences with Inadvertent Hypothermia in Clinical Perioperative Nursing Care

PURPOSE

To deepen the understanding of and describe nurse anesthetists' and operating theater nurses' experiences with inadvertent hypothermia in clinical perioperative nursing care.

DESIGN

Qualitative, explorative, and descriptive study that carries an inductive nature.

METHODS

Focus group interviews with 16 nurse anesthetists and operating theater nurses from four hospitals in Norway. Gadamer's hermeneutics has guided the study's interpretation.

FINDINGS

Taking the temperature and measures against inadvertent hypothermia perioperatively are not always systematically implemented. In the data material, three thematic units emerged: routines and habits, the culture of the perioperative unit, and silent suffering.

CONCLUSIONS

Complications caused by inadvertent hypothermia in surgical patients can lead to unnecessary suffering and prolong the hospital stay. The surgical team's cooperation and responsibility are linked to routine nursing interventions. These depend on the nurses' knowledge and experience as well as their clinical and subjective assessment of the patient's physical condition and the surgical techniques used.

Thermophysiological Comfort of Surgeons and Patient in an Operating Room Based on PMV-PPD and PHS Indexes

There are different actors in an operating room (OR), who have controversial requirements for the indoor thermal environment. While the patient is at risk of perioperative hypothermia, the surgeons are in a state of thermophysiological discomfort. The study presents an analysis of the thermophysiological comfort of both patient and surgeons in an OR. Surgical clothing ensembles with three values of clothing insulation are simulated. Different indoor environment conditions (air temperature and relative humidity) are tested. The analysis is based on the calculation of predicted mean vote and predicted percentage of dissatisfied (PMV-PPD) indexes and assessment of the climatic conditions categories. Discussion of the predicted heat strain is also presented. The simulated results and their analysis show considerable discrepancies between the thermophysiological comfort of the patient and the surgeons, even when dressed in a light protective ensemble, in the same indoor environment.

Reducing Implant Infection in Orthopaedics (RIIiO): Results of a pilot study comparing the influence of forced air and resistive fabric warming technologies on postoperative infections following orthopaedic implant surgery

BACKGROUND

Active warming during surgery prevents perioperative hypothermia but the effectiveness and postoperative infection rates may differ between warming technologies.

AIM

To establish the recruitment and data management strategies needed for a full trial comparing postoperative infection rates associated with forced air warming (FAW) versus resistive fabric warming (RFW) in patients aged >65 years undergoing hemiarthroplasty following fractured neck of femur.

METHODS

Participants were randomized 1:1 in permuted blocks to FAW or RFW. Hypothermia was defined as a temperature of <36°C at the end of surgery. Primary outcomes were the number of participants recruited and the number with definitive deep surgical site infections.

FINDINGS

A total of 515 participants were randomized at six sites over a period of 18 months. Follow-up was completed for 70.1%. Thirty-seven participants were hypothermic (7.5% in the FAW group; 9.7% in the RFW group). The mean temperatures before anaesthesia and at the end of surgery were similar. For the primary clinical outcome, there were four deep surgical site infections in the FAW group and three in the RFW group. All participants who developed a postoperative infection had antibiotic prophylaxis, a cemented prosthesis, and were operated under laminar airflow; none was hypothermic. There were no serious adverse events related to warming.

CONCLUSION

Surgical site infections were identified in both groups. Progression from the pilot to the full trial is possible but will need to take account of the high attrition rate.

Comparison of the EasyWarm® self-heating blanket with the Cocoon forced-air warming blanket in preventing intraoperative hypothermia

The importance of preventing hypothermia in the perioperative period cannot be overemphasised. The use of active warming devices is advocated and practised widely. The forced-air warming (FAW) blanket is currently a popular modality. The BARRIER® EasyWarm® (Mölnlycke Healthcare, Belrose, Australia) self-heating blanket, which does not require a power unit, has been proposed as an easy-to-use alternative to the FAW blanket. We conducted a single-centre, randomized controlled trial to compare the efficacy of the EasyWarm® self-heating blanket to the Cocoon blanket (Care Essentials, North Geelong, Australia), a conventional FAW blanket, in preventing intraoperative hypothermia. Forty patients undergoing elective surgery under general anaesthesia lasting >1 h were randomized in a 1:1 ratio. Prewarming was not allowed; 39 patients were analysed (19 EasyWarm® group and 20 Cocoon blanket group). There was no statistically significant difference between the two groups with regard to the mean (±standard deviation) final nasopharyngeal temperature (35.89 ± 0.82 °C versus 35.74 ± 0.77 °C; P = 0.72 in the Cocoon and EasyWarm® blanket groups, respectively). Similarly, the difference between average temperatures at 1, 2 and 3 h was not statistically significant. We found the EasyWarm® blanket to be as effective as the Cocoon FAW blanket in preventing intraoperative hypothermia. Due to its ease of use, the EasyWarm® blanket may have an additional benefit in preoperative warming of patients.

A dynamic thermoregulatory material inspired by squid skin

Effective thermal management is critical for the operation of many modern technologies, such as electronic circuits, smart clothing, and building environment control systems. By leveraging the static infrared-reflecting design of the space blanket and drawing inspiration from the dynamic color-changing ability of squid skin, we have developed a composite material with tunable thermoregulatory properties. Our material demonstrates an on/off switching ratio of ~25 for the transmittance, regulates a heat flux of ~36 W/m² with an estimated mechanical power input of ~3 W/m², and features a dynamic environmental setpoint temperature window of ~8 °C. Moreover, the composite can manage one fourth of the metabolic heat flux expected for a sedentary individual and can also modulate localized changes in a wearer's body temperature by nearly 10-fold. Due to such functionality and associated figures of merit, our material may substantially reduce building energy consumption upon widespread deployment and adoption.

Randomized clinical study comparing active heating methods for prevention of intraoperative hypothermia in gastroenterology

OBJECTIVE

to compare the efficacy of three active heating methods in the prevention of intraoperative hypothermia in open gastroenterological surgeries.

METHOD

randomized clinical trial with a sample of 75 patients, whose initial body temperature measured by a tympanic thermometer. Esophageal temperature <36ºC was considered hypothermic. Patients were divided into three groups using: thermal mattress, underbody forced-air warming blanket and heated infusion system. The tympanic and esophageal temperatures were measured at different times of the intraoperative period, but the temperature considered gold standard was the esophageal. To evaluate the homogeneity of the groups, we used chi-square test (categorical variables). In the comparison of temperature measurements over time, the analysis of variance (ANOVA) and the contrast profile test were used for the difference in temperature between the times. The non-parametric Kruskal-Wallis test was used to compare the three groups. The level of significance was 5%.

RESULTS

regarding the studied variables, the groups were not homogeneous as to the categorical variable sex. All patients presented hypothermia during the intraoperative period (p> 0.05).

CONCLUSION

there was no significant difference between the heating methods in the prevention of intraoperative hypothermia. REBEC - Brazilian Registry of Clinical Trials (RBR- no. 52shjp).

Reducing Implant Infection in Orthopaedics (RIIiO): a pilot study for a randomised controlled trial comparing the influence of forced air versus resistive fabric warming technologies on postoperative infection rates following orthopaedic implant surgery in adults

Background

Approximately 70,000 to 75,000 proximal femoral fracture repairs take place in the UK each year. Hemiarthroplasty is the preferred treatment for adults aged over 60 years. Postoperative infection affects up to 3% of patients and is the single most common reason for early return to theatre. Ultraclean ventilation was introduced to help mitigate the risk of infection, but it may also contribute to inadvertent perioperative hypothermia, which itself is a risk for postoperative infection. To counter this, active intraoperative warming is used for all procedures that take 30 min or more. Forced air warming (FAW) and resistive fabric warming (RFW) are the two principal techniques used for this purpose; they are equally effective in prevention of inadvertent perioperative hypothermia, but it is not known which is associated with the lowest infection rates. Deep surgical site infection doubles operative costs, triples investigation costs and quadruples ward costs. The Reducing Implant Infection in Orthopaedics (RIIiO) study seeks to compare infection rates with FAW versus RFW after hemiarthroplasty for hip fracture. A cost-neutral intervention capable of reducing postoperative infection rates would likely lead to a change in practice, yield significant savings for the health economy, reduce overall exposure to antibiotics and improve outcomes following hip fracture in the elderly. The findings may be transferable to other orthopaedic implant procedures and to non-orthopaedic surgical specialties.

Methods

RIIiO is a parallel group, open label study randomising hip fracture patients over 60 years of age who are undergoing hemiarthroplasty to RFW or FAW. Participants are followed up for 3 months. Definitive deep surgical site infection within 90 days of surgery, the primary endpoint, is determined by a blinded endpoint committee.

Discussion

Hemiarthroplasty carries a risk of deep surgical site infection of approximately 3%. In order to provide 90% power to demonstrate an absolute risk reduction of 1%, using a 5% significance level, a full trial would need to recruit approximately 8630 participants. A pilot study is being conducted in the first instance to demonstrate that recruitment and data management strategies are appropriate and robust before embarking on a large multi-centre trial.

Trial registration

ISRCTN, ISRCTN74612906. Registered on 27 February 2017.

Electronic supplementary material

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The effectiveness of ultra-clean air operating theatres in the prevention of deep infection in joint arthroplasty surgery

Deep infection was identified as a serious complication in the earliest days of total hip arthroplasty. It was identified that airborne contamination in conventional operating theatres was the major contributing factor. As progress was made in improving the engineering of operating theatres, airborne contamination was reduced. Detailed studies were carried out relating airborne contamination to deep infection rates.

In a trial conducted by the United Kingdom Medical Research Council (MRC), it was found that the use of ultra-clean air (UCA) operating theatres was associated with a significant reduction in deep infection rates. Deep infection rates were further reduced by the use of a body exhaust system. The MRC trial also included a detailed microbiology study, which confirmed the relationship between airborne contamination and deep infection rates.

Recent observational evidence from joint registries has shown that in contemporary practice, infection rates remain a problem, and may be getting worse. Registry observations have also called into question the value of “laminar flow” operating theatres.

Observational evidence from joint registries provides very limited evidence on the efficacy of UCA operating theatres. Although there have been some changes in surgical practice in recent years, the conclusions of the MRC trial remain valid, and the use of UCA is essential in preventing deep infection.

There is evidence that if UCA operating theatres are not used correctly, they may have poor microbiological performance. Current UCA operating theatres have limitations, and further research is required to update them and improve their microbiological performance in contemporary practice.

Cite this article: Bone Joint J 2018;100-B:1264–9.

Multimodal temperature management during donor hepatectomy under combined general anaesthesia and neuraxial analgesia: Retrospective analysis

Background and Aims:

Unintended hypothermia (UIH) during surgery under general anaesthesia has adverse implications. A retrospective analysis of the perioperative temperature records of healthy voluntary liver donors was done to evaluate the efficacy of a multimodal protocol for temperature management.

Methods:

Records of 50 American Society of Anesthesiologists physical status Class 1 patients operated for Donor Hepatectomy lasting >2 h under combined general and epidural anaesthesia were analysed. Ambient temperature was maintained 24°C–27°C before induction of GA and during insertion of epidural catheter. Active warming was done using warming mattress set to temperature 38°C, hot air blanket with temperature set to 38°C and fluid warming device (Hotline™) with preset temperature of 41°C. Nasopharyngeal temperature was continuously monitored. After induction of GA and draping of the patient, ambient temperature was decreased and maintained at 21°C–24°C and was again increased to 24°C–27°C at the conclusion of surgery. During surgery, for every 0.1°C above 37°C, one heating device was switched off such that at 37.3°C all the 3 devices were switched off. Irrigation fluid was pre-warmed to 39°C.

Results:

Baseline temperature was 35.9°C ± 0.4°C. Minimum temperature recorded was 35.7°C ± 0.4°C. Mean decrease in temperature below the baseline temperature was 0.2°C ± 0.2°C. Temperature at the end of surgery was 37.4°C ± 0.5°C.

Conclusion:

Protocol-based temperature management with simultaneous use of resistive heating mattress, forced-air warming blanket, and fluid warmer along with ambient temperature management is an effective method to prevent unintended perioperative variation in body temperature.

Persistent Hypothermia and Excessive Sweating Following Intrathecal Morphine Administration in a Teenage Boy: A Case Report

Introduction

Opioids are used intrathecally to manage surgical pain. There are few reports of hypothermia after spinal morphine injection, none in the pediatric population. We present a teenager's case of mild hypothermia.

Case Presentation

A 15-year-old boy was scheduled for elective abdominal laparotomy. General anesthesia was combined with spinal anesthesia, using levobupivacaine and morphine. In the recovery room, he presented a decreased tympanic temperature (34.4°C) associated with excessive sweating, hyperglycemia, and complained of feeling hot. All other vital signs were normal. It was decided to maintain clinical vigilance and hourly monitoring of temperature and glycaemia values. Despite active warming, he remained hypothermic for 16 hours, with gradual remission of symptoms and normalization of glycemic values. It is unknown how intrathecal morphine causes hypothermia. The most viable hypothesis is its effect on the hypothalamus. In our case the most probable causes of post anesthesia hypothermia were excluded; therefore, we can admit that the cause of hypothermia was the spinal administration of morphine. Some reports used naloxone and lorazepam successfully. In our report, they disappeared spontaneously 16 hours later, which corroborates our diagnosis.

Conclusions

Children undergoing subarachnoid block with with intrathecal morphine may develop a disruption on thermoregulation, leading to a resistant postoperative hypothermia associated with excessive sweating.

Surgery and magnetic resonance imaging increase the risk of hypothermia in infants

AIM

Maintaining normothermia is a tenet of neonatal care. However, neonatal thermal care guidelines applicable to intra-hospital transport beyond the neonatal intensive care unit (NICU) and during surgery or magnetic resonance imaging (MRI) are lacking. The aim of this study is to determine the proportion of infants normothermic (36.5-37.5°C) on return to NICU after management during surgery and MRI, and during standard clinical care in both environments.

METHODS

Sixty-two newborns requiring either surgery in the operating theatre (OT) (n = 41) or an MRI scan (n = 21) at the Royal Children's Hospital (Melbourne) NICU were prospectively studied. Core temperature, along with cardiorespiratory parameters, was continuously measured from 15 min prior to leaving the NICU until 60 min after returning. Passive and active warming (intra-operatively) was at clinician discretion.

RESULTS

The study reported 90% of infants were normothermic before leaving NICU: 86% (MRI) and 93% (OT). Only 52% of infants were normothermic on return to NICU (relative risk (RR) 1.75; 95% confidence interval (CI) 1.39-2.31; number needed to harm (NNH) 2.6). Between departure from the NICU and commencement of surgery, core temperature decreased by mean 0.81°C (95% CI 0.30-1.33; P = 0.0001, analysis of variance), with only 24% of infants normothermic when surgery began (P < 0.0001; RR 3.80 (95% CI 2.33-6.74); NNH 1.5). After an MRI, infants were a mean 0.41°C (95% CI 0.16-0.67) colder than immediately before entering the scanner (P = 0.001, analysis of variance), with only 43% being normothermic (P = 0.003; RR 2.11 (95% CI 1.35-3.74); NNH 2.1).

CONCLUSION

Unintentional hypothermia is a common occurrence during surgery in the OT and MRI in neonates, indicating that evidence-based warming strategies to prevent hypothermia should be developed.

Risk factors for development of surgical site infections among liver transplantation recipients: An integrative literature review

BACKGROUND

Surgical site infection (SSI) is an important complication in the postoperative period of recipients of liver transplantation. The purpose of this integrative literature review is to summarize the knowledge available about the risk factors contributing to the development SSI among adults undergoing liver transplantation.

METHODS

We reviewed the Medical Literature Analysis and Retrieval System Online/PubMed, the Cumulative Index to Nursing and Allied Health Literature, the Latin American and Caribbean Health Sciences Literature, Scopus, and Web of Science databases.

RESULTS

Two hundred sixteen articles were identified and the final sample of 9 articles was analyzed in full length. The SSI rate found in the investigations ranged between 9.6% and 35.5%. Risk factors for SSI were grouped into categories related to the preoperative period, such as Model for End-Stage Renal Disease score > 35 and ventilated support on day of transplant; to the intraoperative period activity, such as transfusion of packed red blood cells, extended surgical time, hyperglycemia >200 mg/dL, use of vasopressor drugs, and ascites flow >1 L; and to the donor/recipient relationship, such as age differences >10 years, ratio of donor liver mass to recipient body mass < 0.01. Additionally, centers that annually perform <50 transplants appear to have higher rates of SSI.

CONCLUSIONS

Few studies have addressed the subject of SSI in relation to liver transplantation in the scientific literature. Risk factors for SSI in patients who underwent liver transplantation vary between institutions.

Randomised trial comparing forced-air warming to the upper or lower body to prevent hypothermia during thoracoscopic surgery in the lateral decubitus position

BACKGROUND

In the supine position, forced-air warming is more effective on the lower body than on the upper body to prevent intraoperative hypothermia. However, it is unknown in the lateral decubitus position. We thus compared forced-air warming on the upper and lower bodies in the lateral position.

METHODS

Patients (n=123) were randomised to receive forced-air warming on the upper body or lower body during thoracoscopic surgery in the lateral position. We measured the nasopharyngeal temperature at 0, 30, 60, 90, and 120 min after lateral positioning during surgery and the infrared tympanic membrane temperature at 0, 30, 60, 90, and 120 min after surgery. Patients received both upper and lower body warming at a temperature of <35.5°C. The primary outcome was the incidence of intraoperative hypothermia with a temperature of <36.0°C.

RESULTS

Intraoperative hypothermia was less frequent with the upper body warming than with the lower body warming {21/62 vs 35/61, risk ratio [95% confidence interval (CI)] 0.6 (0.4-0.9), P=0.011}. The intraoperative temperature was higher with the upper body warming than with the lower body warming at 30 (P=0.002), 60 (P<0.001), and 90 (P<0.001) min after lateral positioning, and the postoperative temperature was higher at 0 (P<0.001) and 30 (P=0.001) min after surgery. Fewer patients received both upper and lower body warming in the upper body warming group than in the lower body warming group during surgery (1 vs 7, P=0.032).

CONCLUSIONS

Forced-air warming was more effective on the upper body than on the lower body to prevent hypothermia during thoracoscopic surgery in the lateral decubitus position.

CLINICAL TRIAL REGISTRATION

NCT02993666.

Consequences of Transfusing Blood Components in Patients With Trauma: A Conceptual Model

Transfusion of blood components is often required in resuscitation of patients with major trauma. Packed red blood cells and platelets break down and undergo chemical changes during storage (known as the storage lesion) that lead to an inflammatory response once the blood components are transfused to patients. Although some evidence supports a detrimental association between transfusion and a patient's outcome, the mechanisms connecting transfusion of stored components to outcomes remain unclear. The purpose of this review is to provide critical care nurses with a conceptual model to facilitate understanding of the relationship between the storage lesion and patients' outcomes after trauma; outcomes related to trauma, hemorrhage, and blood component transfusion are grouped according to those occurring in the short-term (≤30 days) and the long-term (>30 days). Complete understanding of these clinical implications is critical for practitioners in evaluating and treating patients given transfusions after traumatic injury.

Temperature management under general anesthesia: Compulsion or option

Administration of general anesthesia requires continuous monitoring of vital parameters of the body including body temperature. However, temperature continues to be one of the least seriously monitored parameters perioperatively. Inadvertent perioperative hypothermia is a relatively common occurrence with both general and regional anesthesia and can have significant adverse impact on patients' outcome. While guidelines for perioperative temperature management have been proposed, there are no specific guidelines regarding the best site or best modality of temperature monitoring and management intraoperatively. Various warming and cooling devices are available which help maintain perioperative normothermia. This article discusses the physiology of thermoregulation, effects of anesthesia on thermoregulation, various temperature monitoring sites and methods, perioperative warming devices, guidelines for perioperative temperature management and inadvertent temperature complications (hypothermia/hyperthermia) and measures to control it in the operating room.

Forced-Air Warming for Rewarming and Comfort Following Laparoscopy: A Randomized Controlled Trail

We investigated the efficacy of a forced-air warming (FAW) system on postoperative rewarming and comfort in patients undergoing laparoscopic surgery. In this randomized controlled trial, a total of 127 participants were randomly divided into the FAW group ( n = 64) and control group ( n = 63). The esophageal temperature was measured every 30 min during surgery, and the tympanic temperature and comfort levels were measured preoperatively and in the postanesthesia care unit (PACU). Data analysis used the generalized estimating equation. We found that there was a lower incidence of postoperative hypothermia in the FAW group compared with the control group, as well as a higher body temperature between 30 and 180 min in the PACU, a shorter time for rewarming, and a higher comfort level. Taken together, these results suggest that FAW is an effective rewarming technique for laparoscopic patients during surgery and in the PACU that improves comfort levels.

Comparison of forced-air and water-circulating warming for prevention of hypothermia during transcatheter aortic valve replacement

Introduction

Transcatheter Aortic Valve Replacement (TAVR) procedures at our institution were complicated by perioperative hypothermia despite use of the standard of care forced-air convective warming device (the BairHugger, Augustine Medical Inc, Eden Prairie, MN, USA). To remedy this problem, we initiated a quality improvement process that investigated the use of a conductive warm water-circulating device (the Allon ThermoWrap, Menen Medical Corporation, Trevose, PA, USA), and hypothesized that it would decrease the incidence of perioperative hypothermia.

Methods

We compared two different intraoperative warming devices using a historic control. We retrospectively reviewed intraoperative records of 80 TAVRs between 6/2013 and 6/2015, 46 and 34 of which were done with the forced-air and water-circulating devices, respectively. Continuous temperature data obtained from pulmonary artery catheter, temperature upon arrival to cardiothoracic ICU (CTU), age, BSA, height, and BMI were compared.

Results

Patients warmed with both devices were similar in terms of demographic characteristics. First recorded intraoperative temperature (mean 36.26 ± SD 0.61 vs. 35.95 ± 0.46°C, p = 0.02), lowest intraoperative temperature (36.01 ± 0.58 vs. 34.89 ± 0.76°C, p<0.001), temperature at the end of the procedure (36.47 ± 0.51 vs. 35.17 ± 0.75°C, p<0.001), and temperature upon arrival to the CTU (36.35 ± 0.44 vs. 35.07 ± 0.78°C, p<0.001) were significantly higher in the water-circulating group as compared to the forced-air group.

Conclusion

A quality improvement process led to selection of a new warming device that virtually eliminated perioperative hypothermia at our institution. Patients warmed with the new device were significantly less likely to experience intraoperative hypothermia and were significantly more likely to be normothermic upon arrival to the CTU.

Factors that influence effective perioperative temperature management by anesthesiologists: a qualitative study using the Theoretical Domains Framework

PURPOSE

Inadvertent perioperative hypothermia (IPH) is associated with a range of adverse outcomes. Safe and effective warming techniques exist to prevent IPH; however, IPH remains common. This study aimed to identify factors that anesthesiologists perceive may influence temperature management during the perioperative period.

METHODS

After Research Ethics Board approval, semi-structured interviews were conducted with staff anesthesiologists at a Canadian academic hospital. An interview guide based on the Theoretical Domains Framework (TDF) was used to capture 14 theoretical domains that may influence temperature management. The interview transcripts were coded using direct content analysis to generate specific beliefs and to identify relevant TDF domains perceived to influence temperature management behaviour.

RESULTS

Data saturation was achieved after 15 interviews. The following nine theoretical domains were identified as relevant to designing an intervention for practices in perioperative temperature management: knowledge, beliefs about capabilities, beliefs about consequences, reinforcement, memory/attention/decision-making, environmental context and resources, social/professional role/identity, social influences, and behavioural regulation. Potential target areas to improve temperature management practices include interventions that address information needs about individual temperature management behaviour as well as patient outcome (feedback), increasing awareness of possible temperature management strategies and guidelines, and a range of equipment and surgical team dynamics that influence temperature management.

CONCLUSION

This study identified several potential target areas for future interventions from nine of the TDF behavioural domains that anesthesiologists perceive to drive their temperature management practices. Future interventions that aim to close the evidence-practice gap in perioperative temperature management may include these targets.

Guideline Implementation: Preventing Hypothermia

The updated AORN "Guideline for prevention of unplanned patient hypothermia" provides guidance for identifying factors associated with intraoperative hypothermia, preventing hypothermia, educating perioperative personnel on this topic, and developing relevant policies and procedures. This article focuses on key points of the guideline, which addresses performing a preoperative assessment for factors that may contribute to hypothermia, measuring and monitoring the patient's temperature in all phases of perioperative care, and implementing interventions to prevent hypothermia. Perioperative RNs should review the complete guideline for additional information and for guidance when writing and updating policies and procedures.

Comparison of resistive heating and forced-air warming to prevent inadvertent perioperative hypothermia

BACKGROUND

Forced-air warming is a commonly used warming modality, which has been shown to reduce the incidence of inadvertent perioperative hypothermia (<36°C). The reusable resistive heating mattresses offer a potentially cheaper alternative, however, and one of the research recommendations from the National Institute for Health and Care Excellence was to evaluate such devices formally. We conducted a randomized single-blinded study comparing perioperative hypothermia in patients receiving resistive heating or forced-air warming.

METHODS

A total of 160 patients undergoing non-emergency surgery were recruited and randomly allocated to receive either forced-air warming (n=78) or resistive heating (n=82) in the perioperative period. Patient core temperatures were monitored after induction of anaesthesia until the end of surgery and in the recovery room. Our primary outcome measures included the final intraoperative temperature and incidence of hypothermia at the end of surgery.

RESULTS

There was a significantly higher rate of hypothermia at the end of surgery in the resistive heating group compared with the forced-air warming group (P=0.017). Final intraoperative temperatures were also significantly lower in the resistive heating group (35.9 compared with 36.1°C, P=0.029). Hypothermia at the end of surgery in both warming groups was common (36% forced air warming, 54% resistive heating).

CONCLUSION

Our results suggest that forced-air warming is more effective than resistive heating in preventing postoperative hypothermia.

CLINICAL TRIAL REGISTRATION

NCT01056991.

Meta-analysis: effectiveness of forced-air warming for prevention of perioperative hypothermia in surgical patients

AIM

The aim of this study was to evaluate the effectiveness of forced-air warming for preventing perioperative hypothermia.

BACKGROUND

Perioperative hypothermia commonly occurs in patients receiving anaesthesia during surgeries. However, the effectiveness of warming systems requires verification.

DESIGN

Systematic review incorporating meta-analysis.

DATA SOURCES

We searched OVID, PubMed, Cochrane Library, Medline, CINAHL, CETD and CEPS databases (2001-2015) for randomized controlled trials published in English and Chinese. Outcome measures of interests were body temperature and thermal comfort.

REVIEW METHODS

Cochrane methods, Quality of evidence (GRADE) assessments and Jadad Quality Score were used.

RESULTS

Twenty-nine trials (1875 patients) met inclusion criteria, including seven trials (502 patients) related to thermal comfort. Results showed that: (1) forced-air warming was more effective than passive insulation and circulating-water mattresses; (2) there was no statistically significant difference among forced-air warming, resistive heating blankets, radiant warming systems and circulating-water garments; and (3) that thermal comfort provided by forced-air warming was superior to that of passive insulation, resistive heating blankets and radiant warming systems, but inferior to that of circulating-water mattresses.

CONCLUSIONS

Forced-air warming prevents perioperative hypothermia more effectively than passive insulation and circulating-water mattresses, whereas there is no statistically significant difference in its effectiveness compared with circulating-water garments, resistive heating blankets and radiant warming systems.

Perioperative hypothermia: Causes, consequences and treatment

Perioperative hypothermia, core temperature below 36.0 °C, transpires due to disruption of thermoregulation by anesthesia coupled with cold exposure to procedural surroundings and cleansing agents. Although most publications have focused on thermoregulation disruption with general anesthesia, neuraxial anesthesia may also cause significant hypothermia. The clinical consequences of perioperative hypothermia are multiple and include patient discomfort, shivering, platelet dysfunction, coagulopathy, and increased vasoconstriction associated with a higher risk of wound infection. Furthermore, postoperative cardiac events occur at a higher rate; although it is unclear whether this is due to increased oxygen consumption or norepinephrine levels. Hypothermia may also affect pharmacokinetics and prolong postoperative recovery times and hospital length of stay. In order to combat perioperative hypothermia, many prevention strategies have been examined. Active and passive cutaneous warming are likely the most common and aim to both warm and prevent heat loss; many consider active warming a standard of care for surgeries over one hour. Intravenous nutrients have also been examined to boost metabolic heat production. Additionally, pharmacologic agents that induce vasoconstriction have been studied with the goal of minimizing heat loss. Despite these multiple strategies for prevention and treatment, hypothermia continues to be a problem and a common consequence of the perioperative period. This literature review presents the most recent evidence on the disruption of temperature regulation by anesthesia and perioperative environment, the consequences of hypothermia, and the methods for hypothermia prevention and treatment.

[Anesthetic management of severe or worsening postpartum hemorrhage]

INTRODUCTION

Risk factors of maternal morbidity and mortality during postpartum hemorrhage (PPH) include non-optimal anesthetic management. As the anesthetic management of the initial phase is addressed elsewhere, the current chapter is dedicated to the management of severe PPH.

METHODS

A literature search was performed using PubMed and Medline databases, and the Cochrane Library, for articles published from 2003 up to and including 2013. Several keywords related to anesthetic and critical care practice, and obstetrical management were used, in various combinations. Guidelines from several societies and organisations were also read.

RESULTS

When PPH worsens, one should ask for additional team personnel (professional consensus). Patients should be monitored for heart rate, blood pressure, skin and mucosal pallor, bleeding at skin puncture sites, diuresis and the volume of genital bleeding (grade B). Because of the possible rapid worsening of coagulapathy, patients should undergo regular evaluation of coagulation status (professional consensus). Prevention and management of hypothermia should be considered (professional consensus), by warming intravenous fluids and blood products, and by active body warming (grade C). Antibiotics should be given, if not already administered at the initial phase (professional consensus). Vascular fluids must be given (grade B), the choice being left at the physician discretion. Blood products transfusion should be decided based on the clinical severity of PPH (professional consensus). Priority is given to red blood cells (RBC) transfusion, with the aim to maintain Hb concentration>8g/dL. The first round of products could include 3 units of RBC (professional consensus), and the following round 3 units of RBC, and 3 units of fresh frozen plasma (FFP). The FFP:RBC ratio should be kept between 1:2 and 1:1 (professional consensus). Depending on the etiology of PPH, the early administration of FFP is left at the discretion of the physician (professional consensus). Platelet count should be maintained at>50 G/L (professional consensus). During massive PPH, fibrinogen concentration should be maintained at>2g/L (professional consensus). Fibrinogen can be given without prior fibrinogen measurement in case of massive bleeding (professional consensus). General anesthesia should be considered in case of hemodynamic instability, even when an epidural catheter is in place (professional consensus).

CONCLUSION

The anesthetic management aims to restore and maintain optimal respiratory state and circulation, to treat coagulation disorders, and to allow invasive obstetrical and radiologic procedures. Clinical and instrumental monitoring are needed to evaluate the severity of PPH, to guide the choice of therapeutic options, and to assess treatments efficacy.