Forced-air and a novel patient-warming system (vitalHEAT vH2) comparably maintain normothermia during open abdominal surgery. Anesth Analg. 2011;112:608-614. [PMID: 20841410 DOI: 10.1213/ane.0b013e3181e7cc20]

The effect of rewarming on hemodynamic parameters and arterial blood gases of patients after open-heart surgery: A randomized controlled trial

INTRODUCTION

Hypothermia after open-heart surgery can have potential side effects for patients.

AIM

This study aimed to examine the effects of rewarming on patients' hemodynamic and arterial blood gases parameters after open-heart surgery.

METHODS

This randomized controlled trial was performed in 2019 on 80 patients undergoing open-heart surgery at Tehran Heart Center, Iran. The subjects were consecutively recruited and randomly assigned to an intervention group (n=40) and a control group (n=40). After the surgery, the intervention group was warmed with an electric warming mattress while the control group warmed using a simple hospital blanket. The hemodynamic parameters of the two groups were measured 6 times and arterial blood gas was measured 3 times. Data were analyzed by independent samples t and Chi-squared tests, and repeated measures analysis.

RESULTS

Before the intervention, the two groups did not significantly differ in terms of hemodynamic and blood gas parameters. However, the two groups were significantly different in the mean heart rate, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, temperature, right and left lung drainage in the first half-hour, and the first to fourth hours after the intervention (p < 0.05). Furthermore, there was a significant difference between the mean arterial oxygen pressure of the two groups during and after rewarming (P <0.05).

CONCLUSION

Rewarming of patients after open-heart surgery can significantly affect hemodynamic and arterial blood gas parameters. Therefore, rewarming methods can be used safely to improve the patients' hemodynamic parameters after open-heart surgery.

Educational Perspectives: Anesthesia 101: What the Neonatologist Needs to Know About Anesthesiology

As the complexity of medicine increases, so too do the challenges with multidisciplinary communication and coordinated patient care. Anesthesiology represents a field for which there is no required study for medical students, pediatric residents, or neonatal-perinatal medicine fellows in the United States, so a neonatologist may have never received any formal training in anesthesiology (and vice versa for pediatric anesthesiologists in neonatology). In this review, we address frequently asked questions of neonatologists to anesthesiologists to better frame common issues. These topics include thermal regulation, fluid management, airway management, and the field of regional anesthesiology. Finally, collaborative efforts between the surgical and medical fields, such as the American College of Surgeons Children's Surgery Verification Quality Improvement Program, and the American Academy of Pediatrics NICU Verification Program, are ongoing and robust; these programs represent important opportunities to significantly improve the perioperative care of infants. Our hope is that this summary can serve as a primer and reference for those caring for neonatal patients during any perioperative period, including seasoned neonatologists and those early in their training. It is our further desire that this review will lead to improved communication and collegiality between the specialties.

From Nanowarming to Thermoregulation: New Multiscale Applications of Bioheat Transfer

This review explores bioheat transfer applications at multiple scales from nanoparticle (NP) heating to whole-body thermoregulation. For instance, iron oxide nanoparticles are being used for nanowarming, which uniformly and quickly rewarms 50-80-mL (≤5-cm-diameter) vitrified systems by coupling with radio-frequency (RF) fields where standard convective warming fails. A modification of this approach can also be used to successfully rewarm cryopreserved fish embryos (∼0.8 mm diameter) by heating previously injected gold nanoparticles with millisecond pulsed laser irradiation where standard convective warming fails. Finally, laser-induced heating of gold nanoparticles can improve the sensitivity of lateral flow assays (LFAs) so that they are competitive with laboratory tests such as the enzyme-linked immunosorbent assay. This approach addresses the main weakness of LFAs, which are otherwise the cheapest, easiest, and fastest to use point-of-care diagnostic tests in the world. Body core temperature manipulation has now become possible through selective thermal stimulation (STS) approaches. For instance, simple and safe heating of selected areas of the skin surface can open arteriovenous anastomosis flow in glabrous skin when it is not already established, thereby creating a convenient and effective pathway to induce heat flow between the body core and environment. This has led to new applications of STS to increase or decrease core temperatures in humans and animals to assist in surgery (perioperative warming), to aid ischemic stress recovery (cooling), and even to enhance the quality of sleep. Together, these multiscale applications of nanoparticle heating and thermoregulation point to dramatic opportunities for translation and impact in these prophylactic, preservative, diagnostic, and therapeutic applications of bioheat transfer.

Prevention of laparoscopic surgery induced hypothermia with warmed humidified insufflation: Is the experimental combination of a warming blanket synergistic?

INTRODUCTION

Maintaining normothermia during anesthesia is imperative to provide quality patient care and to prevent adverse outcomes. Prolonged laparoscopic procedures have been identified as a potential risk factor for hypothermia, due to continuous insufflation of cold and dry carbon dioxide. Perioperative hypothermia is associated with increased hospital cost and many complications including; impaired drug metabolism, impaired immune function, cardiac morbidity, shivering, coagulopathy.

METHODS

In this experimental study, four pigs underwent four interventions each, resulting in 16 total trials. Using standardized general anesthesia in a randomized Latin-square sequence the four interventions include: 1. Control group without an administered pneumoperitoneum, 2. Administered standard pneumoperitoneum using 21°C insufflated gas and under-body forced-air warming, 3. Administered pneumoperitoneum with insufflation of warmed/humidified carbon dioxide, 4. Administered pneumoperitoneum with insufflation of warmed/humidified carbon dioxide and under-body forced-air warming. The primary outcome was distal esophageal temperature change 4 hours after trocar insertion.

RESULTS

Four hours after trocar insertion, pigs in the control group lost 2.1 ± 0.4°C; pigs with warmed and humidified insufflation lost 1.8 ± 0.4°C; pigs with forced-air warming group lost 1.3 ± 0.9°C; and pigs exposed to a combination of warmed and humidified insufflation with forced-air warming increased by 0.3 ± 0.2°C.

CONCLUSION

This experimental animal study provides evidence that a combination of warmed and humidified insufflation of carbon dioxide (CO2) in conjunction with forced-air warming is an effective strategy in the prevention of perioperative hypothermia. Further clinical trials investigating humans are therefore indicated.

From Nanowarming to Thermoregulation: New Multiscale Applications of Bioheat Transfer

This review explores bioheat transfer applications at multiple scales from nanoparticle (NP) heating to whole-body thermoregulation. For instance, iron oxide nanoparticles are being used for nanowarming, which uniformly and quickly rewarms 50-80-mL (≤5-cm-diameter) vitrified systems by coupling with radio-frequency (RF) fields where standard convective warming fails. A modification of this approach can also be used to successfully rewarm cryopreserved fish embryos (∼0.8 mm diameter) by heating previously injected gold nanoparticles with millisecond pulsed laser irradiation where standard convective warming fails. Finally, laser-induced heating of gold nanoparticles can improve the sensitivity of lateral flow assays (LFAs) so that they are competitive with laboratory tests such as the enzyme-linked immunosorbent assay. This approach addresses the main weakness of LFAs, which are otherwise the cheapest, easiest, and fastest to use point-of-care diagnostic tests in the world. Body core temperature manipulation has now become possible through selective thermal stimulation (STS) approaches. For instance, simple and safe heating of selected areas of the skin surface can open arteriovenous anastomosis flow in glabrous skin when it is not already established, thereby creating a convenient and effective pathway to induce heat flow between the body core and environment. This has led to new applications of STS to increase or decrease core temperatures in humans and animals to assist in surgery (perioperative warming), to aid ischemic stress recovery (cooling), and even to enhance the quality of sleep. Together, these multiscale applications of nanoparticle heating and thermoregulation point to dramatic opportunities for translation and impact in these prophylactic, preservative, diagnostic, and therapeutic applications of bioheat transfer.

Forced air warming to maintain normoTHERMIa during SEDation in the cardiac catheterization laboratory: protocol for the THERMISED pilot randomized controlled trial

AIM

To determine whether applying forced air warming attenuates the impact of sedation-induced impairment of thermoregulation on body temperature of patients who are sedated during interventional procedures in the cardiac catheterization laboratory.

BACKGROUND

A moderate proportion of sedated patients who undergo procedures in the cardiac catheterization laboratory with only passive warming become hypothermic. Hypothermia in the surgical population is associated with increased risk of adverse cardiac events, infections, thrombotic and haemorrhagic complications and prolonged hospital stay. For this reason, investigation of the clinical benefits of preventing hypothermia in sedated patients using active warming is required.

DESIGN

Randomized controlled trial.

METHODS

A total of 140 participants undergoing elective interventional procedures with sedation in a cardiac catheterization laboratory will be recruited from two hospitals in Australia. Participants will be randomized to receive forced air warming (active warming) or usual care (passive warming with heated cotton blankets) throughout procedures. The primary outcome is hypothermia (defined as temperature less than 36°C) at the conclusion of the procedure. Secondary outcomes are postprocedure temperature, postprocedural shivering, thermal discomfort, major complications, disability-free survival to 30 days postprocedure, cost-effectiveness and feasibility of conducting a larger clinical trial.

DISCUSSION

The results from this study will provide high-level evidence for practice in an area where there is currently no guidance. Findings will be easily translatable into clinical practice because most hospitals already have forced air warming equipment available for use during general anaesthesia.

REGISTRATION NUMBER

ACTRN12616000013460.

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.

Comparing new-technology passive warming versus traditional passive warming methods for optimizing perioperative body core temperature

Hypothermia puts surgical patients at risk for adverse outcomes. Traditional passive warming methods are mostly ineffective in reducing hypothermia. New-technology passive warming holds promise as an effective method for promoting and sustaining normothermia throughout surgery. The purpose of this retrospective cohort study was to compare the effectiveness of new-technology passive warming with traditional methods. We measured core body temperature at anesthesia induction and at the end of surgery for patients undergoing robotic-assisted prostatectomy/hysterectomy in the lithotomy position who received either new-technology passive warming (n = 30) or traditional linens and gel pads (n = 35). The traditionally warmed cohort had no change in temperature (35.9° C ± 0.6° C presurgery vs 35.9° C ± 0.7° C postsurgery; t = 0.47; P = .66). The intervention cohort showed a significant increase in temperature (35.75° C ± 0.52° C presurgery vs 36.30° C ± 0.53° C postsurgery; t = 4.64; P < .001). A repeated-measure analysis of variance adjusting for surgery duration and fluid administration confirmed the significance (F = 17.254; P < .001), suggesting that new-technology passive warming may effectively complement active warming to reduce perioperative hypothermia.

Peri-operative warming devices: performance and clinical application

Since the adverse consequences of accidental peri-operative hypothermia have been recognised, there has been a rapid expansion in the development of new warming equipment designed to prevent it. This is a review of peri-operative warming devices and a critique of the evidence assessing their performance. Forced-air warming is a common and extensively tested warming modality that outperforms passive insulation and water mattresses, and is at least as effective as resistive heating. More recently developed devices include circulating water garments, which have shown promising results due to their ability to cover large surface areas, and negative pressure devices aimed at improving subcutaneous perfusion for warming. We also discuss the challenge of fluid warming, looking particularly at how devices' performance varies according to flow rate. Our ultimate aim is to provide a guide through the bewildering array of devices on the market so that clinicians can make informed and accurate choices for their particular hospital environment.

[Infection prevention by the anesthesia team]

The anesthesia team acts every day in a highly complex and high risk environment for the transmission of pathogenic organisms and the induction of infectious complications. With strict adherence to standard precautions and infection control practices in particular regular hand disinfection before and after direct patient contact and before performance of aseptic tasks during anesthesia and an optimized perioperative process the members of the anesthesia team can become infection control pioneers within the hospital. In order to be successful, structural and organizational resources in the form of training, personnel, materials and time, need to be adequate for the situation. This review summarizes the infection control recommendations for anesthesia practice based on the most recent literature and guidelines and offers practical advice for commonly observed mistakes.

Maintenance of core body temperature in anaesthetised pigeons (Columba livia domestica): a comparison of two thermal devices

Active thermal devices are used to prevent hypothermia during anaesthetic procedures. Two thermal devices, one conductive and one convective, were compared for their effect on maintenance of core body temperature (CBT) during 1h of general anaesthesia in pigeons (Columba livia domestica). In a randomised crossover trial, CBT decreased significantly less with the conductive device than when the convective device was used (2.5 ± 0.7°C and 3.8 ± 0.9°C, respectively; P<0.01). Moreover, CBT was maintained above a clinically acceptable level of 38.3°C in 82% of pigeons when the conductive device was selected, compared to 14% of pigeons with the convective device. The use of the conductive device is therefore recommended in preference to the convective device when performing anaesthetic procedures in birds.