Forced-air Blanket Research Articles

A Pilot Quality Improvement Project to Reduce Intraoperative MRI Hypothermia in Neurosurgical Patients.

Introduction:Intraoperative hypothermia increases patient morbidity, including bleeding and infection risk. Neurosurgical intraoperative magnetic resonance imaging (iMRI) can lead to hypothermia from patient exposure and low ambient temperature in the MRI suite. This quality improvement project aimed to reduce the risk of hypothermia during pediatric neurosurgery laser ablation procedures with iMRI. The primary aim was to increase the mean lowest core temperature in pediatric patients with epilepsy during iMRI procedures by 1 °C from a baseline mean lowest core temperature of 34.2 ± 1.2 °C within 10 months and sustain for 10 months.Methods:This report is a single-institution quality improvement project from March 2019 to June 2021, with 21 patients treated at a pediatric hospital. After identifying key drivers, temperature-warming interventions were instituted to decrease hypothermia among patients undergoing iMRI during neurosurgery procedures. A multidisciplinary team of physicians, nurses, and MRI technologists convened for huddles before each case. Interventions included prewarmed operating rooms (ORs), blanket coverings, MRI table and room; forced-air blanket warming, temperature monitoring in the OR and iMRI environments; and the MRI fan turned off.Results:Data were analyzed for five patients before and nine patients after the institution of the temperature-warming elements. The sustainment period included 15 patients. The mean lowest intraoperative temperature rose from 34.2 ± 1.3 °C in the preintervention period to 35.5 ± 0.6 °C in sustainment (P = 0.004).Conclusion:Hybrid OR and MRI procedures increase hypothermia risk, which increases patient morbidity. Implementation of a multidisciplinary, multi-item strategy for patient warming mitigates the risk.

Effect of prewarming on body temperature in short-term bladder or prostatic transurethral resection under general anesthesia: A randomized, double-blind, controlled trial

Perioperative hypothermia causes postoperative complications. Prewarming reduces body temperature decrease in long-term surgeries. We aimed to assess the effect of different time-periods of prewarming on perioperative temperature in short-term transurethral resection under general anesthesia. Randomized, double-blind, controlled trial in patients scheduled for bladder or prostatic transurethral resection under general anesthesia. Eligible patients were randomly assigned to receive no-prewarming or prewarming during 15, 30, or 45 min using a forced-air blanket in the pre-anesthesia period. Tympanic temperature was used prior to induction of anesthesia and esophageal temperature intraoperatively. Primary outcome was the difference in core temperature among groups from the induction of general anesthesia until the end of surgery. Repeated measures multivariate analysis of covariance modeled the temperature response at each observation time according to prewarming. We examined modeled contrasts between temperature variables in subjects according to prophylaxis. We enrolled 297 patients and randomly assigned 76 patients to control group, 74 patients to 15-min group, 73 patients to 30-min group, and 74 patients to the 45-min group. Temperature in the control group before induction was 36.5 ± 0.5 °C. After prewarming, core temperature was significantly higher in 15- and 30-min groups (36.8 ± 0.5 °C, p = 0.004; 36.7 ± 0.5 °C, p = 0.041, respectively). Body temperature at the end of surgery was significantly lower in the control group (35.8 ± 0.6 °C) than in the three prewarmed groups (36.3 ± 0.6 °C in 15-min, 36.3 ± 0.5 °C in 30-min, and 36.3 ± 0.6 °C in 45-min group) (p < 0.001). Prewarming prior to short-term transurethral resection under general anesthesia reduced the body temperature drop during the perioperative period. These time-periods of prewarming also reduced the rate of postoperative complications.Study Registration Registered at ClinicalTrials.gov (Identifier: NCT03630887).

Comparison of upper and lower body forced air blanket to prevent perioperative hypothermia in patients who underwent spinal surgery in prone position: a randomized controlled trial

BackgroundWe compared upper- and lower-body forced-air blankets in terms of their ability to prevent perioperative hypothermia, defined as a reduction in body temperature to < 36.0°C, during the perioperative period in patients undergoing spine surgery in the prone position.MethodsIn total, 120 patients scheduled for elective spine surgery under general anesthesia were divided into an upper-warming group (n = 60) and a lower-warming group (n = 60). After inducing anesthesia and preparing the patient for surgery, including prone positioning, the upper and lower bodies of the patients in the upper- and lower-warming groups, respectively, were warmed using a forced-air warmer with specified upper and lower blankets. Body temperature was measured using a tympanic membrane thermometer during the pre- and post-operative periods and using a nasopharyngeal temperature probe during the intraoperative period. Patients were evaluated in terms of shivering, thermal comfort, and satisfaction in the post-anesthesia care unit (PACU).ResultsThe incidence of intraoperative and postoperative hypothermia was lower in the upper-warming group than in the lower-warming group ([55.2% vs. 75.9%, P = 0.019] and [21.4% vs. 49.1%, P = 0.002]). Perioperative body temperature was higher in the upper-warming group (P < 0.001). However, intraoperative blood loss, postoperative thermal comfort scale and shivering scores, patient satisfaction, and PACU duration were similar in the two groups.ConclusionsThe upper-body blanket was more effective than the lower-body blanket for preventing perioperative hypothermia in patients who underwent spine surgery in the prone position.

Prewarming effect of transcutaneous acupoint electrical stimulation preconditioning in patients undergoing elective video-assisted thoracoscopic lobectomy

To observe the prewarming effect of transcutaneous acupoint electrical stimulation (TAES) preconditioning of Dazhui (GV14) and Mingmen (GV4) in patients undergoing elective video-assisted thoracoscopic lobectomy, so as to determine whether TAES can improve intraoperative hypothermia. A total of 80 patients undergoing elective video-assisted thoracoscopic lobectomy were randomly divided into TAES group (40 cases) and control group (40 cases). Before surgery, all the patients were transferred to the fixed area of an anesthetic preparation room by using a surgery cart carrying the same temperature sheets and quilts before surgery. TAES (2 Hz/100 Hz, 20-30 mA) was applied to Dazhui (GV14) and Mingmen (GV4) for 30 min for patients of the TAES group and the same sheet electrodes of EA stimulator were only attached to GV14 and GV 4 without electrical current transmission for patients in the control group. Then, these patients in the two groups were transferred to the operation room and treated by total intravenous anesthesia, and their anesthetic depth was monitored with bispectral index (BIS, between 45-60) and end-tidal carbon dioxide tension (PETCO2, between 30-45 mmHg). The auricular tympanic temperature was monitored, and when the temperature was below 35.5 ℃, forced-air blanket was used to warm the patient as the remedial measure. The same temperature of operation room, surgical drape, infusion solution and pleural lavage fluid were controlled. The patients' body temperature in the preparation room and operation room during surgery, incidence of hypothemia, blood pressure (BP), heart rate (HR), duration of anesthesia, duration of operation, blood loss volume, urine output, total infusion volume, recovery (awaking) time, and chills during recovery were recorded. The body temperature of patients in the TAES group was significantly higher than that in the control group at the time of entering the operation room (P<0.05). The incidence of chills during recovery was obviously lower in the TAES group (3/40,7.5%) than in the control group (7/40, 17.5%, P<0.05), and the recovery time was significantly shorter in the TAES group than in the control group (P<0.05). There were no significant differences between the two groups in the incidence of intraoperative hypothermia, the duration of anesthesia and operation, blood loss volume, urine output, total infusion volume, BP and HR (P>0.05). TAES preconditioning of GV14 and GV4 can produce prewarming effect before anesthesia, shorten the awaking time and reduce the incidence of chills in the recovery period in patients undergoing elective video-assisted thoracoscopic lobectomy.

DON'T MESS WITH TEXAS? DON'T MESS WITH THE COLD! ACCIDENTAL HYPOTHERMIA WITH CARDIAC ARREST TREATED SUCCESSFULLY WITH PROLONGED RESUSCITATION AND REWARMING

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Accidental hypothermia is an uncommon but potentially life-threatening presentation, more frequently occurring in colder climates. We present a case of severe hypothermia with cardiac arrest in the characteristically warm state of Texas, in a patient who had arrived to the emergency department (ED) several times during the prior week. CASE PRESENTATION: A 55 year old man with a history of alcohol (ETOH) abuse and schizophrenia is brought into the ED after being found down. Records indicate that he had arrived here 10 different times in the prior 2 weeks due to ETOH intoxication and mild hypothermia, with oral and rectal temperatures between 90-95°F. Each time, after being rewarmed, he would act inappropriately, verbally abusing staff despite warnings from security. Social workers provided warm clothing, shelter information, food pantry and other basic needs, but he would decline assistance and was escorted out by security. On this presentation, he was hypothermic to 79°F rectally, unresponsive and pulseless, in ventricular fibrillation (VF) cardiac arrest. CPR was initiated along with intubation, and a cardioversion once returned pulses. Active rewarming began with forced air blankets, warm IV fluids, bladder and esophageal irrigation. The patient again lost pulses, CPR was resumed and a second shock delivered with return of pulses. He then went into pulseless electrical activity (PEA), received multiple rounds of CPR and epinephrine, and had a return of pulses after 3 hours of resuscitation. Bilateral chest tubes were inserted and warm thoracic lavage began. His rectal temperatures improved to 85°F then to the 90s°F, in sinus rhythm with good distal pulses, and the medical Intensive care unit staff was notified for further management. Within days, he showed complete recovery neurologically and was successfully extubated. He did not meet criteria for involuntary commitment, engaged in motivational interviewing and was discharged in good spirits. He was provided transportation to another city where he stated his family resides. DISCUSSION: This patient arrived to the ED several times in the days prior with Stage I and II hypothermia, but his care was complicated by intoxication, combativeness, and he repeatedly refused resources. His last arrival to the ED required full cardiac resuscitation and active rewarming with thoracic lavage. This case illustrates the importance of identifying patients at risk for accidental hypothermia, particularly the homeless, and those with a history of alcohol abuse, even in central Texas. His case may highlight a paucity of guidelines and framework for homeless individuals at risk for hypothermia, in areas that typically remain warm year-round. CONCLUSIONS: Accidental hypothermia can be a life threatening presentation, and identification of those at risk, particularly the homeless, those with a history of alcohol abuse, and poor mental health, is vital. Reference #1: J L Tan, M Saks, J M DelCollo, M Paryavi, S Visvanathan, C Geller; Accidental hypothermia cardiac arrest treated successfully with invasive body cavity lavage, QJM: An International Journal of Medicine, Volume 111, Issue 8, 1 August 2018, Pages 563–564, https://doi.org/10.1093/qjmed/hcy075 Reference #2: Husby, P., Andersen, K.S., Owen-Falkenberg, A. et al. Intensive Care Med (1990) 16: 69. https://doi.org/10.1007/BF01706328 DISCLOSURES: No relevant relationships by Liwayway Andrade, source=Web Response No relevant relationships by Zachary Pinchover, source=Web Response No relevant relationships by Mohi Syed, source=Web Response

Automated closed-loop management of body temperature using forced-air blankets: preliminary feasibility study in a porcine model

BackgroundManagement of a patient’s body temperature is an important aspect of care that should be addressed by targeted temperature management (TTM). Often, non-invasive methods like forced-air blankets are used. Especially in the operating room this management may be a subsidiary and repetitive task requiring constant observation of the patient’s body temperature and adaption using the limited set of available settings. Thus, automation of TTM is a feasible target to improve patient outcome and reduce caregiver workload.MethodsA Philips IntelliVue MP 50 patient monitor with an arterial PiCCO catheter system was used to measure patient blood temperature. Thermal management was performed with a 3M Bair Hugger 755 warming unit with forced air blankets. The warming unit was extended by a computer interface to allow for remote and automated control. A proposed closed-loop algorithm reads the measured temperature and performs automated control of the 3M Bair Hugger. Evaluation was performed in an experimental intensive care setting for animal studies. Two fully automated trials are compared with two manual and two uncontrolled trials in the same study setting using six female pigs for prolonged observation times of up to 90 hours in each trial.ResultsThe developed system and proposed algorithm allow more precise temperature management by keeping a set target temperature within a range of ± 0.5 °C in 88% of the observation time and within a range of ± 1.0 °C at all times. The proposed algorithm yielded better performance than did manual control or uncontrolled trials. It was able to adapt to individual patient needs as it is more dynamic than look-up table approaches with fixed settings for various temperatures.ConclusionsClosed-loop TTM using non-invasive forced-air warming blankets was successfully tested in a porcine study with the proposed hardware interface and control algorithm. This automation can be beneficial for patient outcome and can reduce caregiver workload and patient risk in clinical settings. As temperature readings are most often available, existing devices like the 3M Bair Hugger can easily be expanded. However, even if clinical application is feasible, open questions regarding approval and certification of such automated systems within the current legal situation still need to be answered.

Forced-Air Warming in Patients Undergoing Endovascular Procedures: Comparison between 2 Thermal Blanket Models

The purpose of this study was to compare the efficiency between 2 thermal blanket models: the upper blanket and the underbody blanket in patient heating and hypothermia prevention during endovascular surgery. Fifty patients, American Society of Anesthesiologists physical status 2-4, receiving endovascular surgery repair of infrarenal abdominal aortic aneurysm or lower limb angioplasty by endovascular technique were studied. Primary outcome was to determine which forced-air blanket is more warming effective during the surgeries. Age, type of surgery, gender, body mass index, surgery duration, and initial patient temperature were analyzed to determine possible hypothermia association as secondary outcomes. Patients were randomized and split into 2 groups based on blanket model. All patients received general anesthesia, and temperature was obtained by an esophageal thermometer inserted after tracheal intubation and registered at intervals of 15 min until extubation. Groups significantly differed in body temperature (P = 0.006) and hypothermia occurrence (P = 0.020). The underbody blanket group hada higher ratio of hypothermic patients and a lower average temperature at the end of surgery. The average temperature after 60 min in the underbody blanket group was lower than the upper blanket group,although this difference was only significant after 150 min (P = 0.020). We conclude that upper thermal blanket is more effective thanunderbody thermal blanket in patient warming and hypothermia prevention during endovascular abdominal aortic aneurysm repair and lower limb angioplasty after 150 min of anesthetic-surgical time duration.

Use of Ultrasonography and Computed Tomography in the Diagnosis of Panophthalmitis in a Tuatara (Sphenodon punctatus)

Abstract A 605 g, mature, male tuatara (Sphenodon punctatus) was presented with periorbital swelling, exophthalmos, and hyphema of the right eye. Ultrasound examination showed distortion of the globe, an altered lens contour, heterogeneous vitreous content, and a loss of ocular and retrobulbar tissue planes. Computed tomography demonstrated displacement of the scleral ossicles but an absence of orbital bone lesions. A decision was made to enucleate the right eye. The tuatara was premedicated with medetomidine (0.06 mg/kg) and morphine (1 mg/kg). Intravenous alfaxalone (5 mg/kg) was administered to facilitate intubation. Maintenance anesthesia was achieved using 1–2% sevoflurane. Perioperative support included intraosseous 0.45% saline with 2% dextrose (combined 50% each) at 10 ml/kg/h and thermal support via a forced-air blanket. Transpalpebral enucleation of the right eye was performed and the excised tissue submitted for histopathologic evaluation. Postoperative analgesia was provided using morphine (1 ...

Active Warming Study

We're impressed by the original research studies published in AJN because of their rigor, relevance, and readability. We were especially interested in “The Effects of Active Warming on Patient Temperature and Pain After Total Knee Arthroplasty” (May) because of the nurse's key role in maintaining postoperative normothermia and because of our own recent study in this area1 and our study (in process) about optimal blanket-warming cabinet temperatures. The authors state that the temperature of the blanket-warming cupboard wasn't monitored. We wonder, however, at what temperature the cupboard was set. Low cupboard settings (<150°F) produce lukewarm blankets and lower skin temperatures and lower ratings of thermal comfort compared with higher cupboard settings.2-3 We are pleased that the authors measured “thermal comfort,” because little research has been done on this important variable, and agree with the belief that thermal comfort is “integral to a patient's perception of well-being,” as stated in the article. Based on our own recent study of perioperative hypothermia,1 we caution against using the patient's thermal comfort rating as predictive of core temperature. In our study, we asked patients on arrival to the postanesthesia care unit whether they felt “too hot,” “too cold,” or “just right.” We found that the patient's thermal comfort response did not accurately reflect hypothermia as measured by core (bladder) temperature. Elizabeth H. Winslow, PhD, RN, FAAN Patricia A. Kelly, DNP, APRN, CNS, AOCN Dallas Authors Ember E. Benson, Diana E. McMillan, and Bill Ong respond: The readers are correct in noting that the warming cupboard temperature wasn't monitored. We don't know at what temperature the cupboards were set, because various models within the research facility were used, some of which didn't have an indicator displaying the set temperature or the actual temperature. Temperature variations were likely to occur because of real clinical factors, such as the addition of room-temperature blankets, the door opening, and the length of time before the blanket was applied to the patient. We weren't attempting to predict patients' core temperature using their response to thermal comfort. Rather, we assessed for hypothermia using oral temperature readings, and we measured how satisfied patients were with the thermal comfort provided by the warming methods during the perioperative period and whether this affected their pain. A previous study found that the application of warmth (via forced air blankets) provides patients with a positive feeling of comfort and reduced anxiety.1 Furthermore, some research suggests a link between anxiety and pain2; providing “anxiety reducing strategies,”3 such as warmth, may ultimately affect postoperative pain. We are encouraged that perioperative hypothermia is garnering greater interest, as we believe the subject is of critical importance and worthy of more study.

Avoiding Unintentional Hypothermia During Prosthetic Joint Replacement Surgery

Fig 1. Efficacy of Solution C for disinfection of hospital equipment. Background/Objectives: Hypothermia during the intraoperative period is associated with an increased risk of developing a surgical site infection. Despite using both a forced warm air jacket preoperatively and blanket during surgery, 36% of prosthetic joint replacement patients did not achieve normothermia during the intraoperative period. Due to the surgeon's concern that the forced air motorwould increase room contaminants, the forced air blanket was not turned on until the patient's skin preparation and draping was accomplished, often leading to unintentional hypothermia. Beginning in September 2011, an underbody disposable waterbased warming pad was added to the operating room (OR) table to be used in conjunction with the forced air modalities. Objectives: The objective of this study was to determine if using an underbody warming device, in addition to the forced warm air modalities would increase the proportion of patients achieving and maintaining normothermia during surgery. Methods: From May to September 2010, the baseline period, intraoperative temperatures were obtained from anesthesia records of 50 patients who underwent joint replacement surgery. The underbody disposable water-based warming pad was implemented for joint replacement surgeries in September 2011. From September 2011 to January 2012, the post intervention period, anesthesia records of 56 patients were reviewed to determine the first and last intraoperative temperatures, as well as the highest and lowest temperature. Temperatures were taken using either a bladder probe or an esophageal probe. Results: During the baseline period 13/50 (26%) of patients were normothermic the entire time they were in the OR, as compared to 29/56 (52%) of patients during the post intervention period (p1⁄40.0067). Thirty-six percent (18/50) of the patients were hypothermic for the duration of the surgical procedure during the baseline period, while there were only 12% (7/56) in the post intervention period (p1⁄40.0044). When comparing the last temperature taken in the operating room; 25/50 (50%) of the patients were normothermic in the baseline period, but 46/56 (82%) were normothermic in the post intervention period (p1⁄40.0004). Conclusions: Conclusions: Using the underbody disposable water based warming pad together with preoperative and intraoperative forced warm air warming modalities increased and maintained patients' body temperature throughout the intraoperative period. These results have supported continued utilization of the underbody warming pad. The adoption of this new warming system contributes to collaborative efforts to reduce postoperative infections in prosthetic joint replacement patients.

Does the covering of children during induction of anesthesia have an effect on body temperature at the end of surgery?

Study ObjectivesTo determine whether the covering of healthy children during anesthetic induction reduces hypothermia at the end of minor surgeries. DesignRandomized, single-blinded, prospective study. SettingOperating room and postoperative recovery area of a university-affiliated hospital. Patients50 ASA physical status 1 patients, aged 6 months to 3.5 years, scheduled for simple urological surgeries. InterventionsSubjects were randomly assigned to one of two groups: covered or uncovered. Children in the covered group (Group C) were actively warmed on arrival in the operating room (OR) using cotton blankets and a warm forced-air blanket set at 43°C. Children in the uncovered group (Group U) remained uncovered during the induction of general anesthesia. Children in both groups were actively warmed following placement of surgical drapes. MeasurementsTemperature (in Celsius) during the study procedure was recorded for each patient. Main ResultsMean core body temperature at the end of induction did not differ in the two groups, 36.4°C in Group C and 36.6°C in Group U. Mean core body temperature at the end of surgery did not differ between the two groups: 36.9°C in Group C and 37.0°C in Group U. ConclusionLeaving healthy children uncovered during induction of general anesthesia does not have a clinically significant effect on core temperature at the end of induction or of surgery.

Uso da manta térmica na prevenção da hipotermia intraoperatória

Hypothermia is a life-threatening event during the perioperative period. No consensus has been reached about the best active warming approach for such cases. Furthermore there is no consensus on the most appropriate time to warm a hypothermic patient. This study aimed to assess the efficacy of a forced-air blanket to warm patients at 38 degrees C before and during surgery. Following utilization of the forced-air blanket, adverse effects were evaluated. Patients submitted to orthopedic surgeries were divided into four groups of 15 patients. In the control group (Gcont), patients were not warmed with a forced-air blanket. In the preoperative group (Gpre), intraoperative group (Gintra), and total group (Gtotal), patients were warmed at 38 degrees C, during 30 minutes before anesthetic induction, after anesthetic induction up to 120 minutes and before and after the induction, respectively. Parameters evaluated were central (tympanic) temperature, peripheral (skin) temperature, operating room temperature, variations in the hemodynamic conditions and warming-induced adverse effects. Only Gtotal did not show significant variation in central temperature. Central temperatures of Gtotal patients were significantly higher (p <0.05) than those of other groups at 60 and 120 min after induction. In Gcont, Gpre and Gintra, patients were hypothermic at 60 min. The forced-air blanket is effective to prevent intraoperative hypothermia when applied for a period ranging from 30 min before anesthetic induction to 120 min after anesthetic induction. In the conditions of this study, adverse effects were not observed.

Effect of forced-air heaters on perfusion and temperature distribution during and after open-heart surgery

After cardiopulmonary bypass, patients often show redistribution hypothermia, also called afterdrop. Forced-air blankets help to reduce afterdrop. This study explores the effect of forced-air blankets on temperature distribution and peripheral perfusion. The blood perfusion data is used to explain the observed temperature effects and the reduction of the afterdrop. Fifteen patients were enrolled in a randomised study. In the test group (n=8), forced-air warmers were used. In the control group (n=7), only passive insulation was used. Core and skin temperatures and thigh temperatures at 0, 8, 18 and 38 mm depth were measured. Laser Doppler flowmetry (LDF) was used to record skin perfusion from the big toe. Blood flow through the femoral artery was determined with ultrasound. Afterdrop in the test group was smaller than in the control group (1.2+/-0.2 degrees C vs 1.8+/-0.7 degrees C: P=0.04) whilst no significant difference in mean tissue thigh temperature was found between the groups. Local skin temperature was 2.5-3.0 degrees C higher when using forced-air heaters. However, skin perfusion was unaffected. Ultrasound measurements revealed that leg blood flow during the first hours after surgery was reduced to approximately 70% of pre- and peri-operative values. Forced-air blankets reduce afterdrop. However, they do not lead to clinical relevant changes in deep thigh temperature. LDF measurements show that forced-air heating does not improve toe perfusion. The extra heat especially favours core temperature. This is underlined by the decrease in postoperative leg blood flow, suggesting that the majority of the warmed blood leaving the heart flows to core organs and not to the periphery.

Convection heating in pediatric general surgery – a comparison of warming alternatives in a mannequin study

Numerous methods of patient warming are used to prevent intraoperative hypothermia in children. Commercially available forced air warming blankets are effective, but are single-use items. We tested a custom-designed heat dissipation unit (HDU) against one such commercially available blanket. Air temperatures at various points around a mannequin under simulated operating conditions were recorded using thermistors and thermal imaging. The only variable changed was the heating method: a forced air blanket or a customized HDU with two draping techniques - cotton drapes with and without a plastic 'undersheet'. The three methods produced similar temperature increases and plateaux across the 11 thermistor points measured. There were no significant differences between temperatures at 1 h. A plastic sheet did not appear to enhance the effectiveness of the HDU in this study. Thermal imaging photography suggested more uniform heating of the mannequin with the HDU arrangements. The custom-built HDU compares favorably in our mannequin study with a Bair Hugger forced air warming blanket. As it is reusable, it offers considerable potential savings.

The effect of skin surface warming during anesthesia preparation on preventing redistribution hypothermia in the early operative period of off-pump coronary artery bypass surgery

Redistribution hypothermia adversely affects hemodynamics and postoperative recovery in patients undergoing cardiac surgery. In off-pump coronary bypass surgery (OPCAB), maintaining the temperature is important because warming by cardiopulmonary bypass is omitted. Pre-warming studies reported earlier showing pre-warming as an effective means of preventing redistribution hypothermia was time consuming since it required at least 1-2h to pre-warm the patients before the surgery. Because pre-warming for such a long time is impractical in clinical practice, this study evaluated the efficacy of active warming during the preanesthetic period for the prevention of redistribution hypothermia in the early operative period of OPCAB. After gaining the approval of Institutional Review Board and informed consent from the patients, 40 patients undergoing OPCAB were divided into control and pre-warming groups. The patients in control group (n=20) were managed with warm mattresses and cotton blankets, whereas patients in pre-warming group (n=20) were actively warmed with a forced-air warming device before the induction of anesthesia. Hemodynamic variables and temperature were recorded before anesthesia (Tpre) and at 30 min intervals after anesthesia for 90 min (T30, T60, and T90). Active warming duration was 49.7+/-9.9 min. There were no statistically significant differences in skin temperature, core temperature and hemodynamic variables between the two groups at preinduction period except for mean arterial pressure and central venous pressure. The core temperature at T30, T60, and T90 was statistically higher in pre-warming group than that in control group. Core temperature of six (30%) and seven patients (35%) in control group was reduced below 35 degrees C at T60 and T90, respectively, whereas core temperature of only one patient (5%) in pre-warming group was reduced below 35 degrees C at T90 (P=0.02). Active warming using forced air blanket before the induction of anesthesia reduced the incidence and degree of redistribution hypothermia in patients undergoing OPCAB. It is a simple method with reasonable cost, which does not delay the induction of anesthesia nor the surgery.

Mild hypothermia, blood loss and complications in elective spinal surgery

Background context Spinal surgery carries risks of incidental spinal cord and nerve root injury. Neuroprotection, to minimize the extent of such injuries, is desirable. However, no neuroprotective strategies have been conclusively validated in nonvascular spinal surgery. Mild hypothermia resulting from general anesthesia is a readily achievable potential neuroprotective strategy. Mild hypothermia, however, has been associated with wound infection, increased operative blood loss and other complications. No previous studies have specifically evaluated whether mild hypothermia is associated with an increased risk of these complications in elective spinal surgery. Purpose We investigated the association between incidental mild hypothermia, perioperative complications and operative blood loss. Study design/setting This is a retrospective study employing cohort analysis, rank analysis and single and multivariate linear regression. The setting was the Veterans Administration Medical Center, a teaching hospital of the University of Miami. Patient sample Data on a total of 70 adult veterans aged 23 to 81 years undergoing complex spinal procedures in which passive cooling was employed during surgical decompression. Outcome measures The variables measured were temperature, blood loss, mean arterial pressure (MAP) and duration of anesthesia. The outcome measured was the presence or absence of complications. Methods After 70 patients had been acquired, regression and rank analyses were performed to test for a link between mild hypothermia and blood loss. In addition, two cohorts, patients who experienced complications, and those who did not experience complications in the perioperative period, were compared for several variables including three measures of exposure to hypothermia. Surgical procedures included 60 cervical, 1 occipitocervical, 1 cervicothoracic, 7 thoracic and 1 thoracolumbar procedure. Hypothermia followed induction of anesthesia; esophageal or bladder temperature was monitored. Cooling was passive; warming utilized a forced air blanket. Temperature data from anesthetic records was used to derive mean intraoperative temperature, nadir intraoperative temperature and the rates of cooling and rewarming. The time course of hypothermia, the overall fluctuation in core temperature and the quantity of subbaseline temperature were determined. Medical and surgical complications were included. Two patients with complications considered irrelevant to hypothermia were removed from further analysis. Patients with and without complications were compared as cohorts for differences in mean values of age, comorbid risk factors, intraoperative MAP, intraoperative blood loss, anesthetic duration and temperature-related measures. Relationships between blood loss, anesthesia duration and temperature parameters were assessed in rank and regression analyses. Results Patients with complications (n = 12) had longer mean anesthetic durations (p = .0001) and larger mean surgical blood losses (p = .001) than patients without complications (n = 56). Neither mean nor nadir intraoperative hypothermic temperatures were statistically associated with complications. However, large hypothermic integrals (p = .04) and the total quantity of recorded temperature fluctuation (p = .01) were both associated with complications. Comorbid risk factors, MAP and age were not statistically linked to complications. Finally, no relationship between any of the temperature measures and increased blood loss was found. Conclusion Operative blood loss was not linked to any index of the patient's temperature. Longer anesthesia durations were linked to complications and increased blood loss. Regarding mild hypothermia, neither mean nor nadir hypothermic temperatures were linked to complications, but the estimated total quantity of subbaseline temperature was linked, as was total fluctuation in temperature. Lengthy exposure to mild hypothermia appeared to be associated with wound infections. The use of mild hypothermia as a potential neuroprotective strategy during spinal surgery appears to be reasonably safe, but to avoid complications, the duration of hypothermic exposure should be minimized.

A Comparative Study of Three Warming Interventions to Determine the Most Effective in Maintaining Perioperative Normothermia

A Comparative Study of Three Warming Interventions to Determine the Most Effective in Maintaining Perioperative Normothermia

Complete myocardial revascularization on the beating heart with epicardial stabilization: Anesthetic considerations

Objective: To describe an anesthetic management protocol for patients undergoing cardiac surgery with multiple coronary artery bypass grafts without cardiopulmonary bypass (off-pump CABG surgery) by median sternotomy with mechanical stabilization. Design: Retrospective nonrandomized analysis. Setting: Tertiary care hospital. Participants: Sixty-six consecutive patients on whom off-pump CABG surgery by median sternotomy was attempted. Interventions: Anesthesia was induced with a combination of etomidate and fentanyl; pancuronium bromide was given for muscle relaxation; and anesthesia was maintained with isoflurane, desflurane, or sevoflurane in 100% oxygen. Maintenance of normothermia was attempted by keeping the room temperature at 70°F, warming all fluids to 41°C, and using 2.5 L/min of fresh gas flows and a heat and humidity exchanger. When available, a convective forced-air blanket was used to cover patients' head and shoulders. Patients who were not slated for revascularization of the circumflex vessels and who had good ventricular function received central venous pressure monitoring (26%); all other patients received a pulmonary artery catheter. Measurements and Main Results: Of the 66 patients, 36% required an epinephrine infusion at a mean rate of 1.45 ± 2.05 μg/min intraoperatively to maintain hemodynamic stability; 25% required inotropic support for <12 hours in the intensive care unit. Conclusion: Institution of systematic hemodynamic management was associated with the successful completion of the surgical procedure in 61 patients (92%). Only 5 patients required conversion to regular CABG surgery with cardiopulmonary bypass. Copyright © 2000 by W.B. Saunders Company

Normothermia is protective during infrarenal aortic surgery

Purpose: Mild hypothermia has been suggested to be protective against tissue ischemia during aortic operations. However, recent studies have documented detrimental cardiac effects of hypothermia during a variety of operative procedures. The influence of different warming methods and the impact of hypothermia during standard aortic procedures was assessed. Methods: One hundred patients who underwent repair of infrarenal aortic aneurysms or aortoiliac occlusive disease were prospectively randomized into 2 groups, receiving either a circulating water mattress or a forced air warming blanket. Adjuvant warming methods were standardized. The day before surgery, 48-hour Holter monitors were applied and interpreted by a cardiologist blinded to the treatment. Randomization resulted in equivalent groups with regard to patient history, indications for surgery, body mass index, length of surgery, and fluid requirements. Results: Core temperatures were significantly warmer during surgery (36.3°C ± 0.7°C vs 35.4 ± 0.8°C) and after surgery (36.4°C ± 0.7°C vs 35.6°C ± 0.9°C) in patients with forced air warming ( P < .001). The circulating water mattress group had significantly more metabolic acidosis perioperatively ( P = .03). Postoperative length of stay, cardiac complications, and death rates were not significantly different. Subgroup analysis of 83 aneurysm patients comparing normothermia with hypothermia (temperature less than 36°C) on arrival to the recovery room identified decreased cardiac output ( P = .02), thrombocytopenia ( P = .02), elevated prothrombin time ( P = .04), and inferior Acute Physiology and Chronic Health Evaluation (APACHE) II scores ( P < .001) in the hypothermic group. Holter analysis revealed more sinus tachycardia (ST) segment changes and ventricular tachycardia in hypothermic aneurysm patients ( P = .05). Conclusion: Patients treated with forced air blankets had significantly less metabolic acidosis and were kept significantly warmer than those treated with circulating water mattresses. Patients with aneurysms that were kept normothermic had a significantly improved clinical profile, with fewer cardiac events on the Holter recordings. We therefore conclude that (1) normothermia is protective for infrarenal aortic surgical patients; and (2) forced air warming blankets provide improved temperature maintenance compared with circulating water mattresses. (J Vasc Surg 1998;28:984-94.)

Temperature monitoring.

Central temperature is usually tightly regulated in human beings. Anesthesia alters the normal thermoregulatory controls of the body. Intraoperatively, mild degrees of hypothermia may provide some cerebral protection. However, the risk of organ dysfunction and shivering require that the anesthesiologist be prepared to treat severe hypothermia. Appropriate measures such as warning the operating room and using forced air blankets can prevent both intraoperative hypothermia and postoperative shivering. The use of temperature measurement is not limited to the operative and immediate recovery periods. Anesthesiologists practicing in intensive care units and in pain clinics use temperature monitoring as a diagnostic tool in a variety of situations.