Bair Hugger Research Articles

Prevention of Perioperative Hypothermia: A Prospective, Randomized, Controlled Trial of Bair Hugger Versus Inditherm in Patients Undergoing Elective Arthroscopic Shoulder Surgery

To determine if a clinically significant difference in the core body temperature (CBT) exists between the Bair Hugger (BH) and Inditherm (IT) warming devices in patients undergoing arthroscopic shoulder surgery. This was a parallel, 2-treatment, prospective, randomized, controlled trial conducted in patients undergoing elective arthroscopic shoulder surgery in the beach-chair position using room-temperature irrigation fluid. The BH was used as the indicative forced-air warming device, whereas the IT served as the indicative resistive heating system. By use of a minimal clinically significant difference of 0.6°C and standard deviation of 0.6°C, a power analysis showed that a sample size of 90 patients (45 per group) would be required. Patients fulfilling the inclusion criteria were recruited from the clinics of the senior authors. Anesthetic and surgical protocols were standardized. The intraoperative CBT was recorded every 5 minutes using a nasopharyngeal thermistor probe. Demographic data as well as the volume of irrigation fluid used were also noted. A steady decline in the CBT was observed in both groups up to 30 minutes after induction of anesthesia. Beyond 30 minutes, the BH group showed a gradual increase in temperature whereas it continued to decline in the IT group. A statistically significant difference in the CBT was observed from 60 minutes onward (P= .025). This difference continued to increase up to 90 minutes (P < .001). At no time was a rise in the CBT observed in the IT group. At completion of the study and surgical procedure, 13 of 47 patients in the BH group and 32 of 44 patients in the IT group had hypothermia (P= .0002). The CBT was statistically significantly better with the use of the BH compared with the IT mattress. However, the differences in the CBT did not reach the level of clinical significance of 0.6°C. Far fewer patients in the BH group had hypothermia at the end of surgery. Therefore, this study supports the use of the BH in elective arthroscopic shoulder surgery for the prevention of hypothermia. Level I.

1813 A Killer in the Dark: The Black Esophagus

INTRODUCTION: Acute esophageal necrosis, also known as “black esophagus” is a rare condition of unclear etiology. Only 88 patients were diagnosed over a period of 40 years. It is diagnosed by endoscopy showing darkly pigmented necrotic esophageal mucosa. Prognosis is poor, with a mortality rate of 31.8-50%. We report a case of this condition in an elderly woman who presented with hematemesis and sepsis. CASE DESCRIPTION/METHODS: A woman aged 72 presented after a fall with head strike without loss of consciousness. CT head was unremarkable. That evening, she had an episode of coffee-ground emesis associated with hypotension, tachycardia, and worsening mental status. Hemoglobin was 6.1, raising suspicion of GI bleed. However, she developed leukocytosis without abdominal pain or melena, suggesting septic shock. She received fluids and antibiotics with no improvement. CTPA showed bilateral pulmonary embolism. Anticoagulation was held given concern for GI bleed. Later a massive transfusion protocol was activated when hemoglobin dropped to 4.8; 400 cc of blood was aspirated from the stomach. She received 3U pRBCs, 1U FFP, 1U platelets, 500 cc albumin and vasopressors with improvement of hemoglobin to 11. She then became increasingly acidotic and hypothermic for which a bair hugger was placed. An EGD revealed a severely inflamed esophagus with black material extending from the mid esophagus to the gastroesophageal junction, consistent with esophageal necrosis, the likely source of her GI bleed. The patient stopped following commands, moving extremities or responding to pain. Despite maximal measures, the patient’s hemodynamic instability worsened and she died. DISCUSSION: Acute necrotizing esophagitis is a fatal condition that commonly presents with hematemesis or melena. It is associated with multiple factors including diabetes, hemodynamic instability, trauma, hypercoagulable state, gastric volvulus, and some infections. While the pathophysiology is not well known, it is hypothesized that the condition results from an ischemic insult. Esophageal perforation, stricture, infection and death are the main complications. As with our patient, the most likely cause of death are underlying comorbidities such as infections, sepsis, hypovolemic shock or pulmonary embolism, while underlying esophageal disease as the cause of death have been reported in only less than 10% of patients. Elderly patients with comorbidities like diabetes and vascular disease, presenting with upper GI bleed must always get an upper GI endoscopy.

Incidence of Lumbar Plexopathy while Utilizing Mechanomyography for Transpsoas Lateral Lumbar Interbody Fusion

Introduction Previous studies utilizing electromyography (EMG) have reported that the incidence of thigh complications during transpsoas lateral lumbar interbody fusion (LLIF) ranged from 0.7 to 75%. The reliability of EMG has been questioned because of false-positives, false-negatives, and electrical interference from common operating-room equipment. Mechanomyography is a new neuromonitoring technique that functions by measuring the mechanical activity in muscles, or “twitch,” noninvasively using surface-mounted accelerometers on the skin following nerve stimulation and muscle contraction. MMG may provide an alternative to EMG for neuromonitoring. In this study, we evaluated the incidence of thigh complications during transpsoas LLIF utilizing MMG to monitor the lumbar plexus. Materials and Methods A retrospective review of prospectively collected data of four different surgeons at four separate institutions was performed. A total of 85 consecutive patients, with 175 instrumented levels, were included who underwent transpsoas LLIF surgery (L1–L5) during a 1-year period. Immediate postoperative and routine follow-up clinical examinations at 3, 6, and 12 months were obtained. Results The rate of all ipsilateral thigh symptoms (pain, numbness, and weakness) was 21.2% (18/85). Eight patients (9.4%) had iliopsoas or quadriceps weakness (3/5 motor strength). Overall, 10 patients (11.8%) had anterior thigh pain and/or numbness. Most patients with postoperative thigh symptoms (16/18) had 3 or 4 level procedures performed for adult degenerative scoliosis (ADS) and included the L45 level. All thigh symptoms resolved within 3 months. Conclusion MMG is a safe and effective alternative to EMG for nerve mapping during transpsoas LLIF surgery and overcomes deficiencies related to the high rates of false-positives and false-negatives inherent to EMG. In addition, unlike EMG, MMG is not affected by electrical artifact seen with common operating-room equipment such as the bovie electrocautery and bair hugger body warmer. With the use of MMG, the rate of ipsilateral thigh symptoms was 21.2%, which is consistent with currently reported rates for transpsoas LLIF procedures utilizing EMG. In our study, most thigh symptoms occurred in patients with multilevel LLIF procedures performed and direct trauma to the psoas may have contributed to our results and the actual rate of nerve-related thigh symptoms might be lower. All symptomatic patients had L45 included in their construct. MMG is a safe alternative to EMG to monitor the lumbar plexus when performing transpsoas LLIF.

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Introduction: Hypothermia remains a challenging clinical problem in US. Causes of hypothermia include cold exposure, medical condition such as hypothyroidism, adrenal insufficiency, sepsis, toxin, and medications. Hypothermia is also complicated by other comorbidities such as arrhythmia, lactic acidosis, coagulopathy, infection, and rhabdomyolysis which are life threatening. This can explain high mortality rate of this condition (40%). We present a case of hypothermia as a presentation of hypothyroidism. 74-year-old Hispanic female was brought to the ER as Jane Doe after she was found unresponsive on the street. At ER, she was alert but confused. Medical history was not available at that time. On examination, there were multiple abrasions on extremities. Vital signs were as follows: rectal temerature 28.1 c, blood pressure 122/67 mmHg, heart rate 78/min, respiration 14/min, and oxygen saturation 100% on room air. Her examination was notable for dry mucous membranes, very cold and moist skin, irregular heart rhythm, pupils 3 mm sluggishly reacted to light, and her GCS score was 10. EKG demonstrated atrial fibrillation rate of 93/min with prominent Osborne waves. Active rewarming process was initiated immediately by warm IVF, Bair hugger, bladder irrigation with warm saline, and warmed humidified air. Thirty minutes later, she was more responsive but her blood pressure dropped to 88/52 mmHg and temperature was 30 c. EKG was same as previous. She receives 3 L of NS as bolus and was started on vasopressor. Empiric antibiotics were given. She was then monitored closely in MICU. Laboratory revealed the following results: pH 7.28, pCO2 59, pO2 136, bicarbonate 29, sodium 139, potassium 2.7, creatinine 1.02, lactic 4.5, troponin I 0.05, CPK 869, urine myoglobin < 1, d-dimer 5.41, WBC 14.5, TSH 14.378 mcunit(high), free T4 0.9 ng/dL(normal), cortisol 40, urine drug screen - negative, ammonia 31. CT brain and CT chest was negative for any intracranial lesion and pulmonary embolism. Cardiology was consulted for elevated troponin and possible myocardial infarction. Echocardiography revealed no wall motion abnormality. Elevated troponin was likely reflect rhabdomyolysis. Endocrinology thought that myxedema coma was less likely and recommended to start patient on levothyroxine 50 mcg daily without loading dose for treatment of hypothyroidism. Later on that day, Her son was successfully contacted by hospital and gave information that patient has hypertension, dyslipidemia and worsened memory loss in the past 2 months. After 6 hours of rewarming process, the core temperature normalized (37.1 c). Her EKG converted to normal sinus rhythm. During the hospital course, her CPK trending up to 5,324 then trending down with aggressive IV fluid while her kidney function was maintain normal. Neurological investigations were done reveal normal MRI brain, normal EEG, normal level of vitamin B12. Neurologist confirmed diagnosis of dementia likely secondary to hypothyroidism. She was transferred to general floor at 48 hours. Her consciousness improved back to baseline at 72 hours and was discharged on the sixth day in good condition on levothyroxine 50 mcg oral daily. There are various causes of hypothermia. In this case, it was possible to assume that this patient who was hospitalized with hypothermia and altered mental status suffers from hypothyroidism. The acute decompensation of hypothyroidism is typically precipitated by environment cold exposure, infection, medication or withdrawal. In patients suspected to have this condition, the passive rewarming is preferred compared to active rewarming which carries risk of vasodilation and hypotension which happened in our patient. Our patient also had sign of hypothyroidism (dementia) preceding this incidence. This should raise importance of checking TSH as a routine work up in dementia for early diagnosis and treatment to prevent patient from myxedema coma which has high mortality rate.

Classic EKG Changes of Hypothermia

A 51-year-old female was found lying in a wet damp area near a rural Wisconsin roadside in early spring. The patient was unresponsive and multiple empty medication bottles were found near her body. At the time of admission to the emergency department, her temperature was 80.4°F (26.8°C) with her blood pressure at 80/50 mm Hg. She was intubated for airway protection. The empty medication bottles found included prescriptions for citalopram, aripiprazole, ziprasidone, trazodone, clonazepam, oxycodone, levothyroxine and lansoprazole. She had multiple electrolyte abnormalities (potassium 2.5 mmol/L, magnesium 1.6 mg/dL, phosphate 1.3 mg/dL, and ionized calcium 4.2 mg/dL). Her EKG (figure 1 ▶) showed evidence of hypothermia with prolonged QRS and Osborne waves (arrows in figure 1 ▶), new onset atrial fibrillation, and prolonged QT (QT/QTc 740/688). Members of the emergency department staff were able to rewarm her using warm saline, radiant heat, and warm air (Bair hugger). Her body temperature slowly increased to 88.3°F (31.3°C) within the next 4 hours with significant reversal of her EKG changes (figure 2 ▶), including reverting back to sinus rhythm, normalization of QRS waves (88 milliseconds) with resolution of Osborne waves and improvement in QT (QT/QTc 504/577). By 12 hours post-admission, her temperature was raised to 99°F (37.2°C). Figure 1. Initial EKG with classic findings of hypoxia at body temperature of 80.4°F. Figure 2. Repeat EKG in next 4 hours with significant reversal of her EKG changes at body temperature of 88.3°F. The patient’s cardiac enzymes remained negative. Her comprehensive urine drug screen was positive for oxycodone, oxymorphone, trazodone, lidocaine, and citalopram. She was extubated in less than 24 hours and was discharged from hospital in 3 days. The incident was thought to be an attempted suicide, which resulted in her exposure to cold weather conditions for 24 hours. J waves (also called Osborne waves) are pathognomonic for hypothermia when present.1 These look like “delta” or “camel’s hump” waves after regular QRS complex.1 J waves or Osborne waves appear secondary to an exaggerated outward potassium current leading to repolarization abnormality.2 These waves are detectable in 80% of the patients when core body temperature is lower than 30°C.3 J waves are seen in lead II and precordial leads V2-V6.1 Similar findings can be seen in patients with hypercalcemia, Brugada syndrome, and early repolarization.1 Our patient had significant hypokalemia and it could have contributed to the prolonged QRS. It should be noted, however, that the plasma potassium levels do not generally correspond to the electrocardiographic changes of hypokalemia.4 J waves are not prognostic indicators when they are present, unlike atrial fibrillation, which incurs survival disadvantage.5 Fatal ventricular fibrillation or asystole can occur when core body temperature is below 28°C.1

Post-operative warming in the cardiac patient: Evaluation of the bair hugger® convective warming system

Post-operative warming in the cardiac patient: Evaluation of the bair hugger® convective warming system

Evaluation of the efficacy of a forced-air warmer (bair hugger) during spinal surgery in children

To evaluate the efficacy of a forced-air warmer during spinal surgery for correction of scoliosis in children. Prospective randomized study (group allocation based on the availability of the warming device). Children's teaching hospital. 51 ASA physical status I and II children (mean age, 15 years; mean weight, 45 kg) scheduled for posterior spinal fusion with general anesthesia. Study group (warmed; n = 26)--legs covered with the forced-air warmer (Bair Hugger, Augustine Medical, Inc., Eden Prairie, MN) after installation of the patient in prone position--versus control group (n = 25)--400W heat lamp placed over the head during surgery as is usually done in our institution. Rectal temperature was taken every 15 minutes during surgery and during the first 2 hours in the recovery room. Time required for the wake-up test, time to extubation, and blood loss also were noted. Temperature profiles were very different in the 2 groups. In the control group, rectal temperature decreased during the first 180 minutes to a minimum of 34.8 degrees C +/- 0.6 degrees C, followed by a slow rewarming phase. In the warmed group, the lowest temperature (35.6 degrees C +/- 0.5 degrees C) was recorded 45 minutes after placement of the forced-air warmer, followed by an effective warming phase. At the end of surgery, temperature was significantly higher in the warmed group than in the control group (36.5 degrees C +/- 0.8 degrees C vs. 35.4 degrees C +/- 0.9 degrees C). However, time required for the wake-up test, time to extubation, and blood loss did not differ between groups. The forced-air warmer (Bair Hugger) is effective during spinal surgery, although only about 20% of body surface area can be covered.

Bair hugger forced-air warming maintains normothermia more effectively than thermo-lite insulation

Study Objective: To compare the ability of forced-air warming and reflective insulation to maintain intraoperative normothermia. Design: Prospective, randomized clinical trial. Setting: Operating rooms of a general hospital. Patients: 20 ASA physical status I and II patients undergoing elective total hip arthroplasty. Interventions: Patients were randomly assigned to be warmed intraoperatively using forced-air or reflective insulation. Inspired gases were conditioned using a heat-and-moisture exchanger in both groups, and infused intravenous fluids were warmed to 37°C. Measurements and Main Results: Distal esophageal (core) temperatures decreased approximately 0.5°C in both groups during the first 45 minutes of anesthesia. Subsequently, core temperatures increased slightly in the patients given forced-air warming. In contrast, core temperatures continued to decrease in patients covered with reflective insulation. After 135 minutes of anesthesia, core temperatures were 36.4 ± 0.6°C (mean ± SD) in the forced-air group but only 35.4 ± 0.6°C in the insulated group ( p < 0.01, unpaired t-test). These data indicate that forced-air warming is superior to reflective insulation. Conclusion: Reflective insulation was unable to maintain intraoperative normothermia during total hip arthroplasty. Active warming, such as that provided by forced air, was required to prevent hypothermia.