Aragona Medical, Inc. - Patient Warming Therapy with Radiant Heat

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Title: Additional Heat with Thermal Ceilings
Author: University Hospital, Uppsala, Sweden
Publication: Unpublished, 8p.

Conclusions:
The graphs in the article show the result of a test group heated with external energy in the form of low-temperature radiant heat - maximum 2000 W - and a control group.
The most significant results are that the muscular activity is clearly reduced which gives a decreased hypermetabolism, This decrease is connected with lowered ventilatory need due to a reduction in the carbon dioxide production and the oxygen consumption.
The higher body temperature also reduces the arterial resistance, resulting in lowered circulatory load and a better tissue perfusion.
Also, the patients spontaneously responded in a positive way, as their environmental comfort increased.
The graph of muscular activity is shown at the bottom of each page as a reference to the other graphs. Note that the peak in many of the graphs is after 11/2 hours.

Title: Early Extubation After Coronary Artery Surgery in Efficiently Rewarmed Patients: A Postoperative Comparison of Opioid Anesthesia Versus Inhalational Anesthesia and Thoracic Epidural Analgesia.
Author: P.-O. Joachimsson, MD, PhD, S.-O. Nyström, MD, PhD, and H. Tydén, MD, PhD. Department of Anesthesiology and Intensive Care, and Thoracic Surgery, Uppsala University Hospital, Uppsala, Sweden.
Publication: Journal of Cardiothoracic Anesthesia, Vol. 3, No 4 (August), 1989. 11 pp.

Abstract:
Twenty-eight patients were studied after uncomplicated aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). In all patients residual hypothermia was effectively treated by the use of extended rewarming during CPB and postoperatively by an external heat source. This treatment almost eliminated postoperative shivering, and it resulted in the lowering of oxygen uptake, carbon dioxide production, and required ventilatory volumes to stable levels where spontaneous breathing could be used safely. The patients were divided into two groups. In Group I (n=12), intraoperative anesthesia was based on an intravenous (IV) opioid (phenoperidine), which caused persistent respiratory depression and made mechanical ventilation necessary for a mean postoperative time period of 10.7 ± 3.8 hours even with the rewarming. In group II (n=16), thoracic epidural analgesia and intraoperative general anesthesia with enflurane were used. In this group, postoperative metabolic and ventilatory requirements were stable and low, finger skin temperature was normalized earlier, systemic vascular resistance was lower, and stroke index was higher. Emergence from anesthesia was uneventful and was achieved early postoperatively in Group II. The patients had good pain relief and were mentally alert. Adequate spontaneous breathing was resumed quickly and endotracheal extubation was performed within the first two postoperative hours (1.6 ± 0.5 hours). No complications or increased morbidity occurred, and no patient needed to be reintubated in Group II.

Title: Effects of a Thermal Ceiling on Postoperative Hypothermia.
Author: S. Henneberg, M.D., A. Eklund, M.D., P.-O. Joachimsson, M.D., H. Stjernström, M.D., L. Wiklund, M.D.,Department of Anaesthesiology, University Hospital, Uppsala, Sweden
Publication: Acta Anaesthesiol Scand 1985: 29: 602-606. 5 p.

Summary:
Postoperative external heating with a thermal ceiling reduced oxygen consumption and shivering significantly in moderate hypothermia. Furthermore, it reduced plasma catecholamine levels. At the same time, the comfort of the patient increased considerably.

Title: Etiology and Control of Postburn Hypermetabolism.
The 1991 Presidential Address to the American Burn Association.
Author: Fred T. Caldwell, Jr., M.D., Department of Surgery, University of Arkansas Medical Center, Little Rock, Arkansas.
Publication: Journal of Burn Care & Rehabilitation Volume 12 Number 5 Sept./Oct. 1991. 17p.

Summary:
An historic overview leads to today's energy and nutritional requirements of patients with burns. First by monitoring the oxygen consumption level to determine their energy needs. Second, the HMR must be minimized by one of two methods. The first involves the establishment of a warm ambient temperature or the provision of supplemental infrared heaters. In either instance, the positive heat load must be regulated by the patients expression of comfort. The second procedure involves use of occlusive dressings with insulative value. In the absence of other complications, patients who are managed by either method can reach stable body weight within the first two weeks after burn injury. Third, wound closure of full-thickness injuries should begin as soon as the patient is hemodynamically stable - usually within the first postburn week.

Title: Heat Loss in Burn Patients
Author: P. Dziewulski, FRCS Registrar, J. A. Clarke, FRCS Consultant, Plastic Surgery and Burns Unit, Queen Mary's University Hospital, Roehampton, London, UK.
Publication: British Journal of Intensive Care March/April 1991. 4 p.

Summary:
Heat loss in burn patients is an important preventable cause of morbidity and mortality. It is intimately linked to the hypermetabolic state of the patient, and reduction of heat loss along with nutritional support, plays a major part in controlling accelerated catabolism until the burn wound is healed. Heat losses are increased during the peri-operative period and strenuous efforts must be made to reduce them, especially in children, The main methods of reducing heat losses in general are to raise the environmental temperature and dress the wound. Other more specific measures must be used when required.

Title: Heating Efficacy of External Heat Sypply During and After Open-Heart Surgery with Hypothermia.
Author: P.-O. Joachimsson, M.D., S.-O. Nyström, M.D., H. Tydén, M.D., Departments of Anaesthesiology and Intensive Care, and of Thoracic Surgery, University Hospital, Uppsala, Sweden
Publication: Acta Anaesthesiol Scand 1987: 31: 73-80. 8 p.

Conclusions:
Postoperative external heat supply was shown to improve heat balance when residual hypothermia was present after surgery. Radiant heat from a low-temperature radiator, a thermal ceiling, was established as a new efficacious method for providing heat, shortening the rewarming, since a reduction of muscular thermogenesis, expressed as decreased shivering, was noted concomitantly. Our results also suggest that the postoperative cutaneous vasoconstriction may be treated by postoperative heat supply. Moreover, the findings support the assumption that intraoperative heat loss may be a cause of the postoperative cutaneous vasoconstriction. Additional beneficial effects of the improved postoperative heat balance may be expected, since the passive rewarming promoted by the thermal ceiling will probably lower oxygen consumption, carbon dioxide production and the required alveolar ventilation needed and the systemic vascular resistance. These assumptions remain to be verified and further studies on these topics are in progress in our department.

Title: Hypothermia and Rewarming After Cardiac Operation
Author: Jill N. Howie, RN, MS, CCRN
Publication: Focus on Critical Care, AACN Volume 18, Number 5, October 1991. 5p.

Abstract:
The use of radiant [heat] not only prevents heat loss, but enhances heat gain. The most recent research indicates that radiant heat enhances convective heat transfer, promotes radiant heat gain, and decreases peripheral vasoconstriction. This method can be extremely beneficial for patients after cardiac surgery who initially maintain high systemic vascular resistance.

Title: Hypothermia in the Elderly
Author: Robert C. Morrison, M.D. Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO
Publication: International Anesthesiology Clinics Vol 26 No 2 Summer 1988. 10 p.

Subchapters:
Means of thermoregulation
Mechanisms of heat loss
Radiant,Conductive,Convective,Evaporative
Surgical and medical risk factors for hypothermia
Physiological consequences of hypothermia
Cardiovascular responses
Respiratory system
Circulatory effects
Neurological effects
Hepatic and metabolic function
Renal function
Neuromuscular function
Identification of hypothermia
Prevention
Recovery from hypothermia
Treatment
References

Excerpt:
"In the elderly patient, physiological trespasses are poorly tolerated and recovery takes longer with greater complications. Our role as anesthesiologists is to preserve intraoperative homeostatis. For temperature regulation, this means taking numerous measures to prevent heat loss. We must even occasionally resort to heating of the operating room and making the surgeon uncomfortable. In no other area of our practice does the potential for confrontation so commonly arise, but it is demanded by patient safety."

Title: Inadvertent Hypothermia: A Real Problem
Author: Richard B. Lilly, Jr., M.D., Associate Attending Anesthesiologist at Hartford Hospital, Hartford, Connecticut 06106
Publication: ASA Refresher Courses in Anesthesiology Vol. 15, Chapter 8. 15 p.

Summary:
A high percentage (60 per cent) of all patients become hypothermic during anesthesia and surgery. The greatest danger of hypothermia is present after emergence as the patient is rewarming. Minimal heat loss (0.3ĄC) can increase oxygen consumption, whereas shivering dramatically increases oxygen consumption (500 per cent) and thus the need for increased cardiac output and ventilation. These adverse sequelae of hypothermia can be prevented by compulsively keeping patients covered, warming ORs when feasible, and using radiant heat lamps and heated humidifiers. Shivering must be treated aggressively in the recovery room, and treatment modalities include paralysis and controlled ventilation, supplemental oxygen, radiant heat sources, and small doses of IV meperidine. Blood gas results should not be "temperature corrected."

Title: Inhibition of Postanesthestic Shivering with Radiant Heat
Author: A. Sharkey, M.B., B.CH., B.A.O., F.F.A.R.C.S., J.M. Lipton, PH.D., M.T. Murphy, M.D., A.H. Giesecke, M.D., Departments of Anesthesiology and Physiology, Southwestern Medical School, University of Texas Health Science Center at Dallas, Texas.
Publication: Anesthesiology Vol. 66, No 2, Feb. 1987. 4 p.

Abstract:
In recent studies of postanesthetic shivering (PAS) in an unoperated, anesthetized, subhuman primate model, acute application of radiant heat to the skin immediately interrupted shivering even though deep body temperature remained low. Rapid changes in shivering as the heat lamp was turned on and off suggested that a similar technique might be useful in the control of PAS in humans. This effect was tested on PAS in obstetric patients in studies described. Positive findings in these experiments led to compare the effect on duration of PAS of constant radiant heat exposure with PAS duration when warm blankets were used.

Title: Metabolic Changes Following Thermal Injury
Author: Gösta S. Arthurson, M.D., Burn Center, University Hospital, Uppsala, Sweden
Publication: World Journal of Surgery 2, 203-214, 1978. 12 p.

Abstract:
Patients with extensive thermal injuries have a tremendous, long-lasting increase in transcutaneous heat loss by increased evaporation, radiation, and convection. Their ability to regulate skin temperature and hear loss is limited, and the core-skin insulation is inadequate. The corresponding posttraumatic metabolic response is a massive catabolic drive revealed as insulin insufficiency and increased release of catecholamines and glucagon. This stimulates lipolysis, proteolysis, substrate flow to the liver, and gluconeogenesis of amino acids. The increased heat production is related to an endogenous reset in metabolic activity and is further influenced by environmental conditions. Extensively burned patients cannot overcome the cold stress to which they are exposed by an increased functional heat insulation or by tolerating decreasing body temperature without reacting with a costly increase in heat production and without shivering. If the bur patients are permitted to control the heat supply from infrared heaters until they feel comfortable and all kinds of external environmental disturbances are eliminated, it is possible to reduce their metabolic rate to the normal value for the actual core temperature. The daily caloric requirements can be estimated and, in patients receiving a combined parenteral-enteral dietary program and infrared heat, weight loss can be entirely avoided. Infrared radiation is a practical and inexpensive way of distributing energy from the environment to the patient, suitable also in disaster situations. The ambient air temperature can be kept comfortable with respect to the patient's airways and to the nursing staff.

Title: Postoperative Ventilatory and Circulatory Effects of Heating After Aortocoronary Bypass Surgery
Postoperative external supply.
Author: P.-O. Joachimsson, M.D., S.-O. Nyström, M.D., H. Tydén, M.D., Departments of Anaesthesiology and Intensive Care, and of Thoracic Surgery, University Hospital, Uppsala, Sweden
Publication: Acta Anaesthesiol Scand 1987: 31: 532-542. 10 p.

Conclusions:
Residual hypothermia is usually present after hypothermic cardiopulmonary bypass. Compared with the findings in an unwarmed control group, postoperative external (mainly radiant) heat supply resulted in earlier rewarming in our treatment group of patients, with the benefits of much less shivering, lower oxygen uptake and lower carbon dioxide production. Thus, the rewarming was converted into a mainly passive process. The required ventilation volumes were reduced to such an extent that the possibility of early extubation is suggested. The heat supply promoted a stable central circulation and seemed to be an efficient causal treatment of postoperative peripheral vasoconstriction.

Title: Postoperative Ventilatory and Circulatory Effects of Heating After Aortocoronary Bypass Surgery.
Extended rewarming during cardiopulmonary bypass and postoperative radiant heat supply.
Author: P.-O. Joachimsson, M.D., S.-O. Nyström, M.D., H. Tydén, M.D., Departments of Anaesthesiology and Intensive Care, and of Thoracic Surgery, University Hospital, Uppsala, Sweden
Publication: Acta Anaesthesiol Scand 1987: 31: 543-549. 7 p.

Conclusions:
Postoperative radiant heat supply considerably improves the postoperative condition after aortocoronary bypass surgery. The addition of extended rewarming during cardiopulmonary bypass, to reach a rectal temperature of at least 36ĄC, required on the average 30 min. longer of CPB, and further reduced the metabolic demands and ventilatory needs. Thus, extended CPB rewarming seems worthwhile even when postoperative radiant heat supply is available. This combined treatment resulted in reduced ventilation volumes, and we consider that with the use of this method postoperative ventilatory support would no longer be necessary if the anaesthetic technique were modified to permit early spontaneous breathing and extubation.

Title: Postoperative Ventilatory and Circulatory Effects of Extended Rewarming During Cardiopulmonary Bypass
Author: P.-O. Joachimsson, M.D., S.-O. Nyström, M.D., PH.D., H. Tydén, M.D., PH.D., Departments of Anaesthesiology and Intensive Care, and of Thoracic Surgery, University Hospital, Uppsala, Sweden
Publication: Canadian Journal of Anaesthesia 1989/36:1. 11 p.

Conclusions:
Extended cardiopulmonary bypass rewarming may reduce the heat deficit usually seen after hypothermic cardiopulmonary bypass. It reduced postoperative shivering. However, the beneficial effects on metabolic and ventilatory requirements seen in some patients were not uniform and were quite unpredictable. In fact, overall comparisons between the entire extended CPB-rewarming group and the control group did not reveal any improvements in metabolic or ventilatory requirements due to the extended rewarming.
It therefore seems inefficient when used alone to improve the postoperative course after cardiac surgery, but it may be of value as a complementary measure if combined, for instance, with postoperative radiant heat supply.

Title: Pre-Induction Skin-Surface Warming Minimizes Initial Intraoperative Hypothermia
Author: Camus Y, Delva E, Sessler D, Lienhart A, Saint-Antoine Hospital, Paris, France and Dpt of Anesthesia, University of California, San Fransisco.
Publication: Anesthesiology, Vol. 79, No. 3A, Sept 1993.

Discussion:
Preoperative skin-surface warming significantly minimizes the initial decrease in core temperature. The rate of decrease in core temperature after the induction of anesthesia depends on the peripheral temperature before the induction. Preoperative skin-surface warming may be useful to prevent core hypothermia in short surgical procedures.

Title: Rapid Radiant Rewarming in Hypothermia
Author: M. English, FRCA, A. Scott, FRCA, R. Brown, FRCP, J. Hinchey, FRCP. Depts. Of Anaesthesia and Surgery, McGill University, Montreal, Canada.
Publication: Anesthesiology, Vol. 83, No 3A, P A260, Sept. 1995.

We measured the effect of a 2 m², ceiling-suspended Radiant Ceiling (RC) [Aragona, NJ] on the rate of rewarming in 12 patients hypothermic after aorto-coronary bypass (ACBP). With ethical approval and random selection, 6 patients were rewarmed with the RC suspended 30 cm above the sternal angle, and 6 with the RC at 60 cm: all were covered with a single cotton sheet. Informed consent from the patients was not required becauce the rewarming protocol had been established by the ICU staff independently of our study and had been normal clinical practice for several months. Temperatures were measured with the appropriate Mallinckrodt thermocouples and recorded every minute. Core temperature (TC) was measured in the aural canal; mean skin temperature (TSK) was derived from Ramanathan's 4 skin sites [1] and mean body temperature (TMB) was calculated as 0.66TC + 0.34TSK [2] (at normothermia TMB = 36°C). There were no significant differences between the groups in age (59.5 ± 2.9 yrs at 30 cm vs. 58.2 ± 10.4 yrs at 60 cm); weight (69.8 ± 14.8 kg vs. 77.8 ± 11.6 kg); body surface area (1.9 ± 0.1m2 vs. 1.9 ± 0.2 m2); surgical duration (4.8 ± 0.8 hrs vs. 4.6 ± 1.4 hrs); air temperature (22.3 ± 0.7°C vs. 21.8 ± 0.5 °C); ICU admission TC (34.5 ± 1°C vs. 34.6 ± 0.8 °C); admission TSK (31 ± 1 °C vs. 31 ± 0.6 °C); nor admission TMB (33.3 ± 1 °C vs. 33.4 ± 0.7 °C).
After a control period of 15 minutes the rewarming protocol was started and continued until TMB reached 37 °C, 1 °C above normothermia. The rewarming rate was determined by least squares linear regression analysis of time versus TMB at 10 minute intervals. The hourly rates of increase in TMB were:
- at 30 cm, 2.2 ± 0.1 °C/hr; n = 77; r = 0.9781.
- at 60 cm, 1.8 ± 0.1 °C/hr; n = 83; r = 0.9734.
The rewarming times to normothermia (TMB = 36 °C) were 74 ± 3 minutes at 30 cm, and 90 ± 5 minutes at 60 cm. These temperature increases are equivalent to a rate of heat gain of 148 Watt (W) at 30 cm and 135 W at 60 cm: and, in a separate study, we confirmed these figures by directly measuring heat gain with Heat Flux Transducers in a model simulating the human torso.
During this rapid rewarming there were no deleterious changes in cardiovascular paramaters which required either a modification of the rewarming protocol, or any additional or unusual cardiovascular support. No patient sustained a thermal injury.
The heat gain with current conventional rewarming methods, convective air warmers and hot-water mattresses, is 58-94 W. At 135-148 W the RC offers higher heat gain, faster rewarming, and, because it is a "stand-off" system, allows easy access to the patient without interrupting rewarming.
Early extubation by 4 hours after admission is the ICU's proposed management policy for ACBP patients: but, until the introduction of the RC, this was not feasible because of persistent hypothermia. The rapid rewarming rate offered by the RC, the absence of any deleterious effects, and the practical usefulness of its "stand-off" capability, makes the RC a powerful competitor to current rewarming methods in both effectiveness and, of increasing importance, cost.

[1] J. Appl. Physiol. 1964; 21:1757-62
[2] J. Nutr. 1935; 9:261-80

Title: Treatment of the Hypercatabolic State in Burns
Author: S.-O. Liljedahl, M.D., Surgical Clinic, University Hospital, Linkping, Sweden
Publication: Annales Chirurgiae of Gynaecologiae 69: 191-196, 1980. 6 p.

Abstract:
An extensive burn injury produces a severe state of stress. No other injury causes a comparable increase in metabolism as that seen during the course of an extensive burn. The increased metabolism leads to an accelerated rate of tissue breakdown, loss of body mass and depletion of energy and protein reserves. In this article the course of the hypercatabolic state in severe burns will be discussed together with different ways to reduce it, and the methods we use to balance the nutritional state.

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