Patient Care

Thermal Management of the Surgical Patient

Sigg DC, Houlton AJ, Iaizzo PA: The potential for increased risk of infection due to the reuse of convective-air warming/cooling coverlets. Acta Anaesthesia Scandinavica. 43: 173-176, 1999.

Background: The use of convective air warming and/or cooling for the prevention of hypothermia or to induce hypothermia is growing rapidly. To date, there is no information available as to the potential risks for infection associated with either the postsurgical reuse or the repositioning of coverlets closer to the wound. We hypothesized that use of coverlets either intra- or postoperatively leads to increased contamination.

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Methods: The bacterial contamination of commercially available coverlets before (control group, n=10) and after patient application (n=18) was investigated. From three predetermined sites, 1cm x 2cm pieces of coverlet were removed and analyzed for bacterial contamination.

Results: Even prior to use, coverlet samplings provided identifiable contamination (3 out of 30 sites, 10%), but this could be within our study's sampling error. Nevertheless, following clinical use the frequency for contamination was considerably increased; 17 out of 57 sampled sites (31.5%) elicited contamination (p›0.05, Fisher's exact test).

Conclusion: This study demonstrates, that the use of the coverlets, intra- or postoperatively, can lead to significant bacterial contamination. It is concluded that it is not advisable to reuse coverlets for multiple clinical applications.

Iaizzo PA, Jeon Y, Sigg D: Facial warming increases the threshold for shivering. Journal of Neurosurgical Anesthesiology 11:231-239, 1999.

Background: As little as 1°C core hypothermia provides significant protection against cerebral ischemia. However, shivering usually prevents induction of hypothermia in unanesthetized subjects. We, therefore, tested the hypothesis that facial and airway heating reduces the shivering threshold and enables core cooling in unanesthetized subjects. Such a procedure could be applied to unanesthetized or lightly sedated neuropatients (head injury, acute stroke) in the ICU or even initiated while these patients are being transported to a medical center.

Methods: Nine experimental trials were performed on a group of seven healthy male volunteers. Each subject was positioned supine on a circulating-water mattress (8-15 °C) with a convective air coverlet (15-18°C) extending from the neck to the feet. A dynamic study protocol governed by individualized physiological responses was utilized. Focal facial (and airway) warming was employed to suppress such involuntary motor activity and, thereby, to enable non-invasive cooling to lower the core temperature. The following parameters were monitored throughout: 1) heart rate; 2) blood pressure; 3) core temperature (tympanic, axilla and rectal); 4) cutaneous temperatures; and 5) a subjective shiver index (scale 1-10). In three of the experimental trials, electromyograms (EMG) and infra-red thermographs were also obtained.

Results: Upon cooling without facial and airway warming, involuntary motor activity (muscle tensing and shiver) increased until it was widespread. This vigorous motor activity prevented any significant lowering of core temperature or caused it to slightly increase. Subsequently, in all subjects, within seconds after the application of facial focal warming, motor activity was suppressed almost completely, and within minutes core temperatures significantly decreased. Also, concomitant with facial and airway warming was an increased subjective tolerance for the active cooling.

Conclusion: Preliminary studies described here indicate that focal facial warming applied during active whole body cooling to induce hypothermia minimizes the need to pharmacologically suppress involuntary motor activity. Such a procedure could be used to initiate, as soon as possible (e.g., during emergency transport), cerebral mild hypothermia in order to maximize protection and thus improve outcome in appropriate patients.

Cerebral protection using mild hypothermia

Brain temperatures markedly influence the consequences of cerebral ischemia, and a mild reduction of core temperature by 1-2°C may confer significant cerebral protection. Various studies have shown that mild hypothermia can be beneficial for stroke patients (lower infarct size and mortality) and febrile patients. Three primary modes of noninvasive cooling can be employed either individually or in combination—convective (forced air blankets), conductive (circulating water blankets/mattresses), and evaporative. However, the relative clinical efficacies of different methods for reducing core body temperature have not been thoroughly studied.

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In evaluating any type of cooling technique that is employed without anesthesia, it is considered that skin warmth and thus vasodilation must be controlled in order to avoid counter-productive shivering. Thus, initial studies in our labs have aimed to comparatively assess the clinical application of focal facial warming and focal hand warming with several different cooling techniques in healthy, unanesthetized subjects.

Related articles from the labs:
  • Lanier WL, Iaizzo PA, Murray MJ: The effects of convective cooling and rewarming on systemic and central nervous system physiology in isoflurane-anesthetized dogs. Resuscitation 23: 121-136, 1992.
  • Iaizzo PA, Jeon YM, Sigg DC: Facial warming increases the threshold for shivering. Journal of Neurosurgical Anesthesiology 11: 231-239, 1999.
  • Sweney MT, Sigg DC, Tahvildari S, Iaizzo PA: Shiver suppression using focal hand warming in unanesthetized normal subjects. Anesthesiology 95: 1089-1095, 2001.
  • Pozos RS, Iaizzo PA, Danzl DF, Mills W III: Limits of tolerance to cold. In: Handbook of Physiology: Environmental Physiology, Fregly MJ, Blatteis CM (eds.) Oxford University Press, Chapter 25, pp. 557-578, 1996.
Patents related to this research:
  • US5860292: Inflatable thermal blanket for convectively cooling a body: Augustine SD, Iaizzo PA: Issued January 19, 1999.
  • US6119474: Inflatable thermal blanket for convectively and evaporatively cooling a body. Augustine SD, Iaizzo PA: Issued September 19, 2000.
  • U6487871: Apparatus, system and method for convectively and evaporatively cooling a body. Augustine SD, Iaizzo PA: Issued December 3, 2002.
  • US 6,581,400: Apparatus, system and method for convectively and evaporatively cooling a head. Augustine SD, Iaizzo PA: Issued June 24, 2003.

LTX3000™ Lumbar Rehabilitation System

The LTX3000™ is a lumbar rehabilitation system designed to treat low back pain and stiffness. Appropriate candidates have disk-related back pain or have ungone spine surgery, but continue to have low back or leg pain.

Use of the LTX3000™ is recommended by physicians, physical therapists, rehabilitation specialists and QRCs.

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The unique benefits of using the LTX3000™ are that it stabilizes the low back, encourages a neutral spine position, provides lumbar traction, and allows for therapeutic exercise while the user is in a functional seated position.

Additional advantages of prescribing the LTX3000™ are the ease of use and the ability to utilize the unit both at home or work, thus contributing to high patient compliance.

Recommended Protocol:
  • 3-4 sessions daily, 10-15 minutes per session
  • Recommended usage is 2-3 months. Continued usage determined by physician and/or physical therapist evaluation of patient's progress.