Background: In prehospital trauma care active warming is recommended to aid in protection from further cooling. However, scientific evidence of the effectiveness of active warming in a clinical setting is scarce. Also, evaluating the effectiveness of active warming, especially in harsh ambient conditions, by objective measures, is difficult. Objective: To evaluate the effectiveness of field applicabe heat sources (I) and to evaluate active warming intervention in a prehospital clinical setting (II and III). To evaluate reliability and validity of the Cold Discomfort Scale (CDS), a subjective judgement scale for assessment of the thermal state of patients in a cold environment (IV). Methods: In a laboratory trial, non-shivering hypothermic subjects (n=5), were cooled in 8 ºC water followed by spontaneous warming, a charcoal heater, two flexible hot-water bags or two chemical heat pads, all applied to the chest and upper back (I). Oesophageal temperature, skin temperature, heat flux, oxygen consumption, respiratory rate and, heart rate were measured. In two clinical randomized trials, shivering patients during road and air ambulance transport (II) and during field treatment (III) were randomized to either passive warming alone (n=22 and n=9) or to passive warming with the addition of a chemical heat pad (n=26 and n=11). Body core temperature, respiratory rate, heart rate, blood pressure (II) and the patients’ subjective sensation of thermal comfort (II and III) were measured. In a laboratory trial, shivering subjects were exposed to – 20 ºC (n=22). The CDS was evaluated regarding reliability, defined as test-retest stability, and criterion validity, defined as the ability to detect changes in cold discomfort due to changes in cumulative cold stress (IV). Results: In non-shivering hypothermic subjects postcooling afterdrop was significantly less for the chemical heat pads, but not for the hot water bags and the charcoal heater, compared to spontaneous warming (I). Temperature drop during the entire warming phase was significantly less for all the heat sources respectively, compared to spontaneous warming (I). During road and air ambulance transport, ear canal temperature was significantly increased and cold discomfort significantly decreased, both in patients assigned to passive warming only, and in patients assigned to additional active warming (II). During field treatment, cold discomfort was significantly reduced in patients assigned to additional active warming, but remained the same in patients assigned to passive warming only (III). Weighted kappa coefficient, describing test-retest stability, was 0.84 (IV). CDS ratings were significantly increased during each 30 minutes interval (IV). Conclusion: In non-shivering hypothermic subjects, heat sources were effective to attenuate afterdrop, when providing high heat content over a large surface area and effective to continue to increase body core temperature when providing sustained high heat content. In shivering trauma patients, adequate passive warming were sufficient treatment to prevent afterdrop, to slowly increase body core temperature, and to reduce cold discomfort. If inadequate passive warming, additional active warming was required to reduce cold discomfort. The CDS, a subjective judgement scale for assessment of the thermal state of patients in a cold environment seemed to be reliable regarding test-retest stability and valid regarding ability to detect change in cumulative cold stress.

No description available.

A study was performed on decerebrate ferrets to define the contribution of vagal afferent non-myelinated fibres to the baroreceptor heart rate reflex produced by bolus i.v. injection of phenylephrine, using capsaicin as a selective C fibre blocker. Capsaicin blocked pulmonary chemoreflex substantially without any effects on bradycardia evoked by electrical stimulation of vagal efferent fibres to the heart. The significance of the contribution to bradycardia in response to marked increases in blood pressure by vagal C fibres are discussed in relation to findings in electrophysiological studies. A further study was performed on decerebrate ferrets and chloralose anaesthetised lambs. Baroreflex sensitivity was assessed by the relationship between cardiac interval changes and a rise in systolic blood pressure produced by bolus injection of phenylephrine and descending aorta occlusion. Moderate hypothermia (30-34<SUP>o</SUP>C) enhanced the baroreflex heart rate reflex substantially and was without effect on the sensitivity of pulmonary J receptor reflex pathways involved in the heart rate control. Action of vagal efferent fibres in altering heart rate was increased by moderate cooling. Such an effect may be partially responsible for the enhanced heart rate component of baroreflex response. Other possible mechanisms of enhanced baroreflex sensitivity are discussed. The consequence of enhanced vagal efferent fibre on heart was studied by electrical stimulation of the peripheral end of cervical vagus nerves in decerebrate ferrets and anaesthetised lambs. Moderate cooling substantially increases cardiac arrhythmias, such as sinus bradycardia, sinoatrial block, sinus arrest and A-V block. In addition vagal stimulation resulted in lethal ventricular arrythmia during infusion of noradrenaline. The possible mechanisms underlying the collapse and sudden death following rescue are discussed.

published_or_final_version / Anaesthesiology / Master / Master of Research in Medicine

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: David G. Edwards, Dept. of Health, Nutrition, and Exercise Sciences. Includes bibliographical references.

Stroke is a leading cause of disability in Canada. Delayed hypothermia improves outcome in patients following cardiac arrest and reduces lesion volume in rodents after transient focal ischemia, but less is known about the effectiveness of delayed hypothermia following permanent focal ischemia. In Chapter 1, the efficacy of 12, 24 or 48 h of delayed hypothermia was evaluated one week following pMCAO. All treatments attenuated neurological deficits and brain water content, but only the 24 and 48 h treatments reduced stepping error rate and lesion volume. Thus, delayed hypothermia attenuates brain injury and functional deficits following permanent middle cerebral artery occlusion (pMCAO). Longer bouts of cooling provide superior protection; an effect that is not explained by lessened edema. Chapter 3 describes a novel method of focal brain hypothermia in rats. A metal coil was implanted between the Temporalis muscle and adjacent skull and flushed with cold water. Focal, ipsilateral cooling was successfully produced without cooling of the opposite hemisphere or the core. One day of focal hypothermia was maintained in awake rats without significant alterations in blood pressure, heart rate or body temperature. The described simple method allows for safe inductions of focal brain hypothermia in anesthetized or conscious rats, and is ideally suited to trauma or stroke studies. In Chapter 4, long-term efficacy of 12 and 48 h of delayed focal or systemic hypothermia was evaluated following pMCAO. Both systemic treatments equally reduced lesion volume and skilled reaching deficits compared to normothermic controls, but only the 48 h treatment reduced neurological deficits. Conversely, 12 h of focal cooling did not significantly improve outcome, whereas 48 h of focal brain cooling attenuated functional deficits and reduced lesion volume. Thus, both delayed focal and systemic hypothermia attenuate long-term brain injury and functional deficits following pMCAO. Duration of cooling is clearly an important factor that may depend upon the method of cooling. Overall, this data indicates that delayed and prolonged hypothermia provides substantial and persistent protection against pMCAO in the rat. Prolonged hypothermia is a promising neuroprotective therapy for acute stroke and further clinical investigation is warranted.

Många patienter blir hypoterma under den perioperativa vården. Det finns en mängd åtgärder som kan vidtas för att minska oönskad hypotermi. Pre- och intraoperativ uppvärmning med värmetäcke, varmt på operationssalen, cirkelsystem och användning av varma infusioner kan vara en bra kombination. Oavsett vilken terapi som används är normotermi alltid högt prioriterat.  Det handlar om patientsäkerhet. Genom att effektivt motverka hypotermi skulle möjligheten öka till snabbare återhämtning, färre postoperativa infektioner, mindre kostnader för sjukhuset och minskat lidande för patienter. Syftet med studien var att undersöka anestesisjuksköterskans upplevelser av att förebygga perioperativ hypotermi hos vuxna elektiva patienter. En kvalitativ intervjustudie med induktiv ansats gjordes inom problemområdet. Insamlingen av data gjordes genom intervjuer som spelades in. Intervjuerna transkriberades och analyserades med kvalitativ innehållsanalys. I resultatet framkommer att, även om normotermi är målet och ambitionen finns, är det många faktorer som spelar in hur vida de hypotermiförebyggande åtgärderna når framgång. Det krävs en god planering samt erfarenhet av förebyggande arbete. Att mätmetoderna är ifrågasatta kan bidra till att mätning inte alltid utförs. Avsaknad av riktlinjer kring hypotermiförebyggande åtgärder bidrar till oklarheter för vårdpersonalen. Alla de olika personalkategorierna kring en operation tenderar att fokusera på sina egna uppgifter. En stor ansvarskänsla samt till viss del ensamhetskänsla i besluten, om vilka åtgärder som skall vidtas samt när finns hos anestesisjuksköterskan. När patienten blir kall trots att anestesisjuksköterskan har gjort allt kan det upplevas som ett misslyckande att inte räcka till. När patienten anländer kall till uppvaket kan anestesisjuksköterskan känna skuld till patientens tillstånd samt lidandet det medför. Strävan är att patienten ska må bra även postoperativt. Genom att informera patienten om varför det är nödvändigt att det tillförs extra värme gör att patienten blir delaktig i omvårdnaden. Anestesisjuksköterskan upplever att värmda täcken, strumpor samt mössa gör patienten mindre spänd samt stressad. På så vis ökar man patientens upplevs av välbefinnandet.

Operating theatre is a cold environment and hypothermia (core body temperature lower than 36C) is prevalent among patients undergoing operations. Possible causes of this adverse condition include anesthetic effect, body part exposure, blood loss, and the low room temperature in the theatre. Hypothermia can impair wound healing, decrease drug metabolism, increase oxygen consumption, which in turn causing respiratory distress, bradycardia as well as atrial fibrillation. In extreme cases, it can be lethal. Numerous research studies have explored ways of interventions and new technologies to maintain normal body temperature of patients during operations. However, perhaps without proper translation to clinical practice, the rate of postoperative hypothermia still remains high in many hospital setting. The objectives of this thesis are to systematically review the current literature on the effectiveness of preoperative warming on reducing postoperative hypothermia of patients undergoing general anesthesia. Data from the relevant literature is extracted for setting up a table of evidence. Also, quality assessment is performed. An evidence-based practice guideline for preoperative warming is developed and its feasibility and transferability to the target patients is examined. The purpose of the guideline is to provide better care for patients undergoing general anesthesia. In this thesis, preoperative forced air warming is proposed. The target setting is the operating theatre department and day surgery centre in a local public acute hospital. The target population is patients who undergo general anesthesia. Data is extracted from six articles. The implementation potential of the proposed guideline is high, because of the high transferability, feasibility and cost-effective ratio. An evidence-based practice guideline is developed based on the evidence. Well-designed implementation and evaluation plan are developed for the implementation of the proposed guideline. / published_or_final_version / Nursing Studies / Master / Master of Nursing

No description available.

Perioperative hypothermia (PH) is body temperature < 36°C and may occur in total knee arthroplasty (TKA) surgery. Planned hypothermia is necessary in a select number of surgical procedures but inadvertent hypothermia has deleterious consequences. TKA is a painful procedure and PH may enhance or diminish the effect of opioids and TKA pain – its effect is unclear. A new treatment for PH is a forced-air warming gown. A randomized control trial of 30 TKA patients compared the standard treatment of warm cotton blankets to a forced-air warming gown. Patients treated with the warming gown had higher temperatures (p < 0.001), used less opioid (p = 0.05) and had more satisfaction (p = 0.004) than the standard blanket group. This study suggests that warming gowns may be an effective alternative to averting PH and advocates for more research to explore the relationship between PH and its effect on pain and opioids.