Rewarming Pattern Research Articles

Preliminary study of finger temperature recovery in patients with diabetes mellitus following cold stimulation.

To explore the difference in temperature recovery following cold stimulation between participants with and without diabetes mellitus (DM). The participants without (control group; n=25) and with (DM group; n=26) DM were subjected to local cold stimulation (10º C for 90s). The thermal images of their hands were continuously captured using a thermal camera within 7min following cold stimulation, and the highest temperature of each fingertip was calculated. According to the temperature values at different timepoints, the temperature recovery curves were drawn, and the baseline temperature (T-base), initial temperature after cooling (T0), temperature decline amplitude (T-range), and area under the temperature recovery curve>T0 (S) were calculated. Finally, symmetry differences between the two groups were analysed. No statistical differences in the T-base, T0, and T-range were observed between the DM and control groups. After drawing the rewarming curve according to the temperature of the fingertips of the patients following cold stimulation, the S in the DM group was significantly lower than that in the control group (p < 0.05). Furthermore, the asymmetry of the base temperature of the hand was observed in the DM group. Following cold stimulation, the patients with DM exhibited a different rewarming pattern than those without DM. Thus, cold stimulation tests under infrared thermography may contribute to the early screening of diabetic peripheral neuropathy in future.

Effect of neoadjuvant chemotherapy on intraoperative core temperature in patients with breast cancer: a retrospective cohort study.

Clinical evidence suggests that chemotherapeutic agents are associated with neuropathy and peripheral autonomic dysfunction. However, the possible effects of neoadjuvant chemotherapy on intraoperative temperature remain poorly characterised. We evaluated patients who underwent a mastectomy for breast cancer between April 2016 and July 2020. Propensity scores were used to match patients who received neoadjuvant chemotherapy with those who did not, and intraoperative core temperature patterns were analysed in the matched cohort. The independent associations between vasopressor use and heart rate during general anaesthesia in the matched cohort were also analysed. Data from 1764 patients were analysed (882 patients in each group). Both groups presented a similar pattern of heat redistribution and subsequent rewarming; however, the neoadjuvant chemotherapy group did not reach the same intraoperative plateau temperature as the group that did not receive prior chemotherapy, with differences of up to 0.4°C (95% confidence interval: 0.11-0.63°C; P=0.005). In a subgroup analysis, neuropathy in patients who received neoadjuvant chemotherapy was associated with increased use of vasopressors and higher heart rate. In patients with breast cancer, neoadjuvant chemotherapy is associated with lower plateau core temperatures, increased vasopressor use, and higher heart rates during general anaesthesia, which is more severe in the presence of neuropathy.

Dynamic Infrared Thermography (DIRT) in DIEP flap breast reconstruction: A clinical study with a standardized measurement setup

ObjectiveBreast reconstructions with perforator flaps from the lower abdomen, commonly known as Deep Inferior Epigastric artery Perforator flap (DIEP-flap), have become the golden standard for autologous breast reconstruction after breast amputation. During this surgical procedure multiple challenging steps are encountered such as the selection of a suitable perforator that provides sufficient blood supply for the flap, surgical dissection of the chosen perforator, determination of perfusion area of the chosen perforator, microsurgical anastomosis, flap inset and shaping the flap into a breast.The current gold standard for perforator mapping is Computed Tomography Angiography (CTA). However, this is a relatively expensive imaging modality that requires intravenous contrast injection and exposes patients to ionizing radiation. More recently, Dynamic Infrared Thermography (DIRT) has been proposed as an alternative imaging modality for perforator identification. DIRT appears to be an ideal alternative technique not only for the identification of the dominant perforators, but also for the mapping of the individual influence of each perforator on the flap perfusion, to monitor integrity of the perforator after dissection and to monitor the patency of the pedicle of the free flap after the anastomosis, during flap inset and flap shaping. Study designIn this clinical study we present the results of the use of DIRT in 33 DIEP-flaps in 21 patients after mastectomy. The same standardized measurement set-up was used for all the flaps in the pre-, intra- and postoperative period. ResultsIn the pre-operative period DIRT confirmed the location of the 69 perforators shown on the CTA. In the intra-operative period the rate and pattern of rewarming was successfully observed. One perforator was severely damaged during dissection and the DIEP flap was converted to a Muscle Sparing free Transverse Rectus Abdominis Muscle (TRAM) flap, after viability check of the flap by DIRT. DIRT diagnosed one kinking of the pedicle after microsurgical anastomosis. Two flaps were monitored successfully post-operatively. All 33 breast reconstructions were with good outcome. ConclusionThe use of DIRT with our standardized measurement setup is a useful, non-invasive tool during breast reconstructions with free DIEP-flaps in all the phases of the reconstruction (pre-, intra- and post-operative). This study confirms that DIRT with the standardized measurement setup provides information on perforator location, blood supply and patency of the anastomosis without interference with the operating surgeon.

Infrared thermography in children: a reliable tool for differential diagnosis of peripheral microvascular dysfunction and Raynaud\u2019s phenomenon?

BackgroundInfrared Thermography (IRT) has been used for over 30 years in the assessment of Raynaud Phenomenon (RP) and other peripheral microvascular dysfunctions in adults but, to date, very little experience is available on its use in children for this purpose. The first aim of the study was to assess reproducibility of thermographic examination after cold exposure by comparing inter-observer agreement in thermal imaging interpretation. The secondary aim was to evaluate whether IRT is reliable to diagnose and differentiate peripheral circulation disturbances in children.MethodsChildren with clinical diagnosis of primary Raynaud’s phenomenon (PRP), secondary RP (SRP), acrocyanosis (AC) and age-matched controls underwent sequential measurements of skin temperature at distal interphalangeal (DIP) and metacarpophalangeal (MCP) joints with IRT at baseline and for 10 min after cold challenge test. Intraclass correlation coefficient (ICC) was calculated for inter-rater reliability in IRT interpretation, then temperature variations at MCP and DIP joints and the distal-dorsal difference (DDD) were analysed.ResultsFourteen PRP, 16 SRP, 14 AC and 15 controls entered the study. ICC showed excellent agreement (> 0.93) for DIPs and MCPs in 192 measures for each subject. Patients with PRP, SRP and acrocyanosis showed significantly slower recovery at MCPs (p < 0.05) and at DIPs (p < 0.001) than controls. At baseline, higher temperature at DIPs and lower at MCPs was observed in PRP compared with SRP with significantly lower DDD (p < 0.001). Differently from AC, both PRP and SRP showed gain of temperature at DIPs and less at MCPs after cold challenge. PRP but not SRP patients returned to DIPs basal temperature by the end of re-warming time. Analysis of DDD confirmed that controls and PRP, SRP and AC patients significantly differed in fingers recovery pattern (p < 0.05).ConclusionIRT appears reliable and reproducible in identifying children with peripheral microvascular disturbances. Our results show that IRT examination pointed out that PRP, SRP and AC patients present significant differences in basal extremities temperature and in re-warming pattern after cold challenge therefore IRT can be suggested as an objective tool for diagnosis and monitoring of disease.

Variability in peripheral rewarming after cold stress among 255 healthy Norwegian army conscripts assessed by dynamic infrared thermography

ABSTRACTExposure to cold climate is an inevitable consequence of military training in Norway. Adequate peripheral microcirculation in the extremities is important to maintain temperature, and to protect against freezing cold injuries. The aim of this study was to investigate the variability in skin rewarming ability. The study subjects consisted of 260 healthy Norwegian army conscripts, following a mild cold provocation test (hands immersed in 20°C water for 1 min) using dynamic infrared thermography (DIRT). Thermal images were obtained to investigate any differences in skin rewarming ability of the hand (fingers). DIRT took place under standardised and stable study conditions. Conscripts were characterised as either slow, intermediate or rapid rewarmers. While 90% could recover, partially or completely, within 4 min to the skin temperature values before the provocation test, 10% showed a slow rewarming pattern. In the slow rewarmers, the rewarming ability was correlated with a low average temperature of the hands prior to the cooling test. The healthy young army conscripts in this study showed a large variability in their rewarming ability following a standardised mild cold provocation test.

Evaluation of a home treatment program for cold hypersensitivity using a classical conditioning procedure in patients with hand and arm injuries

Study designCase series. IntroductionA home treatment program using a classical conditioning procedure to decrease cold hypersensitivity has potential to reduce symptoms. PurposeTo evaluate a home treatment program for cold hypersensitivity using a classical conditioning procedure in patients who are cold hypersensitive after hand and arm injuries. MethodsA series of 22 patients followed a classical conditioning procedure consisting of exposing the body to cold outdoor temperatures and immersing the hands in warm water, every other day, for five weeks. The McCabe Cold Sensitivity Severity scale (CSS) was used to measure cold hypersensitivity twice before treatment, at four weeks, and at one year after treatment; Likert scales was used for the patients ratings of improvements. A cold stress test was performed to evaluate rewarming capacity in injured fingers. ResultsFrom the 20 patients, who returned questionnaires at all assessment points, 9 reported a small and three reported a moderate improvement in cold hypersensitivity after treatment. There was a trend toward improvement in the CSS (median 36; interquartile range −19 to 60) and in the rewarming pattern of fingers that were initially slow to rewarm. The improvements were sustained or increased at one-year follow-up. ConclusionThese preliminary results suggest that the classical conditioning procedure to treat cold hypersensitivity has potential and should be further explored in a trial with more rigorous design. Level of evidenceIV.

Livedo and ischemic strokes: diagnostic hints of a rare condition

Sneddon’s syndrome (SS) is a rare condition characterized by the combination of ischemic strokes and cutaneous livedo [1, 2], defined as the ‘‘persistent, not reversible with rewarming, violaceous, reticular or mottled pattern of the skin of trunk, arms or legs, consisting of regular unbroken circles (livedo reticularis) or irregular-broken circles (livedo racemosa)’’. Other well-defined neurological manifestations of SS include headache, seizures, and vascular dementia. Here, we report two cases with clinical and imaging features suggestive of SS. In both patients skin biopsy was performed and sections were stained with hematoxylin and eosin (HE general examination revealed diffused livedo racemosa (Fig. 1a). An extensive cardiological evaluation including an electrocardiogram, an echocardiogram and carotid ultrasound evaluation ruled out cardiovascular causes of stroke. Coagulation parameters (including fibrinogen and D-dimer), inflammatory indexes, syphilis serology, and autoimmune antibody panels including, ANA, ENA, ANCA, lupus anti-coagulants (LAC) and antiphospholipid antibodies (IgM and IgG anti-cardiolipin and anti-b2-microglobulin) were negative. A heterozygous mutation of factor V Leiden was detected. Brain MRI showed cortical atrophy and multiple ischemic lesions involving both the superficial and deep territories of posterior and middle cerebral artery (Fig. 1b). Skin biopsy showed intra-capillary and parietal widespread thrombosis (Fig. 1c). Oral anticoagulants and antipsychotic were added to therapy. A 65-year-old man (Case 2) presented with a 3-year history of progressive lower limbs weakness and mixed dysphagia. He had been having recurrent ischemic strokes since he was 55. He had history of myocardial infarcts, hypertension, and smoking. His neurological examination revealed dysphagia, ataxic and spastic gait, limbs hyperreflexia, right extensor plantar response. General examination revealed diffused livedo racemosa at the trunk and lower limbs (Fig. 1a). A cardiological evaluation and electrocardiogram ruled out the presence of heart arrhythmia; echocardiography demonstrated mild hypokinesia of apical and distal septum of lateral ventricle, as consequence of previous myocardial infarcts. Coagulation parameters and thrombophilic screening were normal. Brain MRI showed diffused cortical atrophy and multiple ischemic lesions (Fig. 1b) in both medium-sized superficial and deep, posterior and middle cerebral artery territories. Skin biopsy revealed intra-capillary and parietal widespread thrombosis (Fig. 1c). As for the first patient, oral anticoagulants were added to therapy. G. Cirillo A. Tessitore (&) F. Salemi S. Liguori S. Esposito G. Tedeschi Department of Neurology, Second University of Naples, 80138 Naples, Italy e-mail: alessandro.tessitore@unina2.it

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INTRODUCTION: Multidetector computed tomography (MDCT) angiography is “the gold standard” for preoperative perforator selection. DIRT is based on the relationship between dermal perfusion and the change in rate and pattern of skin rewarming following a cold challenge. Can DIRT be an alternative to MDCT? METHODS AND MATERIALS: 23 patients scheduled for breast reconstruction with DIEP flap were included. Preoperatively arterial perforator sounds were located with a hand held Doppler. Afterwards a desktop fan was used to deliver a mild cold challenge to the lower abdomen. The rate and pattern of rewarming of the skin was registered with an infrared camera. The locations of first appearing hot spots on the skin were registered. Eight patients had an additional MDCT scan. RESULTS: A rapid appearing “hot spot” was associated with an arterial Doppler sound and a suitable perforator intraoperatively. All DIEP flaps survived and were based on the perforator as selected from DIRT. The selected hot spot could easily be related to a perforator on the MDCT scan. CONCLUSION: Perforator selection of DIEP flaps is facilitated with the use of DIRT. The technique is non-invasive, provides real-time information and does not require exposure to ionizing radiation or intravenous contrast medium. DIRT could be an alternative for MDCT in perforator selection.

Autonomic nerve system responses for normal and slow rewarmers after hand cold provocation: effects of long-term cold climate training

Differences among individuals concerning susceptibility to local cold injury following acute cold exposure may be related to function of the autonomic nervous system. We hypothesized that there are differences in heart rate variability (HRV) between individuals with normal or more pronounced vasoconstriction following cold exposure and that there is an adaptation related to prolonged cold exposure in autonomic nervous system response to cold stimuli. Seventy-seven young men performed a cold provocation test, where HRV was recorded during cold hand immersion and recovery. Forty-three subjects were re-examined 15 months later, with many months of cold weather training between the tests. Subjects were analyzed as 'slow' and 'normal' rewarmers according to their thermographic rewarming pattern. For the 'pre-training' test, before cold climate exposure, normal rewarmers had higher power for low-frequency (PLF) and high-frequency (PHF) HRV components during the cold provocation test (ANOVA for groups: p = 0.04 and p = 0.005, respectively). There was an approximately 25 % higher PHF at the start in normal rewarmers, in the logarithmic scale. Low frequency-to-high frequency ratio (PLF/PHF) showed lower levels for normal rewarmers (ANOVA for groups: p = 0.04). During the 'post-training' cold provocation test, both groups lacked the marked increase in heart rate that occurred during cold exposure at the 'pre-training' setting. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low-frequency and high-frequency HRV components. After winter training, the slow rewarmers showed reduced low-frequency power for some of the cold provocation measurements but not all (average total PLF, ANOVA p = 0.05), which was not present before winter training. These HRV results support the conclusion that cold adaptation occurred in both groups. We conclude that further prospective study is needed to determine whether cold adaptation provides protection to subjects at higher risk for cold injury, that is, slow rewarmers.

Thermoregulation in peripheral nerve injury-induced cold-intolerant rats

Cold intolerance is defined as pain after exposure to non-painful cold. It is suggested that cold intolerance may be related to dysfunctional thermoregulation in upper extremity nerve injury patients. The purpose of this study was to examine if the re-warming of a rat hind paw is altered in different peripheral nerve injury models and if these patterns are related to severity of cold intolerance. In the spared nerve injury (SNI) and complete sciatic lesion (CSL) model, the re-warming patterns after cold stress exposure were investigated preoperatively and at 3, 6 and 9 weeks postoperatively with a device to induce cooling of the hind paws. Thermocouples were attached on the dorsal side of the hind paw to monitor re-warming patterns. The Von Frey test and cold plate test indicated a significantly lower paw-withdrawal threshold and latency in the SNI compared to the Sham model. The CSL group, however, had only significantly lower paw-withdrawal latency on the cold plate test compared to the Sham group. While we found no significantly different re-warming patterns in the SNI and CSL group compared to Sham group, we did find a tendency in temperature increase in the CSL group 3 weeks postoperatively. Overall, our findings indicate that re-warming patterns are not altered after peripheral nerve injury in these rat models despite the fact that these animals did develop cold intolerance. This suggests that disturbed thermoregulation may not be the prime mechanism for cold intolerance and that, other, most likely, neurological mechanisms may play a more important role. There is no direct correlation between cold intolerance and re-warming patterns in different peripheral nerve injury rat models. This is an important finding for future developing treatments for this common problem, since treatment focussing on vaso-regulation may not help diminish symptoms of cold-intolerant patients.

Rewarming Patterns in Hand Fracture Patients With and Without Cold Intolerance

It is often assumed that cold intolerance is associated with abnormalities in the skin temperature due to changes in the blood flow of the hands. In this study, we determined whether patients with and without cold intolerance after a hand fracture or healthy controls have a diminished rewarming after a cold stimulus. The severity of cold intolerance was evaluated using the Cold Intolerance Symptom Severity (CISS) questionnaire. To determine whether abnormal rewarming plays a major role in the underlying pathophysiology of cold intolerance, a cold-stress test was applied at a mean of 30 months (with a range of 11 mo) after the patients recovered from a hand fracture. A control group also underwent identical cold-stress testing for comparison. Temperature during the rewarming phase was measured using videothermography. Thirteen control subjects and 18 patients participated. Control subjects did not report any symptoms of cold intolerance (CISS score, 0) and no loss of sensibility was measured. The mean CISS score of all patients was 27.8; 9 patients scored above the cut-off value for normal cold intolerance. No significant differences were found in the rewarming patterns between (1) the affected and non-affected hand of the postfracture patients, (2) the dominant and non-dominant hand of the control subjects, and (3) the patients and controls. The results of this study revealed no relation between the severity of cold intolerance and rewarming patterns after cold stress testing. This might suggest that temperature regulation of the hands in post-fracture patients might not be responsible for the symptoms of cold intolerance, based on cold-stress test response.

Neural influence on cold induced vasodilatation using a new set-up for bilateral measurement in the rat hind limb

Cold induced vasoconstriction (CIVC) is a way for mammals to reduce heat loss in an effort to maintain body core temperature. As blood flow to a cooled extremity is reduced, the amount of body heat lost at the cooled location is minimised. However, when the extremity temperature gets below a certain threshold, Cold induced vasodilatation (CIVD) occurs, a phenomenon that is believed to reduce the risk of local cold injuries. Many theories explaining the mechanism of the CIVD reaction have been postulated, but no consensus has been found. One of these theories is that the CIVD reaction is controlled neurally. To study the effect of neural influence on the vascularisation and rewarming patterns a new experimental set-up was designed. This set-up is able to measure responses in both hind paws simultaneously, creating the opportunity to study the effect of nerve injury on one limb and use the contralateral limb as a control. Ten rats received a sciatic nerve transection and repair of either the left ( n = 5) or the right ( n = 5) hind limb. Measurements were performed, 1 day pre-operatively, directly post-operatively, and at days 1, 7, 14, 21, 35 and 49 post-operatively. Although results are not significant, there is a tendency for the CIVD reaction to be reduced in the nerve injured paw until the nerve is regenerated around day 35. Further investigation of neural influence on the CIVD reaction will be necessary; this set-up may prove to be useful in future experiments to elucidate the mechanism of the CIVD reaction.

Digital Rewarming Patterns After Median and Ulnar Nerve Injury

Posttraumatic cold intolerance (CI) is a frequent and important sequel after peripheral nerve injury. In this study, it is hypothesized that altered rewarming patterns after peripheral nerve injury are related to the degree of posttraumatic CI. This hypothesis is tested by quantitatively comparing rewarming patterns of the digits in controls and in median or ulnar nerve injury patients and by investigating relationships between rewarming patterns, sensory recovery, and CI. Twelve median or ulnar nerve injury patients with a follow-up of 4 to 76 months after nerve repair and 13 control subjects had isolated cold stress testing of the hands. Video thermography was used to analyze and compare rewarming patterns of the injured and uninjured digits after cold stress testing. Temperature curves were analyzed by calculating the Q value as an indicator of heat transfer (temperature added during the first 10 minutes after start of active rewarming) and the maximum slope. Test-retest reliability was 0.64 and 0.79, respectively, for the Q value and maximum slope. High Q values and maximum slopes were interpreted as the presence of active rewarming. Patients with return of active rewarming had better sensory recovery and lower Blond McIndoe Cold Intolerance Severity Scale (CISS) scores. Better sensory recovery was correlated with lower CISS scores. Test-retest reliability of cold stress testing was good, and we found a difference in rewarming patterns between nerve injury patients and controls. The presence of active rewarming in the nerve injury patients was related to sensory recovery and fewer complaints of posttraumatic CI.

A cold-response index for the assessment of Raynaud's phenomenon

Quantification of Raynaud's phenomenon (RP) is a prerequisite in the evaluation of novel therapeutic strategies. Fingertip rewarming in response to local cold provocation has been used in many studies but not been systematically validated. We have previously described the time elapsed before 63% of pre-cooling temperature is reached as a RP activity index. A comprehensive evaluation of fingertip rewarming in primary and scleroderma-associated RP. We defined a cold-response index (CRI) as the log transformation of the 63% rewarming time upon cold challenge. The CRI shows high intra-individual reproducibility. The mean CRI values were (mean+/-S.D.): 2.4+/-0.3 in controls (n=53) versus 2.7+/-0.3 in RP (n=50, p<0.0001 versus controls), and 2.7+/-0.3 in scleroderma patients (n=46, p<0.0001). In addition, baseline fingertip temperature was also found to be significantly reduced both in primary as well as scleroderma-associated RP. Kinetic analysis of rewarming temperature curves demonstrates that the CRI is independent of individual rewarming patterns. Finally, the CRI decreases significantly upon a single low-level systemic hyperthermia treatment in scleroderma patients (2.68+/-0.28 before versus 2.45+/-0.33 after, p=0.0003), while the extent of cooling remained unchanged, thus demonstrating sensitivity to change. Our results provide a solid basis for using the cold-response assay as an endpoint in addition to clinical activity scores in RP treatment trials.

Intraoperative Dynamic Infrared Thermography and Free-Flap Surgery

Flap failure in free-tissue transfer relates strongly to technical failure of the anastomosis or to kinking as well as to external compression of the donor or recipient vessels. Intraoperative monitoring of flap perfusion has shown to prevent flap failure. This prospective, clinical study presents the results of intraoperative dynamic infrared thermography as a novel method to monitor reperfusion indirectly in 10 free flaps. This noninvasive technique provided a fast and reliable method to register partial or total arterial occlusion due to anastomotic failure, as well as due to external compression or kinking of the vessels. The dynamic infrared image sequences showed an improved rate and pattern of rewarming of the flap after an additional venous anastomosis was opened. The state of reperfusion of the flap at the end of the operation could easily be determined. The authors conclude that dynamic infrared thermography provides the surgeon with valuable information on flap reperfusion during free flap surgery.

Effect of a short period of abstinence from smoking on rewarming patterns of the hands following local cooling

The purpose of the study was to examine the effect of a 12 h period of abstinence from smoking in young and old habitual smokers, on skin rewarming patterns of a hand following local cooling. This was done by comparing changes in peripheral circulation, measured indirectly by monitoring changes in skin surface temperatures of the hand with both infrared (IR) thermography and thermocouples before, during and after immersing the right hand for 2 min in water at 10 degrees C. Included in the study were young male non-smokers (n = 14) and smokers (n = 13), and elderly non-smokers (n = 12) and smokers (n = 14). The results showed no statistically significant difference between young non-smokers and smokers when comparing their response to the local cold challenge. The elderly smokers had a significantly higher hand skin temperature prior to cooling (34.0 +/- 0.2 degrees C) and after 80% rewarming (32.1 +/- 0.2 degrees C) (i.e. when the skin temperature in the "cooled" hand has regained 80% of the cold induced drop in temperature), compared to elderly non-smokers (33.3 +/- 0.2 and 31.3 +/- 0.2 degrees C, respectively). The elderly smoking subjects also had a faster recovery after cooling (9.7 +/- 0.8 min) than the elderly non-smoking subjects (16.7 +/- 2.6 min). A follow-up study with seven elderly smokers, who had smoked as usual until 2 h before the experiment, showed responses lying between the non-smokers and smokers who had had a longer period of abstinence (12 h) from smoking. In conclusion, we have demonstrated using IR-thermal imaging that elderly subjects who have smoked for many years have slightly warmer hand skin temperature when they abstain from smoking. Even a period of abstinence from smoking of a few hours can affect the way in which elderly subjects respond to a local cold challenge, recovering more rapidly then their non-smoking counterparts.

Computerized infrared thermographic imaging and pulpal blood flow: Part 2. Rewarming of healthy human teeth following a controlled cold stimulus.

To investigate the rewarming pattern and rewarming rate of clinically healthy teeth following a controlled cold stimulus using TI techniques. A controlled cold stimulus was developed using an air stream at 20 degrees C. Gingival and incisal sites on 12 healthy maxillary lateral incisors in six patients were imaged under rubber dam following 20 s cooling. Images were captured at 10 s intervals during a 3-min rewarming period and the data used to construct graphs of the rewarming rate. Log transformation of the data was used to produce 'best fit' straight line graphs. Linear regression analysis was used to examine three variables, viz. the side of the mouth (right or left), the site of measurement (gingival or incisal) and the phase of rewarming (early 0-90 s, late 91-180 s). The mean temperature change (delta t degree C) during rewarming was 8.5 degrees C (SD 1.0 degree C) for gingival sites and 7.2 degrees C (SD 1.1 degrees C) for incisal sites. The slope of the 'best fit' straight line data enabled a rewarming index to be calculated for each site on each tooth. Linear regression analysis showed that the phase of rewarming was highly significant but the other variables were not. A one-way ANOVA showed no significant differences between or within groups. Three min is an appropriate time to record rewarming of teeth cooled for 20 s with an airstream at 20 degrees C. The side or site used to record surface temperatures using this technique is not significant. Rewarming is exponential and log transformation of the data produces a well-fitting straight line graph. The slope of this line provides a rewarming index which should enable comparison of TI and laser Doppler flowmetry in determining pulpal blood flow as a measure of tooth vitality.

Thermography of hands after a radial forearm flap has been raised.

To evaluate possible circulatory changes in the donor hand 18 patients underwent cold stress testing and thermography of both hands a mean of 13 months after a radial forearm flap had been harvested. Temperatures were measured with a computed Inframetrics 600L infrared thermocamera, and the images were videotaped at room temperature and after a cold challenge (immersion in a water bath at 15 degrees C for five minutes). Temperatures were measured on the volar aspect of each fingertip, and rewarming curves were plotted for both hands. The patients could be divided into three groups according to the rewarming pattern: mean temperature of the donor hand was more than 0.5 degree C warmer than that of the other hand (n = 7), rewarming was similar in both hands (n = 6), and the mean temperature of the donor hand was less than 0.5 degree C colder than that of the other hand (n = 5). Patients with a colder donor hand had significantly wider (Pearson's r = 0.62, p = 0.005) and longer (r = 0.71, p = 0.001) defects. The rewarming pattern did not correlate with subjective cold intolerance, but the temperature of the donor hand was a mean of 0.5 degree C less than that of the other hand in room temperature in subjects who experienced cold intolerance (p = 0.019). We conclude that the raising of a radial forearm flap, particularly a large one, affects the thermoregulatory system of the donor hand, results in abnormal rewarming, and can cause subjective cold intolerance.

External rewarming and age in mildly hypothermic patients after cardiac surgery

To compare the effects of two external rewarming methods on body core temperature and the rate of rewarming between two age groups (less than 65 years, 65 years or more) of adult, mildly hypothermic patients who have undergone cardiac surgery, during the immediate postoperative period. Stratified, randomized clinical trial. Five-bed cardiac surgical intensive care unit in a large teaching-research institution. Thirty-two white patients who had undergone cardiac surgery and who had mildly hypothermic body core temperatures (33 degrees to 35 degrees C) immediately after the surgery. Body core temperature was measured with a pulmonary artery catheter thermistor at the time of external rewarming method application and at 60, 90, and 150 minutes afterward. Rate of rewarming was measured as body core temperature change in degrees Celsius per hour (at 36.6 degrees C, minus body core temperature when external rewarming method was applied, divided by total rewarming time). Temperatures were recorded six times at intervals of 15 minutes; then every 30 minutes until a value of 36.6 degrees C was obtained, at which time the blanket was removed; then hourly for 8 hours. Either a fluid-filled circulating blanket (active-conductive external rewarming) or a reflective blanket (passive-reflective external rewarming) was applied immediately after core temperature was measured on admission to the cardiac surgical intensive care unit after surgery. External rewarming methods affected body core temperature differently at different times, and there were significant differences in body core temperature across the time periods (p < 0.05). Both active and passive external rewarming methods showed a sigmoidal rewarming pattern without a downward temperature drift. The fluid-filled circulating blanket produced a quicker and steeper body core temperature change in the early rewarming phase; the reflective blanket resulted in a more gradual temperature rise. Age did not significantly affect body core temperature, nor did age or external rewarming method significantly influence the rate of rewarming, although total rewarming time was longer for those of more advanced age. Seven subjects with passive rewarming method experienced body core temperature overshoot during the 8-hour period after blanket removal. In this study, conduction and reflection of radiant heat were equally effective in producing an acceptable rate of rewarming but contributed to different internal patterns in core rewarming. The average total rewarming time with the active external rewarming method was 1 hour shorter than with the passive external rewarming method.

Shivering and rewarming after cardiac surgery: comparison of ventilator circuits with humidifier and heated wires to heat and moisture exchangers

Detrimental physiologic effects of shivering in the cardiac surgery patient have been well documented. Rewarming techniques have been compared, with noted differences in the incidence of shivering. Ventilator circuits have not been examined independently from other rewarming variables. To compare heated wire humidification circuits with heat and moisture exchanger circuits on the incidence of shivering and speed and pattern of rewarming in mechanically ventilated patients. A prospective, descriptive, correlational study was done on 140 adult cardiac surgery patients in a university teaching medical center. All subjects underwent cardiac surgical procedures with hypothermic cardiopulmonary bypass. Subjects were randomized to humidified, heated wire circuits (n = 70) or heat and moisture exchanger circuits (n = 70). Heated water blankets were used on all patients. Mean intensive care unit admission temperature was 35.28 degrees C. No statistical differences were found in preoperative, demographic, or operative course data between treatment and control groups. Shivering was more common in the heat and moisture exchanger group than in the heated wire group. In our analysis, the only variable associated with shivering was the type of ventilator circuit. Patients using heated wire systems rewarmed more rapidly and had significantly higher temperatures than did patients using heat and moisture exchangers. These data suggest that use of heated wire humidified ventilator circuits with heated water blankets in adult cardiac surgery patients significantly reduces the incidence of shivering and results in a more rapid return to normothermia.