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At least 973 records · Page 54Linked to original sources
PubMed1994

The effect of cardiopulmonary bypass on gastric and colonic mucosal perfusion: a tonometric assessment.

In a study to assess the potential effect of nonpulsatile hypothermic cardiopulmonary bypass (CPB), intramucosal pH (pHi) of the gastric and colonic mucosae was determined by tonometry (n = 8). During the hypothermic phase of CPB, gastric and colonic pHi did not change significantly. Forty minutes after the start of rewarming, despite increases in the cardiac index and mean arterial blood pressure, gastric pHi fell from 7.53 +/- 0.02 to 7.31 +/- 0.03 (p = 0.017) and colonic pHi fell from 7.50 +/- 0.02 to 7.32 +/- 0.03 (p = 0.028). Forty minutes after the end of CPB both the colonic (p = 0.017) and gastric (p = 0.046) pHi remained depressed below pre-CPB values. The difference in the arterial (pHa) and the gastric mucosal pH changed from -0.097 before CPB to 0.016, 40 minutes after the end of CPB (p = 0.027). This alteration in the pHa-pHi underlines the importance of measuring intramucosal pH by tonometry, since the pHa and pHi may move in opposite directions during episodes of haemodynamic stress. Both the gastric and colonic pHi were found to have a linear correlation with the pHa, although changes in the gastric pHi (r = 0.41, p = 0.018) were more strongly correlated with the pHa than the colonic pHi (r = 0.23, p = 0.19) in the rewarming phase of CPB and the immediate post-CPB period when there was a tendency towards intramucosal acidosis. The development of intramucosal acidosis in the rewarming and immediate post-CPB phases following hypothermic nonpulsatile CPB may impair the gut barrier and predispose patients to the absorption of luminal toxins.

Blood Pressure↗
PubMed1996

Profound accidental hypothermia in the deep South: clinical experience.

Accidental hypothermia resulting from exposure is generally associated with frigid regions and not with the more temperate areas of the South. However, we present clinical experience from two cases in which the victims of motor vehicle accidents were exposed to the elements for prolonged periods and became profoundly hypothermic. The first patient was a 21-year-old male who was ejected from, and pinned under, his vehicle for approximately four hours in -15 degrees C ambient temperature. Upon admission to the Emergency Room, the patient was unresponsive with fixed and dilated pupils and his core temperature was 25 degrees C. After a prolonged period of cardiopulmonary resuscitation, percutaneous femoral to femoral cardiopulmonary bypass (CPB) was instituted for core rewarming. After reaching 37 degrees C, the patient was removed from bypass. The patient was discharged from the hospital on the fourth postoperative day. The second patient was a 40-year-old male who was ejected from his vehicle into a stream, where he was partially submerged for several hours. Although the ambient temperature was approximately 22 degrees C, his core temperature at admission was 27 degrees C. After a positive peritoneal lavage, the patient was taken to the Operating Room and placed on percutaneous femoral to femoral CPB for core rewarming. During rewarming, an exploratory laparotomy and a splenectomy were performed. The patient was discharged from the hospital on the seventh postoperative day. These cases are unique in that both were trauma patients with suspected internal injuries which required the avoidance of anticoagulation. Therefore, both cases utilized a Carmeda-bonded circuit without systemic anticoagulation.

Accidents, Traffic↗
PubMed1997

Fingertip temperature during cardiopulmonary bypass.

Temperature changes in the nasopharynx, fingertip, forearm and extracorporeal circuit were continuously monitored, starting 10 min before and up to 16 min into the rewarming period of hypothermic (32 degrees C) cardiopulmonary bypass in 14 patients operated on for coronary artery revascularization. Arterial blood temperature was the first to increase after starting rewarming, followed by the nasopharynx and the fingertip temperatures. Fingertip temperature started to increase abruptly 6.2 (2.02 SD) min after rewarming started. At this point, nasopharyngeal temperature was 34.2 degrees C (1.42 SD) and took a further 8.3 min to reach 37 degrees C. Assuming that increasing fingertip temperature indicates a central thermoregulatory response to warming, we suggest that nasopharyngeal temperature is a poor monitor of brain temperature. We also suggest that fingertip temperature may be used to monitor the point at which cerebral temperature reaches 'normothermia'. Further body warming, using arterial temperatures > or = 39 degrees C, should be avoided because of the danger of brain hyperthermia.

Aged↗
PubMed1997

Glucose management in the infant under six kilograms.

A retrospective, nonrandomized study of blood glucose levels in very young children under 6 kg was undertaken. Each patient underwent the repair of complex congenital heart defects using hypothermia and nonpulsatile cardiopulmonary bypass (CPB). Hyperglycaemia may cause metabolic changes, resulting in reduced glucose transport and cerebral ischaemia. To evaluate the frequency of the occurrence of hyperglycaemia, samples were evaluated for glucose levels in three groups of patients. Group 1 (n = 5) consisted of infants undergoing standard bypass and moderate hypothermia (26 degrees C). Group 2 (n = 5) were infants undergoing low-flow bypass and profound hypothermia (20 degrees C). Group 3 (n = 5) was comprised of infants undergoing total circulatory arrest and profound hypothermia (18 degrees C). Glucose samples were taken preoperatively, during hypothermic bypass, during rewarming and 1-h postoperatively. In group 1, blood glucose levels remained within the normal range (65-100 mg/dl) throughout bypass and in the 1-h postoperative sample. In group 2, blood glucose levels remained within the normal range preoperatively and during the hypothermic bypass period. However, during the rewarming period, the glucose level rose to 185 +/- 17.2 mg/dl. The 1-h postoperative level was also increased to 168 +/- 16.5 mg/dl. Group 3, like group 2, showed that the preoperative and hypothermic glucose values were within the normal range and the rewarming, 133 +/- 29.4, and the 1 h, 130 +/- 33.3 mg/dl, glucose values were hyperglycaemic. This study indicates that blood glucose levels should be monitored routinely, both during and after CPB.

Blood Glucose↗
PubMed2002

The relationship between mixed venous and regional venous oxygen saturation during cardiopulmonary bypass.

The relationship between mixed venous and regional venous saturation during cardiopulmonary bypass (CPB), and whether this relationship is influenced by temperature, has been incompletely elucidated. Thirty patients undergoing valve and/or coronary surgery were included in a prospective, controlled and randomized study. The patients were allocated to two groups: a hypothermic group (28 degrees C) and a tepid group (34 degrees C). Blood gases were analysed in blood from the hepatic vein and the jugular vein and from mixed venous blood collected before surgery, during hypothermia, during rewarming, and 30 min after CPB was discontinued. Oxygen saturation in the hepatic vein was lower than in the mixed venous blood at all times of measurement (-24.0 +/- 3.0% during hypothermia, -36.5 +/- 2.9% during rewarming, and -30.5 +/- 3.0% postoperatively, p < 0.001 at all time points). In 23% of the measurements, the hepatic saturation was <25% in spite of normal (>60%) mixed venous saturation. There was a statistical correlation between mixed venous and hepatic vein oxygen saturation (r=0.76, p < 0.0001). Jugular vein oxygen saturation was lower than mixed venous saturation in all three measurements (-21.6 +/- 1.9% during hypothermia, p < 0.001; -16.7 +/- 1.9% during rewarming, p < 0.001; and -5.6 +/- 2.2% postoperatively, p = 0.037). No significant correlation in oxygen saturation could be detected between mixed venous and jugular vein blood (r = 0.06, p = 0.65). Systemic temperature did not influence the differences in oxygen saturation between mixed venous and regional venous blood at any time point. In conclusion, regional deoxygenation occurs during CPB, in spite of normal mixed venous saturation. Mixed venous oxygen saturation correlates with hepatic, but not with jugular, vein saturation. The level of hypothermia does not influence differences in oxygen saturation between mixed venous and regional venous blood.

Aged↗
PubMed2005

Comparison of hollow-fiber membrane oxygenators in terms of pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass in neonates.

UNLABELLED: The objective of this study was to investigate the effects of two hollow-fiber membrane oxygenators, the Capiox SX10 and the Lilliput 901, on pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass (CPB) in neonates. METHODS: Twenty-six congenital heart surgery patients (n = 13 in each group) with a mean weight of 3 kg were included in this study. Pressure drops of the membranes, pre- and post-oxygenator extracorporeal circuit pressures (ECC) were recorded during normothermic CPB, hypothermic CPB (20 degrees C) and after rewarming. There were no differences between the groups in mean arterial pressure, pump flow rate, temperature, duration of CPB, crossclamp time or the severity of the surgical repairs. RESULTS: Pressure drop of the Capiox SX10 oxygenator was significantly lower during normothermic (32 +/- 10 versus 55 +/- 16 mmHg, p < 0.001), hypothermic (38 +/- 15 versus 72 +/- 18 mmHg, p < 0.001) and post-rewarming (42 +/- 13 versus 72 +/- 21 mmHg, p < 0.001) periods compared to the Lilliput oxygenator. In the Capiox group, the pre-oxygenator ECC pressure was also significantly lower during normothermic CPB (142 +/- 27 versus 184 +/- 43 mmHg, p < 0.01), hypothermic CPB (162 +/- 30 versus 199 +/- 38 mmHg, p < 0.01) and after rewarming periods (172 +/- 32 versus 212 +/- 42 mmHg, p < 0.01). Post-oxygenator pressures in the Capiox group were also lower than in the Lilliput group, but results were not statistically significant. CONCLUSIONS: These results suggest that the Capiox SX10 hollow-fiber membrane oxygenator produced significantly lower membrane pressure drops and pre- and post-oxygenator ECC during normothermic and hypothermic CPB. Thus, blood trauma with the Capiox during extracorporeal circulation may be significantly lower compared to the Lilliput. Further studies, including the level of complements, platelets, neutrophils and cytokines, with these oxygenators are warranted.

Blood Flow Velocity↗
PubMed1983

Effect of environmental hypothermia on dorsal aortic blood flow in the chick embryo, stages 18 to 24.

Dorsal aortic blood flow was measured with a pulsed-Doppler meter in Hamburger-Hamilton stage 18, 21, and 24 chick embryos, and stroke volume index was calculated by dividing mean blood flow per minute by heart rate. These parameters were measured at baseline temperature 34.7 degrees C after cooling to 31.1 degrees C and subsequent rewarming to 34.2 degrees C. In stage 21 embryos, after environmental cooling, heart rate decreased from 170 bpm to 118 bpm (P less than 0.01), mean dorsal aortic blood flow decreased from 0.38 mm3/sec to 0.24 mm3/sec (P less than 0.01) but stroke volume index did not change [baseline, 0.13 mm3/beat; after cooling, 0.12 mm3/beat; after rewarming, 0.15 mm3/beat (P = N.S.)]. Similar results were observed in stage 18 and 24 embryos. The bradycardic response to environmental hypothermia was independent of functional autonomic innervation and probably mediated by a direct suppression of cell action potential dv/dt. Myocardial cell function was not adversely affected by an acute change in environmental temperature as the index of stroke volume was not altered, and all parameters returned rapidly to baseline with rewarming.

Action Potentials↗
PubMed1992

Clinical evaluation of cerebral oxygen balance during cardiopulmonary bypass: on-line continuous monitoring of jugular venous oxyhemoglobin saturation.

To prevent brain damage during cardiopulmonary bypass (CPB), adequate cerebral perfusion for cerebral oxygen demand should be maintained. We monitored jugular venous oxyhemoglobin saturation (SjO2), which reflects the overall balance of cerebral oxygen supply and demand, continuously in 12 patients undergoing cardiac surgery. We examined whether this balance is disrupted during CPB, and if so, analyzed critical factors that affect this phenomenon. At the initiation of CPB, in spite of a significant decrease in mean arterial pressure, SjO2 did not change, and it was stable during the hypothermic period of CPB. On the other hand, a significant reduction in SjO2 was observed during the rewarming period, and SjO2 had an inverse linear correlation with nasopharyngeal temperature. Furthermore, the percent decrease of SjO2 was significantly related to "rewarming speed" (an average increase in temperature per minute). Our results indicate that temperature change during the rewarming period is a critical factor affecting the balance of cerebral oxygen supply and demand during CPB.

Adult↗
PubMed1993

The effect of perfusion flow on oxidative metabolism during cardiopulmonary bypass.

The influence of perfusion flow rate on whole-body oxygen consumption (VO2), central venous hemoglobin oxygen saturation (SVO2), and central venous arterial oxygen tension (PVO2) during hypothermic hemodilutional nonpulsatile cardiopulmonary bypass was investigated in 20 patients undergoing coronary artery bypass grafting. In 10 patients, the perfusion flow was 2.4 L.min-1 x m-2 (Group I), whereas a flow of 1.2 L.min-1 x m-2 was used in the other 10 patients (Group II). When the body temperature was 29.7 +/- 1.2 degrees C (Group I) and 29.6 +/- 0.8 degrees C (Group II), mixed venous and arterial blood were sampled simultaneously, and whole-body oxygen consumption was calculated. Data collected during hypothermia were compared with the corresponding values achieved after rewarming to 37 degrees C. In both groups, the whole-body oxygen consumption during hypothermia was lower by about 45% than the VO2 after rewarming. However, SVO2 during the low perfusion flow was not significantly different from SVO2 after rewarming, whereas the temperature-corrected PVO2 was significantly lower. In contrast, the high-perfusion flow provided luxury perfusion as evident by the high SVO2, and maintained the temperature-corrected PVO2 within the normothermic range. Thus, maintenance of the normothermic perfusion flow rate during moderate hypothermic hemodilutional cardiopulmonary bypass may provide a safety margin that may compensate for unexpected increase of oxygen consumption or decrease of oxygen delivery.

Aged↗
PubMed2005

The effect of mild hypothermia on plasma fentanyl concentration and biotransformation in juvenile pigs.

Therapeutic hypothermia may alter the required dosage of analgesics and sedatives, but no data are available on the effects of mild hypothermia on plasma fentanyl concentration during continuous, long-term administration. We therefore assessed in a porcine model the effect of prolonged hypothermia on plasma fentanyl concentration during 33 h of continuous fentanyl administration. Seven female piglets (weight: 11.8 +/- 1.1 kg) were anesthetized by IV fentanyl (15 microg . kg(-1) . h(-1)) and midazolam (1.0 mg . kg(-1) . h(-1)). After preparation and stabilization (12 h), the animals were cooled to a core temperature of 31.6 degrees +/- 0.2 degrees C for 6 h and were then rewarmed and kept normothermic at 37.7 degrees +/- 0.3 degrees C for 6 more hours. Plasma fentanyl concentrations were measured by radioimmunoassay, cardiac index by thermodilution, and blood flows of the kidney, spleen, pancreas, stomach, gut, and hepatic artery by a colored microspheres technique. Furthermore, in an additional 4 pigs, temperature dependency of hepatic microsomal cytochrome P450 3A4 (CYP3A4) was determined in vitro by ethylmorphine N-demethylation. Plasma fentanyl concentration increased by 25% +/- 11% (P < 0.05) during hypothermia and remained increased for at least 6 h after rewarming. Hypothermia reduced the cardiac index (41% +/- 15%, P < 0.05), as well as all organ blood flows except the hepatic artery. A strong temperature dependency of CYP3A4 was found (P < 0.01). Mild hypothermia induced a distribution and/or elimination-dependent increase in plasma fentanyl concentration which remained increased for several hours after rewarming. Consequently, a prolonged increase of the plasma fentanyl concentration should be anticipated for appropriate control of the analgesia/sedatives during and early after therapeutic hypothermia.

Analgesics, Opioid↗
PubMed2004

Comparison of endovascular and surface cooling during unruptured cerebral aneurysm repair.

OBJECTIVE: To compare endovascular versus surface methods for the induction and reversal of hypothermia during neurosurgery in a multicenter, prospective, randomized study. METHODS: Patients undergoing elective open craniotomy for repair of an unruptured cerebral aneurysm (n = 153) were randomly assigned (2:1) to undergo whole-body hypothermia to 33 degrees C, either with an endovascular cooling device placed in the inferior vena cava via the femoral vein (n = 92) or with a surface convective air blanket (n = 61). Active rewarming was accomplished using the same devices. RESULTS: Cooling rates in endovascular and surface blanket groups averaged 4.77 and 0.87 degrees C/h, respectively (P < 0.001). When the first temporary arterial or aneurysm clip was placed, 99% of endovascular patients and 20% of surface blanket patients had reached the target of 33 degrees C (P < 0.001). Obese patients were cooled efficiently with the endovascular approach (3.56 degrees C/h). Rewarming rates averaged 1.88 degrees C/h for endovascular patients and 0.69 degrees C/h for surface blanket patients (P < 0.001). By the end of surgery, 89 and 53% of these patients, respectively, had rewarmed to at least 35 degrees C (P < 0.001). On leaving the operating room, 14% of endovascular patients and 28% of surface blanket patients were still intubated (P = 0.035). The overall safety of the two procedures was comparable. No clinically significant catheter-related thrombotic, bleeding, or infectious complications were reported in the endovascular group. CONCLUSION: Endovascular cooling provided superior induction, maintenance, and reversal of hypothermia compared with the surface blanket, without an increase in complications. Endovascular cooling may have clinical benefit for patients undergoing cerebrovascular surgery, as well as patients with acute stroke, head injury, or acute myocardial infarction.

Adolescent↗
PubMed2005

Phase II clinical trial of moderate hypothermia after severe traumatic brain injury in children.

OBJECTIVE: To determine whether moderate hypothermia (HYPO) (32-33 degrees C) begun in the early period after severe traumatic brain injury (TBI) and maintained for 48 hours is safe compared with normothermia (NORM) (36.5-37.5 degrees C). METHODS: After severe (Glasgow Coma Scale score < or =8) nonpenetrating TBI, 48 children less than 13 years of age admitted within 6 hours of injury were randomized after stratification by age to moderate HYPO (32-33 degrees C) treatment in conjunction with standardized head injury management versus NORM in a multicenter trial. An additional 27 patients were entered into a parallel single-institution trial of excluded patients because of late transfer or consent (delayed in transfer >6 h but within 24 h of admission), unknown time of injury (e.g., child abuse), and adolescence (e.g., aged 13-18 yr). Assessments of safety included mortality, infection, coagulopathy, arrhythmias, and hemorrhage as well as ability to maintain target temperature, mean intracranial pressure (ICP), and percent time of ICP less than 20 mm Hg during the cooling and subsequent rewarming phases. Additionally, assessments of neurocognitive outcomes were obtained at 3 and 6 months of follow-up. RESULTS: Moderate HYPO after severe TBI in children was found to be safe relative to standard management and NORM in children of all ages and in children with delay of initiation of treatment up to 24 hours. Although there was decreased mortality in HYPO in both studies, there was an increased potential for arrhythmias with HYPO, although they were manageable with fluid administration or rewarming. Additionally, there was a reduction in mean ICP during the first 72 hours after injury in both studies, although rebound ICP elevations in HYPO compared with those in NORM were noted for up to 10 to 12 hours after rewarming. Although functional outcome at 3 or 6 months did not differ between treatment groups, functional outcome tended to improve from the 3- to 6-month cognitive assessment in HYPO compared with NORM, although the sample size was too small for any definitive conclusions. CONCLUSION: HYPO is likely a safe therapeutic intervention for children after severe TBI up to 24 hours after injury. Further studies are necessary and warranted to determine its effect on functional outcome and intracranial hypertension.

Adolescent↗
PubMed1998

The recycling pathway of protein ERGIC-53 and dynamics of the ER-Golgi intermediate compartment.

To establish recycling routes in the early secretory pathway we have studied the recycling of the ER-Golgi intermediate compartment (ERGIC) marker ERGIC-53 in HepG2 cells. Immunofluorescence microscopy showed progressive concentration of ERGIC-53 in the Golgi area at 15 degreesC. Upon rewarming to 37 degreesC ERGIC-53 redistributed into the cell periphery often via tubular processes that largely excluded anterograde transported albumin. Immunogold labeling of cells cultured at 37 degreesC revealed ERGIC-53 predominantly in characteristic beta-COP-positive tubulo-vesicular clusters both near the Golgi apparatus and in the cell periphery. Concentration of ERGIC-53 at 15 degreesC resulted from both accumulation of ERGIC-53 in the ERGIC and movement of ERGIC membranes closer to the Golgi apparatus. Upon rewarming to 37 degreesC the labeling of ERGIC-53 in the ERGIC rapidly returned to normal levels whereas ERGIC-53's labeling in the cis-Golgi was unchanged. Temperature manipulations had no effect on the average number of ERGIC-53 clusters. Density gradient centrifugation indicated that the surplus ERGIC-53 accumulating in the ERGIC at 15 degreesC was rapidly transported to the ER upon rewarming. These results suggest that the ERGIC is a dynamic membrane system composed of a constant average number of clusters and that the major recycling pathway of ERGIC-53 bypasses the Golgi apparatus.

Albumins↗
PubMed2004

Technical refinements and drawbacks of a surface cooling technique for the treatment of severe acute ischemic stroke.

PURPOSE: To describe a technique for the induction of hypothermia and its complications for the treatment of acute ischemic stroke. METHODS: Adults with acute (<8 hours), severe (National Institutes of Health Stroke Scale>14) ischemic stroke of the anterior circulation were enrolled. Patients were intubated, sedated, and paralyzed. Surface cooling to 32 degrees+/-1 degrees C was performed with a cooling blanket and an alcohol/ice bath. Hypothermia was maintained for 12-72 hours. Physiological parameters were measured continuously. A computed tomography scan of the brain was obtained at 24 hours. Rewarming was initiated 12 hours after middle cerebral artery recanalization at a rate of 0.25 degrees C/hour. All complications and adverse outcomes were documented from initiation of hypothermia until hospital discharge. RESULTS: Eighteen patients with a mean National Institutes of Health Stroke Scale=21.4+/-5.6 were treated. The goal temperature was reached within 3.2+/-1.5 hours. Cooling time was proportional to body weight (p=0.009) and decreased with immediate paralysis to prevent shivering (p=0.033). Maintenance and rewarming were characterized by fluctuations in core temperature. All patients developed a decrease in blood pressure, heart rate, and potassium values that were proportional to temperature (p<0.05). Complications were generally mild, but pneumonia and myocardial infarction or both occurred in five patients. There were trends for increased risk of complications with longer duration of hypothermia (p=0.08) and increasing age (p=0.0504). Rewarming was well-tolerated with rebound cerebral edema occurring in only one patient. CONCLUSION: Surface cooling for the treatment of acute ischemic stroke can be performed rapidly with early neuromuscular paralysis. Advanced age and prolonged hypothermia may be associated with an increased risk of complications.

Adult↗
PubMed1986

Calcium transport in diluted or cooled ram semen.

Ram semen was subjected to various dilution rates and temperatures of dilution, and was also subjected to slow cooling and rewarming. Calcium ion movements across sperm membranes were measured using the radioisotope 45Ca2+. It was shown that even 2- to 4-fold dilution caused an increase in intracellular calcium content. An increase in intracellular calcium also occurred in proportion to a decreased temperature of dilution. After an initial increase in intracellular calcium content, spermatozoa appeared able to restore a low intracellular calcium level over a period of 2 h at 22 degrees C or above. This ability was lost at 16 degrees C or below. However, if undiluted semen was slowly cooled (0.125 degrees C/min) even to 5 degrees C and rewarmed to 22 degrees C before dilution, the spermatozoa regained this ability. In contrast, spermatozoa rapidly cooled to 5 degrees C and rewarmed to 22 degrees C before dilution were not able to restore the low intracellular calcium level.

Animals↗
PubMed2006

Profound hypothermic cardiac arrest treated successfully using minimally invasive cardiopulmonary bypass: a case report.

BACKGROUND: Hypothermia is defined as a core temperature of less than 35 degrees C. The decision to resuscitate a hypothermic patient can be difficult, as consideration must be given to whether the patient died before the cooling process. The modality for rewarming must also be considered. CASE REPORT: A severely hypothermic 54-year-old man with a core temperature of 21 degrees C was successfully rewarmed using cardiopulmonary bypass via the femoro-femoral route. The patient made a full neurological recovery. CONCLUSION: Cardiopulmonary bypass provides excellent circulatory support for profound hypothermia and allows rapid core rewarming. The femoro-femoral approach is the preferred method for this scenario.

Cardiopulmonary Resuscitation↗
PubMed1985

Frontal subcutaneous blood flow, and epi- and subcutaneous temperatures during scalp cooling in normal man.

Cooling of the scalp has been found to prevent hair loss following cytostatic treatment, but in order to obtain the hair preserving effect the subcutaneous temperature has to be reduced below 22 degrees C. In order to establish the relationship between epicutaneous and subcutaneous temperatures during cooling and rewarming and to measure the effect of scalp cooling on subcutaneous scalp blood flow, subcutaneous blood flow and epi- and subcutaneous temperatures were measured in the frontal region at the hairline border before and during cooling with a cooling helmet, during spontaneous rewarming of the cooling helmet and after removal of the rewarmed helmet in 10 normal subjects. Subcutaneous blood flow was reduced to about 25% of the postcooling control level during cooling. The flow was constantly reduced until the subcutaneous temperature exceeded 30-32 degrees C. A linear relationship between epicutaneous and subcutaneous temperatures could be demonstrated with the regression equation: s = 0.9 c + 4.9 (r = 0.99). In eight of the 10 subjects the subcutaneous temperature could be reduced below 22 degrees C with the applied technique. It is concluded that the hair preserving effect of scalp cooling during cytostatic treatment is mainly due to the metabolic effect of cooling, and only to a minor extent due to the flow reducing effect.

Adult↗
PubMed1998

The influence of body temperature on transient evoked otoacoustic emissions.

Thirty patients undergoing open heart surgery under induced hypothermia had transient evoked otoacoustic emissions (TEOAE) recorded during cooling to 26.07 degrees C (standard deviation (SD) 4.25 degrees C) vesically measured temperature and 24.86 degrees C (SD 4.7 degrees C) nasopharyngeally measured temperature respectively. Subsequently tè patients were rewarmed until normal body temperature was reached again. There was a clear influence of body temperature on the amplitudes and reproducibilities of the TEOAE. The relationship of temperature and amplitude or reproducibility during the cooling phase was significantly different from that during rewarming. No TEOAE were measurable during cooling at a mean temperature lower than 33.41 degrees C (SD 2.04 degrees C) vesical temperature and 30.16 degrees C (SD 3.0 degrees C) nasopharyngeal temperature respectively. During rewarming the echoes became recognizable again at a mean temperature of 28.75 degrees C (SD 3.38 degrees C) vesical temperature and 27.49 degrees C (SD 2.99 degrees C) nasopharyngeal temperature. These results suggest a hysteresis in the relationship between the amplitude of TEOAE and temperature, similar to the well-established relationship between evoked potentials and temperature.

Adolescent↗