Exercise in a hot environment: the skin circulation

The combined metabolic and thermoregulatory demands of exercise in the heat place an exceptional burden on the circulation, more than can be met through cardiac output and blood flow redistribution. Blood flow to muscle is not reduced by heat stress in exercise and cardiac output is insufficient to meet competing demands from skin and muscle. Skin blood flow during exercise in the heat is limited in several ways. Dynamic exercise causes a cutaneous vasoconstriction at exercise onset through increased vasoconstrictor activity, both in cool and warm conditions. As exercise continues, internal temperature reaches a threshold for increased active vasodilator activity that is elevated by exercise, but reduced by high skin temperature. Beyond that threshold, skin blood flow is limited well below what would be achieved at rest with the same thermal drive through a limit to the active vasodilator system. This combination of restraints on cutaneous vasodilator function compromises temperature regulation. Internal temperature rises to levels that limit exercise through central thermal effects, rather than loss of blood pressure or a reduction in blood flow to active muscle.     

Effect of fluid intake volume on 2-h running performances in a 25 degrees C environment

PURPOSE: In this study, we examined the effects of greater than ad libitum rates of fluid intake on 2-h running performances. METHODS: Eight male distance runners performed three runs on a treadmill at 65% of peak oxygen uptake (VO2peak) for 90 min and then ran "as far as possible" in 30 min in an air temperature of 25 degrees C, a relative humidity of 55% and a wind speed of 13-15 km x h(-1). During the runs, the subjects drank a 6.9% carbohydrate (CHO)-electrolyte solution either ad libitum or in set volumes of 150 or 350 mL x 70 kg(-1) body mass (approximately 130 or 300 mL) every 15-20 min. RESULTS: Higher (approximately 0.9 vs 0.4 L x h(-1)) rates of fluid intake in the 350 mL x 70 kg(-1) trial than in the other trials had minimal effects on the subjects' urine production (approximately 0.1 L x h(-1)), sweat rates (approximately 1.2 L x h(-1)), declines in plasma volume (approximately 8%), and rises in serum osmolality (approximately 5 mosmol x L(-1)) and Na+ concentrations (approximately 7 mEq x L(-1)). A greater (approximately 1.0 vs 0.5 g x min(-1)) rate of CHO ingestion in the 350 mL x 70 kg(-1) trial than in the other trials also did not affect plasma concentrations of glucose (> or = 5 mmol x L(-1)) and lactate (approximately 3 mmol x L(-1)) during the performance runs. In all three performance runs, increases in running speeds from approximately 14 to 15-16 km x h(-1) and rises in exercise intensities from approximately 65% to 75% of VO2peak elevated plasma lactate concentrations from approximately 1.5 to 3 mmol x L(-1) and accelerated CHO oxidation from approximately 13 to 15 mmol x min(-1). The only effect of the additional intake of approximately 1.0 L of fluid in the 350 mL x 70 kg(-1) trial was to produce such severe gastrointestinal discomfort that two of the eight subjects failed to complete their performance runs. CONCLUSION: Greater rates of fluid ingestion had no measurable effects on plasma volume and osmolality and did not improve 2-h running performances in a 25 degrees C environment.     

Infrared tympanic thermometry in a hot environment

The purpose of this study was to compare tympanic (measured by infrared thermometry; Tty- (IRED)) with rectal and esophageal temperatures (T (REC) and T (ES)) during exercise in the heat. During Experiment 1, nine subjects pedaled for 55 min in a hot-dry environment (37 degrees C; 27 % humidity) in still-air (< 0.2 m/s) and for 10 additional min using water ingestion, wind and ice to cool them down. During Experiment 2, subjects pedaled for 90 min in a similar environment but with airflow at 2.5 m/s. Pearson correlation coefficients (r) and Bland-Altman plots were calculated. In Experiment 1, Tty- (IRED) and T (REC) were highly correlated (r = 0.83; p < 0.001) with close agreement (- 0.08 +/- 0.4 degrees C). Overall Tty- (IRED) was significantly correlated with T (ES) (r = 0.91; p < 0.001). Cold water ingestion did not affect Tty- (IRED) or T (REC) but lowered T (ES). Wind and ice application lowered Tty- (IRED) below T (REC) (p < 0.05). During Experiment 2, Tty- (IRED) was lower than T (REC) (p < 0.05) and the difference increased throughout exercise as hyperthermia developed resulting in low agreement (- 1.01 +/- 1.1 degrees C). In conclusion, Tty- (IRED) dangerously underestimates T (REC) when exercising in a hot environment with airflow or during a cooling treatment. However, it could correctly detect hyperthermia during exercise in a hot still-air environment.     

Sweat rate and fluid turnover in American football players compared with runners in a hot and humid environment

Objectives: To determine sweat rate (SwR) and fluid requirements for American footballers practicing in a hot, humid environment compared with cross country runners in the same conditions.

Methods: Fifteen subjects, 10 footballers and five runners, participated. On the 4th and 8th day of preseason two a day practices, SwR during exercise was determined in both morning and afternoon practices/runs from the change in body mass adjusted for fluids consumed and urine produced. Unpaired t tests were used to determine differences between groups.

Results: Overall SwR measured in litres/h was higher in the footballers than the cross country runners (2.14 (0.53) v 1.77 (0.4); p<0.01). Total sweat loss in both morning (4.83 (1.2) v 1.56 (0.39) litres) and afternoon (4.8 (1.2) v 1.97 (0.28) litres) practices/runs, and daily sweat losses (9.4 (2.2) v 3.53 (0.54) litres) were higher in the footballers (p<0.0001). The footballers consumed larger volumes of fluid during both morning and afternoon practices/runs (23.9 (8.9) v 5.5 (3.1) ml/min and 23.5 (7.3) v 13.6 (5.6) ml/min; p<0.01). For complete hydration, the necessary daily fluid consumption calculated as 130% of daily sweat loss in the footballers was 12.2 (2.9) litres compared with 4.6 (0.7) litres in the runners (p<0.0001). Calculated 24 hour fluid requirements in the footballers ranged from 8.8 to 19 litres.

Conclusions: The American footballers had a high SwR with large total daily sweat losses. Consuming large volumes of hypotonic fluid may promote sodium dilution. Recommendations for fluid and electrolyte replacement must be carefully considered and monitored in footballers to promote safe hydration and avoid hyponatraemia.

     

全子宫切除手术两种不同手术方式的比较

目的比较腹腔镜全子宫切除术（TLH）及腹腔镜辅助阴式全子宫切除术（LAVH）两种手术方式的效果。方法收集我院2013年1月-2014年6月收治的子宫肌瘤行TLH的患者50例（TLH组）和行LAVH的患者50例（LAVH组）的临床资料,比较两组手术时间、术中出血量、肛门排气时间、术后最高体温、住院时间及伤口愈合情况。结果TLH组手术时间、术中出血量、术后最高体温均低于LAVH组（P〈0．05）,而两组肛门排气时间、住院时间、伤口愈合情况相比,无统计学差异（P〉0．05）。结论TLH术中出血量少,患者术后反应轻,手术安全、可行,但必须熟练掌握镜下缝合技术。     

Whole-body MRI of multiple myeloma: comparison of different MRI sequences in assessment of different growth patterns

Purpose

To determine sensitivity, specificity and inter-observer variability of different whole-body MRI (WB-MRI) sequences in patients with multiple myeloma (MM).

Methods and materials

WB-MRI using a 1.5 T MRI scanner was performed in 23 consecutive patients (13 males, 10 females; mean age 63 ± 12 years) with histologically proven MM. All patients were clinically classified according to infiltration (low-grade, n = 7; intermediate-grade, n = 7; high-grade, n = 9) and to the staging system of Durie and Salmon PLUS (stage I, n = 12; stage II, n = 4; stage III, n = 7). The control group consisted of 36 individuals without malignancy (25 males, 11 females; mean age 57 ± 13 years). Two observers independently evaluated the following WB-MRI sequences: T1w-TSE (T1), T2w-TIRM (T2), and the combination of both sequences, including a contrast-enhanced T1w-TSE with fat-saturation (T1 ± CE/T2). They had to determine growth patterns (focal and/or diffuse) and the MRI sequence that provided the highest confidence level in depicting the MM lesions. Results were calculated on a per-patient basis.

Results

Visual detection of MM was as follows: T1, 65% (sensitivity)/85% (specificity); T2, 76%/81%; T1 ± CE/T2, 67%/88%. Inter-observer variability was as follows: T1, 0.3; T2, 0.55; T1 ± CE/T2, 0.55. Sensitivity improved depending on infiltration grade (T1: 1 = 60%; 2 = 36%; 3 = 83%; T2: 1 = 70%; 2 = 71%; 3 = 89%; T1 ± CE/T2: 1 = 50%; 2 = 50%; 3 = 89%) and clinical stage (T1: 1 = 58%; 2 = 63%; 3 = 79%; T2: 1 = 58%; 2 = 88%; 3 = 100%; T1 ± CE/T2: 1 = 50%; 2 = 63%; 3 = 100%). T2w-TIRM sequences achieved the best reliability in depicting the MM lesions (65% in the mean of both readers).

Conclusions

T2w-TIRM sequences achieved the highest level of sensitivity and best reliability, and thus might be valuable for initial assessment of MM. For an exact staging and grading the examination protocol should encompass unenhanced and enhanced T1w-MRI sequences, in addition to T2w-TIRM.     

Examination of fatigue development in elite soccer in a hot environment: a multi-experimental approach

The study examines fatigue in elite soccer played in hot conditions. High-profile soccer players (n=20) were studied during match play at ～31 °C. Repeated sprint and jump performances were assessed in rested state and after a game and activity profile was examined. Additionally, heart rate (HR), blood lactate, muscle temperature and body mass changes were determined. Repeated sprint and jump performances were reduced (P<0.05) by 2.6% and 8.2%, respectively, after the game. The fatigue index in the repeated sprint test was 6.0±0.7% after the game compared with 1.7±1.0% at rest (P<0.05). High-intensity running was 57±4% lower (P<0.05) during the last 15-min interval of the game compared with the first 15-min period. No differences were observed in mean HR or blood lactates between halves. Muscle temperature was 40.5±0.4 °C after the first half, which was 0.8±0.2 °C higher (P<0.05) than after the second half. Net fluid loss during the game was >2% of the body mass. Correlations were observed between net-fluid loss and repeated sprint test fatigue index after the game (r=0.73, P<0.05) and Yo-Yo intermittent recovery, level 1 test performance and high-intensity running during the final 15 min of the game (r=0.51, P<0.05). The study provides direct evidence of compromised repeated sprint and jump performances induced by soccer match play and pronounced reduction in high-intensity running toward the end of an elite game played in a hot environment. This fatigue could be associated training status and hyperthermia/dehydration.     

Diffusion weighted imaging in breast MRI: comparison of two different pulse sequences

RATIONALE AND OBJECTIVES: Comparison of two different diffusion weighted (DW) sequences in breast MRI regarding the differentiation between benign and malignant lesions. MATERIALS AND METHODS: Breast MRI including two different DW sequences was performed in 165 consecutive women. Inclusion criteria for DW imaging and ADC evaluation were histologically proven focal mass lesions with a diameter of more than 5 mm in dynamic contrast-enhanced MRI. The DW sequences were pre-contrast echo-planar imaging with spectral fat saturation (EPI fs) and DW EPI with inversion recovery (EPI STIR) (b-values: 50, 400, and 800). Lesions were analyzed regarding visibility in DW sequences and ADC values. RESULTS: Inclusion criteria were fulfilled in 56 women with 69 lesions. Five lesions could not be evaluated for different reasons. Finally, DW sequences were evaluated in 51 women with 64 focal mass lesions (15 benign, 49 malignant). The visibility of the lesions was significantly better in the EPI fs sequence (P<0.05). The ADC values (10(-3) mm(2)/s) in the EPI fs were 1.76, 2.58, and 1.21 (mean, maximum, minimum, respectively) for benign lesions and 0.90, 1.19, and 0.34 for malignant lesions. Respective values in the EPI STIR sequence were 1.92, 3.20, 1.10, and 0.91, 1.43, 0.35. Only in the EPI fs sequence there was no overlap in ADC values between benign and malignant lesions. CONCLUSION: The DW MRI of the breast with EPI fs and EPI STIR sequences has a high potential to differentiate between benign and malignant breast lesions. Due to better lesion visibility and selectivity, the EPI fs sequence should be preferred.     

Biomedical cost of low-level flight in a hot environment.

The physiologic and performance effects of low-level reconnaissance flying in hot environments were documented and quantitated. RF-4C pilots and weapons system operators were studied in hot and cool seasons during both high and low missions to distinguish environmental temperature from flight level effects. ECG, sternal and thigh skin temperatures, and cockpit temperature at helmet level were monitored continuously. Body weights, oral temperatures, sweat Na/K ratios, and urine electrolytes, steroids, and catecholamines, as well as sleep and fatigue scores, were measured. Mission performance was assessed using photo target acquisition scores. RF-4C aircrews are exposed to moderate heat stress and acute dehydration (1.2% over 90 min) during low-level summer flights were cockpit temperature occasionally exceeded 50 degrees C. Photo target scores indicated that the potential for crew error was increased, and that the margin of safety was accordingly decreased, during such hot missions. The RF-4C cockpit air conditioning system proved inadequate.     

Postoperative functional rehabilitation after repair of quadriceps tendon ruptures: a comparison of two different protocols

Purpose

Early functional rehabilitation after surgical tendon repair facilitates the healing process and leads to improved joint function. There is a paucity of studies commenting on rehabilitation after surgical repair of ruptured quadriceps tendons, and most surgeons prefer a prolonged period of immobilization and protected weight bearing. The purpose of the present study is to compare the clinical outcome after a more functional and after a rather restrictive postoperative rehabilitation protocol.

Methods

All consecutive patients were included who had a surgical repair of a primary unilateral quadriceps tendon rupture in one of the two participating hospitals and a minimum follow-up of 24 months. Patients of site A were only allowed limited flexion and weight bearing while patients from site B were allowed early functional rehabilitation with full weight bearing. Clinical outcome was measured with the subjective IKDC form. Fisher’s exact test and Mann–Whitney U test were used for statistical analysis.

Results

Sixty-six patients were included in the study. Twenty-eight patients (Group A) were treated with restrictive and 38 patients (Group B) with early functional postoperative rehabilitation. The two groups did not differ in terms of demographic characteristics. Clinical follow-up was available for 95% of patients after an average of 4.5 years. No clinical difference was identified with the use of IKDC form. Patients of group A returned to work an average of 10 days later than patients from group B, but this difference was not significant. Two re-ruptures were observed in each group. There was no significant difference in terms of complication quality or quantity.

Conclusion

Early functional postoperative mobilization with full weight bearing after primary repair of a quadriceps tendon rupture is safe and will not lead to inferior clinical outcome or an increased complication rate.

Level of evidence

Therapeutic, III.     

Assessment of vascular physiology of tumorous livers: comparison of two different methods

RATIONALE AND OBJECTIVES: To evaluate liver and liver tumor perfusions by using two different modelling methods: gamma-variate fitting and a single-compartment model. MATERIALS AND METHODS: 5 New Zealand White rabbits with VX2 tumor implanted into the liver via portal injections were studied. Contrast-enhanced functional CT (fCT) examinations with temporal resolution of 200-500 milliseconds were conducted before tumor inoculation. Thereafter, two or three follow-up studies were conducted. A gamma-variate fitting method was used to determine fractional blood volumes (BV), and a single-compartment model method was used to determine fractional blood volumes (BV), blood flows (BF), and mean transit times (MTT) for normal and tumorous liver regions. RESULTS: For tumorous regions in liver, the gamma-variate fitting and the single-compartment model methods showed statistically significant increases in arterial perfusions (P < 0.01) and decreases in portal perfusions (P < 0.01 with single-compartment model, and P < 0.05 with gamma-variate fitting) when compared with normal liver regions. The single-compartment model showed statistically significant increases (P < 0.01) in MTTs in tumorous regions. In normal liver regions, portal BFs decreased and MTTs increased after tumor inoculation, but the changes were statistically not significant. CONCLUSION: The gamma-variate fitting and the single-compartment model methods showed definite differences in perfusions between normal and tumorous regions in liver. The single-compartment model showed slightly more distinction and was faster. More importantly, both methods can easily be applied in the clinical environment in the assessment of liver perfusion.     

Exercise tolerance in a hot and humid climate in heat-acclimatized girls and women

This study compared physiological responses associated with exercise tolerance in girls (G) and women (W) of similar fitness and heat acclimatization level during exercise in a hot and humid outdoor environment (33.4 degrees C and 55.1 % RH; WBGT = 29.9 +/- 0.2 degrees C). Nine pre-menarcheal G (age = 11.3 yr) and nine W (age = 26.8 yr), matched for aerobic capacity and heat acclimatization level, performed a cycling session at 60 % VO2max until fatigue. A sports drink was provided periodically to prevent dehydration. Tolerance time was not different between the groups (G = 56.9 +/- 6.3, W = 76.5 +/- 9.9 min, p > 0.05). During exercise, sweat rate (G = 9.1 +/- 1.1, W = 12.0 +/- 1.1 ml.m(-2).min(-1)), the increase in rectal temperature [T(re)] (G = 0.9 +/- 0.1, W = 1.1 +/- 0.1 degrees C), and heat storage (G = 10.6 +/- 5.3, W = 20.5 +/- 4.5 W.m(-2)) did not differ between the groups. At fatigue, T(re) (G = 38.2 +/- 0.1, W = 38.4 +/- 0.1 degrees C), heart rate (G = 167.3 +/- 7.3, W = 171 +/- 3.3 beats.min(-1)), stroke index (G = 48.3 +/- 1.5, W = 52.4 +/- 1.8 ml.m(-2)), and forearm skin blood flow (G = 9.5 +/- 1.3, W = 11.7 +/- 1.5 ml.100 ml(- 1).min(-1)) did not differ between the groups. Similar to women, the main reasons reported by girls to stop exercising in the heat were localized leg fatigue and gluteus muscle discomfort. We conclude that heat-acclimatized girls exhibit an adequate cardiovascular and thermoregulatory adjustment while exercising in a hot and humid outdoor environment when hypohydration is prevented.     

Exercise rhabdomyolysis in military aircrew: two cases and a review of aeromedical disposition

INTRODUCTION: Exercise rhabdomyolysis (ER) is a rare, sometimes catastrophic condition where muscle fibers breakdown in response to exertion and release their breakdown products into the circulation. While ER was brought to the medical community's attention largely through reports from military training establishments we are unaware of ER having resulted from the activities of military aircrew. This paper reports two cases of ER in military aircrew and discusses the condition and the approaches taken in determining their future aeromedical disposition. CASE REPORTS: Rhabdomyolysis occurred in two military pilots as a result of their aircrew duties. One, an experienced pilot, suffered rhabdomyolysis as a result of centrifuge based G-training, while the other, a cadet in training, suffered rhabdomyolysis precipitated by exertion during moderately warm weather. Further investigation revealed the second case to also have the Malignant Hyperthermia Trait. AEROMEDICAL DISPOSTION: After wide consultation and lengthy deliberations both of these aircrew were returned to their full previous flying status. No further complications or recurrences have occurred.     

Responses of distance runners and sprinters to exercise in a hot environment

The responses of highly trained distance runners and track sprinters and age-matched untrained men were compared during bicycle ergometry in a 40 degree temperature-controlled environmental chamber. There were no differences among groups in rectal temperature following the 90 min exercise bout. Distance runners had a lower heart rate than either sprinters or untrained subjects. There was no difference in heart rate between sprinters and untrained subjects. Distance runners and sprinters had a much greater sweat rate than untrained subjects and dissipated a greater proportion of their total heat load by evaporation of sweat. Sprinters, however, had a lower sweat rate than distance runners in the hot environment and could only maintain as low a skin temperature as distance runners for 75 min of the 90 min session. Both aerobic training and anaerobic training confer some degree of protection from heat injury during exercise in a hot environment. However, sprinters have a higher heart rate and cannot sustain a low skin temperature as long as distance runners. Sprinters lost their advantage over untrained subjects in skin temperature after 75 min of exercise in a hot environment and did not have a lower heart rate than untrained subjects. Distance runners had a significantly lower heart rate and maintained a lower skin temperature than untrained subjects for the entire 90 min exercise bout.     

Ultrasound-guided injection for MR arthrography of the hip: comparison of two different techniques

Objective

The purpose of this study was to prospectively evaluate the two different ultrasound-guided injection techniques for MR arthrography of the hip.

Materials and methods

Fifty-nine consecutive patients (21 men, 38 women) referred for MR arthrographies of the hip were prospectively included in the study. Three patients underwent bilateral MR arthrography. The two injection techniques were quantitatively and qualitatively compared. Quantitative analysis was performed by the comparison of injected contrast material volume into the hip joint. Qualitative analysis was performed with regard to extraarticular leakage of contrast material into the soft tissues. Extraarticular leakage of contrast material was graded as none, minimal, moderate, or severe according to the MR images. Each patient rated discomfort after the procedure using a visual analogue scale (VAS).

Results

The injected contrast material volume was less in femoral head puncture technique (mean 8.9?±?3.4?ml) when compared to femoral neck puncture technique (mean 11.2?±?2.9?ml) (p?<?0.05). The chi-squared test showed significantly more contrast leakage by femoral head puncture technique (p?<?0.05). Statistical analysis showed no difference between the head and neck puncture groups in terms of feeling of pain (p?=?0.744) or in the body mass index (p?=?0.658) of the patients.

Conclusion

The femoral neck injection technique provides high intraarticular contrast volume and produces less extraarticular contrast leakage than the femoral head injection technique when US guidance is used for MR arthrography of the hip.     

高能量Pilon骨折分期治疗两种不同固定方法疗效的比较

 目的 比较高能量Pilon骨折分期治疗中锁定加压钢板内固定与有限内固定结合外固定的疗效。方法 回顾性分析2009-01至2013-10治疗的56例高能量Pilon骨折患者的临床资料。早期采用跟骨牵引或支具、石膏外固定后,二期按手术固定方法不同分为两组:A组27例行切开复位锁定加压钢板内固定,B组29例行微创有限内固定结合外固定。比较术后两组患者骨折愈合的时间、踝关节功能恢复、并发症情况。结果 A组骨折愈合时间(4.9±0.6)个月,B组(5.2±0.7)个月,两组比较差异无统计学意义。A组踝关节功能恢复优良率(81.5%)与B组(75.9%)比较,差异无统计学意义。A组共发生并发症5例(18.5%),B组7例(24.1%),两组比较差异无统计学意义;但感染发生率比较,A组(14.8%)高于B组(0)(P＜0.05)。结论 在高能量Pilon骨折分期治疗中,上述两种治疗方法均能取得满意效果且疗效相当,但对伴有重度软组织伤者,微创有限内固定结合外固定较切开复位锁定加压钢板内固定治疗,感染的风险更低。