New Considerations for Diagnosing, Treating, and Preventing Exertional Heatstroke

Transcription

1 New Considerations for Diagnosing, Treating, and Preventing Exertional Heatstroke Kevin C. Miller, PhD, AT, ATC Central Michigan University NDATA Symposium, April 2013

2 Thank you

3 Funding Disclosure and Conflict of Interest 0 private companies have funded any of the studies discussed today The views in this presentation are my own and may not be the views of CMU or my colleagues. I hope to present unbiased information

4 Exertional Heat Stroke (EHS) Deaths *Data from the Korey Stringer Institute, University of Connecticut Korey Stringer: 42.2 C (108 F) T 90 minutes after collapse

5 Recognizing EHS Two critical variables for identifying EHS: 1. Severe Hyperthermia (elevated core temp) >40 C (104 F) 2. Obvious CNS impairment (e.g., altered consciousness, irritability)

6 Body Core Temperature Measurement Sites Oral Tympanic Axillary Esophageal Intestinal (transmitter) Rectal

7 Which Devices do ATs Perceive as Most Valid? Mazerolle S, Scruggs I, Casa D, et al. Current knowledge, attitudes, and practices of certified Athletic Trainers regarding recognition and treatment of exertional heat stroke. J Athl Train. 2010;2: Rectal & Ingestible perceived as most valid = Great! But

8 Casa D, Becker S, Ganio M, et al. Validity of devices that assess body temperature during outdoor exercise in the heat. J Athl Train. 2007;42: Rectal v. Ingestible Thermometers Verdict = Good! * = Significantly Different than Rectal Exercise Cool Down

9 Casa D, Becker S, Ganio M, et al. Validity of devices that assess body temperature during outdoor exercise in the heat. J Athl Train. 2007;42: Rectal v. Expensive and Inexpensive Oral Thermometers That s a F Difference! F 99 F 97.5 F * = Significantly Different than Rectal Verdict = Bad! Exercise Cool Down

10 Casa D, Becker S, Ganio M, et al. Validity of devices that assess body temperature during outdoor exercise in the heat. J Athl Train. 2007;42: Rectal v. Aural (Ear) Thermometer * = Significantly Different than Rectal F 99.5 F Verdict = Bad Exercise Cool Down

11 Casa D, Becker S, Ganio M, et al. Validity of devices that assess body temperature during outdoor exercise in the heat. J Athl Train. 2007;42: Rectal v. Axillary (Armpit) Thermometers 6 Difference! Verdict = Terrible * = Significantly Different than Rectal Exercise Cool Down

12 New Considerations for EHS Diagnosis

13 NATA Position Statement: Exertional Heat Illness (c. 2015) Recommendation #22 But How far should you insert the thermometer? Does it matter?

14 What do We Teach our Students? 3-4 (still no 1 (no reference given) references) c c. 2014

15 So We Did a Study Step 1: Insert custom rectal probe (measure T rec at 4, 10, 15 cm) & esophageal probe Step 2: Stand on treadmill for 10 min to acclimate to heat (40 C, 27% rh). Walk/run until esophageal temp reached 39.5 C. Step 3 & 4: CWI until all 4 sites had temps <38 C. Then, recover in heat for 30 min.

16 Results of Rectal Depth Study Miller KC, Hughes L, Long BC, Casa DJ, Adams WM. Body core temperatures of the esophagus and rectum during exercise and cold-water immersion. Manuscript in review J Athl Train. a = T 4cm different than T eso. b = T 10cm different than T eso. c = T 15cm different than T eso. T 4cm = Different at 47 times (75% of all testing times)! T 10cm = Different at 41 times (67% of all testing times)! T 15cm = Different at 32 times (52% of all testing times)!

17 Average Bias by Rectal Depth a = Significantly higher than T 15cm (P<0.05). 0.2 C (0.36 F) difference between 4 cm and 15 cm

18 Average Bias by Experimental Period a = Rest, Exercise, and Post-immersion recovery < Cooling. b = Exercise < Postimmersion Recovery (P<0.05).

19 So What? Rectal depth matters when measuring body core temperature. Inserting a rectal probe 6 provides the most accurate measure of body core temperature Need to use a flexible probe and not a glass thermometer to reach that depth.

20 Treatment of EHS The 2 MOST important factors influencing the prognosis of EHS are: 1. Degree of Hyperthermia 2. Length of Time the Individual is Hyperthermic Most important

21 RAPID DIAGNOSIS (rectal temp) & RAPID COOLING! Treatment of EHS Monitor vitals. Cool the athlete THEN ship to the ER! When rapid cooling and rehydration performed, survival rates are >90%!!!

22 EHS Treatment Ideal Cooling Rates Acceptable Cooling Rates

23 Can t I just assume EHS, avoid doing T rec, & start cooling? Reasons you MUST DO T rec : 1. Confirms EHS diagnosis since S/S mimic other conditions 2. Tells you when to remove patient from CWI thereby preventing hypothermia 3. Allows you to develop RTP criteria

24 If you re thinking Naw, I ll just put them in the tub and not do T rec Water immersion within 5 min of symptoms (Awesome!) EMS called No T rec taken (Great so far!) (crap ) EMS take Gavin out of the tub after 5 min 30 min later at hospital. T rec = 108 F (42.2 C) (this is not going to end well ) (uh oh ) OUTCOME: Emergency liver transplant and almost dies August 2013 = EHS August 2015 = suing to play football

25 New Considerations for EHS Treatment: Necessity of Equipment Removal

26 American Football Players and EHS 1. Practice starts in early August 2. Equipment-intensive sport 3. Intensity of sport

27 NATA Position Statement: Exertional Heat Illness (c. 2002) Recommendation #22 (bullet #3): Lower the body-core temperature as quickly as possible. 34,70,77 The fastest way to decrease body temperature is to remove clothes and equipment and immerse the body (trunk and extremities) into a pool or tub of cold water (approximately 1 C to 15 C [35 F to 59 F]). 32,91,92,97-99 Aggressive cooling is the most critical factor in the treatment of exertional heat stroke. Circulation of the tub water may enhance cooling. None of these 6 references examined the effect of equipment on rectal cooling

28 So We Did a Study Miller KC, Swartz EE, Long BC. Cold-water immersion for hyperthermic humans wearing football uniforms. J Athl Train. 2015;50: Compare the time required to reduce T rec of hyperthermic individuals cooled via CWI while wearing a full American football uniform or control uniform 2. Determine how the uniform conditions affect T rec recovery

29 Methods

30 Results Table 1. Subject demographics and descriptive information (Means ± SD, n = 18). FULL CONTROL Age (y) 22 ± 3 Ht (cm) ± 6.8 Body Mass Index 25.7 ± 3.5 Sum of Skinfolds (mm) 46.6 ± 12.3 Body Density 1.07 ± 0.01 Body Fat (%) 13 ± 4 Body Surface Area (m 2 ) 2.0 ± 0.2 Pre-exercise Usg ± ± Body Mass 1 (kg) 82.3 ± ± 12.9 Body Mass 2 (kg) 81.2 ± ± 12.7 Sweat Rate (L h -1 ) 1.6 ± ± 0.4 Exercise Time to 39.5 C (min) 41.7 ± ± 10.9 Pre-immersion Water Bath Temperature ( C) a 9.82 ± ± 0.15 Post-immersion Water Bath Temperature ( C) a,b,c ± ± 0.30 Environmental Chamber Temperature ( C) d 39.9 ± ± 0.6 Environmental Chamber Relative Humidity (%) d 34 ± 3 35 ± 3

31 Results

32 Results 0.28 ± 0.12 C/min 0.23 ± 0.11 C/min Cool faster with a uniform on? That s weird a = Full < Control (t 17 = -2.1, P = 0.03, effect size = 0.48).

33 So We Did a Study Miller KC, Long BC, Edwards JE. Necessity of removing American football uniforms from hyperthermic humans before cold-water immersion. J Athl Train. 2015;50: Compare CWI durations and T rec cooling rates when hyperthermic subjects wear a full football uniform during CWI (PADS) or remove the uniform immediately before CWI (NO pads ). 2. Compare perceptual indicators of comfort (e.g., thermal sensation and environmental symptoms) before and after CWI in both conditions.

34 1. 18 euhydrated males completed 2 testing days. Weighed nude. Inserted a rectal thermistor. 3. Subjects rated thermal sensation and ESQ pre & post-exercise 4. Day 1 = PADS off prior to CWI (10 C). Day 2 = PADS on during CWI Methods 2. Donned full football uniform and ran in the heat (40 C, 40% rh) until T rec = 39.5 C 5. Time to reduce T rec to 38 C and cooling rates were recorded.

35 Results Table 1. Subject demographics and descriptive information (Means ± SD, n = 18). NOpads PADS No significant differences between days for: (1) Water temperature, (2) Exercise duration, (3) Heat chamber temperature or rh (4) Hypohydration level Age (y) 22 ± 2 Ht (cm) ± 6.1 Body Mass Index 25.7 ± 4.1 Sum of Skinfolds (mm) 38.8 ± 16.4 Body Density 1.07 ± 0.01 Body Fat (%) 11 ± 5 Body Surface Area (m 2 ) 2.07 ± 0.16 Body Mass 1 (kg) 85.4± ± 12.9 Body Mass 2 (kg) 84.1 ± ± 12.8 Pre-exercise Usg ± a ± Sweat Rate (L h -1 ) 1.9 ± ± 0.5 Hypohydration (%) 1.5 ± ± 0.4 Exercise Time to 39.5 C (min) 40.8 ± ± 4.1 Pre-immersion Water Bath Temperature ( C) 9.97 ± ± 0.06 Post-immersion Water Bath Temperature ( C) b ± ± 0.30 Environmental Chamber Temperature ( C) 40.1 ± ± 0.5 Environmental Chamber Relative Humidity (%) 40 ± 3 39 ± 3 NOpads = shorts, undergarments, and socks. PADS = shorts, undergarments, t-shirt, socks, practice jersey, shoulder pads, helmet, game pants, and padding over the thighs, knees, hips, and tailbone. Usg = urine specific gravity. a = NOpads < PADS (P< 0.05). b = Pre-immersion temperature < post-immersion temperature (main effect of time, P< 0.05).

36 Results: CWI Duration Cooled 1.3 min faster in NO pads a = No pads < PADS (z = 2.3, P = 0.01).

37 Results: Cooling Rates 0.28 ± 0.14 C min ± 0.11 C min -1 a = No pads > PADS (t 17 =2.2, P=0.02).

38 Results: Environmental Symptoms Questionnaire ESQ scores at each time point were summed to create an overall symptom score. 0 = No symptoms 5 = Extreme symptom a = Main effect of equipment where PADS < NO pads (P=0.03). b = Main effect of time where Pre-exercise < Post-CWI (P<0.001).

39 Unbearably Hot Results: Thermal Sensation Comfortable Unbearably Cold

40 So What? 1. PADS should be removed before CWI when: individuals knowledgeable in equipment removal are present, removal tools (e.g., scissors) are immediately available, PADS can be easily removed, PADS interfere with the ability to fully immerse the athlete. 2. If CWI has been delayed or the above are not met, immerse the football athlete with PADS on. 3. Cool first, transport second.

41 NATA Position Statement (c. 2015) Now Recommends Miller et al 2015.

42 New Considerations for EHS Treatment: Water Bath Temperature

43 NATA Position Statement (c. 2015) Recommends To get a large water bath that cold, you need a lot of ice. What if you don t have access to a lot of ice? Can temperate water reduce T rec effectively?

44 So We Did a Critically-Appraised Topic (CAT) PIO Question = Are T rec cooling rates acceptable ( 0.08 C/min) when severely hyperthermic humans are immersed in temperate water? High Quality Research studies in English ( ) Examining Temperate Water Immersion (>20 C or 68 F) to Treat Exerciseinduced Hyperthermia (Core Temp >39.5 C) n = 4 Studies Included in CAT n = 3 Studies excluded because of duplicate data reporting by the authors n = 1

45 Truxton T, Miller KC. Can temperate water immersion be used to treat exertional heat stroke?: A critically-appraised topic. J Sport Rehabil. In press.

46 CAT Methods and Interventions Truxton T, Miller KC. Can temperate water immersion be used to treat exertional heat stroke?: A critically-appraised topic. J Sport Rehabil. In press. Heated subjects to core temperature of 40 C Cooled subjects with C water (68-79 F)

47 CAT Results Truxton T, Miller KC. Can temperate water immersion be used to treat exertional heat stroke?: A critically-appraised topic. J Sport Rehabil. In press. 3 of 3 studies showed acceptable to ideal cooling rates with TWI 1 group of subjects had unacceptable cooling rate (more muscle mass & less BSA)

48 And Then We Did a Study Truxton T, Miller KC, Long BC. Can temperate water immersion effectively cool hyperthermic humans wearing American football uniforms? Manuscript being prepared for J Sports Sci. No Differences in Cooling with TWI (54 sec difference)

49 Truxton T, Miller KC, Long BC. Can temperate water immersion effectively cool hyperthermic humans wearing American football uniforms? Manuscript being prepared for J Sports Sci. Cooling rate = Cooling rate = 0.12 ± 0.05 C min ± 0.05 C min -1

50 Results: Thermal Sensation with Temperate Water Immersion Unbearably Hot Comfortable Unbearably Cold Subjects are more comfortable and have less shivering in TWI (TS score = 2.8) than CWI (TS score = 1.8)

51 So What? 1. It takes about 2x as long to cool people with TWI than CWI, but 2. T rec cooling rates are still considered acceptable with TWI EHS Victim with T rec 42 C: If PADS left on = 14 mins with CWI; 26 min with TWI 3. Water immersion is more powerful than all other cooling strategies!

52 New Considerations for EHS Treatment: Effectiveness of Cooling Vests

53 Mazerolle S, Scruggs I, Casa D, et al. Current knowledge, attitudes, and practices of certified Athletic Trainers regarding recognition and treatment of exertional heat stroke. J Athl Train. 2010;2: ATs perceived effectiveness of cooling methods for EHS #1 = Cold-water Immersion #2 = Ice vests/blankets?????

54 So We Did another CAT PIO Question = Are T Core cooling rates acceptable (i.e., >0.08 C min -1 ) when hyperthermic humans are treated with cooling vests post-exercise? Research studies in English ( ) Examining Cooling Vests to Treat Hyperthermia (Core Temp >38 C) n = 12 Studies Included in CAT n = 4 Studies excluded for not having PEDro score >5, Oxford EBP Category Level 2 or higher, or core temp did not exceed 38 C n = 8

55 Keen ML, Miller KC. Should cooling vests be used to treat exertional heatstroke?: A critically-appraised topic. J Sport Rehabil. 2015; In press. Table 1. Summary of study designs of articles retrieved Author Study Design Level of evidence PEDro Score Brade et al. 2 Randomized Controlled Trial 2 6 of 10 DeMartini et al. 4 Randomized Controlled Trial 2 5 of 10 Holster et al. 3 Randomized Controlled Trial 2 6 of 10 Lopez et al. 1 Randomized Controlled Trial 2 6 of 10

56 Keen ML, Miller KC. Should cooling vests be used to treat exertional heatstroke?: A critically-appraised topic. J Sport Rehabil. 2015; In press. Table 2. Characteristics of included studies Authors Patients, n Experimental Design & Cooling Results Conclusions Methods Intervention Brade et al males -Cross-over study. (1) dry PC17 vest with PC17 vest T C pre-cooling -No significant (age=21.3±1.1 y, -Cycled on a bicycle 4 anterior and posterior = 38.44±0.42 C differences between ht=182.7±7.1 cm, ergometer at 75% pockets; (2) a gel vest Gel vest T C pre-cooling = both cooling vests mass=76.2±9.5 kg, VO 2max in heat for (4 anterior and posterior 38.49±0.43 C and no vest. BSA=1.98±0.14 m 2 ) 30 min (35 C±1.4 C, pockets); or (3) no vest No vest T C pre-cooling = -Both cooling vests 52%±4% humidity). 38.5±0.4 C did not meet the -Wore one of two vests acceptable cooling or no vest for 30 min PC17 vest cooling rate = rate for EHS victims. in a comfortable room 0.038±0.007 C/min (i.e., >0.08 C/min) (24.9±1.8 C, 39±10%) Gel vest cooling rate = 0.040±0.009 C/min No vest cooling rate = 0.034±0.010 C/min DeMartini 9 males and -Cross-over study. (1) Game Ready Active T C pre-cooling -No significant et al. 4 7 females -Played soccer, vest with 14 C = 38.73±0.12 C differences between (age=24±6 y, ultimate frisbee and circulating water with (average all trials) both cooling vests ht=182±7 cm, bree-ball outside shade; (2) Nike Ice and no vest. mass=74.03±9.17 kg, (26.64±4.71 C) Vest TM with 22 pouches Game Ready Active vest -Both cooling vests BSA a = ~1.9 m 2 ) for min. with shade; or (3) no cooling rate = did not meet the - Wore one of two vest without shade ±0.025 C/min acceptable cooling vests or no vest for Nike Ice Vest TM cooling rate for EHS victims. 10 min with or rate = 0.053±0.022 C/min (i.e., >0.08 C/min) without shade. No vest cooling rate = 0.042±0.015 C/min

57 Keen ML, Miller KC. Should cooling vests be used to treat exertional heatstroke?: A critically-appraised topic. J Sport Rehabil. 2015; In press. Table 2. Characteristics of included studies, continued. Authors Patients, n Experimental Design & Cooling Results Conclusions Methods Intervention Holster et al males -Cross-over study. (1) water-perfused T C pre-cooling -No significant (age=31.1±7.6 y, -Exercised on a cooling vest; or (2) = 38.25±1.0 C differences between ht=176.2±5.5 cm, treadmill for 50 min no vest. (average both trials) cooling vest and no mass=80.2±12.2 kg, in the heat vest. BSA a = ~2.0 m 2 ) (35.1±2.7 C). Vest cooling rate -Cooling vest did not and 4 females -Wore vest or no vest = 0.041±0.022 C/min meet the acceptable (age=25.5±5.2 y, for 20 min in a No vest cooling rate cooling rate for EHS ht=157.7±2.9 cm, comfortable room = 0.047±0.031 C/min victims (i.e., mass=58.5±6.7 kg, (24.0 C±1.4 C) >0.08 C/min) BSA a = ~1.6 m 2 ) Lopez et al males -Cross-over study. (1) INDURA Heat T C pre-cooling = -No significant (age=25.6±1.6 y, -Ran on a treadmill for Shield Vest (vest temp = 38.8±0.3 C differences between mass=80.3±13.7 kg) b 67.0±10.6 min in the 21.1 C); or (2) no vest (average both trials) INDURA Heat Shield heat (33.3±3.1 C; Vest and no vest. humidity=55.1±8.9%) INDURA Heat Shield -Cooling vest did not -Wore vest or no vest Vest cooling rate = meet the acceptable for 30 min in a 0.03±0.007 C/min cooling rate for EHS comfortable room No vest cooling rate = victims (i.e., (26.6±2.2 C; 0.028± C/min >0.08 C/min) 55.4±5.8% humidity). Average Cooling rate for all vests in CAT = 0.04 C/min! ht = height, BSA = body surface area, T C = core body temperature, VO 2max = maximum volume of oxygen consumed (ml/kg/min), PC17 = phase-change material cooling vest, EHS = exertional heatstroke. a = We calculated BSA with the original author s descriptive information using the following equation: weight height b = Height was not provided in article so BSA could not be calculated.

58 What Does This Mean for EHS Victims? If T core was 42 C and cooling vests were used, it would take 100 minutes to reduce T core to a safe level (i.e., 38 C) Goal is to reduce T core within 30 minutes of collapse

59 McDermott B, Casa D, Ganio M, et al. Acute whole-body cooling for exercise-induced hyperthermia: A systematic review. J Athl Train. 2009;44: Unacceptable cooling rates for EHS victims. Cooling vests have similar cooling rates as: 1. Dousing with water while fanning (0.035 C/min) 1. Ice packs covering the body (0.034 C/min) 2. Ice packs at major arteries and dousing with fanning (0.036 C/min) 3. Fanning and compressed air (0.04 C/min)

60 The So What Messages from Today 1. When taking T rec, insert a flexible thermometer 6 to get the most valid reading. 2. You don t have to remove football gear before CWI or TWI to get acceptable to ideal cooling rates. 3. Invest in a Rubbermaid tub ($100-$300). Water immersion (temperate or cold) is the fastest way to lower T rec 4. Don t use cooling vests to treat EHS.

61 Your Questions or Comments?