Hypothermia Induction Methods

Transcription

1 Hypothermia Induction Methods Advantages and Disadvantages Xia Luo, M.D. Vice President, Clinical Education ZOLL Corporation

2 Targeted Temperature Management (TTM) Temperature is one of the four vital signs (BP, RR & Pulse) Include fever control, therapeutic hypothermia and warming Shown to improve outcomes, reduce complications during recovery after a period of stopped blood flow to the brain. Goal of TTM is Neuroprotection and to improve neurological outcomes in patients with acute brain injury (global or local)

3 Inducing hypothermia Mild = C Metabolic & vascular (maintain Normothermia) Pharmacologic Mechanical

4 Metabolic & Vascular - Thermoregulation in humans is effected through: metabolic activity sweating or shivering vascular activities Dilation or constriction

5 NEGATIVE FEEDBACK Blood temperature Core body temperature <37 C Thermoreceptors Thermoreceptors Hypothalamus Nerves Muscles of skin arteriole walls constrict Sweat glands decrease secretion Body loses less heat Return to 37 C Nerves Muscles shivering Body gains heat Feedback control system summarized

6 Vasodilation

7 Vasoconstriction

8 Inducing Hypothermia - Pharmacologic Preventing Hyperthermia antipyretics acetaminophen, ibuprofen, aspirin, NSAIDs propofol mild poikilothermic, controls shivering barbiturates induce coma & decrease CMR general anesthetic impairs thermoregulatory response meperidine control shivering - preventing hyperthermia narcotics pain & shivering - preventing hyperthermia Busperon synergistic w/ meperidine to prevent shivering

9 Inducing Hypothermia - Mechanical Convection (cold shower or fan/air condition) Heat exchanged with the environment by the movement of air or water molecules adjacent to the skin. Conduction (ice blanket, cooling catheter) Heat exchange between the skin/blood and the adjacent surface material Evaporation (alcohol bath) Heat loss as energy used to transform a liquid into a gas. What is the fastest way?

10 There are a lot of ways to cool

11 Non-Medical Methods

12 Evolution of cooling methods in medicine

13 How to Cool Internal (Core) Cooling Intravascular Temperature management (IVTM) IV cold saline Iced Lavage Extracorporeal circulating cooled blood & Cardiopulmonary bypass External (Surface) Cooling Ice bags/packs Cooling blankets traditional, wraps, Gal pads Ice baths

14 TTM Methods Core Cooling Heat exchange occurs directly with blood from the core typically intravenous via a catheter, cannula, etc. Thermoregulation based on feedback from patient temperature probe Surface Cooling 90% of heat exchange occurs through skin Heat transfer is directly proportional between the cooling pad/blanket to the skin surface area Some systems have feedback control

15 Ideal Cooling Device for Therapeutic Hypothermia Rapidly cools the body core to target temperature Precise control of patient temperature Slow controlled rewarm Precise control to maintain normothermia after TH treatment 37 C Crash Cool Phase Maximum Cooling Rate Rewarm Phase Maintain Normothermia 33 C Maintenance Phase Tight control for 24 hours Slow, controlled rewarm to avoid ICP rebound 4 Phases of Temperature Management

16 Core Cooling with Cold IV Fluid -4ºC Advantages Good way to get jump started 30 cc/kg of 4 C = 1.2 C decrease in 25 minutes 40 cc/kg of 4 C = 2.0 C decrease in 30 minutes Disadvantages Difficult to reach and maintain target temperature Require another cooling method to maintain Limitation on the fluid quantities due to heart condition Kliegel A, et al: cold infusion alone are effective for induction of therapeutic hypothermia but do not keep patients cool after cardiac arrest. Resuscitation 2007.

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18 Rectal / Gastric Lavage Advantage Can drop temperature Disadvantage Very labor intensive Can not maintain Very invasive

19 Iced bath / cold water immersion Advantage Faster cooling Disadvantage Not practical Only for induction, no maintenance, no control Patients can not have open wound

20 Local cooling with head cap Advantage May work on Neonate for fever control Disadvantage Not for hypothermia induction Does not work in adult Only cool the scalp, not the brain Hachimi, Resus, 2001 and Gaida BJ, et al, EuroNeuro 2008

21 Extracorporeal circulating cooled blood & cardiopulmonary bypass Advantage Fast Maybe used in cardiogenic shock Open heart surgery as the mechanical circulatory support Disadvantage Very invasive Require specialty to manage the machine and insert canular

22 Variety of surface blankets Water-circulating Cold air Hydrogel-coated water pads

23 Surface cooling Advantage May be initiated by nursing staff without physician presence Non-invasive Faster time to initiate cooling Some may be reusable Lower costs (some) Disadvantage Not efficient and reliable Temperature fluctuation and overshoot Shivering Labor intensive Risk of skin burns and lesions Higher costs (Gal pads), nonreusable Limits patient access because cooling rate based on skin coverage Some do not have temperature feedback loop

24 Limitations of External Cooling Methods Difficult to achieve target temperature 14% never achieve target, Holzer, Stroke, 2006 Difficult To Maintain Target Temperature 15% maintain temperature between C during the treatment period, Kliegel, NeuroCrit Care, 2007 Easy To Overshoot Target 63%, Merchant, CCM, 2006 Uncontrolled Rewarming Rebound Hyperthermia

25 Intravascular Temperature Management IVTM system is a catheter based solution which effectively cools and warms the patient from the inside out. It has the added benefit of a standard Central Venous Catheter, which these critically ill patients all require for ongoing care. Vein Placement options: Femoral Subclavian Internal jugular

26 How the Catheters Work Cool or warm saline flows within the balloons Blood is cooled or warmed as it passes by each balloon Closed-loop system no fluid infusion to the patient

27 Advantage of IVTM Clinical evidence shows better outcomes; 35% better long-term neurological outcomes than surface cooling. 1 Reaches and maintains target temperature 100% of the time. 2-8 Does not over or undershoot the target temperature; maintains target temperature within ±0.2 C. 4 offers precise cooling and faster to target. Results in a lower rate of shivering (4%) 3, which may require less sedation, paralytics and can be used in awake, non-intubated patients 9. Can use skin counter warming Unhindered patient access allows for full-body counter-warming. Can be used with patients who are not candidates for surface (i.e. burn, trauma, fragile skin). Reduces nursing workload by 74% 1 ; no constant monitoring of temperature, managing shivering, checking pads, etc. Includes a triple lumen; adding vital capability to a line that is already being placed. 1 ICEREA Deye N, et al. Circulation. 2015;132: Mayer SA, et al. Critical Care Medicine. 2004;(3)212: Diringer MN, et al. Critical Care Medicine. 2004;(32)2: Hoedemaekers CW, et al. Critical Care. 2007;11:R91. 5 Heard KJ, et al. Resuscitation. 2010;81: Horn CM, et al. Journal of Neurointerventional Surgery Mar;6(2): Knapik P, et al. Kardiologia Polska. 2011;69(11): COOL-ARREST JP: An Evaluation of Therapeutic Hypothermia by Means of Intravascular Cooling (Intravascular Temperature Management; IVTM) in Patients who Have Undergone Endogenous Cardiac Arrest and Return of Circulation a Joint, Multicenter, Single-Arm, Prospective Interventional Study Trial. 9 Erlinge D et al: Circulation. 2010

28 Disadvantage Require intervention procedure Potential risks similar to CVC (i.e. DVT, infection, bleeding) Higher costs than some cooling blanket

29 FACTORS THAT AFFECT COOLING Shivering Patient body mass Method of cooling

30 Shivering Body tries to self regulate to keep normal body temperature (~37 C) Vasoconstriction to keep body warm Vasodilation to keep body cool Shivering Zone between C General anesthesia and neuromuscular blocking agents typically used to control shivering Uncomfortable to patient, can increase ICP and myocardial demand leading to potential catastrophic issues Guidelines strongly recommends the avoidance of shivering during hypothermia induction

31 What you should know about shivering and surface cooling vs core cooling When skin feels cold, the blood vessels constrict Body s attempt to thermoregulate and conserve body heat Surface cooling devices increase peripheral vasoconstriction and shivering since it is applied directly to the skin Studies show more shivering with surface cooling One study showed 86% of surface cooled (Gel pads) patients experienced shivering Another study showed 96% of post-cardiac arrest intubated paralyzed patients Patients experience less shivering with core cooling Does not pass skin, counter warming help to eliminate vasoconstriction Need less sedation and paralytics since less shivering

32 Patient Body Mass Obese (BMI 25) patients are more difficult to cool Have reduced ability to dissipate internal heat because of low thermal conductivity of their layers of fat High body weight found to be a risk factor for failure of surface cooling Can affect speed of cooling since there is more body fat layers to pass through Greater area/mass needs to be cooled Core cooling more effective for obese patients Directly cools from within Does not pass through body fat layers

33 Cooling Performance Affected by Cooling Method Performance factors to consider: Time to start of cooling Time to target temperature Ability to achieve and maintain target temperature Minimal temperature overshoot and fluctuations Minimal shivering

34 Intravascular Case Study Rapid cooling in a high BMI patient (181 kg) Target Temperature = 33 C Weight: 181 kg Gender: Male Patient Profile ZOLL System Thermogard XP with Quattro Catheter Starting Patient Temp: 35 C Target Temp: 33 C Summary Actual graph downloaded from ZOLL Thermogard System Target temperature of 33 C was reached in 2.1 hours.

35 Surface Case Study Target Temperature = 33 C Slow response time allows Patient Temperature to fluctuate by as much as 2 C. Time to Target Temperature approx. 6 hr. Actual data download from another vendor s surface system

36 Future Applications Recanalization or Revascularization Acute Ischemic Stroke Acute Myocardial Infarction Temperature is Mind Time is Muscle Prevention of reperfusion injury

37 The Common Characteristics Non-paralyzed and intubated Neuroprotection (target 33ºC) needs to be on board before clot removal No delays on intervention Require a powerful cooling device Hypothermia induction via the core

38 Take a way message Hypothermia is the best neuroprotective strategy that has been shown to work in decades It affects all of the mechanisms underlying ischemia Selection of device should be faster reaching target temperature, precisely maintain, controlled rewarming Less complications (i.e. shivering)

39 33 C or 36 C? OHCA pvt/vf who are comatose, TTM at C for 24hrs is highly likely to be effective in improving neurologic outcomes (Level A) OHCA with pvt/vf, PEA or asystole who are comatose, TTM at 36 C for 24hrs is likely as effective, and is an acceptable alternative to TTM at C (Level B) Initial rhythm PEA/asystole who are comatose, TTM possibly is effective (Level C)

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