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Cooling Techniques and Devices for Targeted Temperature Management in Post-Cardiac Arrest Patients

By Currents Editor posted 04-23-2020 10:48

  
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Cardiac Arrest and Cooling

Out-of-hospital cardiac arrest (OHCA) has an incidence of about 110.8 per 100,000 in all ages, while in-hospital cardiac arrest (IHCA) has an estimated incidence of about 292,000 cases per year in the United States.

 

In view of the recent HYPERION trial, finding for the effectiveness of targeted temperature management (TTM) in non-shockable rhythm arrest, TTM is again at the forefront of discussion and remains the standard of care for acute management of all unresponsive post-cardiac arrest patients. Several modalities are currently available for the delivery of TTM. The below varying techniques of cooling provide different advantages and disadvantages depending on the phase of targeted temperature management, be it during the induction, maintenance or rewarming phases.
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Chilled Saline Infusion

The induction phase refers to cooling the patient to a range of 32-36° Celsius.  Non-commercial surface cooling methods, such as ice packs or ice packed cooling blankets or mats applied to the neck, groin and axillae, as well infused cold fluids, are viable options during this phase. Cold saline or Ringer’s lactate solution (4°C) has been shown to decrease temperature by 2°C to 4°C with minimal complications, such as pulmonary edema or decreased cardiac output at 30ml/kg.  Though said methods are cost effective and are relatively easy to implement in the ICU, these methods remain ineffective for the maintenance phase and require intensive nursing interventions, placing a large burden on ICU nurses.  Despite these drawbacks, infused cooled fluids remain useful as induction or adjuncts.

 

Surface Cooling

Several commercial surface cooling systems are currently available, comprising pads or blankets that cover at least 40% of the patient’s body surface. These tools absorb corporal heat by circulating cold fluid or air, utilizing a closed-loop mechanism that continually measures and makes micro adjustments toward the goal temperature, essentially acting as thermostat. Surface cooling devices are able to perform all three phases of TTM efficaciously. However, surface cooling presents several disadvantages, including cost, shivering, potential skin injuries or burns, and inadequate pad sizes for morbidly obese patients. Shivering is a common complication of surface cooling, leading hospitals to adopt shivering mitigation protocols. Additionally, this technique is more likely to result in overcooling and has greater temperature variability than intravascular cooling devices. Overall, commercial surface cooling method remains the most popular modality of TTM.

Chilled Saline Infusion

The induction phase refers to cooling the patient to a range of 32-36° Celsius.  Non-commercial surface cooling methods, such as ice packs or ice packed cooling blankets or mats applied to the neck, groin and axillae, as well infused cold fluids, are viable options during this phase. Cold saline or Ringer’s lactate solution (4°C) has been shown to decrease temperature by 2°C to 4°C with minimal complications, such as pulmonary edema or decreased cardiac output at 30ml/kg.  Though said methods are cost effective and are relatively easy to implement in the ICU, these methods remain ineffective for the maintenance phase and require intensive nursing interventions, placing a large burden on ICU nurses.  Despite these drawbacks, infused cooled fluids remain useful as induction or adjuncts.

 

Surface Cooling

Several commercial surface cooling systems are currently available, comprising pads or blankets that cover at least 40% of the patient’s body surface. These tools absorb corporal heat by circulating cold fluid or air, utilizing a closed-loop mechanism that continually measures and makes micro adjustments toward the goal temperature, essentially acting as thermostat. Surface cooling devices are able to perform all three phases of TTM efficaciously. However, surface cooling presents several disadvantages, including cost, shivering, potential skin injuries or burns, and inadequate pad sizes for morbidly obese patients. Shivering is a common complication of surface cooling, leading hospitals to adopt shivering mitigation protocols. Additionally, this technique is more likely to result in overcooling and has greater temperature variability than intravascular cooling devices. Overall, commercial surface cooling method remains the most popular modality of TTM.

 
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Fig 1. Artic Sun gel coated water-circulating pads. Adapted from Artic Sun®.

Intravascular Cooling Devices

Intravascular cooling devices are another modality, which offers increased effectiveness and thermal stability. These devices have balloons through which cool saline or a dedicated coolant is circulated, removing heat directly from the venous circulation. Being a closed-loop system, no fluids or coolant to enter the circulation, which offers the advantage of continual and more fine-tuned temperature regulation while offering less temperature variability. Intravascular cooling is proven more effective at maintaining temperature within 0.2° C of the set goal. Intravascular cooling does necessitate placement of a large bore central venous catheter, however, most of these devices possess additional inlet ports providing access for drug administration. Disadvantages associated with this method include catheter associated infection, catheter placement injury and venous thrombosis. However, most of these patients may already require central venous access for management of post-cardiac arrest complications, such as hemodynamic instability. Other devices that are not indicated for cooling but also lower temperature include extracorporeal membrane oxygenation circuits and continuous veno-venous hemofiltration.

 

A relatively novel technique, Transnasal Evaporative Cooling (TEC) was studied in a randomized multicenter trial including witnessed cardiac arrest patients receiving early CPR. Although sage and feasibility, no statistically significant change in clinical outcome was observed, and TEC has not gained much traction in the field.

 

At this time, no head-to-head randomized control studies have found outcome differences between intravascular and surface cooling in terms of outcomes, with the former holding an edge in terms of management precision. Cold intravenous fluid administration continues to be considered safe and effective during at least the induction phase. Many avenues are available to reach the same goal of 32-36° Celsius.

  

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Fig 2. Example of intravascular cooling device (Alsius CoolGard 3000®; Adapted from Zoll).

 

References

  1. Benjamin EJ, Muntner P, Alonso A, Bittencourt MS, Callaway CW, Carson AP, Chamberlain AM, Chang AR, Cheng S, Das SR, et al.; American Heart Association Council on Epidemiology and Prevention Statistics Committee and Stroke Statistics Subcommittee. Heart disease and stroke statistics-2019 update: a report from the American Heart Association.Circulation. 2019; 139:e56–e528.
  2. Callaway CW, Donnino MW, Fink EL, Geocadin RG, Golan E, Kern KB, et al. Part 8: post-cardiac arrest care: 2015 American Heart Association Guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2015;132(18 Suppl 2):S465–82.
  3. Polderman KH: Keeping a cool head: how to induce and maintain hypothermia. Crit Care Med 2004, 32: 2558-2560.
  4. Kliegel A, Janata A, Wandaller C, et al: Cold infusions alone are effective for induction of therapeutic hypothermia but do not keep patients cool after cardiac arrest. Resuscitation 2007; 73:46–53
  5. Polderman KH, Herold I. Therapeutic hypothermia and controlled normothermia in the intensive care unit: Practical considerations, side effects, and cooling methods*. Crit Care Med 2009; 37(3): 1101-20
  6. The Hypothermia After Cardiac Arrest Study Group: Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002; 346:549
  7. Flint AC, Hemphill JC, Bonovich DC: Therapeutic hypothermia after cardiac arrest: Performance characteristics and safety of surface cooling with or without endovascular cooling. Neurocrit Care 2007; 7:109–118
  8. Castrén M, Nordberg P, Svensson L, Taccone F, Vincent JL, Desruelles D, et al. Intra-arrest transnasal evaporative cooling: A randomized, prehospital, multicenter study (PRINCE: Pre-ROSC intraNasal cooling effectiveness). Circulation 2010;122:729-36.
  9. Seder DB, Van der Kloot TE. Methods of cooling: Practical aspects of therapeutic temperature management. Crit Care Med. 2009; 37: S211-22.

 


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