Study: Fast, inexpensive hypothermia protocol improves post-cardiac arrest

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A protocol using a combination of core and surface cooling modalities was rapid, safe and low cost in achieving mild therapeutic hypothermia, and relied on readily available equipment rather than costly commercial devices, according to a study in the January issue of Resuscitation.

The benefits of inducing mild therapeutic hypothermia in cardiac arrest patients are well established. Consequently, the International Liaison Committee on Resuscitation and the American Heart Association recommend that comatose survivors of ventricular fibrillation or ventricular tachycardia after out-of-hospital cardiac arrest (OHCA) undergo therapeutic hypothermia.

However, many centers have been slow to implement cooling protocols, citing the perception that they are technically difficult and slow to administer, and that they would need an expensive commercial device, according to the study.

In that regard, Pierre Kory, MD, from Beth Israel Medical Center in New York City, and colleagues tested a hospital-based cooling technique that used a combination modality of rapid, cold saline infusion, evaporative surface cooling and ice water gastric lavage.

They applied the technique to 65 in-hospital cardiac arrest and OHCA patients admitted to the 16-bed intensive care unit who met inclusion criteria during a three-year period.

The primary emphasis was on speed. The main endpoints were the time intervals between return of spontaneous circulation (ROSC), initiation of hypothermia and achievement of target temperature. All patients reached the target temperature.

The median time interval between ROSC and achievement of target temperature was 134 minutes, which decreased from a mean of 243 minutes over the first six months and to a mean of 177 minutes over the final 30 months.

The median time interval between ROSC and initiation of hypothermia was 68 minutes. The median time interval between initiation of hypothermia and achievement of target temperature was 60 minutes. The initiation of hypothermia to achievement of target temperature cooling rate was 2.6° C per hour.

The time from ROSC to target temperature is made up of two critical intervals, according to the researchers. The initiation of hypothermia to target temperature interval depends upon the technique used to induce hypothermia, whereas the ROSC to initiation of hypothermia interval is contingent upon logistical considerations, such as notification, transport, team organization, availability of equipment and preparation of equipment.

"Over time, we worked to reduce ROSC to initiation of hypothermia time by initiating cooling saline infusion at the initial patient location without waiting for transfer to an ICU, raising clinician awareness through multi-departmental lectures, allowing earlier notification by assigning a dedicated pager, using a combined teams approach, creating unique preparation task lists for the physicians and nurses executing the cooling protocol, and widely distributing the printed protocol," researchers wrote. "With these methods, we observed a reduction in the median ROSC to initiation of hypothermia time of 257 to 132 minutes."

Hypothermia Preparation—Team Task Lists
Emergency room/medical ward team

  • Place two large bore peripheral IVs
  • Retrieve four liters pre-cooled saline from refrigerator with two pressure bags
  • Infuse 40 ml/kg at 300 mmHg pressure

ICU physician team
  • Retrieve therapeutic hypnotherapeutic fan and bring to bedside.
  • Fill two patient basins with room-temperature water for evaporative cooling.
  • Fill one patient basin with ice slurry for gastric lavage.
  • Ice orogastric tube and insert.

ICU nurse team
  • Prepare temperature monitor with rectal probe for immediate insertion.
  • Prepare atracurium bolus dose of 25 mg.
  • Prepare fentanyl and midazolam infusions.

Researchers noted that all cooling modalities were stopped immediately upon the patient's rectal temperature reaching 34° C. Core temperature was maintained solely through the use of intermittent fanning without wetting the patient.

After 24 hours of hypothermia, fanning was discontinued and passive re-warming was initiated by placing a single blanket over the patient. Complete temperature data for the induction, maintenance and rewarming phases was available for 35 patients.

Three patients rewarmed to a temperature above 35° C and required additional evaporative cooling to reduce temperature within target range. Moderate overshoot (30–31° C) occurred in five patients and severe overshoot (nadir less than 30° C) occurred in five patients. However, these did not result in any adverse effects such as arrhythmias requiring intervention, worsening hypotension, bleeding or severe electrolyte abnormalities.

Researchers reported that the rates of complications during induction and maintenance on hypothermia were similar to those reported in the literature for OHCA patients, "despite the fact that our population included 62 percent of in-hospital cardiac arrest patients with significant comorbidities."

In all, 31 percent of this mixed population of in-hospital cardiac arrest and OHCA patients recovered to a Pittsburgh cerebral performance score of 1 or 2.