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New data supports cooling cardiac arrest patients

Cooling the pharynx could be a good approach to cooling the brain, according to researchers at Okayama University who set out to determine whether pharyngeal cooling could be administered effectively, and what adverse side effects might occur.1

Cooling the brain is known to prevent neurological problems in patients recovering from cardiac arrest. But previous studies from Sweden have questioned the merits of induced hypothermia. Most of the current methods for therapeutic hypothermia may not be initiated before return of spontaneous circulation.

Researchers in the current study, alongside people working in emergency and critical care clinics, set up a trial for 108 cardiac arrest patients. The medical staff administered treatments with or without pharyngeal cooling to patients at random, and subsequently recorded success rates of resuscitation and physiological conditions, including temperature both at the body core and tympanic temperature, mechanical or temperature damage to the pharynx, inflammation and blood platelet levels.

The results of the trial indicated effective cooling of tympanic temperatures, with no observed adverse side effects. In addition, incidences of inflammation and blood-clotting disorders were reduced in patients receiving pharyngeal cooling. As the researchers report, “In conclusion, it appears that the initiation of pharyngeal cooling is safe and feasible before and shortly after recovery of spontaneous circulation in the emergency room.”

Pharyngeal cooling was begun during chest compression as soon as patients entered the emergency room or on return of spontaneous circulation (ROSC) if ROSC returned before entering the emergency room.

In the current study pharyngeal cooling was administered using a pharyngeal cuff, a vinyl chloride tubular structure fitted into the upper oesophagus and pharynx. Saline solution at a temperature of 5 °C was perfused into the cuff at a rate of 500 ml min−1 and pressure of 50 cm H2O.

The temperature was chosen to be above freezing so that ice did not form, and treatment duration was also limited to 2 hours to avoid damage from the cold. The pressure was chosen to be below 60 cm H2O to avoid neuropathy – nerve damage – which has been reported with the use of equipment similar to the cuff.

Low mechanical damage to the pharynx was thought to be largely due to similarities between the cuff and other medical instruments, as clinicians administering the treatment were familiar with using similar equipment.

Patients aged 14–89 years old were considered eligible for the study within 15 minutes of collapse if they had suffered cardiogenic cardiac arrest or had been resuscitated from non-cardiogenic arrest by medical personnel. Of the 818 patients that met the criteria, 113 were enrolled on the study. The researchers believe that the relatively small size of the fraction of eligible patients that were enrolled does not affect the quality of the study data because the random selection for treatment with or without pharyngeal cooling was undertaken after enrolment, and exclusion from the study after enrolment was very low.

Pharyngeal cooling cuff (left) and circulator (right)

Pharyngeal cooling cuff (left) and circulator (right)


1. Takeda Y, Kawashima T, Kiyota K, et al. Feasibility study of immediate pharyngeal cooling initiation in cardiac arrest patients after arrival at the emergency room. Resuscitation 2014;pii:S0300-9572(14)00756-4.

Published on: October 31, 2014

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