A prospective, multicenter pilot study to evaluate the feasibility and safety of using the CoolGard™ System and Icy™ catheter following cardiac arrest
Introduction
Each year there are at least 300,000 sudden cardiac deaths in the United States [1]. Of these, nearly 70% occur outside the hospital [2]. As many as 20% of patients will survive an out-of-hospital cardiac arrest [3], [4] although considerably lower numbers have been reported [5], [6], and substantially higher (∼40%) rates have been achieved with the advent of automated external defibrillation [7]. Survival after an in-hospital cardiac arrest is even less certain [8], [9], [10].
Most patients who do not awaken after cardiac arrest will die. Many of those who survive are left with enduring and devastating neurological deficits due to global cerebral ischemia [11], [12]. In recent placebo controlled trials [13], [14], survival with poor neurological outcome occurred in 6–11%.
For successful resuscitation, it is not only important to stop cardiac ischemia as quickly as possible but also to overcome post-resuscitation tissue injury [15], [16], [17]. The ability of tissue to survive anoxic no-flow states is reduced in normothermia compared with hypothermia [17], [18]. Clinical and experimental studies suggest a pronounced protective effect of hypothermia, especially in models of global forebrain ischemia mimicking the cerebral consequences of cardiac arrest [13], [14], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30].
To date only systemic external hypothermia has been shown to be efficacious as a neuroprotectant after global cerebral ischemia in humans. The procedure is laborious and time intensive. Average or median times to achieve cooling to 33 °C using external cooling devices has been 480 min [14], 287 min [29], and 301 min [30] in recent studies. Experimentally, rapid attainment of the target temperature may be more beneficial and offer better neuroprotection than slow cooling [31].
Endovascular methods of cooling may provide rapid cooling and temperature control for use in cardiac arrest patients. One such system has been developed by the Alsius Corporation (Irvine, CA, USA), where cooled saline solution is pumped through an intravascular heat exchange catheter placed in the inferior vena cava via femoral vein. We undertook this trial to assess the safety and feasibility of using this system for endovascular cooling after cardiac arrest. We also aimed to assess the speed of endovascular-induced hypothermia and the ability of the endovascular cooling method to maintain hypothermia within a tight range.
Section snippets
Study design and patient selection
This was a prospective, non-randomized, three clinical center trial performed in the United States, between March 2001 and September 2002, in which patients who had been successfully resuscitated following primary cardiac arrest, but had not regained consciousness (GCS≤8), were treated with moderate hypothermia induced by the CoolGard™ System with the Icy™ catheter. Patients were enrolled in the study when the following criteria were met: 18 years of age or older, suspicion of primary cardiac
Patients
A total of 13 patients were enrolled in this study; six males and seven females with a mean age of 60.2±18.7 years (range 32–83 years). “Down time”, was defined as the interval between onset of cardiac arrest and return of spontaneous circulation (pulse). When the recorded down time was imprecise (e.g. 15–20 min), the mean value between the two extremes given was used (in above example, 17.5 min). The average estimated down time was 14.3 min, with down time not reported for one subject. Down time
Discussion
After several positive pilot studies using moderate hypothermia (33–34 °C) following cardiac arrest in humans were reported [26], [27], [28], [30], Bernard et al. in an Australian study [13] confirmed in 77 randomized patients a significant benefit in favor of hypothermia. The Hypothermia After Cardiac Arrest Study Group [14], studying 275 patients in a randomized controlled trial, also showed significant improvements in neurologic outcome and mortality 6 months later. Based on these results,
Acknowledgements
Dr. Al-Senani was supported by NIH Training Grant NS007412. This study was funded by the Alsius Corporation. Study concept, design, monitoring, data analysis, and manuscript preparation were a cooperative effort between Alsius and the investigators. Drs. Grotta, Graffagnino, and Chung receive consulting fees from Alsius. Drs. Palmer and Collins are employees of Alsius.
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