Cath Lab Digest

There is a growing body of evidence that therapeutic hypothermia (TH) in patients who are comatose after cardiac arrest improves neurologic outcomes.^1,2 This is an exciting addition to traditional percutaneous coronary intervention (PCI) therapy for ST-elevation myocardial infarction (STEMI) patients, since brain injury is the ultimate cause of death in 68% of patients who are resuscitated out-of-hospital but die before discharge.³ Enloe Medical Center, a 298-bed hospital in northern California, had an existing hypothermia protocol, but concerns were raised when patients would present with an arrest that left them unconscious, and they needed a heart cath. Is combining these therapies safe and effective? In the first 90 minutes, which should take precedence? How do you make the staff comfortable and competent with using TH during a PCI? What additional considerations are there when these therapies are combined?

The literature does support the combination of PCI and TH.^5-10 With the addition of TH, it is possible to not only save patients’ lives but to have favorable neurologic outcomes as well. One study found patients who received TH before, during, or immediately after PCI did have a significant improvement in neurologic outcomes, compared to those who did not receive TH.¹¹ Another study treated patients with PCI and then TH if they were still comatose after the procedure, and found that 68% of these patients had a favorable neurologic outcome.⁷ In a third study, 56% of patients who underwent PCI and TH had favorable outcomes compared to 26% who were treated with neither.⁹ Yet another study found a trend towards improved neurologic outcomes, although this was not found to be statistically significant.¹⁰ It is also possible that adding TH may reduce infarct size if started before PCI.^5,6

But even though the evidence indicated this was a safe and effective therapy, there was still some reluctance to perform PCI on hypothermia patients, or hypothermia on STEMI patients. We had to get buy-in from the staff. We created separate training programs for different units. Emergency room staff and cath lab staff received in-services with hands-on training regarding which patients are appropriate for this therapy, how this therapy can change lives, how to set up equipment, and what to monitor in the initial stages. The ICU training was also hands on, but more focused on the physiologic changes of hypothermia, the importance of adequate sedation, and how to re-warm patients appropriately. The existing protocol was reviewed with both sets of staff. 

We found that the method of cooling needed to be compatible with performing a heart cath right away. This meant that the equipment needed to be portable, quick to set up, radiolucent, and provide access to the groin areas and to the chest in case defibrillation was needed. Enloe already had the Blanketrol (programmable body temperature regulation) (Cincinnati Sub Zero, CSZ Medical) for hypothermia patients, and we decided to use the Gelli-Roll (a reusable warming and cooling gel pad) (Cincinnati Sub Zero, CSZ Medical) whenever TH was initiated in the ER or cath lab. The Gelli-Roll can be set up ahead of time, can be transferred with the patient, and it leaves the chest and groin areas free. The drawback of this system is that the unit must be off or in standby while images are taken; however, it does stay cold for the time it takes to perform the procedure.

Our cooling protocol includes giving a 20ml/kg bolus of 4°C normal saline. During staff training, we realized that some of the staff had concerns with giving a large fluid bolus to patients who had a compromised heart. By reviewing the literature, we were able to reassure nurses that cold fluid boluses were used in many trials without adverse affect, and may improve hemodynamic stability by preventing hypovolemia.¹²

We also had to decide which method of temperature monitoring we would use. We considered esophageal monitoring, but it would have required extra training on inserting the esophageal probe, and there was the risk of dislodgement while transferring the patient. We decided to use bladder temperature monitoring, since it would require no extra training and the risk of dislodgement was lower. The staff was educated that the bladder temperature might not be as accurate if urine output is very low.¹³

Then there was a question of timing and prioritization. TH “should probably be initiated as soon as possible after return of spontaneous circulation but appears to be successful even if delayed (e.g. 4-6 hours)”.¹⁴ For patients with STEMI, the American College of Cardiology (ACC) and American Heart Association (AHA) recommend PCI within 90 minutes of presentation to a facility, and encourages even faster times.¹⁵ One study found that adding TH did not result in delays of PCI past 90 minutes.¹⁰

In practice, it is hard to say which therapy should be started first every time. If the cath lab team needs to be called in, it makes sense to start the TH while the team is arriving. Or, if the team is ready to go, it may make sense to do the procedure and then start TH afterwards. Either way, everything should be done to ensure the PCI is completed within 90 minutes and the TH is started as soon as possible, either before or after PCI.