Perelman School of Medicine at the University of Pennsylvania
Center for Resuscitation Science

Cold Fluids & Temperature

November 19, 2010

Q: What is the danger of infusing large quantities of cold IV fluids via a SC, IJ or PICC? My understanding is potential arrythmias.

A: This is a theoretical concern, that is why we recommend chilled saline via peripheral IVs, preferably in the antecubetal location. Adequate peripheral access (2 minimum) should be obtained in the peri-arrest period and these can be used for induction of TH while central venous access is obtained.

- David Gaieski, MD

August 6, 2010

Q: At our small community hospitals our ED docs are concerned about inserting alines. Without residents and a "cool team" on call, who inserts the aline is still undetermined. We will have to call the on call surgeon to come in and insert the aline.

My concern is that the patients will be at goal when they arrive in the ICU, or even in the ED after EMS starts the process. I know getting a radial aline will be very difficult, how about a femoral aline, have you had trouble with that when the patients are cooled?

A: We would not delay implementation of therapeutic hypothermia because of questions of who is going to place the arterial line. If the patient is at goal on arrival to the ICU, the benefits of that probably far outweigh the increased difficulty of placing a radial a-line in a patient vasoconstricted from therapeutic hypothermia. You have to work within the resources of your system and if the emergency physicians are not going to place a-lines but will start hypothermia then those constraints can be worked within to set up a successful program.

You are correct in saying that a radial arterial line may be more difficult to obtain in these patients but experienced providers such as the on call surgeon you are consulting should be able to achieve placement of radial a-line in a number of patients (especially if they are using ultrasound to assist them). Femoral a-lines are a completely reasonable alternative and remain easier to place properly in hypothermic patients because of the size of the femoral artery. Our standard approach is not to delay induction of therapeutic hypothermia to attempt a-line access; to make a few attempts at a radial a-line, then proceed with femoral access if necessary, with or without ultrasound guidance.

Hope this is helpful.

- David F. Gaieski, MD

July 27, 2009

Q: I can find references that say that overshooting the target temperature (too cold) is harmful and that rapid rewarming can create instability. Is there literature that addresses potential harm of mild fluctuation in temperature during the treatment period of 24 hours?

One of the selling points used by many of the equipment vendors is the claim that their equipment is superior at maintaining the temperature exactly at 33 degrees a high percentage of the time. Is there evidence to indicate that this is most beneficial or that failure to provide this is potentially harmful? Is time frame from initiation until reaching target temperature a higher priority in achieving the best outcomes or is steady maintenance a higher priority? Have protocols that use only iced IV fluids and conventional cooling blankets with less precise temperature maintenance been associated wtih worse outcomes?

A: As you have pointed out there are references for overshooting the target temperature (including my colleague Raina Merchant's paper from 2006) and for the potential risks of rapid rewarming. There is less available on the clinical relevance of variations from the target temperature during maintenance phase related to different devices. Hoedemaekers and colleagues published a paper in Critical Care looking at the speed of cooling and degree of variation with different devices but this didn't address clinical outcomes/relevance (Hoedemaekers CW, et al. Crit Care. 2007; 11(4): R91). It is highly unlikely that 0.3 degrees C variation versus 0.6 degrees C variation is clinically relevant. There currently is no evidence that such tight control is clinically relevant--that doesn't mean data won't emerge at any point.

A large French study comparing surface cooling to endovascular cooling has been completed and is being prepared for press. I don't know the results but one of the questions they will likely address is the precision of maintenance of target temperature. Joe Ornato in Richmond has discussed improvement in their outcomes after they switched from surface to endovascular cooling and attributes some of the improvement to the speed of cooling but this is not a randomized controlled trial.

As you have pointed out many of these details are "selling points" of different devices and focusing too much on those points is, to some extent, missing the forest for the trees. The important point is cooling and high quality ICU care. The recent publication by Friberg and colleagues (Neilson et al, "Outcome, Timing, and Adverse Events in Therapeutic Hypothermia After Out-of-Hospital Cardiac Arrrest," Acta Anesthesiol Scand 2009; 53: 926-936) doesn't discuss variation from goal temperature but does suggest NO relationship between time to target temperature and outcome (median time from arrest to goal temperature [< 34 degrees C] was 260 minutes, IQR 178-400 minutes). I always try to keep in mind that the two landmark studies (NEJM, 2002; 346) used fairly primitive cooling equipment (Bernard-->ice packs; HACA-->forced cold air blankets that were ineffective enough that 70% of the patients required supplemental ice packs) to achieve the statistically significant improvements in neurologic outcomes (Bernard and HACA) and mortality (HACA) that are the foundation for current therapy.

- David Gaieski, MD

February 2, 2009

Q: I just read the article about you, Benjamin Abella and your research on hypothermia in Popular Science (Carnett, J.B. "Cold Relief" Popular Science 274(2) Pg. 54-59). Very interesting, but I was struck by how hard it was to get someone cold quickly. I just watched a TED talk by Peter Ward on mass extinctions and how breathing hydrogen sulfide can help lower body temperature. I don't know much about animal physiology, but perhaps breathing hydrogen sulfide while being on an "IV slushee" would make a person become colder faster.

A: It turns out that this is a gas of great current interest, it also appears to have cell-protective properties in small quantities. A number of laboratory experiments in simulated cardiac arrest are underway using this fascinating molecule … stay tuned! Not quite ready for human testing, I suspect. It's a tricky gas, and can be toxic at higher doses.

- Benjamin S. Abella, MD