Therapeutic Hypothermia (TH) or intentional cooling of the human body was found to be beneficial after a person survives a cardiac arrest. Cardiac arrest, by definition, is a lack of adequate blood flow to the vital organs in the body due to a cessation of heart pumping function. The lack of blood and oxygen supply to the organs could lead to a severe and irreversible damage.

Our brain is the most sensitive organ to a lack of oxygen supply. Just a few minutes of no blood flow to the brain could lead to anoxic encephalopathy or brain damage from the lack of oxygen. Anoxic encephalopathy has a spectrum of manifestations. In it’s most severe form, the patient never regains consciousness and remains in a permanent vegetative state. The less severe forms of this condition may lead to disturbances with memory, cognition and emotions etc.

It has been recognized that it is possible to “protect” the brain from the harmful effects of anoxia (lack of oxygen) by slowing down it’s metabolism. One of the ways to do it is to cool the brain down. Cooling just the brain is technically difficult but not impossible. Recent research suggests that just the brain can be cooled off by using intranasal cooling (cooling through the patient’s nose). Cooling the whole body including the brain is more feasible.

There are two main methods of cooling: external and internal. External cooling is achieved by applying ice packs, cooling blankets and special cooling pads to the surface of the body. The internal cooling method is by using cold intravenous fluids and inserting special cooling catheters into the bloodstream to cool the patient’s blood directly. Using both methods at the same time is the most effective technique.

Medical literature supports cooling after cardiac arrest to improve recovery and survival. Unfortunately, the adoption of this treatment modality in the clinical practice has been slow. There are multiple barriers including complexity and labor intensity associated with the institution of therapeutic hypothermia.

A recent paper published in the Journal of Trauma, suggest that hypothermia may also attenuate acute lung injury associated with hemorrhagic shock (shock due to bleeding). By modulating the inflammatory response caused by severe bleeding, hypothermia decreased the incidence of lung injury in rats. This was an animal study and the real life clinical study needs to be conducted to confirm the results.

Yet, it is becoming obvious that therapeutic hypothermia has it’s role in treating critically ill patients. The indications for using hypothermia will likely be expanded in the years to come. More effective and sophisticated cooling methods might also expand it’s use by providing more rapid and controlled cooling.

In my practice I see quite a few patients with severe traumatic brain injury. Previously in this blog we talked about decompressive craniectomy as a treatment option for head injured patients. Another aspect of daily management of these patients that has significant impact on recovery is fever control. There is no doubt that high fever worsens neurological outcome in patients with brain injury. Yet, cooling those patients to subnormal temperatures (32-33 degrees C) was not shown to be beneficial. I believe there are too many confounding factors in trauma patients making them poor candidates for cooling.
How do we maintain euthermia (normal temperature) in these patients? I have tried multiple modalities in my practice: ice packs, Tylenol, cooling blankets, fans, gastric/bladder lavages. High fever in neurological patients is often hard to control. None of the options mentioned above work consistently well. The newer fever control modality that I have tried is endovascular cooling. Inserting a special cooling catheter (see picture above) with a cold saline circulating thru 3 or more coaxial balloons into a central vein makes cooling these patient much more consistent and controlled.  This is only one of the few new (intravascular or external) cooling devices available. It would be interesting to see if anybody has more experience with any other devices or techniques.
 

Reviewing recent medical literature, I came across an interesting study from Europe. The investigators in several European cities were using an intranasal cooling device to cool the patients having cardiac arrest. I am myself very interested in cooling cardiac arrest patients. There is a body of evidence that the patients have better neurological outcomes when therapeutic hypothermia (cooling to 32 – 33 degrees Celsius) is utilized. I have been using an intravascular cooling system in my ICU. When cooling is being initiated in ICU, there is always a delay in time. The sooner this treatment is started the better our chances on preserving the neurological function. Ideally, the cooling should be initiated immediately at the scene. Using cooling packs and cold saline is somewhat cumbersome and might interfere with the resuscitation. A company from San Diego came up with an intranasal cooling device called RhinoChill to provide cooling immediately after the cardiac arrest. It sprays a rapidly evaporating chemical onto nasal mucous membrane, thus, cooling it down. It does make sense physiologically. The inner surface of the nose is reach in vascular supply and it’s proximity to the brain makes it an ‘ideal’ place for cooling. The data is promising so far. If it goes mainstream, we might see it next to the cardiac defibrillators at the airports (just kidding).

What is a better way to control high fever in patients with severe traumatic brain injury or stroke? What is a better option: External or Endovascular? Please share your experience.