Hypothermia and Brain Arrest Protocol
Nitin K Sethi, MD
Assistant Professor of Neurology
New York-Presbyterian Hospital
Weill Cornell Medical Center
New York, NY 10065
Recently I attended the American Academy of Neurology (AAN) annual meeting held in Seattle. One of the topics of interest was the use of hypothermia to improve the outcome of patients after cardiac arrest or traumatic brain injury. Since the neurological outcome of patients presenting after a cardiac arrest (whether in hospital or out in the field) is usually dismal, I thought this shall be a good topic for me to discuss here.
The brain needs oxygen to survive and does not do well if deprived of oxygen. Hypoxia (lack of oxygen) occurs after cardiac arrest (the circulation of blood to the brain is interrupted when the heart stops beating as occurs in a cardiac arrest). If the circulatory flow is not rapidly reinstituted (meaning the heart is not restarted) irreversible neuronal death ensures. The usual scenario is as follows. A patient suffers an out of hospital cardiac arrest. A call goes out to 911. The EMS team is on the scene shortly. The patient is noted to be either in cardiac arrest (we call this asytole) or the heart is beating but ineffectively and there is no palpable pulse (we call this ventricular fibrillation). The heart is revived by either injecting drugs or shocking (with the help of a hand held defibrillator) and there is return of palpable pulse. Alls well you might say but the story is far from over!!!
Even though the heart has been revived the brain has taken a hit. During the time when the heart had stopped, there was a lack of blood flow and oxygen to the brain and irreversible neuronal death has occured. So we have a patient whose heart is now beating but the brain is dead. This patient may never make a meaningful neurological recovery. Some of these pateints end up in persistent vegetative state (PVS) or minimally conscious state (MCS).
By the time, I as a neurologist am called to see the patient, there is precious little I can do. The brain is already dead!!! I can just prognosticate and tell the family that their loved one shall never have a meaningful neurological recovery. In other words, I help them in deciding when to pull the plug!!! Nothing makes me feel more helpless. I did not enter neurology to prognosticate, I entered neurology and medicine to save a life and heal.
So that is why hypothermia for cardiac arrest sounds so promising. Recent studies have shown that if the brain is cooled (there are different ways to cool the brain from using high tech cooling blankets and beds to more primitive but equally effective techniques like bags of ice) to 32-34 degree centigrade for 12-24 hours following cardiac arrest, neuronal death does not occur. Till the heart is revived, the brain remains viable!!!
This research has led to the institution of a Brain Arrest Protocol in some big academic centers. Once a patient who has suffered a cardiac arrest is received, hypothermia protocol is immediately instituted. This has resulted in improved survival rates in these critically ill patients. Patients not only survive but they survive with good neurological outcomes.
If the hypothermia is prolonged or if the temperature is lowered too low it can cause complications and increase the risk for sepsis and cardiac arrhythmia. Hence this protocol is at present still in its infancy but I have a feeling this shall become a standard of care very soon.
In this post I thought I would talk a little about persistent vegetative state (PVS) and minimally conscious state (MCS). Though this topic may not concern many of you, I feel it should be discussed as the question of PVS is raised frequently by family members of patients who are in coma.
Doctor is he brain dead? Would he wake up? If yes when? Is he going to be a “vegetable” for the rest of his life?
So what is PVS and how does it differ from brain death. I shall try to make this simple and explain with the aid of a crude example. Let us assume a person suffers major head trauma in a motor vehicle accident. He is brought to the hospital and CT scan shows extensive bleeding in the brain. He is in the intensive care unit on a mechanical ventilator while his blood pressure is been supported with the help of medications (we call such medications vasopressors). Now a neurologist is called to see him regarding prognosis. On examining him the neurologist notices that his pupils are dilated and fixed (do not react to light) and the rest of his brain stem reflexes are also not elicitable (please see my previous post on brain death). An EEG is ordered to confirm the diagnosis of brain death. The EEG shows no cortical (brain) activity above 2 microvolts (meaning it is essentially a flat line) and is thus consistent with electrocerebral inactivity (ECI). SUCH A PERSON IS BRAIN DEAD AND CAN THUS BE REMOVED FROM THE VENTILATOR (OF COURSE WE TAKE THE FAMILY’S WISHES INTO CONSIDERATION). BUT FOR TECHNICAL PURPOSES HE IS DEAD. Remember what I said earlier one cannot die twice, once when the brain stops and once when the heart stops.
Now lets take the second scenario. The neurologist examines the patient and notices that he does not respond to verbal commands, does not respond to a painful stimuli such as a pinch but the brain stem reflexes are intact. His pupils react to light, he gags when the back of his throat is touched, he takes a gasp on his own when he is temporarily disconnected from the ventilator. THE NEUROLOGIST RIGHLY SAYS” PATIENT IS NOT BRAIN DEAD BUT HIS PROGNOSIS FOR RECOVERY IS GUARDED“. Time goes by say about a week. The patient is now still in the intensive care unit but at times responds when he is stimulated, does not open his eyes or talk but moves his arm if he is pinched. More time goes by say about 2 weeks. The patient is now opening his eyes. He now has a tracheostomy and slowly is been weaned off the ventilator. He is still not able to talk and does not interact with any of his nursing staff or his family. More time goes by, the patient has been weaned off the ventilator. He is now out of the intensive care unit and is transferred to the hospital floor. A neurologist’s opinion is asked for as “the patient does not respond”. The neurologist examines the same patient whom he had seen in the aftermath of the trauma. 10 weeks have gone by since the injury. The neurologist finds that the patient open his eyes spontaneously, at times even yawns, he is told by the family at bedside that the patient has sleep wake cycles (meaning he sleeps at night and then wakes up after some time just like any other “normal” person). As the patient’s mother walks into the patient’s room, the neurologist notices that the patient tracks her with his eyes for a short time when she enters. But there is no meaningful interaction of the patient with his environment. It is as if the patient is there but not there. He does not make purposeful eye-contact with anyone. There is nothing in his actions to suggest that he is truly responding to those around him or interacting with them. The tracking movements of the eyes are semipurposeful and so is the yawning behavior–more like a reflex if not anything else.
A person like the one above may be labelled as one who is heading into the persistent vegetative state (PVS) category. You can imagine the delimma for the family members if you tell them that though the patient may remain “alive” for years, he shall never have any meaningful neurological interaction and hence it is better to let him go. “BUT DOCTOR HE IS ALIVE, HE YAWNED TODAY, HE LOOKED AT ME WHEN I WALKED INTO HIS ROOM”: they will say.
Patients who are truly in the PVS shall never recover any meaningful neurological interaction with the environment–this is by defination. But as is true in medicine, everything is not black and white. there are shades of grey. Patients who meet the criteria for PVS but then who later on start showing “some” recovery. Some purposeful goal directed behavior starts emerging. So a new category of minimally conscious state has not come into the literature. There have been some studies done to show that the brains of these patients do actually respond and they are far from a PVS. A lot of research is now been carried out to determine how we can benefit these patients.
If the right procedure is followed and the neurological examination and relevant investigations are carried out and repeated if required after an interval of time, most of these patients can be rightly categorised into the brain dead, PVS or MCS category thus avoiding confusion and anguish to the family members.
Nitin Sethi, MD