Cardiac Arrest and Coma in Patients with Atrial Fibrillation

Myocardial infarction

Dear Director Huang,
I would like to ask you a few questions regarding a patient with atrial fibrillation who has a history of a mild hemorrhagic stroke in the basal ganglia several years ago.
The patient was admitted to the intensive care unit due to myocardial infarction and pulmonary edema.
Prior to admission, the patient was mobile, although there was some weakness in the right limbs.
After 3-4 days in the ICU, X-rays showed no signs of edema, and CPK levels had decreased to 550.
The patient was also undergoing respiratory training in preparation for extubation.
However, early in the morning, the patient suddenly experienced cardiac arrest but spontaneously regained a heart rate of 67 beats per minute after less than a minute.
Unfortunately, the patient remained in a comatose state with a Glasgow Coma Scale of 2T.
Over the past month, the patient has slowly begun to open their eyes and move their limbs, but there is no ability to communicate with the external environment.
An EEG indicated diffuse cerebral changes.
I would like to ask you the following:
1.
In the ICU, with mechanical ventilation and oxygen levels set to maximum, could a cardiac arrest lasting less than one minute lead to such severe coma?
2.
According to nursing records, the patient's blood pressure was 66/33 mmHg, and heart rate dropped from 45 to 0 suddenly.
Is it possible that prolonged low blood flow could cause hypoxia?
3.
The patient was diagnosed with acute renal failure two days prior, attributed to the myocardial infarction seven days ago.
Despite having no history of diabetes or insulin dependence, the patient has experienced episodes of both hypoglycemia and hyperglycemia requiring insulin.
The physician noted that low blood pressure correlates with hypoglycemia (the blood sugar level was 35 at that time).
Could prolonged low blood sugar levels have contributed to the cerebral changes observed?
I appreciate your insights on these three points.
Thank you.

Cai, 30~39 year old female. Ask Date: 2005/06/21

Dr. Huang Yingzhe reply Neurology

Dear Mr.
Tsai,
This is Dr.
Huang Ying-Che, the Director of the Neurology Department at Tainan Hospital, Ministry of Health and Welfare.
1.
It is possible that due to pre-existing stroke damage in the brain and renal failure, there are significant functional issues.
2.
It is difficult to determine.
3.
It is possible, but under monitoring in the intensive care unit, it is not likely to occur.
Wishing you good health and all the best from Tainan Hospital!

Reply Date: 2005/06/21

More Info

Understanding cardiac arrest and coma in patients with atrial fibrillation (AF) involves a multifaceted approach, especially when considering the patient's history of hemorrhagic stroke, recent myocardial infarction, and acute kidney injury. Let's address your questions systematically.

1. Could a brief cardiac arrest in the ICU lead to severe coma?
Yes, even a brief episode of cardiac arrest can lead to significant neurological impairment, particularly if it results in a period of inadequate cerebral perfusion. The brain is highly sensitive to oxygen deprivation, and even a few minutes without adequate blood flow can cause irreversible damage. In your case, the patient experienced a cardiac arrest with a blood pressure of 66/33 mmHg and a heart rate that dropped to zero. This indicates a severe drop in cardiac output, which could lead to hypoxic-ischemic injury to the brain. The duration of the cardiac arrest, even if brief, combined with pre-existing conditions such as atrial fibrillation and a history of stroke, can exacerbate the risk of neurological deficits.

2. Could prolonged low blood flow lead to hypoxia?
Absolutely. The patient's hypotension (BP: 66/33 mmHg) indicates that there was insufficient perfusion pressure to maintain adequate blood flow to vital organs, including the brain. This low blood pressure, coupled with a heart rate of 45, suggests that the patient was in a state of shock, which can lead to multi-organ dysfunction. Inadequate blood flow can cause a cascade of events leading to cellular injury and death due to lack of oxygen and nutrients. The brain, being highly dependent on a continuous supply of oxygenated blood, is particularly vulnerable to these changes. The resultant hypoxia can lead to diffuse brain injury, as indicated by the EEG findings of diffuse encephalopathy.

3. Could prolonged hypoglycemia contribute to brain injury?
Yes, prolonged hypoglycemia can indeed lead to neurological damage. The brain relies on glucose as its primary energy source, and low blood sugar levels (as noted with a blood sugar of 35) can result in neuronal injury and dysfunction. In patients with fluctuating blood sugar levels, particularly those who are not diabetic but require insulin, there is a risk of hypoglycemic episodes, especially in the context of acute illness and stress. The combination of low blood pressure, low blood sugar, and the patient's history of cardiac issues could synergistically contribute to the observed diffuse brain changes.
In summary, the patient's condition is a complex interplay of several factors: the acute myocardial infarction leading to cardiac arrest, the resultant hypoperfusion causing hypoxic injury, and the potential impact of hypoglycemia on brain function. Each of these elements can contribute to the severity of the coma and the overall neurological status of the patient.
It is crucial for the medical team to monitor the patient's neurological status closely and consider interventions that may help improve cerebral perfusion and metabolic stability. Rehabilitation efforts may also be necessary to address the patient's motor deficits and cognitive function as they recover. Regular follow-up with neurology and cardiology specialists will be essential in managing this patient's complex needs.

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