Table of Contents
Introduction
The invention of anesthesia drugs and development in the field has been a blessing in modern medicine. The advent of general anesthesia facilitated the development of many surgeries that were once beyond belief. Many types of anesthesia, like general anesthesia, local anesthesia, regional anesthesia, etc., are commonly used in every part of the world daily. However, there can be complications that become unpredictable in some cases. It could be due to the chemicals in the anesthesia drugs or their pharmacological properties, and affect the central and peripheral nervous system. This article deals with the neurological complications of anesthesia.
What Are Neurologic Complications of Anesthesia?
When the anesthesia given causes an unfavorable effect on the patient’s nervous system, either the central or peripheral nervous system, it is considered a neurological complication of the anesthesia. This is a very rare scenario, but it would be very complicated if it happened. It is one of the most common fears of an anesthesiologist and the healthcare team performing the surgery.
How Do Neurologic Complications With Anesthesia Occur?
Though rare, complications affecting the nervous system can be devastating if they occur. Neurological complications with anesthesia can occur through many mechanisms. Some of them include injuries to the blood vessels, direct trauma, and infectious processes like abscesses. The symptoms of neurological anesthesia complications may be seen in perioperative procedures, surgical factors, iatrogenic injury (an injury caused by the healthcare professional during the procedure or treatment), or nerve compression (occurs when an increased pressure occurs on the peripheral nervous system). In some cases, a neurological condition that the patient already has prior to the surgery may get aggravated and appear as a complication of anesthesia. Sedation can also affect the early clinical evaluation of recovery from anesthesia. It can mask some of the early complications.
After Neuraxial Anesthesia: In neuraxial anesthesia, the anesthesia drug is placed in the epidural space. The complications seen can include:
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Nerve Damage After Epidural Hematoma: This is one of the rarest complications following anesthesia, occurring only two per 100,000 cases. It is important to diagnose this complication as soon as possible, as the damage becomes more severe with time. Vague sensory symptoms like tingling of the tongue, dizziness or ringing sound in the ears, and flaccid paralysis of the lower limbs are the early signs of nerve damage following epidural hematoma. Neurogenic bowel and bladder are some of the later signs.
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Complications Due to Infections: Infections like meningitis or epidural abscess can also cause neurological defects following the use of anesthesia drugs. These are curable, but diagnosing the cause can be challenging. The most common sign of an infection is pain, which is masked by an analgesic following a surgical procedure. Fever and elevated inflammatory markers in the serum can be other indicators to look out for in an infection. Some cases of meningitis can show seizures.
After Peripheral Nerve Blocks: Peripheral nerve blocks are another commonly used type of anesthesia, especially in orthopedic procedures. It is considered to reduce post-operative pain and the need for opioids following the surgery. An existing neuropathy (weakness and pain in the nerves), hypothermia (a dangerous drop in the body temperature), hypovolemia (reduced blood or other fluids in the body), hypoxemia (decreased levels of oxygen), hypotension (reduced blood pressure), electrolyte or a nutritional imbalance increases the risk of neurological complications following a peripheral nerve block. Studies show that most risk factors for neurologic anesthesia complications depend on the patient. Some of them, like diabetes, the use of tobacco and alcohol, and obesity, can be modified to reduce the risk.
How Are Neurologic Complications With Anesthesia Diagnosed?
In order to diagnose the complications in the nervous system, the patient must be advised to note any changes or difficulties in their body as the anesthesia wears off. They should be advised to perform a self-observation and point out any difference they feel, from the ones they consider very silly to the most complicated ones. Often, patients think of some difficulties in their bodies as a usual part of the anesthesia due to the lack of awareness. As a result, they fail to report it to their medical team and go unnoticed. Later, it is found to be a complication when the patient returns with more severe symptoms.
A neurologic evaluation might not be successful during the early pre-operative period, as it can be altered by many other factors. However, a neurologist and an anesthesiologist might have a better chance of predicting the possible postoperative complications following anesthetic drugs in a patient. Some complications like post-dural headaches can be transient and do not require any medical intervention.
What Are the Neurologic Complications After Anesthesia?
Some of the neurological complications following anesthesia include:
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Post-operative Delirium: It is an acute complication following anesthesia. The thinking capacity of the patient is altered, resulting in a confused state. It can be associated with negative outcomes like mortality, increased duration of hospital stay, persistent cognitive decline, and prolonged need for intensive care if not managed appropriately. It can be an indication of an underlying neurological condition like early dementia (memory loss). In most cases, it remains undiagnosed. Without a targeted question, patients appear to be normal or misunderstood as tired in most cases. The Confusion Assessment Method and the Confusion Assessment Method for the Intensive Care Unit are reliable and user-friendly algorithms developed to diagnose delirium. Anesthesiologists generally do not diagnose the condition as the patient leaves their care when the symptoms are shown.
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Postoperative Cognitive Decline (POCD): It is usually seen in elderly patients. Studies show that surgeries should be avoided in people over 50 years, as the risk of cognitive decline is very high in these people. Another study shows that people over 50 years old undergoing surgeries have POCD that may last for days or months. However, the relationship between age and cognitive decline is still debated and requires more research.
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Stroke: The loss of blood supply to the brain causes stroke. This could be hemorrhagic (bleeding in some blood vessels) or ischemic (loss of blood supply). It is commonly seen after heart surgery and carotid endarterectomy (a surgical procedure to remove the fatty deposits in the carotid artery).
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Spinal Cord Ischemia (SCI): This is seen in surgeries aimed at repairing aneurysms (a weakened blood vessel resulting in a bulge in the wall of the vessel) in the chest and abdominal areas. When the patient shows signs of SCI on emergence from anesthesia, it is called immediate-onset SCI. It could be due to the interruption of the blood supply to the spinal cord during some point in the surgery. Delayed-onset SCI could occur due to a thrombosis in the post-operative period. The post-operative mortality in patients with SCI is as high as 50 percent.
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Postoperative Visual Loss: This is a rare scenario, and is associated with surgical procedures in the eye. Being a rare condition, finding preventive strategies is challenging.
Conclusion
Analyzing the patients at a higher risk of neurologic complications after anesthesia should be considered an essential part of surgery. Selecting the right anesthetic drug at the right dose and route of delivery is important in every case. Monitoring the drug delivery using an ultrasound or magnetic resonance imaging can help to reduce complications. The use of anesthesia should be with caution while administering to pregnant, pediatric, and geriatric patients. The potential neurological complications should be considered while administering anesthesia drugs to these categories of patients.
