MEDICALLY INDUCED COMA: WHAT IT IS, HOW IT WORKS, WHO BENEFITS, AND RECOVERY OUTCOMES

Medically Reviewed by Dr. Rae Osborn, Ph.D. and Updated on July 03, 2024

While a coma is perceived to be a scary event with a high chance of mortality, under the right circumstances, it may just save a person’s life.

The below article aims to explore what a medically induced coma is, when a healthcare practitioner might prescribe one, and how it might help to enhance recovery outcomes in the emergency ward.

What is a Medically Induced Coma?

A medically induced coma is a reversible state of deep unresponsiveness that is brought about by sedative administration in an attempt to protect the brain from traumatic damage. The sedatives trigger unconsciousness by suppressing various aspects of brain activity. This helps to lessen the energy requirements of the brain that would otherwise be used to sustain conscious arousal, enabling it to spend more energy on regeneration. Occasionally, doctors may resort to using cryotherapy or extreme hypothermia to help achieve or complement the effects of a medically induced coma^[1].

There are varying degrees of unresponsiveness that a person in a coma may experience. Doctors use the Glasgow Coma Scale to assess a patient’s level of consciousness. This is commonly used in emergency medicine. This considers if the patient can open their eyes, move, speak and respond, giving doctors an idea if a patient is in a coma from traumatic brain injury or some other cause. This can indicate if the patient is in a coma already.

Healthcare specialists typically monitor the patient in a medically-induced coma by running a series of simple tests that assess their level of responsivity, including their ability to speak, gesticulate, and exhibit involuntary reflexes, such as automatic reflexes and pupil dilation^[2]. It is usual for a person in a coma to lose their cognitive abilities yet to retain normal sleep patterns and brain activity pertaining to vital functions required for their survival, such as maintaining their heartbeat.^[3]

Medically Induced Coma vs. Sedation, Anesthesia, the Vegetative State, and Brain Death

A coma can seem very similar to being heavily sedated, in a vegetative state, or to brain death. The differences are discussed briefly below^[4]:

• Sedation. Medically induced comas can be difficult to distinguish from sedation, particularly as sedatives are often used to achieve them.Medically induced comas may be viewed as the ultimate form of sedation, resulting in complete and prolonged unconsciousness. Normal forms of sedation typically attempt to lower arousal in a patient and calm down the nervous system, which may be considered a mild or partial suppression of specific aspects of consciousness. Patients are most often semi-conscious rather than unconscious when they are sedated. Patients that are heavily sedated may experience confusion or be unable to respond normally due to feeling either extremely drowsy or disconnected.
• Anesthesia. Anesthesia may be viewed as a temporary, medically induced coma that is achieved through a lower dose of similar medications with the intention of preventing body trauma and pain due to surgical procedures^[5]. While the two states are very similar, experts often point out that anesthesia and a drug-induced coma are distinct states of unconsciousness that result in different patterns of brain activity, with a medically induced coma being considered a more intensive state than general anesthesia. Patients in a medically induced coma may dream and remember certain sensations after resuming consciousness, such as hunger or thirst felt during the comatose state. Anesthesia generally causes complete amnesia. However, some studies have shown that faulty administration may not fully suppress consciousness, resulting in unexpected sensations of pain^[6].
• The Vegetative State may look similar to a coma, yet the patient suffers from a depressed sense of consciousness as opposed to complete unconsciousness^[7]. While they are unable to move, they are still able to respond to a variety of stimuli, such as pain or sound.
• Brain Death refers to a state where the brain stops working entirely, rendering the person unconscious and unable to survive without life support^[8]. Specific criteria are used by physicians to establish brain death.

Use Cases for Induced Coma and Potential Benefits

Why Is A Person Put In A Medically Induced Coma? A medically induced coma is often only used as a last, life-saving resort in the emergency ward of the hospital. A coma is medically induced to protect brain function in cases of traumatic injury. While traumatic brain injury is the most common ground for inducing a medically induced coma, its use can extend to other kinds of injuries that can lead to brain damage. A patient is also often placed in a medically induced coma when they are needing to be on a ventilator to assist breathing. Secondary justifications may include pain relief, end-of-life support, and other similar applications pertaining to palliative care.^[9]

Medically Induced Coma After Heart Attack. After a heart attack or cardiac arrest, a patient is either in a natural coma or sedated and placed in a medically induced coma. As anesthetics are associated with an increased risk for post-surgical heart attacks and cardiac complications^{[10] [11]}, an induced coma after a heart attack may only be a partially good strategy for preventing potential brain damage. Mild hypothermia has been shown to lower the risk of brain injury and increase survival rates in patients in a coma after a heart attack in which resuscitation was successful^{[12] [13]}.

Medically Induced Coma for Seizures and Status Epilepticus. In Status Epilepticus, a potentially life-threatening condition, a seizure lasts longer than 5 mins.^[14]. It is not unusual for prolonged seizures to occur after traumatic brain injury, cardiac arrest or heart attack. In severe cases of status epilepticus, the doctor may resort to treating a patient with a medically induced coma. In this instance, it can help to reduce seizure duration and promote a quicker resolution of the condition, as indicated by shorter hospital stays and time spent in ICU.^[15]

How A Medically Induced Coma Works

A medically induced coma follows similar principles to a natural coma, as described below:

How a Coma Can Protect The Brain. In an ordinary coma, brain networks involved in generating consciousness are placed under pressure, usually as a result of compromised brain oxygen and increased pressure inside the cranium due to injury, infection, or toxicity. Many patients in a coma due to brain injury have brainstem dysfunction along with nerve cell disruption. Lowered brain oxygen and glucose disrupt brain energy production^[16], causing increased neurologic excitation and firing, a higher seizure risk, inflammation release, and neuronal cell death^[17]. This causes the brain to shut down in order to protect itself from immediate harm, resulting in a coma in which neuronal firing is slower and greatly reduced. Depending on the cause, it may also promote secondary waves of brain injury that can manifest hours to days after the coma begins. Patients in a coma may thus still experience various aspects of conscious arousal and suffer from seizures. The degree to which the coma protects the brain and promotes regeneration often dictates how well the patient is able to recover.

Effectiveness of Medically Induced Coma as a Treatment. The drugs used to induce a medical coma typically work by suppressing the networks used to generate consciousness^[18], allowing the brain to rest and regenerate more efficiently. Their efficacy depends on the patient, their condition, and the sedative used. Animal studies have shown that prolonged general anesthesia can promote new synapse formation during a coma and prevent neuronal loss^[19], shedding light on the additional neuroprotective properties of a medically induced coma. On the other hand, barbiturates may increase the risk for late awakening, brain inflammatory changes, long-term delirium, and poor prognosis^[20].

How a Medically Induced Coma is Sustained. Anesthetics such as isoflurane and propofol, high-strength GABAergic medications^[21], and/or barbiturates are the most common form of medication used to induce a coma. The sedative is continuously administered every couple of hours to keep the patient unconscious in an attempt to minimize brain injury. The patient is usually checked every couple of hours to ensure they are still unconscious and sufficiently medicated to maintain the coma. Top establishments often make use of EEG equipment to monitor the patient’s brain state of arousal, some of which may automatically administer medication as required^[22]. The patient usually requires the respiratory assistance of a ventilator and is often also administered with other medications to stop seizures, lower blood pressure, and keep the heart beating regularly. The moment the sedatives are withdrawn, the brain activity gradually reverts to normal, and the patient slowly wakes up from the artificial coma.

Stages of Anesthesia or Heavy Sedation in a Medically Induced Coma

In anesthesia, states of unresponsiveness are known to progress in four stages^[23]:

1. Pain relief or disorientation. Pain-relieving pills are given that render the patient unconscious after taking effect.
2. Excitement or delirium. Involuntary movements, behaviors, muscle spasms, and reflexes occur during this stage, which ceases when the dosing scales up toward stage 3.
3. Surgical anesthesia. This is the optimal dose required for surgery and is reached when the muscles relax, and involuntary reflexes such as pupil dilation cease to function. The patient can be considered in a coma at this stage.
4. Overdose. When too much anesthetic is administered, vital functions such as breathing stop. Mechanical ventilation and other medications to regulate cardiovascular function and blood pressure become necessary at this point.

Unlike a conventional surgical scenario, the patient usually requires a medically induced coma when they are already in a state of physical trauma. This tends to render stages 1 and 2 irrelevant, as the patient may already be unconscious or suffering from disorientation, overstimulation of the nervous system, seizures, and/or involuntary spasms, reflexes, and movements. The third stage and especially the fourth stage can be used to induce an artificial coma that might help to protect the brain under such conditions.

Coming Out of a Medically Induced Coma: The 3 Stages

Unlike general anesthesia, coming out of an artificial coma does not generally take between 2 and 24 hours as the patient is often unconscious for several days to months and becomes physically dependent on sedatives.

Drug Withdrawal and Early Responses. The physician will slowly wean the patient off the sedatives. They may only begin to regain consciousness a few days after administration completely ceases, depending on the duration of the coma. The first signs of consciousness tend to be basic responses of the patient, in which they respond to simple cues such as light or sound and may be able to follow simple commands, such as blinking when asked or moving a limb. The responses tend to be slow and inconsistent, becoming more certain with time.

Confusion, Agitation, and Delirium. After some time, the patient may progress to the next stage in which they may feel agitated and/or confused, a state indicative of temporary delirium. They tend to be uncertain of who they are, where they are, or how they got there. They may need to be restrained due to acting out, yelling, or striking out until more of the sedative effects wear off. ^[24]

Re-emergence and Recovery. Eventually, they reach the final stages, where they are more conscious, respond without difficulty, and are not delirious, yet they may still suffer from neurologic symptoms. Problem-solving, judgment, decision-making, and physical safety may be impaired. Depending on the duration of the coma and the condition of the patient, they may remain in one stage or recover fully without any complications. If recovery is possible, it is not certain how long the process will take.

Safety Profile: Complication Risks, Side Effects, and Contraindications

Medically induced comas can be a safe and effective way to save a person’s life, protect the brain from further damage, or provide pain relief when in a critical condition. Due to the effects long-term sedation can have on the brain, an induced coma is not without side effects.

Side Effects of being in a coma are usually temporary and treated during the recovery phase. These can include physical weakness, disorientation, amnesia, difficulties either sleeping or staying awake, and issues pertaining to various aspects of cognition, such as comprehension and speech. Withdrawal from the sedative medications used to induce coma is one of the most common side effects. Patients may experience withdrawal effects as a result of abruptly needing to stop any medications they were taking before the coma as well. They may additionally require treatment for respiratory infections or UTIs.

Complication Risks. Long-term side effects of medically induced coma may resolve with appropriate treatment and prevention strategies or may be lifelong. The most prevalent ones are as follows:

• Delirium. Some patients that have taken high doses of coma-inducing sedatives go on to acquire delirium and similar states of altered cognition^[25]. Studies reveal that this is likely a result of individual reactions to these drugs, pertaining to the inflammatory and neurologic profile of the patient in question. One study revealed that delirium might only occur in patients in whom interleukin 6 is too high, which is a specific type of inflammatory compound associated with delirium and chronic disease.
• Severe Withdrawal. Severe withdrawal effects from sedatives or other medications, including antidepressants, antipsychotics, or pre-prescribed sedatives, are likely to compound the side effects associated with a medically induced coma. The patient may experience cognitive difficulties long after recovery and require assistance when resuming their prior medical prescriptions.
• Seizures. Occasionally, seizures may develop when coming out of a coma. This is more of a concern for a patient that was placed in a coma in order to treat severe epilepsy. Sometimes seizures of an epileptic patient are not successfully treated by a medically induced coma, with the seizures resuming after sedation stops. In some, this can worsen the intensity of seizures.
• Overdose-Related Syndromes and Toxicities. Being administered certain types of anesthetic drugs via IV drip can cause systemic toxicities that are eventually fatal. Propofol-related infusion syndrome is one example.^[26] The physician will decide which anesthetic is the most appropriate one indicated for treatment that lowers the risk of such complications.

Contraindications. As medically induced comas are often used to save someone’s life in an emergency, they are often not deemed contraindicated in any circumstance that warrants their appropriate use. However, they may be contraindicated in a patient that is allergic or highly reactive to the sedative agent, in which treatment may serve to hinder their condition or increase the risk of mortality.

Recovery Prognosis and Survival Rate

What is the Survival Rate of a Medically Induced Coma? The chances of coming out of medically induced comas are quite high compared to natural comas, as they are reversible. They usually only last for 1-2 days. The prognosis worsens substantially after 4-6 days, yet some patients are still able to recover even after 6 months.

Induced Coma Prognosis. Recovery from a coma depends on the areas of the brain that are affected and how well the brain manages to prevent secondary injury as a result of prolonged faulty brain energy metabolism. This can sometimes be assessed through EEG testing.^[27] Patients that take longer to achieve stability tend to have a much poorer prognosis. If the coma lasts for weeks to months, the patient may suffer from lifelong disability, be in a permanent vegetative state or pass away. Risk factors for longer coma durations include older age, kidney insufficiency, and systemic shock. The types of medications administered and whether cooling was also used or not can also affect the outcome. The best prognosis has been seen in using hypothermia and when treating status epilepticus with a drug-induced coma.^[28]

Optimizing Medically Induced Coma Recovery. Medical experts are trained to monitor the patient throughout the entire process to minimize the risk of complications. Keeping the patient at a cooler temperature is known to minimize potential brain damage and maximize recovery. During recovery from a medical coma, placing personal objects around the patient as well as encouraging social visits and support from family and friends, can help to reduce disorientation in susceptible patients. Depending on the length of the coma, rehabilitation may include the need for physiotherapy and/or an adequate exercise routine. It is advisable for the patient to engage in maintaining strict sleep hygiene, which demands setting a bedtime, lowering activity before bed, and getting light during the daytime. If the brain gets damaged, the patient may need to relearn basic life skills, demanding occupational therapy. Ubiquinol and B vitamins help improve nerve function and, thus, may greatly improve recovery outcomes.

Conclusion

A medically induced coma renders a person reversibly unconscious on anesthetic sedatives in an attempt to minimize damage, trauma, and pain. It is mostly used as a last resort in ICU and emergency wards to treat patients with traumatic brain injury, prolonged seizures, or after cardiac arrest. When in a coma, the brain uses less energy more efficiently and stands a better chance of recovering from oxygen loss and injury. The prognosis tends to vary from patient to patient, depending on the cause of the injury and the degree of stabilization required.

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