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Induced coma
Induced coma
Induced coma
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Induced coma
Other namesMedically induced coma
SpecialtyNeurology, critical care medicine

An induced coma – also known as a medically induced coma (MIC), barbiturate-induced coma, or drug-induced coma – is a temporary coma (a deep state of unconsciousness) brought on by a controlled dose of an anesthetic drug, often a barbiturate such as pentobarbital or thiopental. Other intravenous anesthetic drugs such as midazolam or propofol may be used.[1][2]

Drug-induced comas are used to protect the brain during major neurosurgery, as a last line of treatment in certain cases of status epilepticus that have not responded to other treatments,[2] and in refractory intracranial hypertension following traumatic brain injury.[1]

Induced coma usually results in significant systemic adverse effects. The patient is likely to completely lose respiratory drive and require mechanical ventilation;[3] gut motility is reduced;[4] hypotension can complicate efforts to maintain cerebral perfusion pressure and often requires the use of vasopressor drugs.[5] Hypokalemia often results.[6] The completely immobile patient is at increased risk of bed sores as well as infection from catheters.[7][8][9]

The presence of an endotracheal tube and mechanical ventilation alone are not indications of continuous sedation and coma. Only certain conditions such as intracranial hypertension, refractory status epilepticus, the inability to oxygenate with movement, et cetera justify the high risks of medically induced comas.[10]

Brain disruption from sedation can lead to an eight times[11] increased risk of the development of ICU delirium. This is associated with a doubled risk of mortality[12] during hospital admission. For every one day of delirium, there is a 10% increased risk of death.[13] Medically induced comas that achieve a RASS level of −4 or −5 are an independent predictor of death.[14]  

Although patients are not sleeping while sedated, they can experience hallucinations and delusions[15] that are often graphic and traumatizing in nature. This can lead to post-ICU PTSD after hospital discharge. Patients that develop ICU delirium are at 120 times greater risk of long-term cognitive impairments.[16]

Considering the high risks of medically induced comas, protocols such as the ABCDEF Bundle[17] and PADIS guidelines[18] have been developed to guide ICU teams to avoid unnecessary sedation and comas. ICU teams that master these protocols to keep patients as awake and mobile as possible are called "Awake and Walking ICUs". These are teams that only implement medically induced comas when the possible benefits of sedation outweigh the high risks during specific cases. 

Survivors of prolonged medically induced comas are at high risk of suffering from post-ICU syndrome[19] and may require extended physical, cognitive, and psychological rehabilitation.

Theory

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Barbiturates reduce the metabolic rate of brain tissue, as well as the cerebral blood flow. With these reductions, the blood vessels in the brain narrow, resulting in a shrunken brain, and hence lower intracranial pressure. The hope is that, with the swelling relieved, the pressure decreases and some or all brain damage may be averted. Several studies have supported this theory by showing reduced mortality when treating refractory intracranial hypertension with a barbiturate coma.[20][21][22]

About 60% of the glucose and oxygen used by the brain is meant for its electrical activity and the rest for all other activities such as metabolism.[23] When barbiturates are given to brain injured patients for induced coma, they act by reducing the electrical activity of the brain, which reduces the metabolic and oxygen demand.[24] Their action limits oxidative damage to lipid membranes and may scavenge free radicals. They also lead to reduced vasogenic edema, fatty acid release and intracellular calcium release.[1]

The infusion dose rate of barbiturates is increased under monitoring by electroencephalography until burst suppression or cortical electrical silence (isoelectric "flatline") is attained.[25] Once there is improvement in the patient's general condition, the barbiturates are withdrawn gradually and the patient regains consciousness.

Controversy exists over the benefits of using barbiturates to control intracranial hypertension. Some studies have found that barbiturate-induced coma can reduce intracranial hypertension but does not necessarily prevent brain damage.[1] Furthermore, the reduction in intracranial hypertension may not be sustained. Some randomized trials have failed to demonstrate any survival or morbidity benefit of induced coma in diverse conditions such as neurosurgical operations, head trauma,[26] intracranial aneurysm rupture, intracranial hemorrhage, ischemic stroke, and status epilepticus. If the patient survives, cognitive impairment may also follow recovery from the coma.[27] Due to these risks, barbiturate-induced coma should be reserved for cases of refractory intracranial pressure elevation.[1]

See also

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References

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Induced coma

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An induced coma, also known as a medically induced coma, is a controlled and reversible state of deep unconsciousness intentionally created by administering high doses of sedative medications, such as propofol or barbiturates like pentobarbital, to reduce brain activity and protect it from further damage in critical conditions. This intervention is typically performed in an intensive care unit (ICU) under close monitoring, where the patient is intubated and placed on mechanical ventilation to support breathing, while continuous electroencephalogram (EEG) tracking ensures the desired "burst suppression" pattern of brain waves, indicating minimized metabolic demand. The primary purpose of an induced coma is to manage severe neurological threats, such as elevated intracranial pressure (ICP) in traumatic brain injury (TBI), where it serves as a last-resort therapy after other measures like osmotic agents or surgical decompression fail, by lowering cerebral metabolism and blood flow to prevent secondary brain damage. It is also employed in cases of refractory status epilepticus to halt uncontrollable seizures, post-cardiac arrest to mitigate hypoxic brain injury from oxygen deprivation, and occasionally in severe strokes or drug overdoses to allow the brain to rest and reduce swelling. The procedure involves gradual titration of sedatives to achieve coma depth, alongside supportive care including vasopressors to maintain blood pressure, intravenous nutrition, and infection prevention, with the goal of weaning the patient off medications once stability is achieved. While effective in stabilizing patients, induced comas carry significant risks, including hypotension requiring pharmacological support, increased susceptibility to infections like ventilator-associated pneumonia, prolonged muscle weakness or atrophy, and potential long-term cognitive impairments such as delirium or memory issues upon emergence. Duration is usually limited to 24–72 hours to minimize complications, though it may extend longer in refractory cases, with outcomes depending on the underlying condition, patient age, and promptness of intervention; recovery involves careful sedation reduction and neurological assessment, often leading to gradual arousal but sometimes with persistent deficits.

Definition and Purpose

Definition

An induced coma, also referred to as a medically induced coma, is a controlled and reversible state of profound unconsciousness deliberately created through the administration of pharmacological agents, such as anesthetics or sedatives, to facilitate therapeutic objectives in critical care settings. This state mimics the deep unresponsiveness of a natural coma but is pharmacologically managed, with patients exhibiting minimal responsiveness. Unlike spontaneous comas resulting from injury or illness, it is intentionally reversible upon cessation of the agents, allowing for gradual emergence as clinical conditions improve. Key characteristics of an induced coma include significant suppression of brain electrical activity, often targeted to achieve a "burst suppression" pattern on electroencephalography (EEG), where periods of high-voltage bursts alternate with flatline suppression. This suppression reduces cerebral metabolic rate of oxygen (CMRO2) by up to 50%, thereby lowering cerebral blood flow and intracranial pressure while minimizing neural tissue stress and oxygen demand. In contrast to general anesthesia, which is short-term (typically hours) for surgical procedures and focuses on immobility and analgesia, an induced coma is prolonged, lasting days to weeks, to provide sustained neuroprotective effects during recovery from severe neurological insults. The terminology "induced coma" encompasses related terms such as "barbiturate coma," which specifically denotes the use of barbiturates like pentobarbital to attain this state, and "therapeutic coma," emphasizing its medical purpose. These synonyms highlight the historical and contextual evolution of the practice, originating from early applications of barbiturates in the mid-20th century for cerebral protection.

Primary Purposes

Induced coma serves as a critical intervention to reduce intracranial pressure (ICP) by diminishing cerebral blood flow and metabolic rate, thereby averting secondary brain injury that could exacerbate initial damage. This physiological reduction in brain activity lowers the volume of blood and oxygen required, stabilizing the intracranial environment and protecting against further tissue swelling or herniation. A core objective is neuroprotection, achieved by curtailing the brain's oxygen demand in at-risk neural tissue. By inducing a state of profound suppression, this approach preserves viable brain regions during periods of vulnerability, supporting potential recovery. Induced coma is also employed to manage refractory seizures or status epilepticus that persist despite standard antiepileptic therapies, interrupting seizure propagation and allowing neural recovery. To ensure adequate depth, therapeutic goals include achieving burst suppression on electroencephalogram (EEG), characterized by alternating periods of high-voltage bursts and suppression (isoelectric intervals), confirming effective coma induction.

Medical Indications

Traumatic Brain Injury

In severe traumatic brain injury (TBI), defined by a Glasgow Coma Scale (GCS) score of ≤8, induced coma serves as a tier 3 intervention according to the Brain Trauma Foundation (BTF) guidelines for managing elevated intracranial pressure (ICP) that is refractory to first- and second-line therapies such as osmotherapy and hyperventilation. This approach is recommended at a Level IIB evidence level, based primarily on Class 2 studies, to suppress cerebral metabolism and thereby control ICP when other measures fail. Induced coma is typically initiated within 24-48 hours post-injury if ICP remains persistently elevated above 20-25 mmHg despite maximal initial treatments. This timing aligns with the stabilization phase following resuscitation, allowing assessment of refractory ICP while minimizing delays that could exacerbate secondary brain injury. Evidence supporting its use includes randomized controlled trials demonstrating ICP control in refractory cases, with one seminal study (Eisenberg et al., 1988) showing that high-dose barbiturates achieved ICP control in 32% of patients compared to 17% in controls (uncontrolled ICP 68% vs. 83%, relative risk 0.82), and improved survival among responders (92% vs. 17%). The Eurotherm3235 trial (2015), which examined therapeutic hypothermia as part of ICP management protocols (often combined with induced coma), confirmed effective ICP reduction but highlighted risks including worse functional outcomes, underscoring the need for cautious application. Patient selection prioritizes those with closed head injuries exhibiting diffuse brain swelling, as this pattern responds better to metabolic suppression without the heightened infection risks associated with penetrating trauma. Induced coma is generally avoided in penetrating injuries due to increased susceptibility to complications like infection in open wounds. These criteria ensure the intervention targets cases where ICP elevation stems from widespread edema rather than focal lesions amenable to surgical evacuation. In severe TBI with refractory intracranial hypertension, a medically induced coma is induced using intravenous anesthetic agents such as barbiturates (e.g., pentobarbital or thiopental), propofol, or midazolam. These drugs are administered via continuous infusion in an ICU setting, with the dose titrated to achieve burst suppression or isoelectric pattern on EEG monitoring. This reduces brain metabolic demand, oxygen consumption, and intracranial pressure to protect the brain from further damage due to swelling. The patient is intubated, mechanically ventilated, and closely monitored for complications like hypotension. The coma is temporary and reversed by gradually reducing the drugs once the condition stabilizes.

Non-Traumatic Conditions

Induced coma is employed in non-traumatic conditions primarily to manage elevated intracranial pressure (ICP), reduce cerebral metabolism, and mitigate secondary brain injury in scenarios such as ischemic stroke and subarachnoid hemorrhage (SAH). In cases of massive ischemic stroke leading to malignant cerebral edema, barbiturate-induced coma may be used rarely as a salvage therapy when standard measures like osmotherapy and hyperventilation fail to control ICP, though it is not routinely recommended due to limited evidence of benefit and potential hemodynamic instability. For aneurysmal SAH, particularly in poor-grade patients with refractory ICP or severe vasospasm, barbiturate coma serves as a last-resort intervention to decrease cerebral metabolic rate and improve outcomes in select refractory cases, despite the challenge of obscuring neurological monitoring. In refractory status epilepticus (RSE), defined as seizures persisting after administration of benzodiazepines and at least one additional anticonvulsant, induced coma with anesthetic agents such as propofol or midazolam is a cornerstone of treatment to achieve burst suppression on EEG and halt seizure activity. This approach acts as a bridge to identify underlying causes or initiate further therapies, with observational studies reporting seizure suppression rates exceeding 80% in RSE patients undergoing pharmacological coma, though recurrence upon weaning occurs in up to 50% of cases. Other applications include hepatic encephalopathy in acute liver failure, where cerebral edema and ICP elevation are prominent; barbiturate coma is reserved for refractory intracranial hypertension unresponsive to mannitol or hypertonic saline, as it reduces metabolic demand and has been associated with improved survival in select cohorts awaiting liver transplantation. In severe encephalitis with significant brain swelling, induced coma may be utilized to limit neurological damage by minimizing brain activity and allowing edema resolution, though evidence is largely anecdotal and supportive care remains primary. Rare use extends to post-cardiac arrest neuroprotection in comatose patients, where historical trials explored barbiturates to attenuate ischemic injury, but current guidelines favor targeted temperature management over pharmacological coma due to superior evidence. The evidence supporting induced coma in these non-traumatic conditions is predominantly observational, with few randomized controlled trials due to ethical challenges and heterogeneity of patient populations; while it demonstrates efficacy in acute seizure control and ICP reduction, long-term neurological outcomes remain variable, underscoring the need for individualized application.

Procedure and Management

Initiation and Sedation

The initiation of an induced coma typically occurs in a specialized intensive care unit (ICU) environment, such as a neurocritical care unit, under the supervision of a multidisciplinary team including a neurologist or neurosurgeon, intensivist, anesthesiologist, and critical care nurses. This setting ensures immediate access to advanced monitoring equipment and rapid response capabilities to manage potential complications during the procedure. Prior to induction, a thorough pre-induction assessment is conducted to optimize patient stability and confirm the appropriateness of the intervention, tailored to the underlying condition. The airway is secured through endotracheal intubation and mechanical ventilation to protect against aspiration and ensure adequate oxygenation, targeting a saturation greater than 95%. Hemodynamic stabilization is achieved by maintaining normovolemia and appropriate cerebral perfusion pressure (typically 60-70 mmHg in cases of elevated intracranial pressure), and mean arterial pressure (often 65-90 mmHg depending on indication), using vasopressors like norepinephrine if needed. Baseline monitoring is established with continuous electroencephalography (EEG) for initial recording, arterial blood pressure via catheter, central venous access, and end-tidal CO2 monitoring; intracranial pressure (ICP) monitoring via an ICP monitor is added when indicated, such as in traumatic brain injury (TBI). The choice of sedative agent and protocol varies by medical indication (see Pharmacology section). For refractory intracranial hypertension in severe TBI after failure of standard therapies like osmotic agents or surgical decompression, high-dose barbiturates such as pentobarbital or thiopental are used per Brain Trauma Foundation guidelines. In select cases, alternative agents such as propofol or midazolam may be considered, particularly to minimize hemodynamic complications. The protocol begins with a bolus loading dose of 10 mg/kg administered intravenously over 30-60 minutes to rapidly achieve deep sedation. This is immediately followed by a continuous infusion, initially at 1-5 mg/kg/hour, titrated based on EEG findings to achieve burst suppression (typically 2-5 bursts per minute) or isoelectric pattern, which indicates profound coma with loss of brainstem reflexes and apnea. Hemodynamic support is closely monitored during loading to counteract barbiturate-induced hypotension. For other indications, such as refractory status epilepticus, propofol or midazolam may be used, with bolus doses (e.g., propofol 1-2 mg/kg) followed by infusion titrated to EEG burst suppression to control seizures. The initial duration of induced coma is planned based on the condition, often as a 24-72 hour trial period to assess efficacy (e.g., in controlling ICP below 20-22 mmHg for TBI), with reassessment by the multidisciplinary team to determine continuation. This approach aligns with evidence from randomized controlled trials supporting barbiturate use in select cases of severe TBI.

Ongoing Monitoring

During an induced coma, continuous and vigilant monitoring is essential to maintain therapeutic goals, detect complications early, and guide adjustments to sedation depth. This involves multimodal assessments tailored to the patient's underlying condition, such as traumatic brain injury, to ensure cerebral protection while minimizing systemic risks. Monitoring protocols emphasize both neurological and physiological parameters, with real-time data informing clinical decisions in intensive care settings. Neurological monitoring forms the cornerstone of oversight, focusing on brain activity and pressure dynamics. Serial electroencephalography (EEG) is routinely employed to achieve and sustain burst suppression patterns, which indicate adequate sedation depth and help prevent subclinical seizures; this involves continuous or frequent recordings to quantify suppression ratios, typically targeting 50-80% suppression for neuroprotection. Intracranial pressure (ICP) is monitored via an intraventricular catheter when indicated, particularly in cases of elevated risk, as it allows direct measurement and therapeutic cerebrospinal fluid drainage to keep ICP below 20-22 mmHg. Pupillary examinations are performed regularly to assess brainstem integrity, evaluating size, symmetry, and light reactivity for signs of herniation or evolving injury. Systemic parameters are tracked continuously to support homeostasis and prevent secondary insults. Vital signs, including heart rate, blood pressure, and temperature, are monitored via invasive lines to maintain cerebral perfusion pressure above 60-70 mmHg in relevant cases. Arterial blood gases and electrolytes are checked frequently—often every 4-6 hours initially—to correct imbalances like hyponatremia or acidosis, which can exacerbate brain swelling. Nutrition is provided through enteral routes when feasible to preserve gut integrity, supplemented by parenteral nutrition if intolerance occurs, aiming for 20-30 kcal/kg/day to avoid catabolism without overfeeding. Sedative agents are titrated based on validated depth scales adapted for coma states, such as the Richmond Agitation-Sedation Scale (RASS) during brief arousals where feasible, targeting scores of -4 to -5 for deep sedation, alongside EEG trends for precise control. Continuous waveform monitoring, including EEG and ICP traces, is standard, with interruptions of sedation for neurologic assessment performed as clinically appropriate (e.g., when hemodynamically stable and ICP controlled) to evaluate responsiveness and adjust therapy. These interruptions facilitate Glasgow Coma Scale scoring and motor testing where possible, balancing the need for accurate prognostication against risks of agitation or ICP spikes.

Pharmacology

Common Agents

Barbiturates, such as pentobarbital and thiopental, serve as first-line agents for inducing coma primarily to control elevated intracranial pressure (ICP) in severe traumatic brain injury (TBI). The typical regimen involves a loading dose of 10-15 mg/kg administered intravenously over 30-60 minutes, followed by a continuous maintenance infusion of 1-4 mg/kg/hour, titrated to achieve burst suppression on electroencephalography (EEG) while monitoring for hemodynamic stability. Propofol is another commonly used agent for induced coma, valued for its rapid onset, shorter half-life allowing easier titration and weaning, and additional antiemetic effects that can benefit patients with nausea from ICP elevation. It is typically administered as a continuous intravenous infusion starting at 1-2 mg/kg/hour after an optional bolus, with doses adjusted based on clinical response and EEG monitoring to maintain deep sedation without excessive accumulation. Other agents include benzodiazepines such as midazolam, which may serve as an alternative in certain contexts (e.g., alongside propofol for some indications), often employed at a maintenance infusion of 0.2 mg/kg/hour specifically for patients at risk of seizures during induced coma, due to its anticonvulsant properties. Ketamine may be considered in select cases where hemodynamic stability is a concern, as it provides analgesia and sedation without significant hypotension, though it is not routinely used as a primary agent for ICP control. Selection of these agents depends on factors, including liver and renal function, as barbiturates like pentobarbital undergo hepatic and may accumulate in hepatic impairment, while propofol is preferred in scenarios requiring quick recovery. is generally avoided to minimize interactions and complications such as or prolonged .

Mechanisms of Action

Sedatives used to induce coma primarily act by enhancing inhibitory neurotransmission through modulation of gamma-aminobutyric acid (GABA) receptors, particularly the GABA-A subtype. Barbiturates, for instance, bind to specific sites on the GABA-A receptor, prolonging the opening of associated chloride ion channels and thereby increasing chloride influx into neurons. This hyperpolarizes neuronal membranes, suppressing action potential firing and overall brain excitability, which facilitates the deep suppression of consciousness required for coma. Similar potentiation occurs with other GABAergic agents like benzodiazepines and propofol, though their effects differ in potency and duration at comatose doses. A key physiological outcome of this enhanced inhibition is a profound reduction in cerebral metabolism. These agents decrease cerebral glucose utilization by approximately 40-50% in normal brain tissue, paralleling a similar drop in the cerebral metabolic rate for oxygen (CMRO2). This metabolic suppression lowers carbon dioxide production, reducing cerebral vasodilation and thereby helping to control intracranial pressure. The uncoupling of cerebral blood flow from metabolism further contributes to neuroprotection by minimizing oxygen demand in vulnerable brain regions. Electroencephalographic (EEG) monitoring reveals characteristic patterns during induced coma, reflecting the depth of neuronal suppression. High doses of these sedatives typically produce burst-suppression or near-isoelectric EEG states, where periods of high-voltage electrical bursts alternate with flatline (isoelectric) intervals. These patterns arise from the dominance of inhibitory GABAergic activity over excitatory neurotransmission, with bursts representing residual synchronized neuronal firing amid widespread silencing. The extent of suppression can be quantified through spectral analysis of EEG signals, which assesses power in frequency bands to titrate sedative dosing and ensure adequate coma depth. In addition to primary inhibitory effects, sedatives exert secondary anticonvulsant actions that reinforce coma induction. At therapeutic concentrations, barbiturates block voltage-gated sodium channels, inhibiting repetitive neuronal firing that could precipitate seizures. They also diminish excitatory glutamate release from presynaptic terminals, further stabilizing neuronal membranes and preventing hyperexcitability. These mechanisms collectively ensure a controlled, protective state of reduced brain activity during critical care.

Risks and Complications

Immediate Risks

Induced coma, typically achieved through high-dose sedation with agents like propofol or barbiturates, frequently leads to hemodynamic instability, primarily manifesting as hypotension due to vasodilation and myocardial depression. This complication arises from the vasodilatory effects of these sedatives, which can reduce systemic vascular resistance and cardiac output, often necessitating the use of vasopressors such as norepinephrine or phenylephrine to maintain cerebral perfusion pressure. Studies in patients with severe traumatic brain injury treated with barbiturate coma report hypotension as a common adverse effect, with incidences ranging from 40% to 50% depending on dosing and patient factors, underscoring the need for continuous arterial pressure monitoring and fluid resuscitation to mitigate risks of secondary brain ischemia. Respiratory suppression is an inherent consequence of induced coma, as deep sedation abolishes the patient's spontaneous breathing drive, mandating mechanical ventilation to ensure adequate oxygenation and ventilation. This reliance on endotracheal intubation and prolonged mechanical support elevates the risk of ventilator-associated pneumonia (VAP), a nosocomial infection characterized by bacterial colonization of the lower respiratory tract. In comatose patients, particularly those with acute brain injury, early-onset VAP occurs in up to 24% of cases within the first week, driven by impaired airway reflexes, gastric reflux, and biofilm formation on ventilatory equipment, potentially prolonging ICU stays and increasing mortality if not addressed through strict infection control protocols. Patients in induced coma exhibit heightened susceptibility to infections owing to sedation-induced immunosuppression, which dampens innate and adaptive immune responses, including reduced cytokine production and leukocyte function. This immunodepression, akin to that observed in traumatic brain injury, facilitates nosocomial infections such as bloodstream infections from central venous catheters, which are routinely placed for hemodynamic monitoring and drug administration. Central line-associated bloodstream infections (CLABSIs) are prevalent in this setting, with rates in ICU patients reaching 1-5 per 1,000 catheter-days, often involving pathogens like Staphylococcus aureus due to breaches in sterile technique and prolonged line dwell times. Metabolic disturbances commonly accompany induced coma, including therapeutic hypothermia to enhance neuroprotection, which can induce electrolyte imbalances such as hypokalemia, hypomagnesemia, and hypophosphatemia through cold diuresis and shifts in cellular ion transport. Barbiturate or propofol infusions exacerbate these issues, leading to azotemia and hepatic dysfunction in susceptible patients. A particularly severe but rare complication is propofol infusion syndrome (PRIS), occurring in 1-3% of critically ill cases but with a fatality rate exceeding 50%, characterized by refractory metabolic acidosis, rhabdomyolysis, hyperkalemia, and cardiac arrhythmias due to mitochondrial toxicity from prolonged high-dose exposure (>4 mg/kg/hour for >48 hours).

Long-Term Effects

Survivors of induced coma often experience persistent cognitive deficits, including impairments in memory, attention, and executive function, affecting 20-40% of cases and associated with the duration of sedation and underlying brain injury. These deficits manifest as difficulties in learning new information, slowed processing speed, and challenges with decision-making, which can persist for months or years post-discharge. Studies in critically ill patients, including those with traumatic brain injury (TBI) requiring induced coma, indicate that prolonged sedation contributes to this vulnerability by altering neurotransmitter activity and cerebral metabolism. Physical sequelae from induced coma primarily arise from extended immobility, leading to significant muscle atrophy that necessitates intensive rehabilitation. Critically ill patients under sedation can lose up to 2% of skeletal muscle mass per day in the first week, with atrophy incidence reaching 60% among those on mechanical ventilation. Additionally, the immobility increases the risk of deep vein thrombosis (DVT), a common complication in comatose individuals due to venous stasis, occurring in up to 20-30% of cases without prophylaxis. Rehabilitation programs focusing on physical therapy are essential to restore strength and mobility, though full recovery may take several months. Psychological impacts, such as post-traumatic stress disorder (PTSD) and residual effects from delirium, affect up to 50% of induced coma survivors based on ICU cohort studies. Delirium upon emergence from coma or in sedated ICU patients, reported in 70-87% of cases, heightens the risk of long-term PTSD symptoms like flashbacks and hypervigilance, with PTSD incidence around 10-30% post-discharge. These effects stem from the disorienting ICU environment and sedative agents disrupting normal sleep-wake cycles, often requiring psychological support for management. Induced coma in conditions like TBI is used in severe, refractory cases where in-hospital mortality rates are 30-50%, alongside long-term neurologic disability in many survivors. Mortality is influenced by factors such as initial injury severity and complications during sedation, while survivors frequently face ongoing disabilities including hemiparesis and aphasia, impacting quality of life. Emerging research as of 2025 highlights advanced neuromonitoring to help mitigate these risks. These outcomes underscore the need for multidisciplinary follow-up to mitigate persistent neurologic burdens.

Recovery Process

Weaning Protocol

The weaning protocol for induced coma involves a systematic, gradual discontinuation of sedative agents to minimize risks of intracranial pressure (ICP) elevation, seizures, or withdrawal symptoms while assessing neurological recovery. This process is typically initiated only after the underlying condition prompting the coma—such as traumatic brain injury or refractory status epilepticus—has stabilized, ensuring safe transition to lighter sedation or wakefulness. Key criteria for starting weaning include sustained ICP control below 20 mmHg for at least 48 hours following a minimum treatment duration, such as 72 hours of burst suppression therapy in barbiturate-induced coma. Additionally, effective seizure control must be confirmed via continuous electroencephalography (EEG), with no ongoing electrographic seizures, and the primary pathology must show evidence of reversibility, such as resolution of cerebral edema on imaging. These thresholds help prevent rebound ICP spikes that could exacerbate brain injury. The tapering method emphasizes slow reduction of sedative infusion rates to avoid abrupt physiological changes. For barbiturates like pentobarbital, a common approach is to decrease the dose by 50% every 12 hours until reaching below 0.5 mg/kg/hour, followed by discontinuation, with similar gradual strategies applied to agents like propofol (e.g., 20-30% daily reductions). Continuous EEG monitoring is essential during this phase to detect rebound burst activity or seizures, allowing immediate resumption of prior dosing if ICP exceeds 20 mmHg within 12 hours of a dose cut. If instability occurs, the infusion is restarted at the previous effective rate for an additional 48 hours before retrying the taper. Challenges during weaning include withdrawal hyperalgesia from prolonged opioid co-administration, manifesting as heightened pain sensitivity, and potential seizures due to rapid sedative withdrawal, both of which can complicate ICP management. These are addressed with adjunct therapies such as clonidine for sympathetic overactivity or low-dose benzodiazepines for agitation, alongside vigilant vital sign monitoring to mitigate hemodynamic instability. A multidisciplinary approach is critical, involving daily neurological examinations by intensivists and neurologists, incorporation of sedation vacations—brief pauses in sedation to evaluate responsiveness—and input from pharmacists for dose adjustments and nurses for real-time ICP tracking. This team-based strategy, often including respiratory therapists for concurrent ventilator weaning, enhances safety and facilitates timely adjustments based on evolving patient status.

Patient Outcomes

Patient outcomes following induced coma vary significantly depending on the underlying condition, duration of coma, and patient-specific factors. Overall survival rates range from 50% to 70%, with higher rates observed in cases of refractory status epilepticus (approximately 68%) compared to traumatic brain injury (TBI), where survival is around 51% for patients presenting with severe impairment. Functional recovery is commonly assessed using the Glasgow Outcome Scale (GOS), which categorizes outcomes from good recovery (GOS 4-5) to death (GOS 1). Among survivors, good recovery rates typically fall between 20% and 40%, while severe disability (GOS 3) affects about 20% to 30% of patients, with lower rates of favorable outcomes in TBI cohorts (13-30%) than in status epilepticus cases (around 24% achieving modified Rankin Scale 0-3, equivalent to good GOS). Key prognostic indicators include pre-coma Glasgow Coma Scale (GCS) score, with higher scores correlating to better survival and recovery; age under 40 years, which is associated with improved outcomes in refractory status epilepticus treated with barbiturate coma; and absence of pupillary abnormalities, where bilateral reactive pupils predict substantially better functional results (up to 25% good outcome) compared to fixed dilated pupils (near 0%). Long-term quality of life among survivors is often compromised, with studies indicating persistent fatigue, cognitive impairments, and dependency on caregivers in a majority of cases, linked to alterations in brain connectivity observed after prolonged induced coma.

History and Research

Historical Development

The use of barbiturates for inducing therapeutic coma originated in the early 20th century, following their introduction as sedative agents in clinical medicine. Barbituric acid was first synthesized in 1864, but clinical applications began around 1903 with barbital (Veronal), which was employed for sedation, hypnosis, and seizure control in epilepsy by the 1910s and gained widespread popularity in the 1930s for managing neurological disorders, including through high-dose administration to achieve deep sedation bordering on coma-like states in psychiatric and epileptic contexts. This early adoption laid the groundwork for later neuroprotective uses, though initial applications focused more on symptom control than systematic coma induction for intracranial pressure (ICP) management. The modern practice of induced coma in neurocritical care emerged in the 1970s, particularly for (TBI), as studies demonstrated ' ability to reduce ICP by suppressing cerebral . A pivotal multicenter study by Marshall et al. in 1979 evaluated aggressive administration in severe patients, showing that high-dose effectively lowered ICP in selected cases, improving outcomes when combined with other interventions like and osmotherapy. This work marked a shift toward coma as a targeted therapy for uncontrolled ICP, influencing its adoption in intensive care units during the 1980s for TBI and other acute brain injuries. By the 1990s, induced coma protocols were formalized within neurocritical care guidelines, reflecting growing evidence from clinical trials. The Brain Trauma Foundation's inaugural Guidelines for the Management of Severe Traumatic Brain Injury, published in 1995, recommended high-dose barbiturates for refractory ICP elevation unresponsive to first-line treatments, based on level II evidence from studies like Marshall's. Subsequent editions in the 2000s and the 4th edition in 2016 refined these recommendations through evidence-based reviews, emphasizing EEG monitoring to achieve burst suppression and cautioning against prophylactic use due to risks like hypotension. A significant milestone came with the 2015 Eurotherm3235 trial, which questioned the broad application of aggressive ICP-lowering strategies, including barbiturate coma. This randomized controlled trial compared therapeutic hypothermia (32–35°C) to normothermia in TBI patients with elevated ICP, finding that while hypothermia reduced ICP, it worsened functional outcomes; barbiturates were reserved for refractory cases in the control arm, prompting guidelines to restrict induced coma to salvage therapy only, rather than routine intervention.

Current Research Directions

Recent research in induced coma emphasizes the integration of advanced neuroimaging techniques, such as functional MRI (fMRI) and positron emission tomography (PET), to tailor the depth and duration of sedation, thereby minimizing overtreatment in patients with traumatic brain injury (TBI) or status epilepticus. Studies have demonstrated that PET imaging can elucidate neural correlates of consciousness in comatose patients. Similarly, hybrid PET/MRI scanners are being explored for preclinical and clinical applications in brain injury management. Investigations into alternative sedative agents aim to mitigate common side effects associated with traditional barbiturates, such as hemodynamic instability and prolonged recovery. Dexmedetomidine, an alpha-2 agonist with neuroprotective properties, is under evaluation in trials, though bradycardia remains a noted risk. For ketamine in TBI-induced coma, phase III trials like the Brain Injury and Ketamine (BIKe) study, ongoing as of 2025, are assessing its role as an adjunct to barbiturates. Efforts to optimize patient outcomes increasingly incorporate biomarkers for predictive modeling, with S100B protein emerging as a key indicator of neurological recovery in induced coma scenarios. Meta-analyses from 2020-2024 highlight S100B's high discriminatory power for functional outcomes at 3-6 months post-TBI, achieving pooled area under the curve (AUC) values of 0.80-0.85 in late serum samples. Ethical considerations in induced coma research have gained prominence, particularly regarding surrogate consent in acute emergencies where patients lack decision-making capacity. Studies emphasize the need for deferred consent models to balance urgency with autonomy, noting challenges in obtaining informed agreement amid sedation and family distress. Analyses also address long-term quality of life (QoL) implications.

References

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