What are the neuroprognostic indicators after cardiac arrest (cardiopulmonary arrest)?

From the Guidelines

Neuroprognostication after cardiac arrest should be delayed until at least 72 hours post-arrest and after rewarming if therapeutic hypothermia was used, using a multimodal approach that combines clinical examination, electrophysiological studies, neuroimaging, and biomarkers. This approach is based on the most recent and highest quality study available, which suggests that no single test has sufficient specificity to eliminate false positives 1.

Clinical Examination

For clinical examination, the following factors can be used to predict neurological outcome:

• Absence of pupillary light reflexes (PLR) at 72 hours or later, which can be assessed using quantitative pupillometry 1
• Bilateral absence of corneal reflex at 72 hours or later 1
• Presence of myoclonus or status myoclonus within 7 days after ROSC, in combination with other tests 1
• Motor response, with absent motor response or extensor posturing indicating poor prognosis

Electrophysiological Studies

Electroencephalography (EEG) can be used to predict neurological outcome, with the following patterns associated with poor outcomes:

• Burst suppression or status epilepticus 1
• Bilateral absence of N20 responses on somatosensory evoked potentials (SSEPs) 1

Neuroimaging

Neuroimaging with brain CT or MRI can be used to predict neurological outcome, with the following findings associated with poor outcomes:

• Diffuse anoxic injury 1
• Gray matter-to-white matter ratio (GWR) on brain CT 1
• Apparent diffusion coefficient (ADC) on brain MRI 1

Biomarkers

Biomarkers such as neuron-specific enolase (NSE) can be used to predict neurological outcome, with high serum values at 48-72 hours after cardiac arrest associated with poor outcomes 1. However, NSE should not be used alone to predict poor neurologic outcome due to the possibility of high false positive rates 1.

Multimodal Approach

A multimodal approach that combines these different factors is recommended, as no single predictor is completely reliable 1. Family discussions should acknowledge the limitations of prognostication and the possibility of delayed neurological recovery in some patients. This approach balances the need to identify patients with no reasonable chance of meaningful recovery against avoiding premature withdrawal of life-sustaining therapy in those who might recover.

From the Research

Post Cardiac Arrest Neuroprognostication

• The process of neuroprognostication after cardiac arrest involves various factors, including the use of targeted temperature management (TTM) and sedation protocols 2, 3, 4, 5, 6.
• Targeted temperature management is recommended for adults with out-of-hospital cardiac arrest with an initial shockable rhythm at a constant temperature between 32 °C and 36 °C for at least 24 hours 2.
• Sedation and analgesia are recommended during TTM, but there is significant variation in choice of drug, dosing, and titration between centers 3.
• The use of propofol and remifentanil for sedation during TTM has been associated with earlier awakening and more ventilator-free days compared to midazolam and fentanyl 4, 5.
• Hypothermia can affect the disposition of sedative drugs, including morphine, midazolam, fentanyl, and propofol, and may require adjustments to infusion rates 6.
• The ideal timing and duration of TTM, as well as the optimal sedation protocol, are still topics of ongoing research and debate 2, 3, 4, 5, 6.

Sedation Protocols

• Propofol and remifentanil have been shown to be effective sedation agents during TTM, with benefits including earlier awakening and more ventilator-free days 4, 5.
• Midazolam and fentanyl are also commonly used for sedation during TTM, but may be associated with delayed awakening and fewer ventilator-free days 4, 5.
• The choice of sedation agent and dosing protocol should be individualized based on patient factors and clinical goals 3, 4, 5, 6.

Targeted Temperature Management

• TTM is a critical component of post-cardiac arrest care, with benefits including improved survival and neurological outcomes 2.
• The optimal temperature range for TTM is between 32 °C and 36 °C, with a duration of at least 24 hours 2.
• TTM should be initiated as soon as possible after cardiac arrest, and should be continued for at least 24 hours 2.