A blood biomarker yet to be used in cardiac arrest care can give a clearer picture of the extent of brain damage after a cardiac arrest. This has been shown in a large international multicentre study led by researchers at Lund University that has been published in The Lancet Respiratory Medicine. Worldwide, around four million people each year suffer a sudden cardiac arrest.
"This will transform care for these patients," says researcher Marion Moseby Knappe.
A simple blood test that can very accurately predict the chance of survival with good recovery will be of great significance for patients in intensive care after a cardiac arrest.
This assertion comes from the researchers behind a large multicentre study in which four brain damage biomarkers in the blood were compared to ascertain how reliably they could estimate the extent of brain damage among unconscious patients after cardiac arrest.
"All those admitted to intensive care after cardiac arrest are unconscious and there is always uncertainty about how long this care is to continue. If the blood test shows that the chances are not exhausted it's reasonable to continue intensive care. But if it's clear there are no conditions for survival with a functional status associated with a good life, transition to a palliative phase could be considered," says Niklas Nielsen, professor of anaesthesiology and intensive care at Lund University and consultant in intensive care at Helsingborg Hospital, who led the study.
The results show that the two brain biomarkers routinely used in care for different types of brain damage - neuron-specific enolase and S-100 protein - have significant limitations regarding the prognosis assessment for brain damage after cardiac arrest.
The study confirms previous preliminary results by comparing four biomarkers using an analysis method that can be applied in clinical settings.
"We saw that the biomarker neurofilament light, NFL, correctly identifies 92 per cent of all patient outcomes at six months after the cardiac arrest," says Marion Moseby Knappe, researcher at Lund University and associate consultant in rehabilitation medicine at Skåne University Hospital, one of the researchers behind the study and the first author.
Neurofilament light is already used as a brain biomarker, for example in the care of patients with the neurological disease, MS. Another of the biomarkers in the study - GFAP - was better at estimating the extent of brain damage than those in current clinical use.
"NFL was superior to the other three biomarkers. It's better at differentiating between patients with major and minor brain damage, and can also give an answer as quickly as 24 hours after the cardiac arrest. The biomarker is also more stable in the blood, which is significant in the measurement process," says Marion Moseby Knappe.
Niklas Nielsen points out that the blood test on its own can never be used as a basis for a decision to end intensive care. The decision also requires information from other sources such as X-ray examinations or analysis of electrical activity in the brain.
"Overall, the new findings are significant for a reliable assessment of the chance of waking up after a cardiac arrest," says Niklas Nielsen.
The study, conducted at 24 hospitals in Europe, included 819 adult patients, of whom 661 were men. Blood samples were taken from the participants at 0, 24, 48 and 72 hours after the person was admitted to hospital. All samples were analysed by the same machine.
About the study
The present study was conducted as part of a large international clinical study (Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest (TTM2 trial), published in NEJM 2021) in which patients who suffered cardiac arrest were randomly assigned for treatment with body cooling to 33°C or treatment at normal temperature. This study showed no difference in survival rates or recovery, which led to cooling no longer being recommended in international guidelines.
Cardiac Arrest
Worldwide, around four million people each year suffer a sudden cardiac arrest. In Sweden, the figure for out-of-hospital cardiac arrest is 6,000. Brain cells begin to die a few minutes after a sudden cardiac arrest, and the more time that passes before blood circulation is restored, the greater the risk of permanent brain damage.
Even if the heart is restarted, many patients remain unconscious for hours or days afterwards and physicians then try to determine the severity of the brain damage - and if recovery is possible. The basis for this evaluation includes neurological examinations and brain imaging - and there is a brain damage biomarker that can be measured in blood samples.
