During severe illness, sepsis can cause brain dysfunction, confusion and changes in awareness. For some people, cognitive problems such as difficulties with memory, concentration and thinking can continue after the immediate infection has been treated.

In more serious cases, sepsis may contribute to lasting brain injury or cognitive impairment. The risk can vary depending on factors such as the severity of the sepsis, whether septic shock or organ failure developed, the person’s health before becoming unwell, and how long they required critical care.

For people affected by sepsis, it is understandable to be concerned about whether these cognitive problems will improve or have a longer-term impact. Memory or concentration difficulties do not necessarily mean that permanent brain damage has occurred, and recovery can vary considerably from person to person.

This guide explains how sepsis can affect the brain, the main risk factors for longer-term cognitive problems, the possible short- and long-term symptoms, and how these difficulties can affect recovery and daily life. It also explains when delayed diagnosis or treatment may raise concerns about medical negligence.

How can sepsis affect the brain?

Sepsis is a life-threatening condition that develops when the body's response to an infection damages its own tissues and organs. Although sepsis may begin with an infection in another part of the body, its effects can extend to the brain and central nervous system.

One recognised complication is sepsis-associated encephalopathy. This describes changes in brain function caused by sepsis without a direct infection of the brain itself. Symptoms can range from mild confusion or delirium to a significant reduction in consciousness.

Research involving King's College London on sepsis-associated encephalopathy describes several processes that may contribute to this brain dysfunction. These include inflammation, reduced blood flow and disruption to the blood-brain barrier, which normally helps protect the brain from substances circulating in the blood. Neuroinflammation and glial activation can also develop as part of the immune response within the brain during sepsis, contributing to changes in normal brain function.

The risk of brain injury may be greater where someone develops septic shock, organ failure or another serious complication of critical illness. Septic shock can cause dangerously low blood pressure, which may reduce the supply of oxygenated blood to the brain and other vital organs.

However, the neurological effects of sepsis are complex. A person can develop cognitive impairment without a single identifiable area of structural brain damage.

What are the symptoms of sepsis affecting the brain?

Changes in mental state can be an important warning sign during sepsis. The symptoms depend on how seriously the brain and body are affected.

During acute sepsis, possible signs of brain dysfunction include:

• New confusion or disorientation.
• Difficulty staying alert.
• Unusual drowsiness.
• Changes in behaviour.
• Difficulty communicating clearly.
• Delirium.
• Reduced consciousness in severe cases.

NICE guidance on assessing suspected sepsis includes a new altered mental state among the signs clinicians should consider when evaluating risk.

Problems can also continue after the acute illness has passed. Symptoms of brain damage caused by sepsis and other cognitive problems reported during recovery can include:

• Short-term memory problems.
• Difficulty concentrating.
• Slower thinking or processing information.
• Difficulty finding the right words.
• Problems following conversations or instructions.
• Difficulty completing tasks that previously felt straightforward.

These symptoms do not all have the same cause. Some may improve as the person recovers from critical illness, while others can form part of a longer-term cognitive impairment.

Can brain damage from sepsis be permanent?

Brain damage and cognitive problems after sepsis are not always permanent. Some people recover fully, while others experience symptoms for months or longer.

The NHS recognises memory loss and difficulty concentrating among the possible longer-term effects of sepsis. These can form part of post-sepsis syndrome, which affects people differently and can last between six and 18 months in some cases. Other people may take longer to recover.

It is therefore useful to distinguish between:

• Temporary brain dysfunction during the acute illness.
• Cognitive problems that continue during recovery.
• Lasting brain injury or neurological impairment.

Someone who experienced delirium in an intensive care unit may not necessarily have permanent brain damage. Equally, cognitive problems should not be dismissed simply because scans do not show an obvious structural injury.

Sepsis-associated encephalopathy has been linked with longer-term cognitive impairment and functional disability, particularly following severe critical illness.

Anyone concerned about continuing memory, concentration or neurological problems after sepsis should discuss these symptoms with their GP or the healthcare team responsible for their follow-up care.

What is post-sepsis syndrome and how can it affect thinking?

Post-sepsis syndrome is a term used for physical, cognitive and psychological problems that continue after the infection and acute sepsis have been treated.

Cognitive symptoms can include poor concentration, memory problems and what is sometimes described as “brain fog”. NHS information about sepsis and post-sepsis syndrome also recognises depression, anxiety, sleep problems and post-traumatic stress disorder among the possible longer-term effects.

These problems can overlap. Poor sleep and severe fatigue can, for example, make concentration more difficult. A person may also experience both cognitive impairment and a separate psychological injury following a frightening period of critical illness or intensive care.

Recovery is individual. Some people's cognitive function improves significantly over time, while others continue to experience problems that affect their independence and quality of life.

How can cognitive problems after sepsis affect daily life?

The effects of cognitive impairment after sepsis can extend beyond memory tests or medical appointments. They may change how someone manages everyday tasks.

A person recovering from sepsis may find it harder to:

• Concentrate for long periods.
• Follow complex conversations.
• Remember appointments or instructions.
• Read or process written information.
• Organise everyday tasks.
• Return to their previous work responsibilities.
• Manage several tasks at the same time.

These changes can be particularly difficult for someone who was previously independent and had no significant cognitive problems.

Other effects of post-sepsis syndrome, such as fatigue, muscle weakness, sleep difficulties or psychological injury, may add to these challenges. NHS guidance on recovery following sepsis provides further information about the possible longer-term effects.

The level of support a person needs will depend on the nature and severity of their symptoms.

How is brain dysfunction recognised during sepsis?

There is no single test that confirms sepsis-related brain dysfunction.

Doctors assess the person's overall clinical condition. This can include changes in mental state, heart rate, blood pressure, breathing and other vital signs, as well as evidence of infection and organ dysfunction.

Depending on the circumstances, investigations may include blood tests, blood cultures and tests of kidney, liver and other organ function. Doctors may also need to rule out other causes of confusion or reduced consciousness.

People with severe sepsis, septic shock or organ failure may require treatment in critical care or intensive care, where their neurological state and organ function can be monitored closely.

Sepsis-associated encephalopathy can range from delirium to coma. This is why a change in mental state during sepsis needs appropriate clinical assessment rather than being assumed to be a normal consequence of feeling unwell.

Why do early diagnosis and treatment matter?

Early diagnosis and prompt treatment are important because sepsis can develop within hours after infection and can progress to serious organ dysfunction, septic shock and death.

NHS England explains that sepsis can be difficult to diagnose because symptoms can overlap with other conditions and there is no single diagnostic test. Early recognition and prompt treatment are important for improving outcomes.

Depending on the person's condition, treatment may include antibiotics for a suspected bacterial infection, intravenous fluids, oxygen and other supportive treatment. People who become critically unwell may require organ support in intensive care.

NICE guidance on managing suspected sepsis sets out how healthcare teams should assess and treat people according to their level of risk.

Prompt treatment cannot guarantee that someone will avoid brain injury or other complications. However, a delayed diagnosis can allow sepsis and organ dysfunction to progress.

For this reason, doctors and nurses need to recognise warning signs, monitor deterioration and respond appropriately when a patient's condition changes.

When can sepsis-related brain injury raise concerns about medical negligence?

Experiencing brain injury or cognitive impairment after sepsis does not automatically mean that medical negligence occurred. We need to investigate the individual circumstances and the care provided.

Questions about medical negligence may arise where a doctor or nurse:

• Failed to recognise symptoms or warning signs of sepsis.
• Failed to respond appropriately to new confusion or altered consciousness.
• Failed to monitor a person's condition and deterioration.
• Delayed appropriate blood tests or other investigations.
• Unreasonably delayed antibiotics or other necessary treatment.
• Failed to escalate care when the person's condition worsened.
• Failed to respond appropriately to septic shock or organ failure.

For a medical negligence claim to succeed, evidence must show that the care fell below a reasonable standard and that this caused or contributed to avoidable harm. Where lasting cognitive impairment is involved, this may mean investigating whether earlier diagnosis and treatment would probably have reduced the severity of the brain injury or other long-term effects.

If we recommend investigating a case, we gather your medical records and review the timeline of your symptoms, diagnosis and treatment. We then instruct appropriate independent medical experts to consider the standard of care and whether any failings caused or contributed to your injuries.

You can read more about sepsis medical negligence claims, how the medical negligence claims process works and how medical negligence is proven.