Sepsis Six: Understanding What Happens When a Patient Deteriorates

You are looking after a patient being treated for a chest infection. Earlier they were talking normally and their observations were fairly stable. A few hours later they seem muddled. Their respiratory rate has climbed, their blood pressure is falling and they have passed very little urine.

No single one of those findings proves that the patient has sepsis. Put together, though, they tell you that something has changed. This is where sepsis care really begins: not with memorising six interventions, but with recognising that a person with an infection may be developing organ dysfunction and needs urgent reassessment.

The Sepsis Six is still widely used across UK hospitals as a practical way of organising early treatment, but current sepsis care is more nuanced than simply completing the same six actions for everybody with a possible infection. Assessment, National Early Warning Score 2 (NEWS2), clinical judgement, investigation and response to treatment all influence how quickly different interventions are needed.

What is happening when infection becomes sepsis?

With an ordinary infection, the immune response is trying to contain and remove the invading organism. In sepsis, that response becomes dysregulated. Inflammatory signalling affects far more than the original site of infection. Blood vessels dilate, the lining of the circulation becomes more permeable and fluid can move out of the vascular space into the tissues. The circulation may therefore have less effective volume to work with at the same time as vascular resistance is falling.

Now go back to the patient whose blood pressure is dropping. Their heart may initially compensate by beating faster, but maintaining blood flow becomes increasingly difficult. If tissue perfusion is impaired, organs begin to show the consequences. The kidneys may produce less urine. The brain may show this as new confusion. The skin can become cool, mottled or poorly perfused. Respiratory rate often rises early, sometimes before the blood pressure has fallen substantially.

Sepsis is therefore more than an infection that has become particularly severe. It is life-threatening organ dysfunction caused by a dysregulated response to infection. That is why a patient can deteriorate quickly and why changes in observations, cognition, urine output and overall appearance deserve attention together rather than in isolation.

Recognising the patient who is becoming more unwell

There is no single set of observations that diagnoses sepsis. Fever may be present, but a patient can be septic with a normal or low temperature. Tachycardia is common but not specific. A raised lactate can increase concern but is not a sepsis test. The useful question at the bedside is often simpler: what has changed in this patient, and could infection be driving the deterioration?

For adults aged 16 and over who are not pregnant or recently pregnant in an acute hospital setting, current NICE guidance uses NEWS2 alongside clinical assessment to estimate the risk of severe illness or death from sepsis. A NEWS2 of 7 or more places a patient in the high-risk pathway. A score of 5 or 6 may also be treated as high risk when a single parameter contributes 3 points or there is another cause for clinical concern. Lower scores do not make deterioration safe to ignore. A single markedly abnormal parameter, worsening clinical picture or failure to improve can change the level of concern.

That is a useful way to think about NEWS2 on placement. The number helps structure recognition and escalation, but you still have to look at the patient. Someone who is newly confused, visibly mottled or becoming exhausted deserves attention even while the observations are being repeated.

Where the Sepsis Six fits

The UK Sepsis Trust developed the Sepsis Six to bring together six early actions used in the recognition and treatment of sepsis. If somebody asks you what the Sepsis Six are, these are the six actions they mean:

1. Give oxygen if required.
2. Take blood cultures.
3. Give intravenous antibiotics.
4. Give intravenous fluids if indicated.
5. Measure lactate.
6. Monitor urine output.

Knowing the six is useful, but they are not six automatic interventions that every patient with a possible infection receives in exactly the same way. They sit inside the wider assessment of the patient, and current NICE pathways use the person's clinical condition and risk of severe illness or death to determine how urgently particular interventions are needed.

Current NICE guidance deliberately links the urgency of treatment to risk. In the high-risk acute-hospital pathway, blood tests including lactate and blood cultures are obtained, the source of infection is investigated and intravenous antibiotics should be given within one hour of the first NEWS2 score in the emergency department or ward if they have not already been given. Intravenous fluid is also given within one hour unless contraindicated. Senior review and repeated reassessment happen alongside these interventions.

For a patient at moderate risk, there may be time for a clinician with the appropriate competencies to gather more information and clarify whether infection is actually the likely cause. NICE allows broad-spectrum antibiotics to be deferred for up to three hours in this group while that assessment takes place. If there is evidence of hypoperfusion, such as a lactate above 2 mmol/L or acute kidney injury, the patient moves into the high-risk pathway. For low-risk patients, antibiotics may be deferred for up to six hours while the diagnosis is clarified.

This does not make antibiotics less urgent for the patient who is seriously unwell. It stops “possible sepsis” from becoming an automatic instruction to give broad-spectrum antibiotics to everybody before the clinical picture has been assessed.

Why cultures, antibiotics and lactate often happen together

When blood cultures are indicated, the aim is to obtain them before antibiotics if this can be done without delaying urgent treatment. A positive culture may identify the organism in the bloodstream and later help the team narrow antimicrobial therapy. Other samples depend on the suspected source, so urine, sputum, wound samples or other microbiology may be needed as well.

Antibiotics then address the infection driving the response. The choice is not simply “give a sepsis antibiotic”. Prescribers consider the likely source, local antimicrobial guidance, allergies, previous microbiology and the patient's individual circumstances. Once more information becomes available, treatment can be reviewed and narrowed where appropriate.

Lactate adds information about how unwell the patient may be. In sepsis it can rise when the circulation and cellular metabolism are under stress, but a raised lactate is not specific to sepsis and does not simply mean that the tissues have “run out of oxygen”. Seizures, medicines, liver dysfunction and other physiological stresses can also raise it. This is why the result belongs beside the patient rather than being interpreted on its own.

A lactate above 2 mmol/L increases concern in the current NICE pathway. The trend can be useful too. If lactate remains elevated while the patient's blood pressure, mental state or urine output is failing to improve, the team needs to reassess what is happening rather than assuming that treatment has worked because it has been given.

Why fluids need reassessment, not just administration

Think again about the vascular changes in sepsis. Vasodilation and increased vascular permeability can reduce effective circulating volume, so a patient may need intravenous fluid to support perfusion. But that does not mean litres of fluid should automatically be run through every patient with suspected sepsis.

Current NICE guidance recommends an initial 250 mL crystalloid bolus, ideally over 10 to 15 minutes, with reassessment after each bolus. Further 250 mL boluses can be given when required, up to 1,000 mL in total before senior advice is sought if improvement is inadequate. Balanced crystalloids are preferred when available, with 0.9% sodium chloride used if they are not.

The reassessment is as important as the fluid. Has the blood pressure improved? Is capillary refill changing? What is happening to the respiratory rate, oxygen requirement, mental state and urine output? A patient with heart failure or impaired kidney function may tolerate additional fluid poorly, and new breathlessness, falling oxygen saturations or signs of pulmonary oedema need prompt review.

Oxygen is used for hypoxaemia, not simply because the patient has sepsis

A patient with sepsis may need supplemental oxygen, particularly if respiratory illness or circulatory compromise has affected oxygenation. But oxygen is not automatically beneficial when the saturation is already within the patient's target range.

For adults who require oxygen, NICE advises a target oxygen saturation of 94–98%, or 88–92% for people at risk of hypercapnic respiratory failure. A new oxygen requirement is also useful clinical information. If someone who was maintaining their saturation on room air now needs supplemental oxygen, that change belongs in your escalation.

The kidneys can tell you something about the circulation

Reduced urine output is easy to overlook when the more visible problems are happening at the bedside, but the kidneys depend on adequate perfusion. As effective circulating volume and renal blood flow fall, urine production may fall with them. Acute kidney injury can develop as part of sepsis-associated organ dysfunction.

This is why urine output appears in the Sepsis Six. Monitoring may be possible through accurate fluid-balance recording, while some patients will need catheterisation when clinically indicated. A catheter should not be inserted simply because the word sepsis appears in the notes.

For the student nurse, the useful observation is the change. If a patient who had been passing urine normally has produced very little over several hours, combine that information with the rest of the assessment and report it. The pattern tells you more than an isolated number.

Your role when the patient begins to deteriorate

You are not expected to diagnose sepsis independently or decide which antibiotics and fluids should be prescribed. You are expected to notice deterioration and communicate it.

If you repeat observations because the patient looks different and discover that their respiratory rate has risen, their blood pressure has fallen and their NEWS2 has increased, those findings need to reach the registered nurse and appropriate clinical team promptly. If the patient is newly confused, requiring oxygen or producing very little urine, say that too. An ABCDE assessment helps organise what is happening while urgent help is being sought.

As treatment begins, nursing assessment continues. Note when prescribed antibiotics and fluids are given, monitor observations at the frequency required by the pathway, watch the response to treatment and escalate again if the patient continues to worsen. Current NICE guidance requires very frequent NEWS2 reassessment in higher-risk patients, so the first escalation is not the end of the process.

The Sepsis Six gives you six actions to recognise. The deeper skill is seeing why those actions are being used for this patient, at this point in their deterioration. Cultures help identify infection. Antibiotics treat it. Lactate contributes to assessment of severity and perfusion. Fluids may support a compromised circulation. Oxygen treats hypoxaemia when present. Urine output gives you another window into organ perfusion and function.

Once those connections make sense, sepsis stops being a list of six things to remember and becomes a patient whose physiology is changing in front of you.

References and further reading

National Institute for Health and Care Excellence. Suspected sepsis in people aged 16 or over: recognition, assessment and early management (NG253).

National Institute for Health and Care Excellence. Suspected sepsis: managing and evaluating risk in all settings.

Resuscitation Council UK. The ABCDE approach.

UK Sepsis Trust. Clinical tools.

Educational note: This article focuses on people aged 16 and over who are not pregnant or recently pregnant in acute hospital settings. NICE provides separate pathways for children and young people and for pregnancy and the postnatal period. Sepsis pathways, antimicrobial guidance and escalation procedures vary locally, so always follow the policy used in your placement area and work within your level of competence.