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← Medicine of older adults indexChapter sections
OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Acute illness in frailty

Medicine of older adults · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Acute deterioration with limited physiological reserve

New delirium, collapse, reduced mobility, poor intake, incontinence or drowsiness may be the presenting feature of sepsis, stroke, myocardial infarction, hypoxia, bleeding, fracture, metabolic disease or medicine toxicity in frailty.

Action: Use ABCDE, glucose, NEWS2 and focused examination, treat immediately reversible threats, obtain collateral about the stable baseline and activate diagnosis-specific pathways without waiting for fever, pain or textbook symptoms to appear.

Overview

Recognise acute disease when frailty blunts classic symptoms, separate reversible illness from baseline vulnerability, and provide proportionate emergency treatment, comprehensive geriatric assessment and rehabilitation that prevents avoidable dependency.

Establish what changed and when. Ask the person, family, carers, ambulance and care records about stable cognition, communication, walking, transfers, continence, food and fluid, medication and care needs roughly two weeks before illness. Document the exact departure: stopped walking, new sleepiness, missed meals, new incontinence or altered behaviour. Avoid calling it general decline because that phrase hides tempo and mechanism.

Assess physiology before attributing symptoms to frailty. Use ABCDE, capillary glucose and NEWS2, but interpret trends and treatment modifiers: beta-blockade may blunt tachycardia, immunosuppression may blunt fever and chronic lung disease changes oxygen targets. Examine heart, lungs, abdomen, skin, mouth, hydration, neurology, joints and injuries, including rectal or bladder assessment when symptoms suggest loading or retention.

Screen for delirium with 4AT when acute change is possible and obtain collateral about baseline cognition. Delirium commonly reflects several precipitants: infection, hypoxia, pain, medicine toxicity, withdrawal, dehydration, electrolyte disturbance, constipation, retention, sleep and environment. Treat these in parallel while providing orientation, hearing aids, glasses, familiar contact, movement, food and sleep opportunity.

Aetiology

01

Common acute disease

Infection, vascular events, heart or lung decompensation, bleeding, fracture and metabolic disturbance remain common despite atypical presentation.

02

Medicine and treatment effects

Sedation, anticholinergic load, hypoglycaemia, hypotension, anticoagulation and renally accumulated medicines can precipitate functional collapse during acute physiological stress.

03

Environmental destabilisation

Hospital transfer, sleep disruption, missing sensory aids, fasting and unfamiliar care can trigger delirium and immobility.

04

Support-system failure

A missed carer, inaccessible toilet, unavailable food or incorrect administration can convert limited reserve into crisis.

Pathophysiology

  1. 1
    Reduced homeostatic reserve

    Multisystem impairment narrows the margin for compensating for infection, fluid shifts, pain, medication and environmental stress.

  2. 2
    Atypical inflammatory response

    Older adults may not develop marked fever or tachycardia, while delirium and functional decline reveal systemic illness earlier.

  3. 3
    Threshold functional failure

    A modest physiological insult can push gait, continence, cognition or self-care below the threshold required for independence.

  4. 4
    Immobilisation cascade

    Bed rest rapidly worsens muscle power, orthostatic tolerance, bowel function, pressure risk and confidence during acute treatment.

  5. 5
    Competing organ vulnerability

    Fluids, oxygen, analgesia and medicines beneficial to one condition may worsen heart, kidney, respiratory or cognitive function.

Clinical features and red flags

Atypical acute illness

New confusion, falls, poor intake or inability to walk occurs without a prominent organ-specific complaint.

Delirium phenotype

Attention and arousal fluctuate over hours, with altered cognition or perception from the stable baseline.

Functional sentinel event

A previously independent transfer or toilet task suddenly fails and reveals physiological deterioration.

Medicine destabilisationRed flag

Symptoms follow missed time-critical treatment, new sedation, hypoglycaemia, hypotension or impaired clearance.

Physiological high riskRed flag

Hypoxia, hypotension, reduced urine, mottling or reduced consciousness requires immediate emergency treatment.

Care-system crisis

Medical stability is accompanied by missing meals, administration, transfers or supervision that makes home unsafe.

Red flags requiring action

  • New oxygen requirement, respiratory distress, hypotension, mottling, reduced urine or altered consciousness requires emergency physiological support.
  • Sudden focal deficit, new inability to stand, speech change or persistent ataxia requires acute stroke assessment.
  • Fall with head impact, anticoagulation, focal bony pain or inability to weight bear requires urgent injury imaging.

Investigations

  1. 01
    ABCDE, glucose and NEWS2First step
    Why
    Identify physiological danger before atypical symptoms mislead.
    Interpretation and limitations
    Treat abnormalities immediately and use trends, chronic baselines and drug effects rather than a single reassuring score.
  2. 02
    Collateral baseline reconstruction
    Why
    Define acute change and rehabilitation target.
    Interpretation and limitations
    Record stable cognition, gait, transfers, ADLs, intake, continence, medicines and support from multiple reliable sources.
  3. 03
    4AT delirium assessment
    Why
    Detect acute brain dysfunction promptly.
    Interpretation and limitations
    A positive result supports delirium but not its cause; repeat when fluctuation or sedation changes the examination.
  4. 04
    Targeted laboratory and microbiology tests
    Why
    Find infection, bleeding and metabolic triggers.
    Interpretation and limitations
    Select FBC, renal, electrolytes, glucose, liver, inflammation, cultures or other tests from findings and interpret against trends.
  5. 05
    ECG and symptom-directed imaging
    Why
    Identify cardiac, pulmonary, neurological, abdominal or injury disease.
    Interpretation and limitations

Differential diagnosis

01

Delirium from acute illness

Fluctuating inattention and altered arousal often integrate several triggers and require active cause assessment rather than a dementia label.

02

Dementia or chronic frailty progression

A gradual trajectory differs from an abrupt departure from baseline, which should be treated as illness until explained.

03

Medicine toxicity or withdrawal

Recent initiation, dose change, renal decline or missed dependence-forming treatment can produce acute cognitive and functional symptoms.

04

Social or safeguarding crisis

Loss of care, neglect, food insecurity and unsafe housing can mimic medical decline while creating genuine physiological harm.

05

End-of-life deterioration

Progressive dying may resemble acute illness, but potentially reversible distress and the person's goals still require explicit assessment.

Management

01First-line acute sequenceStabilise and define departure from baselineFirst stepFirst lineFrailty is accompanied by new cognitive, physiological or functional deterioration.+
  1. 1Use ABCDE, glucose, NEWS2 and focused injury, neurological, chest, abdominal, bladder and bowel assessment.
  2. 2Obtain collateral and reconcile medicines while treating time-critical disease and correcting immediate precipitants.
  3. 3Start CGA, delirium prevention and function-preserving care in parallel rather than waiting for diagnostic completion.
02Function-preservation routeTreat immobility as a complicationAcute illness or ward routines reduce transfers, walking or self-care.+
  1. 1Provide sensory aids, footwear, analgesia, nutrition and the usual walking aid and remove unnecessary tethers.
  2. 2Set daily transfer, chair, toileting and walking goals with therapy and nursing assistance matched to risk.

Complications

01

Delirium and prolonged cognitive loss

Acute brain dysfunction increases aspiration, falls, distress, length of stay and incomplete return to cognitive baseline.

02

Hospital-associated deconditioning

Immobility and dependence during routine care can create new transfer, toileting and walking needs after disease resolution.

03

Pressure, thrombosis and infection

Bed rest, catheters and poor intake produce secondary skin, venous, respiratory and urinary complications during a prolonged admission.

04

Medicine-related harm

Acute kidney or liver change, duplicate reconciliation and sedative escalation can prolong the deterioration treatment was intended to reverse.

05

Unplanned institutionalisation

Failure to restore baseline function or strengthen community support can turn a temporary crisis into permanent placement.

Monitoring and follow-up

  • Trend NEWS2 components, urine, mental state and treatment response rather than relying on one observation set.
  • Repeat 4AT and compare cognition with collateral as pain, sleep, medicines and illness change.
  • Record transfers, chair time, walking distance, aid, ADLs and assistance against the stable baseline.
  • Track oral intake, weight, swallowing, bowel, bladder and pressure-prone skin during admission.
  • Review renal and hepatic function and the restart or dose plan for every temporarily changed medicine.
  • Confirm equipment, care visits, medication supply and named follow-up before and soon after transition.
  • Reconsider missed diagnosis, treatment complication and unmet rehabilitation when recovery plateaus unexpectedly.

Special situations

Function is a vital sign

A sudden lost transfer or meal can reveal serious illness before conventional observations become markedly abnormal.

No fever is not reassurance

Frailty and immune impairment can blunt temperature response during significant infection.

CGA begins during resuscitation

Baseline, medicines and goals improve acute decisions and need not wait until physiology is completely stable.

Bed rest has a dose

Every avoidable day without standing and walking increases muscle and postural impairment.

A ceiling is not a floor

A decision against one burdensome treatment never justifies withholding analgesia, antibiotics, nutrition or ordinary nursing care.

Common pitfalls

  1. 01

    Writing general decline without describing tempo, baseline and failed functions.

  2. 02

    Using frailty to explain acute symptoms before ABCDE and cause assessment.

  3. 03

    Treating a positive urine result as the cause of delirium without compatible infection features.

  4. 04

    Omitting time-critical medicines during swallowing or reconciliation delays.

  5. 05

    Keeping catheters, bed rest and hospital clothing for staff convenience.

  6. 06

    Using a frailty score alone to deny acute investigation or treatment.

  7. 07

    Discharging after biochemical recovery while transfers and medication administration remain unsafe.

Practice

Two practice questions

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Medicine of older adultsOriginal SBA

Atypical deterioration in frailty

An 88-year-old with frailty becomes newly confused, stops walking and eats little over one day, without fever. What is the best immediate approach?

Choose one answer, then submit
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG94 emergency and acute medical careInitial assessment, escalation and coordinated acute care.
  • NICE CG103 deliriumRecognition, risk, multicomponent prevention and management.
  • British Geriatrics Society CGA HubComprehensive geriatric assessment and multidisciplinary planning.
  • NICE NG249 falls recommendationsInjury, gait, medicine and falls assessment.
  • NICE NG5 medicines optimisationReconciliation and safe medicine transitions.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Choose tests from the syndrome. Commonly useful investigations include FBC, renal and electrolytes, glucose, liver, CRP, ECG and urinalysis or chest imaging when indicated. Lactate, cultures, troponin, blood gas, CT or other imaging answer specific questions. Asymptomatic bacteriuria is common and does not explain delirium by itself. A normal early test does not close a strongly supported diagnosis.

Reconcile all medicines and the last dose. Time-critical Parkinson's, insulin, steroid replacement and antiseizure treatment must continue or be safely substituted. Review anticoagulants after injury and renally cleared or sedating medicines after dehydration. Temporary withholding may be necessary, but document indication, stop criteria and restart review rather than allowing an acute pause to become accidental permanent discontinuation.

Begin comprehensive geriatric assessment while acute treatment proceeds. Identify frailty severity, multimorbidity, prognosis, cognition, capacity, mood, falls, mobility, ADLs, nutrition, swallowing, continence, skin, sensory impairment, social support and what matters to the person. CGA is a coordinated process that produces an integrated plan and follow-through, not a single assessment form.

Protect function deliberately. Provide the usual walking aid, footwear, glasses and hearing devices. Encourage washing, dressing, chair meals and toilet use with the assistance required; remove catheters, cannulas and monitoring when no longer necessary. Treat pain before movement and prescribe physiotherapy and occupational therapy goals that progress beyond passive range or referral-only plans.

Balance fluids, oxygen, analgesia and medicines against organ reserve. A person with heart failure may require small fluid aliquots and frequent lung, perfusion and urine reassessment; chronic hypercapnic respiratory failure requires controlled oxygen; low body weight or liver risk changes paracetamol limits; kidney injury changes opioid and anticoagulant exposure. Explicitly record these modifiers at handover.

Discuss treatment escalation early when serious disease and frailty coexist. Explain the acute diagnosis, likely reversibility and what ward, critical-care or resuscitation treatment would involve. Use decision-specific capacity and advance decisions or a relevant lasting power of attorney. A frailty score supports prognosis and planning but must not be used alone to deny beneficial assessment or treatment.

Plan discharge from the stable baseline and current trajectory rather than from bed availability. Confirm mobility, transfers, toileting, cognition, oral intake, medication administration and night support. Arrange equipment and carers before transfer. Communicate pending tests, new baseline, warning signs, medicine changes, rehabilitation and who reviews within an appropriate interval.

After discharge, review whether the acute disease resolved and whether delirium, weight loss, pressure injury or new dependency persists. Reopen missed diagnoses if recovery stalls. Medication, falls and bone review, vaccination and advance-care planning may be appropriate once the person is stable, without overwhelming the immediate recovery plan.

Key points

  • Frailty is vulnerability to stress, not a diagnosis explaining acute deterioration; new confusion or mobility loss should trigger a medical assessment.
  • First-line assessment combines ABCDE, glucose, NEWS2, pain and injury review with collateral about cognition, mobility, ADLs, intake and medicines before illness.
  • Classic symptoms may be absent: pneumonia can present as delirium, myocardial infarction as weakness, and urinary retention as agitation.
  • Use 4AT for possible delirium and investigate hypoxia, infection, pain, retention, constipation, dehydration, medicines and environmental triggers.
  • Reconcile time-critical treatment, anticoagulants, insulin, opioids, anticholinergics and renally cleared medicines immediately after arrival.
  • Investigations follow the syndrome and red flags; indiscriminate testing does not replace examination, trend review and diagnostic ownership.
  • Begin comprehensive geriatric assessment early, covering medical disease, function, cognition, mood, nutrition, continence, sensory needs, medicines, carers and goals.
  • Prevent deconditioning from the first safe day through normal clothing, chair meals, toilet walking, repeated mobilisation and prompt removal of unnecessary tethers.
  • Discuss escalation and resuscitation proportionately using the acute diagnosis, likely reversibility, baseline, values and treatment burden rather than age alone.
  • A safe transition names owners for pending results, medicine changes, rehabilitation, equipment, nutrition and early community follow-up.
  • Acute abdominal pain, distension, vomiting, gastrointestinal bleeding or peritonism requires surgical and resuscitation assessment.
  • Abrupt delirium, missed time-critical medicines, hypoglycaemia, retention or faecal loading requires rapid reversible-cause treatment.
  • Unexplained injury, neglect, carer conflict or absence of essential food, heating or medicines raises a safeguarding concern.
    • Use imaging and biomarkers for a defined question and escalate persistent clinical concern despite an initially normal study.
  • 06
    Comprehensive geriatric assessment
    Why
    Integrate treatment with function and goals.
    Interpretation and limitations
    Combine medical, cognitive, functional, medicine, nutrition, continence, skin, social and carer findings into one owned plan.
  • 07
    Home and support assessment
    Why
    Test whether recovery can continue safely.
    Interpretation and limitations
    Assess equipment, access, meal and medicine support, night care, transport, safeguarding and carer capacity before transition.
  • 3EscalationMeasure recovery against the stable baseline and escalate disease, pain, fear or support barriers when progress stalls.
    • 03Escalation and goals routeMatch treatment to reversible benefitEscalationSerious disease raises ward, critical-care or resuscitation decisions.+
    1. 1Clarify diagnosis, reversibility, current physiology, baseline and likely treatment burden with senior multidisciplinary input.
    2. 2Support capacity, check advance decisions and involve the legally appropriate representative when capacity is absent.
    3. 3Record agreed ceilings, symptom treatment and review triggers without allowing a limitation decision to reduce ordinary care.
    04Transition and recoveryPrevent a temporary crisis becoming permanentAcute physiology improves but function or support remains below baseline.+
    1. 1Reassess cognition, mobility, continence, intake, skin, medicine administration and carer capacity and identify reversible barriers.
    2. 2Arrange rehabilitation, equipment and care before transfer and communicate pending results, medicine actions and warning signs.
    3. 3Review early in the community and reopen diagnosis or support when recovery does not follow the expected trajectory.