Acute Medicine: Shock, sepsis and critical illness

• Shock: What Is Shock? | Types of Shock | Assessing the Shocked Patient | Fluid Resuscitation | Vasopressors and Inotropes
• Sepsis: Defining Sepsis | Recognising Sepsis | The First Hour -Sepsis Six | Source Identification, Antibiotics and Source Control | Septic Shock | Sepsis in Special Groups | Sepsis with Rash -Meningococcal and Toxic Shock
• Other shock states: Cardiogenic and Obstructive Shock | Haemorrhagic Shock in Medical Patients | Anaphylactic Shock
• Critical illness: Multi-organ Dysfunction, ARDS and DIC
• Revision: Shock and Sepsis at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🩺 Shock, sepsis and critical illness -page 3 of the Acute Medicine and Resuscitation chapter. Shock means the tissues aren't getting enough oxygen -and it kills quickly unless the cause is found and fixed. Sepsis is the commonest cause of shock on medical wards, causing about 48,000 deaths a year in the UK; every hour's delay in antibiotics for septic shock increases mortality. Infection-specific detail is in the Infectious Diseases chapter on Sepsis; trauma haemorrhage is on the Major Trauma page.
Your four questions for every shocked patient: Is the patient shocked (BP, lactate, perfusion, urine output, mental state)? What type of shock is it -hypovolaemic, distributive, cardiogenic or obstructive? What treatment is needed in the next hour (fluids, antibiotics, blood, vasopressors, source control)? Does the patient need critical care -and is that within their ceiling of care?

What Is Shock?

• Shock -a state of inadequate tissue perfusion and oxygen delivery, leading to cellular dysfunction and organ failure.
• Oxygen delivery = cardiac output × arterial oxygen content (Hb × saturation); cardiac output = heart rate × stroke volume; blood pressure = cardiac output × systemic vascular resistance.
• Hypotension is a late sign -compensation (tachycardia, vasoconstriction) maintains BP until a lot of volume or function is lost, especially in young people.
• Signs of shock:
  • Tachycardia (may be absent with beta-blockers, pacemakers, hypothermia, older people).
  • Hypotension -systolic under 90 mmHg, MAP under 65 mmHg, or a fall over 40 mmHg from baseline.
  • Poor peripheral perfusion -cold, mottled skin, prolonged capillary refill (warm peripheries early in distributive shock).
  • Reduced urine output -under 0.5 mL/kg/hour.
  • Altered mental state -anxiety, confusion, drowsiness.
  • Raised lactate -over 2 mmol/L (over 4 = severe).
  • Tachypnoea (compensating for metabolic acidosis).
• Mean arterial pressure (MAP) = diastolic + one-third of (systolic − diastolic); target MAP 65 mmHg or more for most patients (higher in some chronic hypertension).

Types of Shock

• Mixed shock is common -e.g. sepsis with dehydration and septic cardiomyopathy.
• Neurogenic shock -loss of sympathetic tone after cord injury above T6 -hypotension with bradycardia and warm skin.
• Endocrine causes -adrenal crisis (hyponatraemia, hyperkalaemia, steroid use), myxoedema coma, thyroid storm.

Assessing the Shocked Patient

• ABCDE with high-flow oxygen, two large-bore cannulas, monitoring, and a senior early.
• Key bedside measurements -HR, BP (and MAP), capillary refill, skin temperature and mottling, JVP, urine output (catheter), conscious level, temperature, respiratory rate.
• Blood gas and lactate -metabolic acidosis, lactate (a marker of hypoperfusion and response to treatment), Hb, potassium, glucose.
• Bloods -FBC, U&E, LFTs, CRP, clotting (DIC), group and crossmatch, troponin, cultures, amylase or lipase, cortisol (if adrenal crisis suspected -but don't delay hydrocortisone).
• ECG -MI, arrhythmia, right heart strain (PE), low voltages (tamponade).
• Imaging -chest X-ray; point-of-care ultrasound (by trained staff) -heart function, pericardial effusion, RV dilatation, IVC size, free fluid, pneumothorax, AAA; CT for source (abdomen, PE).
• History -bleeding (melaena, haematemesis, PV bleeding), fluid losses, infection symptoms, chest pain, allergens, medications (anticoagulants, steroids, antihypertensives), trauma.
• Response to fluid -passive leg raise (fluid responsiveness), reassessment after boluses.

Fluid Resuscitation

• Crystalloids -500 mL bolus over under 15 minutes (NICE CG174), then reassess; balanced crystalloids (Hartmann's, Plasma-Lyte) or 0.9% sodium chloride; avoid starches (harm); albumin in specific situations.
• Sepsis -consider up to about 30 mL/kg in the first hours in septic shock (Surviving Sepsis), given as repeated boluses with reassessment; smaller boluses (250 mL) in heart failure, frailty or kidney failure.
• Haemorrhage -blood and blood products early rather than large volumes of crystalloid; major haemorrhage protocol (red cells, plasma, platelets in balanced ratios; fibrinogen; tranexamic acid where indicated).
• Signs of fluid overload -rising JVP, crackles, falling SpO₂, worsening breathlessness, peripheral oedema -stop fluids and consider vasopressors and critical care.
• After 2 litres without improvement (or earlier if lactate over 4 or MAP under 65) -critical care review for vasopressors.
• Don't over-resuscitate -positive fluid balance is linked with worse outcomes in sepsis and critical illness.
• Hypovolaemia from losses (vomiting, diarrhoea) -replace fluid and electrolytes (potassium, sodium) carefully.

Vasopressors and Inotropes

• Used in critical care (or HDU) with arterial line monitoring, usually via a central line (noradrenaline can be started peripherally short-term in some settings).
• Vasopressors (increase vascular tone):
  • Noradrenaline -first-line in septic shock (alpha-1 vasoconstriction, some beta-1); titrated to MAP 65 mmHg.
  • Vasopressin -second-line added to noradrenaline in septic shock.
  • Metaraminol and phenylephrine -short-term bolus or peripheral infusion (anaesthesia, peri-intubation).
• Inotropes (increase contractility):
  • Dobutamine -cardiogenic shock (beta-1); can cause hypotension (vasodilation) and arrhythmias.
  • Adrenaline -inotrope and vasopressor (anaphylaxis, refractory shock, cardiac arrest).
  • Milrinone (phosphodiesterase inhibitor), levosimendan (calcium sensitiser) -specialist.
• Steroids -hydrocortisone 200 mg/day in septic shock needing ongoing vasopressors (reduces time on vasopressors); essential in adrenal crisis.
• Mechanical support -intra-aortic balloon pump, Impella, ECMO (specialist centres).

Defining Sepsis

• Sepsis (Sepsis-3, 2016) -life-threatening organ dysfunction caused by a dysregulated host response to infection.
• Organ dysfunction -an acute change in SOFA (Sequential Organ Failure Assessment) score of 2 points or more (respiratory, coagulation, liver, cardiovascular, CNS, kidney).
• Septic shock -sepsis with circulatory and metabolic abnormalities severe enough to increase mortality: needs vasopressors to keep MAP at 65 mmHg or more and has a lactate over 2 mmol/L despite adequate fluid resuscitation (mortality over 40%).
• qSOFA (bedside prompt -one point each) -respiratory rate 22 or more, altered mentation, systolic BP 100 mmHg or less; 2 or more suggests higher risk (but not a screening tool for sepsis -NEWS2 is preferred in the UK).
• Older terms -"SIRS" criteria and "severe sepsis" are no longer used in Sepsis-3.
• Common sources -chest (most common), urinary tract, abdomen (perforation, cholangitis, abscess), skin and soft tissue, lines and devices, meningitis, endocarditis, bone and joints.

Recognising Sepsis

• Think "could this be sepsis?" in anyone with suspected infection who is unwell, or with unexplained deterioration -especially if NEWS2 is raised.
• NICE NG51 (2024 update) -uses NEWS2 to stratify risk in adults (16 and over, not pregnant) in acute hospitals:

  NEWS2	Risk of severe illness or death from sepsis	Action
  7 or more	High	Senior review; antibiotics within 1 hour; IV fluids; critical care review
  5–6	Moderate	Senior review within 1 hour; antibiotics within 3 hours (sooner if a clear infection source or worsening -within 1 hour if, e.g., AKI, high lactate, or neutropenia)
  1–4	Low (but higher if, e.g., new confusion, recent chemotherapy)	Clinical assessment; antibiotics within 3 hours if bacterial infection confirmed or likely

• Higher-risk groups -older and frail people, immunosuppressed (chemotherapy, steroids, biologics, transplant), recent surgery or invasive procedures, pregnancy or recent birth, IV drug use, indwelling lines, asplenia, diabetes, very young children.
• Red flags in any setting -new confusion, systolic BP 90 or less, HR over 130, RR 25 or more, needing oxygen to keep SpO₂ 92% or more, non-blanching rash, mottled or ashen skin, no urine for 18 hours, lactate 2 or more, recent chemotherapy.
• Atypical features -no fever (or hypothermia), normal WCC, presenting only with confusion or falls in older people.

The First Hour -Sepsis Six

• Sepsis Six (UK Sepsis Trust) -complete within 1 hour for high-risk patients:

  Step	Give three	Step	Take three
  1	Oxygen to target saturations (94–98% or 88–92%)	4	Blood cultures (and other cultures -urine, sputum -before antibiotics if no delay)
  2	IV antibiotics -broad-spectrum per local guidance, within 1 hour	5	Lactate (and full bloods -FBC, U&E, LFTs, CRP, clotting, glucose)
  3	IV fluids -500 mL bolus, repeat with reassessment if hypotensive or lactate raised	6	Urine output -hourly measurement (catheter if needed)

• Plus:
  • Senior review and escalation -critical care if lactate over 4, systolic BP under 90 despite fluids, or needing high oxygen or with reduced consciousness.
  • Find the source -history, examination, imaging.
  • Set a ceiling of care and communicate with the patient and family.
  • Review medicines -withhold antihypertensives, nephrotoxic drugs (NSAIDs, ACE inhibitors), metformin, SGLT2 inhibitors; steroid sick day rules.
  • Repeat lactate within 2–4 hours to assess response.

Source Identification, Antibiotics and Source Control

• Find the source -chest X-ray, urine (symptoms, culture -not dipsticks in over-65s), wound and line sites, abdominal examination (consider CT), skin (cellulitis, necrotising infection), joints, heart murmurs (endocarditis), neck stiffness (LP if meningitis suspected and safe), recent procedures.
• Empirical antibiotics -follow local microbiology guidelines; choose by suspected source, local resistance, allergies, recent antibiotics, MRSA or ESBL colonisation, and severity. Examples (vary locally):
  • Unknown source, high risk -e.g. piperacillin–tazobactam ± gentamicin (or a carbapenem if ESBL risk); add vancomycin or teicoplanin if MRSA risk.
  • Community-acquired pneumonia (severe) -co-amoxiclav plus clarithromycin.
  • Urosepsis -e.g. co-amoxiclav plus gentamicin, or as local policy.
  • Intra-abdominal -piperacillin–tazobactam (or co-amoxiclav + gentamicin + metronidazole regimens).
  • Meningitis -ceftriaxone 2 g IV (± amoxicillin if Listeria risk, ± dexamethasone).
  • Neutropenic sepsis -piperacillin–tazobactam within 1 hour.
• Source control -essential and time-critical:
  • Drain abscesses, empyema and infected collections.
  • Decompress an obstructed infected urinary tract (nephrostomy or stent).
  • ERCP for cholangitis; surgery for perforation, ischaemic bowel, necrotising fasciitis.
  • Remove infected lines and devices.
• Review at 48–72 hours -de-escalate based on cultures, switch to oral, set duration (Start Smart Then Focus -see the Clinical Pharmacology chapter).

Septic Shock

• Hypotension persisting despite adequate fluid, or lactate over 4 -critical care.
• Management (Surviving Sepsis Campaign):
  • Fluids -balanced crystalloids with frequent reassessment; avoid fluid overload.
  • Noradrenaline to a MAP of 65 mmHg; add vasopressin if needed; adrenaline or dobutamine if cardiac dysfunction.
  • Hydrocortisone 200 mg/day if needing ongoing vasopressors.
  • Antibiotics within 1 hour; source control.
  • Organ support -ventilation (lung-protective -ARDS), renal replacement therapy, blood glucose control (target about 8–10 mmol/L), VTE prophylaxis, stress ulcer prophylaxis where risk, nutrition.
  • Blood transfusion threshold -Hb 70 g/L in most.
• Lactate clearance and capillary refill time guide resuscitation.
• Sepsis survivors -often have weakness, fatigue, cognitive problems, anxiety and higher risk of readmission and death in the following year; "post-sepsis syndrome" -follow-up and rehabilitation.

Sepsis in Special Groups

• Neutropenic sepsis (neutrophils 0.5 × 10⁹/L or less, with fever over 38°C or signs of sepsis) -after chemotherapy (or carbimazole, clozapine, methotrexate) -empirical antibiotics (piperacillin–tazobactam) within 1 hour of presentation, without waiting for the FBC; acute oncology input (see the Oncology Emergencies chapter).
• Asplenia (splenectomy, sickle cell disease) -overwhelming post-splenectomy infection (pneumococcus, meningococcus, Hib) -rapid deterioration -immediate antibiotics.
• Pregnancy and post-partum -sepsis is a leading cause of maternal death; signs are masked by physiological changes; use the maternity early warning score; sources include genital tract (group A streptococcus), urinary, chest; involve obstetrics and consider fetal monitoring.
• Older people -atypical presentation (confusion, falls, low temperature); higher mortality; careful fluids; set ceilings of care.
• Immunosuppressed (steroids, biologics, transplant, HIV) -blunted signs, unusual organisms (PJP, fungi, CMV, Listeria); steroid users need extra hydrocortisone.
• People who inject drugs -endocarditis, abscesses, necrotising soft tissue infection, injection site infections (MRSA, group A strep, botulism, anthrax).
• Returning travellers -malaria (blood films), typhoid, viral haemorrhagic fever risk assessment.
• Hospital-acquired sepsis -lines, catheters, surgical sites, C. difficile, resistant organisms.

Sepsis with Rash -Meningococcal and Toxic Shock

• Meningococcal sepsis (Neisseria meningitidis):
  • Fever, non-blanching petechial or purpuric rash (glass test), limb pain, cold hands and feet, mottled skin, rapid deterioration; meningism may be absent.
  • Immediate IV or IM ceftriaxone (benzylpenicillin in primary care) -don't delay for tests; blood cultures and meningococcal PCR; critical care; DIC and purpura fulminans.
  • Notify UKHSA (public health); prophylaxis for close contacts (ciprofloxacin single dose).
• Toxic shock syndrome -toxins from Staphylococcus aureus (tampons, wounds, burns, nasal packing) or group A streptococcus:
  • High fever, diffuse red (sunburn-like) rash with later desquamation of palms and soles, hypotension, vomiting and diarrhoea, multi-organ failure.
  • Remove the source (tampon, packing), debride; IV antibiotics including clindamycin (stops toxin production); IVIG in severe cases; critical care.
• Necrotising fasciitis -pain out of proportion, rapid spread, shock -urgent surgery (see the Plastic Surgery page).
• Other causes of fever and rash -viral illnesses, drug reactions (DRESS, SJS), endocarditis (splinter haemorrhages, Janeway lesions), rickettsial infection, dengue, leptospirosis, vasculitis.

Cardiogenic and Obstructive Shock

• Cardiogenic shock -pump failure with hypoperfusion despite adequate filling:
  • Causes -large MI (commonest), mechanical complications (papillary muscle rupture -acute mitral regurgitation; ventricular septal rupture; free wall rupture), arrhythmias, myocarditis, Takotsubo, end-stage cardiomyopathy, valve disease, drug toxicity (beta-blockers, calcium channel blockers).
  • Features -cold, clammy, hypotensive, raised JVP, pulmonary oedema, low urine output, confusion, new murmur.
  • Management -oxygen, ECG and echo; urgent revascularisation (PCI) for MI; cautious fluids only if not congested; inotropes (dobutamine) and vasopressors (noradrenaline) in critical care; treat arrhythmias; CPAP or ventilation for pulmonary oedema; mechanical support; avoid beta-blockers and negative inotropes.
• Obstructive shock:
  • Massive PE -hypotension, hypoxia, raised JVP, RV dilatation on echo -thrombolysis (alteplase) if no contraindications; catheter or surgical embolectomy if contraindicated.
  • Tension pneumothorax -immediate decompression.
  • Cardiac tamponade -Beck's triad (hypotension, raised JVP, muffled heart sounds), pulsus paradoxus, low-voltage ECG, electrical alternans -pericardiocentesis (echo-guided).

Haemorrhagic Shock in Medical Patients

• Common medical causes -upper GI bleeding (peptic ulcer, varices), lower GI bleeding, ruptured AAA (back pain), retroperitoneal bleeding (on anticoagulants, after femoral procedures), ectopic pregnancy (women of childbearing age -pregnancy test), haemoptysis, bleeding on anticoagulants.
• Management:
  • ABCDE; two large-bore cannulas; crossmatch; FBC, clotting, fibrinogen, U&E (urea rises in upper GI bleeding), LFTs.
  • Activate the major haemorrhage protocol if bleeding is life-threatening; balanced blood products; avoid excessive crystalloid.
  • Reverse anticoagulants -PCC and vitamin K (warfarin); idarucizumab (dabigatran); andexanet alfa or PCC (factor Xa inhibitors).
  • Specific treatment -endoscopy (GI bleeding -within 24 hours, sooner if unstable), terlipressin and antibiotics for suspected variceal bleeding, interventional radiology (embolisation), surgery (AAA, ectopic).
  • Transfusion threshold -restrictive (Hb 70 g/L; 80 g/L with cardiovascular disease) once bleeding is controlled.
• Risk scoring -Glasgow–Blatchford score (pre-endoscopy -0 can be managed as outpatient), Rockall (post-endoscopy) (see the Gastroenterology Emergencies chapter).

Anaphylactic Shock

• Recognition -sudden airway and/or breathing and/or circulation problems, usually with skin or mucosal changes, after exposure to a trigger (drugs, foods, stings, contrast, latex).
• Treatment (RCUK 2021):
  • Remove the trigger; call for help; lie flat (sit up if breathing difficulty).
  • IM adrenaline 500 micrograms (0.5 mL of 1 mg/mL) in adults -repeat after 5 minutes if no improvement.
  • High-flow oxygen; IV fluid bolus (500–1,000 mL crystalloid).
  • Refractory (no improvement after 2 doses) -adrenaline infusion (experienced staff), more fluids, critical care; glucagon if on beta-blockers.
  • Not first-line -antihistamines (for skin symptoms once stable), steroids (no longer routinely recommended).
• After -mast cell tryptase (early and at 24 hours), observe (biphasic reactions), adrenaline auto-injectors, allergy referral, documentation (see the Clinical Pharmacology chapter).

Multi-organ Dysfunction, ARDS and DIC

• Multi-organ dysfunction syndrome (MODS) -progressive failure of two or more organs after severe illness (sepsis, trauma, pancreatitis, burns); mortality rises with each failing organ.
• Acute respiratory distress syndrome (ARDS):
  • Acute (within 1 week) hypoxaemic respiratory failure with bilateral infiltrates not fully explained by heart failure or fluid overload (Berlin definition -PaO₂/FiO₂ ratio grades severity).
  • Causes -direct (pneumonia, aspiration, inhalation, drowning, lung contusion) or indirect (sepsis, pancreatitis, trauma, massive transfusion -TRALI, burns).
  • Treatment -treat the cause; lung-protective ventilation (low tidal volume about 6 mL/kg ideal body weight, plateau pressure under 30 cmH₂O, PEEP); conservative fluids; prone positioning in severe ARDS; neuromuscular blockade; ECMO in selected cases.
• Disseminated intravascular coagulation (DIC):
  • Widespread activation of clotting -consumption of platelets and clotting factors -bleeding and thrombosis together.
  • Causes -sepsis (especially meningococcal), trauma, malignancy (acute promyelocytic leukaemia), obstetric emergencies (abruption, amniotic fluid embolism), severe liver failure.
  • Bloods -low platelets, prolonged PT and APTT, low fibrinogen, raised D-dimer, fragmented red cells.
  • Treatment -treat the cause; blood products if bleeding (platelets, FFP, cryoprecipitate for low fibrinogen); thromboprophylaxis where thrombosis predominates (see the Haematology chapters).
• AKI -common in sepsis -fluids, avoid nephrotoxins, renal replacement therapy if needed (see page 6).
• Critical illness polyneuromyopathy -weakness after prolonged ICU stay; rehabilitation.

Shock and Sepsis at a Glance

Spot the Diagnosis

Exam-style Scenarios

1. An 80-year-old woman is admitted from a care home with confusion and reduced urine output. Temperature 35.6°C, HR 112, BP 84/50, RR 26, SpO₂ 92% on air. Lactate 4.6. Chest X-ray shows right lower lobe consolidation.
Answer: Sepsis with probable septic shock (pneumonia).

• Sepsis Six within 1 hour -oxygen to target, blood cultures, IV antibiotics (severe CAP per local guidance), 500 mL fluid boluses with reassessment, lactate, urine output (catheter).
• Withhold antihypertensives and nephrotoxic drugs; repeat lactate; check for delirium and other sources.
• Senior and critical care review (lactate over 4, hypotension); agree ceiling of care with the patient and family (frailty, wishes).

2. A 55-year-old man with type 2 diabetes has fever, rigors and right loin pain. BP 88/52 despite 1.5 L of fluid. Lactate 5. CT shows a 7 mm obstructing ureteric stone with hydronephrosis.
Answer: Septic shock from an obstructed infected kidney.

• Continue resuscitation; IV antibiotics (per local urosepsis guidance); critical care referral for noradrenaline.
• Urgent source control -percutaneous nephrostomy or ureteric stent within hours.
• Withhold metformin and SGLT2 inhibitor; monitor glucose and ketones; definitive stone treatment later.

3. A 63-year-old man has crushing chest pain, then becomes cold and confused. BP 76/48, HR 110, bilateral crackles, SpO₂ 88%. ECG shows anterior ST elevation.
Answer: Cardiogenic shock from anterior STEMI.

• Oxygen (CPAP if needed), aspirin and antiplatelet per cath lab protocol, emergency primary PCI.
• Avoid large fluid boluses (pulmonary oedema); inotropes (dobutamine) ± noradrenaline in CCU or ICU; echo for mechanical complications.
• Consider mechanical circulatory support in a specialist centre.

4. A 32-year-old woman had chemotherapy for breast cancer 9 days ago. She has a temperature of 38.5°C and feels shivery. Observations are otherwise normal.
Answer: Suspected neutropenic sepsis.

• IV piperacillin–tazobactam within 1 hour of arrival -don't wait for the FBC.
• Blood cultures (peripheral and from any central line), FBC, U&E, LFTs, CRP, lactate, urine, chest X-ray.
• Contact the acute oncology team; reassess risk (MASCC score) for possible early discharge on oral antibiotics if low risk.

5. A 19-year-old student has a headache, fever and leg pains for 6 hours. He now has a purple non-blanching rash on his legs, cold hands, HR 130 and BP 90/50.
Answer: Meningococcal sepsis.

• Immediate IV ceftriaxone 2 g (don't delay for LP or imaging); blood cultures and meningococcal PCR.
• Fluid resuscitation; early critical care (rapid deterioration, DIC); watch for raised intracranial pressure.
• Notify UKHSA; ciprofloxacin prophylaxis for close contacts (household, kissing contacts).

Key Points

• Shock -inadequate tissue perfusion; hypotension is a late sign; look at lactate, CRT, urine output and mental state.
• Four types -hypovolaemic, distributive (sepsis, anaphylaxis, neurogenic), cardiogenic, obstructive (PE, tension, tamponade).
• Fluid challenge -500 mL over under 15 minutes, then reassess; avoid overload.
• Noradrenaline is the first-line vasopressor in septic shock; target MAP 65 or more.
• Sepsis -life-threatening organ dysfunction from a dysregulated response to infection.
• Septic shock -vasopressors needed for MAP 65 and lactate over 2 despite fluids.
• Use NEWS2 to stratify sepsis risk -7 or more: antibiotics within 1 hour.
• Sepsis Six -oxygen, cultures, antibiotics, fluids, lactate, urine output -within 1 hour.
• Source control is as important as antibiotics -drain, decompress, remove lines, operate.
• Neutropenic sepsis -antibiotics within 1 hour without waiting for the count.
• Non-blanching rash with fever -immediate ceftriaxone.
• Steroid users in shock need hydrocortisone.
• Cardiogenic shock -revascularise, inotropes, avoid excess fluid.
• Massive PE -thrombolyse; tamponade -pericardiocentesis; tension -decompress.
• ARDS -lung-protective ventilation, prone positioning; DIC -treat the cause, replace products if bleeding.