• Systolic BP <100 mmHg; mean arterial pressure <60 mmHg
• fall in systolic BP > 40 mmHg in a hypertensive patient’s usual pressure
• Tachycardia/bradycardia
• Drowsiness/altered mental state
• Nausea/vomiting
• Cold, clammy peripheries

Timing of hypotensive episode

• If soon after surgery, consider bleeding
• see Post-operative haemorrhage guideline in the Surgical guidelines
• Thromboembolism is a late complication of surgery
• After thoracic surgery/central venous catheter placement, consider pneumothorax
• At any time, consider septic shock
• associated with fluid extravasation and hypovolaemia

Hypovolaemia

• Bleeding from;
• wound, into chest/abdomen/pelvis, into soft tissue (e.g. fractures)
• within GI tract
• Gastrointestinal losses
• vomiting, diarrhoea
• when obstructed, into bowel lumen
• Polyuria or inappropriate diuretic treatment
• Increased insensible losses
  • from skin in burns
  • respiratory tract in tachypnoea
  • sweating in pyrexia or hot/dry environments
• Reduced intake of fluid 

Markers

• Heart rate: tachycardia unless on rate limiting drugs
• JVP or CVP: decreased
• Peripheries: cold

Cardiac failure from intrinsic cardiac defect

• Valvular disease
• Myocardial infarction
• Bradycardia or other arrhythmia
• Cardiomyopathy

Markers

• Heart rate: moderate tachycardia
  • severe bradycardia or tachycardia in arrhythmia induced hypotension
• JVP or CVP: raised or normal
• Peripheries: cold

Cardiac failure from mechanical flow defect

• Cardiac tamponade
• Pulmonary embolism
• Tension pneumothorax

Markers

• Heart rate: tachycardia
• JVP or CVP: markedly increased
• Peripheries: cold

Vasodilated state

• Sepsis, particularly Gram-negative sepsis. See Sepsis management guideline
• High spinal or epidural anaesthesia
• Neurogenic shock e.g. high spinal cord injury
• Anaphylaxis
• Adrenal failure (also leads to volume depletion)

Markers

• Heart rate: tachycardia
• JVP or CVP: decreased
• Peripheries: warm

Drugs

• Common examples include:
• abrupt withdrawal of corticosteroids (or failure to increase dosage in stressed patients who are unable to mount their own stress response)
• angiotensin-converting enzyme (ACE) inhibitors/angiotensin II receptor antagonists
• anti-anginal agents
• antihypertensive agents
• diuretics
• phenothiazines

Examination

• Temperature, pulse (rate, volume , character) and BP
• Check for visible bleeding
• JVP or if central line in place, check CVP
• Examine for tracheal deviation
• Chest examination for:
• pneumothorax, pulmonary oedema
• infective pathology and heart sounds
• Check urine output hourly via catheter

Investigations

• FBC
• U&E
• ABG to assess acid-base status
• where available, Hb, lactate and electrolytes
• ECG
• look for myocardial infarction, pulmonary embolism or cardiac arrhythmia
• Chest X-ray
• look for pneumonia, pneumothorax, pulmonary oedema or cardiac enlargement
• Consider focused bedside echocardiogram with the help of a trained operator
• look for LV function, RV function and/or dilation, pericardial tamponade and signs of hypovolemia

• Run immediate treatment and investigations simultaneously
• If high probability of pulmonary embolism, follow Pulmonary embolism guidelines

Supportive therapy

• Ensure airway patency. If necessary, open and protect airway and support respiration
• Commence oxygen therapy. See Oxygen therapy in acutely hypoxaemic patient guideline
• Establish reliable intravenous access; preferably two
  • unless clear evidence suggests a cardiac problem, give compound sodium lactate (Hartmann’s) solution or sodium chloride 0.9%500 mL IV as quickly as possible. See Fluid resuscitation guideline
• If severe bleeding suspected as cause for hypotension, activate major haemorrhage protocol
• Stop/omit any contributing drugs
• If not already catheterised, catheterise
• If initial treatment not effective, involve senior colleague or intensive care at an early stage

Treat cause

• Establish underlying cause and treat/refer as appropriate
• thrombolysis for massive PE
• needle thoracentesis for tension pneumothorax
• cardiology input
• surgical/intervention radiology for haemorrhagic hypotension
• fluids and vasopressors for vasodilated and septic patients

• Pulse, BP and respiratory rate every 15 min until stability achieved
• Urine output hourly
• Arterial blood gases to monitor lactate and base excess 1–2 hrly until stability achieved
• Consider invasive monitoring in the form of arterial pressure and central venous pressure monitoring in a high dependency area if problems persist

• Treat underlying cause promptly
• Give further IV fluid as indicated in Fluid management guideline
• For ongoing haemorrhage give blood and blood products, see:
• Blood and blood products or
• Transfusion section of Surgical guidelines