Post-operative hypotension is a blood pressure that has fallen below the patient's normal after surgery, and on a surgical ward it is hypovolaemia until proven otherwise. The CST answer runs through the CCrISP structure: immediate ABCDE with a 500 ml crystalloid bolus under NICE CG174 if the triggers are met, a full assessment that decides between bleeding, sepsis, the epidural, the heart and the drugs, and a plan with a named escalation.

Key takeaways

  • According to NICE CG174, the indicators for fluid resuscitation are a systolic under 100 mmHg, a heart rate over 90, a capillary refill over 2 seconds or cold peripheries, a respiratory rate over 20, a NEWS of 5 or more, or a positive passive leg raise.
  • CG174's bolus is 500 ml of a crystalloid containing 130 to 154 mmol/L of sodium over less than 15 minutes, followed by reassessment before the next.
  • If the cause is bleeding, NICE NG39 says do not use crystalloid in hospital for active bleeding; give plasma and red cells at 1:1 and call the surgeon.
  • If the cause is sepsis, NICE NG253 gives 250 ml boluses over 10 to 15 minutes up to 1,000 ml, with antibiotics within 1 hour for high-risk patients.
  • The surgical differential is bleeding, sepsis, hypovolaemia from unreplaced losses, an epidural or opioid, a cardiac event, anaphylaxis and a tension pneumothorax after a line.
  • Hypotension that does not respond to one or two boluses is a call to the registrar and to critical care, not a third bag.

How do I recognise significant post-operative hypotension?

Recognise it against the patient's baseline, because a systolic of 95 mmHg is normal for a fit 25-year-old and dangerous for a hypertensive 80-year-old. The signs that make it significant are tachycardia, cool peripheries, falling urine output, confusion, a rising lactate and a NEWS2 that is climbing.

The chart tells you the trend. A pressure that has drifted down over six hours with a rising pulse is a bleed or a leak; a pressure that fell within minutes of a drug is the drug.

What is the surgical differential?

  • Haemorrhage: from the operative site, into a drain, or hidden in the abdomen, pelvis or thigh
  • Hypovolaemia without bleeding: nil by mouth, vomiting, nasogastric losses, a high-output stoma, third-spacing after a laparotomy
  • Sepsis: a collection, a leak, pneumonia, a urinary or line infection, usually from day three onwards
  • Neuraxial and drugs: an epidural running too high, a patient-controlled analgesia bolus, an antihypertensive given on an empty tank
  • Cardiac: myocardial infarction, new atrial fibrillation, heart failure
  • Obstructive and allergic: tension pneumothorax after a central line, pulmonary embolism, anaphylaxis to an antibiotic

What is the immediate management from A to E?

Immediate management is ABCDE with the patient flat and legs raised, oxygen, two wide-bore cannulae, bloods including a gas and a crossmatch, and a 500 ml crystalloid bolus over less than 15 minutes if the CG174 indicators are met. Then reassess, because the response to the first bolus is the most useful test you have.

  • Airway and breathing: patent airway, respiratory rate, saturations, oxygen to 94 to 98%, and a look for the tracheal deviation of a tension pneumothorax if a line went in today
  • Circulation: pulse, blood pressure, capillary refill, jugular venous pressure, the drains, the wound and the abdomen; access, bloods, crossmatch, a venous gas for lactate and haemoglobin, and the bolus
  • Disability: conscious level, pupils, capillary glucose, and the height of the epidural block if there is one
  • Exposure: temperature, the calves, the thighs, a rash for anaphylaxis, and the full drug chart

According to NICE CG174, the bolus is a crystalloid containing sodium in the range 130 to 154 mmol/L, 500 ml over less than 15 minutes, with expert help sought early in patients with complex fluid problems or significant comorbidity. Say that you would reassess by ABCDE after it and repeat if the indicators persist.

That said, if the patient is bleeding the crystalloid is a bridge at most. NG39 is explicit that hospitals do not use crystalloid for active bleeding, and the right fluid is blood at a 1:1 plasma to red cell ratio.

Which investigations find the cause?

The investigations that find the cause are the venous gas, for lactate and haemoglobin, the full blood count and clotting, an ECG, and imaging chosen by the story: a chest X-ray for the chest, a CT of the abdomen and pelvis with contrast for a suspected bleed or collection in a stable patient. Blood cultures and a CRP go with any fever.

In practice the lactate is the number to say. A raised lactate that falls after the bolus means you were right about hypovolaemia; a lactate that keeps rising means bleeding or sepsis and a phone call.

What is the definitive management?

Definitive management is the treatment of the cause you have found, and the panel expects each branch said briefly. Bleeding goes back to theatre or to interventional radiology; sepsis gets antibiotics within 1 hour and source control; the epidural is turned down or stopped by the anaesthetist; the cardiac event goes to the medical team with aspirin under NICE NG185 if it is an acute coronary syndrome.

How does the fluid differ by cause?

  • Hypovolaemia without bleeding: CG174's 500 ml boluses, reassessed, then replacement of the losses you have measured
  • Bleeding: NG39's blood components, tranexamic acid as soon as possible, and the major haemorrhage protocol
  • Sepsis: NG253's 250 ml boluses to 1,000 ml, then senior advice and vasopressors under critical care
  • Cardiogenic: cautious fluid or none, and a medical or cardiology opinion

When do I escalate, and who do I call?

Escalate after the first bolus if the pressure has not responded, and immediately if you suspect bleeding. The registrar is the first call for every hypotensive surgical patient, and critical care is the second when the cause needs vasopressors, blood or a level 2 bed.

  • Any suspected bleed: the registrar and the operating consultant, plus the major haemorrhage call
  • No response to two boluses: the registrar in person and critical care outreach
  • An epidural or opioid cause: the on-call anaesthetist, who owns the block
  • A cardiac cause: the medical registrar, with the ECG in your hand
  • NEWS2 of 7 or more: the emergency response, with the consultant informed

How do I structure the answer in the room?

Structure it as CCrISP: immediate management by ABCDE with the bolus, then a full assessment of the chart, the history of the operation, an examination from head to toe and the results, then a decision to treat or investigate with a written plan, a review time and a named escalation. Say the stages by name; the panel is marking the structure.

What is the interviewer listening for?

  • The CG174 indicators and the 500 ml bolus stated as numbers, then reassessment
  • A surgical differential that puts bleeding first and includes the epidural
  • Blood for bleeding and NG253 boluses for sepsis, rather than one fluid for everything
  • The lactate used as the marker of whether the plan is working
  • Escalation after the first non-response, with the registrar and critical care named

What are the common mistakes?

  • A third and fourth bag of crystalloid instead of a phone call
  • Not looking under the blanket at the drains, the wound and the thighs
  • Missing the epidural as the cause, and giving fluid to a vasodilated patient
  • Forgetting the ECG in a patient over 50
  • Documenting 'fluid challenge given' without the volume, the time or the response

How this comes up at the CST interview

The CST management and clinical station scores a structured approach, knowledge, prioritisation and communication, and post-operative hypotension is the purest test of the structure. There is no single diagnosis to get right; there is an order to work in, and numbers to attach to it.

coresurgeryinterview has 299 questions with AI-marked spoken practice, and its hypotensive day-one patient scenario is scored on the CCrISP order, the CG174 bolus and the escalation, which is why candidates who rehearse it aloud stop reaching for the third bag.