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Post-Operative Hypotension

I. Definition

  • Hypotension =
  • SBP < 90 mmHg OR
  • MAP < 65 mmHg OR
  • Drop > 40 mmHg from baseline
  • Clinical significance depends on organ perfusion: altered mental status, oliguria, lactic acidosis, or chest pain indicate shock regardless of the number.

II. Principles

  • Post-op hypotension may be benign (residual anesthesia, mild hypovolemia) or life-threatening (hemorrhage, cardiogenic shock, sepsis, anaphylaxis).
  • Think in categories:
  • Tank (volume problem): hemorrhage, hypovolemia, third spacing
  • Pump (cardiac problem): MI, arrhythmia, tamponade, cardiomyopathy, PE
  • Pipes (resistance problem): sepsis, anaphylaxis, adrenal insufficiency, epidural vasodilation
  • Unstable patient with hypotension = shock until proven otherwise.
  • Restart chronic antihypertensives early when safe, especially beta-blockers and clonidine, to avoid rebound instability. Hold ACEi/ARB if ongoing hypotension.

III. Stepwise Evaluation

Step 1 – Confirm

  • Recheck BP manually, ensure correct cuff.
  • Review trends and correlate with HR, SpO₂, urine output.
  • Confirm with arterial line if available.

Step 2 – Assess Stability

  • ABCs first.
  • Check mental status, urine output, cap refill, extremity temperature.
  • If unstable → call senior/ICU and start resuscitation immediately.

Step 3 – Focused History & Exam

  • History: blood loss, fluid balance, epidural use, missed antihypertensives.
  • Exam:
  • Surgical site, drains, dressings → bleeding/hematoma
  • JVP, heart sounds, lungs → CHF, tamponade, pneumothorax
  • Abdomen → distension, rigidity, leak
  • Extremities → warm vs cold, mottling, DVT signs

Step 4 – Immediate Workup

  • Continuous vitals and strict I/O.
  • CBC (H/H), BMP, lactate.
  • Coagulation profile if bleeding suspected.
  • ECG (ischemia, arrhythmia).
  • CXR (pneumothorax, pulmonary edema).
  • POCUS: IVC, LV/RV function, tamponade, pericardial effusion.
  • CT chest/abdomen/pelvis if bleeding or leak suspected and patient stable.

IV. Management

General Measures

  • Airway, Breathing, Circulation.
  • O₂, 2 large-bore IVs, monitor.
  • Type & crossmatch if bleeding suspected.

Stepwise by Category

1. Tank (Volume/Hemorrhage/Third Spacing)

  • 500–1000 mL crystalloid bolus → reassess.
  • Repeat bolus or escalate to blood products if inadequate.
  • Search for bleeding (surgical site, chest, abdomen, retroperitoneum).
  • Massive transfusion protocol if active hemorrhage.

2. Pump (Cardiac Dysfunction)

  • EKG, troponin, echo.
  • Arrhythmia → treat per ACLS.
  • MI/cardiogenic shock → cardiology, inotropes (dobutamine, milrinone).
  • Tamponade → pericardiocentesis or surgical decompression.

3. Pipes (Vasodilation/Maldistribution)

  • Sepsis → cultures, broad antibiotics, source control, fluids.
  • Anaphylaxis → epinephrine, antihistamines, steroids.
  • Adrenal insufficiency → stress-dose hydrocortisone.
  • Epidural-induced vasodilation → pause infusion, fluids, vasopressors.

4. Persistent Hypotension Despite Fluids

  • Start vasopressors: norepinephrine = first-line.
  • Add vasopressin or epinephrine if refractory.
  • ICU transfer for invasive monitoring and advanced support.

V. Red Flags – Call Senior Immediately

  • Hypotension unresponsive to 1–2 L crystalloid.
  • Suspected active bleeding or falling hemoglobin.
  • Hypotension with chest pain, arrhythmia, or new ST changes.
  • Hypotension with hypoxia or respiratory distress (PE, tamponade, pneumothorax).
  • Hypotension with altered mental status or rising lactate.
  • MAP < 60–65 mmHg sustained despite fluids.

VI. Intern Pearls

  • Hypotension is never normal post-op — always find the cause.
  • Use Tank → Pump → Pipes to stay systematic.
  • Heart rate clues:
  • Tachycardia → volume loss, sepsis.
  • Bradycardia → meds, conduction block, vagal.
  • Response to fluids is diagnostic: improvement = tank problem.
  • Persistent hypotension despite fluids → pressors + ICU.
  • Always consider occult bleeding (retroperitoneum, hemothorax, intra-abdominal).
  • Restart chronic antihypertensives early if safe to prevent rebound.

Key Takeaways

  • Define hypotension clinically: MAP < 65 or SBP < 90 with poor perfusion.
  • Tank, Pump, Pipes framework organizes causes.
  • Stepwise: Confirm → Assess stability → Focused exam → Workup → Resuscitate.
  • MAP < 60–65 is dangerous and requires prompt action.
  • Early senior/ICU involvement is critical — hypotension is never benign post-op.