Cardiac events, blood pressure problems, and clots (DVT/PE)
Blood pressure changes are common—and sometimes important
Anaesthetic drugs, bleeding, dehydration, sepsis, and neuraxial blocks can all reduce blood pressure. Mild, brief hypotension is often tolerated in healthy patients; prolonged or profound hypotension can reduce perfusion to the heart, brain, and kidneys.
Common causes of intraoperative hypotension
- Vasodilation from anaesthetic agents (propofol, volatiles)
- Relative hypovolemia (fasting, bowel prep, diuretics, dehydration)
- True hypovolemia (blood loss)
- Neuraxial block (sympathetic blockade)
- Sepsis or anaphylaxis (rare but critical)
Hypertension and tachycardia
Pain, inadequate depth, hypercapnia, hypoxia, bladder distension, and withdrawal states can drive sympathetic surges. These can be more concerning in patients with coronary disease or aneurysms.
Myocardial ischemia/infarction (MI)
Perioperative MI risk depends heavily on baseline cardiac disease, surgical stress, blood loss, and hemodynamic instability. In many patients, perioperative events are “demand ischemia” (supply-demand mismatch) rather than plaque rupture.
Arrhythmias: AF, SVT, VT, bradycardia, asystole
- Atrial fibrillation can be triggered by surgical stress, hypoxia, electrolyte imbalance, or underlying heart disease.
- SVT/VT are less common but can occur with ischemia, catecholamine surges, or drug effects.
- Bradycardia/asystole may occur with vagal stimulation (e.g., traction, ocular surgery), neuraxial blockade, hypoxia, or drug interactions.
Blood clots: DVT and pulmonary embolism (PE)
Surgery increases clot risk via inflammation, immobility, and hypercoagulability. Risk is procedure- and patient-specific. Prevention commonly includes early mobilization, compression devices, and anticoagulant prophylaxis where appropriate.
Who is higher risk?
- Major cancer surgery; pelvic/hip surgery; prolonged immobility
- Prior DVT/PE; thrombophilia; estrogen therapy; pregnancy/postpartum
- Obesity, smoking, older age, heart failure