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Vascular Surgery — AAA, CEA, Peripheral
TEXTSpecialty I · 10 min read
Aortic cross-clamp, carotid clamp, contrast nephropathy. The vascular OR runs on three shared physiology lessons.
After this lesson you can
4 min read8 sections- Manage AAA cross-clamp hemodynamics.
- Plan spinal cord protection in thoracoabdominal AAA.
- Choose regional vs general for CEA.
- Anticipate ischemia-reperfusion at unclamping.
Open AAA — cross-clamp physiology
SUPRACELIAC CLAMP (above the celiac axis): worst hemodynamic insult — proximal hypertension can be severe (SBP 180-220+), LV strain + subendocardial ischemia, distal hypoperfusion to gut/kidney/spinal cord.
- most common in elective AAA
- more tolerable
- mostly affects the lower extremities
- vasodilator drawn up + ready (clevidipine 1-2 mg/hr titrated, nitroglycerin gtt, nicardipine)
- DEEPEN ANESTHESIA before clamp goes on
- ensure adequate volume + cardiac output
Aggressive volume + vasopressor + correction of acidosis.
Spinal cord protection in TAAA
The anterior spinal artery is fed by the artery of Adamkiewicz, which arises variably from T8-L2 intercostal arteries — easily occluded by clamp or graft coverage.
10 mmHg, drain 10-15 mL/hr to optimize spinal cord perfusion pressure (SCPP = MAP - CSFP).80-90 mmHg during clamp + post-clamp.32-34°C for neuroprotection.MEP LOSS during procedure immediate response: release distraction, raise MAP to ≥100, drain more CSF, replace lost blood/fluid, communicate with surgeon to consider intercostal reimplantation.
Endovascular AAA repair (EVAR)
- GA (most common for major EVAR)
- epidural
- or LOCAL + sedation for bilateral percutaneous closure devices
Major considerations: CONTRAST NEPHROPATHY (pre-hydration, minimize contrast volume, hold NSAIDs/ACE-I), GROIN ACCESS COMPLICATIONS (femoral pseudoaneurysm, retroperitoneal hematoma), ENDOLEAK on completion angiogram (Type I = proximal/distal seal failure, Type II = collateral backflow, Type III = component separation, Type IV = graft porosity, Type V = endotension).
Shorter ICU stay + lower 30-day mortality than open AAA, but long-term renal events more common + ongoing surveillance imaging required (annual CT angio).
CEA — regional vs GA + monitoring
Awake CEA under REGIONAL anesthesia (superficial + deep cervical plexus block, C2-C4): continuous neurologic monitoring during cross-clamp by simply asking the patient to squeeze your hand + talk.
Real-time detection of clamp-induced hemispheric ischemia.
GA: better BP + ventilation control + patient comfort, but requires SURROGATE monitoring (NIRS cerebral oximetry, EEG, SSEPs, transcranial Doppler, stump pressure measurement) for ischemia detection.
GALA TRIAL (Lancet 2008, 3,500 patients): equivalent stroke + death outcomes between regional and GA — operator + institution + patient preference guide the choice.
NIRS most commonly used adjunct under GA; rSO2 drop ≥20% from baseline during clamp suggests need for shunt placement.
CEA — hemodynamic + hyperperfusion management
Use phenylephrine for hypotension.
POST-OP HYPERPERFUSION SYNDROME (1-3% of CEAs): a chronically ischemic hemisphere is suddenly reperfused after carotid stenosis is removed impaired cerebral autoregulation unilateral headache severe HTN seizure INTRACEREBRAL HEMORRHAGE.
Onset hours to several days postop.
STRICT BP CONTROL post-CEA: SBP <140 mmHg, often LOWER than the patient's baseline (use clevidipine, labetalol, or nicardipine drip if needed).
NEURO CHECKS hourly × 24 hr.
New headache or focal deficit STAT CT/MRI + neurosurgery consult.
Peripheral vascular surgery + DVT prophylaxis
Long cases with positioning concerns + heparinization for vessel clamp + significant blood loss possible (especially redo bypass).
Heparin 100-150 U/kg pre-clamp, ACT >250-300, protamine reversal at end.
Watch for compartment syndrome post-revascularization (reperfusion injury) — fasciotomy may be required.
DVT/PE PROPHYLAXIS for all major vascular cases: SCDs intra-op, heparin 5000 U SC q8h or LMWH postop, early ambulation.
Anticoagulation timing for postop epidural removal: ASRA guidelines.
Contrast nephropathy prevention
- pre-existing CKD (especially eGFR <60)
- diabetes mellitus
- age >70
- dehydration
- concurrent NSAIDs/ACE-I/diuretics
- large contrast volume
- repeated contrast within 72 hr
1 mL/kg/hr 12 hr pre-procedure + 12 hr post; some use NaHCO3 protocols), MINIMIZE contrast volume (work with interventionalist), HOLD nephrotoxic drugs morning of procedure.N-acetylcysteine evidence weak in modern trials — not first-line.
Sodium bicarbonate vs saline equivalent in PRESERVE trial (2018).
Highest-risk patients may need IN-PROCEDURE HEMOFILTRATION.
Check creatinine 48-72 hours post-contrast; most recover spontaneously in 1-2 weeks but CIN-related AKI carries higher long-term mortality.
Heparin + protamine
Heparin 100-150 U/kg IV before peripheral clamp, target ACT >250-300 sec.
(Cardiopulmonary bypass is a separate dosing regimen: 300-400 U/kg with ACT target >400-480 sec — see cardiac surgery lecture.) Recheck ACT every 30 min on heparin.
PROTAMINE reversal at end of case: 1 mg per 100 U heparin given in last 2-3 hr (max single dose 50 mg, slow IV push over 5+ min — fast push causes pulmonary HTN + RV failure + cardiovascular collapse).
Verify protamine in chart for known reactions.
⚠ Common pitfalls
- Unclamping AAA without volume + vasopressor ready — washout of acid + K + decline in SVR.
- Missing the MEP signal loss — raise MAP first; CSF drainage second.
- CEA awake monitoring without an alternative plan — patient agitation derails the case.
- Forgetting renal protection in supra-renal clamps — cold renal flush + mannitol.
💎 Clinical pearls
- Spinal cord ischemia after thoracoabdominal AAA: 5-15% — CSF drain to ICP <10 + maintain MAP ≥80.
- Awake CEA = real-time neuro monitoring; GA = controlled airway + smooth emergence; pick by patient + surgeon.
- EVAR avoids cross-clamp entirely → much lower morbidity but type-II endoleak common.
- Carotid sinus reflex during dissection: brady + hypotension — local infiltration of sinus by surgeon.
Recap
- Spinal cord ischemia after thoracoabdominal AAA: 5-15% — CSF drain to ICP <10 + maintain MAP ≥80.
- Awake CEA = real-time neuro monitoring; GA = controlled airway + smooth emergence; pick by patient + surgeon.
- EVAR avoids cross-clamp entirely → much lower morbidity but type-II endoleak common.
- Carotid sinus reflex during dissection: brady + hypotension — local infiltration of sinus by surgeon.
Mark each section done to complete the module.