Antiphospholipid Syndrome (APS)

The prolonged aPTT is an in vitro artifact - APS antibodies interfere with phospholipids common to many laboratory coagulation tests. Despite the prolonged aPTT, APS poses no increased bleeding risk; it increases the potential for thrombosis. An isolated prolonged aPTT on a preop panel should raise APS as a diagnosis, not a bleeding disorder.

Neuraxial - The aPTT alone is not the barrier. In the absence of coagulation defects from clotting factor antibodies or a platelet abnormality, prolonged aPTT alone should not in theory predispose to hemorrhage or contraindicate an epidural. What actually drives the decision is the anticoagulant on board: identify the agent, the dose and the time of the last dose, and get a platelet count. Hold intervals are not quoted here on purpose - read them off the current ASRA anticoagulation guidelines (5th edition, 2025) rather than off a coagulation number or memory.

Define the anticoagulation plan before the day of surgery - Patients with a prior venous thrombotic event are on long-term warfarin with an INR goal of 2.0 to 3.0; after arterial thrombosis some target above 3.0. LMWH is used where warfarin is not tolerated or not effective. Perioperative complications are common in APS because surgery adds prothrombotic risk, so the hold-and-restart plan should be agreed with hematology in advance.

Thrombosis is the perioperative complication, not bleeding - Any organ can be involved, and APS thromboses sites that are unusual for other causes: upper extremity, Budd-Chiari, sagittal sinus. Keep sequential compression devices on, avoid prolonged stasis and unnecessary venous stasis from positioning, and get anticoagulation restarted as soon as surgical hemostasis allows.

Get an echo before assuming a normal heart - Valve involvement is very common, with prevalence as high as 80% in some series. Mitral and aortic valves show thickening, nodules and vegetations (Libman-Sacks) on echocardiography, and can produce regurgitation or stenosis.

Platelet count governs the neuraxial decision - Thrombocytopenia is present in more than 15% of APS patients. Counts above 50,000/mm3 need no treatment; below that, corticosteroids with or without IVIG or rituximab are used. Send a count on the day of surgery - it tells you far more than the aPTT does.

Catastrophic APS - CAPS occurs in under 1% of APS patients but carries 48% mortality. It is multi-organ thrombosis over a few days in small and medium arteries: ARDS and pulmonary hemorrhage, renal failure from thrombotic microangiopathy, ischemic stroke and encephalopathy, valve lesions, MI and heart failure, digital ischemia and gangrene, bowel infarction, thrombocytopenia. Treatment is anticoagulation and high-dose corticosteroids combined with IVIG, plasmapheresis, rituximab, cyclophosphamide or eculizumab. A postop APS patient failing in more than one organ system at once is CAPS until proven otherwise.

Renal and pulmonary workup - Hypertension, proteinuria and renal failure from thrombotic microangiopathy is the classic renal picture, and renal artery thrombosis causes refractory hypertension. Pulmonary embolism from DVT is common and can leave pulmonary hypertension behind. Check creatinine and urine protein preop, and get an echo for RV function and estimated PA pressure when there is a PE history.

Stroke risk is the arterial signature - TIA and ischemic stroke are the most common arterial manifestations and recur, leading to cognitive dysfunction, seizures and multi-infarct dementia. Retinal artery or vein occlusion can cause blindness. Hold the patient near their own baseline blood pressure rather than accepting permissive hypotension.

Pregnancy - Warfarin is teratogenic and must not be used in pregnancy. LMWH is preferred over unfractionated heparin for better bioavailability, longer half-life, once-daily dosing, and lower rates of thrombocytopenia and osteoporosis. Expect a higher rate of pre-eclampsia, fetal distress, IUGR, abruption, prematurity and HELLP. Plan the neuraxial window around the LMWH dosing schedule using the current ASRA intervals, not a remembered number.

Lupus anticoagulant testing is unreliable on anticoagulants - False positives and false negatives both occur in patients on heparin or warfarin. Don't chase or discard the diagnosis based on a test drawn while the patient is anticoagulated.

Look for the company it keeps - APS is secondary to SLE in about 40% of cases, and 50 to 70% of SLE patients with positive antibodies progress to APS. Check for an SLE diagnosis and its organ involvement; see the Systemic Lupus Erythematosus entry.

Antiphospholipid syndrome (APS) is an acquired autoimmune disorder in which autoantibodies against phospholipid-binding proteins - lupus anticoagulant, anticardiolipin, and anti-beta-2-glycoprotein I - produce arterial and venous thrombosis and pregnancy loss. It is primary in most patients and secondary to systemic lupus erythematosus (SLE) in about 40%. The antibodies are pathogenic rather than a marker: they upregulate tissue factor on monocytes and endothelium, antagonize endothelial nitric oxide synthase, activate complement and inhibit fibrinolysis, and they generally need a second hit of endothelial injury to tip into thrombosis. Surgery supplies exactly that second hit.

The paradox that trips people up is laboratory. These antibodies interfere with the phospholipid used in clotting assays, so the aPTT is prolonged in a patient who clots rather than bleeds.