Study guide
13.2 VTE in the Neuro ICU (01.T.5)
ABIM Neurocritical Care Subspecialty Certification Exam
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Eligibility, Practice Pathway, and the IM Training Route 1.3 Format, Scoring, Pearson VUE, and Score Reports 1.4 How to Use This Independent Study Guide
2 ICU Neurologic Exam, Cerebral Physiology, and CSF
2.1 Neurological Examination in the ICU 2.2 Cerebral Physiology, ICP, CBF, and Autoregulation 2.3 CSF Physiology
3 Core Neuropharmacology
3.1 Osmotic Agents 3.2 Anti-Seizure Drugs 3.3 Anesthetics, Sedatives, Analgesia, and Paralytics 3.4 Antihypertensives, Vasopressors, and Inotropes
4 Reperfusion Drugs, Airway, and Ventilation
4.1 Thrombolytics, Anticoagulants, and Antiplatelets 4.2 Reversal of Anticoagulation After Acute Hemorrhage 4.3 Airway Management and Tracheostomy 4.4 Mechanical Ventilation
5 Hemodynamics and Shock
5.1 Hemodynamic Monitoring 5.2 IABP, Temporary VADs, LVAD, and ECMO 5.3 Diagnosis and Management of Shock
6 Nutrition, Temperature, and ICU Prophylaxis
6.1 Nutrition (01.J) 6.2 Temperature Control (01.K) 6.3 ICU Prophylaxis, Delirium, and Early Mobility (01.L)
7 General Trauma
7.1 Emergency Evaluation of Polytrauma, Chest, and Abdominal Trauma 7.2 Long-Bone Fractures and Fat Embolism 7.3 Burns, Electrical Injury, and Hanging/Strangulation
8 Pulmonary Critical Care
8.1 Pulmonary Physiology and ARDS (01.N.1–2) 8.2 PE, Pneumonia, and Pulmonary Edema (01.N.3, 7–8) 8.3 COPD, Asthma, PAH, and Bronchoscopy Basics (01.N.4–6, 9)
9 Cardiovascular Critical Care
9.1 Cardiovascular Physiology, Stress Cardiomyopathy, ACS, and Valves 9.2 Arrhythmias and Pacing 9.3 Acute Aortic Dissection and Cardiac Ultrasound
10 Renal and Infectious Disease
10.1 AKI, RRT, and Renal Drug Dosing 10.2 Acid-Base and Electrolyte Disorders 10.3 Severe Sepsis, Septic Shock, and Infective Endocarditis 10.4 Antimicrobial Use and Infection in the Immunosuppressed
11 Endocrine and Salt-Water Disorders
11.1 Pituitary Apoplexy, DI, and Panhypopituitarism (01.R.1–4) 11.2 SIADH and Cerebral Salt Wasting (01.R.5–6) 11.3 Thyrotoxicosis, Myxedema, Adrenal Crisis, and Dysglycemia (01.R.7–9)
12 Gastrointestinal Critical Care
12.1 GI Physiology, Acute Abdomen, Bleed, Ileus, and Perforation (01.S.1–5) 12.2 Mesenteric Ischemia and Abdominal Compartment Syndrome (01.S.6–7) 12.3 Fulminant Liver Failure, Cirrhosis Decompensation, and Hepatic Dosing (01.S.8–10)
13 Hematologic Disorders
13.1 Anemia, Transfusion, Thrombocytopenia, Coagulopathy, and DIC (01.T.1–4) 13.2 VTE in the Neuro ICU (01.T.5) 13.3 Chemo/Immune, SCT, CAR-T, Sickle Cell, and TMA (01.T.6–10)
14 Neuroimaging
14.1 CT of Brain and Spine 14.2 MRI and CT/MR Perfusion 14.3 Noninvasive Angiography and Catheter Angiography
15 EEG, EMG, and CSF Analysis
15.1 EEG, Standard and Processed (02.B) 15.2 Basic EMG Interpretation (02.G) 15.3 CSF Analysis (02.H)
16 ICP, TCD, and Multimodality Monitoring
16.1 ICP Monitoring (02.C) 16.2 Transcranial Doppler (02.D) 16.3 Brain-Tissue Oxygen and Multimodality Monitoring (02.E–F)
17 Brain Death and Bedside Procedures
17.1 Brain Death Prerequisites and Clinical Exam (02.I) 17.2 Apnea Testing and Ancillary Studies (02.I) 17.3 Vascular Access, Thoracic Echo, and Lung Ultrasound (02.J–L)
18 Coma, Anoxia, and Intracranial Hypertension
18.1 Coma and Other States of Altered Consciousness (03.A) 18.2 Global Anoxia-Ischemia and Post-Resuscitation Encephalopathy (03.A.1) 18.3 Toxidromes, ICU Delirium, and Hypertensive Encephalopathy (03.A.2–4) 18.4 Intracranial Hypertension as a Disease State (03.B)
19 Acute Ischemic Stroke
19.1 IV Reperfusion Therapy (03.C.3) 19.2 Mechanical Thrombectomy Windows and Imaging Selection (03.C.3) 19.3 Malignant Hemispheric Infarction and Basilar Artery Occlusion (03.C.1–2)
20 Intraparenchymal Hemorrhage
20.1 Intracerebral Hematoma (03.D.1) 20.2 Cerebellar Hematoma (03.D.2) 20.3 Intraventricular Hemorrhage (03.D.3)
21 SAH, CVST, and Spinal Cord Infarction
21.1 Aneurysmal Subarachnoid Hemorrhage (03.E.1) 21.2 Non-Aneurysmal SAH (03.E.2) 21.3 Cerebral Venous Sinus Thrombosis (03.F) 21.4 Spinal Cord Infarction (03.G)
22 Vascular Anomalies and Traumatic Brain Injury
22.1 Unruptured Aneurysm, Cavernoma, AVM, and Dural AVF (03.H) 22.2 Diffuse Axonal Injury and Cerebral Contusions (03.I.1–2) 22.3 Epidural Hematoma, Subdural Hematoma, and Penetrating Injury (03.I.3–4, 7) 22.4 Arterial Dissection and Carotid-Cavernous Fistula (03.I.5–6)
23 Spine, Hydrocephalus, and CNS Infection
23.1 Spinal Cord Injury, Central Cord, and Neurogenic Shock (03.J) 23.2 Unstable Spine Fractures (03.K) 23.3 Hydrocephalus and CSF Diversion (03.L) 23.4 Acute CNS Infections (03.M)
24 Seizures and Neuromuscular Emergencies
24.1 Status Epilepticus and Seizures (03.N) 24.2 Guillain-Barré Syndrome (03.O.1) 24.3 Myasthenic Crisis (03.O.2) 24.4 Motor Neuron Disease, Acute Myopathies, Rhabdomyolysis, and CINM (03.O.3–6)
25 Inflammatory Disease, Neuro-Oncology, and Special Populations
25.1 Fulminant Demyelinating Diseases (03.P) 25.2 Autoimmune Encephalitis and Acute Autonomic Hyperactivity (03.Q–R) 25.3 Neuro-Oncology and Treatment Complications (03.S) 25.4 Pregnancy/Post-Partum, Post-Transplant, and Pediatric Patients (03.T–U)
26 Neurosurgical and Perioperative Complications
26.1 Postoperative Seizures, Hemorrhage, Ischemia, and Hyperperfusion (04.A, C, D, H) 26.2 Infection, CSF Leak, and Pneumocephalus (04.B, E, F) 26.3 Complications of EVD and Lumbar Drain (04.G, I)
27 Ethics, Prognostication, and Organ Donation
27.1 Communication, Decision-Makers, Advance Directives, and DNR (05.A, B, G) 27.2 Uncertainties of Prognostication and the Self-Fulfilling Prophecy (05.C) 27.3 Palliative Care, Withdrawal, Withholding, and Futility (05.D–F) 27.4 Donation After Cardiac Death and Care of the Organ Donor (05.H–I)
13.2 VTE in the Neuro ICU (01.T.5)
Key Takeaways Explain This Topic AI
Start intermittent pneumatic compression on admission in nonambulatory ICH, TBI, SAH, and postoperative patients unless a limb contraindication exists; graduated compression stockings alone are not VTE prophylaxis.
Pharmacologic prophylaxis after ICH, TBI, or craniotomy is often begun in a 24–72 hour window if imaging is stable, but the evidence is limited, class of recommendation is modest, and no universal hour is proven.
AHA/ASA 2022 states that low-dose UFH or LMWH beginning 24–48 hours after ICH onset may be reasonable (Class 2b) and that IPC from the day of diagnosis is Class 1.
When therapeutic anticoagulation is absolutely contraindicated after proximal DVT, a retrievable IVC filter can bridge; retrieve it when anticoagulation becomes possible. Filters are not add-on therapy on top of anticoagulation (PREPIC2).
HIT is a falling platelet count plus thrombosis 5–10 days after heparin (sooner if recent exposure): stop all heparin, start a non-heparin anticoagulant such as argatroban, and do not start warfarin until the count recovers.
Last updated: September 2026
A dense hemiparesis, an EVD, a craniotomy dressing, and a week of bed rest are a venous thrombosis machine. Pulmonary embolism ( PE ) then competes with hematoma expansion for the title of preventable death. This independent ExamFinch section covers venous thromboembolism ( VTE ) prophylaxis and treatment in the neuro ICU as listed in the ABPN Content Specifications. It is not an ABIM or ABPN product. The examination reward is knowing what starts immediately , what waits on a stable scan , and what to do when PE and intracranial bleeding occupy the same patient.
Mechanical prophylaxis starts now
Intermittent pneumatic compression (IPC) belongs on the calves (or thighs, device-dependent) as soon as the patient is nonambulatory, unless a limb is ischemic, has an untreated acute DVT already being managed, or has a wound that the sleeve would destroy. The CLOTS 3 trial in acute stroke showed that IPC reduced proximal deep-vein thrombosis ( DVT ). The CLOTS 1 trial showed that graduated compression stockings did not prevent DVT after stroke and caused skin injury. The 2022 American Heart Association/American Stroke Association ( AHA/ASA ) ICH guideline therefore gives IPC starting on the day of ICH diagnosis a Class 1 recommendation in nonambulatory patients, and it gives stockings alone a Class 3 (no benefit) recommendation. TBI, SAH, and craniotomy patients get the same mechanical logic even when the Class 1 citation is written for ICH: the clot risk begins on hour one, and heparin is not yet on board.
IPC compliance is the hidden failure mode. Sleeves on the floor, sleeves off for a trip to CT, and sleeves omitted on a crushed leg all count as “no prophylaxis.” Document why a limb is uncovered and cover the other limb.
Pharmacologic timing: a window, not a universal hour
Low-dose unfractionated heparin (UFH) (commonly 5,000 units subcutaneously every 8–12 hours) or low-molecular-weight heparin (LMWH) (commonly enoxaparin 40 mg daily, adjusted for renal failure and extreme weight) reduces PE. After a brain bleed or a fresh craniotomy, that benefit is purchased with a theoretical risk of hematoma growth. Randomized evidence that pins a single safe hour is thin. Practice and modest-grade guidelines therefore speak in windows , contingent on hematoma stability on repeat imaging, not on a fake universal stopwatch.
For spontaneous ICH , AHA/ASA 2022 says low-dose UFH or LMWH can be useful to reduce PE (Class 2a) and that starting 24–48 hours from ICH onset may be reasonable to balance thrombosis prevention against hematoma expansion (Class 2b). That is not a command to dose heparin at hour 24 in every patient. An expanding hematoma, an uncorrected coagulopathy, or an untreated aneurysm is a reason to wait. A stable repeat CT, controlled blood pressure, and completed reversal are reasons to start inside that window rather than waiting a week.
For TBI and after craniotomy , many protocols start prophylactic heparin or LMWH 24–72 hours after injury or surgery if a repeat CT shows a stable hematoma . Neurocritical Care Society VTE guidance has suggested initiating prophylaxis by 24–48 hours when hemorrhage is not expanding, but centers still vary, and the supporting trials are not large randomized comparisons of hour 24 versus hour 72. Say that on the examination: evidence is limited and practice varies . Do not invent “always at 36 hours” or “never before day 7.” Coordinate with the neurosurgeon after craniotomy; an unexpected postoperative hematoma resets the clock.
After aneurysmal SAH , mechanical prophylaxis starts immediately. Pharmacologic prophylaxis is commonly deferred until the aneurysm is secured and then started within a day or two if there is no further bleeding — again a practice pattern, not a universal hour. After ischemic stroke without hemorrhage, pharmacologic prophylaxis can start once hemorrhage has been excluded, often the same day, because there is no hematoma to expand. After intravenous thrombolysis, many services wait 24 hours and a stable follow-up scan before heparin, mirroring post-lytic imaging practice.
LMWH is more effective than UFH for DVT prevention in several medical populations and is convenient once-daily. UFH is easier to stop and is preferred by some surgeons immediately after craniotomy and in fluctuating renal function. Neither is treatment-dose anticoagulation.
Setting Mechanical Pharmacologic prophylaxis (typical practice) Certainty
Nonambulatory ICH IPC day of diagnosis Low-dose UFH/LMWH often 24–48 h if hematoma stable (AHA/ASA 2022, Class 2b) IPC: strong; drug timing: modest
- TBI IPC on arrival Often 24–72 h if repeat CT stable Limited RCT timing data
- After craniotomy IPC immediately Often 24–72 h if no unexpected hematoma Surgeon-dependent
- SAH, unsecured aneurysm IPC Usually wait until secured Practice pattern
- Ischemic stroke, no bleed IPC Same day after hemorrhage excluded Stronger medical-stroke evidence
- Stockings alone Not sufficient Not a substitute CLOTS 1 / AHA Class 3
- When PE and ICH occupy the same patient
This is the conflict the examination writes as a stem. A patient day 3 after ICH develops hypoxia, tachycardia, and a CT pulmonary angiogram that shows a proximal PE — or a duplex that shows an iliofemoral DVT. Full-dose anticoagulation now risks hematoma expansion. Withholding anticoagulation now risks fatal PE. There is no randomized “correct hour” for therapeutic anticoagulation after ICH.
AHA/ASA 2022 offers two modest statements. In ICH with proximal DVT who are not yet candidates for anticoagulation , temporary use of a retrievable inferior vena cava (IVC) filter is reasonable as a bridge until anticoagulation can start (Class 2a). In ICH with proximal DVT or PE, delaying treatment-dose UFH or LMWH 1–2 weeks after ICH onset might be considered (Class 2b). That delay is not mandatory and is not safe if the PE is obstructive and the right ventricle is failing. Massive PE with shock after a fresh ICH is a multidisciplinary catastrophe: systemic thrombolysis is usually off the table, catheter-based thrombectomy may be considered in selected centers, and a filter does not treat the clot already in the pulmonary arteries. Document the competing risks, image the hematoma, and do not pretend a single protocol covers every combination of PE size and hematoma age.
IVC filters reduce PE in the short term in older trials (PREPIC) but increase subsequent DVT and cause strut fracture, migration, and IVC thrombosis when left in place. PREPIC2 found that adding a retrievable filter to anticoagulation in PE with a high recurrence-risk score did not reduce recurrent PE at 3 months. The examination use-case is therefore narrow: anticoagulation absolutely contraindicated , preferably a retrievable device, with an explicit retrieval plan when the contraindication lifts. Do not place a permanent filter “just in case” in a 40-year-old who will be anticoagulated next week.
Heparin-induced thrombocytopenia
HIT is an immune reaction to platelet factor 4 ( PF4 )–heparin complexes. IgG antibodies activate platelets, producing thrombocytopenia plus thrombosis (arterial or venous), not bleeding. Timing is classically day 5–10 of heparin. If the patient received heparin within the previous 30 days (some scores allow up to 100 days), the count can crash within 24 hours of re-exposure (rapid-onset HIT). A drop of more than 50% from the postoperative peak, even if the nadir is still above 50 × 10^9/L, is enough. Skin necrosis at injection sites and anaphylactoid reactions to heparin boluses are HIT until proven otherwise.
Score pretest probability with the 4Ts : magnitude of thrombocytopenia, timing, thrombosis or other sequelae, and the presence of another cause. Low probability (0–3) makes HIT unlikely. Intermediate (4–5) or high (6–8) scores warrant laboratory testing and, if clinical suspicion is not low, immediate management. Send an immunoassay (anti-PF4/heparin ELISA). Confirm with a functional assay (serotonin-release assay or heparin-induced platelet activation) when the ELISA is positive or the clinic picture is compelling. Do not wait for the serotonin-release assay to stop heparin if the 4Ts score is intermediate or high.
Management is three simultaneous moves. Stop all heparin , including catheter flushes, heparin-coated lines, and LMWH. Start a non-heparin anticoagulant — argatroban (hepatically cleared; it raises the INR and complicates warfarin overlap), bivalirudin , or, in selected stable patients with adequate kidneys, fondaparinux or a direct oral anticoagulant. Do not start warfarin until platelets have substantially recovered; premature warfarin can cause venous limb gangrene through protein C depletion. Platelet transfusion is generally avoided in HIT unless there is life-threatening bleeding, because adding platelets to an activating antibody can worsen thrombosis.
UFH causes HIT more often than LMWH. Fondaparinux rarely causes HIT. Patients with recent heparin need a baseline platelet count and monitoring while exposed. A falling count on heparin after craniotomy is not “surgical consumption” by default if the timing and a new DVT fit HIT.
- 4Ts domain Higher-probability pattern
- Thrombocytopenia >50% fall, nadir ≥20 × 10^9/L
- Timing Day 5–10, or ≤1 day if heparin in the prior month
- Thrombosis New VTE/arterial clot, skin necrosis, systemic heparin reaction
- Other causes No alternative explanation for the drop
- Exam traps
Do not delay IPC until “the hematoma is stable.” Do not claim a randomized trial proved that every post-craniotomy patient must start LMWH at a single clock time. Do not treat PE after ICH with a week of observation and no filter and no anticoagulation plan. Do not leave a retrievable filter in for life. Do not treat HIT with warfarin while the count is still 20 × 10^9/L, and do not “just give platelets” for HIT.