Critical Care Ultrasound & Echocardiography

ABPN Neurocritical Care Study Guide Exam

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1 Chapter 1: Neurologic Examination & Coma Assessment in the ICU

Current Examination, Blueprint & Preparation Neurologic Examination in Critically Ill Patients Coma Evaluation & Consciousness Alterations Delirium & Toxic-Metabolic Encephalopathy in the ICU

2 Chapter 2: Cerebral Physiology & Intracranial Dynamics

Cerebral Blood Flow, Metabolism & Autoregulation Intracranial Pressure & Compliance Cerebral Edema & Herniation Syndromes

3 Chapter 3: Intracranial Hypertension & Cerebral Perfusion Management

Tiered ICP Management Protocols Hyperosmolar Therapy & Fluid Management Advanced & Refractory ICP Interventions

4 Chapter 4: Airway, Mechanical Ventilation & Pulmonary ICU Management

Emergency Airway Management & Neuro-Intubation Mechanical Ventilation Strategies in Acute Brain Injury Tracheostomy & Ventilator Weaning in Neurocritical Care Pulmonary Complications in the Neuro-ICU Obstructive Lung Disease, Pulmonary Hypertension & Bronchoscopy

5 Chapter 5: Hemodynamics, Shock & Cardiovascular Management

Hemodynamic Monitoring & Blood Pressure Targets Vasoactive Agents: Inotropes, Vasopressors & Antihypertensives Cardiac Complications of Brain Injury

6 Chapter 6: Neuropharmacology, Analgesia & Sedation

ICU Sedation & Analgesia Neuromuscular Blockade & Monitoring Propofol Infusion Syndrome & Drug Toxicities Antiseizure Drug Pharmacology in the ICU

7 Bleeding, Thrombosis & Hematologic Emergencies

Warfarin & Heparin Reversal Direct Oral Anticoagulant (DOAC) Reversal Antiplatelet Management & Platelet Dysfunction Venous Thromboembolism Prophylaxis & Management Transfusion, Coagulopathy, TMA & Cellular-Therapy Neurotoxicity

8 Chapter 8: Systemic ICU Care, Fluids, Electrolytes & Endocrine

Hyponatremia & Osmoregulation: SIADH vs Cerebral Salt Wasting Diabetes Insipidus, Hypernatremia & Endocrine Crises Critical Care Prophylaxis, Nutrition & Infection Prevention

9 Systemic Trauma & Environmental Injury

Polytrauma, Chest Injury & Abdominal Hemorrhage Burns, Electrical Injury & Hanging

10 Cardiac Emergencies & Mechanical Support

IABP, Ventricular Devices & ECMO Acute Coronary, Valvular, Rhythm & Aortic Emergencies

11 Kidney Injury, Acid–Base & Renal Replacement

Acute Kidney Injury & Renal Drug Clearance Acid–Base Disorders, Electrolytes & Renal Replacement

12 Systemic Infection & Endocrine Emergencies

Sepsis, Endocarditis & Antimicrobial Principles Thyroid, Adrenal & Dysglycemic Emergencies

13 Gastrointestinal & Hepatic Emergencies

Acute Abdomen, GI Bleeding & Abdominal Compartment Syndrome Acute Liver Failure, Cirrhosis & Hepatic Drug Effects

14 Chapter 9: Neuroimaging in the Neuro-ICU

Non-Contrast CT & CT Angiography CT Perfusion & Advanced Perfusion Imaging Magnetic Resonance Imaging in Critical Illness

15 Chapter 10: Electrophysiology & Neuromonitoring

Continuous EEG & ACNS Standardized Critical Care Terminology Invasive Neuromonitoring: ICP & External Ventricular Drains Multimodal Monitoring: PbtO2, Microdialysis & Transcranial Doppler

16 Angiography, Electrodiagnosis & CSF Analysis

Conventional Angiography & Cranial–Spinal Shunts EMG, Nerve Conduction & Acute Muscle Disease CSF Analysis: Infection, Inflammation & Hemorrhage

17 Chapter 11: Bedside Procedures, Ultrasound & Death by Neurologic Criteria

Critical Care Procedural Skills Critical Care Ultrasound & Echocardiography Determination of Death by Neurologic Criteria

18 Chapter 12: Acute Ischemic Stroke & Reperfusion Therapies

Acute Ischemic Stroke Management & Thrombolysis Endovascular Thrombectomy & Large Vessel Occlusion Malignant Hemispheric & Cerebellar Infarction

19 Chapter 13: Spontaneous Intracerebral Hemorrhage & Intraventricular Hemorrhage

Acute Intraparenchymal Hemorrhage Management Intraventricular Hemorrhage & Hydrocephalus Surgical Evacuation & Minimally Invasive Surgery in ICH

20 Chapter 14: Aneurysmal Subarachnoid Hemorrhage & Delayed Cerebral Ischemia

Aneurysmal Subarachnoid Hemorrhage: Acute Resuscitation & Securing Delayed Cerebral Ischemia & Cerebral Vasospasm Non-Aneurysmal Subarachnoid Hemorrhage & Vascular Malformations

21 Venous, Spinal & Traumatic Vascular Disease

Cerebral Venous Thrombosis & Spinal Cord Infarction Traumatic Dissection, Carotid–Cavernous Fistula & Penetrating Injury

22 Chapter 15: Traumatic Brain & Spinal Cord Injury

Severe Traumatic Brain Injury & Contusions Acute Traumatic Spinal Cord Injury & Neurogenic Shock Spine Trauma, Fractures & Cord Syndromes

23 Chapter 16: Status Epilepticus, Seizures & Neuromuscular Emergencies

Status Epilepticus: Convulsive & Non-Convulsive Refractory & Super-Refractory Status Epilepticus Acute Neuromuscular Respiratory Failure

24 Chapter 17: Post-Cardiac Arrest Care, CNS Infections & Encephalitis

Targeted Temperature Management & Post-Cardiac Arrest Care Post-Cardiac Arrest Neuroprognostication Acute CNS Infections, Encephalitis & Inflammatory Emergencies

25 Neuroinflammation & Neurooncology

Fulminant Demyelination & Autoimmune Encephalitis Brain, Spinal & Leptomeningeal Cancer Emergencies

26 Pregnancy, Transplantation & Pediatric Care

Pregnancy, Postpartum & Post-Transplant Neurologic Care Pediatric Neurocritical Care

27 Chapter 18: Neurosurgical & Perioperative Emergencies

Postoperative Neurosurgical Complications Device Complications: EVDs, Shunts & ICP Monitors Cerebral Hyperperfusion Syndrome & Post-Interventional Emergencies

28 Chapter 19: Ethics, Palliative Care & Organ Donation in the Neuro-ICU

Communication, Surrogate Decision-Making & Conflict Resolution Neuroprognostication Ethics, Withdrawal of Life Support & Palliative Care Organ Donation & Management of the Deceased Donor

Critical Care Ultrasound & Echocardiography

Key Takeaways Explain This Topic AI

Focused Cardiac Ultrasound (FOCUS) in the neuro-ICU rapidly identifies neurogenic stunned myocardium (Takotsubo pattern with apical ballooning and basal hypercontractility) and acute right ventricular strain resulting from pulmonary embolism.

McConnell's sign—characterized by right ventricular free wall akinesia with spared hyperdynamic apical contractility—demonstrates high specificity for acute pulmonary embolism in immobilized neurocritical patients.

Dynamic inferior vena cava (IVC) collapsibility (> 50% in spontaneous breathing) and distensibility (> 18% during passive mechanical ventilation without spontaneous triggers) guide volume resuscitation, though positive end-expiratory pressure, abdominal hypertension, and low tidal volume ventilation introduce significant diagnostic confounders.

Lung ultrasound using the BLUE protocol reliably identifies pneumothorax via the pathognomonic combination of absent pleural sliding and a localized lung point, while diffuse bilateral B-lines differentiate alveolar-interstitial edema from pure consolidative pneumonia.

Optic nerve sheath diameter (ONSD) measured strictly 3 mm posterior to the globe using a high-frequency linear probe provides a rapid, non-invasive surrogate for elevated intracranial pressure, where values exceeding 5.5 to 5.8 mm correlate with ICP > 20 mmHg.

Last updated: October 2026

Critical Care Ultrasound & Echocardiography

Point-of-care ultrasound (POCUS) represents an essential extension of the physical examination in the neuro-intensive care unit. By integrating Focused Cardiac Ultrasound (FOCUS), Lung Ultrasound (LUS), and Optic Nerve Sheath Diameter (ONSD) sonography, neurointensivists can diagnose shock states, titrate cardiopulmonary resuscitation, and non-invasively detect intracranial hypertension at the bedside in real time.

Focused Cardiac Ultrasound (FOCUS) in Neurocritical Care

Cardiovascular instability in neurocritical patients frequently stems from acute brain-heart crosstalk. Sympathetic hyperactivity provoked by subarachnoid hemorrhage, severe traumatic brain injury, or massive intracranial hypertension triggers myocardial injury, requiring rapid differentiation from primary coronary syndromes or hypovolemia.

Acoustic Windows & Core Views

FOCUS utilizes a phased-array cardiac probe ( 1.5 – 4 MHz 1.5\text{--}4\text{ MHz} 1.5 – 4 MHz ) across four standard acoustic windows:

Subcostal (Subxiphoid) 4-Chamber: Placed flat in the epigastrium pointing toward the left shoulder. Provides an unobstructed view of the pericardium, right ventricle ( R V RV R V ), and left ventricle ( L V LV L V ), serving as the premier view in mechanically ventilated patients where lung hyperinflation obscures parasternal windows.

Parasternal Long-Axis (PLAX): Placed in the 3rd or 4th left intercostal space adjacent to the sternum. Visualizes the aortic valve, mitral valve, left atrium, left ventricle, and the descending thoracic aorta . Differentiates pericardial effusion (fluid accumulating anterior to the descending aorta) from left pleural effusion (fluid tracking posterior to the descending aorta).

Parasternal Short-Axis (PSAX): Rotated 90 ∘ 90^\circ 9 0 ∘ clockwise from PLAX to obtain the mid-ventricular "doughnut" cross-section at the papillary muscle level. Evaluates regional wall motion and interventricular septal dynamics.

Apical 4-Chamber (A4C): Placed at the cardiac apex in the left 5th intercostal space, mid-clavicular line. Compares right-to-left chamber dimensions ( R V : L V RV:LV R V : L V ratio) and assesses tricuspid annular plane systolic excursion ( T A P S E TAPSE T A PSE ).

Neurogenic Stunned Myocardium & Takotsubo Cardiomyopathy

A massive endogenous catecholamine surge—typically observed following aneurysmal subarachnoid hemorrhage ( a S A H aSAH a S A H , 10 – 30 % 10\text{--}30\% 10 – 30% ) or severe intracranial hypertension—precipitates acute neurogenic stunned myocardium. FOCUS typically reveals stress-induced (Takotsubo) cardiomyopathy , characterized by apical and mid-ventricular akinesia/ballooning with compensatory basal hypercontractility . This pattern leads to abrupt cardiogenic pulmonary edema, elevated troponin, and profound hypotension that directly threatens cerebral perfusion.

Acute Cor Pulmonale & Pulmonary Embolism

Immobilized neurocritical patients carry an immense risk of deep vein thrombosis and pulmonary embolism ( P E PE PE ). FOCUS provides immediate recognition of acute right ventricular strain:

R V RV R V Dilation: Normal R V RV R V end-diastolic diameter is < 60 % < 60\% < 60% of L V LV L V diameter. An R V : L V RV:LV R V : L V ratio > 1.0 > 1.0 > 1.0 indicates severe acute R V RV R V enlargement.

Interventricular Septal Flattening ("D-Shaped" Left Ventricle): Increased R V RV R V afterload shifts the interventricular septum toward the left ventricle, transforming the circular L V LV L V into a "D" shape on the PSAX view. Systolic septal flattening denotes R V RV R V pressure overload (pulmonary embolism), whereas isolated diastolic septal flattening denotes R V RV R V volume overload.

McConnell's Sign: Regional R V RV R V free-wall akinesia with sparing and hyperdynamic contraction of the R V RV R V apex. This finding supports RV dysfunction but is not specific to acute PE and can occur with other causes such as RV infarction.

Tricuspid Annular Plane Systolic Excursion ( T A P S E TAPSE T A PSE ): M-mode measurement of lateral tricuspid annulus systolic excursion; values < 17 mm < 17\text{ mm} < 17 mm indicate acute right ventricular systolic failure.

Pericardial Tamponade

Characterized sonographically by an anechoic pericardial fluid stripe accompanied by early diastolic collapse of the thin-walled right ventricle , right atrial collapse, typically during ventricular systole , and a dilated, non-collapsible inferior vena cava.

Inferior Vena Cava (IVC) Respiratory Variation

The IVC is measured in the subcostal longitudinal view 1 – 2 cm 1\text{--}2\text{ cm} 1 – 2 cm caudal to the cavoatrial junction:

Spontaneous Breathing: Negative intrathoracic pressure on inspiration augments venous return, collapsing the IVC. A Collapsibility Index > 50 % [ ( I V C m a x − I V C m i n ) / I V C m a x × 100 % ] > 50\%\ [(IVC_{max} - IVC_{min}) / IVC_{max} \times 100\%] > 50% [( I V C ma x ​ − I V C min ​ ) / I V C ma x ​ × 100% ] correlates with low central venous pressure and volume responsiveness.

Passive Mechanical Ventilation: Positive pressure during inspiration impedes venous return, distending the IVC. In patients in sinus rhythm ventilated with tidal volumes ≥ 8 mL/kg \ge 8\text{ mL/kg} ≥ 8 mL/kg predicted body weight without spontaneous breathing efforts, a Distensibility Index > 18 % [ ( I V C m a x − I V C m i n ) / I V C m i n × 100 % ] > 18\%\ [(IVC_{max} - IVC_{min}) / IVC_{min} \times 100\%] > 18% [( I V C ma x ​ − I V C min ​ ) / I V C min ​ × 100% ] predicts fluid responsiveness.

Note

IVC dynamic indices are invalid in neurocritical patients receiving lung-protective low tidal volume ventilation ( 6 mL/kg 6\text{ mL/kg} 6 mL/kg ), patients triggering spontaneous breaths, or those with severe acute cor pulmonale, elevated positive end-expiratory pressure ( P E E P > 10 cmH 2 O PEEP > 10\text{ cmH}_2\text{O} PEEP > 10 cmH 2 ​ O ), or intra-abdominal hypertension.

Lung Ultrasound (LUS) & The BLUE Protocol

Lung ultrasound is significantly more sensitive than portable supine chest radiography for diagnosing acute respiratory failure, pneumothorax, and pulmonary edema in the ICU.

Acoustic Profiles & Artifacts

Normal Aeration (A-Profile): Visceral and parietal pleura slide against each other, generating dynamic lung sliding ("ants marching on a line" in 2D imaging, or the "seashore sign" on M-mode). Reverberation artifacts generate horizontal, hyperechoic A-lines at equidistant intervals from the pleural line.

Alveolar-Interstitial Syndrome (B-Profile): Accumulation of extravascular lung water creates vertical, hyperechoic "laser-like" artifacts called B-lines (comet tails). True B-lines originate from the pleural line, extend to the bottom of the acoustic field without fading, move synchronously with lung sliding, and erase underlying A-lines. ≥ 3 \ge 3 ≥ 3 B-lines per intercostal space define interstitial syndrome. Diffuse bilateral B-lines occur in cardiogenic pulmonary edema, acute respiratory distress syndrome ( A R D S ARDS A R D S ), and neurogenic pulmonary edema ( N P E NPE NPE ) .

Pneumothorax Identification: Pleural air separates parietal from visceral pleura, resulting in complete absence of lung sliding , absence of B-lines, and absence of lung pulse. On M-mode, the normal granular seashore pattern is replaced by horizontal parallel lines known as the "stratosphere sign" or "barcode sign" .

Important

Absence of lung sliding is sensitive but not entirely specific for pneumothorax (it can also occur in severe atelectasis, mainstem intubation, or pleural symphysis). Identification of the lung point —the precise acoustic interface where normal sliding lung alternates with the static barcode pattern of intrapleural air synchronously with respiration—is 100 % 100\% 100% specific for pneumothorax.

Consolidation & Effusion: Alveolar consolidation appears as tissue-like hepatization of the lung parenchyma with irregular hyperechoic borders (the "shred sign") and dynamic air bronchograms. Pleural effusions present as dependent anechoic fluid collections bounded by the chest wall and visceral pleura (the "quad sign"), displaying respiratory compression on M-mode (the "sinusoid sign").

Optic Nerve Sheath Diameter (ONSD) Ultrasonography

Invasive intracranial pressure monitoring via an external ventricular drain ( E V D EVD E V D ) or intraparenchymal bolt remains the gold standard but is contraindicated in severe coagulopathy or unavailable in non-neurosurgical environments. Transorbital sonography of the optic nerve sheath provides an immediate, non-invasive surrogate.

Anatomic Rationale & Sonoanatomy

The optic nerve ( C N I I CN\ II CN II ) is an embryologic tract of the central nervous system surrounded by the three meningeal layers: pia mater, arachnoid mater, and dura mater. The subarachnoid space surrounding the optic nerve communicates directly with the intracranial subarachnoid space. Consequently, acute elevations in intracranial pressure propagate freely into the perineural space, causing radial expansion of the retrobulbar optic nerve sheath.

Standardized Scanning Protocol

Equipment & Settings: A high-frequency linear array probe ( 7.5 – 12 MHz 7.5\text{--}12\text{ MHz} 7.5 – 12 MHz ) is adjusted to a low thermal and mechanical index ( M I < 0.23 MI < 0.23 M I < 0.23 ) to protect the retina from acoustic bioeffects.

Technique: The patient is placed supine. A generous layer of sterile acoustic coupling gel is applied over the closed upper eyelid. The probe is applied with minimal pressure to avoid globe indentation or vagal bradycardia.

Measurement Technique: The optic nerve is imaged in both the transverse and sagittal planes. The optic nerve sheath diameter ( O N S D ONSD ONS D ) must be measured strictly 3.0 mm 3.0\text{ mm} 3.0 mm posterior to the retina-globe interface , perpendicular to the acoustic axis of the nerve. This specific retrobulbar location represents the area of highest dural distensibility and pressure sensitivity. Globe

• (Eye Interior)
• /-----\
• | |
• | * | <-- Retina / Posterior Wall
• \-----/
• | <-- Exactly 3.0 mm distance
• [=====>] <-- Measure ONSD across sheath here (e.g., 5.8 mm)
• | |
• Optic Nerve
• Diagnostic Thresholds & Board Performance

Normal Value: Normal O N S D ONSD ONS D in healthy adults is < 5.0 mm < 5.0\text{ mm} < 5.0 mm .

Intracranial Hypertension Threshold: An O N S D > 5.5 – 5.8 mm ONSD > 5.5\text{--}5.8\text{ mm} ONS D > 5.5 – 5.8 mm (mean operational cutoff ≈ 5.5 mm \approx 5.5\text{ mm} ≈ 5.5 mm ) strongly predicts elevated intracranial pressure ( I C P > 20 mmHg ICP > 20\text{ mmHg} I CP > 20 mmHg ) with sensitivity and specificity exceeding 90 % 90\% 90% .

Dynamic Responsiveness: O N S D ONSD ONS D is highly dynamic; sheath diameter expands within minutes of acute ICP elevation and rapidly contracts following therapeutic osmotherapy ( 23.4 % NaCl 23.4\%\ \text{NaCl} 23.4% NaCl or mannitol) or surgical CSF drainage.

Confounders & False Positives: Optic nerve sheath meningioma, optic neuritis, retrobulbar hematoma, extensive ocular trauma, and congenital optic nerve drusen can falsely broaden the sheath in the absence of elevated ICP.

Ultrasound Modality Target Structure / Pathognomonic Sign Primary Neuro-ICU Indications Diagnostic Pitfalls / Limits

FOCUS McConnell's sign, D-shaped LV, apical ballooning Pulmonary embolism, Takotsubo, shock differentiation Hyperinflation artifact, chronic pulmonary HTN

Lung Ultrasound Lung point, Barcode sign, diffuse B-lines Pneumothorax, neurogenic pulmonary edema, consolidation Subcutaneous emphysema, pleural symphysis

ONSD Sheath diameter at 3 mm 3\text{ mm} 3 mm depth ( > 5.5 mm > 5.5\text{ mm} > 5.5 mm ) Non-invasive ICP screening, herniation surveillance Optic drusen, retrobulbar hematoma, ocular trauma