17.3 Vascular Access, Thoracic Echo, and Lung Ultrasound (02.J–L)

Procedures that keep the brain perfused

Quick Answer: In the neuro ICU, a central venous catheter (CVC) is a site-choice problem: internal jugular (IJ) is ultrasound-friendly but sits in the cerebral venous outflow; subclavian lowers some infection risk and raises pneumothorax risk; femoral spares the neck when ICP is high or a cervical collar is on, at the price of thrombosis and infection. Place arterial lines for beat-to-beat pressure and blood gas access, preferably ultrasound-guided. Lung ultrasound separates A-lines (aerated) from B-lines (interstitial) and uses the lung point for pneumothorax. Thoracic echo looks for tamponade, left ventricular (LV) and right ventricular (RV) failure, and inferior vena cava (IVC) plethora.

Independent OpenExamPrep teaching in this section covers vascular access, thoracic echocardiography, and lung ultrasound listed under Diagnostic studies and procedural skills in the ABPN Content Specifications. It is not an ultrasound-credentialing course and not an ABIM product. The examination wants which site in a high-ICP patient, which lung sign after a subclavian attempt, and which echo view explains shock after a wire went too far.

Central venous access: three veins, three neuro-ICU prices

A CVC is for vasopressors, hypertonic saline, central venous saturation sampling, and emergency resuscitation when peripheral veins fail. Ultrasound guidance is the default for IJ cannulation: it reduces carotid puncture and failed attempts. Identify the vein as compressible and non-pulsatile, watch the needle tip enter the lumen, confirm venous blood color and pressure if there is any doubt, and never dilate until you are sure you are not in the carotid. A manometry column or a transduced waveform is cheap insurance. After dilation, confirm tip position in the cavoatrial junction on radiograph or by ultrasound/ECG-tip methods used in your unit.

ICP and venous drainage. Cerebral venous blood leaves largely through the jugulars. A tight hematoma, a large-bore dialysis catheter, or IJ thrombosis can raise cerebral venous pressure and therefore ICP. When ICP is already a crisis, many neurointensivists prefer femoral or subclavian access rather than parking a stiff catheter in the only remaining jugular. That is a physiology choice, not a prohibition: an ultrasound-guided IJ is still appropriate when it is the safest emergency vein and the neck is not the problem. Do not place bilateral IJ catheters “because we might need two lumens” in a mass-lesion patient.

Coagulopathy. A compressible site (femoral, IJ) is safer than a non-compressible subclavian when platelets or INR are hostile. Reverse what you can before an elective line; an arterial bleed into the neck after carotid puncture is an airway emergency.

Dialysis catheters in the right IJ are standard for CRRT, but in high ICP they are the same jugular-occupancy problem. If the brain is the organ that will herniate this hour, femoral dialysis access is often the less bad option for a few days.

Arterial lines

Neuro ICU indications are labile blood-pressure targets (ischemic stroke after lytics, SAH, ICP/CPP titration), frequent ABGs, and unreliable non-invasive cuffs in shock or arrhythmia. Radial is first-line: collateral flow via the palmar arch, easy ultrasound, and a compressible site. The modified Allen test is traditional and insensitive; ultrasound of the ulnar artery and of flow after radial occlusion is more informative if you bother to check collaterals. Femoral arterial lines are larger, better in profound shock, and risk retroperitoneal hemorrhage. Brachial lines sit near the median nerve and have weaker collateral options — use them only when radial and femoral are impossible. Axillary and dorsalis pedis are reserve sites.

Transduce at the phlebostatic axis (mid-chest). For CPP you care about the same transducer height you use for MAP. Zero to atmosphere. A damped tracing is a clot, a bubble, or a wrist that is bent — not a reason to believe the cuff over a correctly leveled arterial line without troubleshooting.

Ultrasound habits that prevent catastrophe

• Dynamic needle-in-plane or out-of-plane visualization of the tip, not just the shaft.
• Distinguish artery from vein: pulsatility, non-compressibility, Doppler.
• After CVC placement, lung ultrasound for sliding before you wait on a chest radiograph if the patient desaturates.
• After radial cannulation, check distal color, Doppler, and pain — early ischemia means the catheter comes out.

Lung ultrasound: A-lines, B-lines, and the lung point

A high-frequency linear probe is excellent for sliding and pneumothorax at the anterior chest; a curvilinear or phased-array probe sees effusions and B-lines. Place the probe in sagittal intercostal spaces so you see two ribs and the pleural line between them.

Lung sliding is the to-and-fro shimmer of visceral against parietal pleura. On M-mode, sliding is the seashore sign (sandy lung under a still chest wall). Absent sliding produces the stratosphere / barcode sign. Absent sliding is not diagnostic of pneumothorax by itself: mainstem intubation, apnea (including during a BD/DNC apnea test), dense adhesions, and bullous disease also kill sliding.

A-lines are horizontal reverberation artifacts repeating below the pleural line at multiples of the probe-to-pleura distance. Prominent A-lines with preserved sliding mean aerated lung (normal, pulmonary embolism, or asthma/COPD). A-lines without sliding raise pneumothorax on the differential at that spot.

B-lines are vertical laser-like reverberations that erase A-lines, move with sliding, and reach the bottom of the screen. One or two in a space can be normal. Three or more B-lines in a rib space, in several spaces, define an interstitial syndrome: pulmonary edema, ARDS, pneumonia, or fibrosis. Neurogenic pulmonary edema after SAH or a seizure is a B-line diagnosis at the bedside while you wait for a chest radiograph.

Lung point is the moment the probe sees sliding (or B-lines) on one side of the image and absent sliding / barcode on the other, in the same rib space, moving with respiration. That transition is specific for pneumothorax. It maps the edge of the pleural air. A complete, large pneumothorax may have no lung point anteriorly because the lung is collapsed posteriorly — then you combine absent sliding, absent B-lines, A-lines, and the clinical story (subclavian attempt, positive-pressure ventilation, sudden desaturation).

Pleural effusion is anechoic (or complex) fluid above the diaphragm with a positive spine sign and, on M-mode, a sinusoid sign of the lung moving in fluid. Hemothorax looks similar but may be particulate. After a difficult subclavian line, look at both the anterior chest for pneumothorax and the flanks for new fluid.

The BLUE protocol mindset (Bedside Lung Ultrasound in Emergency) still helps shock and respiratory failure: venous compression for DVT, anterior A/B profiles, and posterolateral effusion. You do not need to recite every BLUE profile name on this examination, but you do need to know that A-profile plus DVT points toward embolism, and that an anterior B-profile is edema until proven otherwise.

Thoracic echo: tamponade, ventricles, IVC

A bedside transthoracic study in subxiphoid, parasternal long- and short-axis, and apical windows answers four shock questions: Is there pericardial tamponade? Is the LV empty, hyperdynamic, or severely hypokinetic (including neurogenic stunned myocardium / takotsubo after SAH)? Is the RV dilated and strained (massive PE, hypoxia, high PEEP)? Is the IVC plethoric or collapsing?

Tamponade is a clinical diagnosis that echo supports: pericardial effusion plus right atrial systolic collapse, right ventricular diastolic collapse, a plethoric IVC that does not collapse, and exaggerated inspiratory variation of mitral/tricuspid inflows. After CVC placement, a new effusion and obstructive shock is wire or dilator injury until proven otherwise — that is a crash thoracotomy / pericardial drain conversation, not a fluid bolus. Loculated postoperative hematoma can tamponade without a circumferential black stripe.

LV qualitative function is enough for most ICU decisions: squeeze is hyperdynamic in vasoplegia and hypovolemia, globally poor after anoxic injury or myocarditis, and regionally abnormal in infarction. After aneurysmal SAH, an apical ballooning pattern with modest troponin and no culprit lesion is neurocardiogenic, not an automatic trip to the catheterization laboratory — but ST elevation still needs an ECG-first approach.

RV dilation with septal flattening (D-sign) in systole suggests pressure overload. McConnell’s sign (apex-sparing RV free-wall hypokinesis) is a PE clue, not pathognomonic. Do not load a failing RV with liters of crystalloid because “the IVC looks small in one clip.”

IVC diameter and inspiratory collapse estimate right atrial pressure in spontaneously breathing patients. In positive-pressure ventilation, collapse is less trustworthy; a fat, non-varying IVC more reliably says high RA pressure (tamponade, RV failure, high PEEP, fluid overload) than a thin IVC proves “give 2 liters.” Integrate with the rest of the echo and the blood pressure.

Complications to name without hedging

Worked scenarios

A patient with a left hemispheric mass and ICP 32 mm Hg needs vasopressors. A right IJ dialysis catheter already occupies the remaining jugular. Place a femoral or subclavian CVC rather than a second IJ.

Desaturation 10 minutes after a left subclavian attempt: anterior left chest shows A-lines without sliding and a lung point — treat as pneumothorax. The same barcode during apnea testing without a lung point may simply be a disconnected ventilator.

PEA after a difficult wire: subxiphoid echo with a new pericardial stripe and RV diastolic collapse is tamponade from injury, not “anesthetic vasodilation.”

Exam traps

Bilateral IJ catheters in a high-ICP patient. Dilating a pulsatile vessel because the ultrasound picture was pretty. Calling absent sliding during BD/DNC apnea a pneumothorax without a lung point. Using EEG language in this procedures section. Treating a small collapsing IVC on high PEEP as a license for uncontrolled volume in a herniating patient. Forgetting that TCD in the previous section is a cerebral blood-flow ancillary test, while here TTE is a shock and tamponade tool.