Procedures & Invasives

A [[lumbar puncture]] (spinal tap) samples the cerebrospinal fluid (CSF) that bathes the brain and spinal cord. It is the definitive test for meningitis and encephalitis and a key tool for bleeding, inflammation, and some cancers that spread to the nervous system.

What the CSF tells you

The procedure is done with the patient curled to open the spaces between vertebrae, with a needle threaded into the fluid sac. It is safe when done carefully, but it is invasive and requires consent and attention to bleeding risk and pressure concerns.

Episode case: Euphoria - A rapid, fatal infection the team cannot stop

Prerequisite & related chapters:

• Tissue biopsy
• Rare infections

A biopsy removes a small piece of tissue for examination under a microscope. It is the most direct way to confirm many diagnoses - cancer, autoimmune inflammation, infection, or deposition diseases - because it looks at the disease itself rather than its chemical footprints.

Common biopsy approaches

• Bone marrow biopsy - for blood disorders, leukemia, lymphoma
• Lymph node biopsy - for lymphoma and infection
• Kidney biopsy - for glomerular disease and lupus nephritis
• Skin biopsy - for vasculitis, sarcoidosis, and rashes
• Lung or liver biopsy - for infiltrative and inflammatory disease

On the show, the biopsy is the moment of truth - the test that finally names the disease after weeks of guessing. It is also a point of conflict, because it is invasive and patients often resist it. The tension between a definitive test and its risk is a recurring theme.

Prerequisite & related chapters:

• Lumbar puncture
• Amyloidosis

Plasmapheresis (plasma exchange) removes a patient's blood, separates the plasma - the liquid part carrying antibodies and proteins - and replaces it with donor plasma or a substitute. It rapidly clears harmful antibodies or proteins driving disease.

When it is used

• Autoimmune conditions where antibodies attack nerves or organs
• Certain severe antibody-mediated diseases (myasthenia gravis crisis, Guillain-Barre)
• Some vasculitis and blood-vessel inflammation
• Conditions where abnormal proteins clog the blood (hyperviscosity)

Plasmapheresis is a treatment, not a cure: it removes the offending substance but does not stop the body from making more. It is often paired with immunosuppressants to treat the underlying production. On the show, it appears in dramatic rescue scenarios where a patient is deteriorating rapidly.

Prerequisite & related chapters:

• Dialysis
• Immunosuppressants

Bronchoscopy passes a thin, flexible scope through the mouth or nose into the airways. It lets clinicians see the trachea and bronchi directly, take samples (biopsy, brushings, washings), and clear secretions or foreign material.

What it is used for

• Investigating persistent cough, hemoptysis (coughing blood), or an abnormal chest finding
• Sampling lung tissue or fluid for infection, inflammation, or cancer
• Removing a foreign body or clearing a blocked airway
• Diagnosing interstitial lung disease and sarcoidosis

On the show, bronchoscopy is often the test that finally reaches a diagnosis hiding in the lung - a granuloma, an unusual infection, a tumor. It is invasive but generally well tolerated with sedation and topical anesthesia.

Prerequisite & related chapters:

• Tissue biopsy
• Sarcoidosis

Cardiac catheterization threads a thin tube through a blood vessel up to the heart. It measures pressures inside the heart chambers, images the coronary arteries (angiography), and can treat blockages by inflating a balloon or placing a stent.

Diagnostic and therapeutic

• Coronary angiography - finds narrowed or blocked arteries
• Pressure measurements - assess heart function and valve problems
• Angioplasty and stenting - reopen a blocked vessel during a heart attack
• Biopsy of heart muscle in suspected cardiomyopathy

The dramatic heart-attack cath - opening a blocked artery in minutes - is a real emergency procedure. On the show, cardiac catheterization is a recurring tool for both diagnosis (unexplained heart failure) and rescue (a patient with a massive clot).

Prerequisite & related chapters:

• Thrombolytics
• Telemetry

Intubation places a tube through the mouth into the trachea to secure the airway and connect the patient to a ventilator. It is an emergency, life-saving procedure when a patient cannot protect or maintain their own airway or breathing.

When intubation is needed

• Respiratory failure - the patient cannot oxygenate or ventilate
• Loss of airway protection (e.g., severe sedation, coma, stroke)
• Severe trauma or swelling threatening the airway
• To allow deep sedation and support during critical illness

Intubation is a high-stakes skill: the clinician must place the tube correctly (in the trachea, not the esophagus) and confirm it, then manage the ventilator. On the show, it is a frequent dramatic beat - the moment a patient 'crashes' and the team rushes to secure the airway.

Prerequisite & related chapters:

• Cardiac catheterization
• Benzodiazepines

Dialysis performs the filtering work of the kidneys when they fail: removing waste products, balancing electrolytes, and removing excess fluid. It is used in acute kidney failure (a bridge while the kidneys recover) and chronic kidney failure (a long-term treatment).

Two main forms

On the show, dialysis appears when a patient's kidneys fail from a disease process - sometimes the very disease the team is trying to diagnose. It is a support measure that keeps the patient alive while the underlying cause is found and treated.

Prerequisite & related chapters:

• Plasmapheresis
• BMP & electrolytes