When to intubate in GCS?

GCS ≤ 8 requires intubation for airway protection. The patient cannot protect their own airway at this level of consciousness. Motor score is the most prognostically important component.

What is the best initial fluid for sepsis resuscitation?

Lactated Ringer's (LR) is the preferred resuscitation fluid. The SMART trial (2018) showed balanced crystalloids reduced death, new renal failure, and persistent renal dysfunction compared to normal saline.

When to start vasopressors in septic shock?

Start norepinephrine (first-line vasopressor) if MAP remains < 65 mmHg after initial 30 mL/kg crystalloid resuscitation, or earlier if patient is profoundly hypotensive. Do not delay pressors to complete full fluid resuscitation.

Why can serum uric acid be normal during acute gout?

During acute inflammation, IL-6 increases renal urate excretion and redistributes urate from plasma to tissues. Up to 40% of acute gout flares have normal serum uric acid. Joint aspiration with polarized microscopy is needed for definitive diagnosis.

How do you distinguish lupus flare from infection in SLE?

Key clues: CRP is low/normal in flare but elevated in infection. Complement (C3/C4) drops in flare but is normal/elevated in infection. Procalcitonin is elevated in bacterial infection but normal in flare. Anti-dsDNA rises in flare, stable in infection.

What is the difference between DKA and HHS?

DKA features acidosis (pH 600), hyperosmolality (> 320), and minimal ketosis -typically in Type 2 DM. DKA requires insulin drip; HHS requires aggressive fluid resuscitation first.

When to give tPA in acute ischemic stroke?

IV alteplase (tPA) can be given within 4.5 hours of last known well time in eligible patients. CT head must rule out hemorrhage first. For large vessel occlusion, mechanical thrombectomy can be performed up to 24 hours with favorable imaging.

What antibiotics for community-acquired pneumonia?

Inpatient non-ICU: ceftriaxone + azithromycin. ICU: ceftriaxone + azithromycin (add vancomycin if MRSA risk). Outpatient healthy: amoxicillin. Outpatient with comorbidities: augmentin + azithromycin or respiratory fluoroquinolone. Duration: 5 days if clinically stable for 48 hours.

How to interpret iron studies?

Iron deficiency: low ferritin (< 30), high TIBC, low iron, low transferrin saturation (< 20%). Anemia of chronic disease: normal/high ferritin (acute phase reactant), low TIBC, low iron. A ferritin of 50-100 in an inflamed patient may still represent iron deficiency.

What is the correction rate for hyponatremia?

Correct sodium no more than 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome (ODS). For symptomatic severe hyponatremia with seizures, give 3% hypertonic saline 100-150 mL bolus over 10-20 minutes. If overcorrected, use D5W + DDAVP rescue protocol.

When to start antibiotics in meningitis?

Within 30-60 minutes. Do NOT delay antibiotics for LP or CT. Draw blood cultures, start empiric antibiotics (vancomycin + ceftriaxone ± ampicillin if > 50 or immunocompromised), then perform LP when possible. Dexamethasone should be given before or with the first antibiotic dose.

DOACs vs warfarin in antiphospholipid syndrome?

DOACs are contraindicated in APS. The TRAPS trial (2018) showed rivaroxaban was inferior to warfarin with more thrombotic events in triple-positive APS patients. Warfarin with INR target 2-3 is the standard for APS, indefinitely.

How to manage scleroderma renal crisis?

ACE inhibitors (captopril) are life-saving -start immediately and titrate aggressively. Do NOT hold for rising creatinine. Steroids > 15 mg prednisone per day precipitate scleroderma renal crisis. ARBs are NOT a substitute -evidence is only for ACEi.

What are the 4 pillars of heart failure treatment?

Guideline-directed medical therapy (GDMT) for HFrEF: (1) ARNI or ACEi/ARB, (2) beta-blocker (carvedilol, metoprolol succinate, or bisoprolol), (3) MRA (spironolactone or eplerenone), (4) SGLT2 inhibitor (dapagliflozin or empagliflozin). All four should be initiated and titrated to target doses.

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EndocrinologyCommon

SIADH & Diabetes Insipidus

Two opposite disorders of water balance. SIADH: too much ADH → water retention → dilutional hyponatremia. DI: too little ADH (or resistance) → massive free water loss → hypernatremia. Correct slowly -osmotic demyelination kills.

💧 SIADH

Diagnostic Criteria -ALL Must Be Present

Serum Na⁺ < 135 mEq/L (hyponatremia)
Serum osmolality < 275 mOsm/kg (hypo-osmolar)
Urine osmolality > 100 mOsm/kg (inappropriately concentrated urine)
Urine sodium > 40 mEq/L (kidneys wasting sodium)
Euvolemic on clinical exam (no edema, no orthostasis)
Normal thyroid and adrenal function (must rule out hypothyroidism and cortisol deficiency -both cause hyponatremia)

SIADH is a diagnosis of exclusion. You must rule out hypothyroidism (check TSH) and adrenal insufficiency (check AM cortisol) before diagnosing SIADH. Both cause hyponatremia and both are treatable with specific therapy.

Asymptomatic / chronic (Na 120–134)Fluid restriction (800–1000 mL/day). Stop offending drugs. Treat underlying cause. Salt tabs ± urea if refractory.≤ 8 mEq/L per 24h (some use ≤ 10). Chronic hyponatremia → brain has adapted → rapid correction → ODS. Symptomatic (seizures, coma, severe AMS)3% hypertonic saline 100–150 mL IV bolus over 10–20 min. May repeat × 2 if no improvement. ICU admission.Immediate goal: raise Na by 4–6 mEq/L in first 6h to stop symptoms. Then ≤ 8 mEq/L total in 24h. RefractoryTolvaptan (Samsca) 15 mg PO daily -vasopressin V2 receptor antagonist ("vaptan"). Or oral urea 15–30g daily. SALT-1/SALT-2, Schrier 2006Tolvaptan: do NOT use with hypertonic saline (risk of overcorrection). Monitor Na q6h. Only use in hospital.

Verbalis Expert Panel, 2013 Osmotic Demyelination Syndrome (ODS): if Na corrects too fast (> 8–10 mEq/L in 24h), myelin in the central pons is destroyed → "locked-in syndrome" (awake but unable to move or speak). Irreversible. Risk factors: chronic hyponatremia, alcoholism, malnutrition, hypokalemia, liver disease. If overcorrecting → give D5W + desmopressin (DDAVP) 2 mcg IV q8h to re-lower Na.

🔥 Diabetes Insipidus

Types

Type	Mechanism	Causes	Urine Osm after DDAVP
Central DI	↓ ADH production (posterior pituitary)	Neurosurgery (#1), pituitary tumors, head trauma, brain death, Sheehan syndrome, infiltrative (sarcoid, histiocytosis)	↑↑ (concentrates > 50%) -kidneys respond to exogenous ADH
Nephrogenic DI	Kidney resistance to ADH	Lithium (#1 drug cause), hypercalcemia, hypokalemia, chronic kidney disease, demeclocycline	No change -kidneys don't respond

Presentation & Diagnosis

Polyuria (> 3 L/day of dilute urine -Uosm < 300)
Polydipsia (intense thirst if alert)
Hypernatremia (if unable to access water -ICU patients, post-neurosurgery, AMS)
Urine osmolality < 300 with serum osmolality > 290 → inappropriate dilute urine
Water deprivation test → distinguishes central vs nephrogenic (give DDAVP and measure urine osm response)

Treatment

Type	Treatment	Notes
Central DI	Desmopressin (DDAVP) 1–2 mcg IV/SC q12h or 10–20 mcg intranasal BID	Replaces missing ADH. Monitor Na closely -risk of hyponatremia with overdose. Titrate to UOP.
Nephrogenic DI	Remove offending agent (lithium). Low-sodium diet + thiazide diuretic (paradoxically ↓ urine output). Amiloride for lithium-induced NDI.	DDAVP does NOT work (kidneys are resistant). Thiazide paradox: thiazides cause mild volume depletion → ↑ proximal reabsorption → less water delivered to collecting duct → less dilute urine.
Acute hypernatremia (from DI)	D5W or 0.45% NS IV. Free water deficit = TBW × (Na/140 − 1).	Correct ≤ 10 mEq/L per 24h if chronic. If acute (< 48h) → can correct faster. Replace ongoing free water losses (UOP) in addition to deficit.

📋 On Rounds

A patient's Na corrected from 112 to 124 in 18 hours. What do you do?

That's a 12 mEq/L correction in 18h -too fast. The safe limit is ≤ 8–10 mEq/L in 24h. Immediate steps: (1) D5W infusion (free water to re-lower Na), (2) DDAVP 2 mcg IV q8h (replaces ADH → kidneys retain free water → Na drops back), (3) target Na back to no more than 8 mEq/L above the starting value for the 24h period. The goal is to "re-lower" the sodium to a safe correction trajectory.

Why do thiazides paradoxically help nephrogenic DI?

Counterintuitive but elegant: thiazides block NaCl reabsorption in the distal convoluted tubule → mild sodium and volume depletion → the body compensates by increasing proximal tubule reabsorption of sodium AND water → less water is delivered to the ADH-insensitive collecting duct → less dilute urine produced → lower urine volume. The effect reduces urine output by ~30–50%.

How does tolvaptan work and why must you start it inpatient?

Tolvaptan is a V2 receptor antagonist -blocks ADH (vasopressin) at the collecting duct → induces a free water diuresis (aquaresis) without sodium loss. Result: concentrated urine, dilute plasma → sodium rises. Must be started inpatient because the sodium correction can be unpredictable and rapid → risk of overcorrection → osmotic demyelination syndrome (ODS). Monitoring protocol: Na checked at 4-6h, 8-12h, and 24h after first dose.

What are the criteria for diagnosing SIADH?

Essential criteria (all must be met): (1) Serum osm < 275 mOsm/kg (hypoosmolar), (2) Urine osm > 100 mOsm/kg (inappropriately concentrated -the kidneys SHOULD be making dilute urine in hypo-osmolar state), (3) Euvolemic (no edema, no JVD, no orthostasis), (4) Urine Na > 40 mEq/L (kidneys excreting sodium inappropriately)

A patient with Na 118 and seizures -what do you give and how fast do you correct?

3% hypertonic saline 100-150 mL bolus over 10 min. Can repeat ×1. Target 4-6 mEq/L rise in the first 4-6h. Do NOT exceed 8 mEq/24h (6 if high-risk). Overcorrection → osmotic demyelination syndrome.

What is the most dangerous time for osmotic demyelination syndrome (ODS)?

ODS presents 2-6 days after overcorrection with dysarthria, dysphagia, quadriparesis, and locked-in syndrome. Risk factors: chronic hyponatremia > 48h, alcoholism, malnutrition, liver disease, hypokalemia.

When should you give DDAVP in hyponatremia management?

As an ODS rescue -if Na is correcting too fast (> 8 mEq/24h or > 6 in high-risk). Give DDAVP 2 mcg IV q8h + D5W to re-lower sodium back to the safe correction rate.

Why must you check TSH and cortisol before diagnosing SIADH?

Both hypothyroidism and adrenal insufficiency cause hyponatremia and mimic SIADH (euvolemic, concentrated urine). They are treatable and MUST be excluded. SIADH is a diagnosis of exclusion.

Clinical Examples

📋 Case 1, SSRI-Induced SIADH

Patient: 72-year-old woman started on escitalopram 3 weeks ago for depression. Presents with fatigue, nausea, mild confusion. Na 118, serum osm 248, urine osm 520, UNa 58. Euvolemic. TSH and AM cortisol normal.

Key findings: Classic SSRI-induced SIADH. All diagnostic criteria met: hypo-osmolar, inappropriately concentrated urine, euvolemic, UNa > 40, normal thyroid/adrenal function.

Management:

Hold escitalopram (offending agent)
Fluid restriction < 1 L/day
Na q4-6h (symptomatic with confusion)
If Na not improving: salt tabs 1g TID
Correction rate ≤ 8 mEq/L per 24h (high risk: elderly)

Teaching point: SSRIs are the #1 drug cause of SIADH. Always check Na 2-4 weeks after starting an SSRI in elderly patients. Leth-Moller et al., 2016

📋 Case 2, Post-Neurosurgical Central DI

Patient: 38-year-old man, POD 1 from transsphenoidal pituitary adenoma resection. UOP 650 mL/hr x 4 hours. Clear, dilute urine. Na 151 (was 140 pre-op), serum osm 308, urine osm 78.

Key findings: Post-surgical central DI. Massive polyuria with inappropriately dilute urine and rising Na. Must watch for triphasic response.

Management:

DDAVP 1 mcg IV q12h
D5W to replace free water deficit + match ongoing losses
Na q4h, strict I&Os, hourly UOP
If UOP drops and Na falls on days 5-10: STOP DDAVP immediately (SIADH phase)

Teaching point: The triphasic response (DI, then SIADH, then permanent DI) occurs in ~25% of pituitary surgery patients. Continuing DDAVP into the SIADH phase causes fatal hyponatremia.

📋 Case 3, Overcorrection Rescue

Patient: 65-year-old man with chronic hyponatremia (Na 108) from SCLC-associated SIADH. After 18 hours of 3% saline and fluid restriction, Na corrected to 122 (14 mEq/L rise).

Key findings: Overcorrection: 14 mEq/L in 18h exceeds the safe limit of 8 mEq/L per 24h. High risk for ODS: chronic, severe hyponatremia, malignancy.

Management:

STOP hypertonic saline immediately
DDAVP 2 mcg IV q8h (re-lower Na)
D5W infusion to bring Na back down
Target: Na no more than 8 mEq/L above starting value for 24h period (goal Na ≤ 116)
Na q2h until trending downward

Teaching point: ODS rescue (DDAVP + D5W) should be initiated immediately when overcorrection is detected. ODS presents 2-6 days later and is irreversible. Verbalis Expert Panel, 2013

📣 Sample Presentation

One-Liner

"Mr. Foster is a 68-year-old started on sertraline 3 weeks ago presenting with Na⁺ 122, serum osm 258, urine osm 480, UNa 52, euvolemic. TSH and cortisol normal. SIADH from SSRI."

Monitoring Parameters -Cellulitis & Skin Infections

Parameter	Frequency	Target / Action
Vitals	q4h floor, q1–2h ICU	HR, BP, RR, SpO₂, Temp -notify for significant deviations
Labs (BMP, CBC)	Daily AM or as indicated	Trend Cr, K⁺, WBC, Hgb -adjust treatment based on trajectory
Disease-specific markers	Per clinical context	See Overview and Management tabs for condition-specific targets
I&Os	Strict if volume-sensitive	UOP ≥ 0.5 mL/kg/hr. Net fluid balance guides diuresis or resuscitation.
Telemetry	Continuous if indicated	Arrhythmia detection. Discontinue when no longer indicated (reduces alarm fatigue).
Clinical response	Each assessment	Symptom improvement, functional status, appetite, mental status -the exam matters more than labs

Don't just order labs -act on them. Every lab should have a clear clinical question. If you wouldn't change management based on the result, don't order it.

Key Points to Cover on Rounds

SIADH -euvolemic hypoosmolar hyponatremia with inappropriately concentrated urine and high UNa. Cause: sertraline (SSRIs are the most common drug cause of SIADH). Asymptomatic (no seizure, no AMS). Treatment: fluid restriction <1L/day started. Sertraline held -discuss alternative antidepressant with psychiatry. Na trending 122→124→126 over 36h (rate 3 mEq/24h -safe, goal ≤8 per 24h). Plan: if refractory to fluid restriction → salt tabs 1g TID. If still refractory → tolvaptan (inpatient only, check Na q6h). ODS rescue protocol available if overcorrected (D5W + DDAVP).

🧪 Workup

See the Overview and Management tabs for topic-specific diagnostic evaluation.

⚡ Management

Management -SIADH & Diabetes Insipidus

See the Management section above for the full treatment algorithm with evidence-based recommendations and trial citations.

💊 Medications

Key Medications -Cellulitis & Skin Infections

Refer to the Management tab for the full treatment algorithm with drug choices, dosing, and contraindications. Refer to the Antibiotic Guide if infectious etiology. Always check renal dosing and drug interactions.

First-line agents: See Management tab for evidence-based recommendations with trial citations
Renal adjustment: Check CrCl -see Antibiotic Guide renal dosing tab or Calculators for CrCl
Drug interactions: See Drug Interactions reference
Allergies: Always verify before prescribing. Document reaction type (rash vs anaphylaxis)

⚡ Summary

Summary

Diagnostic Criteria

Serum osm < 275 + urine osm > 100 + euvolemic + UNa > 40 + normal thyroid/adrenal function + no diuretics. Diagnosis of exclusion.

Common Causes

SSRIs (#1 drug cause), carbamazepine, cyclophosphamide, vincristine. CNS: stroke, SAH, meningitis. Pulmonary: pneumonia, TB. Malignancy: SCLC.

Treatment

Fluid restriction < 1L/day (first-line) → salt tabs → tolvaptan (V2 antagonist, inpatient only, check Na q6h). Treat underlying cause.

Tolvaptan Rules

Start inpatient. No fluid restriction while on it. Check Na at 4-6h, 8-12h, 24h. Hold if correcting > 8 mEq/24h. Hepatotoxicity risk (max 30 days).

Correction Rate

≤ 8 mEq/L per 24h. High-risk for ODS: Na < 105, chronic, alcoholism, malnutrition, liver disease. In high-risk → ≤ 6 mEq/24h.

ODS Rescue

D5W + DDAVP 2 mcg IV q8h if overcorrecting. Act immediately. ODS = devastating irreversible pontine demyelination.