Clinical Diagnostics & Treatment Protocols

Clinical DX requires systematic approach combining Hx, PE, and diagnostic workup. The DDx process begins w/ chief complaint (CC) and evolves through pattern recognition and probabilistic reasoning.

## History Taking Framework

OPQRST for pain assessment: Onset (sudden vs gradual), Provocation/Palliation, Quality (sharp/dull/burning), Region/Radiation, Severity (1-10 NRS), Timing (constant/intermittent). Always assess ROS across major organ systems. SAMPLE for emergency: Signs/Sx, Allergies, Medications, PMHx, Last meal, Events preceding.

Red flags requiring immediate eval: sudden severe HA w/ neck stiffness (r/o SAH), chest pain w/ diaphoresis and dyspnea (r/o ACS), acute abd pain w/ rigidity (r/o peritonitis), unilateral leg swelling w/ pain (r/o DVT/PE), new focal neuro deficits (r/o CVA).

## Physical Examination Systematic Approach

VS interpretation: HR normal 60-100 bpm, tachycardia >100 suggests hypovolemia/sepsis/pain/anxiety. BP classification per ACC/AHA: normal <120/80, elevated 120-129/<80, HTN Stage 1 130-139/80-89, Stage 2 >=140/>=90. Orthostatic hypotension: SBP drop >=20 or DBP drop >=10 within 3min of standing suggests volume depletion.

Cardiac exam: Auscultate 4 areas — aortic (R 2nd ICS), pulmonic (L 2nd ICS), tricuspid (L lower sternal border), mitral (apex/5th ICS MCL). S3 gallop suggests volume overload/CHF. S4 suggests decreased ventricular compliance/HTN. New murmur w/ fever → r/o endocarditis, obtain BC x2 from separate sites.

Pulmonary: Percussion — dullness suggests consolidation/effusion, hyperresonance suggests PTX/emphysema. Auscultation — crackles (PNA/CHF), wheezes (asthma/COPD/CHF), absent breath sounds (PTX/massive effusion). Tactile fremitus increased w/ consolidation, decreased w/ effusion/PTX.

Abdominal: Inspect, auscultate, percuss, palpate (in that order). RLQ tenderness w/ rebound → McBurney's point → appendicitis. RUQ tenderness w/ Murphy's sign → cholecystitis. Epigastric pain radiating to back → pancreatitis (check lipase, >3x ULN diagnostic). Peritoneal signs: involuntary guarding, rigidity, rebound tenderness → surgical consult.

## Laboratory Interpretation

CBC: WBC >11k suggests infection/inflammation, left shift (>10% bands) suggests bacterial. WBC <4k w/ fever → sepsis concern. Hgb <7 in stable pt → consider transfusion (TRICC trial threshold). Plt <50k → bleeding risk, <10k → spontaneous hemorrhage risk.

BMP: Na 135-145 mEq/L. Hyponatremia: acute (<48h) vs chronic, hypo/eu/hypervolemic. Correct Na for glucose: add 1.6 mEq for each 100 mg/dL glucose >100. K 3.5-5.0 mEq/L. Hyperkalemia >6.5 or w/ ECG changes (peaked T, wide QRS) → emergent tx: calcium gluconate (membrane stabilization), insulin+glucose, albuterol, kayexalate, consider HD.

Creatinine/BUN: Cr >1.2 may indicate AKI or CKD. BUN:Cr ratio >20:1 suggests prerenal etiology. RIFLE/KDIGO criteria for AKI staging. GFR estimation via CKD-EPI equation preferred over MDRD.

LFTs: AST/ALT elevation pattern — hepatocellular (ALT>AST, viral/drug hepatitis) vs cholestatic (ALP/GGT elevated, obstruction). AST:ALT >2:1 w/ GGT elevation → alcoholic liver disease. Alk phos isolated elevation → bone origin vs hepatic (confirm w/ GGT).

Cardiac markers: Troponin I/T — high-sensitivity assays detect earlier. Serial measurements q3-6h. Rising pattern confirms AMI. BNP >400 pg/mL strongly suggests CHF; <100 helps r/o CHF in dyspnea workup.

## Imaging Decision Framework

CXR: First-line for dyspnea, cough, chest pain, fever. Look for: cardiomegaly (CTR >0.5), pleural effusion (blunting of costophrenic angles), PNA (consolidation/air bronchograms), PTX (absent lung markings, visceral pleural line), widened mediastinum (r/o aortic dissection → CTA).

CT: Head CT w/o contrast for acute CVA/hemorrhage — get within 25min of arrival for stroke alert. CT abd/pelvis w/ contrast for acute abd pain when DX unclear. CTA chest for PE when Wells score intermediate/high + elevated D-dimer. CTPA sensitivity >95% for PE.

US: FAST exam in trauma (4 views: RUQ, LUQ, suprapubic, subxiphoid). Bedside echo for tamponade (pericardial effusion + RV diastolic collapse). RUQ US first-line for biliary disease. DVT: compression US of proximal veins, sensitivity >95%.

## Common Treatment Protocols

ACS management: MONA is outdated mnemonic but components valid — Morphine (only if refractory pain), O2 (only if SpO2 <94%), Nitroglycerin (SL q5min x3, hold if SBP <90 or RV infarct), Aspirin 325mg chewed immediately. Dual antiplatelet: ASA + P2Y12 inhibitor (ticagrelor preferred over clopidogrel per PLATO). Heparin (UFH or enoxaparin). STEMI → cath lab within 90min door-to-balloon.

Sepsis (Surviving Sepsis Campaign): Hour-1 bundle — lactate level, BC before ABx, broad-spectrum ABx within 1hr, 30mL/kg crystalloid for hypotension or lactate >=4, vasopressors (norepi first-line) if MAP <65 after fluids. qSOFA bedside: altered mentation, SBP <=100, RR >=22 (>=2 = high risk). Reassess volume status, consider CVP or POCUS IVC assessment.

DKA: IVF (NS initially, then 0.45% when Na normalizes), insulin drip (0.1-0.14 U/kg/hr, DO NOT bolus per newer guidelines), K replacement (hold insulin if K <3.3, replace first), monitor AG q2-4h, transition to SQ insulin when AG closes AND pt eating AND glucose <200. Bridge overlap: give SQ basal 2hrs before stopping drip.

COPD exacerbation: SABA (albuterol) + SAMA (ipratropium) nebs, systemic corticosteroids (prednisone 40mg x5d, no taper needed per REDUCE trial), ABx if purulent sputum or requiring mechanical ventilation (azithromycin or doxycycline). BiPAP for respiratory acidosis (pH <7.35, PaCO2 >45). Intubation if BiPAP fails or pt obtunded.

## Medication Safety

Always check: drug allergies (true allergy vs intolerance), renal/hepatic dosing adjustments, drug interactions (CYP450 — 2D6, 3A4 most clinically relevant), pregnancy category, QTc prolongation risk (azithromycin, fluoroquinolones, ondansetron, antipsychotics). High-alert medications requiring double-check: insulin, anticoagulants, opioids, chemotherapy, concentrated electrolytes.

Anticoagulation: Warfarin target INR 2-3 for Afib/DVT, 2.5-3.5 for mechanical valve. DOACs preferred for nonvalvular Afib — apixaban (ARISTOTLE), rivaroxaban (ROCKET-AF). Bridging: generally NOT recommended for Afib pts on warfarin undergoing procedures (BRIDGE trial). Reversal: warfarin → vitamin K + 4-factor PCC; dabigatran → idarucizumab; apixaban/rivaroxaban → andexanet alfa.

## Disposition Decision Making

Admit criteria: hemodynamic instability, acute organ dysfunction, need for IV medications/monitoring not available outpatient, inability to maintain PO intake, unsafe social situation, high-risk DDx requiring serial exams/labs. ICU criteria: vasopressor requirement, mechanical ventilation, active hemorrhage w/ hemodynamic compromise, acute MI w/ complications, status epilepticus, DKA w/ severe acidosis (pH <7.1).

Discharge safety: ensure reliable follow-up within 24-72h for concerning presentations, clear return precautions in pt's language, medication reconciliation, confirm understanding w/ teach-back method.