Esmolol - STAT (Emergency) Usage

Drug Class & Mechanism

• Morgan and Mikhail's Clinical Anesthesiology, 7e, p.456
• Katzung's Basic and Clinical Pharmacology, 16e, p.258

Pharmacokinetics (Why It's Ideal for STAT Use)

• Goodman & Gilman's Pharmacological Basis of Therapeutics, p.707
• Brenner and Rector's The Kidney, p. (Table 49.39)

STAT Indications

1. Rate control in atrial fibrillation/flutter - rapidly conducted AF with fast ventricular response
2. Supraventricular tachycardia (SVT) - when patient is not hypotensive
3. Perioperative tachycardia and hypertension - response to laryngoscopy, intubation, surgical stimulation, emergence
4. Hypertensive emergencies - especially post-operative hypertension, hypertension with coronary insufficiency
5. Sympathetically mediated tachycardia during ECT (electroconvulsive therapy) - blunts response without significantly affecting seizure duration
6. Myocardial ischemia in acutely ill patients - controls rate and reduces O2 demand
7. Arrhythmias associated with thyrotoxicosis - useful for sympatholysis
8. Aortic dissection - rate and BP control (in combination)

• Barash Clinical Anesthesia, 9e, p.987
• Katzung's Basic and Clinical Pharmacology, p.258

Dosing Protocol (STAT/IV)

Bolus (short-term, e.g., intubation response)

• 0.2-0.5 mg/kg IV bolus - immediate effect for brief stimuli (laryngoscopy, etc.)
• Morgan & Mikhail, p.456

Loading + Infusion (sustained rate/BP control)

• 500 mcg/kg (0.5 mg/kg) IV over 1 minute

• Start at 50 mcg/kg/min

• Repeat loading dose (500 mcg/kg over 1 min)
• Increase infusion by 50 mcg/kg/min increments every 5 min
• Maximum infusion: 200-300 mcg/kg/min

Brenner & Rector cites a loading dose of 250-500 mcg/kg/min × 1 min, then 50-100 mcg/kg/min maintenance, up to a maximum of 300 mcg/kg/min.

Preparation

• Available as multidose vials: 10 mg/mL (for bolus)
• Ampules for infusion: 2.5 g in 10 mL - must be diluted to 10 mg/mL before use
• Extravasation can cause serious local irritation and skin necrosis - use a central or large peripheral line when possible
• Morgan & Mikhail, p.457; Brenner & Rector

Contraindications / Cautions

• Sinus bradycardia
• Heart block > 1st degree (2nd or 3rd degree AV block)
• Cardiogenic shock
• Uncompensated heart failure / low EF
• Renal impairment - use with caution (de-esterified metabolite is renally eliminated)
• At high doses: β2 blockade can cause bronchospasm - use cautiously in asthma/COPD

Key Clinical Pearl

• Goodman & Gilman's, p.707
• Katzung's, p.258

Clinical Assessment & Treatment

First: Understand the Clinical Picture

The troponin being negative but CK-MB elevated is a red flag - CK-MB rises earlier (3-8 hrs) than high-sensitivity troponin in some assays. This patient cannot be discharged without serial troponins and repeat ECG. The picture is most consistent with NSTE-ACS (Unstable Angina vs NSTEMI).

• Goldman-Cecil Medicine, p. (NSTE-ACS chapter)

Immediate MONA + ACS Protocol

Step 1: Initial Stabilization

• IV access, continuous cardiac monitoring, pulse oximetry
• 12-lead ECG immediately (and repeat every 30 min if symptoms persist)
• Serial troponin at 0, 3, and 6 hours
• Chest X-ray (rule out aortic dissection, pulmonary edema)
• O2 only if SpO2 <94% (avoid routine supplemental O2 in normoxic ACS)

"Individuals with chest pain or shortness of breath generally require a chest radiograph, electrocardiogram, and cardiac biomarker (e.g., troponin, natriuretic peptide) measurement." - Rosen's Emergency Medicine

Treatment (Hypertension WITH Chest Pain + Elevated CK-MB)

1. Antiplatelet Therapy

• Aspirin 300 mg (loading) orally stat - chewed, not swallowed whole
• P2Y12 inhibitor loading (if NSTEMI confirmed or high suspicion):
  • Clopidogrel 300-600 mg PO, or
  • Ticagrelor 180 mg PO (preferred per current guidelines)

2. Anti-ischemic / BP Lowering (Dual Purpose)

• Reduces HR and BP (reduces myocardial O2 demand)
• Has anti-anginal and anti-arrhythmic effects
• Reduces infarct size in ACS

Avoid beta-blockers if: signs of acute heart failure, HR <60, SBP <100, AV block, or severe bronchospasm

• Sublingual NTG 0.4 mg - repeat every 5 min x3 if chest pain persists
• If pain or BP still uncontrolled: IV nitroglycerin infusion 5-100 mcg/min, titrate to pain relief and BP response
• Contraindication: suspected RV infarct, or if patient took PDE-5 inhibitor within 24-48 hrs

"Intravenous nitroglycerin may be the drug of choice in the treatment of patients with moderate hypertension associated with coronary ischemia because it provides collateral coronary vasodilation." - Brenner & Rector's The Kidney

3. Anticoagulation

• Unfractionated heparin (UFH): 60 U/kg IV bolus (max 4000 U) then 12 U/kg/hr infusion, titrate to aPTT 50-70 seconds
• OR Enoxaparin 1 mg/kg SC q12h (if not going for early invasive strategy)
• Reduces thrombus propagation on the ruptured plaque

4. Statin

• High-intensity statin - Atorvastatin 80 mg or Rosuvastatin 40 mg PO stat
• Pleiotropic anti-inflammatory effects and plaque stabilization

5. Blood Pressure Target

• BP 160/80 does NOT constitute a hypertensive emergency in isolation (true hypertensive emergencies typically ≥180/110 with target organ damage)
• However, with chest pain/ACS: target BP <140/90 initially, avoid over-aggressive reduction
• Do NOT reduce MAP by more than 20-25% in the first hour to avoid cerebral hypoperfusion

"The long-standing approach to acute antihypertensive therapy has targeted a maximal reduction in MAP of 20% to 25% within the first hour and a goal BP of 160/100 mmHg by 2-6 hours." - Rosen's Emergency Medicine, p.1146

What to Avoid

Important: Serial Troponin Strategy

1. Early NSTEMI (troponin hasn't risen yet - sample was too early)
2. Non-cardiac CK-MB source being coincidental
3. Unstable angina with CK-MB rise from minor myonecrosis

• Goldman-Cecil Medicine - NSTE-ACS chapter
• Rosen's Emergency Medicine, p.1145-1146

Summary Algorithm

BP 160/80 + Chest pain + Trop(-) + CK-MB↑
         ↓
ECG + Serial Troponin + CXR
         ↓
ASA 300mg + Beta-blocker or NTG (sublingual → IV)
         ↓
Anticoagulate (Heparin/Enoxaparin)
         ↓
Statin (high intensity)
         ↓
Monitor: repeat ECG, repeat troponin @ 3h, 6h
         ↓
If Troponin rises → NSTEMI → Cardiology consult
                             Early invasive strategy
If Troponin stays negative → Unstable Angina
                             Risk stratify, stress test

Clinical bottom line: BP of 160/80 with chest pain and elevated CK-MB should be managed as presumed NSTE-ACS first. The hypertension is likely a consequence of pain and sympathetic activation - treat the ACS with beta-blockers and nitrates, and the BP will respond. Aggressive BP-lowering alone without addressing the ischemia is inadequate management here.

ECG Interpretation

Machine-Reported Measurements (from the printed report)

Lead-by-Lead Visual Analysis

Rhythm

• Regular rhythm - R-R intervals appear consistent
• HR ~68 bpm - normal
• P waves present before every QRS - confirms Normal Sinus Rhythm

P Waves

• Upright in leads I, II, aVF - normal sinus P waves
• Normal morphology, no notching, no biphasic P in V1 to suggest LA enlargement

PR Interval

• 138 ms - within normal limits (120-200 ms) ✅

QRS Complex

• 80 ms - narrow, normal ✅
• No bundle branch block pattern
• Normal R wave progression visible in precordial leads V1-V6

Axis

• QRS axis ~80° - Normal axis ✅ (normal range: -30° to +90°)

ST Segments

• Looking carefully at the precordial leads (V1-V6): no obvious ST elevation or depression
• Limb leads appear isoelectric at the J-point
• No classic Wellens pattern or de Winter changes visible

T Waves

• Upright in I, II, aVF, V4-V6
• No obvious T wave inversion in the lateral leads
• T waves in V1-V2 appear normal (may be flat/biphasic - normal in those leads)

QT Interval

• Machine reports QTc around 560 ms - if accurate, this is prolonged (normal <440 ms men, <460 ms women)
• However, this value should be manually verified as machine QT measurement can be unreliable

Overall Interpretation

Machine says: Normal ECG / Sinus Rhythm

Clinical assessment in the context of your earlier presentation (BP 160/80, chest pain, elevated CK-MB):

This ECG does NOT show STEMI - no ST elevation, no LBBB.

1. NSTEMI - by definition has no ST elevation
2. Unstable angina
3. Posterior MI (may only show tall R and ST depression in V1-V2 - look carefully)

⚠️ Critical Points for This Patient

What to Do Next

1. Do NOT rely solely on this ECG - a normal ECG does not rule out ACS with elevated CK-MB
2. Repeat ECG every 30 minutes while chest pain persists - dynamic changes (new ST depression, T inversion, Wellens) may appear
3. Serial troponins remain mandatory (0h, 3h, 6h)
4. Measure QTc manually using: QTc = QT / √(RR interval in seconds)
5. Posterior leads (V7-V9) - consider if posterior MI suspected
6. Right-sided leads (V3R, V4R) - if inferior ST changes appear, rule out RV infarct

The combination of chest pain + elevated CK-MB + this ECG puts this patient in the NSTE-ACS category requiring continued monitoring, antiplatelet therapy, anticoagulation, and cardiology consult regardless of this ECG appearing "normal."