ACLS | ACS and Preventing Arrest

Rapid Response System (RRT) Triggers

Over half of in-hospital cardiac arrests (IHCAs) stem from respiratory failure or hypovolemic shock[1]. RRS activates based on adult criteria[1]:

• Airway & Breathing: Airway compromise; respiratory rate <6/min or >30/min[1].
• Circulation: Heart rate <40/min or >140/min; SBP <90 mmHg; symptomatic hypertension[1].
• Neurological & Renal: Unexpected drop in consciousness; unexplained agitation; seizures; significant urine output drop[1].
• Subjective: Clinician concern regarding patient deterioration[1].

II. ACS Classification & Triage

The initial 12-lead ECG is central to classifying ACS into two major categories[2]:

1. STEMI: ST elevation in ≥2 contiguous leads (≥2 mm in V2–V3 for men ≥40, ≥2.5 mm for men <40, ≥1.5 mm for women; ≥1 mm in other leads) or new LBBB[4]. Indicates complete coronary occlusion requiring immediate reperfusion[5].
2. NSTE-ACS: ST depression (≥0.5 mm), dynamic T-wave inversion, transient ST elevation, or normal/nondiagnostic ECG[2][4].

III. Initial Medications & Critical Traps

ED assessment within 10 minutes targets ischemia relief and risk triage[3]:

• Aspirin: Administer 162 to 325 mg (chewed) immediately to inhibit COX-1 and thromboxane A2[4][7]. Suppositories (300 mg) for severe nausea/vomiting[7]. Contraindicated in true allergy or active/recent GI bleed[4][7].
• Oxygen: Give (4 L/min) only if SpO2 <90%, dyspneic, hypoxemic, or showing heart failure signs; withhold in normoxic patients[4][7].
• Nitroglycerin: Give 1 sublingual dose every 3–5 minutes (max 3 doses)[7][8]. Contraindications: SBP <90 mmHg (or ≥30 mmHg drop below baseline), severe bradycardia (<50/min), tachycardia (>100/min), or RV infarction[4][7].
• Morphine: IV for pain unalleviated by nitroglycerin; caution in hypotension or RV infarction[4][7]. Can decrease oral antiplatelet absorption[4].
• NSAID Contraindication: NSAIDs (except aspirin) are strictly avoided due to increased risk of mortality, reinfarction, and myocardial rupture[9].

IV. STEMI Reperfusion Timelines

Reperfusion within 12 hours of onset limits myocardial necrosis[5][10]:

• Primary PCI: Preferred strategy[10]. FMC-to-balloon goal ≤90 minutes (≤120 minutes if transferred to PCI facility)[10].
• Fibrinolysis: Door-to-needle goal ≤30 minutes[10]. Most effective within 1 hour of symptom onset (reduces mortality by 47%)[5][10]. Not recommended if symptoms >12 hours; contraindicated >24 hours or for ST depression without posterior MI[8].

V. NSTE-ACS & Adjunctive Care

• High-Risk NSTE-ACS: Early invasive strategy indicated for refractory ischemia, recurrent ST deviation, VT, instability, or heart failure[4][6].
• IV Nitroglycerin: For recurrent ischemia, hypertension, or pulmonary edema; titrate maintaining SBP >90 mmHg[8][11].
• Heparin: Routine adjunct for PCI and fibrinolysis[8].