Cardiovascular and Respiratory Emergencies
Time-critical ischaemia and failing ventilation
Acute coronary syndrome demands a 12-lead electrocardiogram within 10 minutes of arrival. Reperfusion targets are door-to-balloon within 90 minutes for primary percutaneous coronary intervention and door-to-needle within 30 minutes where fibrinolysis is chosen. Give aspirin 162–325 mg chewed. Nitroglycerin is contraindicated in right ventricular infarction (hypotension after nitrate) and within 24–48 hours of phosphodiesterase-5 inhibitors. Oxygen is a drug: give it for hypoxaemia, not routinely to a patient with normal saturation. Morphine is no longer routine. In cardiac arrest, shockable rhythms (ventricular fibrillation, pulseless ventricular tachycardia) are defibrillated immediately, with epinephrine 1 mg every three to five minutes and amiodarone for refractory cases.
On the respiratory side, know the asthma severity markers: inability to speak, accessory muscle use, silent chest, bradycardia, exhaustion, and a normal or rising carbon dioxide in a previously hypocapnic patient. A silent chest is a pre-arrest sign, not improvement. Non-invasive ventilation is avoided with vomiting, reduced consciousness or facial trauma. Acute respiratory distress syndrome is ventilated with lung-protective volumes near 6 mL/kg of predicted body weight.
Interpret arterial blood gases systematically: pH first, then decide whether the primary change is respiratory or metabolic, then check compensation and calculate the expected value.
Worked example: pH 7.28, PaCO2 30 mmHg, bicarbonate 14 mmol/L. The primary disorder is metabolic acidosis; the low CO2 is respiratory compensation (expected CO2 ≈ 1.5 × 14 + 8 = 29).
Traps: relying on pulse oximetry when carbon monoxide or poor perfusion may mislead, and labelling any breathless patient as cardiac without assessing the airway.