Choking, Hypoxic Cardiac Arrest, and ROSC Pathophysiology

Vocabulary flashcards covering the pathophysiology of airway obstruction, the progression to hypoxic cardiac arrest, ETCO2 monitoring, pharmacological interventions, and post-ROSC recovery based on clinical lecture notes.

Partial obstruction

A condition where air movement still occurs, the patient can cough, and stridor may be present while oxygenation begins to fall.

Complete obstruction

A condition with no effective air movement and no oxygen entry to the lungs, leading to rapid development of hypoxaemia.

Stridor

A high-pitched inspiratory sound that occurs when air is forced through a narrowed upper airway.

Hypoxaemia

Low oxygen in arterial blood.

Hypoxia

Inadequate oxygen delivery to tissues.

Paediatric bradycardia

A sign of severe hypoxia and impending cardiac arrest occurring when the heart can no longer maintain compensatory tachycardia due to decreased myocardial oxygen delivery.

PEA (Pulseless Electrical Activity)

A state where the monitor shows organised electrical activity but mechanical contraction is ineffective or absent, resulting in no pulse.

Common paediatric arrest pathway

Respiratory failure $\rightarrow$ Hypoxia $\rightarrow$ Bradycardia $\rightarrow$ PEA $\rightarrow$ Asystole.

Normal ETCO$_2$

$$35–45\,mmHg$$

ETCO$_2$ changes before arrest

Falling levels caused by reduced pulmonary blood flow, reduced cardiac output, and reduced alveolar gas exchange.

ETCO$_2$ changes after ROSC

Increasing levels due to improved circulation, pulmonary perfusion, and ventilation; a sudden rise can be an early indicator of ROSC.

Alpha-1 receptor effects (Adrenaline)

Causes peripheral vasoconstriction, leading to increased systemic vascular resistance, increased aortic diastolic pressure, and increased coronary perfusion pressure.

Beta-1 receptor effects (Adrenaline)

Increases heart rate, contractility, and conduction velocity.

Beta-2 receptor effects (Adrenaline)

Causes bronchodilation in the lungs and mild vasodilation in peripheral vessels.

Adrenaline's role in cardiac arrest

Causes vasoconstriction to redirect the limited cardiac output generated by CPR ($25–30\%$) toward the heart and brain.

Crystalloid Fluid (Normal Saline)

A fluid that remains primarily within the extracellular space to expand circulating volume and improve preload, stroke volume, and tissue perfusion.

ROSC

Return of Spontaneous Circulation.

Reperfusion injury

Cellular injury, inflammation, and free radical production triggered when ischaemic tissues are reperfused after ROSC.

Post-ROSC complications

Cerebral oedema, seizures, myocardial dysfunction, hypotension, and multi-organ dysfunction.