Pharmacology for Paramedics Flashcards

The pharmacological difference between succinylcholine and rocuronium as neuromuscular blocking agents is:

Answer: Succinylcholine is depolarising (short-acting, cannot be reversed); rocuronium is non-depolarising (longer-acting, reversible with sugammadex)

Succinylcholine mimics acetylcholine causing sustained depolarisation (fasciculations, then paralysis) — ultra-short acting (8-10 min) but irreversible. Rocuronium competitively blocks nicotinic receptors — longer acting but reversible with sugammadex.

Sodium bicarbonate 8.4% IV is used in which pre-hospital toxicological emergency?

Answer: Tricyclic antidepressant (TCA) overdose with QRS prolongation or hypotension

In TCA overdose, sodium bicarbonate alkalises the plasma, reducing TCA binding to sodium channels, and provides extra sodium to overcome cardiac sodium channel blockade, shortening QRS duration and improving haemodynamics.

Dexamethasone is used in the pre-hospital management of severe croup because:

Answer: It reduces laryngeal/subglottic inflammation, providing sustained airway improvement over 12-24 hours

Dexamethasone's anti-inflammatory effect reduces subglottic oedema over hours, providing sustained benefit and reducing the chance of hospitalisation or rebound after nebulised adrenaline wears off.

In pre-hospital pain management, what is the significance of the 'analgesic ceiling effect'?

Answer: Some analgesics (e.g., paracetamol, NSAIDs) have a maximum effective dose beyond which increasing the dose adds no benefit but increases side effects

Ceiling effect drugs have a dose above which additional analgesia is not achieved — unlike opioids (no true ceiling for analgesia); paracetamol at 1g IV will not be more effective at 2g, only more toxic.

Vasopressin is used in septic shock as a vasopressor because:

Answer: It acts on V1 receptors independently of adrenoceptors — effective when catecholamine levels are already maximally elevated

In refractory septic shock, endogenous vasopressin is depleted; exogenous vasopressin acts on V1 receptors (vascular smooth muscle) through a non-adrenergic mechanism, providing vasoconstriction when adrenergic receptors are downregulated.

Tranexamic acid (TXA) works in traumatic haemorrhage by:

Answer: Inhibiting fibrinolysis (clot breakdown) by blocking plasminogen activation — preserving formed clots

TXA is an antifibrinolytic that blocks plasminogen conversion to plasmin, preventing breakdown of formed clots in injured vessels; it is most effective when given within 3 hours of injury (CRASH-2 trial evidence).