Appendicitis

Appendicitis

Obstruction of the appendiceal lumen, causing fluid to accumulate in the appendix, where microorganisms proliferate.

Pathophysiology

1. Lumen obstruction but appendix continues to produced mucus and secrete fluids but the outflow is blocked, increasing pressure.

2. Stagnant environment also allow bacteria to proliferate in anaerobic conditions.

3. Infection then triggers neutrophil infiltration, releases inflammatory mediators and purulent exudate.

4. As venous outflow and arterial inflow is compromised, it leads to ischaemia and necrosis of the appendiceal wall.

Pain

Early inflammation causes irritation of visceral afferent fibres = dull and poorly localised

Becomes localised as it irritates the parietal peritoneum = shifts to RLQ pain

Rovsing (LLQ causes pain in RLQ) from inflamed peritoneal stretching and increasing intraluminal pressure

If ischaemia or full-thickness necrosis leads to perforation = sudden drop in intraluminal pressure and temporary pain relief

Pyrexia

Cytokine mediated + tachycardia + mild leucocytosis

Consequences

Bacteria enters the peritoneal cavity, causing peritonitis. And a cytokine surge = vasodilation, hypotension and septic shock

IV Paracetamol: Actions

Analgesic - inhibits COX 3 (splice variant), preventing central prostaglandin synthesis and reducing pain signal amplification of the CNS.

Antipyretic - works directly on hypothalamus, promoting diaphoresis and loss of body heat

IV Paracetamol: Benefits

Effective in mild-moderate analgesia regimen

Opioid sparing, reducing risk of respiratory depression, nausea or sedation.

It also does not impair platelet aggregation like NSAIDs

IV Paracetamol: Risks

Hepatotoxicity - paracetamol is metabolised in the liver, so overdose can lead to acute liver failure or hepatic encephalopathy.

If administered too quickly, can cause vasodilation and transient hypotension

Severe renal impairment caution - may impair renal perfusion

Ondansetron: Actions

Highly selective 5HT3 (serotonin) receptor antagonist. Blocks these receptors in the CTZ in the medulla oblongata. Prevents communication between the CTZ and vomiting centre to reduce N+V

Ondansetron: Benefits

Highly selective means it has minimal effects on other serotonin pathways. Improves patient comfort and helps tolerate treatments.

Ondansetron: Risks

Other neurotransmitter like acetylcholine and dopamine also interacts with the CTZ, therefore it is not always effects.

OND can block a gene that regulates potassium channels in the heart, preventing cardiac repolarisation, and causing Long QT that can escalate to TdP.