Presentation of a patient with cholinergic syndrome:
(1) miosis (with bilateral pinpoint pupils)
(2) excessive sweating
(3) poor air entry into the lungs secondary to bronchospasm and bronchorrhoea (with excessive secretions)
(4) bradycardia (the heart rate may also be normal or increased)
(5) hypotension (systolic blood pressure < 80 mm Hg)
Initial management with atropine:
(1) 1.8 to 3.0 mg IV push into a fast-flowing IV infusion
(2) If there is no improvement in 3-5 minutes, then double the IV dose.
(3) If there is no improvement in another 3-5 minutes, then double the dose again.
The doubling is continued each cycle. Some patients may require hundreds of milligrams of atropine, and rapid atropine is essential in these patients. However, the risk of atropine toxicity increases with higher doses.
Target end-points for atropine therapy:
(1) chest clear on auscultation (except if there has been aspiration)
(2) no wheezing
(3) heart rate > 80 beats per minute (if bradycardic)
(4) pupils no longer pinpoint (except if pesticide has been splashed into the eye)
(5) dry axillae (decreased sweating)
(6) systolic blood pressure > 80 mm Hg
Signs of atropine toxicity:
(1) (confusion and/or hyperthermia/pyrexia) AND absent bowel sounds
(2) urinary retention
Differential diagnosis of atropine toxicity includes:
(1) alcohol withdrawal, which can cause confusion
(2) pneumonia or occult infection, which can cause fever
(3) benign prostatic hypertrophy, which can cause urinary retention
