Final answer:
Glycopyrrolate or atropine are necessary when administering a remifentanil bolus to counteract the remifentanil-induced bradycardia by blocking parasympathetic stimulation.
Step-by-step explanation:
Glycopyrrolate or atropine should be on hand when administering a remifentanil bolus because these medications can mitigate potential side effects such as bradycardia (a dangerously slow heart rate) that remifentanil can induce. Both glycopyrrolate and atropine are anticholinergic drugs, which means they work by blocking the action of the neurotransmitter acetylcholine in the parasympathetic nervous system.
When remifentanil is given, it may stimulate parasympathetic activity that leads to a decrease in heart rate. To counteract these effects and maintain a safe heart rate, glycopyrrolate or atropine is administered, as these drugs act as antagonists to muscarinic acetylcholine receptors. Atropine, in particular, crosses the blood-brain barrier less effectively than some synthetic counterparts, which may be preferable in managing central symptoms of nerve agent poisoning, but its peripheral effects are crucial in a setting where remifentanil is used.