Which medication is used to treat a client with a dangerously high level of beta blockers?

Glucagon is used to treat a client with a dangerously high level of beta blockers because it can help to counteract the effects of beta-blockade on the heart. Beta-blockers work by blocking beta-adrenergic receptors, leading to decreased heart rate and contractility. In cases of overdose or toxicity, glucagon can stimulate adenylate cyclase to increase cyclic AMP levels, which can improve heart function and raise heart rate independently of the beta-adrenergic receptor pathway. This makes glucagon particularly effective in reversing the cardiac effects of beta-blocker overdose.

Other medications listed do not serve this purpose in the context of beta-blocker toxicity. For instance, atropine primarily increases heart rate by blocking vagal effects on the heart but may not be effective in cases of significant beta-blocker toxicity. Dopamine could potentially increase heart rate and contractility but depends on a functioning adrenergic system and may not be effective in this scenario. Atenolol, being a beta-blocker itself, would further exacerbate the problem in the case of an overdose. Thus, glucagon stands out as an appropriate and potentially lifesaving intervention in this situation.