Final answer:
The treatment option not used for LAST is calcium channel blockers, as they have negative inotropic effects and could worsen cardiotoxicity, whereas treatments like benzodiazepines and propofol are appropriate for managing seizures in LAST.
Step-by-step explanation:
The treatment option that would not be used for a patient with Local Anesthetic Systemic Toxicity (LAST) is E) Calcium channel blockers. While benzodiazepines and propofol are considered appropriate treatment options for LAST as they have sedative effects and can help to control seizures, calcium channel blockers are negative inotropic agents that decrease the strength of heart muscle contraction and would not be beneficial in a case of LAST. In LAST, the focus is on managing seizures and cardiovascular complications using options such as cardiopulmonary resuscitation and medication to support heart function, which is why something like cardiopulmonary bypass could be considered in severe cases.
Bag-mask ventilation is a vital support treatment in LAST to ensure that the patient is receiving enough oxygen, especially if they are experiencing respiratory difficulty. Injection of a solution like KCl would be used in completely different scenarios, such as to stop a beating heart during open-heart surgery, not for treating LAST. Therefore, the use of calcium channel blockers is contraindicated as they could exacerbate the cardio-toxic effects of local anesthetics that triggered LAST.