Final answer:
The nurse should be ready to adjust the IV infusion and prepare for defibrillation if a client exhibits dangerous PVCs and is under lidocaine treatment. Defibrillation is vital for ventricular fibrillation, a medical emergency that requires life support and prompt action.
Step-by-step explanation:
If a client has started to exhibit dangerous Premature Ventricular Contractions (PVCs) in the cardiac postoperative unit and is already under continuous IV infusion of lidocaine with a previous bolus administered, the nurse should be prepared to adjust the IV infusion rate if the client exhibits signs of lidocaine toxicity or systemic effects like hypotension. However, if the PVCs persist or worsen, indicating potential progression to ventricular fibrillation, the nurse should be ready to prepare for defibrillation. This is because ventricular fibrillation is a life-threatening emergency where the ventricles cannot pump blood effectively and defibrillation can restore a normal sinus rhythm. Immediate action and readiness for advanced cardiac life support measures are crucial in such situations. Calling for the doctor is necessary, but waiting without preparing for further intervention could be detrimental to the patient's health.
Lidocaine is used in this scenario as an antiarrhythmic agent due to its ability to block voltage-gated sodium channels. Blocking these channels reduces the excitability of cardiac cells by preventing sodium ions from entering the cell during the action potential, which reduces the propensity for ectopic heartbeats that lead to arrhythmias. In other contexts, lidocaine's action on sodium channels in nerve cells leads to numbness and pain relief, as it prevents the propagation of pain signals.