What immediate action should be taken if a third-degree AV block is suspected in a patient?

In cases where third-degree AV block is suspected, the most important immediate action is to monitor the patient closely to assess their hemodynamic status and ensure they are stable. Continuous pulse oximetry monitoring provides essential information regarding the patient's oxygen saturation and respiratory status, which is crucial since this type of block can lead to inadequate cardiac output and potentially result in hypoxia or more severe complications.

Effective monitoring at this stage allows healthcare providers to detect any signs of deterioration promptly, enabling timely interventions that may include pacing or advanced cardiac life support if necessary. While the other options—such as increasing fluid rate, administering anticoagulants, or scheduling an echocardiogram—might be relevant in different clinical scenarios, they do not address the immediate need for patient assessment and observation when an AV block is suspected. The priority is to maintain the patient's safety and stabilize their condition while further testing or treatments can be planned based on ongoing evaluation.