Retrobulbar block: Hemodynamic effect
When the block is performed, the pain associated with the block frequently induces elevated heart rate and blood pressure in the minutes immediately following. With the passage of time, however, the patient usually has very few complaints of pain during the surgery and does not have subsequent hemodynamic changes stemming from the block unless complications occur.
Complications of retrobulbar block include orbital perforation or ischemia, vascular injury causing retrobulbar hemorrhage, brainstem anesthesia, and activation of the oculocardiac reflex. Of these complications, the oculocardiac reflex is the common. The oculocardiac reflex occurs when afferent nerve signals are sent via the trigeminal nerve to synapses with the vagus nerve on the floor of the fourth ventricle. These signals may induce bradycardia and occasionally arrhythmias, particularly in younger patients.
Brainstem anesthesia occurs when local anesthetic is accidentally injected in the subdural space, likely due to placement of the needle through the optic nerve sheath. This results in respiratory depression and even arrest requiring assisted ventilation. Hemodynamic changes are occasional and variable.