Final answer:
The best nursing action immediately following a ventriculoperitoneal shunt procedure in an infant with hydrocephalus is to maintain a flat head position to prevent excessive CSF flow and related complications.
Step-by-step explanation:
Immediately following the procedure of ventriculoperitoneal shunt insertion for treating hydrocephalus in an infant, the best nursing action to prevent decompression due to excessive cerebrospinal fluid (CSF) flow would be: C. Maintain a flat head position. Elevating the head of the bed may actually promote more rapid drainage of CSF, which can increase the risk of overdraining and related complications such as collapse of the ventricles or tearing of blood vessels. Keeping the head flat will reduce this risk and allow for gradual stabilization of CSF levels in accordance with ventricular and peritoneal absorption dynamics.