Normal Pressure Hydrocephalus (NPH)

Baseline neuro exam - Chart gait, orientation and continence before induction. The scales used to track NPH pre- and post-shunt are the MMSE, the Timed Up and Go, and the Berg Balance Scale; a number in the chart makes postoperative confusion or a new gait deficit interpretable instead of a guess.

Access and lines - Two IVs. Once the head and abdomen are prepped and draped there is almost no access to the patient. An arterial line is not routine for a shunt — add it for cardiovascular disease, not for the operation itself.

Positioning and room setup - The table gets turned 90 degrees and pushed out so two teams can work at the head and the abdomen simultaneously. Get circuit extensions; the machine ends up 5–10 feet away. Head is turned to one side with slight forward flexion, sometimes in Mayfield pins.

ETT position after head turn - Recheck depth and auscultate after the surgical team finishes positioning the head — flexion and rotation migrate the tube toward the right mainstem.

Ventilation target - The surgeon may ask for hyperventilation to an EtCO2 of 25–30 to slacken the brain. Clarify the target before you drape.

Gastric decompression - Expect a request for an OG tube to low suction before the abdominal portion.

Abdominal insufflation - The peritoneum is insufflated to place the distal catheter. Be ready for a vagal bradycardia and a pressure swing.

Ventricular decompression - When the surgeon enters the ventricle and drains it, the pressure around the brainstem falls with it and blood pressure can drop abruptly. Have phenylephrine drawn up and in line.

Subcutaneous tunneling - Tunneling the catheter from scalp to abdomen is intensely stimulating and the patient is not deeply anesthetized for it by default. A sudden HR and BP surge here is the catheter, not light anesthesia elsewhere — deepen and give opioid ahead of it.

Overdrainage - Overdrainage is the characteristic shunt complication, which is why gravitational valves and anti-siphon devices exist. Postoperative headache that is worse upright, or a new decline after an uneventful case, is a shunt problem until neurosurgery says otherwise.

Emergence - These patients start with subcortical dementia and a gait that is already unsafe. Plan a clean, unsedated emergence and hand off with the preoperative baseline attached, and keep them from ambulating unassisted in PACU.

Normal pressure hydrocephalus (NPH) is a communicating hydrocephalus of older adults. CSF absorption at the arachnoid granulations is impaired, the ventricles enlarge, and opening pressure on lumbar puncture reads normal or near-normal — though basal ICP has to have been elevated for some period for NPH to develop at all. Stretching of periventricular fibers and the corticospinal tract produces the Hakim triad: a magnetic, wide-based, glue-footed gait, subcortical dementia with poor executive function, and urinary urgency or incontinence from detrusor overactivity.

Diagnosis is confirmed by a high-volume LP (30–50 mL removed) or a lumbar drain trial with gait retested afterward. Definitive treatment is a ventriculoperitoneal or lumboperitoneal shunt with an adjustable valve. You meet these patients for the shunt itself, for the tap or drain trial, or with a shunt already in place for unrelated surgery.