A pressure adjustment protocol for programmable valves.

OBJECTIVE: There is no definite adjustment protocol for patients shunted with programmable valves. Therefore, we attempted to find an appropriate method to adjust the valve, initial valve-opening pressure, adjustment scale, adjustment time interval, and final valve-opening pressure of a programmable valve.

METHODS: Seventy patients with hydrocephalus of various etiologies were shunted with programmable shunting devices (Micro Valve with RICKHAM(R) Reservoir). The most common initial diseases were subarachnoid hemorrhage (SAH) and head trauma. Sixty-six patients had a communicating type of hydrocephalus, and 4 had an obstructive type of hydrocephalus. Fifty-one patients had normal pressure-type hydrocephalus and 19 patients had high pressure-type hydrocephalus. We set the initial valve pressure to 10-30 mmH(2)O, which is lower than the preoperative lumbar tapping pressure or the intraoperative ventricular tapping pressure, conducted brain computerized tomographic (CT) scans every 2 to 3 weeks, correlated results with clinical symptoms, and reset valve-opening pressures.

RESULTS: Initial valve-opening pressures varied from 30 to 180 mmH(2)O (mean, 102 +/- 27.5 mmH(2)O). In high pressure-type hydrocephalus patients, we have set the initial valve-opening pressure from 100 to 180 mmH(2)O. We decreased the valve-opening pressure 20-30 mmH(2)O at every 2- or 3-week interval, until hydrocephalus-related symptoms improved and the size of the ventricle was normalized. There were 154 adjustments in 81 operations (mean, 1.9 times). In 19 high pressure-type patients, final valve-opening pressures were 30-160 mmH(2)O, and 16 (84%) patients' symptoms had nearly improved completely. However, in 51 normal pressure-type patients, only 31 (61%) had improved. Surprisingly, in 22 of the 31 normal pressure-type improved patients, final valve-opening pressures were 30 mmH(2)O (16 patients) and 40 mmH(2)O (6 patients). Furthermore, when final valve-opening pressures were adjusted to 30 mmH(2)O, 14 patients symptom was improved just at the point. There were 18 (22%) major complications : 7 subdural hygroma, 6 shunt obstructions, and 5 shunt infections.

CONCLUSION: In normal pressure-type hydrocephalus, most patients improved when the final valve-opening pressure was 30 mmH(2)O. We suggest that all normal pressure-type hydrocephalus patients be shunted with programmable valves, and their initial valve-opening pressures set to 10-30 mmH(2)O below their preoperative cerebrospinal fluid (CSF) pressures. If final valve-opening pressures are lowered in 20 or 30 mmH(2)O scale at 2- or 3-week intervals, reaching a final pressure of 30 mmH(2)O, we believe that there is a low risk of overdrainage syndromes.