We retrospectively analyzed 46 patients who underwent LPS for iNPH in our institution during the period from February 2017 to January 2020, with more than 12 months of follow-up. All patients were confirmed to be free of obstructive hydrocephalus, based on having normal intracranial pressure as determined by spinal lumbar puncture, and were diagnosed as having iNPH. All patients selected LPS rather than standard VPS after they and/or their first-degree relatives received a full explanation of both procedures prior to surgery. Then, all patients selected either general anesthesia or rachianesthesia after they and/or their first-degree relatives received a full explanation of both forms of anesthesia prior to surgery. All procedures performed in this study were in accordance with the ethical standards of our institutional and national research committee, as well as with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. We also obtained approval from the ethics committee of our institution for this study. Written informed consent was obtained from all individual participants and/or their first-degree relatives, prior to inclusion in the study.
For all patients, anesthesiologists determined preoperative American Society of Anesthesiologists physical status (ASA-PS), and registered nurses determined both preoperative and postoperative delirium scores using the intensive care delirium screening checklist (ICDSC).[3, 12] Perioperative complications, postoperative symptomatic improvements, and the length of hospital stay were analyzed in all patients by three neurosurgeons. In order to control for potential confounding factors regarding the ICDSC and the length of hospital stay analyses, we excluded from this study patients who were transferred to our institution from other hospitals only for the LPS surgical procedure and those who were transferred to other hospitals after LPS regardless of their status; all of the patients in this study were non-institutionalized and had been admitted to our hospital from their own homes and were discharged to their homes (Fig. 1). In order to compare the two anesthetic approaches chosen, we divided the patients into two groups; 1) general anesthesia and 2) rachianesthesia. We analyzed these two groups with regard to postoperative complications and the length of hospital stay (Table 1).
Table 1
Patient characteristics of each group
| General anesthesia | Rachianesthesia | Total | P-values |
| (n = 29) | (n = 16) | (n = 45) | |
Age (years) | 79.4 (5.2) | 81.1 (8.3) | 80.0(6.5) | 0.6604 |
BMI | 25.5 (0.3) | 21.1 (2.7) | 22.4 (3.0) | 0.5375 |
ASA-PS | 2.1 (0.3) | 2 (0) | 2.1 (0.2) | 0.1879 |
Preoperative ICDSC | 0.6 (0.8) | 0.9 (0.9) | 0.7 (0.9) | 0.1966 |
Surgical time (minutes) | 41.6 (33.4) | 33.9 (24.0) | 38.8 (30.6) | 0.1760 |
Postoperative ICDSC | 1.3 (1.4) | 1.3 (1.4) | 1.3 (1.3) | 0.8246 |
Length of hospital stay (days) | 13.9 (4.7) | 10.8 (2.1) | 12.8 (4.2) | 0.0360 |
ASA-PS: American Society of Anesthesiologists physical status, BMI: body mass index, ICDSC: intensive care delirium screening checklist |
Patients in the general anesthesia group underwent bolus administration of propofol and/or sevoflurane, remifentanil hydrochloride, and rocuronium bromide, followed by tracheal intubation or fixation of a laryngeal mask airway. During the surgery, anesthesiologists administered these medications continually or intermittently. There was no use of sedation (i.e., dexmedetomidine hydrochloride) or neuraxial anesthesia in any patients before or after the surgery. Postoperative pain control was achieved with acetaminophen or loxoprofen sodium hydrate. The LPS procedures were as follows; a 3cm skin incision was made in the posterior lumbar region, at a site depending on the preoperatively determined level using lumbar computed tomography scans. After making this small skin incision and dissecting the subcutaneous connective tissue, we inserted a 14-gauge needle from the inter-spinous ligament or inter-lamina space (Fig. 2). After achieving lumbar puncture, we inserted a spinal catheter into the subarachnoid space and ascertained the cerebral spinal fluid outflow from this catheter. Then, we placed the indwelling valve system on the lumbar posterior side of the paravertebral spinal muscle beneath the skin of the lower back. The main component of valve system was a CODMAN CERTAS Plus programmable valve with a SiphonGuard system (Codman Neuro, MA, USA), and initial valve pressure was determined based on the patient’s body weight and height, then adjusted depending on their activities and clinical manifestations as documented by periodic outpatient visits.[14]
Patients in the rachianesthesia group underwent lumbar puncture and were administered 20 milligrams of isobaric bupivacaine hydrochloride hydrate into the lumbar subarachnoid space, at a slow pace. After the anesthesiologist confirmed that the patient had no sensation beneath the ensiform process, which usually took 10 to 15 minutes while maintaining the decubitus position, we started the LPS procedures. Minimal levels of sedation with dexmedetomidine hydrochloride were used in some patients, depending on their conditions. None of the patients received additional sedation or neuraxial anesthesia either before or after the surgery. Postoperative pain control, the LPS procedures, and valve pressure adjustments were the same as those employed in the general anesthesia group.