Abstract
Since the publication of guidelines for managing idiopathic normal pressure hydrocephalus (iNPH) in 2004, an increasing number of patients with iNPH have been undergoing shunt surgery in Japan. However, shunt surgeries for iNPH can be challenging because the procedures are performed on elderly patients. General anesthesia-related risks, such as postoperative pneumonia or delirium, are higher in the elderly. To decrease these risks, we applied spinal anesthesia on a lumboperitoneal shunt (LPS). Herein, we analyzed our methods focusing on the postoperative outcomes. We retrospectively analyzed 79 patients who underwent LPS at our institution with more than one year of follow-up. The patients were divided into two groups based on the anesthetic approach, that is, 1) general anesthesia and 2) spinal anesthesia, and were examined in terms of postoperative complications, delirium, and postoperative hospital stay. In the general anesthesia group, two patients had respiratory complications after the surgery. The postoperative delirium score using the intensive care delirium screening checklist (ICDSC) was 0 (2) (median [interquartile range]), and the length of postoperative hospital stay was 11 (4) days. In the spinal anesthesia group, no patients had respiratory complications. The postoperative mean ICDSC was 0 (1), and the length of postoperative hospital stay was 10 (3) days. Although there was no significant difference regarding postoperative delirium existed, LPS under spinal anesthesia decreased respiratory complications and significantly shortened the postoperative hospital stay. LPS under spinal anesthesia could be an alternative to general anesthesia in elderly patients with iNPH and possibly lessen the general anesthesia-related risks.
Keywords: elderly patient, idiopathic normal pressure hydrocephalus, lumboperitoneal shunt, spinal anesthesia
Introduction
Among aging societies, the number of patients with idiopathic normal pressure hydrocephalus (iNPH) is increasing. After the publication of the first edition of the guidelines for the management of iNPH in 2004 (the English version was published in 2008) and the conduction of multicenter prospective cohort studies in Japan (multicenter trial to iNPH diagnosis via magnetic resonance imaging [MRI]-based scheme [SINPHONI] and multicenter trial to assess lumboperitoneal shunt [LPS] implantation in patients with iNPH [SINPHONI-2]), an increasing number of patients with iNPH have undergone shunt surgery, such as ventriculoperitoneal shunt (VPS) or LPS.1-4) Nevertheless, the incidence of preoperative impaired general conditions such as cardiac, pulmonary, and renal reserve loss is increasing with age.5,6) Postoperative cognitive decline and delirium are also reported to be more prevalent in patients older than 65 years.7) According to reports, these risks are linked to poor functional outcomes and extended institutionalization.8,9) Neuraxial anesthesia, such as spinal anesthesia, decreased the aforementioned complications more than general anesthesia, which was associated with lower hospital mortality and shorter length of hospital stays.3,6,9) In this study, we administered spinal anesthesia on the LPS and analyzed our methods with a focus on technical characteristics and postoperative results.
Materials and Methods
Patient cohort
We conducted a retrospective analysis of 129 patients diagnosed with iNPH who underwent LPS at our institution between February 2017 and February 2022. All patients were confirmed to be free of obstructive hydrocephalus, had normal intracranial pressure as determined by lumbar spinal puncture, and were diagnosed with iNPH according to the guidelines for the management of iNPH (the second edition was published in 2012, and the third edition was in 2021).4,10,11) To control for potential confounding factors regarding the delirium score and the length of postoperative hospital stay analyses, in this study, we excluded 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 noninstitutionalized and had been admitted to our hospital from their own homes and were discharged to their homes. Consequently, 79 patients who received LPS for iNPH and were followed up for more than a year were enrolled in this study.
For all patients, anesthesiologists determined preoperative American Society of Anesthesiologists physical status (ASA-PS), and occupational or physical therapists determined Mini-Mental State Examination (MMSE) and iNPH grading scale (iNPHGS).12-14) Using the intensive care delirium screening checklist (ICDSC), registered nurses determined preoperative and postoperative delirium scores.15) Primarily, general anesthesia was administered to the first consecutive patients. The remaining patients were administered spinal anesthesia. To compare the two anesthetic methods selected, the patients were divided into two groups: 1) general anesthesia and 2) spinal anesthesia. We compared the postoperative complications, delirium score, and length of hospital stay between these two groups.
Anesthetic techniques
In the general anesthesia group, patients received a bolus administration of propofol and sevoflurane, remifentanil hydrochloride, and rocuronium bromide, followed by tracheal intubation or fixation of a laryngeal mask airway. Anesthesiologists administered these medications continuously or intermittently during surgery. The patients did not receive sedation (i.e., dexmedetomidine hydrochloride) or neuraxial anesthesia before or after the surgery. Acetaminophen or loxoprofen sodium hydrate was effective in managing postoperative pain.
Slowly, 20 mg of isobaric bupivacaine hydrochloride hydrate was administered into the lumbar subarachnoid space of patients in the spinal anesthesia group who underwent lumbar puncture. After the anesthesiologist confirmed that the patient had no sensation beneath the ensiform process, which typically takes 10-15 min while maintaining the decubitus position, the LPS procedures were initiated. Depending on the patient's condition, dexmedetomidine hydrochloride was used to induce minimal sedation in some patients. Before or after surgery, no patient received additional sedation or neuraxial anesthesia. Postoperative pain management, LPS procedures, and valve pressure adjustments were identical to those applied in the general anesthesia group.
Operative technique
The LPS procedures were identical in both groups. We made two small skin incisions. One skin incision was for the laparotomy between the tenth costal inferior edge and the anterior superior iliac spine. The other was the spinal tube catheterization performed inferior and lateral to the midline of the lower back. The laparotomy was performed on the lateral side of the patient's trunk, proceeding with the LPS without a relaying wound or any change in operative position. After incising each site, using a passer, we pass the shunt system between the two skin incisions. Initially, the subcutaneous connective tissue of the posterior lumbar site was dissected. Then, the 14-gauge needle was inserted through the inter-lamina space at a location 2.0 cm inferior and lateral to the midline, with a 10-degree angle toward the midline. In lieu of the conventional medial lumbar puncture via the vertebral inter-spinous space, we performed this lateral lumbar puncture via the vertebral inter-lamina space. After performing a lumbar puncture and inserting the spinal catheter into the subarachnoid space, the cerebral spinal fluid outflow from the spinal catheter was ascertained. Then, the indwelling valve system was then positioned on the lumbar posterior side of the paravertebral spinal muscle beneath the skin of the lower back. Next, laparotomy was performed. We divided the muscles using a blunt dissector. The lateral abdominal wall comprises three layers of muscle: external oblique, internal oblique, and transverse abdominal. These three muscle layers lack the tough fascia of the anterior abdominal muscle. They can be easily divided with a blunt dissector. Following the division of these muscle layers, the peritoneal layer is observed. We positioned the catheter at the bottom of the abdominal cavity and then sutures to close the peritoneal space.16,17) The primary component of the valve system was a CODMAN CERTAS Plus programmable valve with a SiphonGuard system (Codman Neuro, MA, USA), and the initial valve pressure was determined based on the patient's body weight and height before being adjusted based on the patient's activities and clinical manifestations as documented during periodic outpatient visits.18)
Assessment outcomes
All patients were evaluated for postoperative complications, MMSE, iNPH grading scale, ICDSC score, and length of postoperative hospital stay when discharged. Logistic regression univariate analyses of the following variables were performed in terms of postoperative hospital stay and postoperative ICDSC: age, anesthetic techniques, preoperative MMSE, surgical time, and preoperative iNPHGS. In describing demographic characteristics, p-values were obtained via linear regression. Each statistical test was set to be significant at p < 0.05 (two-sided p-value). SAS software (version 9.4; SAS Institute, Inc., Cary, North Carolina) was used for all statistical analyses.
All procedures performed in this study were in accordance with the ethical standards of our institutional and national research committee and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. We used spinal anesthesia instead of standard general anesthesia after the patients and their first-degree relatives received a full explanation of both forms of anesthesia. We also obtained approval from the ethics committee of our institution for this study. Before inclusion in the study, written informed consent was obtained from all individual participants and/or their first-degree relatives.
Results
Table 1 summarizes the patient characteristics and outcomes.
Table 1.
Patient characteristics
| Patient characteristics | Total (n = 79) | General anesthesia (n = 43) | Spinal anesthesia (n = 36) |
|---|---|---|---|
| Age at LPS (years) | 78.0 (10.0) | 78.0 (9.5) | 78.5 (10.0) |
| Sex (M/F) | 47/32 | 30/13 | 17/19 |
| BMI | 22.3 (5.2) | 24.9 (4.8) | 22.6 (4.8) |
| ASA-PS | 2 (0) | 2 (0) | 2 (0) |
| Preoperative MMSE | 24 (6.5) | 24 (5.5) | 24 (8) |
| Preoperative iNPHGS | 5 (2) | 5 (2.5) | 5 (1.25) |
| Preoperative ICDSC | 0 (1) | 0 (1) | 0 (1) |
| Postoperative findings | |||
| Surgical time (minutes) | 30 (14.5) | 30 (13) | 31 (16) |
| Postoperative MMSE | 25 (8.5) | 25 (7.5) | 24 (10) |
| Postoperative iNPHGS | 4 (2) | 4 (2) | 4 (2) |
| Postoperative ICDSC | 0 (1.5) | 0 (2) | 0 (1) |
| Postoperative hospital stay (days) | 11 (3.5) | 11 (4) | 10 (3) |
| Follow-up (years) | 2.5 (2) | 3.5 (2) | 1.75 (1.5) |
| Complications | |||
| Chronic subdural hematoma | 2 | 1 | 1 |
| Aspiration pneumonia | 2 | 2 | 0 |
Data are presented as median and interquartile range; median (interquartile range).
Abbreviations: ASA-PS: American Society of Anesthesiologists physical status, BMI: body mass index, F: female, ICDSC: intensive care delirium screening checklist, iNPHGS: idiopathic normal pressure hydrocephalus grading scale, LPS: lumboperitoneal shunt, M: male, MMSE: Mini-Mental State Examination
Patient characteristics
There were 43 patients in the general anesthesia group. The preoperative ASA-PS was 2 (0) (median [interquartile range]), MMSE was 24 (5.5), iNPHGS was 5 (2.5), and ICDSC was 0 (1). There were 36 patients in the spinal anesthesia group. The preoperative ASA-PS was 2 (0) (median [interquartile range]), MMSE was 24 (8), iNPHGS was 5 (1.25), and ICDSC was 0 (1). In one patient, we had to switch from spinal anesthesia to general anesthesia during the surgery because severe intestinal adhesion was found, which necessitates that we cut the intestinal membrane, thereby creating adequate space to insert the shunt tube and complete the LPS.
Outcomes and data analyses
The general anesthesia group's surgical time was 30 (13) min. The postoperative MMSE at discharge was 25 (7.5), the iNPHGS was 4 (2), and ICDSC was 0 (2). The length of the hospital stay was 11 (4) days. One patient presented with a thin chronic subdural hematoma, which resolved after the adjustment in valve pressure. Two patients had mild aspiration pneumonia after the surgery; one quickly recovered in response to oral antibiotic therapy, and the other required a week of intravenous antibiotic administration before the infection resolved. In the spinal anesthesia group, the spinal anesthesia group's surgical time was 31 (16) min. The postoperative MMSE at discharge was 24 (10), the iNPHGS was 4 (2), and ICDSC was 0 (1). The length of the hospital stay was 10 (3) days. One patient presented with a thin chronic subdural hematoma, which resolved following the adjustment in valve pressure. After the surgery, none of our patients developed respiratory complications. Logistic regression univariate analyses on the postoperative hospital stay showed a significant difference in the anesthetic technique (general anesthesia or spinal anesthesia). However, no significant difference regarding the postoperative delirium score was found (Tables 2 and 3).
Table 2.
Logistic regression univariate analyses of postoperative hospital stay
| Factor | 95% CI | p value |
|---|---|---|
| Age at LPS | 0.854–1.555 | 0.3523 |
| Anesthetic technique | 1.193–6.076 | 0.0171* |
| Preoperative MMSE | 0.779–1.908 | 0.3870 |
| Surgical time | 0.982–1.362 | 0.0821 |
| Preoperative iNPHGS | 0.922–1.746 | 0.1444 |
CI: confidence interval, iNPHGS: idiopathic normal pressure hydrocephalus grading scale, LPS: lumboperitoneal shunt surgery, MMSE: Mini-Mental State Examination, *significant difference
Table 3.
Logistic regression univariate analyses of postoperative ICDSC
| Factor | 95% CI | p value |
|---|---|---|
| Age at LPS | 0.817–9.660 | 0.1010 |
| Anesthetic technique | 0.237–158.185 | 0.2748 |
| Preoperative MMSE | 0.220–5.080 | 0.9443 |
| Surgical time | 0.888–1.482 | 0.2939 |
| Preoperative iNPHGS | 0.258–1.559 | 0.3208 |
CI: confidence interval, ICDSC: intensive care delirium screening checklist, iNPHGS: idiopathic normal pressure hydrocephalus grading scale, LPS: lumboperitoneal shunt surgery, MMSE: Mini-Mental State Examination
Discussion
Since the publication of the guidelines for the management of iNPH (the first edition was published in 2004, the second edition was in 2012, and the third edition was in 2021), several patients with iNPH have been undergoing shunt surgery in aging societies, including Japan.4,10,11) Nevertheless, treating iNPH without any complications is sometimes difficult.5,19,20) Factors that increase risk after shunt surgery include advanced age, preoperative dementia, and multiple co-existing internal diseases.5,6) To decrease postoperative complications, a low-impact shunt procedure that causes little change in patients' status should be mandatory.
LPS is an extracranial procedure that can reduce intracranial complications. After a multicenter prospective cohort study in Japan (multicenter trial to assess lumboperitoneal shunt [LPS] implantation in patients with idiopathic normal pressure hydrocephalus [iNPH] [SINPHONI-2]) demonstrated that LPS is not statistically inferior to the VPS procedure in patients with iNPH, many patients have since been undergoing LPS in Japan.2,10) LPS has advantages over VPS, particularly in elderly patients with iNPH, to avoid general anesthesia-related risks such as respiratory dysfunction. Because LPS does not require manipulation of the upper part of the body, performing LPS under neuraxial anesthesia, such as spinal anesthesia, is possible. Conversely, the potentially problematic feature of LPS compared with VPS entails its spinal tube insertion via calcified narrow inter-spinous space or excessive drainage syndrome causing postoperative chronic subdural hematoma, whereas these issues are gradually showing resolution based on the development of valve systems as well as a wide range of pressure control strategies.18,19,21,22)
Neuraxial anesthesia, such as spinal and epidural anesthesia, and local anesthesia decreased postoperative complications such as postoperative aspiration pneumonia or postoperative delirium compared with general anesthesia in many areas such as cardiovascular or orthopedic fields.9,23-27) These reductions are associated with lower hospital mortality and shorter length of hospitalization.9,27,28) Although there was no difference between the two groups in terms of postoperative delirium score, LPS under spinal anesthesia was significantly decreased the postoperative hospital stay and advantageous in decreasing postoperative respiratory complications, which may have contributed to a shorter hospital stay in this group. Since spinal anesthesia is used so often, we opted for it for this study instead of epidural or local anesthesia. Although there is no report regarding an anesthetic approach to LPS, epidural or local anesthesia might have the potential to be an alternative method to general anesthesia.23,24,27) Table 4 summarizes the advantages and disadvantages of each method.8,9,23-26,29-32)
Table 4.
Advantages and disadvantages of each anesthetic technique
| Anesthetic technique | Advantages | Disadvantages | |
|---|---|---|---|
| General anesthesia | Immediate onset and is easily maintained without time restriction | Postoperative nausea | |
| Broad access to vital change | Postoperative respiratory complication | ||
| A versatile method for all patients, even in cases with BPSD | Postoperative cognitive decline | ||
| Neuraxial anesthesia | Spinal | Lower postoperative respiratory complication | Perioperative hypotension |
| Lower postoperative delirium | Spinal root injury or cauda equina syndrome | ||
| Earlier postoperative oral intake | Post-dural puncture headache | ||
| Epidural | Favorable hemodynamic profile | Late-onset and limited duration of anesthetic action | |
| Spinal root injury or epidural hematoma | |||
| Total spinal anesthesia from an erroneous dural puncture | |||
| Local infiltration anesthesia | No suppression of the autonomic nerve reflexes | ||
| Incomplete range of anesthetic action | |||
| Need for the cooperation of the patient | |||
BPSD: behavioral and psychological symptoms of dementia
Although useful in many cases, spinal anesthesia has limitations, such as a shorter duration of action and the need for patient cooperation. In this study, a patient with severe abdominal adhesions due to multiple abdominal operations required a transition from spinal to general anesthesia during surgery. In the event of unanticipated findings necessitating additional strategies or a prolonged surgical time, surgeons should be prepared to switch from spinal anesthesia to general anesthesia and apply the optimal approach to complete the surgery. Although we had no patient who required general anesthesia due to restlessness, the hyperactivity behaviors of patients with dementia (e.g., irritability, agitation, aggression, and disinhibition) require general anesthesia for the safety of the surgery.5,6) For the aforementioned reasons, preoperative evaluation of all the patients and selection of the most effective anesthesiologic procedures are required.
Limitations
This present study is limited by the small number of patients and its retrospective design. These variables may affect the results and reduce the validity of our conclusion.
Conclusions
LPS under spinal anesthesia had the benefit of reducing respiratory complications and the length of postoperative hospital stay. In elderly patients, this method would serve as an alternative to the conventional LPS under general anesthesia.
Funding
No funding was received for this research.
Ethical Approval
All procedures performed in this study were in accordance with the ethical standards of our institutional committee, national research committee, and the 1964 Helsinki Declaration with its later amendments or comparable ethical standards. This study also obtained approval from the ethics committee of our institution. All data identifying the patients were anonymized. This article was conducted and described using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.
Conflicts of Interest Disclosure
All authors confirm that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements) or nonfinancial interests (such as personal or professional relationships, affiliations, knowledge, and beliefs) in the subject matter or materials discussed in this manuscript.
Acknowledgments
We thank Dr. Masahiro Tujiura (MD, PhD, Department of Gastroenterological Surgery, Saiseikai Shiga Hospital) for assistance in performing the laparotomy procedure on the patient with severe intestinal adhesion.
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