Anaesthesia in Elderly Patients with Neurodegenerative Disorders

Preoperative Management of Medications for Neurologic Diseases: Society for Perioperative Assessment and Quality Improvement Consensus Statement

Neurologic diseases are prevalent in patients undergoing invasive procedures; yet, no societal guidelines exist as to best practice in management of perioperative medications prescribed to treat these disorders. The Society for Perioperative Assessment and Quality Improvement tasked experts in internal medicine, anesthesiology, perioperative medicine, and neurology to provide evidence-based recommendations for preoperative management of these medications. The aim of this review is not only to provide consensus recommendations for preoperative management of patients on medications for neurologic disorders, but also to serve as an educational guide to perioperative clinicians. While, in general, medications for neurologic disorders should be continued preoperatively, an individualized approach may be needed in certain situations (eg, holding anticonvulsants on day of surgery if electroencephalographic mapping is planned during epilepsy surgery). Pertinent interactions with commonly used drugs in anesthesia practice, as well as considerations for targeted laboratory testing or perioperative drug substitutions, are addressed as well.

Neuroprotective Role of Polyphenols in Treatment of Neurological Disorders: A Review

: The most frequent illnesses characterized by the gradual malfunctioning of brain neurons are neurodegenerative disorders (NDs). Genetic mutations and a range of biological processes can produce NDs. Alzheimer's disease (AD), Parkinson's disease (PD), and Multiple Sclerosis (MS) are all related to oxidative stress (OS). Reduced brain activity has become a greater health threat with a growing elderly population. It causes some pathophysiological alterations and is an important risk factor for a range of neurodegenerative illnesses. An increase in reactive oxygen species (ROS) can cause neuronal cell death, and it is thus essential to control ROS levels to maintain normal neuronal activity. Synthetic medicines are often used to treat neurological disorders; however, harmful effects have been reported. Multiple bodies of research have shown the effectiveness of polyphenols in the treatment of various NDs due to their negligible side effects. This review article describes the neuroprotection effects of polyphenols such as resveratrol, epigallocatechin-3-gallate, curcumin, and quercetin, as well as the signaling pathways and immune response controls through polyphenols.

Do we really improve life quality after total knee arthroplasty in patients with Parkinson's disease?

INTRODUCTION

The knee in Parkinson's disease (PD) patients is a problematic joint due to pain, stiffness and gait instability. The aim of this study is to evaluate the functional outcome and degree of pain relief achieved after total knee arthroplasty (TKA) in PD patients.

MATERIALS AND METHODS

This is a retrospective review of 26 PD patients (32 knees) with osteoarthritis who underwent a TKA between 1994 and 2013. Comorbidities, anesthetic procedures and complications were recorded. Patient functional status was assessed with the Knee Society Function Score (KFS) and the Knee Society Score (KSS). PD stage was classified with the Hoehn and Yahr Scale.

RESULTS

The mean follow-up was 3.5 years (range 2-9). The mean age was 71 years (range 61-83) with a mean time since PD diagnosis of 11.8 years (range 4-24). PD severity on the Hoehn and Yahr Scale was 1.5 points before surgery and 2 points postoperatively. Pain on the visual analogic scale improved from 8 points preoperatively to 5 points at 1-year follow-up; function improved from 32 (range 20-45) to 71 (range 50-81) and from 34 (range 28-52) to 59 (range 25-76) on the KSS and KFS, respectively. The mean postoperative hospital stay was 9.8 days (range 5-21). Confusion and flexion contracture were the most frequent perioperative complications.

CONCLUSION

TKA successfully provided pain relief in PD patients. However, the functional outcome is related to disease progression and, therefore, variable. Perioperative complications are difficult to avoid and manage.

Spinal versus General Anesthesia for Patients with Parkinson's Disease

Background

Anesthesiologists prefer using general anesthesia (GA) in Parkinson’s disease (PD). However, GA may mask neurological symptoms in the intraoperative period and exacerbate them postoperatively. Furthermore, the anesthetics used in GA have clear interactions with the drugs used to control PD. On the other hand, drugs used in spinal anesthesia (SA) might be safer for patients with PD. The aim of this study is to evaluate the effect of SA and GA in patients with PD who underwent hip fracture repairs.

Methods

Retrospectively, we identified those patients with PD who were admitted due to hip joint fracture. The following information were obtained: demographics, preoperative assessment information of the patients, type of anesthesia, and types of fractures and orthopedic procedures. In addition, intraoperative and postoperative complications were studied. The patients were divided based on the type of anesthesia received and were compared.

Results

Ten (8 males) patients with PD who underwent hip fracture surgery included in the study. Six patients received SA and 4 patients received GA. The mean age was 73.2 years. The preoperative assessment was not significant for all patients. Postoperatively, within the inpatient period, 3 out of 4 patients received GA developed complications (two atelectasis and urinary tract infection) while no patient developed complication from the SA group. Postoperative outpatient complications within one-month included 3 out of 4 cases in the GA group and only one complication in the SA group. The mean hospitalization period was 9 days for patients received GA and 5.8 days for patients received SA.

Conclusion

This study reported less perioperative complications in the SA. Accordingly, further investigations and rp-randomized controlled trials evaluating various anesthetic techniques or drugs are needed.

Comparison of recovery profiles in patients with Parkinson's disease for 2 types of neuromuscular blockade reversal agent following deep brain stimulator implantation

As an anesthetic reversal agent, there are concerns with cholinesterase inhibitors regarding worsening of Parkinson's disease (PD)-related symptoms. Sugammadex, a relatively new reversal agent, does not inhibit acetylcholinesterase and does not require co-administration of an antimuscarinic agent. The present study compared the recovery profiles of 2 agents initially administered for reversal of neuromuscular blockade in patients with advanced PD who underwent deep brain stimulator implantation.A total of 121 patients with PD who underwent deep brain stimulator implantation were retrospectively analyzed. Patients were divided into 1 of 2 groups according to the type of neuromuscular blockade reversal agent (pyridostigmine vs sugammadex) initially administered. Recovery profiles reflecting time to extubation, reversal failure at first attempt, and hemodynamic stability, including incidence of hypertension or tachycardia during the emergence period, were compared.Time to extubation in the sugammadex group was significantly shorter (P < .001). In the sugammadex group, reversal failure at first attempt did not occur in any patient, while it occurred in seven (9.7%) patients in the pyridostigmine group (P = .064), necessitating an additional dose of pyridostigmine (n = 3) or sugammadex (n = 4). The incidence of hemodynamic instability during anesthetic emergence was significantly lower in the sugammadex group than in the pyridostigmine group (P = .019).Sugammadex yielded a recovery profile superior to that of pyridostigmine during the anesthesia emergence period in advanced PD patients. Sugammadex is also likely to be associated with fewer adverse effects than traditional reversal agents, which in turn would also improve overall postoperative management in this patient population.

Hospital Management of Parkinson Disease Patients

Management of patients with Parkinson disease (PD) during inpatient hospital stays is complex and poses unique challenges for physicians and ancillary staff. Patients with PD have a high risk of complications, encephalopathy, and prolonged hospital stay. Early recognition of complications and implementation of rehabilitation strategies along with appropriate management of medications are critical to improve outcomes. Patients with PD can exhibit worsening mobility and balance, insomnia, orthostatic hypotension, multiple neuropsychiatric symptoms, and gastrointestinal dysfunction while hospitalized. This review summarizes the specific in-hospital concerns observed in patients with PD and discusses potential treatment approaches.

Considerations for general anaesthesia in Parkinson's disease

Parkinson's disease is a common neurodegenerative disorder in the elderly which when present has a significant influence on surgical management. These patients necessitate additional perioperative and anaesthetic considerations across disease specific domains as well as in relation to the respiratory and cardiovascular systems. This brief review focuses on the factors which contribute to perioperative morbidity, including the use of medications that may exacerbate symptoms or adversely interact with treatments for Parkinson's disease. Recommended dosing practices to reduce complications during hospitalisation are covered. In addition, recent concerns regarding anaesthetic exposure in early childhood as a risk factor for the development of Parkinson's disease are discussed in light of data from animal models of anaesthetic neurotoxicity and epidemiological studies.

Total Knee Arthroplasty In Patients With Parkinson's Disease- A Critical Analysis of Available Evidence

Background:

In this era of modern medicine, there is an increase in life expectancy and thereby an ageing population. Among this group one of the most common neurological disorder is Parkinson disease and one of the most common operation done in elderly population is a total joint arthroplasty. But total joint arthroplasty in Parkinson disease is a relatively uncommon entity. There is sparse literature available with regards to total knee arthroplasty (TKA) in Parkinson disease. This review focusses on the necessity, complications and previous experiences on TKA in PD based on the literature available.

Method:

The review was conducted after a series of advanced search in the following medical databases; Pub med, Biomed central, Cochrane and Google scholar for articles related to total knee replacement in patients with Parkinson’s disease. The following keywords were used; Total knee arthroplasty, Parkinson’s disease, Hoehn and Yahr, Flexion Contracture.

Results:

The review indicates that the functional outcome is comparable to that of controls in immediate post-operative phase, one year and three-year phase, but the long term functional outcome seems to deteriorate significantly.

Conclusion:

Total knee arthroplasty can serve as an effective tool in alleviating pain in short term as well as long term periods, whereas the functional outcome seems to deteriorate post operatively on a long-term basis. Nevertheless, TKA in PD is a challenging situation, thereby necessitating a holistic approach with the efforts from various specialists needed at each stage to ensure a successful operation.

Remifentanil Requirement for Inhibiting Responses to Tracheal Intubation and Skin Incision Is Reduced in Patients With Parkinson's Disease Undergoing Deep Brain Stimulator Implantation

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease affecting the quality of life in the elderly. We speculated that PD patients might have abnormal pharmacodynamics due to the degenerative neural system, and the present study was performed to investigate the pharmacodynamics of remifentanil in PD patients.

MATERIALS AND METHODS

Two arms of patients were recruited, including 31 PD patients undergoing pulse generator placement after deep brain stimulator implantation and 31 pair-controlled patients undergoing intracranial surgery without PD (NPD). Patients were anesthetized with target-controlled infusion of propofol and remifentanil. The effective concentration of remifentanil to inhibit responses to intubation and skin incision in 50% and 95% patients (EC50 and EC95) was determined by the up and down method.

RESULTS

Demographic data, bispectral index, and hemodynamic values were similar between the PD and the NPD groups. The average remifentanil concentration used in the PD group for tracheal intubation is significantly lower than in the NPD group (P<0.001). The EC50 for inhibiting the response to tracheal intubation were 1.86 ng/mL (95% confidential interval [CI], 1.77-1.96 ng/mL) in the PD group and 3.20 ng/mL (95% CI, 3.13-3.27 ng/mL) in the NPD group. The average remifentanil concentration used in the PD group for skin incision is significantly lower than in the NPD group (P<0.001). EC50 for inhibiting the response to skin incision were 2.17 ng/mL (95% CI, 2.09-2.25 ng/mL) in the PD group and 3.09 ng/mL (95% CI, 3.02-3.17 ng/mL) in the NPD group.

CONCLUSIONS

The remifentanil concentrations required for inhibiting responses to tracheal intubation and skin incision are reduced markedly in PD patients undergoing pulse generator placement (NCT01992692).

Propofol requirement for induction of unconsciousness is reduced in patients with Parkinson's disease: a case control study

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease, but whether the neurodegenerative process influences the pharmacodynamics of propofol remains unclear. We aimed to evaluate the effect of PD on pharmacodynamics of propofol. A total of 31 PD patients undergoing surgical treatment (PD group) and 31 pair-controlled non-PD patients undergoing intracranial surgery (NPD group) were recruited to investigate the propofol requirement for unconsciousness induction. Unconsciousness was induced in all patients with target-controlled infusion of propofol. The propofol concentration at which unconsciousness was induced was compared between the two groups. EC₅₀ and EC₉₅ were calculated as well. Demographic data, bispectral index, and hemodynamic values were comparable between PD and NPD groups. The mean target concentration of propofol when unconsciousness was achieved was 2.32 ± 0.38 μg/mL in PD group, which was significantly lower than that in NPD group (2.90 ± 0.35 μg/mL). The EC₅₀ was 2.05 μg/mL (95% CI: 1.85–2.19 μg/mL) in PD group, much lower than the 2.72 μg/mL (95% CI: 2.53–2.88 μg/mL) in NPD group. In conclusion, the effective propofol concentration needed for induction of unconsciousness in 50% of patients is reduced in PD patients. (This trial is registered with NCT01998204.)

Slowing the progression of Alzheimer's disease; what works?

Alzheimer's disease (AD) is an age-related progressive dementia, which is increasing in prevalence world-wide. Typically affecting short-term memory at onset, this devastating illness advances to impair all aspects of cognition, as well as non-cognitive domains. Although much effort has been made in recent years to develop disease-modifying treatments, medications which provided promising results in pre-clinical research have so far faltered in human clinical trials. Attention has recently shifted into trying to identify preventative measures that may delay the onset of the illness. Preventative factors include physical activity, proper diet, cognitive stimulation and the management of conditions such as hypertension, diabetes and obesity. However, it remains imperative to identify approaches that may help patients already diagnosed with the illness. Alongside pharmacological research, much work has been done on uncovering strategies which may slow down the progression of AD. This review aims to summarize evidence supporting or refuting methods impacting on the progression of the disease. AD remains a chronic and serious condition, therefore any intervention delaying the onset of moderate/severe symptoms will have a significant impact on patients and their families.

Perioperative management of patients with Parkinson's disease

Parkinson's disease is the second most common neurodegenerative disease worldwide, leading to a wide range of disability and medical complications. Managing patients with Parkinson's disease in the perioperative hospital setting can be particularly challenging. Suboptimal management can lead to medical complications, prolonged hospital stays, and delayed recovery. This review aims to address the most important issues related to caring for patients with Parkinson's disease perioperatively who are undergoing emergent or planned general surgery. It also intends to help hospitalists, internists, and other health care providers mitigate potential in-hospital morbidity and prevent prolonged recovery. Challenges in managing patients with Parkinson's disease in the perioperative hospital setting include disruption of medication schedules, "nothing by mouth" status, reduced mobility, and medication interactions and their side effects. Patients with Parkinson's disease are more prone to immobility and developing dysphagia, respiratory dysfunction, urinary retention, and psychiatric symptoms. These issues lead to higher rates of pneumonia, urinary tract infections, deconditioning, and falls compared with patients without Parkinson's disease, as well as prolonged hospital stays and a greater need for post-hospitalization rehabilitation. Steps can be taken to decrease these complications, including minimizing nothing by mouth status duration, using alternative routes of drugs administration when unable to give medications orally, avoiding drug interactions and medications that can worsen parkinsonism, assessing swallowing ability frequently, encouraging incentive spirometry, performing bladder scans, avoiding Foley catheters, and providing aggressive physical therapy. Knowing and anticipating these potential complications allow hospital physicians to mitigate nosocomial morbidity and shorten recovery times and hospital stays.

Clinical problems in the hospitalized Parkinson's disease patient: systematic review

The problems Parkinson's disease (PD) patients encounter when admitted to a hospital, are known to be numerous and serious. These problems have been inventoried through a systematic review of literature on reasons for emergency and hospital admissions in PD patients, problems encountered during hospitalization, and possible solutions for the encountered problems using the Pubmed database. PD patients are hospitalized in frequencies ranging from 7 to 28% per year. PD/parkinsonism patients are approximately one and a half times more frequently and generally 2 to 14 days longer hospitalized than non-PD patients. Acute events occurring during hospitalization were mainly urinary infection, confusion, and pressure ulcers. Medication errors were also frequent adverse events. During and after surgery PD patients had an increased incidence of infections, confusion, falls, and decubitus, and 31% of patients was dissatisfied in the way their PD was managed. There are only two studies on medication continuation during surgery and one analyzing the effect of an early postoperative neurologic consultation, and numerous case reports, and opinionated views and reviews including other substitutes for dopaminergic medication intraoperatively. In conclusion, most studies were retrospective on small numbers of patients. The major clinical problems are injuries, infections, poor control of PD, and complications of PD treatment. There are many (un-researched) proposals for improvement. A substantial number of PD patients' admissions might be prevented. There should be guidelines concerning the hospitalized PD patients, with accent on early neurological consultation and team work between different specialities, and incorporating nonoral dopaminergic replacement therapy when necessary.

Care of patients with Parkinson's disease in the operating department

As our elderly population increases, theatre staff are frequently presented with the challenges of caring for patients with co-morbidities who are undergoing surgery. This article aims to educate the reader about Parkinson's disease, and suggest interventions that perioperative practitioners may want to consider in order to improve the patient's experience in the operating department.

Total knee arthroplasty and Parkinson disease: enhancing outcomes and avoiding complications

Total knee arthroplasty (TKA) is typically an extremely successful method of restoring pain-free function and providing good long-term outcomes for patients with end-stage knee disease. However, outcomes are less predictable in persons with Parkinson disease. The limited literature available and our experience lead us to conclude that complication rates in the perioperative and postoperative periods with TKA are comparatively high in persons with Parkinson disease. In addition, a good functional outcome is less certain than in the general population. For persons with Parkinson disease who require TKA, we propose an integrative, collaborative approach to avoid complications and optimize outcomes.

Preoperative assessment of adult patients for intracranial surgery

The preoperative assessment of the patient for neurosurgical and endovascular procedures involves the understanding of the neurological disease and its systemic presentation, and the requirements of the procedure. There is a wide spectrum of different neurosurgical disorders and procedures. This article provides an overview of the preoperative evaluation of these patients with respect to general principles of neuroanesthesia, and considerations for specific intracranial and vascular neurosurgical and interventional neuroradiological procedures.

Identification and management of deep brain stimulation intra- and postoperative urgencies and emergencies

Deep brain stimulation (DBS) has been increasingly utilized for the therapeutic treatment of movement disorders, and with the advent of this therapy more postoperative urgencies and emergencies have emerged. In this paper, we will review, identify, and suggest management strategies for both intra- and postoperative urgencies and emergencies. We have separated the scenarios into 1--surgery/procedure related, 2--hardware related, 3--stimulation-induced difficulties, and 4--others. We have included ten illustrative (and actual) case vignettes to augment the discussion of each issue.

Anesthetic management of patients with Huntington disease

BACKGROUND

Huntington disease (HD) is a rare autosomal dominant disease with symptoms of chorea, dystonia, incoordination, cognitive decline, and behavioral difficulties. Abnormal responses to anesthesia have been reported in case reports and raised concerns regarding the safety of anesthesia in this patient population.

METHODS

We performed a computerized search of the Mayo Clinic medical records database searching for patients with HD who underwent general anesthesia. Medical records were reviewed for anesthetic technique, medications used, and postoperative complications.

RESULTS

We identified 11 patients with genetically confirmed HD who underwent 17 general anesthetics. Psychiatric medication use was common, with 6 patients using antipsychotics, 7 patients using antidepressants, and 3 patients using benzodiazepines. Succinylcholine was used in 7 anesthetics, and nondepolarizing neuromuscular blocking drugs in 11 anesthetics, all without adverse effects. Patients had normal responses to induction and maintenance of anesthesia without adverse effects. Serious postoperative complications did not occur.

CONCLUSION

Contrary to previous case reports, we found that patients with HD have normal responses to general anesthesia. However, the anesthesiologist should be aware of interactions between anesthetics and psychiatric medications frequently used by these patients. Measures should also be taken to minimize the risk of pulmonary aspiration because bulbar dysfunction may be a manifestation of this disease.

Parkinson's disease and deep brain stimulator placement

Deep brain stimulation (DBS) has added to the comfort and quality of life for an increasing number of Parkinson's disease (PD) patients. The anesthesiologist needs to understand the pathophysiology of the disease, the surgical procedure, and its postoperative implications to most effectively manage these patients. This article examines the role of the anesthesiologist in the pre- and perioperative management of patients undergoing DBS procedures. In terms of the general anesthetic management of PD patients, it is clear that no simple anesthetic regimen exists. Anesthesiologists can provide the best care through preoperative assessment, maintenance of PD drug therapy, and avoidance of known precipitating agents.

Tremor entrainment by patterned low-frequency stimulation

High-frequency test stimulation for tremor suppression is a standard procedure for functional target localization during deep brain stimulation. This method does not work in cases where tremor vanishes intraoperatively, for example, due to general anaesthesia or due to an insertional effect. To overcome this difficulty, we developed a stimulation technique that effectively evokes tremor in a well-defined and quantifiable manner. For this, we used patterned low-frequency stimulation (PLFS), i.e. brief high-frequency pulse trains administered at pulse rates similar to neurons' preferred burst frequency. Unlike periodic single-pulse stimulation, PLFS enables one to convey effective and considerably greater integral charge densities without violation of safety requirements. In a computational investigation of an oscillatory neuronal network temporarily rendered inactive, we found that PLFS evokes synchronized activity, phase locked to the stimulus. While a stronger increase in the amount of synchrony in the neuronal population requires higher stimulus intensities, the portion of synchronously active neurons nevertheless becomes strongly phase locked to PLFS already at weak stimulus intensities. The phase entrainment effect of PLFS turned out to be robust against variations in the stimulation frequency, whereas enhancement of synchrony required precisely tuned stimulation frequencies. We applied PLFS to a patient with spinocerebellar ataxia type 2 (SCA2) with pronounced tremor that disappeared intraoperatively under general anaesthesia. In accordance with our computational results, PLFS evoked tremor, phase locked to the stimulus. In particular, weak PLFS caused low-amplitude, but strongly phase-locked tremor. PLFS test stimulations provided the only functional information about target localization. Optimal target point selection was confirmed by excellent post-operative tremor suppression.

Effect of age on brain oxygenation regulation during changes in position

INTRODUCTION

Reports indicate that brain regulation of oxygenation is inhibited in patients with low baseline oxyhemoglobin concentrations and that brain oxyhemoglobin concentrations are decreased with aging. The purpose of this study was to determine if regulation of brain oxygenation to changes in blood pressure is inhibited by normal aging.

METHODS

Brain oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations were determined from the forehead using a frequency domain near infrared spectroscopy in 27 healthy volunteers. Subjects were separated into two groups by age (20-39, n=16; 40-60, n=11). Brain hemoglobin and non-invasive blood pressure were measured in (1) supine, (2) sitting, (3) supine and (4) sitting positions with 10-min equilibration intervals between each determination. Statistical differences were determined by two way repeated measures analysis of variance.

RESULTS

Young subjects were 28+/-5 years (mean+/-S.D.) and older subjects were 48+/-6 years. In supine position, OHb and HHb were 28.4+/-8.3 and 15.4+/-2.4micromol/L, respectively, in young; 22.4+/-5.7 and 13.4+/-2.9micromol/L, respectively, in older subjects, both P<0.05 between groups. Changing position from supine to sitting decreased OHb 5% and increased HHb 5% with no difference between groups.

CONCLUSIONS

There was a small but significant decrease in OHb and an increase in HHb from supine to sitting position, and this effect was similar between young and older subjects. Regulation of brain oxygenation during modest decreases in blood pressure did not change in normal aging to 60 years compared to young adults.

Monitoring cerebral oxygen saturation in elderly patients undergoing general abdominal surgery: a prospective cohort study

BACKGROUND AND OBJECTIVES

The aim of this prospective, observational study was to evaluate changes in regional cerebral oxygen saturation (rSO2) and incidence of intraoperative cerebral desaturation in a cohort of elderly patients undergoing major abdominal surgery.

METHODS

rSO2 was continuously monitored on the left and right sides of the forehead in 60 patients older than 65 yr (35 males and 25 females; ASA II-III; age: 72 +/- 5 yr; without pre-existing cerebral pathology, and baseline Mini Mental State Examination (MMSE) score >23) undergoing sevoflurane anaesthesia for major abdominal, non-vascular surgery >2 h.

RESULTS

Baseline rSO2 was 63 +/- 8%; cerebral desaturation (rSO2 decrease <75% of baseline or <80% in case of baseline rSO2 <50%) occurred in 16 patients (26%). The MMSE decreased from 28 +/- 1 before surgery to 27 +/- 2 on 7th postoperative day (P = 0.05). A decline in cognitive function (decrease in MMSE score > or = 2 points one week after surgery as compared to baseline value) was observed in six patients without intraoperative cerebral desaturation (13.6%) and six patients who had intraoperative cerebral desaturation (40%) (P = 0.057) (odds ratio: 4.22; CI95%: 1.1-16). Median (range) hospital stay was 14 (5-41) days in patients with an area under the curve of rSO2 <50% (AUCrSO2<50%) >10 min%, and 10 (4-30) days in those with an AUCrSO2<50% <10 min% (P = 0.0005).

CONCLUSIONS

In a population of healthy elderly patients, undergoing non-vascular abdominal surgery cerebral desaturation can occur in up to one in every four patients, and the occurrence of cerebral desaturation is associated with a higher incidence of early postoperative cognitive decline and longer hospital stay.

Sedation during regional anesthesia: inhalation versus intravenous

PURPOSE OF REVIEW

Sedation of patients either with or without regional anesthesia is discussed to ascertain sedation requirements in the two groups. The differences between 'monitored anesthesia care' and conscious sedation are defined. Several current and promising methods with which we can evaluate a patient's degree or level of sedation are assessed. Also noted are safety concerns regarding monitoring solutions for patients undergoing monitored anesthesia care. Well established techniques, including some which are decidedly 'low tech', are examined. Several routes of intravenous administration are discussed along with patient variables. Sevoflurane sedation is mentioned with regards to administration, advantages and drawbacks.

RECENT FINDINGS

Several modalities have been studied for evaluation of a patient's level of sedation, some of which have little applicability in the operating room. Processed electroencephalographic monitoring has tremendous promise but is currently not reliable enough to assess sedation level. Sevoflurane has a role in sedation, providing the limitations are understood. One drawback of sevoflurane is its greater degree of disinhibition when compared with intravenous agents, necessitating conversion to general anesthesia.

SUMMARY

Evaluating the degree of patient sedation is a need that technology has yet to meet. Several techniques have been tried in intensive care units but have little utility in the operating room. Utilization of processed electroencephalogram waveforms has the greatest potential but is of limited value at the present time. Sevoflurane is demonstrated to have a limited role in sedation but may prove useful in specific circumstances.

Anesthesia for Functional Neurosurgery

The use of functional stereotactic neurosurgery is increasing for treatment of patients with movement disorders and other chronic illnesses. The anesthetic considerations include the influence of the anesthetic agents on the microelectrode recordings and stimulation testing of an awake patient. The purpose of this study was to review the anesthetic management and incidences of intraoperative complications during functional neurosurgery in our institution. One hundred seventy-eight patients underwent an ablative procedure (n = 6) or the insertion of deep brain stimulator (n = 172) under monitored anesthesia care for movement disorders (n = 124), chronic pain (n = 20), and other procedures (n = 34). Local anesthetic was used for head frame pin sites and burr holes. No sedation/analgesia was administered to 57 (32%) patients. One patient required conscious sedation and another general anesthesia for the entire procedure. The remainder received small increments (mean +/- SD) of propofol (113 +/- 73 mg), midazolam (1.6 +/- 0.8 mg), and/or fentanyl (93 +/- 55 mug). Intraoperative complications that occurred in 16% of the patients included seizures (n = 8), change in neurologic status (n = 5), airway obstruction (n = 2), and hypertension (n = 7). Functional neurosurgery can be performed with minimal anesthesia in many patients. Awareness and vigilance can improve the identification and early treatment of intraoperative complications such as seizures, loss of airway, and changes in the neurologic status.

Continuous Monitoring of Cerebral Oxygen Saturation in Elderly Patients Undergoing Major Abdominal Surgery Minimizes Brain Exposure to Potential Hypoxia

Elderly patients are more prone than younger patients to develop cerebral desaturation because of the reduced physiologic reserve that accompanies aging. To evaluate whether monitoring cerebral oxygen saturation (rSO(2)) minimizes intraoperative cerebral desaturation, we prospectively monitored rSO(2) in 122 elderly patients undergoing major abdominal surgery with general anesthesia. Patients were randomly allocated to an intervention group (the monitor was visible and rSO(2) was maintained at > or =75% of preinduction values; n = 56) or a control group (the monitor was blinded and anesthesia was managed routinely; n = 66). Cerebral desaturation (rSO(2) reduction <75% of baseline) was observed in 11 patients of the treatment group (20%) and 15 patients of the control group (23%) (P = 0.82). Mean (95% confidence intervals) values of mean rSO(2) were higher (66% [64%-68%]) and the area under the curve below 75% of baseline (AUCrSO2(2)< 75% of baseline) was lower (0.4 min% [0.1-0.8 min%]) in patients of the treatment group than in patients of the control group (61% [59%-63%] and 80 min% [2-144 min%], respectively; P = 0.002 and P = 0.017). When considering only patients developing intraoperative cerebral desaturation, a lower Mini Mental State Elimination (MMSE) score was observed at the seventh postoperative day in the control group (26 [25-30]) than in the treatment group (28 [26-30]) (P = 0.02), with a significant correlation between the AUCrSO(2) < 75% of baseline and postoperative decrease in MMSE score from preoperative values (r(2)= 0.25, P = 0.01). Patients of the control group with intraoperative cerebral desaturation also experienced a longer time to postanesthesia care unit (PACU) discharge (47 min [13-56 min]) and longer hospital stay (24 days [7-53] days) compared with patients of the treatment group (25 min [15-35 min] and 10 days [7-23 days], respectively; P = 0.01 and P = 0.007). Using rSO(2) monitoring to manage anesthesia in elderly patients undergoing major abdominal surgery reduces the potential exposure of the brain to hypoxia; this might be associated with decreased effects on cognitive function and shorter PACU and hospital stay.

Endoscopic and stereotactic neurosurgery

PURPOSE OF REVIEW

Review of the anesthetic considerations for neuroendoscopy and stereotactic procedures.

RECENT FINDINGS

Minimally invasive procedures are increasingly applied in novel ways in the diagnosis and treatment of neurological pathologies. Endoscopic third ventriculostomy, endoscopic shunt revisions and drainage of intraventricular hematoma using a neuroendoscope have become routine neurosurgical procedures. Stereotaxis has expanded its scope from simple brain biopsy to functional neurosurgery and psychiatry. While these procedures are 'minimally invasive', perioperative critical events may still occur.

SUMMARY

Vigilance in preoperative assessment and intraoperative monitoring is essential in minimizing perioperative morbidity and mortality in patients undergoing neuroendoscopic and stereotactic procedures.