Postoperative cognitive dysfunction (POCD) is a multifactorial adverse event most frequently in elderly patients. This study evaluated the effect of dexamethasone on POCD incidence after noncardiac ...and nonneurologic surgery.
One hundred and forty patients (ASA I-II; age 60-87 years) took part in a prospective phase III, double blind, randomized study involving the administration or not of 8 mg of IV dexamethasone before general anesthesia under bispectral index (BIS) between 35-45 or 46-55. Neuropsychological tests were applied preoperatively and on the 3rd, 7th, 21st, 90th and 180th days after surgery and compared with normative data. S100β was evaluated before and 12 hours after induction of anesthesia. The generalized estimating equations (GEE) method was applied, followed by the posthoc Bonferroni test considering P<0.05 as significant.
On the 3rd postoperative day, POCD was diagnosed in 25.2% and 15.3% of patients receiving dexamethasone, BIS 35-45, and BIS 46-55 groups, respectively. Meanwhile, POCD was present in 68.2% and 27.2% of patients without dexamethasone, BIS 35-45 and BIS 46-55 groups (p<0.0001). Neuropsychological tests showed that dexamethasone associated to BIS 46-55 decreased the incidence of POCD, especially memory and executive function. The administration of dexamethasone might have prevented the postoperative increase in S100β serum levels.
Dexamethasone can reduce the incidence of POCD in elderly patients undergoing surgery, especially when associated with BIS 46-55. The effect of dexamethasone on S100β might be related with some degree of neuroprotection.
www.clinicaltrials.gov NCT01332812.
The effect of interscalene block (ISB) on pulmonary function of obese participants has not been investigated. The goal of this study is to assess the association of obesity (body mass index BMI >29 ...kg/m vs BMI <25 kg/m) and change in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) after ISB in participants undergoing outpatient shoulder surgery.
This prospective, observational cohort study compared obese (BMI >29 kg/m) and normal-weight (BMI <25 kg/m) groups undergoing ISB for ambulatory shoulder surgery, on preblock and postblock FVC and FEV1, at 30 minutes postblock and in the postanesthesia care unit (PACU). The primary outcome in this study was FVC% change (percentage change from preblock to postblock values of FVC) at 30 minutes postblock in the supine position. Secondary outcomes included FVC% change at PACU and in the sitting position, FEV1% change (percentage change from preblock to postblock values of FEV1), FVC, FEV1, incidence of diaphragmatic paresis, modified Borg scale for perceived dyspnea, Richmond Agitation-Sedation Scale scores for sedation, and intraoperative airway events.
Fourteen participants were recruited to each group. The mean (standard deviation) BMI in the normal-weight and obese groups was 23 (1.7) and 33 (3.1) kg/m, respectively. ISB success rate was 100%. All participants demonstrated hemidiaphragmatic paresis after ISB. Compared to the normal-weight group, in the sitting position, the obese group had a significant decrease in FVC% change at 30 minutes (-30 10.5 vs -23 7.2, P = .046) and an FEV1% change in the PACU (-40 12.6 vs -27 13.9, P = .02). No difference was found for measurements taken in the supine position. A repeated-measures analysis demonstrated that, adjusted for position, there is no significant group effect on FVC% change or FEV1% change from 30 minutes to PACU. The 2 groups were not different in terms of breathlessness and sedation at 30 minutes (P = .67, P = .48, respectively) and in the PACU (P = .69, P > .99, respectively) nor in the occurrence of intraoperative airway events (P > .99).
ISB is associated with greater FVC and FEV1 reductions in obese participants undergoing shoulder surgery compared to normal-weight participants. Neither time (30 minutes versus PACU) nor position (sitting versus supine) affected this relationship. Despite these changes, obesity was not associated with increased clinical respiratory symptoms or events.
Regional anesthesia is increasing in popularity for ambulatory surgical procedures. Concomitantly, the prevalence of obesity in the United States population is increasing. The objective of the ...present investigation was to assess the impact of body mass index (BMI) on patient outcomes after ambulatory regional anesthesia.
This study was based on prospectively collected data including 9,038 blocks performed on 6,920 patients in a single ambulatory surgery center. Patients were categorized into three groups according to their BMI (<25 kg/m2, 25-29 kg/m2, > or =30 kg/m2). Block efficacy, rate of acute complications, postoperative pain (at rest and with movement), postoperative nausea and vomiting, rate of unscheduled hospital admissions, and overall patient satisfaction were assessed. Linear and logistic multivariable analyses were used to obtain the risk-adjusted effect of BMI on these outcomes.
Of all patients 34.8% had a BMI <25 kg/m2, 34.0% were overweight (BMI 25-29 kg/m2), and 31.3% were obese (BMI > or = 30 kg/m2). Patients with BMI > or =30 kg/m2 were 1.62 times more likely to have a failed block (P = 0.04). The unadjusted rate of acute complications was higher in obese patients (P = 0.001). However, when compared with patients with a normal BMI, postoperative pain at rest, unanticipated admissions, and overall satisfaction were similar in overweight and obese patients.
The present investigation shows that obesity is associated with higher block failure and complication rates in surgical regional anesthesia in the ambulatory setting. Nonetheless, the rate of successful blocks and overall satisfaction remained high in patients with increased BMI. Therefore, overweight and obese patients should not be excluded from regional anesthesia procedures in the ambulatory setting.
Limited information exists on the effects of temporary functional deafferentation (TFD) on brain activity after peripheral nerve block (PNB) in healthy humans. Increasingly, resting-state functional ...connectivity (RSFC) is being used to study brain activity and organization. The purpose of this study was to test the hypothesis that TFD through PNB will influence changes in RSFC plasticity in central sensorimotor functional brain networks in healthy human participants.
The authors achieved TFD using a supraclavicular PNB model with 10 healthy human participants undergoing functional connectivity magnetic resonance imaging before PNB, during active PNB, and during PNB recovery. RSFC differences among study conditions were determined by multiple-comparison-corrected (false discovery rate-corrected P value less than 0.05) random-effects, between-condition, and seed-to-voxel analyses using the left and right manual motor regions.
The results of this pilot study demonstrated disruption of interhemispheric left-to-right manual motor region RSFC (e.g., mean Fisher-transformed z effect size at pre-PNB 1.05 vs. 0.55 during PNB) but preservation of intrahemispheric RSFC of these regions during PNB. Additionally, there was increased RSFC between the left motor region of interest (PNB-affected area) and bilateral higher order visual cortex regions after clinical PNB resolution (e.g., Fisher z between left motor region of interest and right and left lingual gyrus regions during PNB, -0.1 and -0.6 vs. 0.22 and 0.18 after PNB resolution, respectively).
This pilot study provides evidence that PNB has features consistent with other models of deafferentation, making it a potentially useful approach to investigate brain plasticity. The findings provide insight into RSFC of sensorimotor functional brain networks during PNB and PNB recovery and support modulation of the sensory-motor integration feedback loop as a mechanism for explaining the behavioral correlates of peripherally induced TFD through PNB.
Peripheral nerve stimulation has a long history in regional anesthesia. Despite the advent of ultrasound-guided peripheral nerve blockade, nerve stimulation remains a popular technique used alone or, ...now, in combination with ultrasound-guided techniques. In light of this evolving utility of nerve stimulation, this is an appropriate time to review the basic concepts and knowledge base of this historically important tool. Electrical nerve stimulation facilitates nerve localization, using threshold current as a surrogate for needle-to-nerve distance. Preferential activation of motor nerves is possible because motor nerve fibers are more readily activated with a shorter duration of current compared with sensory nerves. The association between current and needle-to-nerve distance predicts that less current is needed to evoke a motor response as the needle moves closer to the nerve. Thus, an elicited motor response at or below 0.5 mA is considered a common end point for successful neural blockade. However, current magnitude is neither 100% sensitive nor specific. Independent of technical ability, both the biological environment and the equipment used impact the current-distance relationship. Thus, successful electrical nerve stimulation is dependent on an anesthesiologist with a solid foundation in anatomy and a thorough understanding of electrophysiology.
Peripheral nerve blocks (PNBs) have an increasingly important role in ambulatory anesthesia and have many characteristics of the ideal outpatient anesthetic: surgical anesthesia, prolonged ...postoperative analgesia, and facilitated discharge. Critically evaluating the potential benefits and supporting evidence is essential to appropriate technique selection. When PNBs are used for upper extremity procedures, there is consistent opioid sparing and fewer treatment-related side effects when compared with general anesthesia. This has been demonstrated in the immediate perioperative period but has not been extensively investigated after discharge. Lower extremity PNBs are particularly useful for procedures resulting in greater tissue trauma when the benefits of dense analgesia appear to be magnified, as evidenced by less hospital readmission. The majority of current studies do not support the concept that a patient will have difficulty coping with pain when their block resolves at home. Initial investigations of outpatient continuous peripheral nerve blocks demonstrate analgesic potential beyond that obtained with single-injection blocks and offer promise for extending the duration of postoperative analgesia. The encouraging results of these studies will have to be balanced with the resources needed to safely manage catheters at home. Despite supportive data for ambulatory PNBs, most studies have been either case series or relatively small prospective trials, with a narrow focus on analgesia, opioids, and immediate side effects. Ultimately, having larger prospective data with a broader focus on outcome benefits would be more persuasive for anesthesiologists to perform procedures that are still viewed by many as technically challenging.
Ultrasound imaging has been used for performing single-injection peripheral nerve blocks and continuous catheters. One limitation with current technology is the inability to confirm the location of ...the needle or catheter tip. We describe a new needle and catheter design that permits distal tip visualization using color flow Doppler. An 18-gauge 100-mm insulated Tuohy needle and a 20-gauge 50-mm polyamide catheter (open tip) with a Teflon-coated steel stylet (B. Braun, Bethlehem, PA) were customized by adhering in place two piezoelectric actuators. These created 1-8 kHz vibrations when coupled to a function generator (FG502, Tektronix, Richardson, TX) and a 100 W audio amplifier (R3000, KLH, Sun Valley, CA). Mimicking a lateral popliteal fossa block, the needle and catheter were inserted into the leg of an unembalmed cadaver. When activated, the tip of each was highlighted in color when scanned in the short axis using the color Doppler mode of a two-dimensional ultrasound and a 12 MHz L38 probe (MicroMaxx, Sonosite, Bothell, WA). Vibration technology may be a useful adjunct while performing ultrasound-guided regional anesthesia. Further study evaluating its usefulness and safety in live tissue is warranted.
The prevalence of obesity and diabetes mellitus continues to rise in industrialized countries. The impact of diabetes on the practice of peripheral nerve block anesthesia, however, has not been fully ...elucidated. The authors retrospectively evaluated the influence of diabetes, body mass index (BMI), age, and sex on the success of supraclavicular block (SCB) placed with a landmark-based paresthesia technique.
The anesthetic records of 1858 consecutive patients who received an SCB were analyzed. Block success was documented solely on the day of surgery, without additional follow-up. Patients were categorized as diabetic (group D, n = 262) or nondiabetic (group ND, n = 1596). Block "success rate" (ie, general anesthesia not required to produce surgical conditions) was analyzed using multiple regression (multivariable linear and logistic) to assess the associations of diabetes and/or body mass index on successful surgical anesthesia.
Patients in group D were more likely (odds ratio, 3.3) to have a "successful" SCB for surgical anesthesia than were patients in group ND (P < 0.0001). Body mass index, age, and sex were not associated predictors of SCB "success."
We speculate that the "higher success" of SCB in patients with diabetes may be explained by: (i) higher sensitivity of diabetic nerve fibers to local anesthetics, (ii) possible unknown intraneural penetration before injection, and/or (iii) preexisting neuropathy with accompanying decreased sensation. In the absence of additional follow-up on these patients, these data should generate outcomes research addressing dose-response curves for patients with diabetes or at risk for diabetes.
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