Underweight but not overweight is associated with excess mortality in septic ICU patients.

BACKGROUND: Higher survival has been shown for overweight septic patients compared with normal or underweight patients in the past. This study aimed at investigating the management and outcome of septic ICU patients in different body mass index (BMI) categories in a large multicenter database. METHODS: In total, 16,612 patients of the eICU collaborative research database were included. Baseline characteristics and data on organ support were documented. Multilevel logistic regression analysis was performed to fit three sequential regression models for the binary primary outcome (ICU mortality) to evaluate the impact of the BMI categories: underweight (<18.5 kg/m2), normal weight (18.5 to < 25 kg/m2), overweight (25 to < 30 kg/m2) and obesity (≥ 30 kg/m2). Data were adjusted for patient level characteristics (model 2) as well as management strategies (model 3). RESULTS: Management strategies were similar across BMI categories. Underweight patients evidenced higher rates of ICU mortality. This finding persisted after adjusting in model 2 (aOR 1.54, 95% CI 1.15-2.06; p = 0.004) and model 3 (aOR 1.57, 95%CI 1.16-2.12; p = 0.003). No differences were found regarding ICU mortality between normal and overweight patients (aOR 0.93, 95%CI 0.81-1.06; p = 0.29). Obese patients evidenced a lower risk of ICU mortality compared to normal weight, a finding which persisted across all models (model 2: aOR 0.83, 95%CI 0.69-0.99; p = 0.04; model 3: aOR 0.82, 95%CI 0.68-0.98; p = 0.03). The protective effect of obesity and the negative effect of underweight were significant in individuals > 65 years only. CONCLUSION: In this cohort, underweight was associated with a worse outcome, whereas obese patients evidenced lower mortality. Our analysis thus supports the thesis of the obesity paradox.

ICU-Mortality in Old and Very Old Patients Suffering From Sepsis and Septic Shock.

Purpose: Old (>64 years) and very old (>79 years) intensive care patients with sepsis have a high mortality. In the very old, the value of critical care has been questioned. We aimed to compare the mortality, rates of organ support, and the length of stay in old vs. very old patients with sepsis and septic shock in intensive care. Methods: This analysis included 9,385 patients, from the multi-center eICU Collaborative Research Database, with sepsis; 6184 were old (aged 65-79 years), and 3,201 were very old patients (aged 80 years and older). A multi-level logistic regression analysis was used to fit three sequential regression models for the binary primary outcome of ICU mortality. A sensitivity analysis in septic shock patients (n = 1054) was also conducted. Results: In the very old patients, the median length of stay was shorter (50 ± 67 vs. 56 ± 72 h; p < 0.001), and the rate of a prolonged ICU stay was lower (>168 h; 9 vs. 12%; p < 0.001) than the old patients. The mortality from sepsis was higher in very old patients (13 vs. 11%; p = 0.005), and after multi-variable adjustment being very old was associated with higher odds for ICU mortality (aOR 1.32, 95% CI 1.09-1.59; p = 0.004). In patients with septic shock, mortality was also higher in the very old patients (38 vs. 36%; aOR 1.50, 95% CI 1.10-2.06; p = 0.01). Conclusion: Very old ICU-patients suffer from a slightly higher ICU mortality compared with old ICU-patients. However, despite the statistically significant differences in mortality, the clinical relevance of such minor differences seems to be negligible.

Changes in the augmentation index and postoperative orthostatic intolerance in orthopedic surgery: a prospective cohort study.

BACKGROUND: Postoperative orthostatic intolerance (OI) can be a major obstacle to early ambulation and its determinants are poorly understood. We aimed to study postoperative changes in vascular tone and their potential association with OI in various orthopedic surgical settings. METHODS: In this prospective cohort study, 350 patients undergoing total joint arthroplasty under neuraxial anesthesia or spine surgery under general anesthesia were enrolled. We determined the augmentation index (AI) as a measure of vascular tone and studied symptoms of OI using a validated questionnaire at various postoperative time points. RESULTS: The AI was significantly reduced postoperatively (at spinal resolution in patients with neuraxial anesthesia or two hours postoperatively in general anesthesia) compared with baseline values in all procedures and did not subsequently return to baseline throughout the postoperative period in the majority of patients [252/335 (75.2%); P < 0.001]. The majority [260/342 (76.0%); P < 0.001] of patients had postoperative symptoms of OI. Nevertheless, no association was found between postoperative change in AI from baseline and postoperative symptoms of OI. CONCLUSIONS: A significantly prolonged decrease in AI and symptoms of OI are common after orthopedic surgery. Nevertheless, an association between the two measures was not observed. While compensatory mechanisms may limit the influence of an AI decrease on symptoms of OI, more research is needed to understand the contributing factors and aid in the identification of patients at risk of OI.

Factors associated with hospital admission after rotator cuff repair: the role of peripheral nerve blockade.

STUDY OBJECTIVE: The objective was to analyze the impact of a peripheral nerve block in addition to general anesthesia on hospital admission after surgical rotator cuff repair. DESIGN: This was a population-based outcome study. The cost effectiveness of ambulatory rotator cuff repair relies on the discharge of patients on the day of surgery. As the impact of a peripheral nerve block in addition to general anesthesia on this outcome is unknown, we sought to elucidate this subject using population-based data. PATIENTS AND METHODS: Information on patients undergoing rotator cuff surgery under general anesthesia with or without the addition of a peripheral nerve block (GN vs G) from a retrospective database provided by Premier Perspective, Inc, Charlotte, NC (http://www.premierinc.com), was analyzed. Using multilevel multivariable regressions, we evaluated the independent impact of the type of anesthesia on the outcomes hospital admission, combined major complications, and increased hospital costs. RESULTS: We identified 27,201 patients who underwent surgical rotator cuff repair. Approximately 89% (24,240) of patients were discharged on the day of surgery, whereas 11% (2961) were admitted to the hospital. The admission rates for the GN group were 9.1% and 11.2% for the G group (P=.0001). The multivariable regression models showed that patients with the addition of a peripheral nerve block had 18% less risk of being admitted to the hospital (relative risk [RR]=0.82; 95% confidence interval [CI], 0.74-0.91; P=.0003) compared with those without this intervention. Differences in risk for combined major complications (RR=1.00; 95% CI, 0.83-1.20; P=.9751) or increased hospital costs (RR=0.97; 95% CI, 0.93-1.02; P=.2538) were nonsignificant. DISCUSSION: For patients undergoing surgical rotator cuff repair under general anesthesia, the addition of a peripheral nerve block may be associated with a reduction in the need for postoperative hospital admission after ambulatory surgery. Although the reason for this finding has to remain speculative, better pain control may play a role.

Impact of Melatonin on Sleep and Pain After Total Knee Arthroplasty Under Regional Anesthesia With Sedation: A Double-Blind, Randomized, Placebo-Controlled Pilot Study.

This pilot study explores sleep disruption after total knee arthroplasty and the impact of melatonin on sleep and postoperative pain. Sleep time was decreased on the last preoperative night and first two postoperative nights. Sleep efficiency was decreased on all three postoperative nights. Compared to placebo, melatonin increased sleep efficiency by 4.4% (mean; 95% CI -1.6, 10.4; P=0.150) and sleep time by 29 min (mean; 95% CI -2.0, 60.4; P=0.067). Melatonin appeared to have no effect on subjective sleep quality or daytime sleepiness, pain at rest or pain with standardized activity. In conclusion, sleep quality is impaired after total knee arthroplasty and exogenous melatonin does not appear to improve postoperative sleep or pain to a significant degree.

Blood Transfusions May Have Limited Effect on Muscle Oxygenation After Total Knee Arthroplasty.

BACKGROUND: Traditionally, blood transfusions in the perioperative setting are used to maintain adequate delivery of nutrients and oxygen to organs. However, the effect of blood administration on tissue oxygenation in the perioperative setting remains poorly understood. QUESTIONS/PURPOSES: The aim of this study was to determine changes in muscle tissue oxygenation saturation (SmO2) in response to perioperative blood transfusions. PATIENTS AND METHODS: Patients undergoing total knee arthroplasty were enrolled. SmO2, continuous hemoglobin (SpHb), stroke volume (SV), cardiac index, and standard hemodynamic parameters including heart rate (HR), mean arterial blood pressure (MAP), and arterial oxygen saturation (SO2) were recorded. To assess fluid responsiveness, a passive leg raise (PLR) test was performed before the transfusions were started. RESULTS: Twenty-eight patients were included in the analysis. Mean (±SD) SmO2 before transfusion was 63.18 ± 10.04%, SpHb was 9.27 ± 1.16 g/dl, and cardiac index was 2.62 ± 0.75 L/min/m(2). A significant increase during the course of blood transfusion was found for SmO2 (+3.44 ± 5.81% [95% confidence interval (CI) 1.04 to 5.84], p = 0.007), SpHb (0.74 ± 0.92 g/dl [95% CI 0.35 to 1.12], p < 0.001), and cardiac index (0.38 ± 0.51 L/min/m2 [95% CI 0.15 to 0.60], p = 0.002), respectively. However, the correlation between SmO2 and SpHb over the course of the transfusion was negligible (ρ = 0.25 [95% CI -0.03 to 0.48]). A similar lack of correlation was found when analyzing data of those patients who showed a positive leg raise test before the start of the transfusion (ρ = 0.37 [95% CI -0.11 to 0.84]). CONCLUSION: We detected a statistically significant increase in SmO2 during the course of a single unit blood transfusion compared to baseline. However, there was no evidence of a correlation between longitudinal SmO2 and SpHb measurements.

Subsartorial adductor canal vs femoral nerve block for analgesia after total knee replacement.

PURPOSE: Providing effective analgesia for total knee arthroplasty (TKA) patients remains challenging. Femoral nerve block (FNB) offers targeted pain control; however, its effect on motor function, related fall risk and impact on rehabilitation has been the source of controversy. Adductor canal block (ACB) potentially spares motor fibres of the femoral nerve, but the comparative effect of the two approaches has not yet been well defined due to considerable variability in pain perception. Our study compares both single-shot FNB and ACB, side to side, in the same patients undergoing bilateral TKA. METHODS: Sixty patients scheduled for bilateral TKA were randomised to receive ultrasound-guided FNB on one leg and ACB on the other, in addition to combined spinal epidural anaesthesia. The primary outcome was comparative postoperative pain in either extremity at six to eight, 24 and 48 hours postoperatively. Secondary comparative outcomes included motor strength (manually and via dynamometer), physical therapy milestones and patient satisfaction. RESULTS: While pain levels were lowest at six to eight hours postoperatively and increased thereafter (P < 0.001), no significant differences were seen between extremities at any time point with regard to pain in the quantitative comparison using visual analogue scale (VAS) scores (P = 0.4154), motor strength (P = 0.7548), physical therapy milestones or patient satisfaction. However, in the qualitative comparison, a significant proportion of patients reported the leg receiving ACB to be more painful than that receiving FNB at 24 h [50.9 % (n = 30) vs 25.42 % (n = 15), P = 0.0168)]. CONCLUSIONS: Although we could not confirm a benefit in motor function between ACB and FNB, given the equivalent analgesic potency combined with its potentially lower overall impact if neuropraxia should occur, ACB may represent an attractive alternative to FNB.

Tranexamic acid use and postoperative outcomes in patients undergoing total hip or knee arthroplasty in the United States: retrospective analysis of effectiveness and safety.

OBJECTIVE: To determine the effectiveness and safety of perioperative tranexamic acid use in patients undergoing total hip or knee arthroplasty in the United States. DESIGN: Retrospective cohort study; multilevel multivariable logistic regression models measured the association between tranexamic acid use in the perioperative period and outcomes. SETTING: 510 US hospitals from the claims based Premier Perspective database for 2006-12. PARTICIPANTS: 872,416 patients who had total hip or knee arthroplasty. INTERVENTION: Perioperative intravenous tranexamic acid use by dose categories (none, ≤ 1000 mg, 2000 mg, and ≥ 3000 mg). MAIN OUTCOME MEASURES: Allogeneic or autologous transfusion, thromboembolic complications (pulmonary embolism, deep venous thrombosis), acute renal failure, and combined complications (thromboembolic complications, acute renal failure, cerebrovascular events, myocardial infarction, in-hospital mortality). RESULTS: While comparable regarding average age and comorbidity index, patients receiving tranexamic acid (versus those who did not) showed lower rates of allogeneic or autologous transfusion (7.7% v 20.1%), thromboembolic complications (0.6% v 0.8%), acute renal failure (1.2% v 1.6%), and combined complications (1.9% v 2.6%); all P<0.01. In the multilevel models, tranexamic acid dose categories (versus no tranexamic acid use) were associated with significantly (P<0.001) decreased odds for allogeneic or autologous blood transfusions (odds ratio 0.31 to 0.38 by dose category) and no significantly increased risk for complications: thromboembolic complications (odds ratio 0.85 to 1.02), acute renal failure (0.70 to 1.11), and combined complications (0.75 to 0.98). CONCLUSIONS: Tranexamic acid was effective in reducing the need for blood transfusions while not increasing the risk of complications, including thromboembolic events and renal failure. Thus our data provide incremental evidence of the potential effectiveness and safety of tranexamic acid in patients requiring orthopedic surgery.

Perioperative pain control after total knee arthroplasty: An evidence based review of the role of peripheral nerve blocks.

Over the last decades, the number of total knee arthroplasty procedures performed in the United States has been increasing dramatically. This very successful intervention, however, is associated with significant postoperative pain, and adequate postoperative analgesia is mandatory in order to allow for successful rehabilitation and recovery. The use of regional anesthesia and peripheral nerve blocks has facilitated and improved this goal. Many different approaches and techniques for peripheral nerve blockades, either landmark or, more recently, ultrasound guided have been described over the last decades. This includes but is not restricted to techniques discussed in this review. The introduction of ultrasound has improved many approaches to peripheral nerves either in success rate and/or time to block. Moreover, ultrasound has enhanced the safety of peripheral nerve blocks due to immediate needle visualization and as consequence needle guidance during the block. In contrast to patient controlled analgesia using opioids, patients with a regional anesthetic technique suffer from fewer adverse events and show higher patient satisfaction; this is important as hospital rankings and advertisement have become more common worldwide and many patients use these factors in order to choose a certain institution for a specific procedure. This review provides a short overview of currently used regional anesthetic and analgesic techniques focusing on related implications, considerations and outcomes.

Perioperative outcomes and type of anesthesia in hip surgical patients: An evidence based review.

Over the last decades the demand for hip surgery, be it elective or in a traumatic setting, has greatly increased and is projected to expand even further. Concurrent with demographic changes the affected population is burdened by an increase in average comorbidity and serious complications. It has been suggested that the choice of anesthesia not only affects the surgery setting but also the perioperative outcome as a whole. Therefore different approaches and anesthetic techniques have been developed to offer individual anesthetic and analgesic care to hip surgery patients. Recent studies on comparative effectiveness utilizing population based data have given us a novel insight on anesthetic practice and outcome, showing favorable results in the usage of regional vs general anesthesia. In this review we aim to give an overview of anesthetic techniques in use for hip surgery and their impact on perioperative outcome. While there still remains a scarcity of data investigating perioperative outcomes and anesthesia, most studies concur on a positive outcome in overall mortality, thromboembolic events, blood loss and transfusion requirements when comparing regional to general anesthesia. Much of the currently available evidence suggests that a comprehensive medical approach with emphasis on regional anesthesia can prove beneficial to patients and the health care system.

Blood transfusions in total hip and knee arthroplasty: an analysis of outcomes.

BACKGROUND: Various studies have raised concern of worse outcomes in patients receiving blood transfusions perioperatively compared to those who do not. In this study we attempted to determine the proportion of perioperative complications in the orthopedic population attributable to the use of a blood transfusion. METHODS: Data from 400 hospitals in the United States were used to identify patients undergoing total hip or knee arthroplasty (THA and TKA) from 2006 to 2010. Patient and health care demographics, as well as comorbidities and perioperative outcomes were compared. Multivariable logistic regression models were fitted to determine associations between transfusion, age, and comorbidities and various perioperative outcomes. Population attributable fraction (PAF) was determined to measure the proportion of outcome attributable to transfusion and other risk factors. RESULTS: Of 530,089 patients, 18.93% received a blood transfusion during their hospitalization. Patients requiring blood transfusion were significantly older and showed a higher comorbidity burden. In addition, these patients had significantly higher rates of major complications and a longer length of hospitalization. The logistic regression models showed that transfused patients were more likely to have adverse health outcomes than nontransfused patients. However, patients who were older or had preexisting diseases carried a higher risk than use of a transfusion for these outcomes. The need for a blood transfusion explained 9.51% (95% CI 9.12-9.90) of all major complications. CONCLUSIONS: Advanced age and high comorbidity may be responsible for a higher proportion of adverse outcomes in THA and TKA patients than blood transfusions.

Inpatient falls after total knee arthroplasty: the role of anesthesia type and peripheral nerve blocks.

BACKGROUND: Much controversy remains on the role of anesthesia technique and peripheral nerve blocks (PNBs) in inpatient falls (IFs) after orthopedic procedures. The aim of the study is to characterize cases of IFs, identify risk factors, and study the role of PNB and anesthesia technique in IF risk in total knee arthroplasty patients. METHODS: The authors selected total knee arthroplasty patients from the national Premier Perspective database (Premier Inc., Charlotte, NC; 2006-2010; n = 191,570, >400 acute care hospitals). The primary outcome was IF. Patient- and healthcare system-related characteristics, anesthesia technique, and presence of PNB were determined for IF and non-IF patients. Independent risk factors for IFs were determined by using conventional and multilevel logistic regression. RESULTS: Overall, IF incidence was 1.6% (n = 3,042). Distribution of anesthesia technique was 10.9% neuraxial, 12.9% combined neuraxial/general, and 76.2% general anesthesia. PNB was used in 12.1%. Patients suffering IFs were older (average age, 68.9 vs. 66.3 yr), had higher comorbidity burden (average Deyo index, 0.77 vs. 0.66), and had more major complications, including 30-day mortality (0.8 vs. 0.1%; all P < 0.001). Use of neuraxial anesthesia (IF incidence, 1.3%; n = 280) had lower adjusted odds of IF compared with adjusted odds of IF with the use of general anesthesia alone (IF incidence, 1.6%; n = 2,393): odds ratio, 0.70 (95% CI, 0.56-0.87). PNB was not significantly associated with IF (odds ratio, 0.85 [CI, 0.71-1.03]). CONCLUSIONS: This study identifies several risk factors for IF in total knee arthroplasty patients. Contrary to common concerns, no association was found between PNB and IF. Further studies should determine the role of anesthesia practices in the context of fall-prevention programs.

Does the impact of the type of anesthesia on outcomes differ by patient age and comorbidity burden?

INTRODUCTION: Neuraxial anesthesia may provide perioperative outcome benefits versus general anesthesia in orthopedic surgical patients. As subgroup analyses are lacking, we evaluated the influence of the type of anesthesia on outcomes in patient groups of different age and the presence of cardiopulmonary disease. METHODS: Data from approximately 500 hospitals in the United States regarding total hip and total knee arthroplasties performed between 2006 and 2012 were accessed. Patients were categorized by age (ie, <65, 65-74, or ≥75 years) as well as the presence of cardiopulmonary disease. Resulting groups were compared with regard to patient, hospital, procedure, and comorbidity-related variables, as well as incidence of major perioperative complications. A multivariable logistic regression analysis was performed to assess the independent influence of the type of anesthesia on complications within each patient subgroup. RESULTS: We identified 795,135 records of patients who underwent total hip arthroplasty or total knee arthroplasty. The incidence of major complications was highest in the oldest patient group with cardiopulmonary disease (26.1%) and the lowest in the youngest group without cardiopulmonary disease (4.5%).Multivariable logistic regressions showed that neuraxial anesthesia was associated with decreased odds for combined major complications, need for intensive care services, and prolonged length of stay compared with general anesthesia in all patient subgroups. For patients without major cardiopulmonary comorbidities, the positive impact of neuraxial anesthesia increased with increasing age. CONCLUSIONS: Neuraxial anesthesia is associated with decreased odds for major complications and resource utilization after joint arthroplasty for all patient groups, irrespective of age and comorbidity burden.

Rheumatoid arthritis vs osteoarthritis in patients receiving total knee arthroplasty: perioperative outcomes.

There is a paucity of data available on perioperative outcomes of patients undergoing total knee arthroplasty (TKA) for rheumatoid arthritis (RA). We determined differences in demographics and risk for perioperative adverse events between patients suffering from osteoarthritis (OA) versus RA using a population-based approach. Of 351,103 entries for patients who underwent TKA, 3.4% had a diagnosis of RA. RA patients were on average younger [RA: 64.3 years vs OA: 66.6 years; P<0.001] and more likely female [RA: 79.2% vs OA: 63.2%; P<0. 001]. The unadjusted rates of mortality and most major perioperative adverse events were similar in both groups, with the exception of infection [RA: 4.5% vs. OA: 3.8%; P<0.001]. RA was not associated with increased adjusted odds for combined adverse events.

Dexmedetomidine added to ropivacaine extends the duration of interscalene brachial plexus blocks for elective shoulder surgery when compared with ropivacaine alone: a single-center, prospective, triple-blind, randomized controlled trial.

BACKGROUND AND OBJECTIVES: Research suggests that the addition of dexmedetomidine to local anesthetics can prolong peripheral nerve blocks; however, clinical safety data are limited, and interscalene blocks have not been studied. The present study was designed to test the hypothesis that dexmedetomidine added to ropivacaine would safely enhance the duration of analgesia without adverse effects when compared with ropivacaine alone. METHODS: We conducted a single-center, prospective, randomized, triple-blind, controlled trial of 62 patients undergoing elective shoulder surgery under general anesthesia with an interscalene block. Patients underwent ultrasound-guided interscalene blocks using either 12 mL of 0.5% ropivacaine or 0.5% ropivacaine plus 150-µg dexmedetomidine. The primary outcomes were self-reported duration of the nerve block and safety assessment (adverse effects and neurological sequelae). Data were analyzed in a blinded fashion. RESULTS: The median duration of the nerve block was 18 hours (95% confidence interval, 18-20) in the dexmedetomidine group and 14 hours (95% confidence interval, 14-16) in the ropivacaine group (P = 0.0001). Dexmedetomidine also lowered pain scores for the first 14 hours postoperatively and significantly hastened the time to sensory (P = 0.04) and motor (P = 0.002) block onset. Dexmedetomidine lowered heart rate but blood pressures were stable. Plasma levels of ropivacaine were not different between groups, and plasma dexmedetomidine levels were relatively low. There were no adverse events or neurological sequelae. CONCLUSIONS: Dexmedetomidine added to ropivacaine for interscalene blocks increased the duration of the nerve block and improved postoperative pain. These additional efficacy and safety data should encourage further study of peripheral perineural dexmedetomidine in humans.

Sleep apnea and total joint arthroplasty under various types of anesthesia: a population-based study of perioperative outcomes.

BACKGROUND AND OBJECTIVES: The presence of sleep apnea (SA) among surgical patients has been associated with significantly increased risk of perioperative complications. Although regional anesthesia has been suggested as a means to reduce complication rates among SA patients undergoing surgery, no data are available to support this association. We studied the association of the type of anesthesia and perioperative outcomes in patients with SA undergoing joint arthroplasty. METHODS: Drawing on a large administrative database (Premier Inc), we analyzed data from approximately 400 hospitals in the United States. Patients with a diagnosis of SA who underwent primary hip or knee arthroplasty between 2006 and 2010 were identified. Perioperative outcomes were compared between patients receiving general, neuraxial, or combined neuraxial-general anesthesia. RESULTS: We identified 40,316 entries for unique patients with a diagnosis for SA undergoing primary hip or knee arthroplasty. Of those, 30,024 (74%) had anesthesia-type information available. Approximately 11% of cases were performed under neuraxial, 15% under combined neuraxial and general, and 74% under general anesthesia. Patients undergoing their procedure under neuraxial anesthesia had significantly lower rates of major complications than did patients who received combined neuraxial and general or general anesthesia (16.0%, 17.2%, and 18.1%, respectively; P = 0.0177). Adjusted risk of major complications for those undergoing surgery under neuraxial or combined neuraxial-general anesthesia compared with general anesthesia was also lower (odds ratio, 0.83 [95% confidence interval, 0.74-0.93; P = 0.001] vs odds ratio, 0.90 [95% confidence interval, 0.82-0.99; P = 0.03]). CONCLUSIONS: Barring contraindications, neuraxial anesthesia may convey benefits in the perioperative outcome of SA patients undergoing joint arthroplasty. Further research is needed to enhance an understanding of the mechanisms by which neuraxial anesthesia may exert comparatively beneficial effects.

Ephedrine shows synergistic motor blockade when combined with bupivacaine or lidocaine for spinal anesthesia in a rat model.

BACKGROUND: Ephedrine is a direct/indirect vasoactive drug. In addition, it also possesses intrinsic local anesthetic properties, mainly due to its sodium-channel blockage. We investigated whether ephedrine demonstrates a synergistic effect with bupivacaine and lidocaine when injected via a spinal catheter into the spinal space of rats. METHODS: Spinal catheters were surgically placed in 47 rats (n = 8 per group; 7 rats were excluded.) Bupivacaine, lidocaine, and ephedrine in various concentrations and constant volumes (60 µL) were injected into the spinal catheters to determine the equipotency of each drug. Ephedrine in combination with either bupivacaine or lidocaine was then injected into the spinal catheters. RESULTS: Ephedrine demonstrated statistically significant synergistic effects with bupivacaine as well as with lidocaine in fixed combinations. The combination index reflecting a synergistic effect was 0.792 (95% confidence interval: 0.665-0.919) for ephedrine + bupivacaine and 0.663 (95% confidence interval: 0.532-0.794) for ephedrine + lidocaine. CONCLUSION: Ephedrine combined with either bupivacaine or lidocaine acted synergistically to block motor function and has the potential to reduce the amount of local anesthetic needed for spinal block. The synergistic effect of ephedrine in combination with local anesthetics is an interesting pharmacological phenomenon that warrants further clinical evaluation.

The Impact of Hypotensive Epidural Anesthesia on Distal and Proximal Tissue Perfusion in Patients Undergoing Total Hip Arthroplasty.

Little data exists to detail the effect of hypotensive epidural anesthesia on differential tissue oxygenation changes above and below the level of neuraxial blockade. This study was designed to investigate tissue oxygenation in a clinical setting, using non-invasive near-infrared spectroscopy. METHODS: Patients aged 18 to 85 years scheduled to undergo primary total hip arthroplasty were enrolled. Muscle oxygenation saturation was measured above and below the level of neuraxial blockade (deltoid and vastus lateralis muscles). Other continuously recorded parameters included cardiac output, stroke volume, heart rate, invasive mean arterial blood pressure and arterial oxygen saturation. Recordings of muscle oxygenation were compared over time separately for upper and lower extremity. RESULTS: 10 patients were enrolled. We found an intermittent and significant unadjusted decline of mean muscle oxygenation saturation in the vastus lateralis muscle during first part of the surgery (nadir 2nd quintile: 71.0% vs. 63.3%, p<0.0001). This decline was followed by a return to baseline towards the end of the surgery (71.0% vs. 69.1%, p=0.3429). Mean muscle oxygenation saturation did not change for the same period of time in the deltoid muscle. When adjusting for covariates, the changes in muscle tissue oxygenation remained significant. CONCLUSION: These results indicate that muscle oxygenation saturation, a surrogate parameter for tissue perfusion, is decreased by hypotensive epidural anesthesia, but only within the functional limits of the neuraxial blockade. The etiology of these findings remains to be elucidated.

Bilateral loss of neural function after interscalene plexus blockade may be caused by epidural spread of local anesthetics: a cadaveric study.

BACKGROUND AND OBJECTIVES: Interscalene brachial plexus blockade is widely used in surgical procedures of the upper limb. Recently, we experienced the complication of a contralateral blockade after ultrasound-guided interscalene block. The clinical appearance was a blockade of both the ipsilateral and the contralateral cervical segments 6 to 8. We hypothesized that epidural spread of local anesthetics could be cause for this phenomenon. METHODS: We conducted a cadaveric study using ultrasound for needle guidance of interscalene blocks in 5 cadavers by a single investigator using contrast agent. Injections were made either ventral (extrafascial) or dorsal (subfascial) to the prevertebral lamina of the deep cervical fascia. Computed tomography was obtained following each injection with contrast agent immediately after incremental injections of progressively higher volumes. Subsequently, contrast spread to anatomic landmarks was investigated by a radiologist. RESULTS: After ultrasound-controlled injection of contrast agent beneath the prevertebral layer of the deep cervical fascia, 4 of the 5 investigated specimens showed contrast enhancement in the epidural space in the consecutive computed tomography scans. After extrafascial injection, none of the investigated specimens showed contrast enhancement in the epidural space. CONCLUSIONS: Contralateral blockade after ultrasound-guided interscalene injection of local anesthetics is very likely to be the effect of epidural spread. Future in vivo studies are needed to understand the implications of needle location and volume on epidural spread in interscalene blockade.