Mohammad A. Helwani

Effects of regional versus general anesthesia on outcomes after total hip arthroplasty: a retrospective propensity-matched cohort study.

BACKGROUND Many orthopaedic surgical procedures can be performed with either regional or general anesthesia. We hypothesized that total hip arthroplasty with regional anesthesia is associated with less postoperative morbidity and mortality than total hip arthroplasty with general anesthesia. METHODS This retrospective propensity-matched cohort study utilizing the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database included patients who had undergone total hip arthroplasty from 2007 through 2011. After matching, logistic regression was used to determine the association between the type of anesthesia and deep surgical site infections, hospital length of stay, thirty-day mortality, and cardiovascular and pulmonary complications. RESULTS Of 12,929 surgical procedures, 5103 (39.5%) were performed with regional anesthesia. The adjusted odds for deep surgical site infections were significantly lower in the regional anesthesia group than in the general anesthesia group (odds ratio [OR] = 0.38; 95% confidence interval [CI] = 0.20 to 0.72; p < 0.01). The hospital length of stay (geometric mean) was decreased by 5% (95% CI = 3% to 7%; p < 0.001) with regional anesthesia, which translates to 0.17 day for each total hip arthroplasty. Regional anesthesia was also associated with a 27% decrease in the odds of prolonged hospitalization (OR = 0.73; 95% CI = 0.68 to 0.89; p < 0.001). The mortality rate was not significantly lower with regional anesthesia (OR = 0.78; 95% CI = 0.43 to 1.42; p > 0.05). The adjusted odds for cardiovascular complications (OR = 0.61; 95% CI = 0.44 to 0.85) and respiratory complications (OR = 0.51; 95% CI = 0.33 to 0.81) were all lower in the regional anesthesia group. CONCLUSIONS Compared with general anesthesia, regional anesthesia for total hip arthroplasty was associated with a reduction in deep surgical site infection rates, hospital length of stay, and rates of postoperative cardiovascular and pulmonary complications. These findings could have an important medical and economic impact on health-care practice.

The Current Role of Ultrasound Use in Teaching Regional Anesthesia: A Survey of Residency Programs in the United States

BACKGROUND AND OBJECTIVES   The purpose of this survey was to determine the current teaching practices of regional anesthesia and the prevalence of ultrasound use in guiding peripheral nerve blocks in the academic institutions across the United States. METHODS   A survey was distributed to all American Board of Anesthesiology-accredited residency programs via email and/or the U.S. postal service. The survey was designed to determine the number of peripheral nerve blocks (PNBs) performed, the role of the ultrasound guidance, the barriers to its use, and the methods by which teaching physicians acquired their ultrasound skills. RESULTS   We received 82 responses (62%) of the 132 programs surveyed. Eighty-eight percent of the responding programs performed more than 20 PNBs/week and 46% performed more than 40 PNBs/week. Three-fourths of the respondents relied on ultrasound to guide the majority of single injection and continuous PNBs. When using ultrasound, most programs (79%) used real-time ultrasound without nerve stimulator. Most teaching physicians supervising ultrasound-guided PNBs received their training via workshops and/or from other colleagues. The three main reasons for using ultrasound were to 1) achieve a higher success rate; 2) improve safety; and 3) teach anesthesia trainees. However, the three main barriers to using ultrasound were 1) lack of training; 2) perceived decreased efficiency; and 3) the lack of immediate availability of equipment. Overall, ultrasound was less utilized to guide lower extremity vs upper extremity PNBs. CONCLUSIONS   Ultrasound-guided PNBs are universally taught across residency programs in the United States. Most teaching physicians believe that ultrasound increases PNBs success and improves safety of regional anesthesia. Barriers to ultrasound use are lack of faculty training and unavailability of ultrasound equipment.

Improving Prediction of Postoperative Myocardial Infarction With High-Sensitivity Cardiac Troponin T and NT-proBNP.

BACKGROUND: This study sought to determine whether preoperatively measured high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) improve cardiac risk prediction in patients undergoing major noncardiac surgery compared with the standard risk indices. METHODS: In this ancillary study to the Vitamins in Nitrous Oxide trial, patients were included who had preoperative hs-cTnT and NT-proBNP measured (n = 572). Study outcome was the incidence of postoperative myocardial infarction (MI) within the first 3 postoperative days. hs-cTnT was considered elevated if >14 ng/L and NT-proBNP if >300 ng/L. Additional cutoff values were investigated on the basis of receiver operating characteristic statistics. Biomarker risk prediction was compared with Lee’s Revised Cardiac Risk Index (RCRI) with the use of standard methods and net reclassification index. RESULTS: The addition of hs-cTnT (>14 ng/L) and NT-proBNP (>300 ng/L) to RCRI significantly improved the prediction of postoperative MI (event rate 30/572 [5.2%], Area under the receiver operating characteristic curve increased from 0.590 to 0.716 with a 0.66 net reclassification index [95% confidence interval 0.32–0.99], P < .001). The use of 108 ng/L as a cutoff for NT-proBNP improved sensitivity compared with 300 ng/L (0.87 vs 0.53). Sensitivity, specificity, positive, and negative predictive value for hs-cTnT were 0.70, 0.60, 0.09, and 0.97 and for NT-proBNP were 0.53, 0.68, 0.08, and 0.96. CONCLUSIONS: The addition of cardiac biomarkers hs-cTnT and NT-proBNP to RCRI improves the prediction of adverse cardiac events in the immediate postoperative period after major noncardiac surgery. The high negative predictive value of preoperative hs-cTnT and NT-proBNP suggest usefulness as a “rule-out” test to confirm low risk of postoperative MI.

High-sensitivity Cardiac Troponin Elevation after Electroconvulsive Therapy: A Prospective, Observational Cohort Study

Background: While electroconvulsive therapy is widely regarded as a lifesaving and safe procedure, evidence regarding its effects on myocardial cell injury is sparse. The objective of this investigation was to determine the incidence and magnitude of new cardiac troponin elevation after electroconvulsive therapy using a novel high-sensitivity cardiac troponin I assay. Methods: This was a prospective cohort study in adult patients undergoing electroconvulsive therapy in a single academic center (up to three electroconvulsive therapy treatments per patient). The primary outcome was new high-sensitivity cardiac troponin I elevation after electroconvulsive therapy, defined as an increase of high-sensitivity cardiac troponin I greater than 100% after electroconvulsive therapy compared to baseline with at least one value above the limit of quantification (10 ng/l). Twelve-lead electrocardiogram and high-sensitivity cardiac troponin I values were obtained before and 15 to 30 min after electroconvulsive therapy; in a subset of patients, an additional 2-h high-sensitivity cardiac troponin I value was obtained. Results: The final study population was 100 patients and a total of 245 electroconvulsive therapy treatment sessions. Eight patients (8 of 100; 8%) experienced new high-sensitivity cardiac troponin I elevation after electroconvulsive therapy with a cumulative incidence of 3.7% (9 of 245 treatments; one patient had two high-sensitivity cardiac troponin I elevations), two of whom had a non–ST-elevation myocardial infarction (incidence 2 of 245; 0.8%). Median high-sensitivity cardiac troponin I concentrations did not increase significantly after electroconvulsive therapy. Tachycardia and/or elevated systolic blood pressure developed after approximately two thirds of electroconvulsive therapy treatments. Conclusions: Electroconvulsive therapy appears safe from a cardiac standpoint in a large majority of patients. A small subset of patients with preexisting cardiovascular risk factors, however, may develop new cardiac troponin elevation after electroconvulsive therapy, the clinical relevance of which is unclear in the absence of signs of myocardial ischemia.

Intraoperative plateau pressure measurement using modern anesthesia machine ventilators

Monitoring respiratory system mechanics is vital to guide safe and effective ventilator management. Transalveolar pressure (tAp) is the driving force of alveolar distension, which allows for effective respiration; however, overdistension may lead to inflammation and subsequent destruction of alveoli. Unfortunately, there is no practical way to measure tAp directly; hence, surrogate measures are often used. Peak airway pressure (PAP), commonly monitored in patients undergoing general anesthesia, consists of static and dynamic components. Volume-preset ventilation allows determination of the respiratory system mechanics. In a muscle-relaxed patient, PAP consists of two components, i.e., the dynamic pressure to drive gas across the resistance (Pres) of the bronchial tree and the static pressure to expand the alveoli against the elastic recoil of the lungs and chest wall (Plateau pressure, [Pplat]), which is more reflective of tAp than PAP. Plateau pressure can be displayed easily on the new generation of anesthesia machine ventilators by inserting an end-inspiratory pause of 0.5-1 sec. Calculating the difference in airway pressure during flow and no-flow states allows the calculation of airway resistance (Pres = PAP Pplat). Diagnostic and therapeutic information can be extracted by distinguishing components of PAP. This information can help the anesthesia provider to narrow the differential diagnosis of high PAP to help solve oxygenation/ventilation issues and tailor treatment. For example, elevated Pres at constant flow may indicate bronchospasm or endotracheal tube obstruction (Figure). Conversely, falling Pres may correspond with a response to bronchodilators. Elevated Pplat indicates excessive tidal volume or decreased lung and/or chest wall compliance (e.g., pulmonary edema, acute lung injury, or abdominal distension). Positive pressure ventilation may cause or exacerbate lung injury due to an increase in lung stretching which is best assessed by the transpulmonary pressure or the tAp. Separation of lungs from chest wall compliance requires an esophageal pressure measurement to approximate pleural pressure. Due to the technical and accuracy limitations, esophageal manometry is not widely used, and Pplat is used as a surrogate to guide titration of mechanical ventilation. As a lung protective ventilation strategy, it is recommended that Pplat be maintained B 30 cm H2O to prevent alveolar overdistension and barotrauma, especially in acute lung injury and during one-lung ventilation. Whenever chest compliance is reduced, the stiff chest contributes substantially to Pplat. This should be taken into consideration when assessing lung stretch, as higher Pplat may still be safe due to the limitation of alveolar distension by the chest wall. We present two examples of procedures to acquire Pplat in the operating room using two popular anesthesia machines. For the GE S/5 Aespire SmartVent (General Electric Company, Madison, WI, USA) (Figure), select setup/calibration from the main menu (Figure, upper panel); then change the inspiratory pause from 0 to 30-60% to achieve a pause of 0.5-1 sec, and Pplat will be displayed (Figure, lower panel). With a respiratory rate of 8 breaths min and inspiratory:expiratory (I:E) ratio 1:2, M. A. Helwani, MD (&) Washington University School of Medicine, St. Louis, MO, USA e-mail: helwanim@anest.wustl.edu

High-Sensitivity Cardiac Troponin T Improves the Diagnosis of Perioperative MI

BACKGROUND: The diagnosis of myocardial infarction (MI) after noncardiac surgery has traditionally relied on using relatively insensitive contemporary cardiac troponin (cTn) assays. We hypothesized that using a recently introduced novel high-sensitivity cTnT (hscTnT) assay would increase the detection rate of perioperative MI. METHODS: In this ancillary study of the Vitamins in Nitrous Oxide trial, readjudicated incidence rates of myocardial injury (new isolated cTn elevation) and MI were compared when diagnosed by contemporary cTnI versus hscTnT. We probed various relative (eg, >50%) or absolute (eg, +5 ng/L) hscTnT change metrics. Inclusion criteria for this ancillary study were the presence of a baseline and at least 1 postoperative hscTnT value. RESULTS: Among 605 patients, 70 patients (12%) had electrocardiogram changes consistent with myocardial ischemia; 82 patients (14%) had myocardial injury diagnosed by contemporary cTnI, 31 (5.1%) of which had an adjudicated MI. After readjudication, 67 patients (11%) were diagnosed with MI when using hscTnT, a 2-fold increase. Incidence rates of postoperative myocardial injury ranged from 12% (n = 73) to 65% (n = 393) depending on the hscTnT metric used. Incidence rates of MI using various hscTnT change metrics and the presence of ischemic electrocardiogram changes, but without event adjudication, ranged from 3.6% (n = 22) to 12% (n = 74), a >3-fold difference. New postoperative hscTnT elevation, either by absolute or relative hscTnT change metric, was associated with an up to 5-fold increase in 6-month mortality. CONCLUSIONS: The use of hscTnT compared to contemporary cTnI increases the detection rate of perioperative MI by a factor of 2. Using different absolute or relative hscTnT change metrics may lead to under- or overdiagnosis of perioperative MI.

Dexamethasone and Clonidine, but not Epinephrine, Prolong Duration of Ropivacaine Brachial Plexus Blocks, Cross-Sectional Analysis in Outpatient Surgery Setting

Objective The primary aim of this study is to determine the effect of adding dexamethasone, clonidine or both with and without epinephrine to ropivacaine and bupivacaine brachial plexus blocks. Design Observational study of prospectively collected data. Setting Single academic outpatient surgery center. Methods We evaluated 5,515 patient entries who received brachial plexus block (BPB). Multiple, rescue, unsuccessful, and distal nerve blocks of the upper extremity were excluded. The duration was calculated from the time the block was performed until the resolution of the block by patient report. Block durations were compared using Analysis of Variance. Results After exclusions, 3,706 nerve blocks were analyzed. The median concentration of ropivacaine used was 0.5%. Both clonidine and dexamethasone significantly increased block duration by 1.1 and 3.0 hours, respectively. Combining clonidine and dexamethasone with ropivacaine increased block duration by 6.2 hours (p<0.001) when compared to ropivacaine alone. Dexamethasone and Clonidine increased block duration by 5.2 hours (p<0.001) when compared to clonidine alone and by 3.2 hours (p<0.001) compared to dexamethasone alone. The addition of epinephrine to any of the adjuvants made no statistically significant difference to the duration of action except when it was added to dexamethasone. Summary For brachial plexus blocks, epinephrine did not affect the duration of analgesia when added to ropivacaine. Epinephrine did not enhance the observed increase of block duration induced by clonidine or the combination of clonidine and dexamethasone. The most block duration enhancement was observed when combination of clonidine and dexamethasone were added to ropivacaine.

Mortality and Ratio of Blood Products Used in Patients With Severe Trauma

Mortality and Ratio of Blood Products Used in Patients With Severe Trauma To the Editor Dr Holcomb and the Pragmatic, Randomized Optimal Platelet and Plasma Ratios (PROPPR) study collaborative1 completed a multicenter randomized trial with the hypothesis that a 1:1:1 ratio for units of plasma and platelets to red blood cells (RBCs) would be superior to a 1:1:2 ratio. These investigators did not find a survival advantage in their primary outcomes of 24-hour and 30-day mortality, achieving greater than 95% power to detect a 10% mortality reduction. Survival was an objective end point, whereas the secondary end points of hemostatic control and death attributed to exsanguination were subjective and vulnerable to observer bias by the unblinded treating surgeon. For example, in Table 3 in the article, the 1:1:1 group had 31 exsanguination deaths during the first 24 hours and 5 deaths after 24 hours. However, in the 1:1:2 group, all 50 exsanguination deaths occurred within the first 24 hours and none after 24 hours. These values are difficult to reconcile because the 1:1:1 cohort reportedly had superior hemostasis and delayed deaths from bleeding, whereas the 1:1:2 group did not. Resuscitation with fixed ratios of blood products has been associated with worse outcomes compared with goaldirected resuscitation.2 The likely mechanistic explanation is that patients with trauma manifest a spectrum of coagulation abnormalities following injury3 to which a ratio approach does not adapt. Goal-directed hemostatic resuscitation allows tailoring of transfusions to the dynamic changes in hemostasis occurring between different patients and within the same patient during the course of resuscitation, guided by results obtained within minutes.4 Thrombelastography has been previously reported to be the optimal tool to predict transfusion requirements in patients with trauma.5 Only the R value for thrombelastography was reported in this article despite the other variables (angle, MA, LY30) being recognized as reliable predictors of transfusion requirements and death. It would be instructive to see these additional thrombelastography variables at enrollment and examine the effect of the resuscitation strategies on these measures of hemostatic capacity over time. In contrast to the authors’ conclusion, we suggest that a 1:1:2 ratio, which uses less blood product, may be the preferred strategy from a health care resource use perspective. With mounting evidence that patients with trauma have different phenotypes of coagulation abnormalities, personalizing resuscitation strategies over a formulaic fixed ratio approach warrants prospective evaluation.

Intraoperative protective ventilation: too early to redefine management parameters?

The attention to detail, use of a large representative dataset, and rigorous statistical approach in Ladha and colleagues’ study of intraoperative mechanical ventilation and postoperative respiratory complications all help advance our knowledge.1 However, important limitations mean that these data must be interpreted with caution, especially before changing ventilatory management practices for patients in the operating room. In a retrospective analysis of prospectively collected data, the authors showed in both unmatched and propensity matched analyses that patients who had all three of low plateau pressures (Pplat), low tidal …

To BIS or not to BIS.

In Reply: We thank Dr. Myles for his thoughtful comments on our editorial1 and his contribution to the field of anesthesiology in general and comparative effectiveness research (CER) specifically. The points, including the disagreement with our categorization of the discussed trials, are well taken and are representative of a wider discussion about the question of what actually constitutes CER and what methodologies should be used to achieve it.2,3 Although the most commonly used definition in the United States today is that put forth by the Federal Coordinating Council for Comparative Effectiveness Research in 2009,* it can be argued that principles There are few points that warrant clarification. First, the author included patients who received total intravenous anesthesia. However, the details of this subgroup of patients were not provided. The method of determining the minimum alveolar concentration level in the no bispectral index total intravenous anesthesia patients, the alarm limits, and the incidence of awareness in these patients were not described. Second, the inter-rater agreement using Fleiss κ statistic for the three blinded assessments of awareness showed fair agreement (0.25). Can the authors comment on the low level of agreement and provide the confidence interval for κ? Third, 36% of patients did not have bispectral index data recorded because of technical issues. While this could provide a third arm for comparison, it may also create some bias. Providers who did not receive an alarm might have decreased vigilance as they could have depended on the alarm system. Adding a third arm of routine care in the design might have provided valuable information. Finally, it would have been interesting to learn more about the 19 definite awareness cases in this large sample which could help in refining the characteristics of high-risk patients.