Recent Research Publications Spotlight

Udani AD, Moyse D, Peery CA, Taekman JM. Twitter-Augmented Journal Club: Educational Engagement and Experience So Far. A A Case Rep. 2015 Nov 17. [Epub ahead of print]


Social media is a nascent medical educational technology. The benefits of Twitter include (1) easy adoption; (2) access to experts, peers, and patients across the globe; (3) 24/7 connectivity; (4) creation of virtual, education-based communities using hashtags; and (5) crowdsourcing information using retweets. We report on a novel Twitter-augmented journal club for anesthesia residents: its design, implementation, and impact. Our inaugural anesthesia Twitter-augmented journal club succeeded in engaging the anesthesia community and increasing residents’ professional use of Twitter. Notably, our experience suggests that anesthesia residents are willing to use social media for their education.

García PS, Ciavatta VT, Fidler JA, Woodbury A, Levy JH, Tyor WR. Concentration-Dependent Dual Role of Thrombin in Protection of Cultured Rat Cortical Neurons. Neurochem Res. 2015 Nov;40(11):2220-9. Epub 2015 Sep 5.


Thrombin’s role in the nervous system is not well understood. Under conditions of blood-brain barrier compromise (e.g., neurosurgery or stroke), thrombin can result in neuroapoptosis and the formation of glial scars. Despite this, preconditioning with thrombin has been found to be neuroprotective in models of cerebral ischemia and intracerebral hemorrhage. We investigated the effects of physiologically relevant concentrations of thrombin on cortical neurons using two culture-based assays. We examined thrombin’s effect on neurites by quantitative analysis of fluorescently labeled neurons. To characterize thrombin’s effects on neuron survival, we spectrophotometrically measured changes in enzymatic activity. Using receptor agonists and thrombin inhibitors, we separately examined the role of thrombin and its receptor in neuroprotection. We found that low concentrations of thrombin (1 nM) enhances neurite growth and branching, neuron viability, and protects against excitotoxic damage. In contrast, higher concentrations of thrombin (100 nM) are potentially detrimental to neuronal health as evidenced by inhibition of neurite growth. Lower concentrations of thrombin resulted in equivalent neuroprotection as the antifibrinolytic, aprotinin, and the direct thrombin inhibitor, argatroban. Interestingly, exogenous application of the species-specific thrombin inhibitor, antithrombin III, was detrimental to neuronal health; suggesting that some endogenous thrombin is necessary for optimal neuron health in our culture system. Activation of the thrombin receptor, protease-activated receptor-1 (PAR-1), via micromolar concentrations of the thrombin receptor agonist peptide, TRAP, did not adversely affect neuronal viability. An optimal concentration of thrombin exists to enhance neuronal health. Neurotoxic effects of thrombin do not involve activation of PAR receptors and thus separate pharmacologic manipulation of thrombin’s receptor in the setting of direct thrombin inhibitors could be a potential neuroprotective strategy.

Whitener G, McKenzie J, Akushevich I, White WD, Dhakal IB, Nicoara A, Swaminathan M. Discordance in Grading Methods of Aortic Stenosis by Pre-Cardiopulmonary Bypass Transesophageal Echocardiography. Anesth Analg. 2015 Dec 8. [Epub ahead of print]


BACKGROUND: Current guidelines define severe aortic valve stenosis (AS) as an aortic valve area (AVA) ≤1.0 cm by the continuity equation and mean gradient (ΔPm) ≥ 40 mm Hg. However, these measurements can be discordant when classifying AS severity. Approximately one-third of patients with normal ejection fraction and severe AS by AVA have nonsevere AS by ΔPm when measured by preoperative transthoracic echocardiography (TTE). Given the use of positive pressure ventilation and general anesthesia in the pre-cardiopulmonary bypass (pre-CPB) period, we hypothesized that discordance between ΔPm and AVA during pre-CPB transesophageal echocardiography (TEE) would be higher than previously reported by TTE.

METHODS: We retrospectively examined pre-CPB TEE data for patients who had aortic valve replacement, with or without coronary artery bypass grafting, from 2000 to 2012. Patients were excluded if they had ejection fraction <55%, emergency surgery, repeat sternotomy, moderate or severe mitral regurgitation, or severe aortic regurgitation. Only patients with both pre-CPB AVA and ΔPm measurements were included. Patients were grouped according to severity (mild, moderate, and severe) by AVA or ΔPm. Discordance was defined as disagreement between severities based on either parameter.

RESULTS: A total of 277 patients met inclusion criteria. There were 227 patients with AVA ≤ 1.0 cm. The proportion of these patients with a ΔPm < 40 mm Hg was 54% (95% confidence interval, 47%-61%). The rate of discordance was significantly higher than the rate (37%; P < 0.001) found in previously reported analyses using TTE. Of the patients with a ΔPm ≥ 40 mm Hg, only 8% (n = 9/113) had a discordant AVA. In contrast, of the patients with ΔPm < 40 mm Hg, 80% (n = 131/164) had a discordant AVA.

CONCLUSIONS: We confirmed our hypothesis that grading AS by ΔPm and AVA during pre-CPB TEE exhibits higher discordance than reported for TTE by others. It remains unclear whether these discrepancies reflect the effect of general anesthesia, imaging modality (TTE versus TEE) differences, inaccuracies in AS grading cutoffs when applied to pre-CPB TEE, or selection bias of the surgical population.

Olson R, Ishwori D. Day of Surgery Cancellation Rate After Preoperative Telephone Nurse Screening or Comprehensive Optimization Visit. Perioperative Medicine. (2015) 4:12.


BACKGROUND: Structured preoperative assessment has been reported to improve operating room efficiency as measured by metrics such as day of surgery cancellations (DOSCs). However, not all patients require comprehensive assessment; routine full assessments can result in unnecessary duplication of tests and investigations. Selective nurse screening under the supervision of anesthesiology may provide adequate information gathering in lower risk patients. This study is undertaken to assess if DOSC rates vary with different assessment processes.

METHODS: At a single academic tertiary care hospital, from Jan 2 to May 31, 2013, the consecutive patients undergoing comprehensive preoperative assessment (CPA) and nurse screening (NS), as well as the patients not assessed by the anesthesiology-supervised preoperative process, were followed for the occurrence and reason for DOSC. The operating room schedule of all elective surgery patients was analyzed to allow calculation of rates of DOSCs. Reasons for cancellations were documented as one of ten structured reasons by preoperative holding area clerical staff.

RESULTS: Overall, there were 14,893 elective surgery patients in this time period, with 183 DOSCs, giving a rate of 1.23 % (95 % CI 1.06, 1.42). Patients who received CPA numbered 5980; 29 of them had a DOSC, giving a rate of 0.48 % (95 % CI 0.33–0.70) (P < 0.0001 vs. no assessment). Patients receiving NS numbered 1840; 11 of them had a DOSC, giving a rate of 0.60 % (95 % CI 0.30–1.10) (P < 0.0001 vs. no assessment). The most common reason for cancellation was new medical condition.

CONCLUSIONS: A very low DOSC rate can be achieved with a comprehensive preoperative process where some patients are selectively telephone screened by nurses, with complete assessment deferred to the anesthesiologist on the day of surgery.

Gadsden J, Latmore M, Levine DM, Robinson A. High Opening Injection Pressure Is Associated With Needle-Nerve and Needle-Fascia Contact During Femoral Nerve Block. Reg Anesth Pain Med. 2015 Dec 8. [Epub ahead of print]


BACKGROUND AND OBJECTIVES: High opening injection pressures (OIPs) have been shown to predict sustained needle tip contact with the roots of the brachial plexus. Such roots have a uniquely high ratio of fascicular versus connective tissue. It is unknown if this relationship is preserved during multifascicular nerve blockade. We hypothesized that OIP can predict needle-nerve contact during femoral nerve block, as well as detect needle contact with the fascia iliaca.

METHODS: Twenty adults scheduled for femoral block were recruited. Using ultrasound, a 22-gauge needle was sequentially placed in 4 locations: indenting the fascia iliaca, advanced through the fascia iliaca while lateral to the nerve, slightly indenting the femoral nerve, and withdrawn from the nerve 1 mm. At each location, the OIP required to initiate an injection of 1 mL D5W (5% dextrose in water) at 10 mL/min was recorded. Blinded investigators performed evaluations and aborted injections when an OIP of 15 psi was reached.

RESULTS: Opening injection pressure was 15 psi or greater for 90% and 100% of cases when the needle indented the femoral nerve and fascia iliaca, respectively. Opening injection pressure was less than 15 psi for all 20 patients when the needle was withdrawn 1 mm from the nerve as well as at the subfascial position (McNemar χ P < 0.001).

CONCLUSIONS: Opening injection pressure greater than 15 psi was associated with a block needle tip position slightly indenting the epineurium of the femoral nerve (90%) and the fascia iliaca (100%). Needle tip positions not indenting these structures were associated with OIP of less than 15 psi (100%).