Impact of Caffeine Ingestion on the Driving Performance of Anesthesiology Residents After 6 Consecutive Overnight Work Shifts.

BACKGROUND: Residency training in anesthesiology involves care of hospitalized patients and necessitates overnight work, resulting in altered sleep patterns and sleep deprivation. Caffeine consumption is commonly used to improve alertness when fatigued after overnight work, in preparation for the commute home. METHODS: We studied the impact of drinking a caffeinated energy drink (160 mg of caffeine) on driving performance in a high-fidelity, virtual reality driving simulator (Virginia Driving Safety Laboratory using the Driver Guidance System) in anesthesiology resident physicians immediately after 6 consecutive night-float shifts. Twenty-six residents participated and were randomized to either consume a caffeinated or noncaffeinated energy drink 60 minutes before the driving simulation session. After a subsequent week of night-float work, residents performed the same driving session (in a crossover fashion) with the opposite intervention. Psychomotor vigilance task (PVT) testing was used to evaluate reaction time and lapses in attention. RESULTS: After 6 consecutive night-float shifts, anesthesiology residents who consumed a caffeinated energy drink had increased variability in driving for throttle, steering, and speed during the first 10 minutes of open-road driving but proceeded to demonstrate improved driving performance with fewer obstacle collisions (epoch 2: 0.65 vs 0.87; epoch 3: 0.47 vs 0.95; P = .03) in the final 30 minutes of driving as compared to driving performance after consumption of a noncaffeinated energy drink. Improved driving performance was most apparent during the last 30 minutes of the simulated drive in the caffeinated condition. Mean reaction time between the caffeine and noncaffeine states differed significantly (278.9 ± 29.1 vs 294.0 ± 36.3 milliseconds; P = .021), while the number of major lapses (0.09 ± 0.43 vs 0.27 ± 0.55; P = .257) and minor lapses (1.05 ± 1.39 vs 2.05 ± 3.06; P = .197) was not significantly different. CONCLUSIONS: After consuming a caffeinated energy drink on conclusion of 6 shifts of night-float work, anesthesiology residents had improved control of driving performance variables in a high-fidelity driving simulator, including a significant reduction in collisions as well as slightly faster reaction times.

Driving Performance of Residents after Six Consecutive Overnight Work Shifts.

BACKGROUND: Residency training requires work in clinical settings for extended periods of time, resulting in altered sleep patterns, sleep deprivation, and potentially deleterious effects on safe performance of daily activities, including driving a motor vehicle. METHODS: Twenty-nine anesthesiology resident physicians in postgraduate year 2 to 4 drove for 55 min in the Virginia Driving Safety Laboratory using the Driver Guidance System (MBFARR, LLC, USA). Two driving simulator sessions were conducted, one experimental session immediately after the final shift of six consecutive night shifts and one control session at the beginning of a normal day shift (not after call). Both sessions were conducted at 8:00 AM. Psychomotor vigilance task testing was employed to evaluate reaction time and lapses in attention. RESULTS: After six consecutive night shifts, residents experienced significantly impaired control of all the driving variables including speed, lane position, throttle, and steering. They were also more likely to be involved in collisions. After six consecutive night shifts, residents had a significant increase in reaction times (281.1 vs. 298.5 ms; P = 0.001) and had a significant increase in the number of both minor (0.85 vs. 1.88; P = 0.01) and major lapses (0.00 vs. 0.31; P = 0.008) in attention. CONCLUSIONS: Resident physicians have greater difficulty controlling speed and driving performance in the driving simulator after six consecutive night shifts. Reaction times are also increased with emphasis on increases in minor and major lapses in attention after six consecutive night shifts.

Ventricular assist devices and increased blood product utilization for cardiac transplantation.

BACKGROUND AND AIM OF STUDY: The purpose of this study was to examine whether blood product utilization, one-year cell-mediated rejection rates, and mid-term survival significantly differ for ventricular assist device (VAD patients compared to non-VAD (NVAD) patients following cardiac transplantation. METHODS: From July 2004 to August 2011, 79 patients underwent cardiac transplantation at a single institution. Following exclusion of patients bridged to transplantation with VADs other than the HeartMate II® LVAD (n = 10), patients were stratified by VAD presence at transplantation: VAD patients (n = 35, age: 54.0 [48.0-59.0] years) vs. NVAD patients (n = 34, age: 52.5 [42.8-59.3] years). The primary outcomes of interest were blood product transfusion requirements, one-year cell-mediated rejection rates, and mid-term survival post-transplantation. RESULTS: Preoperative patient characteristics were similar for VAD and NVAD patients. NVAD patients presented with higher median preoperative creatinine levels compared to VAD patients (1.3 [1.1-1.6] vs. 1.1 [0.9-1.4], p = 0.004). VAD patients accrued higher intraoperative transfusion of all blood products (all p ≤ 0.001) compared to NVAD patients. The incidence of clinically significant cell-mediated rejection within the first posttransplant year was higher in VAD compared to NVAD patients (66.7% vs. 33.3%, p = 0.02). During a median follow-up period of 3.2 (2.0, 6.3) years, VAD patients demonstrated an increased postoperative mortality that did not reach statistical significance (20.0% vs. 8.8%, p = 0.20). CONCLUSIONS: During the initial era as a bridge to transplantation, the HeartMate II® LVAD significantly increased blood product utilization and one-year cell-mediated rejection rates for cardiac transplantation. Further study is warranted to optimize anticoagulation strategies and to define causal relationships between these factors for the current era of cardiac transplantation.

Speed, accuracy, and confidence in Google, Ovid, PubMed, and UpToDate: results of a randomised trial.

BACKGROUND: The explosion of biomedical information has led to an 'information paradox'-the volume of biomedical information available has made it increasingly difficult to find relevant information when needed. It is thus increasingly critical for physicians to acquire a working knowledge of biomedical informatics. AIM: To evaluate four search tools commonly used to answer clinical questions, in terms of accuracy, speed, and user confidence. METHODS: From December 2008 to June 2009, medical students, resident physicians, and attending physicians at the authors' institution were asked to answer a set of four anaesthesia and/or critical care based clinical questions, within 5 min, using Google, Ovid, PubMed, or UpToDate (only one search tool per question). At the end of each search, participants rated their results on a four point confidence scale. One to 3 weeks after answering the initial four questions, users were randomised to one of the four search tools, and asked to answer eight questions, four of which were repeated. The primary outcome was defined as a correct answer with the highest level of confidence. RESULTS: Google was the most popular search tool. Users of Google and UpToDate were more likely than users of PubMed to answer questions correctly. Subjects had the most confidence in UpToDate. Searches with Google and UpToDate were faster than searches with PubMed or Ovid. CONCLUSION: Non-Medline based search tools are not inferior to Medline based search tools for purposes of answering evidence based anaesthesia and critical care questions.

Strict glucose control does not affect mortality after aneurysmal subarachnoid hemorrhage.

BACKGROUND: The effects of both hyperglycemia and hypoglycemia are deleterious to patients with neurologic injury. METHODS: On January 1, 2002, the neurointensive care unit at the University of Virginia Health System initiated a strict glucose control protocol (goal glucose < 120 mg/dl). The authors conducted an impact study to determine the effects of this protocol on patients presenting with aneurysmal subarachnoid hemorrhage. RESULTS: Among the 834 patients admitted between 1995 and 2007, the in-hospital mortality was 11.6%. The median admission glucose for survivors was lower (135 vs. 176 mg/dl); however, on multivariate analysis, increasing admission glucose was not associated with a statistically significant increase in the risk of death (P = 0.064). The median average glucose for survivors was also lower (116 vs. 135 mg/dl). This was significant on multivariate analysis (P < 0.001); however, the effect was small (odds ratio, 1.045). Implementation of the strict glucose protocol decreased median average glucose (121 vs. 116 mg/dl, P < 0.001) and decreased the incidence of hyperglycemia. Implementation of the protocol had no effect on in-hospital mortality (11.7% vs. 12.0%, P = 0.876 [univariate], P = 0.132 [multivariate]). Protocol implementation was associated with an increased incidence of hypoglycemia (P < 0.001). Hypoglycemia was associated with a substantially increased risk of death on multivariate analysis (P = 0.009; odds ratio = 3.818). CONCLUSIONS: The initiation of a tight glucose control regimen lowered average glucose levels but had no effect on overall in-hospital mortality.

Perioperative statin use is associated with decreased incidence of primary graft dysfunction after lung transplantation.

BACKGROUND: Primary graft dysfunction (PGD) is a major cause of early morbidity and mortality after lung transplantation. Statins reduce the risk of chronic rejection after lung transplantation, but their effects on PGD are unknown. We hypothesized that perioperative statin therapy decreases the risk for PGD after lung transplantation. METHODS: We retrospectively reviewed records of all patients undergoing lung transplantation between January 1999 and December 2014 at the University of Virginia Health System. The primary outcome was PGD (grades 1-3). Secondary outcomes included grade 3 PGD, length of intensive care unit and hospital stay, and mortality. RESULTS: Of 266 patients who met final inclusion criteria, 138 (52%) were diagnosed with PGD. In-hospital mortality among patients with PGD was 6.5%. There were no deaths in patients without PGD (p < 0.001). PGD was diagnosed in 24 patients taking statins (34.8%) and in 114 patients (57.9%) who did not take statins (p = 0.001). After propensity score adjustments, perioperative statin use was independently associated with a reduced risk for PGD (odds ratio [OR] 0.41, 95% confidence interval [CI] 0.20-0.84, p = 0.015) and reduced risk to develop grade 3 PGD (OR 0.42, 95% CI 0.18-0.94, p = 0.036). Other risk factors associated with PGD included intraoperative use of cardiopulmonary bypass (OR 3.74, 95% CI 1.75-8.02, p = 0.001) and positive donor smoking status (OR 2.27, 95% CI 1.18-4.35, p = 0.014). CONCLUSIONS: The results demonstrate that perioperative use of statins is independently associated with reduced risk for PGD after lung transplantation.

Haptoglobin 2-2 Phenotype Is Associated With Increased Acute Kidney Injury After Elective Cardiac Surgery in Patients With Diabetes Mellitus.

BACKGROUND: Recent studies reported an association between the 2-2 phenotype of haptoglobin (Hp 2-2) and increased cardiorenal morbidity in nonsurgical diabetic patients. Our goal was to determine whether the Hp 2-2 phenotype was associated with acute kidney injury (AKI) after elective cardiac surgery in patients with diabetes mellitus. METHODS AND RESULTS: We prospectively enrolled 99 diabetic patients requiring elective cardiac surgery with cardiopulmonary bypass. Haptoglobin phenotypes were determined by gel electrophoresis. Cell-free hemoglobin, haptoglobin, and total serum bilirubin were quantified as hemolysis markers. The primary outcome was postoperative AKI, as defined by the Acute Kidney Injury Network classification. The incidence of AKI was significantly higher in Hp 2-2 patients compared with patients without this phenotype (non-Hp-2-2; 55.6% versus 27%, P<0.01). The need for renal replacement therapy was also significantly higher in the Hp 2-2 group (5 patients versus 1 patient, P=0.02). Thirty-day mortality (3 versus 0 patients, P=0.04) and 1-year mortality (5 versus 0 patients, P<0.01) were also significantly higher in patients with the Hp 2-2 phenotype. In multivariable analysis, Hp 2-2 was an independent predictor of postoperative AKI (P=0.01; odds ratio: 4.17; 95% confidence interval, 1.35-12.48). CONCLUSIONS: Hp 2-2 phenotype is an independent predictor of postoperative AKI and is associated with decreased short and long-term survival after cardiac surgery in patients with diabetes mellitus.

Use of the intrathoracic pressure regulator to lower intracranial pressure in patients with altered intracranial elastance: a pilot study.

OBJECT: The intrathoracic pressure regulator (ITPR) is a novel noninvasive device designed to increase circulation and blood pressure. By applying negative pressure during the expiratory phase of ventilation it decreases intrathoracic pressure and enhances venous return, which increases cardiac output. It is possible that the ITPR may both decrease intracranial pressure (ICP) and increase cerebral perfusion pressure (CPP) in brain-injured patients by decreasing cerebral venous blood volume and increasing cardiac output. The authors conducted an open-label, "first-in-humans" study of the ITPR in patients with an ICP monitor or external ventricular drain and altered intracranial elastance. METHODS: This prospective randomized trial commenced July 2009. Baseline hemodynamic variables and ICP were recorded prior to inserting one of the two ITPRs into the ventilator circuit based on a randomization scheme. Depending on the device selected, activation provided either -5 or -9 mm Hg endotracheal tube pressure. Hemodynamic and ICP data were recorded sequentially every 2 minutes for 10 minutes. The first device was turned off for 10 minutes, then it was removed and the second device was applied, and then the procedure was repeated for the second device. RESULTS: Ten patients with elevated ICP secondary to intracranial hemorrhage (n = 4), trauma (n = 2), obstructive hydrocephalus (n = 2), or diffuse cerebral processes (n = 2) were enrolled. Baseline ICP ranged from 12 to 38 mm Hg. With device application, a decrease in ICP was observed in 16 of 20 applications. During treatment with the -5 mm Hg device, there was a mean maximal decrease of 3.3 mm Hg in ICP (21.7 vs 18.4 mm Hg, p = 0.003), which was associated with an increase in CPP of 6.5 mm Hg (58.2 vs 64.7 mm Hg, p = 0.019). During treatment with the -9 mm Hg device, there was a mean maximal decrease of 2.4 mm Hg in ICP (21.1 vs 18.7 mm Hg, p = 0.044), which was associated with an increase in CPP of 6.5 mm Hg (59.2 vs 65.7 mm Hg, p = 0.001). CONCLUSIONS: This pilot study demonstrates that use of the ITPR in patients with altered intracranial elastance is feasible. Although this study was not powered to demonstrate efficacy, these data strongly suggest that the ITPR may be used to rapidly lower ICP and increase CPP without apparent adverse effects. Additional studies will be needed to assess longitudinal changes in ICP when the device is in use and to delineate treatment parameters.

Ultrasound-guided common peroneal nerve block at the level of the fibular head.

A common peroneal nerve block at the fibular head is uncommon in clinical practice. The case of a 41 year old, morbidly obese woman requiring right total ankle replacement is presented. Ultrasound-guided common peroneal nerve block was performed at the fibular head after an unsuccessful popliteal approach.

The effect of the intrathoracic pressure regulator on hemodynamics and cardiac output.

The intrathoracic pressure regulator (ITPR) (CirQLator; Advanced Circulatory Systems Inc, Roseville, Minn) is a novel, noninvasive device intended to increase cardiac output and blood pressure in hypovolemic or cardiogenic shock by generating a continuous low-level intrathoracic vacuum in between positive pressure ventilations. Although there are robust data supporting the benefit of the ITPR in multiple animal models of shock, the device has not been used in humans.The goals of this study were to evaluate both the safety and efficacy of the ITPR in humans. Twenty patients undergoing coronary artery bypass graft surgery were enrolled in this phase 1 study. Intraoperative use of both pulmonary artery pressure monitoring and transesophageal echocardiography (TEE) was required for study inclusion. Hemodynamic variables as well as TEE measurements of left ventricular performance were collected at baseline and after the ITPR device was activated, before surgical incision. Thermodilution cardiac output increased significantly with the application of the ITPR (4.9 vs. 5.5 L/min; P = 0.017). Similarly, cardiac output was measured by TEE (5.1 vs. 5.7 L/min; P = 0.001).There were significant increases in pulmonary artery systolic blood pressures (35 vs. 38 mmHg; P G 0.001) and mean pulmonary artery pressures (24 vs. 26 mmHg; P = 0.008). There were no significant differences in systemic blood pressures, left ventricular volumes, stroke volume, or ejection fraction as measured by TEE. Using two different measurement techniques, application of the ITPR increased cardiac output in normovolemic anesthetized patients who underwent coronary artery bypass graft before sternotomy. These data suggest that the ITPR has the potential to safely and effectively increase cardiac output in humans.

Intraoperative factors and the risk of respiratory complications after pneumonectomy.

BACKGROUND: The potential effect of intraoperative factors on respiratory complications after pneumonectomy is still unclear. METHODS: We conducted a retrospective cohort study; charts of 129 patients who underwent elective pneumonectomy at the University of Virginia were reviewed. Logistic regression was used to estimate the effect of anesthetic factors on the odds of at least one respiratory complication. Linear regression models were fit to assess the impact of these outcomes on length of stay (LOS). RESULTS: The incidence of respiratory complications in this cohort was 21%. In univariate analysis total nonblood fluids (p = 0.001), and the blood products packed red blood cells (p < 0.001), plasma (p < 0.001), and platelets (p = 0.044) were significantly associated with respiratory complications. In a multivariable logistic regression analysis, single unit transfusion of any blood product (packed red blood cells, plasma, or platelets) was identified as a major risk factor for respiratory complications after controlling for covariates (odds ratio = 1.47, 95% confidence interval 1.06 to 2.05). Respiratory failure and complications were closely related to LOS, increasing the LOS by a factor of 4.7 (95% confidence interval 3.51 to 6.18) and 3.5 (95% confidence interval 2.69 to 4.41), respectively. CONCLUSIONS: Blood product transfusion affects respiratory function and is an independent risk factor for respiratory complications after pneumonectomy.

Ultrasound does not improve the success rate of a deep peroneal nerve block at the ankle.

BACKGROUND: The deep peroneal nerve is 1 of 5 nerves anesthetized when performing an ankle block. Multiple techniques of blocking the deep peroneal nerve have been described, but little evidence exists to delineate the efficacy of any one technique. We hypothesized that ultrasound would increase both the success rate and the quality of a deep peroneal nerve block at the ankle. METHODS: Eighteen healthy volunteers participated in this randomized, controlled, prospective study. Each subject was randomly assigned to receive an ultrasound-guided deep peroneal nerve block of either the right or the left ankle. The deep peroneal nerve on the opposite side was blocked using a conventional landmark technique. Subjects were blinded to the technique used. All blocks were preformed with 5 mL of 3% 2-chloroprocaine. We evaluated both sensory and motor blocks at 10-min intervals for 60 mins. RESULTS: Blocks were maximal in both groups at 20 to 30 mins. There was a statistically significant difference in temperature sensation and motor function at 10 mins favoring the ultrasound group. There was no statistical difference in motor function, temperature, or pinprick sensation between 20 and 60 mins. CONCLUSIONS: The use of ultrasound seems to improve the onset of deep peroneal nerve block at the ankle but does not improve the overall quality of the block.