Avinash B. Kumar

Cardiopulmonary bypass-associated acute kidney injury.

A PPROXIMATELY 300,000 patients undergo cardiac surgical procedures each year in the United States. More than 80% of routine cardiac surgical procedures are performed using cardiopulmonary bypass (CPB). Acute kidney injury (AKI; previously referred to as acute renal failure) after CPB is a well-known, yet incompletely understood, entity that has significant implications on both shortand long-term outcomes. The development of AKI after CPB is associated with a significant increase in infectious complications, an increase in length of hospital stay, and greater mortality when compared with patients without AKI-CPB. The incidence of AKI-CPB averages 20–30%, depending on the definition used and the duration of the postoperative period studied. Furthermore, more patients with AKI-CPB who require dialysis remain dialysis dependant. For all patients undergoing CPB, the risk of AKI-CPB is the least in those who undergo coronary artery bypass grafting (CABG) only; the risk increases for patients undergoing valve replacement surgery; and the risk is the greatest after combined CABGvalve procedures. There has not been a significant reduction in mortality, despite many recent advances in our understanding of the causative pathophysiology and pharmacotherapeutics of AKI-CPB. Furthermore, advances in renal replacement therapies (RRTs) have not significantly altered the overall mortality associated with AKI-CPB. In this review, we will focus on the current definitions of AKI, pathophysiologic features, and risk factors for developing AKI-CPB. We will also discuss perioperative strategies and emerging concepts that add to our understanding of this complex entity to help better manage patients at risk for AKI-CPB.

Association Between Postoperative Acute Kidney Injury and Duration of Cardiopulmonary Bypass: A Meta-Analysis

OBJECTIVEnThis meta-analysis examined the association between cardiopulmonary bypass (CPB) time and acute kidney injury (AKI).nnnDESIGNnMeta-analysis of previously published studies.nnnSETTINGnEach single-center study was conducted in a surgical intensive care unit and/or academic or university hospital.nnnPARTICIPANTSnAdult patients undergoing heart surgery with CPB.nnnINTERVENTIONSnA systematic literature review was conducted using PubMed, EMBASE, and Cochrane Library databases and Google Scholar from January 1980 through September 2009. Initial search results were refined to include human subjects, age >18 years, randomized controlled trials, and prospective and retrospective cohort studies, meet the Acute Kidney Injury Network definition of renal failure, and report times on CPB.nnnMEASUREMENTS AND MAIN RESULTSnThe length of time on CPB has been implicated as an independent risk factor for development of AKI after CPB (AKI-CPB). The 9 independent studies included in the final meta-analysis had 12,466 patients who underwent CPB. Out of these, 756 patients (6.06%) developed AKI-CPB. In 7 of the 9 studies, the mean CPB times were statistically longer in the AKI-CPB cohort compared with the control group (cohort without AKI). The absolute mean differences in CPB time between the 2 groups were 25.65 minutes with the fixed-effects model and 23.18 minutes with the random-effects model.nnnCONCLUSIONSnLonger CPB times are associated with a higher risk of developing AKI-CPB, which, in turn, has a significant effect on overall mortality as reported by the individual studies.

Implementing a hybrid web-based curriculum for an elective medical student clerkship in a busy surgical intensive care unit (ICU): effect on test and satisfaction scores.

OBJECTIVEnTo determine whether a hybrid traditional and web-based curriculum improves test scores and enrollment among senior medical students in an elective critical care rotation.nnnDESIGN AND SETTINGnRetrospective study in a surgical ICU at a major academic center.nnnSUBJECTSnOne hundred twenty-one fourth year medical students completing an elective ICU clerkship between 2007 and 2010.nnnINTERVENTIONSnPre-test and post-test during a 4-week rotation.nnnMETHODSnWe implemented a hybrid curriculum that involved both traditional teaching methods and a new online core curriculum that incorporating audio, video, and text using screen capture technology. The curriculum was hosted on a secure online portal called ICON (Desire2Learn Inc., Ontario, Canada). The core curriculum covered topics that were considered essential to meet the didactic objectives of the rotation. MEASUREMENTS AND EVALUATIONS: A pre-test was administered online on day 1 of the rotation. A post-test was administered on the second to last day of the rotation. Both tests were composed of 20 questions randomly chosen from a question bank of 100 questions. The tests are managed (administering, grading, and reporting) exclusively online.nnnRESULTSnOne hundred twenty-one medical students have successfully completed the clerkship since implementing the new curriculum. Each group of students showed an improvement in the mean post-test score by at least 17%+ to 10%. The satisfaction scores of the clerkship improved consistently from 2007 and is currently rated at 4.31 ± 0.85 (on a 5-point scale). The rotation is in the top 25(th) percentile of all clinical clerkships offered at the University of Iowa.nnnCONCLUSIONnA systematically implemented hybrid web-based critical care curriculum can improve knowledge based test scores and overall clerkship satisfaction scores in a busy surgical ICU.

The acute effectiveness and safety of the constant-flow, pressure-volume curve to improve hypoxemia in acute lung injury.

Objective: To investigate the effectiveness of the constant-flow, pressure-volume curve (PVC) to prescribe positive end-expiratory pressure (PEEP) in acute lung injury (ALI) and risk of cardiopulmonary deterioration during the PVC process. Design: A retrospective, cohort study. Setting: A surgical intensive care unit (ICU) of a tertiary, university hospital. Patients: Fifty consecutive ventilated patients diagnosed with ALI undergoing the PVC maneuver from 1999 to 2003. Interventions: Titration of PEEP based on the lower inflection point of the constant-flow, pressure-volume curve. Measurements and Main Results: Patients were divided into 2 groups based on PVC-guided PEEP changes of <3 cm H2O (PVC-NC or “no change”) or ≥3 cm H2O (PVC-CHG or “change”) from the initial empiric prescription. There was a greater increase in partial pressure of arterial oxygen (PaO2)/fractional concentration of inspired oxygen (FiO2) in the PVC-CHG group, with a mean change of 80 ± 50 (95% confidence interval [CI] 61, 98) versus 42 ± 54 (95% CI 17, 67) in the PVC-NC group. Eighty-two percent of patients (41/50) showed an increase in ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2) by 20% within 6 to 24 hours after the PVC test—greater in the PVC-CHG group (OR 1.44, 95% CI 1.02, 2.01). Thirteen percent (4/30) within the PVC-CHG group and none within the PVC-NC group (0/20) required a 25% increase in vasoactive infusion rates (P = .089) in relation to the procedure. Univariate logistic regression showed that PVC-CHG was significantly associated with a 20% change in PaO2/FiO2 (OR 7.54, 95% CI 1.37, 41.41). Multivariate logistic modeling showed that PVC-guided PEEP changes of ≥3 cm H2O, age ≤65 years, and pre-PVC FiO2 ≥.85 were significantly associated with a 20% increase in PaO2/FiO2 (receiver operator area under the curve = .86). Conclusions: In the setting of acute lung injury, use of the constant-flow, pressure-volume curve to prescribe PEEP appears associated with improvement in oxygenation with limited risk of acute, process-related, cardiopulmonary deterioration.

Hetastarch-induced Osmotic Nephrosis

A 63-YR-OLD male (weighing approximately 83 kg) with no significant past medical history underwent an open reduction and internal fixation of his femur fracture under general anesthesia. He had been nil per os for 14 h and his preoperative blood pressure was 136/74 mmHg. Intraoperative course was uneventful, except for a 5–7 min episode of relative hypotension with systolic pressures 80 – 85 mmHg. He received 500 ml of 6% Hetastarch (Hospira, Lake Forest, IL) during this episode, and another 500 ml of 6% Hetastarch was started and completed during the case. His baseline serum creatinine was 1.1 mg/dl. He was oliguric on postoperative day 3 and his serum creatinine increased to 3.8 mg/ dl. Urinalysis was consistent with acute tubular necrosis (muddy casts and tubular epithelial cells). A kidney biopsy was performed (image) considering a differential diagnosis of acute tubular necrosis, drug-induced nephrotoxicity, and interstitial nephritis. However, a histopathologic diagnosis of osmotic nephrosis was made. Osmotic nephrosis is characterized by extensive vacuolization, clear cell transformation, and swelling of the proximal tubular epithelial cells with nuclei being displaced toward the basal membranes. The vacuoles in the proximal tubules are formed by the fusion of pinocytic vesicles (often containing the offending agent) and lysosomes containing hydrolytic enzymes. Distal tubules and collecting ducts are usually not affected. Osmotic nephrosis has been reported with other osmotically active compounds, including mannitol, dextran-40, and iodinated contrast media. Osmotic nephrosis (biopsy diagnosis) is an often unrecognized and frequently reversible cause of acute kidney injury. The choice of colloid may play a role in the pathophysiology of acute kidney injury and should be considered in the differential diagnosis. This patient’s creatinine returned to baseline at the time of discharge from the hospital.

Refractory caffeine and ergot-induced cervico-cerebral vasospasm and stroke treated with combined medical and endovascular approach

Dear Sir, We wish to bring to your attention a case of stroke secondary to cervico-cerebral vasospasm after IV caffeine and Dihydroergotamine (DHE) 45 for status migrainosus. Early aggressive multidisciplinary management resulted in a good neurological outcome, despite severe neurological disease. This 28-year-old right-handed woman was transferred to our tertiary care facility for spastic quadriparesis following 13-day treatment of status migrainosus with an aggressive combined oral and intravenous caffeine and DHE 45 regimen. The day prior to transfer, she developed fluctuating cognitive status and quadriparesis, ranging from mild weakness to complete quadriplegia. MRI done prior to transfer showed bilateral acute infarction in the hemispheric watershed regions. MRA demonstrated diffuse cervical and cerebral sausage-like constrictions and dilatations most consistent with vasospasm (Fig. 1). The patients past medical history was only positive for infrequent migraine headaches. She was a non-smoker and denied drug use. On initial examination, she demonstrated a fluctuating level of consciousness and orientation with asymmetric spastic quadriparesis. Her National Institute of Health Stroke Scale (NIHSS) score was 14. Laboratory examination, including electrolytes, complete blood counts, CSF analysis, as well as urine drug screen and pregnancy tests, were unremarkable. She underwent emergent cerebral angiography demonstrating severe diffuse vasospasm of all cervical and cerebralvascular territories (Fig. 2). Intra-arterial (IA) nicardipine was administered to multiple territories resulting in angiographic (Fig. 3) and clinic improvement to near baseline neurological status. She was admitted to the surgical intensive care unit and subsequently treated with dual anti-platelet agents, triple-H therapy with an augmented cardiac index (CI) >3.5 L/min m guided by lithium dilution cardiac monitor (LiDCO®-Lidco systems IL, USA), oral (PO) nimodipine, and IV nicardipine. On hospital day (HD) 3, her exam deteriorated necessitating repeat angiography and administration of IA nicardipine, which again resulted in angiographic and clinic improvement. On HDs 4 and 7, attempts to wean IV nicardipine were unsuccessful, resulting in neurological deterioration. Both vasospasm episodes were again successfully treated with combined IA nicardipine and stent-assisted angioplasty of the left cervical vertebral artery. Over the course of the hospitalization, HHH therapy was weaned and IV nicardipine was transitioned to oral nimodipine. She was discharged on HD 11 without patient therapies. At 3-month follow-up, her NIHSS was 0 and MRA demonstrated normal cervicocerebral vasculature (Fig. 4). Caffeine and ergotamine use in status migrainosus are well-accepted therapies for this often difficult-to-treat M. Miller :A. B. Kumar Department of Anesthesia, University of Iowa Hospitals and Clinics, Iowa City, IA, USA

Is inhalation burn injury an independent risk factor for acute kidney injury: a retrospective study

Crit Care Med 2015 • Volume 43 • Number 12 (Suppl.) matched-control study evaluated dronabinol as an adjunct therapy for acute pain management in burn patients that used marijuana as an outpatient. The control group was comprised of patients who did not receive dronabinol nor had a history of marijuana use. Patients were matched in a 1:1 fashion based on age, sex, weight, length of intubation, and total burn surface area. The primary outcome was the amount of opioids used per day over the first 14 days of admission. Secondary outcomes included other pharmacologic interventions, mean pain scores, and length of stay. Results: Thirty-two patients who met inclusion criteria for the dronabinol group were matched to 32 control patients. Baseline demographics were statistically similar between groups. Mean total burn surface area was 13.3% and 12.7% in the dronabinol and control groups, respectively. The dronabinol and control groups used a median of 56.3 mg (IQR 44.8–72.7) and 43.2 mg (IQR 30.3–60) of IV morphine equivalents (EQs), respectively (p=0.02). The dronabinol group used a median of 1.58 mg (IQR 0.8–2.3) lorazepam EQs per day vs. 0.7 mg (IQR 0.4–1.5) in the control group (p=0.006). The dronabinol group used more antiemetics, ketorolac, and ketamine. There were no differences in mean pain scores or length of stay. Conclusions: Patients in the dronabinol group required greater amounts of analgesic, anxiolytic, and antiemetic medications. Causality remains unknown. Future studies consisting entirely of patients that use marijuana are warranted to more accurately assess the benefit of cannabinoid supplementation in acute pain management.

Successful Echocardiography-Guided Management of Refractory Postoperative Hypotension After Alfieri Repair of the Mitral Valve

We read with interest the article by Maslow et al titled ‘‘Problems With Excess Mitral Leaflet After Repair: Possible Issues During Repair and Preservation of the Posterior Leaflet.’’ We share our experience of successfully managing a case of refractory hypotension and deteriorating hemodynamics in a patient after Alfieri repair of the mitral valve for severe mitral regurgitation (MR). Managing refractory postoperative hypotension can be especially challenging in the post–cardiac surgery patient. The availability of point-of-care echocardiography in the intensive care unit has greatly enhanced our ability to manage these complex patients. A 75-year-old woman successfully underwent Alfieri repair of the mitral valve with annuloplasty for grade IV MR. The procedure was completed with a #28 Cosgrove Edwards annuloplasty ring (Edwards Lifesciences, Irvine, CA) and an asymmetric edge-to-edge repair of the P1-P2 and A1 and A2 of the mitral leaflets. Preoperative echocardiography showed a normal left ventricular ejection fraction of 65% with severe MR, severe tricuspid regurgitation (right ventricular/right atrial peak instantaneous gradient 1⁄4 70 mmHg), and a known fixed left ventricular outflow tract gradient of 30 mmHg. Within 3 to 4 hours of admission to the intensive care unit, she developed significant hypotension with mean arterial pressures dipping to 40 mmHg with cardiac indices o1.8 L/min/m. Epinephrine, norepinephrine,