Caron M. Hong

Hemorrhagic Progression of a Contusion after Traumatic Brain Injury: A Review

The magnitude of damage to cerebral tissues following head trauma is determined by the primary injury, caused by the kinetic energy delivered at the time of impact, plus numerous secondary injury responses that almost inevitably worsen the primary injury. When head trauma results in a cerebral contusion, the hemorrhagic lesion often progresses during the first several hours after impact, either expanding or developing new, non-contiguous hemorrhagic lesions, a phenomenon termed hemorrhagic progression of a contusion (HPC). Because a hemorrhagic contusion marks tissues with essentially total unrecoverable loss of function, and because blood is one of the most toxic substances to which the brain can be exposed, HPC is one of the most severe types of secondary injury encountered following traumatic brain injury (TBI). Historically, HPC has been attributed to continued bleeding of microvessels fractured at the time of primary injury. This concept has given rise to the notion that continued bleeding might be due to overt or latent coagulopathy, prompting attempts to normalize coagulation with agents such as recombinant factor VIIa. Recently, a novel mechanism was postulated to account for HPC that involves delayed, progressive microvascular failure initiated by the impact. Here we review the topic of HPC, we examine data relevant to the concept of a coagulopathy, and we detail emerging data elucidating the mechanism of progressive microvascular failure that predisposes to HPC after head trauma.

Biomarkers as outcome predictors in subarachnoid hemorrhage – a systematic review

Abstract Context: Subarachnoid hemorrhage (SAH) has a high fatality rate and many suffer from delayed neurological deficits. Biomarkers may aid in the identification of high-risk patients, guide treatment/management and improve outcome. Objective: The aim of this review was to summarize biomarkers of SAH associated with outcome. Methods: An electronic database query was completed, including an additional review of reference lists to include all potential human studies. Results: A total of 298 articles were identified; 112 were reviewed; 55 studies were included. Conclusion: This review details biomarkers of SAH that correlate with outcome. It provides the basis for research investigating their possible translation into the management of SAH patients.

Increased ICU resource needs for an academic emergency general surgery service

Objective:ICU needs of nontrauma emergency general surgery patients are poorly described. This study was designed to compare ICU utilization of emergency general surgery patients admitted to an acute care emergency surgery service with other general surgery patients. Our hypothesis is that tertiary care emergency general surgery patients utilize more ICU resources than other general surgical patients. Design:Retrospective database review. Setting:Academic, tertiary care, nontrauma surgical ICU. Patients:All patients admitted to the surgical ICU over age 18 between March 2004 and June 2012. Interventions:None. Measurements and Main Results:Six thousand ninety-eight patients were evaluated: 1,053 acute care emergency surgery, 1,964 general surgery, 1,491 transplant surgery, 995 facial surgery/otolaryngology, and 595 neurosurgery. Acute care emergency surgery patients had statistically significantly longer ICU lengths of stay than other groups: acute care emergency surgery (13.5 ± 17.4 d) versus general surgery (8.7 ± 12.9), transplant (7.8 ± 11.6), oral-maxillofacial surgery (5.5 ± 4.2), and neurosurgery (4.47 ± 9.8) (all p< 0.01). Ventilator usage, defined by percentage of total ICU days patients required mechanical ventilation, was significantly higher for acute care emergency surgery patients: acute care emergency surgery 73.4% versus general surgery 64.9%, transplant 63.3%, oral-maxillofacial surgery 58.4%, and neurosurgery 53.1% (all p < 0.01). Continuous renal replacement therapy usage, defined as percent of patients requiring this service, was significantly higher in acute care emergency surgery patients: acute care emergency surgery 10.8% versus general surgery 4.3%, transplant 6.6%, oral-maxillofacial surgery 0%, and neurosurgery 0.5% (all p < 0.01). Acute care emergency surgery patients were more likely interhospital transfers for tertiary care services than general surgery or transplant (24.5% vs 15.5% and 8.3% respectively, p < 0.001 for each) and more likely required emergent surgery (13.7% vs 6.7% and 3.5%, all p < 0.001). Chronic comorbidities were similar between acute care emergency surgery and general surgery, whereas transplant had fewer. Conclusions:Emergency general surgery patients have increased ICU needs in terms of length of stay, ventilator usage, and continuous renal replacement therapy usage compared with other services, perhaps due to the higher percentage of transfers and emergent surgery required. These patients represent a distinct population. Understanding their resource needs will allow for better deployment of hospital resources.

Patients with chronic pulmonary disease.

Chronic pulmonary disease is common among the surgical population and the importance of a thorough and detailed preoperative assessment is monumental for minimizing morbidity and mortality and reducing the risk of perioperative pulmonary complications. These comorbidities contribute to pulmonary postoperative complications, including atelectasis, pneumonia, and respiratory failure, and can predict long-term mortality. The important aspects of the preoperative assessment for patients with chronic pulmonary disease, and the value of preoperative testing and smoking cessation, are discussed. Specifically discussed are preoperative pulmonary assessment and management of patients with chronic obstructive pulmonary disease, asthma, restrictive lung disease, obstructive sleep apnea, and obesity.

Practical considerations for the dosing and adjustment of continuous renal replacement therapy in the intensive care unit.

Familiarity with the initiation, dosing, adjustment, and termination of continuous renal replacement therapy (CRRT) is a core skill for contemporary intensivists. Guidelines for how to administer CRRT in the intensive care unit are not well documented. The purpose of this review is to discuss the modalities, terminology, and components of CRRT, with an emphasis on the practical aspects of dosing, adjustments, and termination. Management of electrolyte and acid-base derangements commonly encountered with acute renal failure is emphasized. Knowledge regarding the practical aspects of managing CRRT in the intensive care unit is a prerequisite for achieving desired physiological end points.

Inducible nitric oxide synthase (NOS-2) in subarachnoid hemorrhage: Regulatory mechanisms and therapeutic implications

Aneurysmal subarachnoid hemorrhage (SAH) typically carries a poor prognosis. Growing evidence indicates that overabundant production of nitric oxide (NO) may be responsible for a large part of the secondary injury that follows SAH. Although SAH modulates the activity of all three isoforms of nitric oxide synthase (NOS), the inducible isoform, NOS-2, accounts for a majority of NO-mediated secondary injuries after SAH. Here, we review the indispensable physiological roles of NO that must be preserved, even while attempting to downmodulate the pathophysiologic effects of NO that are induced by SAH. We examine the effects of SAH on the function of the various NOS isoforms, with a particular focus on the pathological effects of NOS-2 and on the mechanisms responsible for its transcriptional upregulation. Finally, we review interventions to block NOS-2 upregulation or to counteract its effects, with an emphasis on the potential therapeutic strategies to improve outcomes in patients afflicted with SAH. There is still much to be learned regarding the apparently maladaptive response of NOS-2 and its harmful product NO in SAH. However, the available evidence points to crucial effects that, on balance, are adverse, making the NOS-2/NO/peroxynitrite axis an attractive therapeutic target in SAH.

Focused Comprehensive, Quantitative, Functionally Based Echocardiographic Evaluation in the Critical Care Unit is Feasible and Impacts Care

OBJECTIVES To determine whether comprehensive quantitative echocardiogram could be used as a resuscitation tool in critically ill surgical patients and to assess its effect on patient care. DESIGN Prospective observational. SETTING The Trauma and Surgical Intensive Care Units of the University of Maryland Medical Center. PATIENTS Critically ill trauma and surgical patients. INTERVENTIONS The Focused Rapid Echocardiographic Evaluation (FREE), an abbreviated version of a comprehensive transthoracic echocardiogram, which is under an approved protocol, was performed. MEASUREMENTS AND MAIN RESULTS Over a 30-month period, 791 FREEs were performed on 659 patients. The mean patient age was 60 (±17) years. Ninety-one percent were intubated and 80% were postoperative. Ejection fraction was reported for 95%, and cardiac index was reported for 89% of FREE studies. Right heart function was assessed for 94%. Measures of volume status--internal left ventricular diameter, inferior vena cava diameter, diameter change, and stroke volume variation--were reported for 88%, 79%, 75%, and 89% of patients, respectively. The FREE was judged to be useful by the consulting primary care team for 95% of patients, and altered the plan of care for 57%. The most common change was administration of a fluid bolus (43%), followed by change from an original prestudy plan to one of monitoring (24%), diuresis (23%), addition/titration of an inotropic agent (19%), and/or addition/titration of a vasoconstrictor (8%). CONCLUSIONS The FREE is feasible and alters care in the intensive care unit by providing clinical data not otherwise available at the bedside. Further studies are warranted to assess the impact of comprehensive echocardiogram-directed resuscitation on patient outcomes.

Perioperative temperature measurement and management: moving beyond the Surgical Care Improvement Project

Abstract Intraoperative management of patient body temperature is a standard of care for practicing anesthesiologists. Merely complying with the Surgical Care Improvement Project (SCIP) measurement is inadequate for optimizing

Angiogenesis induced by prenatal ischemia predisposes to periventricular hemorrhage during postnatal mechanical ventilation

Background:Three risk factors are associated with hemorrhagic forms of encephalopathy of prematurity (EP): (i) prematurity, (ii) in utero ischemia (IUI) or perinatal ischemia, and (iii) mechanical ventilation. We hypothesized that IUI would induce an angiogenic response marked by activation of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9), the latter degrading vascular basement membrane and increasing vulnerability to raised intravenous pressure during positive pressure mechanical ventilation.Methods:We studied a rat model of hemorrhagic-EP characterized by periventricular hemorrhages in which a 20-min episode of IUI is induced at E19, pups are born naturally at E21-22, and on P0, are subjected to a 20-min episode of positive pressure mechanical ventilation. Tissues were studied by H&E staining, immunolabeling, immunoblot, and zymography.Results:Mechanical ventilation of rat pups 2–3 d after 20-min IUI caused widespread hemorrhages in periventricular tissues. IUI resulted in upregulation of VEGF and MMP-9. Zymography confirmed significantly elevated gelatinase activity. MMP-9 activation was accompanied by severe loss of MMP-9 substrates, collagen IV and laminin, in microvessels in periventricular areas.Conclusion:Our findings are consistent with the hypothesis that positive pressure mechanical ventilation of the newborn in the context of recent prenatal ischemia/hypoxia can predispose to periventricular hemorrhages.

Systemic inflammatory response does not correlate with acute lung injury associated with mechanical ventilation strategies in normal lungs.

BACKGROUND: Mechanical ventilation (MV) can lead to ventilator-induced lung injury secondary to trauma and associated increases in pulmonary inflammatory cytokines. There is controversy regarding the associated systemic inflammatory response. In this report, we demonstrate the effects of MV on systemic inflammation. METHODS: This report is part of a previously published study (Hong et al. Anesth Analg 2010;110:1652–60). Female pigs were randomized into 3 groups. Group H-VT/3 was ventilated with a tidal volume (VT) of 15 mL/kg predicted body weight (PBW)/positive end-expiratory pressure (PEEP) of 3 cm H2O; group L-VT/3 with a VT of 6 mL/kg PBW/PEEP of 3 cm H2O; and group L-VT/10 with a VT of 6 mL/kg PBW/PEEP of 10 cm H2O, for 8 hours. Each group had 6 subjects (n = 6). Prelung and postlung sera were analyzed for inflammatory markers. Hemodynamics, airway mechanics, and arterial blood gases were monitored. RESULTS: There were no significant differences in systemic cytokines among groups. There were similar trends of serum inflammatory markers in all subjects. This is in contrast to findings previously published demonstrating increases in inflammatory mediators in bronchoalveolar lavage. CONCLUSION: Systemic inflammatory markers did not correlate with lung injury associated with MV.