Aristides Koutrouvelis

Cellular Mechanisms That Cause Suppressed Gamma Interferon Secretion in Endotoxin-Tolerant Mice

ABSTRACT Endotoxin (lipopolysaccharide [LPS]) tolerance is a state of altered immunity characterized, in part, by suppression of LPS-induced gamma interferon (IFN-γ) expression. However, the cellular mediators regulating LPS-induced production of IFN-γ in normal mice and the effect of LPS tolerance on these mediators has not been well characterized. Our studies show that macrophage dysfunction is the primary factor causing suppressed IFN-γ expression in LPS-tolerant mice. Specifically, LPS-tolerant macrophages have a markedly impaired ability to induce IFN-γ secretion by T cells and NK cells obtained from either control or LPS-tolerant mice. However, T cells and NK cells isolated from LPS-tolerant mice produce normal levels of IFN-γ when cocultured with control macrophages or exogenous IFN-γ-inducing factors. Assessment of important IFN-γ-regulating factors showed that interleukin-12 (IL-12) and costimulatory signals provided by IL-15, IL-18, and CD86 are largely responsible for LPS-induced IFN-γ expression in control mice. IL-10 is an inhibitor of IFN-γ production in both the control and LPS-tolerant groups. Expression of IL-12 and the IL-12 receptor β1 (IL-12Rβ1) and IL-12Rβ2 subunits are suppressed in the spleens of LPS-tolerant mice. LPS-tolerant splenocytes also exhibit decreased production of IL-15 and IL-15Rα. However, expression of IL-18 and the B7 proteins CD80 and CD86 are unchanged or increased compared to controls after induction of LPS tolerance. CD28, a major receptor for B7 proteins, is also increased in the spleens of LPS-tolerant mice. Expression of the inhibitory cytokine IL-10 and the IL-10R are sustained after induction of LPS tolerance. These data show that suppression of IFN-γ production in LPS-tolerant mice is largely due to macrophage dysfunction and provide insight into the cellular alterations that occur in LPS tolerance. This study also better defines the factors that mediate LPS-induced IFN-γ production in normal mice.

Glucan phosphate potentiates endotoxin-induced interferon-γ expression in immunocompetent mice, but attenuates induction of endotoxin tolerance

Glucan phosphate has been shown to enhance antimicrobial immunity in a variety of experimental models. However, the mechanisms by which glucans enhance resistance to infection remain largely unknown. Interferon-gamma (IFN-gamma) is a key regulator of both innate and acquired immunity. Suppression of IFN-gamma production is a prominent feature of the altered immune response that follows major trauma or sepsis. The present studies were designed to determine the effect of glucan phosphate on IFN-gamma expression in normal mice and endotoxin [lipopolysaccharide (LPS)]-tolerant mice. The model of LPS tolerance was used because it results in patterns of cytokine expression similar to those commonly observed following severe trauma or sepsis. Glucan treatment potentiated LPS-induced IFN-gamma expression in control mice. The induction of LPS tolerance resulted in marked suppression of LPS-induced IFN-gamma production. However, co-administration of glucan with LPS, during the tolerance induction phase, attenuated the LPS-tolerant response. Interleukin-12 (IL-12) and IL-18 are important mediators of LPS-induced IFN-gamma production. LPS-induced IL-12 p40 mRNA expression was increased in the spleens of glucan-treated mice compared with controls. Induction of LPS tolerance caused marked suppression of IL-12 production, a response that was attenuated by glucan treatment. IL-18 was constitutively expressed in both control and LPS-tolerant mice, and LPS-induced serum levels of IL-18 were increased in mice treated with glucan. T cells isolated from glucan-treated mice exhibited increased IFN-gamma expression in response to IL-12 and IL-18, as well as increased expression of the IL-12 and IL-18 receptors. The ability of glucan to potentiate IFN-gamma expression in control mice provides a potential mechanism by which glucan enhances antimicrobial immunity. The ability of glucan to attenuate suppressed IFN-gamma expression in LPS-tolerant mice denotes its potential benefit for the treatment of trauma and sepsis-induced immunosuppression.

Intraocular pressure and steep trendelenburg during minimally invasive gynecologic surgery: Is there a risk?

STUDY OBJECTIVE Steep Trendelenburg position is frequently used during gynecologic minimally invasive surgery (MIS). However, little attention has been given to the potential impact of this nonphysiologic positioning on patients, specifically intraocular pressure (IOP). The purpose of our study was to evaluate IOP changes during laparoscopic or robotic hysterectomy conducted in the steep Trendelenburg position. DESIGN Prospective cohort study (Canadian Task Force classification II-2). SETTING John Sealy Hospital at the University of Texas Medical Branch, Galveston, TX. PATIENTS Female patients with no history of ocular pathology who underwent elective robotic or laparoscopic hysterectomy. INTERVENTIONS The anesthesia protocol was standardized for all study patients. IOP and mean arterial pressure (MAP) were obtained before anesthesia, after general anesthesia and intubation were achieved, after 1 hour of steep Trendelenburg positioning, after 2 hours of steep Trendelenburg positioning, and after the patient was returned to the supine position. Ocular perfusion pressure (OPP) was calculated using the following equation: OPP = MAP - IOP. MAIN RESULTS A total of 10 patients were included in this prospective study. A significant increase in IOP from baseline was observed after 1 hour and 2 hours of steep Trendelenburg positioning (p = .005 and .002, respectively). There was a statistically significant trend of increasing the IOP from baseline to the second hour of steep Trendelenburg positioning (p < .001). The IOP remained significantly elevated once the patient was returned to the supine position when compared with the baseline IOP (p = .006). OPP significantly decreased from baseline after 2 hours of steep Trendelenburg positioning (p = .03). CONCLUSIONS IOP increases significantly when patients are placed in the steep Trendelenburg position. Although further studies are needed to better characterize this process, given the aging population of our MIS patients in whom risk for glaucoma is significant, preoperative ocular health assessment should be considered in certain cases.

A THREE-DIMENSIONAL STEREOTACTIC DEVICE FOR COMPUTED TOMOGRAPHY-GUIDED INVASIVE DIAGNOSTIC AND THERAPEUTIC PROCEDURES

&NA; Koutrouvelis PG, Louie A, Lang E, Heilen R, Koulizakis EN, Koutrouvelis A. A three‐dimensional stereotactic device for computed tomography‐guided invasive diagnostic and therapeutic procedures. Invest Radiol 1993;28:845‐847. rationale and objectives. A three‐dimensional stereotactic technique is presented as an improvement in precision needle placement for percutaneous diagnostic and therapeutic procedures. methods. This method uses transaxial computed tomography (CT) imaging for the selection of the optimal target path, and it employs a three‐dimensional stereotactic device designed to match precisely the CT parameters in a three‐dimensional space. results. In selected cases, we reached targets as small as 1 to 2 cm while avoiding vital structures. conclusions. In our hands, in selected cases, this has been a simple, safe, and accurate technique for improvement of percutaneous diagnostic and therapeutic procedures under CT guidance.

Case Scenario: Emergency Reversal of Oral Anticoagulation

REVERSING warfarin-induced anticoagulation quickly and effectively can be challenging in medically compromised patients presenting for emergency surgery. Anticoagulation reversal poses a delicate balance between increasing the risk of clotting and decreasing the risk of intraoperative blood loss. Furthermore, variable individual responses and warfarin’s adverse effect profile render particular dosing challenges. Consequently, meticulous monitoring of anticoagulated patients with prothrombin time and international normalized ratio (INR) must guide titration. Traditionally, fresh frozen plasma (FFP) has been the mainstay of warfarin reversal. Herein, we present a case in which we administered prothrombin complex concentrate (PCC) instead of FFP to hasten INR correction, reduce volume requirements, and diminish immune-related risks.

Intrathoracic Pressure Regulation Augments Stroke Volume and Ventricular Function in Human Hemorrhage.

ABSTRACT Obtaining intravenous (i.v.) access for fluid administration is a critical step in treating hemorrhage. However, expertise, supplies, and personnel to accomplish this task can be delayed or even absent in austere environments. An alternative approach that can “buy time” and improve circulation when i.v. fluids are absent is needed. Preclinical studies show that intrathoracic pressure regulation (ITPR) can increase perfusion in hypovolemia in the absence of i.v. fluid. We compared ITPR with placebo in humans undergoing a 15% hemorrhage under general anesthesia. Paired healthy volunteers (n = 7, aged 21 – 35 years) received either ITPR or placebo on different study days. Institutional review board informed consent was obtained. Subjects were anesthetized using propofol, intubated, and mechanically ventilated and hemorrhaged (10 mL/kg). Twenty minutes after hemorrhage, ITPR (−12 cm H2O vacuum) or placebo (device but no vacuum) was administered for another 60 min. Intravenous fluid was administered when systolic blood pressure was less than 85 mmHg. Hemodynamics, cardiac function by echocardiography, and volumetric data were compared. Data were expressed in &Dgr;mean ± SEM before and after ITPR/placebo intervention. There were no differences in mean arterial pressure (ITPR, 2.1 ± 3 mmHg; placebo, −0.7 ± 3 mmHg) or fluid infused (ITPR, 17.4 ± 4 mL/kg; placebo, 18.6 ± 5 mL/kg). Urinary output and plasma volume also were not significantly different. Intrathoracic pressure regulation augmented stroke volume (ITPR, 22 ± 5 mL, placebo, 6 ± 4 mL; P < 0.05), ejection fraction (ITPR, 4% ± 1%; placebo, 0% ± 1%), and diastolic function (&Dgr;E/e′) (ITPR, −0.8 ± 0.4 vs. placebo, +0.81 ± 0.6; P < 0.05). Intrathoracic pressure regulation did not improve mean arterial pressure in healthy volunteers aged 21 to 35 years. However, ITPR augmented stroke volume, which could be caused by improved ventricular function.

Reversal Strategies for Intracranial Hemorrhage Related to Direct Oral Anticoagulant Medications

Direct oral anticoagulants (DOACs) are a new class of anticoagulants that directly inhibit either thrombin or factor Xa in the coagulation cascade. They are being increasingly used instead of warfarin or other vitamin K antagonists (VKAs). Adverse side effects of DOACs may result in hemorrhagic complications, including life-threatening intracranial hemorrhage (ICH), though to a much lesser degree than VKAs. Currently there are relatively limited indications for DOACS but their usage is certain to expand with the availability of their respective specific reversal agents. Currently, only idarucizumab (antidote for dabigatran) has been United States Food and Drug Administration- (FDA-) approved, but others (andexanet-α and ciraparantag) may be approved in near future, and the development and availability of such reversal agents have the potential to dramatically change the current anticoagulant use by providing reversal of multiple oral anticoagulants. Until all the DOACs have FDA-approved reversal agents, the treatment of the dreaded side effects of bleeding is challenging. This article is an attempt to provide an overview of the management of hemorrhage, especially ICH, related to DOAC use.

71: CARDIAC HEMODYNAMIC CHANGES DURING WEANING FROM MECHANICAL VENTILATION USING NICOM

Crit Care Med 2015 • Volume 43 • Number 12 (Suppl.) outcome during ECMO would be instrumental in managing these critically ill patients. Conventional quantitative echocardiographic measures performed during ECMO have not been predictive of successful decannulation. Strain echocardiography (SE) is capable of capturing subtle perturbations in function. To date, series describing use of SE in assessing ECMO patients and their potential outcomes in a general PICU population are nonexistent. Methods: Pediatric ECMO patients admitted to a tertiary medical/surgical PICU from 2014–2015 who received echocardiographic imaging (ECHO) were retrospectively analyzed. Initial and final ECHOs during the ECMO course were post-processed using SE analysis software. Strain and strain rate parameters were compared using t-test for patients successfully decannulated versus those who did not, and between patients receiving eCPR and nonemergent cannulation. Results: 24 patients with at least one ECHO while on ECMO were identified, with 17 surviving to decannulation. Half of the patients received eCPR. Diastolic circumferential strain rate (CSR) on initial ECHO was significantly greater in patients who were successfully decannulated from ECMO (p=0.033) compared to those who were not. Patients who received eCPR demonstrated significantly lower magnitude diastolic and systolic circumferential strain (CS) than patients cannulated nonemergently (p=0.046 and p=0.038, respectively). Systolic CSR magnitude was significantly less in those who underwent eCPR on initial ECHO (p=0.01). Lactate proximate to the time of ECHO was significantly correlated with both systolic CS and CSR (p=0.033 and p=0.043 respectively). Conclusions: Decreased CS parameters may indicate compromised cardiac function seen in shock and following eCPR in pediatric patients on ECMO. Higher magnitude diastolic CSR may also portend successful decannulation from ECMO. Further investigation could be instrumental in determining the utility of SE as an outcome assessment instrument in the PICU.