Low levels of nitric oxide as contaminant in hospital compressed air: physiologic significance?

Objectives: To determine whether the levels of nitric oxide found in hospital compressed air have a clinically relevant effect on oxygenation in intubated patients with normal lungs.

Design: Prospective study.

Setting: Cardiothoracic and surgical intensive care unit in a university hospital.

Contamination of hospital compressed air with nitric oxide: unwitting replacement therapy.

Background: Inhaled nitric oxide (NO) at levels between 5 and 80 ppm has been used experimentally to treat a variety of conditions. NO also is a common environmental air pollutant in industrial regions. As compressed hospital air is drawn from the local environment, we speculated that it may contain NO contamination, which, if present, would provide unwitting inhaled NO therapy to all subjects respiring this compressed gas.

Positive pressure inspiration differentially affects right and left ventricular outputs in postoperative cardiac surgery patients.

Purpose: The purpose of this study was to determine the dynamic changes in right ventricular (RV) and left ventricular (LV) output during positive airway pressure inspiratory hold maneuvers so as to characterize the interaction of processes in creating steady-state cardiac output during positive pressure ventilation.

Materials And Methods: We examined the disparity of RV and LV outputs at 5 seconds (early) and 20 seconds (late) into a 24-second inspiratory hold maneuver in 14 subjects in the intensive care unit immediately following coronary artery bypass surgery. RV output was measured by the thermodilution technique, whereas LV output was measured by the arterial pulse contour method.

Quantitative assessment of alterations in regional left ventricular contractility with color-coded tissue Doppler echocardiography. Comparison with sonomicrometry and pressure-volume relations.

Background: Tissue Doppler imaging (TDI) is a novel method of color-coding myocardial velocity on-line. The objective of the present study was to evaluate endocardial velocity with TDI as a method of objectively quantifying alterations in regional contractility over a wide range induced by inotropic modulation.

Methods And Results: Myocardial length crystals were used to simultaneously assess regional left ventricular (LV) function, and high-fidelity pressure and conductance catheters were used to assess global LV contractility by pressure-volume relations in nine open-chest dogs.

Release of lactate by the lung in acute lung injury.

Unlabelled: The pathogenesis of hyperlactatemia during sepsis is poorly understood. We have previously described an increase in lactate concentration across the lung in the dog during early endotoxemia. Accordingly, we sought to determine if the lung releases lactate in humans and what relation this has with lung injury.

Tracheal gas insufflation improves ventilatory efficiency during metacholine-induced bronchospasm.

Introduction: Barotrauma and cardiovascular insufficiency are frequently encountered problems in patients with acute bronchospastic disease who require mechanical ventilation. Permissive hypercapnia is a recognized strategy for minimizing these adverse effects; however, it has potential risks. Tracheal gas insufflation (TGI) has been shown to increase carbon dioxide elimination efficiency and thus could permit mechanical ventilation at lower peak airway pressures without inducing hypercapnia.

Splanchnic buffering of metabolic acid during early endotoxemia.

Purpose: We sought to determine the sites of metabolic acid production and clearance during acute endotoxemia.

Materials And Methods: In 10 pentobarbital-anesthetized dogs, flow was measured (ultrasonic probes) for the protal vein, hepatic artery, and renal artery. Catheters were inserted into the hepatic vein, pulmonary artery, renal vein and portal vein.

Left ventricular performance assessed by echocardiographic automated border detection and arterial pressure.

Automated echocardiographic measures of left ventricular (LV) cavity area are closely correlated with changes in volume and can be coupled with LV pressure (PLV) to construct pressure-area loops in real time. The objective was to rapidly estimate LV contractility from end-systolic relationships of cavity area (as a surrogate for LV volume) and central arterial pressure (Pa) (as a surrogate for PLV) in a canine model using automated algorithms. In eight anesthetized mongrel dogs, we simultaneously measured PLV, LV area, and Pa (fluid-filled catheter).

Tracheal gas insufflation during pressure-control ventilation: effect of using a pressure relief valve.

Objectives: Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway pressure, but a consequence of this pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with pressure-control ventilation to augment CO2 elimination. During pressure-control ventilation with continuous TGI, we observed that peak airway pressure increased above the set inspiratory pressure.

The effect of managed care on ICU length of stay: implications for medicare.

Objective: To determine whether insurance status (managed care vs traditional commercial and Medicare) influences resource consumption (as measured by length of stay [LOS]) in the intensive care unit (ICU).

Design: Retrospective analysis of the 1992 Massachusetts state hospital discharge database, using prospectively developed and validated risk-stratification models.

Setting: All nonfederal hospitals in Massachusetts.

Transvisceral lactate fluxes during early endotoxemia.

The pathogenesis of hyperlacticemia during sepsis is poorly understood. We investigated the role of lung, kidney, gut, liver, and muscle in endogenous lactate uptake and release during early endotoxemia in an intact, pentobarbital-anesthetized dog model (n = 14). Ultrasonic flow probes were placed around the portal vein and hepatic, renal, and femoral arteries.

Organ-specific therapy in critical illness: interfacing molecular mechanisms with physiological interventions.

Sepsis and SIRS is the outward manifestation of a generalized uncontrolled inflammatory response, which, if sustained, induces widespread endothelial damage and MODS. Immunomodulating therapies, at present, have proven ineffective in reducing morbidity and mortality, presumably because of the heterogeneous nature of sepsis and septic shock and the reciprocating and redundant nature of this inflammatory cascade. Organ-specific therapies can support life but impair both organ-specific function and remote organ function.

Dynamic right and left ventricular interactions in the rabbit: simultaneous measurement of ventricular pressure-volume loops.

Purpose: This study was performed to characterize the dynamic factors determining ventricular interdependence in an open-pericardium intact animal model.

Materials And Methods: Simultaneous measures of right ventricular (RV) and left ventricular (LV) pressures and volumes in 6 urethane-anesthetized open-chested, open-pericardium rabbits. RV and LV V were calculated every 2 milliseconds.

Blood lactate levels are better prognostic indicators than TNF and IL-6 levels in patients with septic shock.

Objective: Both serum levels of tumor necrosis factor-alpha (TNF alpha) and interleukin-6 (IL-6) and blood lactate levels in patients with septic shock have been shown to correlate with prognosis. The aim of the study was to define the relative predictive value of these measures.

Patients: 38 hospitalized patients with septic shock, including 18 survivors and 20 non-survivors.

Left ventricular pressure-volume relations with transesophageal echocardiographic automated border detection: comparison with conductance-catheter technique.

Pressure-volume relations are important means used to assess left ventricular (LV) contractility; however, on-line volume acquisition has been limited to the invasive conductance catheter. The objective was to compare simultaneous measures of LV volume by transesophageal echocardiographic automated border detection (ABD) and conductance catheter and their respective pressure-volume relations during steady state and alterations in preload and contractility. Seven dogs had placement of high-fidelity pressure and conductance catheters, a vena caval balloon occluder, and a transesophageal probe.

Increases in peripheral oxygen demand affect blood flow distribution in hemorrhaged dogs.

Blood flow redistribution away from the gastrointestinal tract and kidney occurs during progressive hemorrhage and stress. However, the effects of remote increases in oxygen demand on a circulation with limited ability to respond have not been described. Thus, we observed the effect of remote increases in oxygen demand on splanchnic and renal blood flow in hemorrhaged dogs.