Carl Roosens

The effects of load on systolic mitral annular velocity by tissue Doppler imaging

In this investigation, we sought to identify the role of gamma-aminobutyric acid (GABA)A and GABAB receptors in the feline pulmonary vascular bed. Using adult mongrel cats and in separate experiments, we investigated the effects of l-N5-(1-iminoethyl) ornithine hydrochloride (l-NIO) (a nitric oxide synthase inhibitor), glibenclamide (an adenosine triphosphate (ATP)-sensitive K+ channel blocker), meclofenamate (a nonselective cyclooxygenase inhibitor), bicuculline (a GABAA receptor antagonist), and saclofen (a GABAB receptor antagonist) on pulmonary arterial responses to pinacidil (an ATP-sensitive K3channel activator), bradykinin (a nitric oxide synthaseinducer),muscimol(a GABAA receptor agonist), and 3-aminopropyl(methyl)phosphinic acid, hydrochloride (SKF-97541; a GABAB receptor agonist). Under increased tone conditions in the isolated left lower lobe vascular bed of the cat, muscimol induced a dose-dependent vasodepressor response that was not significantly altered after the administration of l-NIO, glibenclamide, meclofenamate, and saclofen. SKF-97541-induced vasodepression was not significantly attenuated after the administration of l-NIO, meclofenamate, and bicuculline. Responses to SKF-97541 were significantly attenuated after the administration of glibenclamide and saclofen. Responses to muscimol were significantly reduced after the administration of bicuculline. The results suggest that muscimol and SKF-97541 have potent vasodepressor activity in the feline pulmonary vascular bed and that these responses are modulated by, respectively, GABAA and GABAB receptor-sensitivepathways.Further,SKF-97541-induced vasodepression is mediated or modulated by an ATP-sensitive K3channel.Tissue Doppler Imaging (TDI) provides information on systolic function through its systolic mitral annulus velocity wave (Sm), reflecting the peak velocity of shortening of the myocardial fibers oriented in the longitudinal direction. In this study, we evaluated the effect of load changes on Sm. Forty-two cardiac surgical patients with left ventricular ejection fraction >60% were consecutively evaluated. In 24 patients, load was changed with an IV bolus of phenylephrine (50-100 microg) or nitroglycerine (300-500 microg); in 18 patients, preload was changed with a rapid infusion of 500 mL of a gelatin solution. The sample volume of TDI was placed at the lateral side of the mitral annulus in the mid-esophageal 4-chamber view. Changing loading conditions with phenylephrine or nitroglycerine had no effect on Sm; the increase of preload in 18 patients resulted in a statistically significant increase of Sm (baseline, 8.4 +/- 2.6 cm/s; after increase of preload, 9.6 +/- 2.5 cm/s; P = 0.001). We conclude that Sm is dependent on changes in preload obtained by volume loading and cannot be recommended as an index of ventricular contractile performance in critically ill patients where significant changes in ventricular filling occur.

Contractility in humans after coronary artery surgery : Echocardiographic assessment with preload-adjusted maximal power

BackgroundPropofols unique pharmacokinetic profile offers advantages for titration and rapid emergence in patients after coronary artery bypass graft (CABG) surgery, but concern for negative inotropic properties potentially limits its use in these patients. The current study analyzed the effect of

The impact of the initial ventilatory strategy on survival in hematological patients with acute hypoxemic respiratory failure

PURPOSE The aim of this study was to assess the impact of the 3 types of initial respiratory support (noninvasive positive pressure ventilation vs invasive positive pressure ventilation vs supplemental oxygen only) in hematological patients with acute hypoxemic respiratory failure (ARF). MATERIALS AND METHODS This study is a retrospective analysis of a cohort of hematological patients admitted to the intensive care unit (ICU) of a tertiary care hospital between January 1, 2002, and June 30, 2006. RESULTS One hundred thirty-seven hematological patients were admitted at the ICU with ARF (defined as Pao(2)/Fio(2) <200): within the first 24 hours, 24 and 67 patients received noninvasive positive pressure ventilation and invasive positive pressure ventilation, respectively, and 46 received supplemental oxygen only. Intensive care unit mortality in the 3 patient categories was 71%, 63%, and 32%, respectively (P = .001), and in-hospital mortality was 75%, 80%, and 47%, respectively (P = .001). In multivariate regression analysis, increasing cancer-specific severity-of-illness score upon admission and more organ failure after 24 hours of ICU admission, but not the type of initial respiratory support, were significantly associated with ICU or in-hospital mortality. CONCLUSIONS Intensive care unit and in-hospital mortality in our population of hematological patients with hypoxemic ARF was determined by severity of illness and not by the type of initial respiratory support.

Management of Candidal Thrombophlebitis of the Central Veins: Case Report and Review

Candidemia and major organ candidiasis are problems that emerged in the past 2 decades and that are partially due to medical progress. Catheter-related thrombosis of the central veins is known to be a frequent but mostly subclinical complication of central venous lines. Although candidemia and catheter-related thrombosis are frequent, candida thrombophlebitis of the central veins is rarely reported. We recently successfully treated a 19-year-old polytrauma patient with candidal thrombophlebitis of the innominate vein. Despite catheter removal and therapy with amphotericin B, recurrent candidemia and signs of infection persisted, and a complete resection of the involved vein had to be performed. Only 16 well-documented cases of candidal thrombophlebitis of the central veins in adults have been reported over the past 20 years. An analysis of these 16 patients, together with our patient, is made in relation to risk factors, clinical features, diagnosis, therapy, and mortality.

Hemodynamic effects of different lung-protective ventilation strategies in closed-chest pigs with normal lungs

Objective:The benefits of lung-protective ventilation strategies used for acute respiratory distress syndrome in subjects with normal lungs are uncertain. The purpose of this study was to investigate the hemodynamic effects of conventional lung-protective ventilation (CLPV) and high-frequency oscillatory ventilation (HFOV) in a normal lung animal model. Design:Prospective laboratory investigation. Setting:Animal laboratory in a university medical center. Subjects:Seven landrace pigs (mean weight 41 kg). Interventions:Pigs were ventilated at random conventionally with positive end-expiratory pressure 2–3 cm H2O and tidal volume 10–12 mL/kg (control), with CLPV (positive end-expiratory pressure 10 cm H2O, tidal volume 6 mL/kg), or with HFOV. Hemodynamics were analyzed after insertion of biventricular conductance catheters and a pulmonary artery catheter. Measurements and Main Results:The protective strategies led to higher mean airway pressures and severe hypercapnia with acidosis, which was only significant with CLPV. Compared with control, oxygenation was worse with CLPV and HFOV. With HFOV and CLPV, mean arterial pressure, cardiac output, and stroke volume decreased significantly; pulmonary arterial elastance increased. The slope of the end-diastolic pressure volume relationship for the left and right ventricle remained unchanged (preserved ventricular function), whereas the intercept increased with both protective strategies (augmented intrathoracic pressure); left and right end-diastolic volumes decreased significantly. Conclusions:In the absence of a fluid resuscitation strategy, CLPV and HFOV caused decreased mean arterial pressure, cardiac output, and stroke volume and worsened oxygenation in this normal lung animal model. This resulted primarily from a biventricular decrease in preload.

Acute effects of upright position on gas exchange in patients with acute respiratory distress syndrome.

Patients with acute respiratory distress syndrome (ARDS) have dorsal atelectasis of the lungs. This is probably caused by several mechanisms: compression on dependent lung zones, purulent secretions in alveoli, and upward shift of the diaphragm. An upright position (UP) of the patient (the whole body in a straight line at 40 to 45 degrees) can theoretically ameliorate these mechanisms. The objective was to evaluate whether there was an improvement of gas exchange during UP of ARDS patients and to evaluate the hemodynamic effects. A prospective interventional study was performed in the surgical and medical ICUs and the burn unit of the Ghent University Hospital, a tertiary care center. Included were ARDS patients with onset of ARDS within 48 hours before start of the study. Patients were excluded when there was hemodynamic instability or when the PaO2/FiO2 ratio deteriorated during the 2 hours preceding UP. After a 2-hour observation period in a semirecumbent position, patients were put in UP for 12 hours. Respiration and hemodynamic data were recorded at the start and end of the 2-hour observation period, and after 1, 4, and 12 hours in UP. Eighteen patients were included in the study. There was a significant increase of the PaO2/FiO2 ratio during UP (P< .001). Except for the need for volume resuscitation in 5 patients (27.8%), there was no significant change in the hemodynamic profile of the patients. Upright positioning of patients with ARDS, a relatively simple maneuver, resulted in an improvement of gas exchange and was tolerated hemodynamically relatively well during a 12-hour observation period.

Estimation of myocardial performance in CABG patients

Myocardial performance index (MPI) permits a relative easy estimation of global left ventricular (LV) systolic and diastolic function. It was shown that MPI inversely correlated strongly with the maximum derivative of LV pressure with respect to time (+dP/dtmax). The current study evaluated the change of MPI during and immediately after coronary artery bypass surgery (CABG) surgery and analyzed the relationship between MPI and hydraulic energy (exemplified by preload adjusted maximal power – PAMP) during that same period. The study was conducted in 45 patients undergoing CABG. After induction of anaesthesia, 10 min after revascularization and 2 h postoperatively, haemodynamics were assessed. Preload was characterized by LV end‐diastolic area indexed for BSA (LVEDAI); afterload was estimated by arterial elastance (Ea) and indexed systemic vascular resistance (SVRI). Global myocardial performance was indicated in terms of MPI and contractility was achieved by PAMP. Myocardial performance index increased postoperatively (0.44 ± 0.13, 0.37 ± 0.17 and 0.50 ± 0.16, respectively; P < 0.001). Preload adjusted maximal power did not alter significantly (1.90 ± 1.24, 2.02 ± 1.34 and 2.12 ± 1.00 W cm−2*104, respectively). Left ventricular enddiastolic area indexed did not change. Arterial elastance augmented to 0.76  ±  0.39, 0.80 ± 0.40 and 1.01 ± 0.43 mmHg ml−1, respectively; P < 0.001. Systemic vascular resistance did not change. A relationship was found between 1‐MPI/LVEDAI2 and PAMP (R2 = 0.50).

Is tissue Doppler echocardiography the Holy Grail for the intensivist

Assessment of left ventricular diastolic function in the critically ill patient remains a difficult issue in clinical practice. Combined use of routine transmitral and pulmonary venous Doppler patterns in conjunction with tissue Doppler imaging have been claimed to allow bedside diagnosis of diastolic dysfunction. Although in the previous issue of Critical Care it was clearly demonstrated there might be a difference in load dependency of the early myocardial tissue Doppler velocity between lateral and septal placed sample volume, there remain still several unanswered questions, particularly with respect to the preload dependency of these indices.

Perioperative use of dihydropyridine calcium channel blockers

CALCIUM channel entry blockers (CCEB) are drugs extensively used in cardiology practice. CCEB include a broad spectrum of various drugs with different actions on the heart and the vessels (1). Table 1 shows a classification of the various generations of CCEB (2). Three groups of routinely used CCEB blocking the high voltage (L-type) calcium channel have been accepted: phenylalkylamines (e.g. verapamil), dihydropyridines (e.g. nifedipine, nimodipine, nicardipine, isradipine or felodipine) and benzothiazepines (e.g. diltiazem). Clevidipine is another IV 1,4dihydropyridine with ultra short activity, being rapidly hydrolysed by esterases (3, 4). In each subset of CCEB, different generations have been determined (2). The first generation comprises older drugs with a rapid onset and short duration of action, and neurohumoral activation (Table 1). All of these drugs are characterised by potent peripheral vasodilation, inducing reflex sympathetic stimulation. The second generation includes a subset with newer CCEB, e.g. nitrendipine, nisoldipine, nimodipine and others. Finally, a third generation group, contains newer, longer acting drugs (e.g. amlodipine), permitting improved and long-term control of hypertension (2). Owing to their clinical importance, only the intravenously available dihydropyridines, as a distinct class of CCEB, will be discussed in this review in relation to their pharmacokinetics and cardiovascular effects. In contrast to the other CCEB, 1,4-dihydropyridines have little effect on heart rate and conduction and are potent arteriolar vasodilators (5). In this way, it seems logical that these drugs are used in controlling blood pressure in the critical care environment

Echocardiography and assessing fluid responsiveness: acoustic quantification again into the picture?

Accurate identification of fluid responsiveness has become an important issue in critically ill patients. Pulse pressure and stroke volume variation have been shown to be reliable predictors of fluid responsiveness. Apart from these two valuable techniques, echo-Doppler offers an interesting alternative for estimating the adequacy of filling. Acoustic quantification is a high-tech tool for delineating the blood-tissue interface on-screen in real time. Cannesson and coworkers utilized this technique in ventilated patients to assess stroke area changes, with the intention being to predict fluid responsiveness.