Hemodynamic effects of medical antishock trousers during mechanical ventilation.

PURPOSE: To compare the hemodynamic effects of medical antishock trousers (MAST) inflation in mechanically ventilated patients with normal and poor left ventricular function. METHODS: Twelve patients requiring respiratory support were divided into two groups according to baseline transesophageal echocardiography (TEE) measurements: normal left ventricular dimensions and fractional area of contraction (FAC=61 +/- 5%) (n=7) and dilated cardiomyopathy with reduced FAC (21 +/- 1%) (n=5). All patients were studied when two successive levels of load (mild load by inflation of the leg compartment of MAST at 50 cmH2O and high load by adding the abdominal compartment of MAST inflated at 30 cmH2O) were applied. Global left ventricular systolic function was assessed on the TEE transgastric short-axis view. End-systolic wall stress (ESWS) was used as an indicator of left ventricular afterload. RESULTS: Total respiratory, lung and chest wall compliances were reduced by 48%, 51% and 27% respectively at the high load level (P < 0.05). Whereas no hemodynamic changes occurred at mild load, the high load level produced an increase in left ventricular afterload as evidenced by concomitant increases in diastolic arterial blood pressure (66 +/- 6 to 79 +/- 6 mmHg, P < 0.05) and ESWS (69 +/- 12 to 74 +/- 12 Kdyn x cm(-2) x m(-2), P < 0.05). In patients with dilated cardiomyopathy, this increase in afterload impaired the left ventricular systolic function and end-systolic area increased (19.0 +/- 2.5 to 21.4 +/- 2.9 cm2 x m(-2), P < 0.05) while FAC decreased (22 +/- 2 to 16 +/- 2%, P < 0.05). Left ventricular end-diastolic area remained unchanged during the study in both groups. CONCLUSION: MAST inflation impairs respiratory mechanics and global left ventricular systolic function in cardiac patients without changes in left ventricular preload.

Does positive end-expiratory pressure ventilation improve left ventricular function? A comparative study by transesophageal echocardiography in cardiac and noncardiac patients.

STUDY OBJECTIVES: Positive end-expiratory pressure (PEEP) has been proposed to improve cardiac output in patients with left ventricular (LV) dysfunction. This study was designed to compare quantitative global and regional LV performance in response to PEEP in patients with normal and poor LV function. DESIGN: A prospective clinical trial. SETTING: Adult medical ICU in a university hospital. PATIENTS: Twelve critically ill patients requiring respiratory support and divided into two groups according to baseline transesophageal echocardiographic (TEE) measurements: normal LV dimensions and fractional area of contraction (FAC=61+/-5%) (n=7) and dilated cardiomyopathy with reduced FAC (21+/-1%) (n=5). MEASUREMENTS AND RESULTS: All patients were studied when two successive levels of PEEP (best PEEP as the highest value of respiratory compliance and high PEEP as best PEEP+10 cm H2O) were applied. Global systolic LV performance and quantitative regional wall motion analysis performed by the centerline method were assessed on the TEE transgastric short-axis view. End-systolic wall stress (ESWS) was used as a reliable indication of LV afterload. PEEP reduced LV dimensions asymmetrically in both groups of patients and septolateral diameter significantly decreased without affecting global LV systolic performance. Additionally, high PEEP produced a significant impairment in septal kinetics as evidenced by the centerline method. High PEEP also decreased ESWS for all patients (-27% in normal group and -23% in cardiac group, p<0.05) without significant improvement in global systolic LV performance (FAC: +2% in normal group and +0% in cardiac group; not significant). CONCLUSIONS: PEEP cannot be recommended routinely to improve LV performance in patients with severe dilated cardiomyopathy.

Noninvasive monitoring of cardiac output in critically ill patients using transesophageal Doppler.

Measurement of cardiac output using thermodilution technique in mechanically ventilated patients is associated with significant morbidity. The goal of the present study was to assess the validity of cardiac output measurement using transesophageal Doppler in critically ill patients. Forty-six patients from three different intensive care units underwent 136 paired cardiac output measurements using thermodilution (COTH) and transesophageal Doppler (COTED). In addition, simultaneous suprasternal Doppler and indirect calorimetry (Fick principle) were used to measure cardiac output in 26 patients from one center. A good correlation was found between COTH and COTED (r = 0.95), with a small systematic underestimation (bias = 0.24 L/min) using transesophageal Doppler. The limits of agreement between COTH and COTED were +2 L/min and -1.5 L/min. Variations in cardiac output between two consecutive measures using either transesophageal Doppler or thermodilution techniques were similar in direction and magnitude (bias = 0 L/min; limits of agreement = +/-1.7 L/min). Suprasternal Doppler and indirect calorimetry yielded similar correlations and agreements in the subset of patients in whom they were used. These results confirm that transesophageal Doppler can provide a noninvasive, clinically useful estimate of cardiac output and detect hemodynamic changes in mechanically ventilated, critically ill patients.

Mechanical and contractile properties of in situ localized mesenteric arteries in normotensive and spontaneously hypertensive rats.

An in situ model was developed for studying mechanical properties of mesenteric arteries in rats. A branch of the mesenteric artery was exposed and dissected in normotensive (WKY) and spontaneously hypertensive rats (SHR). A catheter was introduced into the larger branch of the mesenteric artery and connected to a pressure chamber. The artery was submitted to transmural pressures ranging from 0 to 200 mmHg per steps of 25 mmHg and observed using a microscope-video-camera system. The diameter-pressure relations were established under basal conditions, under contraction (phenylephrine 10(-6) M), and after abolition of the smooth muscle tone by potassium cyanide (KCN, 0.1 mg/mL). The arterial segment was then fixed (glutaraldehyde 2.5%), and the wall cross-sectional areas were measured in transverse sections. Compliances, distensibility, wall tensions, and wall stresses were calculated from diameter, pressure, and media thickness values under three conditions. Active tension and active stress were defined as differences in wall stresses and wall tensions calculated under passive and active conditions. Comparison of WKY and SHR when arteries were studied at the respective operating pressure indicates (1) thicker and stiffer mesenteric arteries in SHRs than in WKY rats, (2) similar wall stresses in mesenteric arteries from WKY and SHRs despite larger wall tensions in the hypertensive group, and (3) larger contractility to phenylephrine in SHRs than in WKY mesenteric arteries.

Incidence of tricuspid regurgitation and vena caval backward flow in mechanically ventilated patients. A color Doppler and contrast echocardiographic study.

In 40 patients requiring mechanical ventilation for an episode of respiratory failure of various causes, prevalence of tricuspid regurgitation (TR) or other cause of vena caval backward flow (VCBF) was systematically investigated using transthoracic Doppler echocardiography. Quantification of TR was obtained from planimetry of the regurgitant jet during color Doppler examination. The influence of cyclic mechanical lung inflation was examined by contrast echography of the inferior vena cava and hepatic veins. All the 40 patients studied had TR, which was mild in 21, moderate in 9 and severe in 10. Using a planimetric scale, TR was more marked during mechanical ventilation, when compared with a brief period of spontaneous breathing. Moreover, contrast echocardiography demonstrated that systolic TR reached inferior vena cava and hepatic veins in 16 cases, and also evidenced direct mechanical action of lung inflation producing a pancardiac VCBF in 15 cases. This high incidence of TR and VCBF partially may explain the relatively poor reliability of the thermodilution method for measurement of cardiac output when used in ventilated patients.

Invasive monitoring combined with two-dimensional echocardiographic study in septic shock.

OBJECTIVE: An investigation into the incidence and the clinical implication of discrepancies which may sometimes occur between invasive and non-invasive hemodynamic evaluation in septic patients. DESIGN: A prospective, consecutive comparison. SETTING: Department of Intensive Care Medicine at a University Hospital. PATIENTS: 32 patients undergoing therapy for an episode of septic shock. INTERVENTIONS: Conventional hemodynamic support (including volume expansion in all cases and inotropic support if necessary) required to obtain a stable hemodynamic status. MEASUREMENT AND RESULTS: Cardiac output (thermodilution method), cardiac pressures (right heart catheterization) and left ventricular (LV) volumes (two-dimensional echocardiography) were simultaneously recorded. A comparison was thus made between both procedures, particularly concerning preload evaluation and assessment of left ventricular systolic function. Pulmonary artery occlusion pressure measurement was evidence as an unreliable index of LV end-diastolic volume, determining preload. Assessment of LV systolic function by both methods was conflicting in 11 cases out of the 32. CONCLUSIONS: Frequent discrepancies between to invasive and non-invasive procedure were observed. The reasons for these discrepancies, including low vascular resistance, reduced LV compliance, and a possible overestimation of cardiac output by the thermodilution method, are examined in the light of data recorded. It was concluded that invasive hemodynamic evaluation by right heart catheterization in septic patients should be seriously questioned.

[Simultaneous measurement of systolic pulmonary artery pressure by catheterization and contrast enhancement doppler echocardiography]. / Mesure simultanée de la pression artérielle pulmonaire systolique par cathétérisme et échocardiographie doppler avec contraste.

The aim of this study was to assess the value of echocardiographic contrast in measuring systolic pulmonary artery pressures. Thirty-four patients with an average age of 61 +/- 15 years undergoing right heart catheterisation had a simultaneous measurement of systolic pulmonary artery pressures by catheter and colour-coded Doppler echocardiography under basal conditions and after injection of 5% dextrose agitated with 1 cm3 of air to form microcavitations. The Doppler echocardiographic measurements were performed after withdrawal of the catheter into the inferior vena cava before and after injection of contrast. Patients were divided into two groups according to the pulmonary artery pressures at catheterisation: Group I, comprising 11 patients with systolic pulmonary artery pressures of less than 35 mmHg; Group II, comprising 23 patients with systolic pulmonary artery pressures of over 35 mmHg; The injection of contrast significantly increased the number of patients in whom systolic pulmonary artery pressures could be calculated from the Doppler signal of tricuspid regurgitation (TR) in Group I (control: 18%; contrast: 100%, p < 0.01) and Group II (control: 65%; contrast: 96%, p < 0.05). There was a close correlation between the catheter and Doppler measurements of the trans-tricuspid valve pressure gradients before and after injection of contrast in Group I (n = 11, r = 0.85, p = 0.001, with an estimated standard error (ESE) = 3.8 mmHg) and in Group II (control: n = 15, r = 0.89, p = 0.001, ESE = 10.5 mmHg, and after contrast: n = 22, .r = 0.90, p = 0.001, ESE = 7.95 mmHg) with the catheter in the right ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

[Left ventricular dysfunction while weaning from mechanical ventilation. Contribution of enoximone]. / Dysfonction ventriculaire gauche au cours du sevrage de la ventilation mécanique. Apport de l'énoximone.

Mechanical ventilation is a valuable therapeutic option in left ventricular failure because of its effect on ventricular load. However, weaning cardiac patients form mechanical ventilation may result in severe pulmonary oedema, especially if it is not properly prepared. Some of the factors which contribute to pulmonary oedema are: 1) increased venous return due to the inversion ot the regime of inthrathoracic pressures and the release of catecholamines commonly observed during weaning, 2) reduction of left ventricular compliance due to myocardial ischemia, compression of the cardiac chambers by the lungs, ventricular interdependence in some cases and left ventricular dilatation in others, 3) increased left ventricular afterload due to negative intrathoracic pressures and increased systolic blood pressure. Of all the causes of unsuccessful weaning, left ventricular dysfunction should be carefully considered because its treatment alone may enable the patients to be taken off the ventilator. The authors report six cases of pulmonary oedema in coronary patients after discontinuing mechanical ventilation. The administration I.V. enoximone, a phosphodiesterase inhibitor, prevented acute left ventricular dysfunction in 5 of the 6 cases and enabled successful and definitive weaning from mechanical ventilation.

Severe hypokalaemic paralysis from an unusual cause mimicking the Guillain-Barré syndrome.

We report a case of hypokalaemic quadriparesis occurring 37 years after a bilateral ureterosigmoidostomy. The history and physical signs as well as cerebrospinal fluid analysis initially led to a diagnosis of Guillain-Barré syndrome. Acidosis and profound hypokalaemia were present and a dramatic improvement occurred after rapid correction of the potassium depletion. The underlying mechanism of potassium depletion which occurs after this mode of urinary diversion are briefly discussed.

[Radiation-related atrioventricular block]. / Bloc auriculoventriculaire radique.

Twelve years after mediastinal irradiation for Hodgkin's disease, a 38-years old man developed an infra-hisian atrioventricular block with syncopes. The rarity of this complication of radiotherapy is emphasized. A review of the literature yielded only 6 cases of atrioventricular block associated with cobalt therapy; a pathological examination was performed in two of these patients and an electrophysiological study in two others.