François Brenot

Increased plasma serotonin in primary pulmonary hypertension

PURPOSE Pulmonary hypertension can occur in patients who have disorders associated with altered platelet serotonin storage, including collagen vascular disease and platelet storage pool disease. We tested the hypothesis that primary pulmonary hypertension (PPH) may be also associated with impaired handling of serotonin by platelets, resulting in increased plasma serotonin levels. PATIENTS AND METHODS We used radioenzymatic assays to measure serotonin in platelets and plasma and serotonin released during in vitro platelet aggregation in 16 patients with PPH, and in 16 normal controls matched for age and sex. Six patients were restudied after heart-lung transplantation to determine whether serotonin abnormalities persisted after pulmonary arterial pressure returned to normal. RESULTS Patients had decreased platelet serotonin concentration (1.8 +/- 0.6 x 10(-18) mol/platelet versus 3.2 +/- 0.2 x 10(-18) mol/platelet in controls; P < 0.01) and increased plasma serotonin concentration (30.1 +/- 9.2 x 10(-9) mol/L versus 0.6 +/- 0.1 x 10(-9) mol/L in controls; P < 0.001). Serotonin released during in vitro platelet aggregation was higher in patients than in controls. After heart-lung transplantation, platelet serotonin concentrations remained decreased and plasma levels remained increased. CONCLUSIONS Abnormal handling of serotonin by platelets leading to an increase in plasma serotonin occurs in PPH. The persistent decrease in platelet storage of serotonin after heart-lung transplantation suggests that this platelet abnormality is not secondary to PPH.

Role of CT in chronic pulmonary embolism: comparison with pulmonary angiography.

To assess the value of CT in chronic pulmonary embolism (CPE), CT scans and pulmonary angiograms of 21 consecutive patients were reviewed. Computed tomography was better than angiography in assessing proximal clots (three thrombi not seen by angiography, three angiographic false-positives confirmed by surgery). Furthermore, CT was able to analyze pulmonary arteries distal to angiographic amputations. Computed tomography was less sensitive than angiography for vascular distortions (38 vs. 50%) and stenosis (35 vs. 71.8%). Pulmonary infarctions were better detected and characterized by CT than by angiography. Isolated parenchymal ground-glass opacities were seen by CT in 18 patients, especially in those with right cardiomegaly. High resolution CT delineated them better than did standard CT. Computed tomography may be a useful adjunct to angiography in the assessment of CPE.

Frequency of mechanical ventilation and respiratory activity after double lung transplantation

We investigated the contribution of pulmonary afferent nerve fibers to the control of inspiratory activity in awake humans. Eight double lung transplant outpatients and eight normal subjects were hyperventilated with a mechanical ventilator. Respiratory frequency was increased until no respiratory activity was detectable. Then, by either adding CO2 in the inspired gas or decreasing respiratory frequency, end-tidal PCO2 (PETCO2) was increased until inspiratory activity (i.e. change in inspiratory airway pressure peak and/or time profile) was detected. In normal subjects, PETCO2 threshold for inspiratory muscle recruitment was significantly lower when frequency was decreased than when CO2 was added (31.3 +/- 6.8 Torr vs. 38.2 +/- 8.1 Torr respectively, P < 0.005). This was not the case in the double lung transplant group (31.5 +/- 6.5 Torr vs. 32.9 +/- 5.8 Torr). These findings suggest that pulmonary afferent nerves have an inhibitory effect on inspiratory activity in humans.

Maprotiline and Pulmonary Alveolitis

Excerpt To the Editor:Maprotiline (Ludiomil, Ciba Pharmaceutical Company, Summit, New Jersey) is a new tetracyclic antidepressant agent widely used in the United States and in Europe. The allergic ...