Assessment of occlusion of the vascular access in patients on chronic hemodialysis: comparison of physical examination with continuous-wave Doppler ultrasound. STOP Investigators. Shunt Thrombotic Occlusion Prevention with Picotamide.

BACKGROUND: Dialysis access occlusion is the most common cause of hospitalization and a frequent indirect cause of mortality in patients on chronic hemodialysis. The clinical assessment of an arteriovenous shunt is presently the most widely adopted method for the diagnosis of vascular access occlusion in hemodialysis patients, but no studies have yet investigated objectively its sensitivity and positive predictive value (PPV). Continuous-wave (CW) Doppler ultrasound is a simple, inexpensive, and noninvasive technique for the assessment of arterial blood flow. We have carried out a prospective evaluation of the PPV of CW Doppler for the diagnosis of vascular access occlusion in hemodialysis patients and compared it with clinical investigation. METHODS: Fourty-one hemodialysis patients with clinical diagnosis of occlusion of their fistula were studied, and in 23 of them the diagnosis of occlusion was objectively validated. RESULTS: CW Doppler in the patients in whom occlusion was objectively validated showed PPV of 86 and 83% under basal conditions and after fistula compression, respectively, with sensitivities of 95 and 100%, respectively. Clinical diagnosis, under the same conditions, showed a PPV of 83% and a sensitivity of 100%. CONCLUSIONS: CW Doppler and clinical examination have a similar high sensitivity for the diagnosis of occlusion of the dialysis access; thus, there is no need to use routinely Doppler CW examination, unless objective documentation is required.

Altered platelet function associated with the bronchial hyperresponsiveness accompanying nocturnal asthma.

BACKGROUND: Nocturnal awakening is a common feature of bronchial asthma, and yet the mechanisms underlying this phenomenon are poorly understood. We investigated whether nocturnal awakening is associated with changes in platelet function with the use of a variety of markers of platelet activation. METHODS: Ten patients with a history of nocturnal asthma and 10 age- and sex-matched healthy control subjects were studied at 10:00 PM, 4:00 AM, and 10:00 AM on 2 consecutive days. The following parameters were tested: forced expiratory volume in 1 second (FEV1), log dose of methacholine inducing a 20% fall in FEV1, platelet count and volume, platelet aggregation induced by collagen or activating factor, and plasma and intraplatelet levels of beta-thromboglobulin and platelet factor 4. RESULTS: We have demonstrated that altered platelet function and platelet activation occurs at 4:00 AM in patients with nocturnal asthma and is associated with the maximum increases in bronchial reactivity. Such changes were not observed in 10 control subjects. Platelet dysfunction has been detected as a reduced aggregatory response of platelets to collagen and platelet activating factor such that up to 5 times more platelet activating factor and 1.5 times more collagen were required to elicit a threshold aggregatory response in asthmatic subjects when compared with control subjects; this difference was evident at all time points tested. Furthermore, at 4:00 AM there were significantly lower levels of intraplatelet beta-thromboglobulin corresponding to the maximum reduction in peak expiratory flow and to the maximal increase in bronchial responses to inhaled methacholine. CONCLUSIONS: These results suggest that platelet activation accompanies nocturnal asthma and further suggest that platelets may play a role in this common clinical condition.

Evidence for a storage pool defect in platelets from cirrhotic patients with defective aggregation.

The mechanisms underlying the defective platelet function in cirrhotic patients were investigated. Eleven cirrhotic patients with mild disease (group 1), 20 patients with severe cirrhosis (group 2), and 31 controls were studied. Platelet aggregation was significantly reduced in cirrhotics compared with controls. Compared with controls, cirrhotic patients in group 2 showed a significant reduction in the total content of adenosine triphosphate (57.8 +/- 7.8 vs. 26.1 +/- 6.3 mumol/10(11) platelets; P less than 0.05), 5-hydroxytryptamine (285 +/- 26 vs. 104 +/- 38 nmol/10(11) platelets; P less than 0.05), beta-thromboglobulin (2129 +/- 120 vs. 1223 +/- 161 ng/10(8) platelets; P less than 0.01), and platelet factor 4 (1389 +/- 108 vs. 805 +/- 176 ng/10(8) platelets; P less than 0.05). In patients with severe disease, an increase in plasma beta-thromboglobulin-platelet factor 4 ratio, an index of in vivo platelet activation, was observed (controls, 3.50 +/- 0.50; group 1, 4.02 +/- 0.80; and group 2, 6.59 +/- 1.15). Our data indicate the existence of a platelet storage pool defect, which may favor the bleeding tendency of cirrhotic patients.