Heparin-induced platelet aggregation in anorexia nervosa and in severe peripheral vascular disease

Abstract. We have previously demonstrated that platelets obtained from patients with anorexia nervosa or severe peripheral vascular disease are hyperaggregable. Since conventional heparins are known to activate platelets in vitro and occasionally induce thrombosis and consumptive thrombocytopenia in vivo , we have investigated the direct effect of a conventional heparin on platelets obtained from patients with anorexia nervosa or severe peripheral vascular disease. Heparin at therapeutic concentrations was found to induce platelet aggregation of such platelets in vitro. In contrast, a recently developed low molecular weight heparinoid (Org 10172), at therapeutic concentrations, had no effect on these hyperaggregable platelets. We conclude that: (i) heparin may be potentially harmful to patients with hyperaggregable platelets; (ii) thrombocytopenia and thrombosis associated with heparin therapy may be mediated through a direct effect of heparin on platelets; (iii) it is unlikely that heparin induced thrombocytopenia is always mediated by classical immunological mechanisms, especially in patients with hyperaggregable platelets; and (iv) low molecular weight heparinoids may be safer anticoagulants in patients with platelet hyperaggregability.     

术中超声在脑血管疾病的应用

目的 采用术中超声观察不同颅内血管性病变的显示情况,探讨术中超声实时定位病灶、指导手术切除的价值.方法 对204例颅内血管性疾病患者行术中超声检查,对动静脉畸形患者寻找供血动脉和引流静脉.对海绵状血管瘤患者剪开硬脑膜切除病变前(术前)、经大脑皮层造瘘到达病灶时(术中)以及病灶切除术后(术后)均行术中导航及术中超声检查,并比较二者定位的准确性.结果 ①术中超声对颅内血管性疾病的显示率为98%,其中对颅内动静脉畸形和海绵状血管瘤的显示率均为100%,动脉瘤的显示率为81%,血管母细胞瘤的显示率为91%.②术中超声对颅内动静脉畸形患者供血动脉及引流静脉的显示率为71%.③术中超声与术中导航在海绵状血管瘤切除术前定位的准确率差异无统计学意义(100%对95%,P=0.244).术中超声在海绵状血管瘤切除术中、术后定位的准确率明显高于术中导航,差异有统计学意义(100%对74%,x2=19.513,P＜0.0001,100%对68%,x2=24.973,P＜0.0001).结论 术中超声对颅内血管性疾病具有较高的显示率,并可准确定位病变,指导手术,缩短手术时间,减少损伤,提高手术的精确性.     

Effect of burst-mode transcutaneous electrical nerve stimulation on peripheral vascular resistance

BACKGROUND AND PURPOSE: Based on changes in skin temperature alone, some authors have proposed that postganglionic sympathetic vasoconstrictor fibers can be stimulated transcutaneously. Our goal was to determine the effects of low-frequency (2 bursts per second), burst-mode transcutaneous electrical nerve stimulation (TENS) on calf vascular resistance, a more direct marker of sympathetic vasoconstrictor outflow than skin temperature, in subjects with no known pathology. SUBJECTS: Fourteen women and 6 men (mean age=31 years, SD=13, range=18-58) participated in this study. METHODS: Calf blood flow, arterial pressure, and skin temperature were measured while TENS was applied over the common peroneal and tibial nerves. RESULTS: Blood flow immediately following stimulation was not affected by TENS applied just under or just above the threshold for muscle contraction. Transcutaneous electrical nerve stimulation applied at 25% above the motor threshold caused a transient increase in calf blood flow. Regardless of stimulation intensity, TENS had no effect on arterial pressure; therefore, calf vascular resistance decreased only during the trial that was 25% above the motor threshold. Regardless of stimulation intensity, TENS failed to alter dorsal or plantar skin temperature. DISCUSSION AND CONCLUSION: These results demonstrate that the effects of TENS on circulation depend on stimulation intensity. When the intensity was sufficient to cause a moderate muscle contraction, a transient, local increase in blood flow occurred. Cooling of the dorsal and plantar skin occurred in both the stimulated and control legs, most likely because skin temperature acclimatized to ambient room temperature, rather than because of any effect of TENS on circulation. The data, therefore, call into question the idea that postganglionic sympathetic efferent fibers are stimulated when TENS is applied at clinically relevant intensities to people without symptoms of cardiovascular or neuromuscular pathology.     

Laser angioplasty in peripheral vascular disease

The use of laser energy to recanalize peripheral arterial vessels is a new and challenging alternative to more extensive surgical intervention. This exciting technique allows the critical care nurse to respond creatively to changing protocols and patient situations, establishing standards of nursing care for this patient population.     

Ethnic differences in peripheral vascular disease

The wide variation in the way coronary artery disease (CAD) affects different ethnic groups and the associated risk factor profiles of these groups have been extensively studied, but ethnic differences in the clinical manifestations of peripheral vascular disease (PVD) have been relatively neglected. The aim of the present review is to provide an overview of PVD in different ethnic groups and to explore possible pathophysiological factors accounting for these differences. Atherosclerotic PVD is generally less prevalent in Indo-Asians and Afro-Caribbeans than in caucasians, despite the 'classical' risk factors being as prevalent, if not more so, suggesting the possibility of as yet unidentified risk factors in these groups. Angiographic and microscopic evidence suggests that patients of African or Afro-Caribbean origin suffer from a different pattern of PVD, which primarily affects the distal arteries. In contrast, Indo-Asians tend to suffer from thromboangiitis obliterans (Buerger's disease) far more frequently than other ethnic groups; thus, their arterial disease appears to present much earlier and with greater severity. However, if this sub-category of patient is excluded, they seem to suffer much less from 'simple' atherosclerotic disease than their caucasian counterparts. Despite a higher prevalence of diabetes among Indo-Asians, the prevalence of intermittent claudication is considerably less in this ethnic group.     

Treatment modalities in peripheral vascular disease

This section deals with two commonly encountered clinical problems lower extremity arterial occlusive disease and venous dysfunction. Medical and surgical treatment approaches are discussed, providing an overview of management options. Patients with peripheral arterial and venous disease present nursing with many challenges. Their problems are often chronic, enforcing the need for astute recognition and management as well as patient teaching.     

Study of peripheral blood circulation during continuous and pulsatile perfusion based on the data of transcutaneous pO2 and pCO2 monitoring

The study was performed on 22 patients with congenital heart valve defects after hypothermic cardiopulmonary bypass surgery. Transcutaneous and arterial pO2 and pCO2 have been measured at different stages of investigation. Nonpulsatile flow was applied to 10 patients and pulsatile flow--to 12 patients. Pulsatile pressure was maintained at about 30 mmHg. Transcutaneous index, carbon dioxide gradient and transcutaneous oxygen shunt have been calculated. Perfusion caused a decrease in transcutaneous pO2 and transcutaneous index, as well as an increase in transcutaneous O2 shunt. The use of non-pulsatile flow caused the most marked peripheral vasoconstriction. Transcutaneous index demonstrates that peripheral circulation decrease in pulsatile flow is 3 times lower than in non-pulsatile flow. Calculation of transcutaneous index and O2 shunt based on transcutaneous pO2 and pCO2 values can characterize peripheral circulation prior to, during and following perfusion.     

New drug therapy in peripheral vascular disease

New drug therapy for peripheral vascular disease includes the use of nifedipine or sympathetic blocking agents for Raynaud's phenomenon and the use of lower doses of warfarin to prevent recurrence of thromboembolic disease. In prophylaxis of deep venous thrombosis, minidose heparin with or without dihydroergotamine and pneumatic boots are effective. Exercise regimens and the cessation of smoking remain the best therapy for intermittent claudication.