A change of heart: cardiovascular development in the shrimp Metapenaeus ensis.

The larval development of penaeid shrimp is among the most complicated in crustaceans. In Metapenaeus ensis, there are six naupliar, three protozoeal and three mysid larval instars, followed by postlarval development. Irregular heartbeat begins late in naupliar instar 6. Co-ordinated beating at 400-600 beats min(-1) commences in the first protozoeal instar and continues throughout larval life. Initially, the contractile region is located more posteriorly in the cephalothorax and has a single pair of ostia, and the arterial distribution is limited to a single anterior vessel. In later mysid instars, a second cardiac pumping site develops posterior to, but connected with, the original site. This extension is more muscular, contains additional ostia and develops additional distribution vessels supplying the cephalothorax and abdominal areas. The original site is gradually merged into the new extension and only small refinements in the circulation occur in postlarval and juvenile life. Changes in physiological responses of the heart also occur throughout development. Responses to intra-pericardial microinjection of 5-hydroxytryptamine change drastically during development, as do cardiac responses to ambient hypoxia. Similarly, heartbeat of later juvenile instars is inhibited by injection of tetrodotoxin, while heartbeat of larval and early juvenile instars is not, suggesting that neurogenic regulation via the cardiac ganglion arises later in development. Our present studies attempt to integrate the anatomical and physiological changes in the development of the crustacean heart.

Effect of graft material on loss of erythrocytes after aortic operations.

It has been suggested that loss of erythrocytes after abdominal aortic grafting is influenced by the type of synthetic graft used. A prospective randomized study was done to compare loss of erythrocytes in patients receiving Dacron (polyester fiber, Meadox woven double velour) and Gore-Tex (polytetrafluoroethylene [PTFE]) grafts during the perioperative period. A total of 25 patients (13 Dacron and 12 PTFE) was studied, including 21 with abdominal aortic aneurysms and four with aortoiliac occlusive disease. Erythrocyte volume (EV) was measured using 51Cr-labeled autologous erythrocytes on the day prior to the operation, one to two hours after the operation when the patients were hemodynamically stable and 24 hours postoperatively. In addition to measurements of 51Cr EV and the volume of intraoperatively salvaged washed erythrocytes, the length of storage of the units of homologous liquid preserved erythrocytes at 4 degrees C. prior to transfusion were recorded. The mean intraoperative erythrocyte loss (+/- S.D.) for the Dacron group was 892 +/- 543 milliliters and for the PTFE group, 842 +/- 403 milliliters (p = NS). Patients in the Dacron group received intraoperatively 2.2 +/- 1.6 (units +/- S.D.) milliliters with a range of zero to 4 units of homologous liquid preserved erythrocytes and patients in the PTFE group received 1.2 +/- 1.2 milliliters with a range of zero to 3 units of homologous liquid preserved erythrocytes (p = NS). The mean total loss of erythrocytes (+/- S.D.) was 1,055 +/- 649 milliliters for the Dacron group and 978 +/- 503 milliliters for the PTFE group (p = NS). Despite inherent differences in graft material, there were no significant differences in intraoperative or post-operative loss of erythrocytes or in the number of homologous units of liquid preserved erythrocytes transfused with a p value of less than 0.05 considered significant.

Symptomatology and anatomic patterns of peripheral vascular disease: differing impact of smoking and diabetes.

We retrospectively examined the impact of smoking and diabetes on the clinical presentation and arteriographic pattern of occlusion in 227 patients evaluated for symptomatic infrainguinal arterial disease. The age at which significant symptomatology developed did not differ for diabetics and nondiabetics. Diabetics had significantly more occlusion in the large arteries of the calf, however, particularly in the peroneal and posterior tibial arteries. Despite this, the extent of occlusive disease in the pedal arch was not influenced by diabetes. Diabetics also tended to present more frequently with gangrene or ulcer (greater than 70%) when compared to nondiabetic smokers (41%, p less than .01). Smokers presented with symptomatic disease earlier than nonsmokers (p less than .0005). Intermittent claudication was strongly associated with smoking; among 33 patients with claudication, 32 were smokers. In contrast to the effect of diabetes, smokers appeared to have less extensive occlusive disease in the large arteries of the calf than nonsmokers. Nondiabetic nonsmokers constituted less than 10% of our study population and presented at a significantly older age. Nevertheless, despite the absence of either risk factor, this group also tended to present with gangrene or ulcer relatively frequently (71%). Although diabetes and smoking are both risk factors for atherosclerotic disease, we conclude that their impact on the angiographic pattern of occlusion and clinical presentation differs substantially.

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.

A comprehensive approach to extremity vascular trauma.

A review of our experience with 368 patients with 382 extremity injuries has resulted in a treatment plan resulting in improved patient care and limb survival. A thorough examination of the injured extremity will help diagnose a significant vascular injury in the presence of certain clinical findings, eg, bruit or thrill (100%), signs of acute ischemia (100%), absent pulse (91%), shock (89%), neurologic deficit (78%), and hematoma (55%). Arteriography in proximity injuries has resulted in an abnormal finding in 16% of cases. A total of 165 vascular injuries, including 112 arterial and 53 venous injuries, were repaired using a variety of techniques. In 136 patients undergoing operative intervention, there was no operative mortality and a 1.5% amputation rate.

Therapeutic and clinical course of deep vein thrombosis.

We have reviewed our experience with the treatment of 250 patients with deep vein thrombosis diagnosed by contrast venography. The level of thrombosis was recorded according to the anatomic level to which it extended. A third of the patients had cancer, and the most common clinical findings were swelling and pain. The risk of the development of pulmonary embolism, based on the anatomic level of initial deep vein thrombosis, revealed the following: 12 of 115 patients (10 percent) with level I (calf) deep vein thrombosis developed pulmonary embolism, as did 2 of 27 patients (7 percent) with level II (popliteal) disease, 5 of 60 (8 percent) with level III (thigh) disease, 1 of 19 patients (5 percent) with level IV (groin) disease, and 2 of 26 patients (8 percent) with level V (iliac) disease. Based on our favorable experience with heparin we believe that heparin is the treatment of choice for deep vein thrombosis regardless of the anatomic level. The incidence of pulmonary embolism does not appear to be influenced significantly by the level of the deep vein thrombosis.

Evaluation and management of vascular injuries of the extremities.

We reviewed our experience with 315 extremity injuries in 306 patients for the possibility of accurately evaluating the presence of a potential vascular injury. Indications for surgical exploration based on the clinical finding of a bruit and/or thrill, ischemia, absent, pulse, shock, hemorrhage, neurologic deficit, hematoma, and proximity resulted in a rate of positive surgical exploration results of between 20% and 100%. Angiography was performed in 65 patients; 24 angiograms showed vascular injury and 41 did not. Angiography for proximity alone revealed 12% abnormal finding. Operative morbidity in the surgically explored group was 2%. We developed an algorithm for the treatment of these patients.

Management of vascular injuries to the leg.

Our experience with 69 vascular injuries in 56 patients led us to modify the management of vascular injuries to the leg. We believe that prompt and complete angiography whenever the general condition of the patient allows it, early fasciotomy when indicated before vascular repair, thrombectomy of the injured artery and vein and local instillation of heparinized saline solution, vascular repair before orthopedic stabilization of fractures in selected cases, external fixation of the fracture when there is significant soft tissue injury, and early skin grafting resulted in an improved level of care with a low morbidity and no mortality in our series.

Technical modifications in the placement of inferior vena caval filter devices.

Placement of 151 Mobin-Uddin vena caval umbrella filters and 17 Kimray-Greenfield vena caval filters since 1972 led us to make a number of technical modifications. The operative procedure is performed with local anesthesia in the vascular radiology suite. If the right internal jugular vein is narrowed and cannot be dilated, an approach through the left internal jugular vein is possible. The filters are advanced under fluoroscopic control after direct visualization of both renal veins. Since the patient is awake, he can be asked to roll on the left side if there is a tendency for the filter to advance into the hepatic veins or the right renal vein. Release of the filter is most accurately accomplished by withdrawing the carrier rather than advancing the filter. The carrier is then removed under fluoroscopic control and the internal jugular vein ligated. These modifications have resulted in a success rate of nearly 100 percent in recent filter placements, an operative morbidity of 8.3 percent and a 30 day hospital mortality of 8.9 percent.