Biomedical subjects
R C Darling
Publications and source records attributed to R C Darling.
Avoiding the hemodynamic consequences of aortic cross-clamping and unclamping.
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Splenorenal arterial anastomosis for renovascular hypertension.
In properly selected patients, the benefits of renal artery reconstruction for renovascular hypertension have been clearly established. Disagreement remains, however, regarding the optimal technique. For most types of left-sided lesions, a splenorenal arterial anastomosis offers decided advantages. Only a single suture line is required and autogenous arterial tissue is employed. Difficulties with a diseased aorta are avoided. The procedure is particularly suitable for a staged approach to bilateral disease or in reoperation for failed prior reconstructions. Our experience with this procedure in 19 patients is reviewed and indications for selection of a splenorenal anastomosis are discussed. There were no deaths, and a single failure due to graft occlusion (5%). Of the remaining 18 patients, 7 are cured and 11 are improved. There were no instances of postoperative renal failure, and renal function improved in all four patients with preoperative renal failure. We conclude that in properly selected patients this procedure is of great usefulness and deserves wider application.
Femoral artery pressure measurement during aortography.
Femoral artery pressure (FAP) measurements were carried out to evaluate the hemodynamic significance of aorto-iliac occlusive disease in 150 patients (173 limbs) at the time of transfemoral angiography. Clinical assessment based upon traditional criteria of claudication level, pulse examination, and monoplane angiography were at variance with the results of this physiologic testing in approximately one-third of the patients. Results were most variable, and FAP testing most helful in evaluating patients with moderate diffuse disease on angiography, who are usually difficult to evaluate clinically. Strong correlation existed between FAP evaluation and the results of arterial reconstructive surgery. Of the patients with a positive FAP result who underwent proximal vascular reconstruction, 96% had satisfactory relief of ischemic symptoms despite uncorrected distal disease in the majority. In contrast, 57% of the patients undergoing proximal operation despite a normal FAP result were unrelieved of symptoms and required subsequent distal procedures. Similar correlation existed with results of femoro-popliteal and femoro-femoral grafting. This simple physiologic test has been found of great value in selecting the proper level of arterial reconstruction and in accurately predicting the results of surgery.
Experience with a noninvasive evaluation for cerebral vascular disease.
This report describes a newly developed noninvasive method for extracranial cerebrovascular evaluation. Two hundred consecutive cases were studied at the Massachusetts General Hospital and matched with clinical and angiographic findings. There were three false negative and five false positive results. Two ulcerated plaques without stenosis were not detected. Management routes for different groups of patients with central nervous system symptoms are outlined. We emphasize the usefulness of monitoring postoperative ophthalmic artery pressure to aid in the early detection of carotid occlusion in patients developing neurologic symptoms following carotid endarterectomy.
Rational management of the asymptomatic carotid bruit.
A noninvasive cerebrovascular evaluation has been devised that combines three separate but complimentary procedures: ocular pneumoplethysmography (OPPG), carotid audiofrequency analysis (CAA), and cerebral Doppler analysis. This evaluation has proven particularly useful in examination of the asymptomatic carotid bruit, and the management of such patients is aided by noninvasive testing. Patients with a poorly compensated stenosis (reduced OPPG) are all considered candidates for angiography and surgery. For patients with a well-compensated (normal OPPG) but surgically important stenosis (abnormal CAA or Doppler), angiography and surgery are recommended in selected patients. Angiography and/or surgery are believed safely withheld in all remaining patients. The reliability and effectiveness of this approach is evaluated in a series of 100 consecutive patients with an asymptomatic carotid bruit. There were no false-positive results and only known false-negative interpretation.
The dead zone of thermoregulation in normal and paraplegic man.
Independent heating and cooling of the core and skin were performed to a normal and a paraplegic subject. It was found that the core threshold temperature for vasoconstriction release was between that for shivering and sweating. After the onset of sweating, vasodilation of the forearm was observed to increase sharply. The core threshold temperature of sweating of the paraplegic was 0.7 degrees C higher than that of the normal at corresponding mean sentient skin temperatures. No sweating was observed in the spinal man without raising his core temperature. It appeared that the dead zone of thermoregulation is shifted up in the spinal patient and the possible reasons for this are discussed.
Sweating response: a means of evaluating the set-point theory during exercise.
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Noninvasive evaluation of asymptomatic carotid bruits.
Proper clinical management of a patient found to have an asymptomatic carotid bruit continues to be controversial, with wide differences of opinion concerning the advisability of angiography and surgery. A noninvasive cerebrovascular evaluation is described, which combines three separate but complimentary procedures: ocular pneumoplethysmography (OPPG), carotid audiofrequency analysis (CAA), and cerebral Doppler analysis. Such studies are particularly helpful in evaluating patients with an asymptomatic carotid bruit. The reliability and effectiveness of this approach was evaluated in a series of 165 consecutive patients with an asymptomatic bruit. Angiography was recommended in patients with positive results (42%) and safely withheld in those with negative findings (58%). There were two false-positive results and only one known false-negative interpretation.
Optimal methods of aortoiliac reconstruction.
Alternate methods of aortic reconstruction for aortoiliac occlusive disease were reviewed in one author's (R.C.D.) personal series of 582 patients (1,105 limbs) during the 15 year period from 1963 to 1977. To illustrate certain trends, separate analysis was done for periods 1963 to 1969 (interval I) and 1970 to 1977 (interval II). During the earlier period, endarterectomy was performed in 72% of patients, with unilateral operations carried out in 15% of patients. Operative mortality was 5.1% and early failure occurred in 4% of patients. In contrast, in interval II graft procedures were done in 89% of patients, with mortality of only 2% and early failure in less than 1% of patients. Unilateral procedures were utilized infrequently (4%). Our analysis suggests that aortoiliac endarterectomy is still the procedure of choice for a small group (approximately 10%) with localized disease. For more extensive disease, aortofemoral grafts appear to be the procedure of choice. Patency of such grafts in the most recent interval was 91% at 5 years. Superior long-term function of aortofemoral grafts appears to be associated with use of a knitted Dacron prosthesis, end-to-end proximal anastomosis, and distal anastomosis which ensures patency of the profunda femoris outflow. The incidence of infection (0.3%) and false aneurysm formation (1.4%) was extremely low. In view of the low mortality rate and superior long-term success of direct reconstructions, extraterritorial grafts are felt to be rarely indicated.
[Autotransfusion, an old concept with new interest].
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Selection of patients with lymphedema for compression therapy.
Seventeen patients with lymphedema were treated with intermittent external pneumatic compression. Two patients with hemodynamically significant venous obstruction showed no response to therapy. The response of the remaining fifteen patients varied with the degree of subcutaneous tissue fibrosis. Xeroradiographic estimates of tissue compressibility provided valuable prognostic information. Intermittent external pneumatic compression is an effective nonsurgical method of treatment in patients selected by xeroradiography.
Hematuria as a sign of aorto-caval fistula.
An aorto-caval fistula is a rare complication of an abdominal aortic aneurysm (AAA). Typical features, including congestive heart failure and a loud abdominal bruit, may be present and allow prompt diagnosis, but not infrequently they are absent or overlooked and the diagnosis not made preoperatively. Four patients with an AAA and an aorto-caval fistula are described, each of whom presented with hematuria. We believe the presence of hematuria in a patient with a symptomatic AAA should suggest the diagnosis of an aorto-caval fistula. A correct preoperative diagnosis may contribute to better planning of the operative procedure, reduced blood loss, and avoidance of possible pulmonary embolization.
Arterial injuries associated with fractures and/or dislocations of the knee.
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Intraoperative monitoring using the pulse volume recorder.
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Autopsy study of unoperated abdominal aortic aneurysms. The case for early resection.
A review of 24,000 consecutive autopsies during a 23-year period from 1952 through 1975 at the Massachusetts General Hospital revealed 473 patients died with surgically intact arteriosclerotic abdominal aortic aneurysms (AAA). Contrary to previous studies, the incidence of rupture of AAA between 4 and 7 cm in our experience is similar and significant (25%). The location of rupture and duration of symptoms were recorded. Of the multiple-risk factors considered, only size seemed to bear on the likelihood of AAA rupture. Of 52 patients followed 3 months to 10 years before death with known AAA, the majority died of the ruptured AAA. In a surgical environment with an expected mortality of less than 2%, even small aortic aneurysms should be resected.
Assessment of abdominal aortic aneurysm size.
Because of the importance of size in the decision for elective operation in patients with abdominal aortic aneurysm (AAA) and the need to identify accurately even small aneurysms, a prospective study was carried out to compare currently available diagnostic methods. A series of 78 patients with AAA underwent evaluation by physical examination, lateral lumbar spine X-ray, aortic ultrasound, and aortography. Measurements were compared to aneurysm size at operation. Physical examination was most variable, and tended to overestimate size by approximately 20%. Lateral spine X-ray was useful in three of every four patients and in these cases it was reliable and reasonably accurate. Ultrasonography was most widely applicable and very reliable for diagnosis. Its tendency to underestimate aneurysm size in our experience may be improved by use of gray-scale units, which better define aneurysm wall thickness. The anatomic information provided by aortography was of great value in the surgical management of patients with AAA, but aortography was of limited value in accurate measurement and should not be employed for this purpose.
Failure of ultralightweight knitted Dacron grafts in arterial reconstruction.
We have observed 11 cases in which the use of the ultralightweight knitted Dacron arterial graft made by the United States Catheter and Instrument Co. (USCI) was complicated by Interstitial hemorrhage dilation, or both. Although the incidence and specific cause of failure of this graft are unknown, we have discontinued its use on the basis of this experience.