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Biomedical subjects

R Berguer

Publications and source records attributed to R Berguer.

At least 19 recordsLinked to original sources
PubMed1992

Selective deep hypothermia of the spinal cord prevents paraplegia after aortic cross-clamping in the dog model.

We tested, in the dog, the hypothesis that selective deep hypothermia (19 degrees to 12 degrees C) of the spinal cord protects it from the ischemia that follows double aortic cross-clamping. The extracorporal perfusion system consisted of heat exchanger and a pump, infusing saline solution at 5 degrees C into the subarachnoid space (L-6) and draining it through the cisterna magna. After 30 minutes this system cools a normally perfused spinal cord to a stable temperature gradient of 13 degrees C (inflow) to 18 degrees C (outflow). Proximal and distal intrathecal, proximal and distal aortic, and central venous pressures were continuously recorded. Rectal temperature was maintained between 36.5 degrees C and 38.5 degrees C. Eight control dogs had cross-clamping of the aorta below the left subclavian artery and above the diaphragm without cord hypothermia. Nine experimental dogs had cord hypothermia initiated 50 minutes before systemic heparinization (100 U/kg) and double cross-clamping of the aorta. Cross-clamping was maintained for 45 minutes. The aorta was then unclamped, heparin was reversed, cord cooling was discontinued, and the dura was closed. Hindlimb function of animals was graded by use of Tarlov's scale at recovery and 24 hours later. The dogs were then killed, and the cords were removed and fixed for microscopy. All control animals were paraplegic and had histologic confirmation of spinal cord infarction. All experimental animals had intact hindlimb function and normal appearing cords on histologic examination. A two-tailed Fisher's exact test (chi square) shows this difference to be significant to p = 0.00004. In the dog selective deep hypothermia of the cord avoids the ischemic injury induced by aortic cross-clamping that results in paraplegia. The implications of these findings in thoracoabdominal aortic clamping in humans is discussed.

Animals↗
PubMed1991

Minimal access surgery for gastroesophageal reflux: laparoscopic placement of the Angelchik prosthesis in pigs.

Conventional surgery for gastroesophageal reflux is effective but requires laparotomy. Minimal access surgery for gastroesophageal reflux could provide a decrease in morbidity. The Angelchik antireflux prosthesis is an alternative to fundoplication for the treatment of this ailment. We evaluated the results of laparoscopic placement of the Angelchik prosthesis in 10 pigs. The duration of the procedure averaged 44 min. The mean lower esophageal sphincter pressure increased from 12.2 +/- 2.8 mmHg at baseline to 45.2 +/- 7.8 (P less than 0.05), 32.1 +/- 3.9 (P less than 0.05), and 25.1 +/- 6.5 mmHg (P greater than 0.05) as measured immediately postoperatively, at 1 week, and at 3 weeks, respectively, following placement of the prosthesis. There was no instance of prosthetic migration or esophageal perforation. One postoperative death due to distention and perforation of the colon occurred. Two animals developed distal esophageal impaction of food. We conclude that the antireflux prosthesis can be safely and effectively placed using laparoscopic methods in a porcine model. Further development of this technique is warranted.

Animals↗
PubMed1991

Beneficial effects of isovolemic hemodilution using a perfluorocarbon emulsion in a stroke model.

In a clinically applicable cat stroke model, 16 purpose-bred adult animals were used to evaluate the beneficial effects of two treatment regimens: isovolemic hemodilution with either a perfluorocarbon emulsion or dextran 40 (a glucose polymer). Animals that received these treatment regimens were then compared with a control group of untreated animals. Focal cerebral infarctions were produced by transorbital ligation of the left middle cerebral artery. The randomly allocated treatment arms of the study were instituted 3 hours after ligation of the middle cerebral artery, thereby simulating a human clinical situation. In vivo mitochondrial metabolic activity of the peri-infarct cerebral tissue was continually assessed by means of a multiwavelength near-infrared spectrophotometer. This allowed measurement of cellular oxygenation at the cytochrome aa3 level, the terminal member of the cytochrome chain. Sequential proton-based magnetic resonance imaging was used to measure intracerebral water in vivo. Cardiac output, oxygen consumption/delivery, chemical, histologic, and rheologic parameters were also assessed. The data collected were analyzed by group means and standard statistical analyses, which revealed that the group treated with the perfluorocarbon emulsion had both less brain edema in the early post-infarct period (p less than 0.05), as well as a higher level of oxidation of cytochrome aa3 (p less than or equal to 0.025). This evidence supports the premise that isovolemic hemodilution with an oxygen-carrying hemodiluent may be beneficial in the treatment of ischemic strokes.

Animals↗
PubMed1990

MRI quantitation of edema in focal cerebral ischemia in cats: correlation with cytochrome aa3 oxidation state.

1H MRI permits detection of edema in the brain. In a middle cerebral artery stroke model in the cat, we found a significant correlation between an edema index based on MRI and a sensitive metabolic index of ischemia, the in vivo oxidation status of mitochondrial cytochrome aa3 determined by near-infrared reflectance spectrophotometry (r = -0.70, alpha = 0.001). This result suggests that a simple, noninvasive study using MRI can provide an index of the extent of ischemic damage in an experimental acute stroke model.

Animals↗
PubMed1988

Determinants of porphyrin fluorescence emission spectra of atheromatous plaques.

Plaques were obtained via carotid endarterectomy and exposed to the fluorescent dye hematoporphyrin in vitro. Fluorescence emission spectra were used to characterize sites of dye binding. To provide additional information on the role of environment on fluorescence, model systems were studied involving micellar and premicellar systems. The data indicate two distinct fluorescence signals from plaque-bound porphyrin. These signals were at least 50-fold greater than the fluorescence from uninvolved regions of the vessel wall. Fluorescence emission at 618 nm was observed in all plaques examined. A second fluorescence signal at longer wavelengths was associated with the more complex plaques and could be mimicked by mixtures of porphyrin and detergent at a premicellar concentration. These studies suggest the presence of 2 different porphyrin-binding regions in the plaques examined. The first appears to be a predominantly aqueous site which may represent the interior of a cholesterol-rich micellar structure. The second is associated with 'hard' plaque, i.e., collagen and calcification.

Arteriosclerosis↗
PubMed1986

The short retropharyngeal route for arterial bypass across the neck.

Occasionally, in order to revascularize the carotid bifurcation one may need to cross the neck with a bypass that originates in the opposite subclavian or common carotid artery. This report describes a short, natural route behind the pharynx that permits using a shorter bypass as well as a direct reimplantation of one common carotid into its opposite without an intervening graft.

Arterial Occlusive Diseases↗
PubMed1986

The silent brain infarct in carotid surgery.

The destructive potential of carotid artery disease is underestimated by the clinical classification that surveys only that part of the brain with clear somatic representation. Asymptomatic patients are found to have brain infarctions on CT scan for which there is no history or symptom. To assume "benign" behavior of a carotid lesion, a patient must be both asymptomatic and "asignomatic." Likewise, when the morbidity of carotid operations is reported, silent infarcts must somehow be taken into account. We investigated this "silent" disease in a prospective study of 100 carotid operations done on 91 patients over a 9-month period in our service. All patients had arch and four-vessel selective arteriography. Detailed neurologic examinations and CT scans were done before and after surgery. Of the 91 patients, 78 (86%) had a history of neurologic problems. Preoperative CT scans showed infarction in 21 patients, but only 57% of the infarctions correlated with symptoms and/or history. Among patients with a history of transient ischemic attack (TIA), 19% had an infarction seen on CT scan; however, among those patients who had lateralizing TIAs, the incidence of unsuspected infarction was higher (26%). Arteriography showed a lesion in all carotid systems supplying a symptomatic or infarcted hemisphere. Following 100 operations, four patients had neurologic abnormalities--two had transient hemianopsia and two had hemiparesis. CT scan showed a new infarct in all four patients as well as in eight other patients without neurologic findings; two of these silent postoperative infarctions were found in the hemisphere opposite the side of the operated carotid artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Artery Diseases↗
PubMed1985

Idiopathic ischemic syndromes of the retina and optic nerve and their carotid origin.

Most eye problems referred to vascular surgeons for workup of carotid disease are either transient (amaurosis fugax) or partial (retinal branch artery occlusion) visual loss. Patients with more severe total infarcts of the retina (central retinal artery occlusion) or of the head of the optic nerve ("ischemic optic neuropathy") are seldom suspected of carotid disease and, in the latter case, are generally labeled idiopathic. An explanation for the difference in attitude towards these conditions is suggested. A prescribed carotid etiology for these various ischemic syndromes of the eye and optic nerve was explored in a study of 20 consecutive patients who had acute ischemic eye/optic nerve problems. Special visualization of the neck, orbital, and retinal vasculature was obtained. Sixty percent had ipsilateral and 50% had contralateral carotid artery disease. The ophthalmic artery and the posterior ciliary arteries showed intrinsic lesions each in 25% of cases. Our pilot study concludes that there is strong evidence that most of these ischemic eye syndromes are related to carotid artery disease, which is found in the majority of patients. In a minority of them ischemic problems may be due to arteritis or to intrinsic disease of the ophthalmic artery. A more cohesive approach to the study and treatment of these different entities is supported by the suggestion of a common etiology for most of them. Close collaboration with ophthalmologists will be needed to improve the present management of these eye conditions.

Acute Disease↗
PubMed1978

Induced thrombosis of inoperable abdominal aortic aneurysm.

On occasions it may be vital to produce controlled thrombosis of an abdominal aortic aneurysm when resection is not possible. A successful technique was evolved to achieve this in a 57-year-old man with malignant lymphoma. The tumor was found to infiltrate massively the retroperitoneum and the wall of a large abdominal aortic aneurysm. The large aneurysm was deemed to be technically unresectable at operation. An approach was devised to thrombose the aneurysm and to proceed safely with chemotherapy of the malignant lymphoma. An axillobifemoral bypass was made with the limbs anastomosed end to end to the common femoral arteries. The external iliac vessels were exteriorized through the abdominal wall. The aneurysmal sac outflow was occluded by balloon catheters introduced through the exteriorized iliac vessels. A right transaxillary catheter was inserted and placed at the level of the renal arteries to induce and to control the progress of thrombus formation in such a way as to ensure patency of the renal vessels. Thrombin was delivered into the sac via this transaxillary catheter. A high urinary output was maintained. Serial angiograms of the clotting process were obtained. Once the sac was thrombosed, the balloon catheters were removed and a final angiogram was obtained which demonstrated the obliteration of the aneurysmal sac and the patency of the renal vessels. The patient has been fully employed for 20 months.

Aorta, Abdominal↗
PubMed1976

Subclavian artery to external carotid artery bypass graft. Improvement of cerebral blood supply.

External carotid flow may contribute a substantial amount of cerebral flow via collaterals in cases of internal carotid artery occlusion. When common and internal carotid arteries are occluded, the distal portion of the external carotid artery is kept open by collateral flow. Revascularization of the external carotid by means of a bypass graft from the subclavian artery will improve the blood flow through collateral vessels connecting the external and internal carotid territories, and thus increase the cerebral blood supply from the branches of the external carotid artery.

Aged↗
PubMed1976

Vertebral artery bypass.

The origin of the vertebral artery is a frequent site for the development of stenosing lesions. The flow deficit caused by the stenosis of one vertebral artery is normally compensated for by intracranial anastomosis between the carotid and basilar arteries or by the opposite vertebral artery. A number of patients, however, have inadequate intracranial anastomosis and hypoplasia or stenosis of the opposite vertebral artery, and symptoms of brain ischemia develop. We describe here four cases in which a new technique, a subclavian vertebral artery autogenous vein bypass graft, was used to deal with the diseased segment of the vertebral artery. Transient postoperative problems included lymphocele and Horner syndrome. All four bypasses were patent at the time of angiography one week postoperatively. All four patients were relieved of symptoms of vertebrobasilar insufficiency.

Aged↗
PubMed1975

Geometry, blood flow, and reconstruction of the deep femoral artery.

The deep femoral artery is the main source of blood supply to the leg and foot when the superficial femoral artery is occluded. In this situation, the geometry of the trunk of the deep femoral artery represents a stenosis of 50 per cent interposed between the common femoral artery and the collateral circuit of the deep femoral artery. Intimal thickening of only 0.5 and 1.0 mm increases this anatomic stenosis to 64 and 76 per cent, respectively. Beyond the trunk, the cross-sectional area of the deep femoral artery circuit increases at each arterial division. Any reconstruction of the deep femoral artery intended to increase its inflow must extend down to at least its first important bifurcation if it is to overcome this trunk "stenosis". This requirement ex plains the effectiveness of proper reconstruction of the deep femoral artery in avoiding or delaying amputation in patients with ischemic symptoms and occlusion of the superficial femoral artery who are not candidates for femoropopliteal reconstruction. In this group, the absence of plaque on the arteriogram does not contraindicate reconstruction.

Angiography↗