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Biomedical subjects

R C Heros

Publications and source records attributed to R C Heros.

At least 19 recordsLinked to original sources
PubMed1992

Mechanism of cerebral blood flow augmentation by hemodilution in rabbits.

BACKGROUND AND PURPOSE: Hemodilution is known to increase cerebral blood flow, but it is not known whether the increase in flow is a direct result of a decrease in viscosity or whether it may be due to compensatory vasodilatation in response to the decrease in oxygen carrying capacity that results from hemodilution. This study is designed to investigate this question. METHODS: Changes in regional cerebral blood flow were studied in normal and ischemic brains of 15 and 18 rabbits, respectively. In one group of rabbits graded hemodilution was used to reduce arterial oxygen content progressively in stages; in the second group the arterial oxygen content was reduced in similar stages by progressively larger reductions in the concentration of inspired oxygen (hypoxic hypoxia). In the ischemic animals focal ischemia was produced by embolic occlusion of the right middle cerebral artery. RESULTS: In the normal rabbits, hypoxic hypoxia and hemodilution resulted in similar progressive increases in cerebral blood flow as arterial oxygen content fell. In the ischemic animals, there was a significant fall in cerebral blood flow in the ischemic region in all groups after arterial occlusion. Hemodilution resulted in a progressive increase in cerebral blood flow in both ischemic and nonischemic regions. With hypoxic hypoxia, however, cerebral blood flow in the ischemic region showed no increase or a slight decrease. CONCLUSIONS: Even though hypoxic hypoxia results in a marked increase in cerebral blood flow in normal brain, it does not significantly change cerebral blood flow in ischemic brain. In contrast, hemodilution resulting in a comparable degree of hypoxemia is capable of significantly increasing cerebral blood flow in ischemic brain. Therefore, the mechanism of blood flow augmentation by hemodilution in ischemic brain is probably related to a direct hemorheologic effect rather than to the resulting hypoxemia.

Animals↗
PubMed1992

"Subclinoid" carotid aneurysm with erosion of the anterior clinoid process and fatal intraoperative rupture.

We present the case of a patient with an aneurysm of the right internal carotid artery with subarachnoid hemorrhage. The aneurysm had resulted in erosion of the anterior clinoid process, but this was not recognized preoperatively. Intraoperative rupture during drilling of the clinoid necessitated vigorous packing that led to unintended carotid occlusion with subsequent fatal cerebral infarction. Preoperative recognition of the clinoid erosion may have prevented this catastrophe. To call attention to the potential for intraoperative rupture during exposure, we suggest the term subclinoid aneurysm to refer to aneurysms of the internal carotid artery that grow superolaterally and remain confined under the anterior clinoid process.

Aged↗
PubMed1992

Intracerebral hemorrhage due to cerebral arteriovenous malformations.

The most common presentation of a pial arteriovenous malformation (AVM) is spontaneous intracerebral hemorrhage (ICH). The peak incidence of ICH is early in the third decade of life. This article discusses the management of ICH of unknown etiology, ICH from angiographically visible AVM, and ICH from angiographically occult vascular malformations based on the current understanding of the natural history of these disease entities.

Cerebral Angiography↗
PubMed1991

Occlusion of an "accessory" distal anterior cerebral artery during treatment of anterior communicating artery aneurysms. Report of two cases.

Two cases are presented in which clip occlusion of a third distal anterior cerebral artery segment occurred during treatment of anterior communicating artery aneurysms. Case histories, angiograms, operative descriptions, and postmortem findings are presented. The incidence of this anomalous vessel is reviewed. Preoperative and intraoperative vigilance in determining the presence of this anomaly prior to clip placement is emphasized.

Adult↗
PubMed1991

Familial hemifacial spasm associated with arterial compression of the facial nerve. Case report.

This report of an 88-year-old woman with familial hemifacial spasm includes the first published postmortem description of hemifacial spasm with cross-compression of the seventh cranial nerve root exit zone by a redundant loop of the anterior inferior cerebellar artery and associated vascular plexus. Histological examination of the seventh and eighth cranial nerve complex suggested nerve degeneration because increased numbers of corpora amylacea were present just distal to the compression concavity. There was no evidence of demyelination or gliosis of the nerve. This case suggests that vascular compression of the nerve root exit zone is an important condition in the etiology of most of these cases. This is the third reported case of familial hemifacial spasm; to date, all such patients have had left facial involvement. The family pedigree in this case suggests a pattern of autosomal-dominant inheritance with partial penetrance. The genetic basis for familial hemifacial spasm may involve anatomical variants or anomalies of the posterior circulation, since both posterior inferior cerebellar arteries were congenitally absent in this case.

Aged↗
PubMed1990

Brain resection for exposure of deep extracerebral and paraventricular lesions.

In exposing deep extracerebral or paraventricular lesions, it sometimes may be preferable to resect a small amount of noneloquent brain tissue rather than retract the brain. This may be the case in carefully selected instances when, in the surgeon's estimate, brain retraction may result in significant parenchymal damage, in aneurysmal rupture, or in damage to important bridging veins. Some surgical approaches involving brain resection have been well described. This technical note discusses the following approaches that, though undoubtedly used by many surgeons sporadically, have received less formal attention: (1) anterior-inferior temporal resection for basilar aneurysms, (2) posterior-inferior temporal resection to approach the posterior incisura and avoid damage to the vein of Labbé, (3) parahippocampal resection to expose the posterior cerebral artery in the ambient cistern, (4) paramedial posterior parietal incision to approach the trigone of the lateral ventricle, (5) parasagittal resection to expose the interhemispheric fissure and avoid damage to bridging veins, (6) cingulate resection for pericallosal aneurysms, and (7) tonsillar resection for aneurysms of the peripheral portion of the posterior-inferior cerebellar arteries.

Arteriovenous Malformations↗
PubMed1990

Surgical excision of cerebral arteriovenous malformations: late results.

A follow-up study of 153 consecutive patients who underwent complete excision of an angiographically visualized intracerebral arteriovenous malformation was conducted. The follow-up period ranged from 0.5 to 10.6 years, with a mean of 3.8 years. The presenting clinical event was hemorrhage in about one-half of the patients and seizure in about one-third. There was a marked tendency for postoperative neurological deficits to improve with time, so that whereas the immediate postoperative rate of serious morbidity was 24.2%, only 7.8% of the patients were found to have serious morbidity at follow-up. An additional 3 patients had died, one of an unrelated carcinoma, making the mortality related to arteriovenous malformation 1.3%. The classification of Spetzler and Martin (43) was used retrospectively; the percentages of Grade I (easiest) through Grade V (most difficult) lesions were 7.8%, 22.9%, 28.8%, 26.8%, and 13.8%, respectively. The early result was well correlated to grade, with good or excellent results in 100%, 94.3%, 88.6%, 61%, and 28.6% of the patients in Grades I through V, respectively. At follow-up, 98.7% of the patients with arteriovenous malformations of Grades I, II, and III were in good or excellent condition. The late morbidity and mortality rates for the patients in Grades IV and V were 12.2% and 38.4%, respectively. Of the patients who did not have seizures before surgery, 8.2% had only one or two seizures during the immediate postoperative period, and 7.1% had late seizures that were well controlled with medication in all. Of the patients who had seizures before surgery, over half were either cured or greatly improved with respect to the seizures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Comparison of crystalloids and colloids for hemodilution in a model of focal cerebral ischemia.

Forty dogs were subjected to 6 hours of occlusion of the left internal carotid and middle cerebral arteries. They were divided into two "hemodilution groups" of 13 dogs each and a control "nonhemodiluted group" of 14 dogs. Thirty minutes after arterial occlusion, isovolemic hemodilution was performed by phlebotomy and infusions of low-molecular weight (MW) dextran in one group and of lactated Ringer's solution in the other group. The animals were sacrificed 1 week after temporary arterial occlusion. Hemodilution reduced the hematocrit to a level of 33% to 34%, which lasted throughout the week in both groups. After hemodilution there was a very significant reduction in blood viscosity, plasma total protein content, and fibrinogen levels in both groups in the acute stage; these levels gradually returned to baseline by the end of the week. In the group with lactated Ringer's solution hemodilution, both osmotic and oncotic pressures were decreased by hemodilution in the acute stage. In the control and low-MW dextran groups, osmotic and oncotic pressure remained unaltered throughout the week. Hemodilution resulted in a slight decrease in mean arterial blood pressure in all groups in the acute stage, but there were no significant changes in central venous, pulmonary arterial, or pulmonary wedge pressures. During the week of study, there were no differences in the cardiac index and total blood volume between the groups, and no significant changes in hematological parameters with the exception of a slight increase in bleeding time immediately after hemodilution with low-MW dextran. Daily neurological assessment showed consistently poorer condition during the first 5 days in the group with lactated Ringer's solution compared to either the control group or the group receiving low-MW dextran. Based on Mann-Whitney U-testing, the infarct volume of the lactated Ringer's solution recipients, expressed as a percentage of the total volume of that hemisphere (median 15.7%, range 6.6% to 25.2%) was significantly larger than that of the group receiving low-MW dextran (median 2.2%, range 0% to 15.8%) and that of the control group (median 11.9%, range 0% to 39.9%). The results indicate that, in this model, hemodilution with colloids was beneficial, whereas hemodilution with crystalloids was deleterious. It is likely that the decrease in oncotic pressure observed after hemodilution with lactated Ringer's solution is one of the most important reasons for its detrimental effect.

Animals↗
PubMed1990

Clinical aspects of vasospasm.

In summary, clinically significant vasospasm is characterized by several relatively consistent features. Those patients most at risk are adults, of either sex, who have had a subarachnoid hemorrhage about 4 to 9 days previously; who had a poor clinical grade on admission; and in whom a CT scan taken 24 to 48 hours after the ictus showed a thick layer of blood surrounding one or more of the major cerebral vessels. Initially afebrile, affected patients later develop a steady low-grade fever and may have an elevated WBC count, but no infectious source of fever can be found. Patients complain of worsening headache, but not as bad as the one a few days ago; the neck may feel a little more stiff. The pulse is slightly faster than usual, the blood pressure perhaps a bit higher; however, the ECG shows only "cerebral T waves." An antifibrinolytic agent may have been used. The serum sodium concentration has dropped significantly. Such patients need a more thorough examination than usual, directed toward more subtle neurologic signs, and a few extra checks during the day by both physician and nurses, so that we can apply what remedies we have when the patients are just "a little more confused," rather than later, when they are exhibiting decerebrate posturing and coma.

Humans↗
PubMed1990

Intracranial aneurysms. A review.

Intracranial aneurysms are common, and their rupture carries a grave prognosis. There is no effective way of preventing the development of intracranial aneurysms, but noninvasive means of detection are becoming increasingly practical and, at present, should be used routinely--at least in populations at high risk. SAH is frequently preceded by warning signs that, when recognized by the primary care or the emergency room physician, can lead to prompt and safe surgical intervention. About half the patients who suffer a major rupture either die or remain in poor condition as a result of the hemorrhage. In the rest, surgical intervention has become safer and very effective in preventing subsequent hemorrhage, which occurs in about 50% of patients if the aneurysm is left untreated. Since early surgery should be at least considered in the majority of these patients and since the early treatment of a patient after SAH is so specialized, it appears prudent to manage patients with SAH in units where the necessary neurological and neurosurgical specialized intensive care is available.

Combined Modality Therapy↗
PubMed1989

Combining the detachable balloon technique and surgery in imaging carotid cavernous fistulae.

Among 143 carotid cavernous fistulae, 10 cases could not be successfully treated by standard endovascular techniques alone; some form of surgical assistance was required. The circumstances included incomplete closure of the fistula while the internal carotid artery was occluded, failure to occlude the fistula after both arterial and venous endovascular approaches, hairpin loop of the cervical portion of the internal carotid artery, failure of previous trapping procedures, and failure to cure spontaneous carotid cavernous fistulae of the dural type after embolization of the external carotid feeders. These ten patients were cured by combining a surgical procedure and an interventional technique.

Adult↗
PubMed1989

Acute effects of isovolemic hemodilution with crystalloids in a canine model of focal cerebral ischemia.

We used 44 splenectomized dogs to study the effects of isovolemic hemodilution with a crystalloid solution. The dogs were randomly divided into a hemodilution and a control group. In each group, 17 dogs were subjected to 6 hours of internal carotid and middle cerebral artery occlusion, and five dogs received sham operations. Isovolemic hemodilution by phlebotomy and Ringer's lactate infusion was performed 30 minutes after arterial occlusion and resulted in an average hematocrit of 32-33%. Hemodilution significantly reduced viscosity, fibrinogen and total protein concentrations, and plasma oncotic pressure. Systemic arterial blood pressure and pulmonary wedge pressure decreased slightly with hemodilution, but central venous pressure and pulmonary arterial pressure did not change significantly. There was a similar decrease in cardiac index in both hemodiluted and control dogs, which may have been due to the effects of barbiturate anesthesia. Intracranial pressure increased significantly with time in all dogs subjected to arterial occlusion, but this increase was significantly more severe in the hemodiluted dogs. Specific gravity, measured just after the dogs were killed, 6 hours after hemodilution, was significantly lower in the white matter and basal ganglia of the left (ischemic) hemisphere in hemodiluted dogs than in controls. Regional cerebral blood flow decreased significantly in the left hemisphere after arterial occlusion. This decrease was almost completely reversed by hemodilution except in the basal ganglia, where the increase in edema caused by hemodilution was the greatest.

Animals↗