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Biomedical subjects

C R Gomez

Publications and source records attributed to C R Gomez.

At least 73 records · Page 4Linked to original sources
PubMed1993

Transcranial Doppler validation pilot study.

The use of transcranial Doppler sonography (TCD) for the evaluation of patients with ischemic cerebrovascular disease remains controversial. This study was organized to gather preliminary data regarding the sensitivity and specificity of TCD when compared to cerebral angiography in detecting stenosing lesions and collateral flow patterns of the anterior cerebral circulation. Forty-two patients from six medical centers were prospectively enrolled. Each received cerebral angiography and TCD testing within 24 hours of each other. Based on TCD criteria established a priori, the results were first analyzed by a blinded investigator and then by computer. Computerized analyses were then repeated with modified criteria. Collateral flow through the anterior communicating and ophthalmic arteries was detected with sensitivities of 62% and 100%, and specificities of 98% and 92%, respectively. Internal carotid artery proximal and distal severe ( greater than 70%) stenoses were detected with sensitivities of 79% and 100% and specificities of 88% and 97%. Middle and anterior cerebral artery stenoses and middle cerebral artery occlusion were detected with specificities exceeding 98%; however, the data were insufficient to determine sensitivity. Computerized analyses did not permit improvement of sensitivity and specificity of the baseline criteria. The selected TCD criteria are highly specific in detecting intracranial stenoses and collateral flow patterns of the anterior circulation. The criteria have limited but acceptable sensitivity and specificity in detecting internal carotid artery origin severe stenoses, and are highly sensitive in detecting ophthalmic artery retrograde flow. A study with a larger sample is necessary to provide definitive guidelines for diagnosis.

Adult↗
PubMed1993

Stroke following injection of a melted suppository.

BACKGROUND AND PURPOSE: Stroke following the intravenous injection of drugs may be secondary to the direct effect of the substance itself or from embolization by the inert vehicle used in the manufacturing process of the drug. CASE DESCRIPTION: We describe a 39-year-old man who developed a left homonymous hemianopia after intravenous injection of a melted suppository. CONCLUSIONS: Paradoxical fat embolism should be added to the possible list of stroke mechanisms in intravenous drug abusers.

Adult↗
PubMed1993

Perioperative stroke in patients undergoing head and neck surgery.

The risk of perioperative strokes has been demonstrated to be very low in general surgical procedures, and somewhat higher in cardiac and carotid artery procedures. We describe 5 patients who underwent major head and neck procedures not requiring carotid ligation and who postoperatively suffered strokes. These occurred between the first and ninth postoperative days. Four of the patients were thought to have had emboli, 3 to the cerebral hemispheres (2 ipsilateral and 1 contralateral to the neck dissections), and another to the lower brain stem. Hypoperfusion was thought to have caused the stroke in the fifth patient. All patients had risk factors for stroke. The cases in our series were difficult to diagnose because of the delayed onset and subtle nature of symptoms, as well as masking of speech and communication due to the operative involved. Thrombogenesis within the internal carotid and vertebral artery systems due to patient positioning and intraoperative cervical manipulation may be an important etiologic factor in this form of stroke.

Aged↗
PubMed1993

Cerebral and ophthalmic artery hemodynamic responses in diabetes mellitus.

OBJECTIVE: To address whether hemodynamic responses in the cerebral arteries and OAs may be altered in patients with diabetic retinopathy. We used TCD to evaluate the effects of changes in BP, posture, and exercise on MCA and OA blood flow velocities. RESEARCH DESIGN AND METHODS: We evaluated 13 patients with BDR, 19 with PDR, and 11 control subjects. Each was tested while supine, breathing 100% oxygen, sitting, and during exercise. RESULTS: Control subjects exhibited linear increases in velocity in the MCA and OA with increases in BP. Those with BDR had higher baseline sBP than control subjects. The MCA velocity response to BP in the BDR group was parallel to, but differed significantly from, the response in control subjects in compensation for the level of BP (ANCOVA F1,53 = 10.1, P = 0.003). The OA velocity response to BP was indistinguishable between the control subjects and the group with BDR. The group with PDR had more elevated BP than control subjects, and those with BDR had more advanced autonomic neuropathy. The PDR group had heterogenous velocity responses in the MCA and OA with respect to BP. None of the control subjects and 3 of 13 of the BDR group had abnormal autoregulatory velocity responses in the MCA or OA to 100% oxygen breathing, whereas 12 of 19 PDR patients were abnormal (P < 0.01). Of those with PDR, 4 had elevated MCA and 3 had elevated OA velocities while supine at rest. CONCLUSIONS: Patients with PDR demonstrated abnormal hemodynamic responses of the cerebral and ophthalmic circulation both at rest and with exercise.

Adult↗
PubMed1992

Cerebral lateralization and color perception: a transcranial Doppler study.

Eight normal subjects were examined in dark, light and color conditions. Mean cerebral blood flow velocity (MBFV) were recorded almost simultaneously from their posterior cerebral arteries (PCA) using transcranial Doppler (TCD) ultrasound. The side-to-side difference was significant during the dark (p = 0.0159) and color stimulation (p = 0.0001) but not in light condition. This side-to-side difference in MBFV was used to characterize lateralization of color perception. This showed that the right PCA was always greater than the left during the presentation of color stimuli. Primary psychological colors (blue, yellow, red and green) induced greater lateralization as compared with color resulting from a mixed blue-green wavelength. This suggests that the right visual cortex is selectively sensitive to wavelengths.

Adolescent↗
PubMed1992

Effect of cardiac dysfunction upon diastolic cerebral blood flow.

The transcranial Doppler (TCD) studies performed in 54 patients with various forms of cardiac dysfunction were reviewed and the results compared with those of normal individuals. There were 4 patients with aortic insufficiency, 5 being treated by intra-aortic balloon pumps, 12 patients with atrial fibrillation, 11 with syncope, and 22 undergoing cardiopulmonary resuscitation. In all instances, significantly low or even absent diastolic cerebral perfusion was found. The importance of this parameter, in the future evaluation and management of similar patients, is discussed.

Cardiovascular Diseases↗
PubMed1992

Establishing a neurology service in support of Operation Desert Storm.

As a result of Operation Desert Storm, a neurology service was established in the Fort Leonard Wood MEDDAC. Between January 1 and April 30, 1991, a total of 315 new neurology patients were seen in consultation. This number plus all the follow-up visits add up to a total of 750 clinical encounters during that period. The characteristics of this service (population served, reasons for referral, and diagnoses) were not significantly different than has been previously reported. The level of activity, by MS3 standards, qualifies this MEDDAC to have two neurologists.

Hospital Bed Capacity, 100 to 299↗
PubMed1991

Atrial septal aneurysm and stroke: a transesophageal echocardiographic study.

The prevalence and morphologic characteristics of atrial septal aneurysms identified by transesophageal echocardiography in 410 consecutive patients are described. Two groups of patients were compared: Group I consisted of 133 patients referred for evaluation of the potential source of an embolus and Group II consisted of 277 patients referred for other reasons. An atrial septal aneurysm was diagnosed by transesophageal echocardiography in 32 (8%) of the 410 patients. Surface echocardiography identified only 12 of these aneurysms. Atrial septal aneurysm was significantly more common in patients with stroke (20 [15%] of 133 vs. 12 [4%] of 277) (p less than 0.05); right to left shunting at the atrial level was demonstrated in 70% of patients in Group I and 75% of patients in Group II by saline contrast echocardiography. Four patients in Group I had an atrial septal defect with additional left to right flow. There was no difference between the two groups in aneurysm base width, total excursion or left atrial or right atrial excursion. However, Group I patients had a thinner atrial septal aneurysm than did Group II patients. It is concluded that an atrial septal aneurysm occurs commonly in patients with unexplained stroke, is more frequently detected by transesophageal echocardiography than by surface echocardiography and is usually associated with right to left atrial shunting. Treatment (anticoagulant therapy vs. surgery) of atrial septal aneurysm identified in stroke patients can be determined only by long-term follow-up studies.

Adult↗
PubMed1991

Transcranial Doppler ultrasound following closed head injury: vasospasm or vasoparalysis?

Nine patients suffering closed head injury were studied using transcranial Doppler ultrasound recording of the basal cerebral arteries. On admission, six patients had Glasgow Coma Scores of 7 or less, while three had initial scores of 8-10. Eight of the nine patients (82%) developed abnormally high mean velocities (greater than or equal to 110 cm/s) in one or more vessels. The onset, duration, and amplitude of the altered flow velocities were somewhat different from those that are seen with vasospasm after aneurysmal subarachnoid hemorrhage, which tend to occur later. Cerebral angiography in one of the study patients confirmed the presence of vasospasm. Multivariate regression analysis showed a definite correlation between the velocities recorded, even when abnormally elevated, and concurrent pH and PCO2 measurements (p = 0.01, R2 = 0.23). Although these results suggest that the cerebral vasculature retains its vasoreactivity following head injury, arguing against vasoparalysis, inconsistencies found in some of the patients lead us to think that both vasospasm and vasoparalysis may occur following head trauma but that they may have different temporal profiles.

Adolescent↗
PubMed1991

Superiority of transesophageal echocardiography in detecting cardiac source of embolism in patients with cerebral ischemia of uncertain etiology.

The diagnostic yield of transesophageal and transthoracic echocardiography for identifying a cardiac source of embolism was compared in 79 patients presenting with unexplained stroke or transient ischemic attack. There were 35 men and 44 women with a mean age of 59 years (range 17 to 84); 52% had clinical cardiac disease. Both transthoracic and transesophageal echocardiograms were performed using Doppler color flow and contrast imaging. Transesophageal echocardiography identified a potential cardiac source of embolism in 57% of the overall study group compared with only 15% by transthoracic echocardiography (p less than 0.0005). Compared with transthoracic echocardiography, transesophageal echocardiography more frequently identified atrial septal aneurysm associated with a patent foramen ovale (9 versus 1 of 79 patients, p less than 0.005), left atrial thrombus or tumor (6 versus 0 of 79 patients, p less than 0.05) and left atrial spontaneous contrast (13 versus 0 of 79 patients, p less than 0.0005). All cases of left atrial thrombus or spontaneous contrast were identified in patients with clinically identified cardiac disease. In the 38 patients with no cardiac disease, transesophageal echocardiography identified isolated atrial septal aneurysm and atrial septal aneurysm with a patent foramen ovale more frequently than transthoracic echocardiography (8 versus 2 of 38 patients, p less than 0.05). The two techniques had a similar rate of identifying apical thrombus and mitral valve prolapse. Overall, transesophageal echocardiography identified abnormalities in 39% of patients with no cardiac disease versus 19% for transthoracic echocardiography (p less than 0.005). Thus, transesophageal echocardiography identifies potential cardiac sources of embolism in the majority of patients presenting with unexplained stroke.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Infarction↗
PubMed1991

New method for optimal stabilization of the transcranial Doppler transducer during monitoring: normal controls and patient application.

Maintaining proper alignment of the transcranial Doppler probe during continuous monitoring has been a major limiting factor in its clinical and experimental application. We recently developed a simple yet reliable method of probe stabilization that allows continuous monitoring of blood flow velocities from any of the vessels accessible through the transtemporal window without regard to patient position or head movement. Under laboratory conditions, blood flow velocities were recorded in 5 subjects in the supine, sitting, standing, and head-down positions. Also, measurements were carried out during flexion, extension, lateral rotation, and tilting of the neck. In addition, 10 patients were successfully monitored in the acute stroke unit for periods of 12 to 72 hours. There was excellent preservation of Doppler waveforms during all these maneuvers. This device offers a method of stabilizing transcranial Doppler transducers during continuous monitoring, which is more practical than those available so far. It results in an expansion of the potential clinical and experimental applications of this ultrasonic technique.

Blood Flow Velocity↗
PubMed1991

Fourier analysis of the cerebrovascular system.

We performed Fourier analysis of the middle cerebral artery blood flow velocity waveform envelope in 14 normal subjects (group A) and 15 patients, of whom five had arteriovenous malformations (group B), five had cerebral vasospasm (group C), and five had arterial hypertension (group D). Measurements were obtained under conditions of normocapnia, hypercapnia, and hypocapnia. The Fourier coefficients measured in the first five harmonics of the Doppler waveforms of group A were used as the reference baseline and were compared with the coefficients found in the other three groups. Group B showed significantly lower Fourier coefficients, while groups C and D showed higher coefficients (p less than 0.05). The elevation of the Fourier coefficients occurred in an alternating pattern in group C and a decremental pattern in group D. This distinction was attributed to possible differences in the underlying pathophysiological processes. The degree of vascular distensibility of the cerebral arterioles, inferred from the shape of the Fourier analysis curves, was compared in all four groups. Vascular distensibility was characterized as abnormal in arteriovenous malformations, vasospasm, and arterial hypertension. Fourier coefficients may be better indicators of cerebrovascular abnormalities than mean blood flow velocity in hypertension and pulsatility index in arteriovenous malformations, vasospasm, and hypertension.

Adult↗
PubMed1991

Transcranial Doppler in reversible migrainous vasospasm causing cerebellar infarction: report of a case.

A young woman with a history of classic migraine suffered a large cerebellar infarction. Comprehensive evaluation did not disclose any potential causes for the stroke and she had no other risk factors. Transcranial Doppler (TCD) was useful in identifying vasospasm of the vertebral arteries. Following treatment with propranolol, angiography and repeat TCD revealed resolution of the vasospastic disorder. TCD is a useful noninvasive tool in detecting vasospasm associated with ischemic lesions in certain patients with migraine.

Adult↗
PubMed1990

Meso-diencephalic infarction: a not so rare form of stroke.

26 patients admitted with clinical pictures consistent with meso-diencephalic infarction were studied using computerized axial tomography, magnetic resonance imaging and angiography. All of the patients presented symptoms in two of three major categories which comprise the "top of the basilar" syndrome. Lesions in the territory of the basilar-communicating artery were demonstrated in 22 of them. The remaining patients died before adequate neuroimaging documentation was obtained. Overall prognosis appeared relatively good since 80% of the patients recovered completely or incompletely from the ictus. Meso-diencephalic infarction is a very important and not uncommon subtype of cerebrovascular disorder.

Adult↗
PubMed1990

A comparison of transcranial Doppler ultrasound (TCD) and radioactive microspheres in determining cerebral perfusion in normal and low flow states.

We have previously utilized the technique of transcranial Doppler (TCD) ultrasound to determine cerebral perfusion in patients undergoing cardiopulmonary resuscitation (CPR). In order to assess if TCD can reliably measure alterations in cerebral perfusion under conditions of normal and low cardiac outputs, we compared TCD measured blood flow velocities in the middle cerebral artery (MCA) of six piglets with radioactive microsphere determinations of total cerebral perfusion at baseline normal sinus rhythm (NSR), during CPR, and following return of spontaneous circulation (ROSC). Peak systolic and mean blood flow velocities were compared to the microsphere perfusion results on 15 different occasions; six during NSR, five during CPR, and four following ROSC. Although qualitative alterations in TCD measurements reflected changes in microsphere perfusion, we could not find a statistically significant correlation between either peak systolic or mean MCA blood flow velocities and microsphere perfusion measurements either overall or in any subgroup. The possible reasons which may explain the findings are discussed.

Animals↗
PubMed1990

Transcranial Doppler determination of cerebral perfusion in patients undergoing CPR: methodology and preliminary findings.

STUDY OBJECTIVES: To correlate cerebral arterial blood velocity measurements as determined by transcranial Doppler ultrasound with various resuscitation maneuvers performed in an uncontrolled manner in a series of cardiac arrest patients undergoing standard resuscitation. TYPE OF PARTICIPANTS: Any patient undergoing resuscitation for a nontraumatic cardiac arrest was eligible for the study. INTERVENTIONS: Resuscitation was carried out while flow velocities were monitored in various intracranial arteries by transcranial Doppler ultrasound. Vessel identification was based on the angle and depth of insonation. MEASUREMENTS AND MAIN RESULTS: The internal carotid artery was located more consistently than either middle cerebral or ophthalmic arteries and provided superior waveforms for analysis. Alterations in flow velocity were noted and correlated to various therapeutic interventions. Flow velocities were 70% of normal during the early phase of resuscitation but deteriorated over time until there was no evidence of net forward flow. Even early in CPR, flow was demonstrated only during systole. CONCLUSION: Transcranial Doppler ultrasound appears to be a potentially promising means of determining cerebral flow in patients undergoing CPR.

Brain↗