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Biomedical subjects

J C Hoak

Publications and source records attributed to J C Hoak.

At least 73 records · Page 4Linked to original sources
PubMed1977

Detection of deep vein thrombosis with an automatic electrically calibrated strain gauge plethysmograph.

A new strain gauge plethysmography was developed to permit accurate electrical calibration and automatic calculation of limb blood flow from a panel meter. This instrument was used to quantitate maximum venous outflow (MVO) in both limbs of 20 normal volunteers and 387 limbs of 195 patients with clinically suspected leg vein thrombosis. The MVO of normal subjects averaged 45 +/- 18 cc/minute/100 cc of calf tissue (mean +/- 1 SD). In 69 limbs with deep vein thrombosis documented by Doppler ultrasound and/or phlebography, the MVO averaged 17 +/- 13 cc/minute/100 cc, which was significantly less than that of normal limbs (p less than 0.001). Only three of 31 limbs with venous thrombosis above the knee had MVO above 20 cc/minute/100 cc, the lower limit of normal, for a diagnostic sensitivity of 90%. The specificity of a normal MVO in excluding deep vein thrombosis was 81%, with only a 1% rate of false-negative diagnoses above the knee. This automatic strain gauge plethysmograph has the attribute of providing rapid quantitation of limb venous hemodynamics which facilitates noninvasive diagnosis and follow-up assessment of venous disease.

Doppler Effect↗
PubMed1976

Spontaneous platelet aggregation in arterial insufficiency: mechanisms and implications.

To investigate the clinical implications and mechanisms of spontaneous platelet aggregation (SPA) in man, 150 normal subjects, 22 patient controls and 130 patients with vascular insufficiency were studied. SPA was negative in normal subjects and patient controls whereas it was positive in 36 of 66 (54%) patients with transient ischemic attacks, 6 of 32 (19%) patients with stable angina, 7 of 10 (70%) patients with acute myocardial infarction and 11 of 14 (80%) patients with acute peripheral arterial insufficiency. The SPA was inhibited with aspirin in vivo, and inhibited competitively in vitro by low concentrations of aspirin, 2-chloroadenosine, prostaglandin E1 or apyrase but only by high concentrations of heparin or hirudin. Addition of platelet-poor plasma from patients with positive SPA did not cause normal platelets to aggregate. Treatment of patients who had acute peripheral arterial insufficiency with aspirin and dipyridamole prevented SPA with notable clinical improvement of the ischemic changes.

Adenosine↗
PubMed1976

Venous disease. Advances in objective diagnosis.

A number of newer noninvasive or minimally invasive diagnostic techniques overcome the inaccuracies of clinical diagnosis of venous disease. Among these are Doppler ultrasound; plethysmography, especially the strain-gauge technique; the 125I fibrinogen uptake test; and radionuclide phlebography. Contrast phlebography is still the procedure of choice when diagnostic controversy remains or when facilities for the other techniques are not available.

Fibrinogen↗
PubMed1976

Platelet hyperaggregability in idiopathic recurrent deep vein thrombosis.

Studies of platlet function were performed in 30 patients with idiopathic recurrent venous thrombosis. Evidence of platelet hyperactivity was found in 14 patients who exhibited spontaneous platelet aggregation and in 13 patients who had evidence of circulating platelet aggregates. No other differences in clinical characteristics or coagulation parameters could be elucidated between these two subgroups. In nine patients who had 51Cr-labeled platelet survival studies, there was a good correlation between the platelet hyperactivity and shortened platelet survival. Spontaneous platelet aggregation was inhibited both in vivo and in vitro by aspirin. In addition, the circulating platelet aggregates were normalized by combination treatment with aspirin and dipyridamole. The results indicate that the idiopathic recurrent venous thrombosis patient population could be differentiated by the platelet function tests into subgroup I, in which no platelet abnormality could be detected, and subgroup II, where platelet hyperaggregability was present. These results indicate that the role of platelets should be considered in the pathogenesis of recurrent venous thrombosis and therapy with agents which inhibit platelet aggregation may be beneficial in the patients with platelet hyperaggregability.

Adult↗
PubMed1976

Heterogeneity of antibody response to human platelet transfusion.

To study the antibody response to human platelet transfusions, nine thrombocytopenia patients with bone marrow failure were given 6 U (3X10(11)) of random platelet concentrates twice a week. Before transfusion, none of the patients had preexisting antibodies detectable with lymphocytotoxicity, platelet aggregation, or capillary leukoagglutination techniques. After receiving 18-78 U of platelets, they became refractory to further transfusions of random platelets and alloantibodies were detectable. Two patterns of antibody response could be identified. In three patients, the sera were not lymphocytotoxic with a panel of standard cells in which all the known HLA antigens in the first and second series were represented at least once. Yet, they caused platelet aggregation with 30, 24, and 60%, respectively, of a donor population studied. The aggregating activities were inhibited by antihuman IgG but not by antihuman IgA or antihuman IgM antiserum. The aggregating antibodies could be absorbed out with donor platelets but not lymphocytes or granulocytes. Antibodies from two of these patients aggregated platelets of their respective siblings matched for both HLA haplotypes. Transfusion of platelets from these two siblings did not increase the platelet count while platelets obtained from aggregation-negative donors did. The sera from the remaining six patients were lymphocytotoxic with 15-100% of the panel of standard cells. They also had aggregating antibodies, which could be absorbed out by both platelets and lymphocytes, suggesting that they were HLA antibodies. These data suggest that the development of platelet-specific antibodies may play an important role in the immunological rejection of isologous platelets, and should be considered in the selection of donors for patients who are refractory to platelets from random donors.

Adult↗
PubMed1976

Accuracy of Doppler ultrasound in clinically suspected venous thrombosis of the calf.

Doppler ultrasonic examinations and contrast phlebography were performed on 55 limbs of 43 patients with a clinical diagnosis of venous thrombosis of the calf and without phlebographic evidence of thrombosis above the knee. There was diagnostic concurrence of Doppler and venographic evaluations in 46 of 55 limbs studied. There was only one instance of a false-negative diagnosis by Doppler examination. Of the eight false-positive Doppler examination findings, an alternate clinical diagnosis affecting venous flow in the calf was evident in six patients. The diagnostic importance of augmentation of flow velocity of the posterior tibial vein upon release of compression of the calf is emphasized. A normal Doppler examination finding may accurately exclude significant deep venous disease in a patient with clinical manifestations of venous thrombosis in the calf.

Adolescent↗
PubMed1975

Fallibility of the clinical diagnosis of venous thrombosis.

Doppler ultrasound examination confirmed the diagnosis of acute venous thrombosis in only 194 (37%) of 527 patients. Of the remaining 333 patients, 245 (74%) had some other evident cause of the limb complaints. The postphlebitic stasis syndrome; symptomatic varicose veins; congestive heart failure; leg trauma; venous or lymphatic obstruction by malignancy; cellulitis or lymphangitis; arthritis; and pregnancy were etiologic factors in these patients. The proved inaccuracy of the bedside diagnosis of leg vein thrombosis stresses the need for accurate objective verification of venous disease before committing the patient to a full course of anticoagulant therapy. For most clinicians, a contrast phlebogram is the most available and reliable diagnostic procedure.

Acute Disease↗
PubMed1975

Use of platelet aggregometry in selection of compatible platelet donors.

To determine if platelet aggregometry was useful in selecting compatible platelet donors, six patients who had become refractory to random platelets were studied. Serum from the patient was added to citrated platelet-rich plasma from the prospective donor in a standard aggregometry system. Serial aggregometry studies revealed no platelet aggregation unless the refractory state had been reached. At that time positive aggregation occurred only between the poorly matched pairs. A correlation between platelet aggregation and HL-A histocompatibility was noted. Family members with negative aggregation were selected as donors, and their platelets were able to provide consistently satisfactory increments in the platelet count of the recipient who was refractory to random donors. In contrast, platelets from family members who exhibited positive aggregation failed to do so. These findings suggest that platelet aggregometry can be used to select compatible platelet donors.

Blood Donors↗