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Biomedical subjects

R W Barnes

Publications and source records attributed to R W Barnes.

At least 181 records · Page 10Linked to original sources
PubMed1976

Doppler jugular flow velocity to differentiate cardiac tamponade from failure.

Jugular venous flow velocity (JVFV) was analyzed by the directional Doppler velocity detector in an experimental model to distinguish postoperative acute cardiac tamponade from myocardial failure in eight dogs. Cardiac tamponade was produced by infusion of saline solution into the pericardial cavity; acute myocardial failure was created by temporary occlusion of the left anterior descending artery and circumflex coronary artery. A decrease in mean arterial pressure of only 10% was associated with a decrease in JVFV of 30% +/- 6% (mean +/- SE) in the tamponade group compared to 10% +/- 2% in the myocardial failure group. The difference was statistically significant (P less than .005) and persisted to severe levels of hypotension. An increase in venous pressure to 8 mm Hg resulted in a decrease in JVFV of 41% +/- 11% in the tamponade group. Thus, there is an early notable decrease in JVFV in tamponade, which allows differentiation from myocardial failure.

Animals↗
PubMed1976

Echoencephalographs of 100 consecutive acute psychiatric admissions.

Echoencephalography (ECHO) on 100 consecutive acute short-term psychiatric admissions showed a high (12 per cent) incidence of abnormalities. Incidence of midline ECHO abnormalities was 2 per cent, comparable to similar studies. Ventricular enlargement accounted for the majority of ECHO abnormalities. This study also confirmed a previous report of a relationship between third ventricular size and response to treatment. Use of the ECHO as a screening test for these patients was safe and rapid. Correlative studies tended to confirm ECHO findings.

Adolescent↗
PubMed1976

Value of segmental limb blood pressures in predicting results of aortofemoral bypass.

The efficacy of segmental limb blood pressure measurements, assessed noninvasively by Doppler ultrasound, in predicting the result of aortofemoral reconstruction was evaluated in fifty-two extremities with varying extent of aortoiliac and more distal arterial occlusive disease. Three prognostic correlates were analyzed: (1) preoperative proximal thigh/arm pressure index (TPI); (2) preoperative pressure gradient between adjacent leg segments (proximal thigh, above-knee, below-knee, and ankle), normally less than 30 mm Hg; and (3) early postoperative increase in the ankle/arm pressure index (API). After aortofemoral bypass, forty-one limbs (79 per cent) were asymptomatic or improved and eleven were unimproved. The mean TPI in extremities benefiting from aortofemoral bypass, 0.82 +/- 0.17 (+/-1SD) was significantly less than that of unimproved limbs, 1.01 +/- 0.09 (p less than 0.01). Aortofemoral bypass was beneficial in all twenty limbs with normal leg pressure gradients. Conversely, six of twenty-five legs with one abnormal gradient and five of seven with two abnormal gradients failed to improve. The postoperative increase in API was 0.1 or more in all forty-one improved extremities and was less than 0.1 in all eleven failures. Although eleven of thirty-two limbs (34 per cent) with arteriographic evidence of combined aortoiliac and subinguinal occlusive disease were not improved after proximal bypass, the result of operation could not be predicted from the angiographic pattern or severity of distal disease. Segmental limb blood pressures provide useful predictive indices of the efficacy of aortofemoral bypass and the potential need for more distal reconstruction in multisegmental disease.

Adult↗
PubMed1976

Evaluating peripheral arterial occlusive disease.

The clinical history and physical examination remain the most important factors in determining the presence, anatomic location, and physiologic extent of arterial occlusive disease and the need for operation. The physician should refrain from ordering arteriography to confirm the diagnosis of arterial disease unless operation is warranted. If peripheral arterial occlusive disease is diagnosed clinically, its anatomic and physiologic extent can be determined qualitatively and quantitatively by Doppler ultrasonic studies. These studies are also useful in following the natural history of or the influence of therapy on the course of arterial occlusive disease. Ultrasonic studies coupled with careful clinical assessment and with arteriographic evaluation prior to planned operation provide an optimal armamentarium for the diagnosis and management of peripheral arterial occlusive disease.

Angiography↗
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

Pedal vasomotor tone following aortofemoral reconstructions: a randomized study of concomitant lumbar sympathectomy.

A prospective randomized trial was undertaken to evaluate effects of lumbar sympathectomy as an adjunct to reconstructive surgery of the lower limb. The objective of this study was to assess the early postoperative effect of these procedures on pedal vasomotor tone. A pedal arterial resistance index (PARI) at rest was derived from the ratio of the ankle-digit systolic pressure gradient and pedal blood flow measured plethysmographically. Studies were performed on 32 normal individuals and pre- and postoperatively in 29 patients undergoing aortic reconstruction, 12 of whom were randomly chosen to have lumbar sympathectomy. The mean postoperative PARI in 17 patients who had reconstructions alone was 42+/-7 (S.E.M.) units which approximated the preoperative PARI (43+/-9 units) and normal control values (45+/-6 units). In contrast, 12 patients who had a concomitant lumbar sympathectomy had a significant reduction in the postoperative PARI (8+/-1 units, Pless than 0.005). These initial results indicate that the addition of lumbar sympathectomy to an aortic reconstruction may enhance blood flow to the foot by significantly reducing outflow resistance.

Adult↗
PubMed1976

Postoperative deep vein thrombosis in the lower extremity amputee: A prospective study with Doppler ultrasound.

The incidence of postoperative venous thrombosis and pulmonary embolism was assessed in 87 patients undergoing 96 major lower extremity amputations for ischemia. Prospective surveillance for deep leg vein thrombosis was carried out by Doppler ultrasound in 35 patients. There was no instance of major leg vein thrombosis and only one episode of a small non-fatal pulmonary embolus in a patient suffering trauma to the amputation stump after discharge from the hospital. This study suggests that clinically significant venous thromboembolism following current techniques of lower extremity amputation is not as common as previously reported. Doppler ultrasound is the most suitable technique for surveillance of venous thrombosis in these patients.

Adult↗
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

Doppler ultrasonic assessment of aortic stenosis by analysis of axillary arterial blood velocity upstroke time.

Rate-corrected velocity upstroke time (VUT) was calculated from analogue Doppler ultrasound recordings of axillary artery blood flow velocity in 25 patients with aortic stenosis documented by cardiac catheterization and in 14 normal individuals. The mean VUT in normal individuals was 0.11 +/- 0.02 second (+/- 1 SD), which was significantly lower than that of patients with aortic stenosis: 0.15 +/- 0.05 second (P less than 0.005). The VUT correlated with the aortic valve index and the aortic valve mean pressure gradient with correlation coefficients of 0.62 and 0.64, respectively (P less than 0.005). Arterial blood flow velocity assessment by Doppler ultrasound may be a useful noninvasive technique to evaluate patients with aortic valve disease.

Adult↗
PubMed1976

An index of healing in below-knee amputation: leg blood pressure by Doppler ultrasound.

Preoperative Doppler ultrasonic assessment of below-knee (BK) arterial signals and systolic blood pressures was performed on 50 patients undergoing 53 BK amputations for advanced ischemia. No patient was excluded from initial BK amputation unless gangrene at that level or severe joint contracture was present. Failure of healing of the BK amputation occurred in all five limbs with an undetectable Doppler arterial signal (and thus pressure) below the knee. Failure of amputation occurred in four of 16 limbs with detectable arterial signals and BK pressures less than 70 mm. Hg. Healing occurred in all 32 limbs with BK pressures greater than 70 mm. Hg. The differences in healing between these three groups are highly significant (p less than 0.005). This study suggests that Doppler ultrasonic assessment of BK arterial signals and pressures may be a simple hemodynamic correlate of healing of a BK amputation. Absence of a detectable arterial signal below the knee may be an indication for initial above-knee (AK) amputation in advanced ischemia.

Amputation, Surgical↗
PubMed1976

Directional arterial flow velocity: a sensitive index of changes in peripheral vascular resistance.

The effect of peripheral vascular resistance of directional arterial flow velocity was determined utilizing the directional Doppler velocity detector under experimental conditions. Femoral arterial resistance was increased and decreased, and arterial pressure, venous pressure, volume flow, and directional flow velocity were measured in the femoral artery. An increase in peripheral vascular resistance was associated with a marked increase in reverse flow and a decrease in forward flow velocity. Reverse flow decreased and forward flow velocity increased when resistance was lowered. The ratio of peak and mean reverse/forward (r/f) flow velocity changed in a linear relationship with vascular resistance. The increase in resistance associated with progressive hypovolemia was paralleled by an increase in r/f flow velocity which occurred before blood pressure declined. Thus alterations in directional arterial flow velocity can be used as a sensitive indicator of changes in peripheral vascular resistance.

Animals↗
PubMed1976

Limitations of the Doppler cerebrovascular examination in hemispheric cerebral ischemia.

The results of a directional Doppler ultrasound cerebrovascular examination were compared with arteriographic findings in 56 patients with resolved hemispheric strokes or transient ischemic attacks. Aortic arch arteriography revealed appropriate internal carotid artery lesions which were amenable to endarterectomy in 36 patients (64 percent). Of this group, abnormal Doppler findings were present in only 11 patients (31 percent). The definitive clinical applications of the Doppler cerebrovascular examination are limited to those settings in which demonstration of altered hemodynamics is decisive. In view of the apparent preponderance of embolic rather than hemodynamic mechanisms in the pathogenesis of focal cerebral ischemia, the Doppler examinations has only an adjunctive role in the evaluation of most patients with hemispheric symptoms of cerebrovascular occlusive disease. In such patients, preselection of candidates for diagnostic arteriography is an inappropriate application of the Doppler cerebrovascular examination.

Carotid Artery Thrombosis↗
PubMed1976

The role of prostaglandin E in the hemodynamic response to aortic clamping and declamping.

The infrarenal aorta was occluded for one hour in 11 control dogs and in eight dogs in which biosynthesis of prostaglandin E (PGE) was inhibited by administration of indomethacin (2.5 mg. per kilogram). The mean arterial pressure (MAP) in the indomethacin group was significantly (p less than 0.001) higher than in the control group at the end of 60 minutes of aortic occlusion (187 +/- 3 vs. 137 +/- 4 mm. Hg, mean +/- S.E.M.) and remained higher (p less than 0.001) after declamping. However, the decline in MAP at the time of aortic declamping was essentially the same for both groups. Total peripheral resistance (TPR) was higher in the indomethacin group than in the control group at the end of one hour of occlusion (159 +/- 13 vs. 124 +/- 12%, p less than 0.001) and remainded higher throughout the period following occlusion. The plasma concentration of PGE in the control group increased significantly (p less than 0.05) above control (630 +/- 110 to 1,299 +/- 261 pg. per milliliter) during the 60 minute period of occlusion with further increases to 1,447 +/- 389 and 1,523 +/- 256 pg. per milliliter (p less than 0.001) at 10 and 60 seconds after declamping, respectively. In the indomethacin group, PGE remained essentially unchanged throughout the clamping and declamping period and therefore was significantly (p less than 0.05) lower than in the control group. A similar pattern was observed in the tissue levels of PGE. This study suggests that PGE is released during and after infrarenal aortic occlusion and may be responsible for maintaining reduced TPR and MAP. However, hypotension after declamping is not affected by inhibition of PGE biosynthesis.

Animals↗
PubMed1976

Critique of the Allen test for continuity of the palmar arch assessed by doppler ultrasound.

The arterial circulation of both hands of 128 adults was assessed by the Allen test, a modified Allen test emphasizing proper hand position and by Doppler ultrasound. Full extension of the fingers during the Allen test resulted incomplete capillary refilling of the hand in 73 per cent of the patients. The modified Allen test, avoiding hyperextension of the wrist and fingers, revealed interruption of the palmar arch in only one patient with absence of the left radialy artery. There was complete concordance of findings by Doppler ultrasound and the modified Allen test, emphasizing the importance of maintaining proper hand position to avoid false interpretations of incomplete circulation of the palmar arch.

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↗
PubMed1976

Noninvasive ultrasonic carotid angiography: prospective validation by contrast arteriography.

Pulsed ultrasonic images of the carotid bifurcation in 82 vessels of 43 patients were compared independently with contrast arteriograms for stenosis (by percentage quartiles) or occlusion of the internal carotid artery. All 14 occluded vessels were identified correctly by ultrasound but were visualized on repeat examination. Estimation of percentage stenosis on ultrasonic images agreed with the quartile determination by contrast arteriography in 35 of 68 (51 percent) vessels and was within one quartile of correct interpretation in 48 of 68 (71 percent). The interpretative error of grading stenosis of ultrasonic images was due to vascular wall calcification which inhibited ultrasound transmission. This limitation was overcome by sound spectral (sonographic) analysis of distal internal carotid flow velocity which allowed estimation of stenosis within one quartile of that determined by contrast arteriography in 46 of 47 (98 percent) vessels.

Adult↗