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Biomedical subjects

P T McDonald

Publications and source records attributed to P T McDonald.

At least 19 recordsLinked to original sources
PubMed1990

Differential survival of male and female partially resistant horn flies (Diptera: Muscidae) on steers treated with permethrin.

Males and females from a heterozygous, resistant strain (SR) of the horn fly, Haematobia irritans (L.), were tested for survival until reproductive maturity on steers with ear tags in outdoor, screened enclosures and on steers sprayed on the neck in an indoor isolation room. After 6 d, female SR flies on outdoor steers with one tag had 10 times greater survival than males; almost no SR flies on steers with two ear tags survived. Survival of male and female SR flies on steers sprayed on the neck was reduced during the first 24 h, but not thereafter. Lower survival of males compared with females on treated steers reflected differential survival of the sexes during exposure to treated cloths in a laboratory bioassay. Hair samples from neck, back, rump, and lower legs of steers with ear tags in outdoor pens were tested for toxicity to the SR flies. These bioassays indicated high localization of insecticide on the neck of steers with ear tags.

Animals↗
PubMed1990

Linkage, expression, and distribution of the pyrethroid resistance gene in the horn fly (Diptera: Muscidae).

A sex-linked gene for pyrethroid resistance in the horn fly, Haematobia irritans (L.), showed complete linkage to the male-determining gene in a laboratory colony that had been inbred for 10 generations. Within susceptible, heterozygous, and resistant populations, the level of resistance that was expressed was greater for females than for males. The increase in level of resistance conferred by the gene was similar for females and males. Preliminary synergism and allelism tests supported our supposition that the same gene was responsible for resistance in California, Florida, and Texas populations.

Animals↗
PubMed1989

Improving diagnosis of appendicitis. Early autologous leukocyte scanning.

A prospective nonrandomized study investigating the accuracy and utility of autologous leukocyte scanning in the diagnosis of apendicitis was performed. One hundred patients in whom the clinical diagnosis of appendicitis was uncertain underwent indium 111 oxyquinoline labelling of autologous leukocytes and underwent scanning 2 hours following reinjection. Of 32 patients with proved appendicitis, three scans revealed normal results (false-negative rate, 0.09). Of 68 patients without appendicitis, three scans had positive results (false-positive rate, 0.03; sensitivity, 0.91; specificity, 0.97; predictive value of positive scan, 0.94; predictive value of negative scan, 0.96; and overall accuracy, 0.95). Scan results altered clinical decisions in 19 patients. In 13 cases, the scan produced images consistent with diagnoses other than appendicitis, expediting appropriate management. Early-imaging111 In oxyquinoline autologous leukocyte scanning is a practical and highly accurate adjunct for diagnosing appendicitis.

Adolescent↗
PubMed1989

Popliteal artery entrapment: an evolving syndrome.

Popliteal artery entrapment can result in claudication and limb-threatening ischemia in the young adult. The purpose of this study was to evaluate prospectively those patients with popliteal artery entrapment. To define the syndrome, the methods used in diagnosis and the type of anatomic anomaly were established for each patient. From 1977 to 1988, 12 patients were found to have popliteal artery entrapment. The average age was 27 years, with all but three patients under age 40 years. All patients complained of calf claudication, and one had acute ischemia. The ankle pulses decreased with maneuvers in 10 patients; four patients had a resting ankle/brachial index less than one. All had diminished ankle/brachial indexes when a treadmill test was performed at 4.2 mph, 10% grade, for 10 minutes. All patients had biplanar arteriography with passive dorsiflexion and active plantar flexion. All results showed abnormal extrinsic compression or occlusion of the popliteal artery. Twenty limbs were affected; eight of 12 patients (67%) had bilateral entrapment. Type IV (37%) lesions were the most common, with type II (32%) and type III (26%) following closely. One (5%) type I lesion and no type V lesions were found. This is the largest single series of patients with popliteal entrapment in the United States. A treadmill test followed by biplanar arteriography established the diagnosis in all patients. Bilateral involvement was twice that reported in previous studies. Popliteal artery entrapment should be considered in the young adult with claudication and may be seen with greater frequency in an increasingly active population.

Adult↗
PubMed1988

Coronary artery disease in aortic surgery.

The incidence of coronary artery disease in patients coming to aortic surgery and the impact of aggressive preoperative cardiac catheterization and myocardial revascularization was prospectively analyzed in 59 patients. Seventy-five percent of patients had at least one-vessel involvement, and 32% had three-vessel or left main involvement. Patients with electrocardiographic evidence of coronary artery disease had at least one-vessel involvement 84% of the time and three-vessel, left main involvement 36% of the time. Sixty-four percent of patients with no preoperative indications of coronary artery disease had at least one-vessel involvement and 29% had three-vessel, left main involvement. Resting (39 patients) and exercise multiple-gated acquisition scans (22 patients) did not predict the presence of coronary artery disease in patients without a history or electrocardiographic evidence of coronary artery disease. Myocardial revascularization was performed prior to aortic surgery in 17 patients (29%). The operative mortality was 3.7% with two patients dying from noncardiac-related complications. There were two additional deaths prior to aortic surgery with one patient dying during coronary artery bypass grafting, and one dying of aneurysm rupture prior to repair, making the overall mortality associated with this approach 7.4%. Preoperative cardiac catheterization and an aggressive approach toward coronary artery bypass grafting reduces the risk of cardiac complications in aortic surgery.

Aged↗
PubMed1985

Localization of lower gastrointestinal hemorrhage. Experience with red blood cells labeled in vitro with technetium Tc 99m.

Seventy-six patients clinically suspected of having lower gastrointestinal bleeding were studied by scintigraphy utilizing red blood cells labeled in vitro with technetium Tc 99m. Sixteen patients required emergency surgery; bleeding was accurately localized in 15 (94%). One patient (6%) had a normal scan. A 20-month mean follow-up of the 16 patients showed no recurrent bleeding. Of 60 patients not requiring emergency surgery, bleeding was localized in 11, but the bleeding ceased. Forty-nine of the 60 patients had normal scans and had no further hemorrhaging during hospitalization. A 21-month mean follow-up of 38 of the 49 patients showed no further bleeding episodes or surgical procedures in 29 patients; however, eight patients required surgical procedures, including seven for gastrointestinal malignancies. Scanning of red blood cells labeled in vitro with 99mTc is accurate and efficacious in localization of bleeding sites that require emergency surgery for lower gastrointestinal hemorrhage.

Adult↗
PubMed1985

Management of patients with symptomatic extracranial carotid artery disease and incidental intracranial berry aneurysm.

Perioperative fluctuation of blood pressure and the use of anticoagulants during carotid endarterectomy may potentiate lethal aneurysm rupture in patients who have symptomatic extracranial carotid artery occlusive disease with incidental, asymptomatic, intracranial berry aneurysms. Ten patients having this combination are described in the present study. Of five men and five women whose mean age was 63 years, nine had symptomatic carotid bifurcation atherosclerosis, one had internal carotid fibromuscular dysplasia, and all had intracranial berry aneurysms ranging from 2 to 13 mm in diameter (mean diameter 6.6 mm). In seven patients, aneurysms were greater than or equal to 6 mm in diameter. Hypertension was present in seven patients and moderately severe in five. Three of the aneurysms were located in the intracranial internal carotid artery, five in the middle cerebral artery, three in the posterior communicating artery, one in the anterior cerebral artery, and one in the superior cerebellar artery. Twelve carotid reconstructive procedures were performed without morbidity related to aneurysm rupture. These included 10 carotid endarterectomies, one of which was combined with Dacron patch angioplasty and one of which was combined with a simultaneous coronary artery bypass; one carotid artery dilatation for fibromuscular disease; and one reoperative carotid endarterectomy with patch angioplasty. Three patients had correction of hemodynamically significant lesions, two of which were proximal to ipsilateral anterior circulation aneurysms. An intraluminal shunt and heparin anticoagulation therapy were used in all patients. Despite a concerted effort to control blood pressure, the patients' perioperative blood pressures ranged from 60/30 to 240/110 mm Hg. Three patients had subsequent elective clipping of intracranial aneurysms.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Arteries↗
PubMed1983

Etiologic factors for recurrent carotid artery stenosis.

Since 1966, 29 patients with recurrent carotid artery stenosis have been encountered. The mean (+/- SEM) internal between initial carotid endarterectomy and secondary presentation was 67.5 +/- 9.2 months (range 6 to 180 months). There was a disproportionate number of women with recurrent stenosis. The mean age at initial endarterectomy in patients with recurrent stenosis, 54.6 +/- 1.4 years, was significantly less (P less than 0.001) than that of all patients who had endarterectomy. To define the etiologic factors for recurrence, 21 of these patients were matched with case-control patients of the same age and sex who had undergone endarterectomy the same year but did not develop recognized recurrent stenosis. There was no significant difference in the incidence of hypertension, diabetes mellitus, coronary artery disease, bilateral carotid disease, other vascular operations, or family history for atherosclerosis in patients with recurrent stenosis compared to control patients. The indications for primary endarterectomy, angiographic distribution of disease, and operative details were similar in both groups. There was no difference in the incidence of regular, therapeutic aspirin ingestion following initial endarterectomy (52.5% in both groups). There was a striking difference in smoking habits. Ninety-five percent of patients with recurrent stenosis continued to smoke following initial endarterectomy, compared to 23.8% of control patients (P less than 0.001). Lipid fractionation studies were performed in both groups, and there were no significant differences in levels of cholesterol, triglycerides, high-density lipoprotein (HDL)-cholesterol, and total cholesterol/HDL-cholesterol ratio. Dose-response platelet aggregometry detected no differences between groups in the sensitivity of platelets to adenosine diphosphate (ADP), collagen, and epinephrine. Reoperation in patients with recurrent stenosis was associated with minimal morbidity, no deaths, and generally excellent results.

Anesthesia↗
PubMed1980

Vascular trauma secondary to diagnostic and therapeutic procedures: cardiopulmonary bypass and intraaortic balloon assist.

Significant arterial trauma can result from femoral arterial cannulation for cardiopulmonary bypass or intraaortic balloon pumping. Threat of imminent loss of limb or suture line disruption requires prompt surgical intervention. Delayed appearance of claudication, characteristically at 1 to 2 weeks postoperatively, is highly suggestive of iatrogenic iliofemoral injury. Arterial reconstructive surgery was necessary in three of five such patients.

Adult↗
PubMed1980

Popliteal artery entrapment syndrome. Clinical, noninvasive and angiographic diagnosis.

The popliteal artery entrapment syndrome is increasingly recognized as a cause of arterial insufficiency in the leg. Diagnosis is based on a clinical history of claudication, which may be atypical, physical examination, noninvasive exercise testing and angiography. Patients with normal ankle pulses and resting ankle/brachial pressure indexes may require extensive exercise testing to document arterial insufficiency. Angiographic demonstration of medial deviation of the popliteal artery is diagnostic of the popliteal artery entrapment syndrome. Arteries that appear normal on routine angiography require biplane angiography with various provocative maneuvers to demonstrate induced arterial stenosis. Using this approach, three additional cases of popliteal artery entrapment syndrome were diagnosed preoperatively and successfully treated with surgery.

Adult↗
PubMed1980

Fallibility of postoperative Doppler ankle pressures in determining the adequacy of proximal arterial revascularization.

Twenty-three consecutive patients with limb-threatening ischemia underwent proximal arterial revascularization. In all patients Doppler ankle pressure was measured hourly in the postoperative period. In 16 limbs with patent superficial femoral arteries, the pressure index increased from 0.55 +/- 0.06 to 0.78 +/- 0.06 within the 1st hour postoperatively. Twenty limbs with occluded superficial femoral arteries, did not demonstrate a significant increase until 3 hours postoperatively (from 0.41 +/- 0.06 to 0.62 +/- 0.05). Immediate improvement in the Doppler pressure index is to be expected in patients with isolated aortoiliac disease who undergo successful arterial reconstruction. Failure to demonstrate such improvement is diagnostic of an intraoperative accident. Lack of immediate improvement in patients with combined aortoiliac and femoropopliteal disease should not be construed as evidence of intraoperative failure. With 3 to 4 hours, however, the ankle/arm pressure ratio should exceed the preoperative value. The failure to do so within that interval is strongly suggestive of inadequate revascularization, and in most cases immediate operative revision or the later addition of a distal bypass procedure will be necessary.

Adult↗
PubMed1980

Carotid endarterectomy: regional versus general anesthesia.

The records of 421 patients who underwent carotid endarterectomy were reviewed. Between 1967 and 1972 carotid endarterectomy was performed with regional anesthesia in 232 patients. Ten per cent of these patients required the use of general anesthesia and a temporary indwelling shunt, because of the development of neurologic symptoms after temporary cross-clamping (5.6%) or the inability to tolerate regional anesthesia (4.3%). The 30-day mortality was 2.6 per cent. The incidence of fixed neurologic deficits was 2.2 per cent, and the incidence of transient neurologic deficits was 3 per cent. Between 1974 and 1976, 189 carotid endarterectomies were performed with general anesthesia and the routine use of a temporary indwelling shunt. The 30-day mortality was 0.5 per cent. The incidence of fixed neurologic deficits was 2.6 per cent; the incidence of transient neurologic deficits was 2.6 per cent. The use of general anesthesia with a shunt has not significantly changed the mortality or incidence of postoperative neurologic complications when compared with the authors' series performed with regional anesthesia. All patients in whom postoperative strokes occurred had multiple stenotic or occlusive lesions. Special precautions should be taken in this high-risk group.

Anesthesia, Conduction↗
PubMed1979

Popliteal vascular entrapment. Its increasing interest.

In the past 20 years since the first clinical management of a patient with a congenital anomaly associated with an abnormal medial head of the gastrocnemius muscle causing external compression on the popliteal artery, approximately 100 similar lesions have been documented in the world's literature. This has been a lesion of international interest, with only approximately 25% of the cases from hospitals in the United States. This present series of 14 lesions from Walter Reed Army Medical Center, Washington, DC, during a 12 1/2-year period beginning in September 1966 emphasizes the increasing interest in this lesion. The young athletic male in whom intermittent claudication develops with strenuous exercise or the middle-aged patient with a popliteal aneurysm should be evaluated for the possibility of popliteal vascular entrapment. Medial deviation of the popliteal artery seen angiographically is a classic finding, however, there might also be segmental occlusion of the midpopliteal artery. This series outlines various types of popliteal vascular entrapment and documents successful surgical management.

Adult↗