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Biomedical subjects

R J Baird

Publications and source records attributed to R J Baird.

18 recordsLinked to original sources
PubMed1991

Thoracic aortic surgery.

Between 1982 and 1989, 119 patients had repair of thoracic aortic pathology. Thirty-seven had repair of ascending aortic aneurysms, with an 11% hospital mortality. Forty-one patients had urgent repair of acute type A aortic dissections, with a 32% hospital mortality. The independent predictors of mortality were the use of crystalloid cardioplegia, aortic dissection, and the use of an intraluminal prosthesis or the inclusion surgical technique. Better grafts and the resection technique has reduced mortality since 1986. Seventeen patients had their primary pathology in the aortic arch, with a 47% hospital mortality. The urgency of the procedure and crystalloid cardioplegia predicted an unsuccessful outcome. Seventeen patients had descending aortic aneurysms repaired, with an 18% mortality. The urgency of surgery was the predictor of mortality. Seven patients had a descending thoracic aortic disruption repaired, with one death (14%). Better graft materials, surgical techniques, and methods of myocardial protection have contributed to the improved results of thoracic aortic surgery in recent years.

Aortic Dissection↗
PubMed1978

Abdominal aortic aneurysms: recent experience with 210 patients.

In the 6 1/2 years ending June 1977, 210 patients with abdominal aortic aneurysms underwent operation at Toronto Western Hospital; 160 aneurysms (76%) were unruptured and 50 (24%) were ruptured. In the patients with unruptured aneurysms the mean age was 68 years; the oldest was 91, and 12 were more than 80 years of age. The overall hospital mortality was 5.6%. Death in hospital occurred in 1 (1.2%) of the 83 asymptomatic patients, 4 (7.4%) of the 54 symptomatic patients and 4 (17.0%) of the 23 patients for whom operation was considered urgent. In the patients with ruptured aneurysms the mean age was 71 years; the oldest was 90, and five were more than 80 years of age. The overall hospital mortality was 54%. The morbidity and mortality were analysed; in particular the reasons for the markedly variable hazard of operations for the three categories of unruptured aneurysm were sought. The surgical literature is confusing because of the interchanging use of the words unruptured, elective and symptomless. The current philosophy management and technique of operation in a large cardiovascular surgery service with many trainees are presented and a plea is made for a standardized and simplified operation, always performed with three assistants helping the operating surgeon.

Aged↗
PubMed1978

Optimal myocardial protection.

The low mortality and perioperative infarction rates for aortocoronary bypass (ACB) make them unsuitable for evaluating the adequacy of myocardial protection. Enzymatic and functional measurements were found to be sensitive and specific indicators of myocardial injury. A prospective concurrent study of 78 patients undergoing triple ACB was conducted to evaluate the effectiveness of three popular methods of myocardial protection. Group I (32 patients) had a single dose of cold (4 degrees C) potassium cardioplegic (CPC) solution infused inducing a mean myocardial temperature (MMT) of 31 +/- 4 degrees C/min. Group II (23 patients) had multiple doses of CPC solution 8nducing a MMT of 22 +/- 2 degrees C/min. Group III (23 patients) had intermittent anoxic arrest at a MMT of 28 +/- 1 degrees C. The groups were not randomized but had comparable clinical symptoms and catheterization findings. Serial measurements of cardiac specific creatine kinase (CK-MB) revealed a peak in enzymatic activity occurring 60 minutes following ACB. The highest CK-MB was significantly (P less than 0.01) lower in group II (25 +/- 8 IU/liter) than group I (50 +/- 8 IU/liter), or group III (68 +/- 14 IU/liter). Myocardial performance was evaluated after ACB by serially measuring left ventricular stroke work index (SW) and left atrial pressure (LAP) in response to volume loading. The rise in SW was significantly (P less than 0.01) greater in group II (3.0 +/- 0.7 gm.m/sq m/mm Hg) than in group I (1.4 +/- 0.7) or group III (1.8 +/- 0.9). The highest SW attained was higher (P less than .01) in group II (43 +/- 7 gm.m/sq m) than group I (19 +/- 6) or group III (34 +/- 8) at comparable LAP values (group I: 20 +/- 5 mm Hg; group II: 18 +/- 3; group III: 18 +/- 4). Post-operative clinical evaluation failed to differentiate among the three groups. The more sensitive indices, however, demonstrated the superiority of cold, multidose cardioplegia in providing optimal myocardial protection.

Anti-Arrhythmia Agents↗
PubMed1977

Arteriosclerotic femoral artery aneurysms.

Arteriosclerotic aneurysms of the femoral artery are uncommon lesions that occur in elderly men. In 30 patients 36 aneurysms were repaired at the Toronto Western Hospital from January 1965 to June 1977. Half of the patients presented with ischemia and one quarter with an enlarging mass, and one quarter had no symptoms. Two thirds had other aneurysms and one third had suffered from cerebral or myocardial ischemia. The technique of repair changed from reconstructive aneurysmorrhaphy before 1970 to use of an interposition arterial prosthesis thereafter. Minimal groin dissection, internal control of blood flow in the deep femoral artery, and use of an appropriate arterial prosthesis provided excellent results. Surgical repair is recommended for most symptomatic ones when the patient's life expectancy is more than 2 years.

Aged↗
PubMed1977

Thrombosis of Björk-Shiley aortic valve prosthesis: report of three cases.

Thrombotic malfunction of a Björk-Shiley aortic valve prosthesis occurred in three patients 6 to 16 months postoperatively. None of the patients had been taking anticoagulants. Although the presentation was acute, prodromal symptoms could be identified retrospectively in two of the patients. Two patients survived thrombectomy. Postoperative anticoagulant therapy is recommended in patients with these prostheses despite factors that may make such therapy riskier in specific patients. Attention to the character of murmurs and of the closure sound of the prosthetic valve must be part of the routine follow-up. In the emergency situation, when delay must be avoided, catheterization and angiography are unnecessary. The operative approach consists of complete thrombectomy without replacement of the valve or any of its components unless there is obvious periprosthetic leak or prosthetic wear.

Adult↗
PubMed1977

3. Current approaches to popliteal artery repair.

Trauma to the popliteal artery is potentially dangerous, and limb loss may result, especially with delayed diagnosis. Three anatomic factors contribute to the seriousness of the outcome: proximity of the artery to bone, superficial position of the artery and consequent lack of protection, and frequent associated injury to associated collateral blood vessels. Diagnosis of injury to the popliteal artery rests on suspicion and vigilance; the Doppler transcutaneous flow detector and angiography are often useful aids to diagnosis. Methods of treatment that have been used include arterial repair, grafting and fasciotomy, together with management of associated injuries. The bypass principle of vascular reconstruction may improve overall results.

Adult↗
PubMed1977

Ascending aorta to bilateral femoral artery graft via a ventral subcutaneous route.

Two patients were treated for grossly ischemic legs by a graft from the ascending aorta to both common femoral arteries. After leaving the mediastinum, the graft lay in the subcutaneous position throughout its course. In both patients, standard aorto-femoral repair was considered unduly hazardous because of gross obesity, large incisional hernias, previously unsuccessful vascular procedures, impaired renal function, emphysema, and complete occlusion of the abdominal aorta to the level of the renal arteries. Both patients had evidence of bilateral subclavian artery stenosis or occlusion. The technique of the operation is described and its assets and liabilities discussed. Within strict limitations, it is an alternative to axillo-femoral bypass.

Aged↗
PubMed1976

The response of diastolic myocardial tissue pressure and regional coronary blood flow to increased preload from blood, colloid, crystalloid.

An increase in the left ventricular end-diastolic pressure (LVEDP), resulting from the intravenous administration of blood, a colloid solution, or a crystalloid solution, was accompanied by an increase in both the inner:outer left ventricular wall flow ratio and the diastolic myocardial tissue pressure gradient. With a normal left ventricular end-diastolic pressure, the normal inner:outer flow ratio was just above unity and the minimum diastolic myocardial tissue pressure in the subepicardium was twice as high as in the subendocardium. When the left ventricular end-diastolic pressure was raised, the subepicardial tissue pressure rose earlier and to a higher degree than the subendocardial; thus a gradient which encourages subendocardial flow was increased. This paper correlates the changes in diastolic myocardial tissue pressure and in inner:outer flow ratios which occurred when eight dogs were transfused with blood, seven with colloid, and seven with lactated Ringer's solution. Regional diastolic myocardial tissue pressure was measured by the flow-cessation technique and regional flow by radioactive microspheres. The gradient in diastolic myocardial tissue pressure, which is a major contributory factor to adequate subendocardial perfusion under normal conditions, is of even greater importance when LVEDP is raised.

Animals↗
PubMed1975

A sterile technique for adjustment of intra-aortic balloon catheter position after closure of the groin incision.

Following insertion or prolonged pumping, intraaortic balloon position is occasionally found well below the desired site with the concomitant loss of mechanical advantage. Repositioning may mean having to advance a semisterile catheter into the arterial lumen. To alleviate this risk, a new technique of balloon catheter insetion is suggested whereby a 10 inch length of prosthetic material is sewn into the artery. The redundant length is allowed to protrude beyond the skin closure. If prolonged pumping is envisaged, the cuff may be left intact altogether or else it is amputated upon satisfying oneself that the balloon is placed in the desired position.

Assisted Circulation↗
PubMed1975

Surgical aspects of regional myocardial blood flow and myocardial pressure.

The surgical technique of cardiopulmonary bypass with either an empty beating or an empty fibrillating ventricle produces marked changes in the regional blood flow and oxygen demand of the left ventricle. This paper describes the changes which occurred in the regional perfusion of both the normal and the hypertrophied left ventricle during these conditions and relates them to the known changes in oxygen demand. It also correlates the changes in flow with the measurable changes in myocardial tissue pressure-systolic when the heart is beating and continuous when fibrillating. The various types of filbrillation had identical effects on both regional tissue pressure and regional flow. The subendocardial blood supply was adequate or more than adequate under each of these conditions so long as the coronary perfusion pressure was maintained at an adequate level. A low perfusion pressure during ventricular fibrillation of any type led to a marked reduction in flow to the subendocardial portion of the left ventricle: The presence of ventricular hypertrophy accentuated this danger.

Animals↗
PubMed1975

Identification and successful treatment of congenital microfistulas with the aid of directional Doppler.

Hitherto unidentifiable and therefore untreatable congenital microfistulas were detected with the aid of continuous-wave directional Doppler and a fine-beam pencil probe. The microfistulas formed part of the Klippel-Trenaunay (K-T) syndrome. The management of one case is reported in detail and in three others salient features are touched upon. Careful clinical and radiological examination failed to demonstrate any arteriovenous microfistulas. When Doppler ultrasound scanning was carried out, two discrete fistulas were discovered. Their extent and direction were mapped out accurately. Incisions were made directly over the markings displaying a pulsating capillary tuft of vessels. Further dissection exposed a feeding arteriole which was less than 1 mm. in diameter. Excision of the vascular malformations resulted in the cure of the patient. In another patient with the K-T syndrome in whom a cutaneous hemangioma involved the whole lower limb, in spite of a thorough and systematic search with a Doppler, no microfistulas could be demonstrated. It is suggested that all patients suffering from the K-T syndrome should be examined by Doppler ultrasound in the hope that microfistulas which elude radiodiagnostic techniques might be detected and treated surgically.

Adult↗
PubMed1975

Noninvasive assessment of aorta-coronary saphenous vein bypass graft patency using directional Doppler.

Noninvasive monitoring of patency of aorta-coronary bypass grafts can be achieved with reasonable accuracy using the continuous wave directional Doppler and a pencil probe. The character of the graphic record and the auditory signal generated by the flow through these new vessels perfusing the myocardium are distinctive because of both the pattern of flow and also the fixed and relatively immobile position of these grafts in the anterior mediastinum. A total of 226 aorta-coronary bypass grafts were monitored in the first postoperative week: 82 to the right coronary artery (RCA), 90 to the left anterior descending (LAD), and 56 to the circumflex and lateral ventricular branches. Interpretation of patency in these latter vessels was consistently unreliable and was abandoned early in the study. This unreliability was probably due to their short superficial course and their juxtaposition to the aorta and the pulmonary artery. In contrast, flow through grafts to the RCA and the LAD could be established in approximately 90%. Of 82 grafts to the RCA, flow could not be detected in four (5%) and was doubtful in two (2%). In 90 grafts to the LAD, no flow was observed in four (4%) and was doubtful in five (6%). Comparing noninvasive Doppler results with angiography in 34 grafts, no false negatives were found, but there were two or 10% false positives. Flow characteristics in a functioning internal mammary implant were also found to be quite different from those in an intact opposite mammary artery. This form of monitoring requires some practice and experience but is quick, cheap and noninvasive. It offers an acceptable degree of accuracy in monitoring aorta-coronary bypass grafts to the RCA and the LAD when the conduits are in the anterior mediastinum.

Coronary Artery Bypass↗