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Biomedical subjects

D K Baird

Publications and source records attributed to D K Baird.

36 records · Page 2Linked to original sources
PubMed1986

Cardioplegic solution: a contamination crisis.

Eleven patients were given varying doses of cardioplegic solution contaminated with Enterobacter cloacae. Five patients died. Early bleeding, necessitating reoperation, occurred in eight patients and a total of 126 units of blood and 203 units of platelets were given (range 2 to 19 and 15 to 47 units, respectively). Mycotic aneurysms developed in four patients, rupturing between the ninth and eleventh postoperative day. Only one of these patients survived. Other complications included adult respiratory distress syndrome (three patients), renal failure (four patients), sternal infections (six patients), and organic brain syndrome (five patients). Although some factors of gram-negative septicemia were identified in retrospect, others were masked by the clinical setting in which it occurred. We recommend that each dose of cardioplegic solution be prepared on an individual basis and used immediately. We also recommend that "sternal blood" be cultured on all patients. The subtle features of "gram-negative septicemia" necessitate urgent investigation and treatment. The combination of low white cell count, high cardiac output, and low peripheral vascular resistance should be assumed to indicate septicemia until proved otherwise. A full coagulation screen including platelet function and fibrin degradation products should be performed in any and all patients with these findings. Mycotic aneurysms mandate urgent reoperation with interposition of a saphenous vein segment of these patients are to survive.

Acute Disease↗
PubMed1983

Coronary artery surgery in Australia. Report from the Committee of the National Heart Foundation Coronary Artery Surgery Register.

Clinical data on all patients who have undergone coronary artery surgery in Australia are collected, audited, and published each year by the National Heart Foundation of Australia. These data from 1971 to 1980 are summarized and show the indications for operation, the variation in numbers of patients operated on in each state and unit, and the overall increase in number of operations during the decade.

Australia↗
PubMed1981

Influence of heart rate and atrial transport on left ventricular volume and function: relation to hemodynamic changes produced by supraventricular arrhythmia.

The response of the left ventricle to pacing-induced changes in heart rate and the atrioventricular (A-V) relation was examined with equilibrium gated radionuclide ventriculography in 20 patients who had normal ventricular function after surgery for recurrent supraventricular tachycardia. In 10 patients count-derived left ventricular ejection fraction, end-diastolic volume and stroke volume were measured during sinus rhythm and during atrial pacing at 120, 140 and 160 beats/min. In the other 10 patients similar determinations were made during sequential A-V and simultaneous ventricular and atrial (V/A) pacing, both at rates of 100 and 160 beats/min. Left ventricular ejection fraction did not change significantly with atrial pacing (from 0.65 +/- 0.02 [mean +/- standard error of the mean] at a baseline sinus rate of 91 +/- 3 beats/min to 0.62 +/- 0.03 at 160 beats/min) despite a progressive decrease in end-diastolic volume. The percent reduction in end-diastolic volume (% delta EDV) and stroke volume (+ delta SV) from the baseline values was linear and related to change in heart rate (delta HR) as % delta EDV = -0.60 delta HR + 5.19 (r = 0.71; p less than 0.01) and % delta SV = -0.62 delta HR + 5.03 (r = 0.76; p less than 0.001). Left ventricular ejection fraction with baseline sequential A-V pacing at 100 beats/min was 0.67 +/- 0.03 and not significantly altered by either sequential A-V or simultaneous V/A pacing at 160 beats/min. At 100 beats/min, loss of atrial transport with simultaneous V/A pacing resulted in a small reduction in end-diastolic volume from a baseline value of -9.0 +/- 1.9 percent (p less than 0.01) and a nonsignificant reduction in stroke volume of -3.7 +/- 1.6 percent. During simultaneous V/A pacing at 160 beats/min, the reduction in end-diastolic and stroke volumes from the baseline value was -26.6 +/- 3.8 percent and -28.8 +/- 4.3 percent, respectively (both p less than 0.01), but was significantly smaller (-16.1 +/- 3.6 percent and -19.2 +/- 4.1 percent, respectively [p less than 0.05]) when atrial transport was maintained during sequential A-V pacing at the same heart rate. During simultaneous V/A pacing at 160 beats/min, two thirds of the reduction in end-diastolic and stroke volumes from the baseline value was due to the increment in heart rate as assessed from sequential A-V pacing and the other third was due to loss of atrial transport. The data indicate that the hemodynamic consequences of supraventricular tachyarrhythmias in patients with normal ventricular function are due primarily to decreases in ventricular volume as heart rate is increased and atrial contribution is lost rather than to any changes in left ventricular ejection fraction.

Adult↗
PubMed1981

Pseudoaneurysm of the left ventricle.

A case study is reported of a patient with rheumatoid arthritis who developed a pseudoaneurysm of the left ventricle after inferior myocardial infarction. The clinical diagnosis was confirmed by radionuclide cardiac blood pool imaging and by contrast ventriculography; the aneurysm was successfully excised.

Diagnosis, Differential↗
PubMed1981

Aortic and mitral valve replacement in a patient with severe haemophilia A.

A forty-nine year old man with severe Haemophilia A developed left ventricular failure as a complication of valvular heart disease. On November 26th, 1979, open heart surgery was performed and both the aortic and mitral valves were replaced with porcine heterografts. Replacement therapy in the form of Factor VIII concentrates maintained the Factor VIII coagulant level at 100% until ten days post-operatively and a total dose of 116,600 units were given. The patient described is the first haemophiliac to undergo open heart surgery in Australia and the first reported case in the world to have had a successful double valve graft. With the current availability of factor VIII concentrates, elective surgical procedures are being performed more frequently. Such procedures require careful pre-operative planning and post-operative monitoring of replacement therapy to ensure satisfactory haemostasis. Although haemostatic defects may occur after open heart surgery, this case report illustrates that the haemostatic problems of open heart surgery and haemophilia can be prevented by pre-operative planning and meticulous post-operative monitoring of replacement therapy.

Aortic Valve↗
PubMed1979

Coronary bypass grafting in early stages of acute myocardial infarction.

Acute coronary bypass surgery was performed in four patients with early anterior myocardial infarction due to severe proximal stenosis of the left anterior descending artery. Improvemnet of left ventricular anteroapical wall contraction was detected at the completion of the operation, in the early postoperative phase, and six to 18 months after surgery. It is concluded that critically ischaemic myocardium was salvaged by revascularization.

Adult↗
PubMed1979

Preoperative and postoperative technetium-99m pyrophosphate myocardial scintigraphy in the assessment of operative infarction in coronary artery surgery.

The incidence of operative myocardial infarction was assessed by electrocardiogram (ECG) and technetium-99m pyrophosphate (99mTc-PyP) myocardial scintigrams in 89 consecutive patients undergoing coronary artery bypass grafting (CABG). Myocardial scintigrams were performed on the day before operation and repeated 2 to 3 days postoperatively. All patients survived operation, with three in-hospital deaths not related to myocardial infarction (mortality rate 3 percent). Operative infarction was assessed to have occurred in four of 89 patients (4 percent). Two had new Q waves and positive scintigrams; one, major ST-T wave changes and a positive scintigram; and the fourth, new Q waves without a positive scintigram. Three further patients (3 percent) had Q waves and positive scintigrams postoperatively, but myocardial infarction was evolving before anesthesia and operation. Twenty-seven of 89 patients (30 percent) were found to have abnormal scintigrams preoperatively. In two patients, both operated upon with evolving myocardial infarction, the scintigram was worse postoperatively. In 13 patients the scintigram was improved after operation. In 12 patients (13 percent) the abnormal preoperative scintigram was unchanged after operation. Preoperative and postoperative myocardial scintigrams and ECG's must be compared to assess the incidence of operative myocardial infarction in patients undergoing CABG.

Adult↗
PubMed1978

Radionuclide imaging to assess myocardial damage during open heart surgery.

Technetium 99m Pyrophosphate imaging before and after open heart surgery was performed in 38 patients to estimate the incidence of peri-operative infarction. Positive images were present pre-operatively in 11 of 30 patients with coronary artery disease. In three patients the images changed from negative to positive and in two this was thought to be due to infarction produced at operation. The high incidence of positive pre-operative images emphasises that many patients with evolving myocardial infarction, unstable angina or severe heart failure are now operated upon without delay. Because many patients have positive images before surgery pre-operative and post-operative images must be compared to assess myocardial damage due to surgery.

Adult↗
PubMed1978

Surgical division of an accessory atrioventricular connection in the posterior septal region following ventricular fibrillation in the Wolff-Parkinson-White syndrome.

A young man presented with atrial fibrillation and a rapid ventricular response which degenerated into ventricular fibrillation. Electrophysiological study demonstrated an accessory atrioventricular connection in the posterior septal region. This was sectioned to prevent recurrence of his arrhythmia. Post-operative electrophysiological study demonstrated that the surgical section was successful.

Adolescent↗
PubMed1975

Surgical management of large bronchial collateral arteries with pulmonary stenosis or atresia.

Single or multiple large bronchial collateral arteries may provide all or some of the pulmonary arterial blood flow in patients with proximal atresia of the pulmonary artery, and even in patients with only pulmonary stenosis. At the time of corrective surgery such arteries must be ligated in order to provide favorable operating conditions, to avoid cardiac overdistention during repair, and to prevent left-to-right intrapulmonary shunting postoperatively. Their ligation and control require precise preoperative definition of their number, origin, and course, and special intraoperative methods for their exposure. Associated hypoplasia of the pulmonary arteries may be severe enough to preclude corrective operation, but these hypoplastic arteries may enlarge in response to increase of blood flow through them resulting from a surgically created shunt. Experience with 14 surgically managed cases of this type forms the basis for the report.

Adolescent↗
PubMedDate not supplied

Redistribution of vertical ground reaction force in dogs with experimentally induced chronic hindlimb lameness.

When lameness occurs in a load-bearing limb, compensatory load adjustments are made in the other supporting limbs. The vertical component of the ground reaction force, as measured by force platform analysis, reflects these adjustments. This study describes the pattern of vertical ground reaction force redistribution during experimental, chronic hindlimb lameness in dogs. The peak and impulse of the vertical ground reaction force were measured and described in 13 dogs before, and at 2, 6, and 12 weeks after transection of the cranial cruciate ligament. These variables were compared among limbs. The vertical ground reaction force in the forelimbs did not change significantly during the course of the study. At 2, 6, and 12 weeks after surgery, means of peak vertical force in the limb that underwent surgery were 18.9%, 44.0%, and 61.3% respectively, of presurgical values. In the contralateral limb, corresponding values were 131.7%, 112.8% and 112.9% respectively. If one accepts the relationship of mechanical loading to musculoskeletal architecture and the now certain relationship between lameness and compensatory loading of other limbs, then the use of another limb of the same animal as a control is a potential study design flaw.

Animals↗
PubMedDate not supplied

Low-field magnetic resonance imaging of early subchondral cyst-like lesions in induced cranial cruciate ligament deficient dogs.

Six healthy adult male mongrel dogs underwent cranial cruciate ligament transection in the left stifle. Survey radiography of both stifles and low-field (0.064 T) MRI of the left stifle were performed preoperatively and at 2, 6, and 12 weeks postoperatively. Focal changes in signal intensity were seen with MRI in the subchondral bone of the medial tibial condyle at 2 and 6 weeks postoperatively. At 12 weeks postoperative, a cyst-like lesion was detected using MRI in the subchondral bone of the medial tibial condyle in 4 of 6 dogs and a less defined lesion at this site in the remaining 2 dogs. The cyst-like lesion was spherical in shape and showed typical characteristics of fluid with low signal intensity on T1-weighted images, high signal intensity on T2-weighted images and high signal intensity on inversion recovery images. The lesion was seen in the subchondral bone of the caudal medial and/or middle region of the tibial plateau slightly cranial to the insertion of the caudal cruciate ligament. No subchondral cysts were seen in the tibia on radiographs. Histopathologically, the tibia was characterized by a loose myxomatous phase of early subchondral cyst formation.

Animals↗
PubMedDate not supplied

Low-field magnetic resonance imaging of the canine stifle joint: normal anatomy.

Low-field magnetic resonance imaging (MRI) was performed on the stifle joints of four normal adult mongrel dogs using a 0.064 Tesla scanner. Markers were placed on each stifle joint to serve as reference points for comparing gross sections with the images. A T1-weighted sequence was used to image one stifle joint on each dog in the sagittal plane and the other stifle joint in the dorsal plane. The dogs were euthanized immediately following MRI and the stifle joints frozen intact. Each stifle joint was then embedded in paraffin, again frozen, and sectioned using the markers as reference points. On T1-weighted images, synovial fluid had low signal intensity (dark) compared to the infrapatellar fat pad which had a high signal intensity (bright). Articular cartilage was visualized as an intermediate bright signal and was separated from trabecular bone by a dark line representing subchondral bone. Menisci, fibrous joint capsule, and ligamentous structures appeared dark. In the true sagittal plane, the entire caudal cruciate ligament was often seen within one image slice. The patella was visualized as an intermediate bright signal (trabecular bone) surrounded by a low intensity signal (cortical bone). The trochlea and the intercondylar notch were difficult areas to analyze due to signal volume averaging of the curved surface of these areas and the presence of several types of tissues.

Adipose Tissue↗
PubMedDate not supplied

Effect of hydration on signal intensity of gelatin phantoms using low-field magnetic resonance imaging: possible application in osteoarthritis.

Five gelatin phantoms were constructed to study the effect of matrical hydration on magnetic resonance imaging (MRI) signal intensity using a low-field strength imager. Water content of the phantoms ranged from 75 to 95% weight/weight. Signal intensity values of each phantom were measured using five imaging sequences: proton density, T1-weighted, T2-weighted, inversion recovery with short inversion time, and inversion recovery with long inversion time. There was significant positive correlation (p < .05) of signal intensity with differences in hydration using the T2-weighted sequence and the inversion recovery sequence with short inversion time. Significant negative correlations (p < .05) were found with T1-weighted imaging and the inversion recovery sequence with long inversion time. In a second part of the study, in vivo focal variations in MRI signal intensity were evaluated in a canine cranial cruciate ligament deficient model of osteoarthritis. Signal intensity measurements were obtained from multiple areas of articular cartilage to identify an initial stage in osteoarthritis that is characterized in part by increased hydration of articular cartilage. At 6 weeks post-transection of the cranial cruciate ligament, an increase in signal intensity was detected in the articular cartilage of the weight-bearing portion of the lateral femoral condyle and the caudal portion of the medial tibial condyle with T1-weighted imaging. The increase in signal intensity may reflect increased proteoglycan synthesis by chondrocytes that also occurs early in the pathogenesis of osteoarthritis.

Animals↗
PubMedDate not supplied

Low-field magnetic resonance imaging of the equine tarsus: normal anatomy.

The objective of this study was to define the normal gross anatomic appearance of the adult equine tarsus on a low-field magnetic resonance (MR) image. Six radiographically normal, adult, equine tarsal cadavers were utilized. Using a scanner with a 0.064 Tesla magnet, images were acquired in the sagittal, transverse and dorsal planes for T1-weighted and the sagittal plane for T2-weighted imaging sequences. Anatomic structures on the MR images were identified and compared with cryosections of the imaged limbs. Optimal image planes were identified for the evaluation of articular cartilage, subchondral bone, flexor and extensor tendons, tarsal ligaments, and synovial structures. MR images provide a thorough evaluation of the anatomic relationships of the structures of the equine tarsus.

Animals↗