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Biomedical subjects

W H O'Connor

Publications and source records attributed to W H O'Connor.

8 recordsLinked to original sources
PubMed1993

Atypical presentations and echocardiographic findings in patients with cardiac tamponade occurring early and late after cardiac surgery.

Cardiac tamponade, a potentially lethal complication following cardiac surgery, may present either early or late postoperatively and may be difficult to diagnose due to atypical clinical, hemodynamic, or echocardiographic findings. To determine the frequency and clinical features of postoperative cardiac tamponade, we performed a review of 510 consecutive patients who underwent cardiac surgery. The incidence of postoperative cardiac tamponade was 2.0 percent (10/510 patients) and occurred following valvular, bypass, and aortic surgery. Nine of ten patients had either atypical clinical, hemodynamic, and/or echocardiographic findings. The diagnosis of tamponade was made 1 to 30 days (mean = 8.5 days) postoperatively. Presenting symptoms were often mild and nonspecific. Classic signs including hypotension, pulsus paradoxus greater than 12 mm Hg, and elevated jugular venous pressure were present in 7, 6, and 5 patients, respectively. Right heart hemodynamics revealed elevated and equalized diastolic pressures in three of six patients. Two-dimensional echocardiography revealed selective compression of the left ventricle (LV) (four patients), right ventricle (RV) (one patient), left atrium (LA)/RV (one patient), LA/LV (one patient), LA/LV/RV (one patient), all four chambers (one patient), and no diastolic collapse of any chamber (one patient). There was often an absence of anterior pericardial fluid (six patients) with tethering of a portion of the RV to the chest wall anteriorly (five patients). Coagulation parameters were "supratherapeutic" in only three of eight patients who were receiving systemic anticoagulants at the time of diagnosis. The initial diagnosis was confused with congestive heart failure in one patient, pulmonary embolism in three patients, acute myocardial infarction in two patients, and sepsis in one patient. Eight of ten patients survived; all of these patients underwent surgical removal of fluid and/or hematoma in the operating room. We conclude that postoperative tamponade after cardiac surgery may have varied clinical and hemodynamic presentations, often due to selective chamber compression by loculated fluid or clot. Due to its frequently atypical features and presentation that may simulate other disorders, the diagnosis of tamponade should be considered whenever hemodynamic deterioration or signs of low output failure occur in the postcardiotomy patient.

Adult↗
PubMed1989

Pacemaker-mediated tachycardia from a single chamber temperature sensitive pacemaker.

This report describes a case of pacemaker-mediated tachycardia from a single chamber temperature sensitive rate modulated pacemaker. The patient experienced diaphragmatic pacing that produced an increase in right ventricular blood temperature. This temperature increase was sensed by the pacemaker and led to sustained upper rate limit pacing. Decreasing the ventricular output to prevent diaphragmatic capture eliminated further episodes of pacemaker-mediated tachycardia.

Blood↗
PubMed1971

The effect of diffusible acids on potassium ion uptake by yeast.

1. When yeast oxidizes ethanol at different pH values the uptake of K(+) corresponds closely to the amount of acetate accumulated at each pH value. 2. The addition of semicarbazide to the suspension buffered at pH4.75 inhibited both the K(+) uptake and the acetate accumulation by about 50%. 3. The addition of either acetate or propionate to the suspensions markedly increased the K(+) uptake. 4. The addition of acetate to the suspensions lowered the intracellular pH of the yeast from a resting value of pH5.80 to 5.56. 5. The ratio of the initial rate of K(+) uptake to O(2) consumption was 0.77. This ratio was increased to 1.77 in the presence of 10mmol of propionate/l.

Acetates↗
PubMedDate not supplied

Evaluation of the mechanisms of antiepileptic drug-related chronic leukopenia.

Antiepileptic drug (AED)-related chronic leukopenia [white blood cell (WBC) count < 4,000/microliters] is a dilemma, especially when the AED is effective in controlling seizures. We evaluated the possible mechanisms of leukopenia in 7 patients. Mean WBC count was 3,000/microliters with a mean of 42% polymorphonuclear leukocytes (PMN). The AEDs were carbamazepine (CBZ) alone in 1 patient or CBZ combined with phenytoin (PHT), primidone (PRM), phenobarbital (PB) and/or valproate (VPA) in 5 patients; one patient was receiving PHT only. Bone marrow (BM) aspirates and PMN antibody studies using chemiluminescence were normal. Two liver-spleen scans showed mild relative splenomegaly. After exercise, WBC count (n = 7) increased by 54% (SEM 12%), while the WBC counts in controls (n = 5) increased by 52 +/- 16%. Antinuclear antibodies (Hep-2) were absent in 6 patients and positive (1:160) in 1. PMN adhesion to nylon wool was decreased (54 +/- 10% in patients vs. 80 +/- 5% in controls: n = 13, p < 0.005). Our data, particularly the appropriate WBC response to the stress of exercise, and normal BM examinations suggest that continuation of AED therapy when leukopenia is stable and the percentage of PMN is normal is probably safe. Caution should be used if the absolute PMN count is consistently < 1,000/microliters. BM examinations need not be performed routinely for every patient with neutropenia due to AEDs, especially if the leukopenia fluctuates in the range of 2,000-4,000 cells/microliters.

Adult↗