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Biomedical subjects

R A Ott

Publications and source records attributed to R A Ott.

53 records · Page 3Linked to original sources
PubMed1977

Light-regulated permeability of rhodopsin:egg phosphatidylcholine recombinant membranes.

Purified rhodopsin was incorporated into phospholipid bilayers of egg phosphatidylcholine to give recombinant membrane vesicles, which were examined by proton and phosphorus nuclear magnetic resonance spectroscopy. Increased rhodopsin content in the membranes appears to progressively inhibit the molecular motions of the methyl, methylene, and phosphate groups of the phospholipid molecules. This indicates that regions of the rhodopsin molecule interact in a manner that affects the phospholipids from the aqueous interface to the bilayer midline. In the dark, the recombinant vesicles were sealed to europium, manganese, or cobalt ions. Light exposure allowed rapid equilibration of Mn2+ and Co2+, and somewhat slower equilibration of Eu3+ across the membrane. Light changed the membrane permeability, and the gradient in chemical potential resulted in a net ion movement across the rhodopsin:phospholipid recombinant membrane. The results suggest rhodopsin is a transmembrane protein.

Cobalt↗
PubMed1977

A servo controlled transapical left ventricular to aortic assist device with implantable canulae.

A servo controlled transapical LV to aortic bypass system employing a roller pump was evaluated. The pump achieved complete LV decompression with reduction of LV pressure below systemic pressure. The servo control was responsive to LA pressure and allowed stable complete bypass during interventions designed to raise and lower LA pressure. A permanently implantable transapical LV cannula and aortic cannula without obturators was evaluated with and without anticoagulants. The teflon felt surface 'healed' rapidly and developed a multi-layered fibrous pseudointima. Anticoagulants appeared to avoid excessive thrombus formation at the cannula sites and embolization.

Animals↗
PubMed1977

The effect of left atrial-to-aortic assistance on infarct size.

Left atrial-to-aortic (La-A) assistance is effective in supporting the failing circulation. This study evaluated its effect in salvaging ischemic myocardium in both large and small infarct models. In a control group, good correlation was shown between measurements of infarct size by ST-segment mapping at 20 minutes, triphenyl tetrazolium chloride staining at 5 hours, and the distribution of radioactive microspheres (P less than 0.01). A servo controlled assist pump was used which controlled pump speed according to the left atrial pressure. This allowed greater degrees of bypass for prolonged periods with reduced risk of air embolism. La-A assistance reduced systolic left ventricular pressure, and reduced the pressure time index (P less than 0.05). La-A assistance did not reduce infarct size measured by ST-segment mapping in a large infarct model when instituted before occlusion or 20 minutes after occlusion. Triphenyl tetrazolium chloride staining, however, showed less severe and homogenous damage in the assisted group as compared to controls. Electron microscopy confirmed the patchy nature of the ischemia. In a small infarct model, La-A assistance reduced nST from 6.3 +/- 0.8 to 3.8 +/- 1.5 and ST from 4.9 +/- 0.6 to 2.7 +/- 0.9 (P less than 0.05). The endocardial to epicardial ratio in the ischemic area fell from 0.69 +/- 0.05 to 0.43 +/- 0.05 in the control group (P less than 0.05) and a similar fall occurred in the assisted groups. La-A assistance is thus effective in reducing myocardial ischemia in a small infarct model, but appears to be less effective in a large infarct model.

Animals↗
PubMedDate not supplied

Clinical choices for circulatory assist devices.

Approximately 1.0% of open heart surgery patients become unweanable from cardiac bypass during the surgical procedure. In addition, nearly 20% of patients accepted for cardiac transplantation die while waiting for a donor heart. Pulsatile pneumatic ventricular assist devices (VADs) provide a realistic solution to these dilemmas. Currently, there are five manufacturers who are competing for the major market share in the clinical use of these devices. Novacor, Thermetics, Thoratec, Symbion, and Abiomed all have competitive VAD systems. Because no one system is optimal for all patients, the limitations, similarities, and strengths of each system should be known to enhance the patient's outcome when using these devices. Successful use of VAD systems, either as a bridge to transplantation or to ventricular recovery, is best approached by adherence to strict patient selection. Once instituted, VAD management centers on detailed attention to anticoagulation and prompt diagnosis and treatment of various complications.

Blood Loss, Surgical↗
PubMedDate not supplied

Rapid recovery of octogenarians following coronary artery bypass grafting.

BACKGROUND: Rapid recovery protocols for coronary artery bypass grafting (CABG) have resulted in major decreases in postoperative hospital length of stay (LOS) when applied to younger patients undergoing elective procedures. However, the effectiveness of rapid recovery protocols when applied to octogenarians has not been thoroughly studied. METHODS: Thirty-seven consecutive octogenarians underwent isolated CABG utilizing cardiopulmonary bypass (CPB). A protocol emphasizing preoperative placement of the intra-aortic balloon pump, reduced CPB time, early extubation, perioperative steroids, thyroid hormone, and aggressive postoperative diuresis was used. RESULTS: The 30-day operative mortality for the entire series was 5.4%. Twenty-five patients (71%, group I) were discharged in < 10 days postoperatively (average LOS of 6.3 +/- 1.6 days), while ten patients (29%, group II) were discharged at 10 or more days postoperatively (average LOS of 20.3 +/- 8.0, p < 0.001). Patients in group II were found to have a higher incidence of obesity (50% vs 4%, p < 0.01), symptomatic peripheral vascular disease (60% vs 8%, p < 0.01), and preoperative ambulatory difficulties (50% vs 0%, p < 0.01). The incidence of complications was 31% for the entire series, with no differences between the groups. CONCLUSION: Octogenarians performed well under a rapid recovery protocol, with 71% being discharged in < 10 days postoperatively, while patients with obesity, symptomatic peripheral vascular disease, and ambulatory difficulties rehabilitated more slowly.

Aged↗
PubMedDate not supplied

Simplified Parsonnet risk scale identifies limits to early patient discharge.

BACKGROUND: Fast-track recovery after coronary artery bypass surgery has influenced patient care positively. Predicting patients who fall off track and require prolonged (> or =7 days) hospitalization remains uncertain. The Parsonnet risk assessment score is effective in predicting length of stay, but is limited by inaccurate subdivision of risk categories. We simplified the Parsonnet risk scale to better identify patients eligible for fast-track recovery. METHOD: The cases of 604 consecutive patients who underwent isolated coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) were reviewed retrospectively. A rapid recovery protocol emphasizing reduced CPB time, preoperative intra-aortic balloon pump (IABP) criteria, and atrial fibrillation prophylaxis was applied to all patients. The five original divisions of the Parsonnet risk scale were reduced to three risk categories: Low (0-10; Group A), Intermediate (11-20; Group B), High (> 20; Group C). Comparisons of progressive risk categories were analyzed to identify predictive factors associated with fast-track outcomes. RESULTS: The thirty-day operative mortality for the entire group was 3.6%. Three clinical features were identified that distinguished risk progression-female gender, reoperative CABG, and increased age. Additionally, the presence of diabetes (p < 0.05), congestive heart failure (p < 0.01), and peripheral vascular disease (p < 0.001) distinguished Groups A and B, while acute myocardial infarction (p < 0.05) influenced outcomes in Group C. Group A (48%) mean risk score 5.9+/-3.2 was compared to Group B (34%) 14.8+/-2.6, which was further compared to Group C (18%) 26.4+/-2.8. The mean length of stay for Group A (5.3+/-4.1 days) was notably less than Group B (6.1+/-4.7 days; p < 0.05); however, both groups responded favorably to fast-track techniques. Group C did not respond comparably (9.2+/-9.2 vs 6.1+/-4.7 days; p < 0.001) and experienced prolonged recovery. The simplified Parsonnet risk scale did not identify differences in operative mortality and revealed only pneumonia (p < 0.05) and atrial fibrillation (p < 0.01) to be greater in Group C. As risk increased, significantly less revascularization was performed (Group A 3.6+/-1.2 grafts/patient vs Group B 3.3+/-1.2 [p < 0.01]; Group B 3.3+/-1.2 vs Group C 2.5+/-1.0 [p < 0.001]). CONCLUSION: A simplified Parsonnet risk scale (three categories) is an effective tool in identifying factors limiting fast-track recovery. Low- and intermediate-risk patients represent the majority (82%) and respond well to fast-track methods. High-risk patients (18%) are limited by a greater percentage of female patients, reoperative CABG, and the very elderly, resulting in fast-track failure. Strategies to improve recovery in high-risk patients may include evolving off-pump techniques.

Aged↗
PubMedDate not supplied

Reduced postoperative atrial fibrillation using multidrug prophylaxis.

BACKGROUND: Atrial fibrillation (AFIB) is the most common complication following coronary artery bypass grafting (CABG). Despite three decades of recognition, efforts to reduce the high incidence reported (15%-30%) have been largely unsuccessful. Reasons for postoperative AFIB are likely multifactorial. As a result, we defined a multidrug prophylaxis based on agents known to be individually effective. This method was applied prospectively to a series of consecutive CABG patients with the goal of reducing the incidence of new-onset postoperative AFIB. METHODS: Isolated CABG with cardiopulmonary bypass was performed on 517 consecutive patients. A rapid recovery protocol emphasizing AFIB multidrug prophylaxis was applied to all patients. All patients received 10 microg of triiodothyronine intraoperatively when the clamp on the aorta was released. Immediately following CABG, parenteral magnesium was administered to assure a serum magnesium > 2.2 mEq/dL. Thyroxine 200 microg was administered parenterally to all patients on postoperative days 1 and 2. Metoprolol (25 mg to 100 mg/day) was begun on all patients after extubation provided: heart rate > 85 beats/min and systolic blood pressure > 130 mmHg. Parenteral procainamide (12 mg/kg) loading dose, followed by a maintenance dose (2 mg/min), was used for patients who developed premature atrial contractions (> 1/min), nonsustained supraventricular tachycardia, or any episodes of atrial fibrillation. All patients also received postoperative digitalization, steroids, and aggressive diuresis. RESULTS: The 30-day operative mortality was 3.7%. The overall incidence of new-onset postoperative AFIB was 10.3% (53 patients). There was no major difference in operative mortality (7.5% vs 3.2%, p = 0.23), Parsonnet risk score, or intraoperative variables between AFIB patients and the non-AFIB patients. Patients presenting with a preoperative acute myocardial infarction (p < 0.05), left main stenosis > or = 70% (p < 0.01), and advanced age > or = 70 years (p < 0.05) were at increased risk of developing AFIB. The length of stay for patients with AFIB was 9.9 +/- 9.6 days versus 5.9 +/- 5.2 days (p < 0.001). CONCLUSION: Application of a multidrug prophylaxis can reduce postoperative AFIB to a low incidence. Identification of associated clinical features can help predict patients at risk for postoperative AFIB. Additional strategies to target postoperative AFIB may include treatment at the earliest recognition of atrial rhythm instability.

Aged↗
PubMedDate not supplied

A simple method to avoid thrombus formation at the de-airing port of the acute ventricular assist device.

De-airing of the acute ventricular assist device using the designed port has resulted in thrombus formation at the site of device puncture in three of four ventricular assist devices in place during long-term (more than 72 hours) support. Disruption of the inner biomer coating by blunt needle insertion for de-airing of the prosthetic ventricle is the apparent underlying cause. Because of the obvious hazard of subsequent embolization, we describe a simple and effective method of de-airing the acute ventricular assist device with use of a jejunostomy kit.

Enteral Nutrition↗
PubMedDate not supplied

Successful treatment of acute allograft failure using pneumatic biventricular assistance.

A 61-year-old man underwent orthotopic heart transplantation complicated by acute allograft failure. Management entailed placement of two ventricular assist devices, and there was subsequent hemodynamic stabilization. Ventricular assistance continued for 8 days, at which time graft recovery resulted in successful explanation of the devices. Subsequent recovery was uneventful, and the patient was discharged on the 28th postoperative day. Methods of optimizing interoperative device cardiac output and synchronous-mode weaning are discussed.

Cardiomyopathy, Dilated↗
PubMedDate not supplied

ECMO assisted angioplasty for cardiomyopathy patients with unstable angina.

Patients who are otherwise unsuitable candidates for coronary bypass surgery or standard coronary angioplasty (PTCA) may be successfully treated with PTCA during ECMO. Five patients (3 men, 2 women), with a mean age of 57 years, are reported on here. They were not considered good candidates for standard therapy because of poor left ventricular function (mean EF, 24; range, 16 to 28%). Patients were supported by percutaneous femoral bypass using a BARD CPS machine, and underwent successful PTCA of either two vessels (three patients) or three vessels (two patients); in addition, one patient had dilatation of a stenotic aortic valve. Patients were supported with ECMO for 26 to 140 (mean 104) minutes, and required transfusion with 0 to 4 (mean 2) units of blood during or after the procedure. Complications included groin hematoma in two patients. All were discharged within 4 days of the procedure. Follow-up of the patients has been completed (4-7 mo) with no further hospitalizations for unstable angina. All patients remain in NYHA Class II or III. These data suggest that ECMO-assisted angioplasty is a safe and effective method of palliation of unstable angina associated with cardiomyopathy.

Adult↗
PubMedDate not supplied

Surgical approach to combined coronary revascularization and abdominal aortic aneurysmectomy.

Combined repair of peripheral vascular disease and myocardial revascularization has become accepted treatment in selected patients. Two of our patients underwent such a procedure. One patient suffered an intraoperative dissection of the ascending aorta following myocardial revascularization. Ascending aortic replacement and vein graft reimplantation was accomplished as well as repair of the abdominal aortic aneurysm. Because of this experience we recommend that following myocardial revascularization, aortic cannulation be maintained during repair of the abdominal aortic aneurysm. This allows immediate access to cardiopulmonary bypass should untoward cardiovascular events occur during aneurysm repair.

Aged↗
PubMedDate not supplied

Hepatic trauma during cardiac surgery.

Two patients undergoing routine cardiac surgical procedures developed hypovolemic shock following cardiopulmonary bypass. They were found to have hemoperitoneum due to liver injuries. In the first case, intraabdominal hemorrhage was not diagnosed soon enough to save the patient. In the second case, immediate abdominal exploration led to prompt repair of the injury and resuscitation of the patient. We suggest that unexplained hypovolemic shock following cardiopulmonary bypass should be evaluated by immediate abdominal exploration to rule out hemoperitoneum.

Cardiac Surgical Procedures↗
PubMedDate not supplied

Concepts in the application of pneumatic ventricular assist devices for ischemic myocardial injury.

The clinical results of "bridge-to-recovery" from ischemic myocardial injury using pneumatic ventricular assist devices (VADs) have been disappointing, because no significant improvement in the hospital discharge rate (25%) has been observed during the past 10 years. Interestingly, similar results have been reported using the less sophisticated and more widely available centrifugal pumps. It is well recognized that appropriate patient selection and early device implantation are important determinants of patient survival; however, it is less clear why there is a lack of difference in the results between pneumatic VADs and the centrifugal pumps. The reasons for the lack of difference in the results between pneumatic VADs and centrifugal pumps are multifactorial, and to some extent may be due to a conservative approach in the application of the more capable pneumatic VADs. In an effort to provide a more effective approach to the clinical application of pneumatic VADs for bridge-to-recovery, two pneumatic devices (the Jarvik 7-70 total artificial heart and the Symbion acute VAD) were functionally characterized using an in vitro mock circulatory system. The performance under pneumatic VAD asynchronous pumping compared to electrocardiogram synchronous counterpulsation was also evaluated. Based upon the results obtained, a two phase approach was developed. In the initial phase (i.e., the first 12-48 hrs), device output is maximized through asynchronous pumping to rapidly reverse the effects of cardiogenic shock. During the second phase (i.e., after hemodynamic stabilization and early evidence of end-organ recovery), electrocardiogram synchronous counterpulsation is used to focus more specifically on recovery of the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗