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Biomedical subjects

F G Baumann

Publications and source records attributed to F G Baumann.

At least 73 records · Page 4Linked to original sources
PubMed1989

The value of silent myocardial ischemia monitoring in the prediction of perioperative myocardial infarction in patients undergoing peripheral vascular surgery.

Real-time electrocardiographic monitoring for silent myocardial ischemia was performed on 200 patients undergoing peripheral vascular surgery to try to better define those at high risk of perioperative myocardial infarction. The patients were divided into those undergoing abdominal aortic aneurysm or lower extremity revascularization procedures (group I, n = 120) and those undergoing carotid artery endarterectomy (group II, n = 80). Silent ischemia was detected during the preoperative, intraoperative, or post-operative periods in 60.8% of group I and 67.5% of group II patients. Six group I and three group II patients suffered an acute perioperative myocardial infarction with two cardiac deaths. In both groups I and II a variety of parameters based on monitoring of silent myocardial ischemia were compared between the subgroups of patients who had myocardial infarction and those who did not. The results show that in both groups there was a significantly (p less than or equal to 0.05) greater total duration of perioperative ischemic time, total number of perioperative ischemic episodes, and total duration of perioperative ischemic time as a percent of total monitoring time in patients who suffered a perioperative myocardial infarction compared to those who did not. Multivariate logistic regression analysis of preoperative characteristics in all 200 patients showed the occurrence of preoperative silent myocardial ischemia and angina at rest to be the only significant predictors of perioperative myocardial infarction. Thus perioperative monitoring for silent myocardial ischemia might noninvasively identify those patients undergoing peripheral vascular surgery who are at increased risk for perioperative myocardial infarction, permitting implementation of timely preventive measures in selected patients.

Aged↗
PubMed1989

Ten-year operative experience with 165 aneurysms of the ascending aorta and aortic arch.

Results of surgery in 165 patients with aneurysms of the ascending aorta and aortic arch during 1978-1988 were analyzed retrospectively. Etiology included 29% dissection, 22% atherosclerosis, 22% cystic-medial necrosis, and 27% other causes. Concomitant procedures on the aortic valve were performed in 65% of patients (valvular replacement in 37%, valve-conduit in 23%, and valvular resuspension in 5%), and 13% underwent concomitant coronary artery bypass surgery. Major changes in our operative technique for such aneurysms have been introduced during the last 5 years, especially use of a continuous suture-graft-inclusion technique in 99% of patients, use of circulatory arrest in 59%, and use of an open hemiarch repair in 32%. Hospital mortality dropped from 17.9% during the first 5 years of the study period to 12.3% in the last 5 years despite increasing complexity of the cases encountered. Operative mortality was 7.6% for ascending aortic aneurysmal repair; 5.3% for valve-conduit procedure; 8.8% for open hemiarch repair; and 30.8% for repair of extensive aneurysms involving the aortic arch and significant portions of the descending aorta. Multivariate analysis showed that, of the variables examined, significant predictors of increased operative risk were age (p less than 0.05) and extension of an ascending aortic aneurysm to the descending aorta or involvement of the aortic arch (p less than 0.001). The incidence of stroke was 2.4%, with only one stroke since 1983 despite more extensive use of circulatory arrest since that time. Follow-up was 94% complete, with a mean (+/- SD) follow-up interval of 28 +/- 24 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Epidural-evoked potentials: a more specific indicator of spinal cord ischemia.

The purpose of this experimental study was to examine the differences between peripheral nerve stimulation and direct spinal stimulation in generating cortical somatosensory-evoked potential (SEP) responses for monitoring spinal cord ischemia during thoracic aorta cross-clamping. Adult mongrel dogs (n = 6) were placed under general anesthesia and a left thoracotomy was performed. A conventional stimulating electrode was placed over the posterior tibial nerve (PN-SEP), and a special bipolar electrode was placed epidurally over the spinal cord at L1-2 (SC-SEP). The aorta was cross-clamped proximal to the left subclavian artery. Stimulations were alternately performed through both electrodes, and SEP responses were continuously monitored. The cross-clamp was released after one hour and the animal was observed for another hour prior to sacrifice. Excellent SEPs were obtained with six stimuli over 3 sec via the SC-SEP stimulus in contrast to the 200 stimulations over 90 sec required for the PN-SEP stimulus. Aortic cross-clamping resulted in a significantly longer mean time to loss of SEPs for SC-SEP (mean +/- SEM, 13.7 +/- 1.0 min for SC-SEP vs 11.3 +/- 0.7 min for PN-SEP, P less than 0.05). Likewise, unclamping of the aorta consistently resulted in a shorter mean time to return of SEPs for SC-SEP compared with PN-SEP. These data indicate that direct epidural stimulation for evoked cortical responses is a more sensitive means of determining the adequacy of posterior spinal cord blood flow as reflected by posterior spinal cord function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Current concepts of mitral valve reconstruction for mitral insufficiency.

In recent years, there has been a renewed interest in surgical reconstruction of the insufficient mitral valve because of reconfirmation of the limitations of existing prosthetic and bioprosthetic valves. A follow-up study, including late functional data, of 148 patients who underwent mitral valve reconstruction at our institution was combined with a review of the literature to assess the current status of mitral reconstruction. The results indicate that mitral reconstruction by Carpentier techniques is widely applicable, durable, and relatively free of complication. Freedom from late thromboembolic and anticoagulant complications is particularly notable. These factors could prove to justify earlier operative intervention in patients with mitral insufficiency before permanent myocardial damage evolves. As mitral valve reconstruction techniques become more familiar and widely used, mitral reconstruction may become the operative procedure of choice for mitral insufficiency, especially insufficiency due to degenerative disease.

Actuarial Analysis↗
PubMed1988

Percutaneous cardiopulmonary bypass limits myocardial injury from ischemic fibrillation and reperfusion.

Percutaneous implementation of cardiopulmonary bypass (PCPB) with a synchronous pulsatile pump has been shown to be an efficient means of unloading the heart. Therefore, this technique may provide a practical and effective method for treating patients undergoing a major cardiac catastrophe who are unresponsive to the usual resuscitative efforts. We tested whether PCPB could effectively unload the heart and provide myocardial salvage during left anterior descending (LAD) coronary artery occlusion complicated by ventricular fibrillation in the canine model (n = 13). All 13 dogs fibrillated within 20 minutes of LAD occlusion, and none could be successfully resuscitated by manual cardiac compression, sodium bicarbonate administration, antiarrhythmic agent administration, and electrical defibrillation. All 13 dogs were then placed on PCPB by way of the right jugular vein and right femoral artery; in seven, we used a synchronous pulsatile pump and in six a standard roller pump. No vent was placed in the left ventricle. All animals returned to normal sinus rhythm within 20 minutes of institution of PCPB. The LAD snare was released after 2 hours, and all animals were maintained on PCPB during 3 hours of reperfusion. At sacrifice, the area of infarction was determined by staining with triphenyltetrazolium chloride and was expressed as a percentage of the left ventricular area-at-risk for infarction. The tension time index was also measured and expressed as percent change from baseline. The left ventricular area-at-risk for infarction was similar in both groups (31.5% for roller pump vs. 29.2% for pulsatile pump; p greater than 0.05), but the area of infarction as a percentage of the area at risk was significantly smaller in the pulsatile-pump group (22.0%) than in the roller-pump group (35.4%; p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Long-term results of mitral valve reconstruction with Carpentier techniques in 148 patients with mitral insufficiency.

There have been few relatively complete follow-up studies of long-term mitral valve function after Carpentier-type surgical reconstruction. Between January 1980 and May 1986, 148 patients underwent Carpentier reconstruction for mitral valve disease (43% degenerative and 30% rheumatic). Operative mortality was 5.4% overall (1.2% for isolated mitral reconstruction), and follow-up (mean, 26 months) was completed for all survivors. Five-year survival from late cardiac death was 90.0%, as was 5-year freedom from postreconstruction mitral valve replacement. Postreconstruction mitral replacement was needed in eight patients, in only five for failure of repair. Follow-up echocardiographic studies on 83.2% (104 of 125) of eligible patients showed 92.3% were free of significant (3+ or 4+) mitral regurgitation. Freedom from mitral valve replacement or recurrent severe (4+) insufficiency was 84.4% at 5 years overall, but was lower for the rheumatic type of mitral disease than for the degenerative type (71.6% vs. 88.3%). At 5 years, 95.2% of patients were free from thromboembolism without the necessity for long-term warfarin (Coumadin) therapy. At follow-up, 95.3% of survivors had improved to New York Heart Association Class I or II. The functional durability of mitral reconstruction and consistently high level of freedom from late endocarditis and thromboembolic and anticoagulant complications support the value of the Carpentier method of mitral reconstruction for mitral insufficiency, especially insufficiency due to degenerative disease.

Adolescent↗
PubMed1987

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. I. Relationship of aortic cross-clamp duration, changes in somatosensory evoked potentials, and incidence of neurologic dysfunction.

To determine if intraoperative monitoring of somatosensory evoked potentials detects spinal cord ischemia, we subjected 21 dogs to aortic cross-clamping distal to the left subclavian artery. Group I animals (short-term studies, n = 6) demonstrated decay and loss of somatosensory evoked potentials at 8.5 +/- 1.1 minutes after aortic cross-clamping. During loss of somatosensory evoked potentials, significant decreases in spinal cord blood flow occurred in cord segments below T6. Significant reactive hyperemia occurred without normalization of somatosensory evoked potentials after reperfusion. Fifteen Group II animals (long-term studies) were studied to determine the relationship between duration of spinal cord ischemia (evoked potential loss) and subsequent incidence of paraplegia. Extension of aortic cross-clamping for 5 minutes after loss of somatosensory evoked potentials in six dogs resulted in no paraplegia (mean cross-clamp time 12.7 +/- 0.6 minutes). Prolongation of aortic cross-clamping for 10 minutes after evoked potential loss in nine dogs (mean cross-clamp time 17.6 +/- 0.6 minutes) resulted in a 67% (6/9) incidence of paraplegia 7 days postoperatively (p = 0.02 versus 10 minutes of aortic cross-clamping). These findings demonstrate that simple aortic cross-clamping uniformly results in spinal cord ischemia and that such ischemia is detectable by monitoring of somatosensory evoked potentials. Duration of ischemia, as measured by the time of evoked potential loss during the cross-clamp interval, is related to the incidence of postoperative neurologic injury.

Animals↗
PubMed1987

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. II. Use of somatosensory evoked potentials to assess adequacy of distal aortic bypass and perfusion after thoracic aortic cross-clamping.

Pulsatile left atrial-femoral artery bypass was instituted after aortic cross-clamping distal to the left subclavian artery in a canine experimental model to determine the relationship of distal aortic perfusion pressure with spinal cord blood flow and somatosensory evoked potentials. In six animals (Group I) distal aortic perfusion pressure was maintained at 100 mm Hg throughout a 1 hour interval of aortic cross-clamping. During this period, somatosensory evoked potentials and spinal cord blood flow (radioactive microspheres) showed no significant change from baseline. In six other dogs (Group II) distal aortic perfusion pressure was initially maintained at 100 mm Hg after aortic cross-clamping and then progressively decreased to 70, 40, and 25 mm Hg. Somatosensory evoked potentials and spinal cord blood flow were preserved at baseline levels for all distal perfusion pressures greater than 70 mm Hg. At 40 mm Hg, abnormalities in amplitude of the somatosensory evoked potentials were noted in all animals with progression to complete loss of evoked potential activity at lower perfusion pressures. Maintenance of adequate somatosensory spinal cord conduction after thoracic aortic cross-clamping is dependent on a critical level of distal aortic perfusion that can be accomplished by use of an adjunct such as pulsatile left atrial-femoral artery bypass. The critical level of distal aortic perfusion pressure to maintain normal somatosensory evoked potentials and spinal cord blood flow in this canine experimental study was 70 mm Hg or greater. Because inadequate distal aortic perfusion can be easily detected by monitoring of somatosensory evoked potentials, these techniques should prove helpful in evaluating the effectiveness of distal perfusion techniques during clinical aortic cross-clamping for procedures on the thoracoabdominal aorta.

Animals↗
PubMed1987

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. III. Intraoperative identification of vessels critical to spinal cord blood supply.

Somatosensory evoked potentials were used to locate intercostal arteries critical to spinal cord blood flow in nine dogs. To mimic a clinical situation, the proximal descending thoracic aorta (left subclavian artery to T7) was excluded with cross-clamps, and partial pulsatile left atrial-femoral artery bypass was instituted to maintain distal aortic pressure at 100 mm Hg. Progressively lower aortic segments were excluded (T7-10, T10-L1, L1-3, L3-6, L6-7) until loss of somatosensory evolved potentials occurred. Spinal cord blood flow measurements at the time of evoked potential loss revealed significant ischemia (p less than 0.02 versus baseline) in the excluded segment in seven animals but normal spinal cord blood flow in the remainder of the cord. Upon reperfusion, significant reactive hyperemia (p less than 0.02) was noted only in previously ischemic cord segments. Two animals exhibited no change in somatosensory evoked potentials or spinal cord blood flow despite exclusion of the entire thoracoabdominal aorta, presumably as a result of spinal collaterals. Loss of somatosensory evoked potentials despite adequate distal perfusion indicates that critical intercostal vessels have been excluded from systemic and bypass circulations. Use of evoked potential measurements in both experimental and clinical situations provides a means for assessing adequacy of spinal cord blood flow during cross-clamping and can alert the surgeon to the need for reimplantation of critical intercostal arteries during surgical resection of the thoracoabdominal aorta.

Animals↗
PubMed1987

The hemodynamics of beta-blockade in patients undergoing abdominal aortic aneurysm repair.

To assess the intraoperative and postoperative hemodynamic effects of beta-blockade and its benefits in limiting myocardial ischemia and infarction, a group of 32 patients scheduled for abdominal aortic aneurysm (AAA) surgery (group 1) was treated with oral metoprolol immediately before surgery and with intravenous metoprolol during the postoperative period. Mean age was 71 years, and mean ejection fraction was 56% (range 36% to 83%). Eight patients had a preoperative history of angina, 13 had a history of myocardial infarction, and five had electrocardiographic evidence of prior myocardial infarction. A group of 51 closely matched patients with AAA who did not receive metoprolol served as controls (group 2). In group 1, overall hemodynamic tolerance of metoprolol intraoperatively and postoperatively was good, and there was no incidence of congestive heart failure, hypotension, or asthma. Furthermore, in group 1 significant reduction of systolic blood pressure and heart rate was consistently noted at frequent intraoperative intervals and for 48 hr after surgery, with only a transient reduction of cardiac index. In group 1, only one patient (3%) suffered an acute myocardial infarction. In contrast, nine group 2 patients (18%; p less than .05) suffered perioperative myocardial infarction. Furthermore, only four (12.5%) group 1 patients developed significant cardiac arrhythmias as opposed to 29 group 2 patients (56.9%; p less than .001). These data demonstrate that beta-blockade with metoprolol is effective in controlling systolic blood pressure and heart rate both intraoperatively and postoperatively in patients undergoing repair of AAA and can significantly reduce the incidence of perioperative myocardial infarction and arrhythmias.

Aged↗
PubMed1987

A comparison of methods for limiting myocardial infarct expansion during acute reperfusion--primary role of unloading.

Current use of angioplasty, thrombolysis, and surgical techniques for prompt reperfusion of an acute myocardial infarction raises questions concerning the optimum reperfusion technique for maximum myocardial salvage. Alterations in the conditions of reperfusion and/or the composition of the initial reperfusate can exert a significant effect on the extent of myocardial salvage. In an effort to define an optimum reperfusion technique, we used 40 dogs in a series of experiments in which the left anterior descending coronary artery (LAD) was snared for 2 hr followed by reperfusion by one of five methods for 4 hr. In addition, in a control group(group I, n = 6) the LAD was occluded for 6 hr without any reperfusion. In group 2 (n = 12), simulating medical reperfusion, reperfusion was achieved by simply releasing the snare for 4 hr. Group 3 dogs (n = 6) were placed on pulsatile left atrial-femoral bypass throughout 4 hr of reperfusion. Group 4 dogs (n = 9) were placed on percutaneous, synchronized pulsatile cardiopulmonary bypass during reperfusion. The procedure in group 5 (n = 7) dogs simulated coronary artery bypass grafting with cardiopulmonary bypass and cold blood, low-Ca++ cardioplegia during reperfusion. Group 6 (n = 6) was treated similarly except that during reperfusion amino acid-enriched cardioplegia was administered by warm induction techniques. At the end of 4 hr of reperfusion, the left ventricular area of infarction was determined by triphenyltetrazolium chloride staining and expressed as a percentage of the left ventricular area at risk for infarction (area of infarction [AI]/area at risk [AR]).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Percutaneous cardiopulmonary bypass with a synchronous pulsatile pump combines effective unloading with ease of application.

Percutaneous total cardiopulmonary bypass offers the advantage of rapid, simple implementation without the need for thoracic incision and provides the ability to support both left and right ventricular failure as well as pulmonary insufficiency. Previous studies using roller pump percutaneous bypass were only partially successful because of the inability to effectively unload the left ventricle. In the present experiment we attempted to determine in a normal canine model whether use of synchronous pulsatile pumping for percutaneous bypass could overcome this problem. Fourteen dogs were placed on percutaneous bypass for 1 hour. A roller pump was used in seven and a synchronous pulsatile pump with an electrocardiogram triggering mechanism in the other seven. All animals were maintained on percutaneous bypass for 1 hour. In the pulsatile pump group there was a significantly greater percent decrease from baseline in tension-time index (-56.3% versus -19.1%, p less than 0.01) and in myocardial oxygen consumption (-45.8% versus +2.1%, p less than 0.05) and a significantly greater percent increase in the endocardial/epicardial blood flow ratio (27.6% versus -6.5%, p less than 0.01) than in the roller pump group. These results show that superior unloading can be achieved by percutaneous pulsatile bypass compared with percutaneous roller pump bypass. The findings suggest that percutaneous total cardiopulmonary bypass with a synchronous pulsatile pump offers a relatively simple but effective method for providing appropriate patients with temporary hemodynamic stability before cardiac catheterization or medical or surgical revascularization.

Animals↗
PubMed1986

The atherosclerotic ascending aorta and transverse arch: a new technique to prevent cerebral injury during bypass: experience with 13 patients.

Calcification of the ascending aorta and transverse arch significantly increases morbidity and may compromise the completeness of cardiac surgical procedures. Several stratagems have been suggested to reduce the risk, but for some patients this finding is still associated with a devastating outcome, irrespective of the technique employed. Thirteen patients (7 men and 6 women with a mean age of 66 years) with extensive calcification in the ascending aorta and transverse arch underwent cardiopulmonary bypass (CPB). The presence of calcification was known prior to CPB in 12 patients and noted after cross-clamping of the aorta in 1 patient. Special techniques for cannulation of the ascending aorta or arch were undertaken in 12 patients; 1 patient required groin cannulation. In 12 patients CPB with gradual core cooling to 18 degrees C was done, during which time no manipulation of the aorta was allowed. Circulatory arrest was then initiated for 3.5 to 12 minutes. The aorta was opened widely during this time to remove ulcerated plaques and friable debris, and to locate a safe place for aortic occlusion. All patients recovered without neurological complications. In 1 patient, in whom occipital lobe infarcts developed, calcification was discovered after the aorta had been cross-clamped and necessitated subsequent endarterectomy of the ascending aorta and transverse arch.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Experiences with 1643 porcine prosthetic valves in 1492 patients.

Sixteen hundred and forty-three porcine prosthetic values (1102 Carpentier-Edwards, 541 Hancock) were implanted in 1492 patients at New York University Medical Center between January 1976 and June 1983. The aortic valve alone was replaced in 786 patients (53%), mitral valve alone in 556 (37%), and multiple valves in 143 patients (9.6%). Concomitant coronary artery bypass was performed in 326 patients (22%). There were 116 deaths within 30 days of operation (7.8%). Follow-up (mean: 42 months) was completed in 94% of survivors and revealed that late survival from cardiac-related death was 87% at 5 years and 81% at 7 years, with no significant difference between the Carpentier-Edwards and Hancock patients. Late thromboembolic complications, however, were significantly more frequent in Hancock patients at all intervals from 1-7 years (p less than 0.05), whether in the aortic or mitral position. Patients with coronary artery disease who had concomitant coronary bypass showed a survival from late cardiac death that did not differ significantly from that of patients undergoing valve replacement alone. Before operation, 87% of patients were in New York Heart Association Class III or IV, but after operation 80% were in Class I or II. Late anticoagulant complications, endocarditis, and valve dysfunction were relatively rare. These results from a series of such size, duration, and representative numbers of two types of porcine bioprosthesis confirm excellent results with porcine prostheses in the first 4-5 years following operation.

Animals↗
PubMed1985

A survey of 77 major infectious complications of median sternotomy: a review of 7,949 consecutive operative procedures.

Sternal wound infections developed following 77 (0.97%) of 7,949 operative procedures involving median sternotomy at New York University Medical Center from 1976 to 1984. Risk factors associated with the development of a sternal wound infection included combined revascularization and valve replacement, early reexploration for bleeding, prolonged low cardiac output syndrome, and prolonged ventilatory support (greater than 24 hours). Concomitant infection at other sites with the same organism as cultured from the sternum was present in 42% of the patients. Thirty-seven patients (48%) were treated with radical debridement followed by closed antibiotic irrigation. In 31 other patients (40%), the wounds were debrided and left to heal by open granulation. Both initial treatments had equally high success rates (78.4% and 74.2%, respectively). However, the open granulation method resulted in a hospital stay that was an average of 10 days longer than the closed antibiotic irrigation method. Muscle flaps were used to expedite healing of open granulation in 9 patients. Analysis of the results of different treatment strategies revealed that if debridement was accomplished within 20 days of the initial cardiac procedure, 76% of the patients could be successfully treated with closed antibiotic irrigation. Conversely, if treatment was delayed for longer than 20 days, 81% of the patients were treated with open granulation (p less than 0.001). Also noted was an inverse relationship between the serum blood urea nitrogen (BUN) level and the success rate of initial treatment with closed antibiotic irrigation. Patients with a serum BUN level of less than 40 mg/dl at the time of debridement had a 90% success rate as opposed to a success rate of 38% when the BUN level was 40 mg/dl or greater. The data presented suggest the following conclusions. Early diagnosis is crucial to successful treatment of sternal wound infection. When diagnosis can be established within 20 days, 80% of infections can be eradicated by the simple approach of debridement and closed antibiotic irrigation. When diagnosis is delayed, however, prompt debridement followed by muscle flaps is the procedure of choice. Open granulation alone, while successful, unnecessarily prolongs the hospital course.

Adult↗
PubMed1985

Pulsatile flow.

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Blood Flow Velocity↗
PubMed1985

Adjunctive left ventricular unloading during myocardial reperfusion plays a major role in minimizing myocardial infarct size.

Although prompt institution of reperfusion following coronary artery occlusion has been shown to limit myocardial infarct size, significant "reperfusion injury" may result. We investigated in a canine model whether maintenance of the left ventricle in an unloaded state during the initial reperfusion period following acute myocardial ischemia would result in greater limitation of infarct size or modify the development of reperfusion injury. Group I (control, n = 6) underwent 6 hours of occlusion of the left anterior descending coronary artery without further intervention. In both Group II (n = 6) and Group III (n = 6), the snare was released after 2 hours and hearts were reperfused for 4 hours. In Group III only, the left ventricle was maintained in an unloaded state throughout the entire reperfusion interval via pulsatile left atrial-femoral artery bypass. The results showed that reperfusion of the left ventricle in an unloaded state resulted in significantly improved limitation of both infarct size (area of infarct/area at risk = 16.6% for Group III versus 72.0% for Group I and 55.4% for Group II, p less than 0.001) and area of microvascular damage (area of microvascular damage/area at risk = 4.8% for Group III versus 30.6% for Group II, p less than 0.001). These results indicate that although myocardial reperfusion of the type provided by thrombolysis and/or angioplasty techniques does result in limitation of infarct size when compared to no reperfusion, this limitation is not optimal unless the left ventricle is unloaded during the initial reperfusion period.

Animals↗