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Biomedical subjects

O W Isom

Publications and source records attributed to O W Isom.

At least 19 recordsLinked to original sources
PubMed1992

Effects of temperature and flow rate on regional blood flow and metabolism during cardiopulmonary bypass.

Eleven dogs were subjected to a 150-minute period of cardiopulmonary bypass that consisted of a high-flow, normothermic phase, a high-flow, hypothermic phase, a low-flow, hypothermic phase, and then a high-flow, rewarming phase. Regional blood flow and oxygen consumption to the brain, intestines, kidney, and hind limb were determined at baseline and at 10-minute intervals during cardiopulmonary bypass. Blood flow to the carotid artery, superior mesenteric artery, and renal artery declined significantly with hypothermic cardiopulmonary bypass whereas blood flow to the femoral artery increased significantly. Although total body oxygen consumption returned to baseline values at the end of the rewarming phase, oxygen consumption for these regions differed somewhat from their baseline values. We conclude that blood flow during hypothermic cardiopulmonary bypass is shunted to skeletal muscle, particularly with high pump flows. Additionally, the return of total body oxygen consumption to baseline after rewarming is not necessarily reflected at the regional level.

Animals↗
PubMed1992

Evaluation of an extraaortic counterpulsation device in severe cardiac failure.

A valveless, single-orifice polyurethane ventricle with a maximum stroke volume of 60 mL was implanted on the brachiocephalic artery just above the aortic arch in sheep (n = 14) to act as an extraaortic counterpulsation device. In parallel, an intraaortic balloon was placed in the descending thoracic aorta. Both devices were pneumatically driven with an intraaortic balloon pump console that was gated by the electrocardiogram to provide aortic diastolic augmentation at a stroke volume of 40 mL. To compare the efficacy of counterpulsation for each device during severe cardiac failure, biventricular block was induced by continuous infusion of esmolol (100 to 600 micrograms.kg-1.min-1), titrated to reduce aortic flow and pressure to less than 75% of baseline. Pulsatile coronary and aortic flows were recorded with ultrasonic flow probes placed around their respective vessels. Aortic root and left ventricular pressures were recorded using micromanometers. The enhancement of hemodynamic variables for both devices were compared for optimal timing conditions, which were defined as inflation set just before the dicrotic notch and deflation bordering on isovolumetric systole. The extraaortic counterpulsation device was able to significantly augment aortic and coronary flows while simultaneously decreasing left ventricular tension time index and aortic end-diastolic pressure (p less than 0.02). The intraarotic balloon pump was able to significantly reduce only tension time index (p less than 0.002) to a lesser extent that the extraaortic counterpulsation device. All analysis was performed with the paired-samples t test. The extraaortic counterpulsation device greatly improves the myocardial oxygen supply-consumption ratio of the left ventricle by increasing diastolic coronary flow and reducing left ventricular wall tension during systole.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of shaving methods and intraoperative irrigation on suppurative mediastinitis after bypass operations.

To investigate the effects of the hair removal methods and intraoperative irrigation on suppurative mediastinitis after cardiopulmonary bypass operations, 1,980 consecutive adult patients over a 2-year period in our institution were prospectively randomized to manual shaving versus electrical clipping of hair before the skin incision, and to povidone-iodine solution (0.5%) versus saline solution mediastinal and subcutaneous irrigation before wound closure. The overall incidence of suppurative mediastinitis was 0.86% (17/1,980). The infectious rate was significantly higher in the manually shaven (13/990) than in the electrically clipped patients (4/990) with an odds ratio of 3.25 (95% confidence interval, 1.11 to 9.32; p = 0.024). It was also higher in the povidone-iodine group (11/990) than in the saline group (6/990), although the difference was not statistically significant (p = 0.16). Fourteen patients were treated with operative debridement with closed tube irrigation, with one failure requiring a conversion to an open wound. Two patients were successfully treated with primary open wound procedures followed by delayed muscular flap closures, and 1 patient succumbed to rapid and profound sepsis soon after open drainage. We conclude that electrical clipping is superior to manual shaving in the prevention of suppurative mediastinitis. The routine use of povidone-iodine (0.5%) irrigation was of no benefit in this study and may increase the incidence of infection due to its known suppressive effects on local leukocytes and fibroblasts. Furthermore, operative debridement with closed tube irrigation was successful in treating the majority of cases in this series.

Cardiopulmonary Bypass↗
PubMed1992

Survival analysis of octogenarian patients with coronary artery disease managed by elective coronary artery bypass surgery versus conventional medical treatment.

BACKGROUND: In view of the increasing age of the U.S. population, the use of coronary artery bypass surgery in the management of the elderly patients with coronary artery disease needs to be better defined. METHODS AND RESULTS: To evaluate the effects of medical and surgical therapy on octogenarian patients with coronary artery disease in our institution, we retrospectively reviewed 177 consecutive octogenarians who underwent cardiac catheterization over a 5-year period. Sixty-five of these patients were found to have significant coronary artery disease without severe valvular disease. Elective coronary artery bypass surgery was performed in 36 patients, whereas 29 patients were continued on maximization of medical therapy and not referred to the surgical service. Left ventricular ejection fractions (LVEF) were similar for the two groups, whereas the surgical patients had slightly higher average number of diseased coronary vessels and slightly higher levels of angina. Univariate survival analysis of 20 variables, including the choice of medical versus surgical treatment and the associated conditions, was performed by Mantel-Cox testing of the paired Kaplan-Meier product limit survival curves stratified by the subgroups of each variable. The variables found to be significant were then included in a multivariate survival analysis using the Cox proportional hazards regression model. The treatment choice, LVEF, level of angina, and presence of any aortic and/or mitral valvular disease at the time of cardiac catheterization were found to be independent prognostic indicators of survival in the follow-up period of 26 +/- 16 months. The 3-year probability of survival rates for the surgical patients and medical patients were 77.4% and 55.2%, respectively (p = 0.0294). The New York Heart Association functional class of the surgical group decreased significantly from a mean preoperative level of 3.4 +/- 0.5 to a mean level of 1.2 +/- 0.6 at the follow-up interview (p < 0.01), whereas it did not significantly change for the medical group from a baseline mean level of 2.8 +/- 1.3 to a mean follow-up level of 2.5 +/- 1.0. CONCLUSIONS: We conclude that coronary artery bypass surgery provided improved long-term survival and functional benefit compared with conventional medical treatment in a small group of octogenarian patients in our institution.

Aged↗
PubMed1992

Compositional analysis of a modified University of Wisconsin solution for extended myocardial preservation. A study of the left ventricular pressure-volume relation.

BACKGROUND: The University of Wisconsin solution (UW) has been shown to be superior to the use of traditional types of simple crystalloids in extended heart preservation. This study was designed to determine the necessity of four potentially redundant components in UW. MATERIALS AND METHODS: Forty canine hearts (n = 8 in each group) were preserved for 6 hours under hypothermic (1-2 degrees C), nonperfused conditions in unmodified UW, UW with an extracellular or reversed composition of sodium and potassium (UW-E), UW with chloride instead of lactobionate (UW-L), UW without raffinose (UW-R), and UW without hydroxyethyl starch (UW-HS). The left ventricular functions were assessed in an isolated heart preparation equipped with a computerized servo-volume pump to measure the pressure-volume relation. The systolic function was expressed in elastance derived from the end-systolic pressure-volume relation, and total ventricular performance was expressed in preload recruitable stroke work area derived from the stroke work-end-diastolic volume relation. Diastolic compliance was derived from the end-diastolic pressure-volume pressure relation. The results were compared with a control group with no ischemia. There was no significant deterioration in left ventricular systolic contractile functions as demonstrated by the analysis of elastance and the preload recruitable stroke work area in any of the modifications of UW. However, significant deterioration in the diastolic compliance occurred in the UW-E and UW-HS groups. A similar trend was found in the UW-L group, although it was not statistically significant, whereas the diastolic compliance was preserved in the UW-R group. CONCLUSIONS: The intracellular electrolyte composition and the hydroxyethyl starch are important in the preservation of left ventricular diastolic function, whereas the omission of raffinose was inconsequential. The replacement of lactobionate by chloride had less untoward functional effects compared with studies of other solid organ preservation.

Adenosine↗
PubMed1992

Superiority of the University of Wisconsin solution over simple crystalloid for extended heart preservation. A study of left ventricular pressure-volume relationship.

To compare the effects of the University of Wisconsin solution with those of an extracellular crystalloid solution, Krebs-Ringer bicarbonate, as cardiac preservation media, we studied 35 adult dogs in an isolated heart preparation. Four groups of seven hearts were preserved in University of Wisconsin solution for 6 or 12 hours or in Krebs-Ringer bicarbonate solution for 6 or 12 hours. An additional group of seven hearts with no ischemia was used for a control group. In the four preservation groups, hearts were arrested by electrolyte solution (Normosol with potassium chloride, 20 mEq/L, added, 4 degrees C), flushed with 200 ml of the preservation solution, and then stored in the same solution at 1 degree to 2 degrees C. The hearts were mounted on an isolated heart preparation equipped with a computer-controlled servo-pump system that used a mock arterial system to modulate the aortic input impedance presented to the left ventricle. Left ventricular pressure-volume loops were measured on-line for 2 hours of reperfusion with autologous warm oxygenated blood. Elastance was derived from the end-systolic pressure-volume relationship, and diastolic compliance was derived from the end-diastolic pressure-volume relationship. The total left ventricular performance was assessed by the preload recruitable stroke work area, the slope, and its x-intercept, all of which derived from the stroke work (pressure-volume area)-end-diastolic volume relationship. Extended global ischemia had more deleterious effects on the end-diastolic than the end-systolic pressure-volume relationship. In confirmation with other studies, elastance did not accurately reflect the level of ventricular contractile dysfunction because of the significant amount of diastolic dysfunction. The preservation of myocardial systolic and diastolic functions, as demonstrated by the preload recruitable stroke work area and diastolic compliance, was better in the University of Wisconsin solution groups than in the Krebs-Ringer bicarbonate solution groups after 6 and 12 hours of preservation. In addition, 6 hours of preservation with University of Wisconsin solution maintained normal systolic and diastolic functions as compared with those of the control group. Preservation with University of Wisconsin solution prevented any myocardial edema formation; by contrast, this was significantly increased after 12 hours in Krebs-Ringer bicarbonate solution. Groups preserved with University of Wisconsin solution had less reperfusion injury as evidenced by the release of coronary sinus creatine kinase during reperfusion; they also had improved oxygen use during reperfusion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMed1991

Isolated coronary artery bypass grafting in one hundred consecutive octogenarian patients. A multivariate analysis.

One hundred consecutive patients aged 80 or older underwent isolated coronary artery bypass grafting for New York Heart Association functional class III (24%) or IV (76%) disease in our institution from 1985 to 1989. The operations were elective in 36 patients, urgent in 52, and emergent in 12. Twenty-eight patients had significant disease of the left main coronary artery, with the remainder having an average of 2.8 diseased coronary vessels. Preoperative left ventricular ejection fraction was considered good (greater than 50%) in 62 patients, fair (30% to 50%) in 24 patients, and poor (less than 30%) in 14 patients. An average of 2.8 grafts were performed per patient, and the internal mammary artery was used in 10 patients. Univariate analysis of 36 perioperative factors followed by multivariate logistic regression analysis of the significant variables (p less than 0.05) revealed that the urgency of the operation and left ventricular ejection fraction were independent predictors of operative mortality. There were 12 in-hospital deaths, and the mortality was significantly lower in the elective cases (2.8%) than in the urgent (13.5%) and emergent cases (33.3%). Major complications occurred in 14% of the elective cases, in 21% of the urgent cases, and in 67% of the emergent cases. The operative mortality rates for good, fair, and poor left ventricular ejection fraction were 4.9%, 12.5%, and 42.9%, respectively. Long-term follow-up averaging 22 months revealed a 77% actuarial probability of survival at 24 months and 51% at 48 months, with only two cardiac-related deaths. We conclude that coronary artery bypass grafting can be performed in octogenarians with a favorable outcome when done electively in patients with normal to moderately depressed left ventricular function.

Aged↗
PubMed1991

Myocardial reperfusion injury. Platelet-activating factor stimulates polymorphonuclear leukocyte hydrogen peroxide production during myocardial reperfusion.

To study the roles of platelet-activating factor, polymorphonuclear leukocytes, and oxygen free radicals in myocardial reperfusion injury, we subjected 10 sheep to 90 minutes of mid-left anterior descending coronary artery followed by 6 hours of reperfusion. Stainings with gentian violet and tetratriphenyl ammonium chloride demonstrated 20% +/- 3% of the left ventricular mass at risk for ischemia, of which 75% +/- 10% underwent infarction. Coronary sinus blood was assayed for platelet-activating factor and neutrophil hydrogen peroxide production before and during coronary occlusion and during reperfusion. Platelet-activating factor was isolated by column chromatography and lipid extraction and quantified by radioimmunoassay. Neutrophil hydrogen peroxide production was measured by a 2',7'-dichlorofluorescein flow-cytometric assay. Platelet-activating factor was elevated to 899 +/- 210 pg/ml at 15 minutes of reperfusion, compared with the preocclusion level of 271 +/- 55 pg/ml and coronary occlusion level of 359 +/- 64 pg/ml (p less than 0.05; analysis of variance). Neutrophil hydrogen peroxide production, measured on a relative fluorescence scale, was also elevated to a level of 141 +/- 27 at 1 hour of reperfusion, compared with the preocclusion level of 103 +/- 6 and the coronary occlusion level of 114 +/- 13 (p less than 0.01; analysis of variance). Both of these parameters returned toward baselines at the end of 6 hours of reperfusion. Histologic examination revealed infiltration of polymorphonuclear leukocytes into the interstitium of the reperfused myocardium. Neutrophils isolated from unoperated and healthy sheep demonstrated a graded dose response in hydrogen peroxide production when stimulated by purified platelet-activating factor in vitro. These findings suggest that platelet-activating factor is released in the coronary circulation and is a mediator of oxygen free radical production in polymorphonuclear leukocytes during myocardial reperfusion.

Animals↗
PubMed1990

Treatment with desmopressin acetate in routine coronary artery bypass surgery to improve postoperative hemostasis.

Desmopressin acetate (DDAVP) has been shown to decrease blood loss and transfusions in complex cardiac operations with long extracorporeal times. Its use in routine cardiac valve operations has been shown not to be beneficial, but its role in routine coronary artery bypass grafting operations has not been defined. We examined the effect of DDAVP in a prospective study of 60 patients undergoing uncomplicated primary coronary artery bypass grafting operations. Thirty consecutive patients received DDAVP (0.3 micrograms/kg) after cardiopulmonary bypass and were compared with 30 consecutive patients who did not receive DDAVP. No significant differences were seen in 12-hour mediastinal blood loss (465 +/- 207 ml with DDAVP versus 511 +/- 221 ml without DDAVP) or 12-24-hour mediastinal blood loss (236 +/- 127 ml with DDAVP versus 260 +/- 112 ml without DDAVP). Transfusion of blood products were similar for both groups. Platelet aggregometry at intraoperative and postoperative time points using ADP, collagen, and ristocetin was not significantly different from baseline values in either group. In a subgroup of patients with poor initial ristocetin-induced platelet aggregometry, a significant increase (p less than 0.05) in ristocetin-induced platelet aggregometry was seen postoperatively only in those patients who had received DDAVP. A decrease in blood loss and transfusions, however, was not demonstrable. In those patients who had been on aspirin or nonsteroidal anti-inflammatory drugs preoperatively, DDAVP did not improve mediastinal blood loss or transfusion needs.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1989

Reversal of left ventricular dilatation, hypertrophy, and dysfunction by valve replacement in aortic regurgitation.

Although aortic valve replacement for aortic regurgitation relieves left ventricular volume overload, ventricular geometry does not consistently normalize. To assess the extent, determinants, and functional consequences of reversal of left ventricular dilatation and hypertrophy, 38 patients with severe aortic regurgitation were studied pre- and postoperatively by serial echocardiography and radionuclide cineangiography. Left ventricular end-diastolic dimension normalized in 58% of patients by 9 +/- 6 months postoperatively, at which time 50% of patients had normalized mass; cumulative normalization rose to 66% for end-diastolic dimension and 68% for left ventricular mass during further follow-up. All patients who had normalized end-diastolic dimension also had normal postoperative ejection fractions (mean 61 +/- 8%). In contrast, patients in whom the left ventricle remained dilated had a 42% prevalence of subnormal postoperative left ventricular ejection fraction. Preoperative left ventricular end-systolic dimension less than or equal to 55 mm identified 86% of patients in whom end-diastolic dimension normalized, whereas end-systolic dimension exceeded 55 mm in 81% of those with persistent dilatation; other proposed preoperative predictors of operative outcome correctly identified lower proportions (from 59% to 71%) of patients in whom left ventricular size did or did not normalize. In conclusion, aortic valve replacement resulted in normalized left ventricular chamber size and mass in two thirds of the patients selected for operation by current criteria; favorable geometric outcome is associated with persistence or recovery of normal left ventricular function.

Aortic Valve↗
PubMed1989

Safety of metallic surgical clips in patients undergoing high-field-strength magnetic resonance imaging.

Use of metallic clips with ferromagnetic properties in patients undergoing a large variety of surgical procedures, and in particular, in coronary artery and other vascular reconstructions, has become increasingly popular. The safety of these commonly used surgical clips when subjected to high-intensity diagnostic magnetic resonance imaging fields is still debated. Commonly used hemostatic metallic clips manufactured by the Weck and US Surgical Corporations were tested in an in vitro system to assess their safety with regard to migration and displacement. The two tested hemostatic metallic clips proved safe and did not migrate or become dislodged when they underwent magnetic resonance imaging scans. This is in direct contrast to multiple cerebral aneurysm clips, also tested, which have highly ferromagnetic properties and were previously shown to migrate with disastrous results in patients undergoing diagnostic magnetic resonance imaging scans. This study supports the continued widespread use of small metallic hemostatic clips in the myriad of procedures in which they are presently used and illustrates the need for methods of evaluating such devices before they are clinically implanted.

Electromagnetic Fields↗
PubMed1988

Acute purulent mediastinitis and sternal osteomyelitis after closed chest cardiopulmonary resuscitation: a case report and review of the literature.

Numerous complications have been associated with cardiopulmonary resuscitation. Acute purulent staphylococcal mediastinitis and sternal osteomyelitis are, however, unusual and do not appear to have been reported previously in association with closed chest resuscitation. Sternal fracture during chest compressions and subsequent hematogenous seeding of the resultant retrosternal hematoma with Staphylococcus aureus led to purulent mediastinitis and sternal osteomyelitis in our patient. The source of bacteremia may have been a resolving phlebitis at an intravenous catheter insertion site. Early diagnosis, aggressive surgical debridement, and antibiotic therapy were key to a successful outcome.

Acute Disease↗
PubMed1987

Intra-abdominal complications of cardiopulmonary bypass operations.

The records of 6,452 consecutive patients who underwent cardiopulmonary bypass procedures were examined for intra-abdominal complications. There were 60 complications in 51 patients for an incidence of 0.94 per cent. The mortality rate was 59 per cent. Complications included bleeding in the gastrointestinal tract in 20, intestinal ischemia in 16, acute cholecystitis in 11, pancreatitis in five, small intestinal obstruction in three, perforated ulcer in two, hepatic necrosis in two and splenic laceration in one instance. Clinical risk factors included advanced age, emergency operation, valvular surgical treatment, hypotension, intra-aortic balloon pump, pressors and reoperation. Patients with a prolonged pump time had an increased risk of intraabdominal complications (p less than 0.001).

Acute Disease↗
PubMed1979

Angina following myocardial revascularization. Does time of recurrence predict etiology and influence results of operation?

To assess the operative mortality and long-term results in patients undergoing repeat revascularization for recurrent angina, we analyzed 48 consecutive patients operated upon at New York University Medical Center between 1970 and 1978. Between January, 1970, and July, 1973, 15 patients underwent repeat revascularization with five operative deaths (33 percent). Thirty-three patients underwent similar operations from July, 1973, to July, 1978, with only one operative death (3 percent). Technical factors and improved methods of myocardial protection during the operation directly influence this decrease in operative mortality rate. The indication for reoperation was incapacitating angina developing within 2 months of the inital operation in 18 patients (early failures) and after more than 2 months in 30 patients (late failures). The early failures were most commonly attributed to technical factors (33 percent) and graft occlusion by exuberant pericardial scarring (33 percent). The late failures were commonly related to the development of new native coronary lesions (47 percent) and selection of an incorrect site for distal anastomoses (23 percent). The prognostic and therapeutic implications of these findings will be discussed in detail. Angina was abolished or significantly decreased in 90 percent of the survivors, and there were only two late deaths occuring 18 and 20 months postoperatively. These data indicate that patients undergoing repeat myocardial revascularization can be operated upon with low operative mortality rates and symptomatic improvement comparable to that of patients undergoing coronary artery bypass for the first time.

Adult↗