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Biomedical subjects

S R Igo

Publications and source records attributed to S R Igo.

At least 37 records · Page 2Linked to original sources
PubMed1981

Combined use of dopamine and nitroprusside therapy in conjunction with intra-aortic balloon pumping for the treatment of postcardiotomy low-output syndrome.

Intra-aortic balloon pumping (IABP) has been utilized in our institution in over 600 patients for the treatment of postcardiotomy low-output syndrome, with a 59% survival rate. Volume loading and pharmacologic treatment have played integral roles in the overall treatment of this syndrome. This investigation documents the hemodynamic effectivenss of combined nitroprusside/dopamine therapy in patients who required IABP for weaning from cardiopulmonary bypass. Serial hemodynamic measurements were made before and during infusion of nitroprusside (0.5 to 5.0 microgram/kg/min) and after combined nitroprusside/dopamine (7.5 micrograms/kg/min) therapy in 10 patients during IABP. Prior to pharmacologic therapy, cardiac index was 1.6 +/- 0.4 L/min/m2 and systemic vascular resistance (SVR) was 2,774 +/- 932 dynes sec cm-5. After nitroprusside infusion, cardiac index increased to 1.8 +/- 0.5 L/min/m2 (NS) and SVR decreased to 1,957 +/- 791 dynes sec cm-5 (p less than 0.01). The simultaneous infusion of nitroprusside and dopamine resulted in further augmentation of cardiac index to 2.5 +/- 0.5 L/min/m2 (p less than 0.01) and an additional reduction of SVR to 1,439 +/- 358 dynes sec cm-5 (p less than 0.02). In addition, pressure-rate-product, an index of myocardial oxygen demand, was decreased by nitroprusside (p less than 0.02) but was not significantly altered by both agents. This study provides a rationale for the combined use of nitroprusside/dopamine in postcardiotomy low-output syndrome necessitating IABP when SVR is greater than 2,000 dynes sec cm-5 and cardiac index is less than 2.0 L/min/m2.

Assisted Circulation↗
PubMed1980

Quantitative indices of intra-aortic balloon pump (IABP) dependence during post-infarction cardiogenic shock.

This study attempts to quantitate post-infarction cardiogenic shock IABP dependence in instances of massive myocardial infarction with the use of hemodynamic indices plotted over time-course trajectories. Mortality is predicted when age and hemodynamic performance are also considered. It appears that post-infarction IABP dependence can be quantitated and that such information can be useful in considering diagnostic and therapeutic alternatives during the course of IABP support and cardiogenic shock. The analysis suggests that such IABP-dependent patients could be considered for therapeutic alternatives. They do not expire during the first 50 hours of IABP support and neither improve nor deteriorate during the second 50 hours of support. They remain in Class B without the occurrence of life-threatening ventricular dysrhythmias for a sufficient time for cardiac catheterization to determine the appropriateness of corrective procedures.

Adult↗
PubMed1979

RIGHT AND LEFT VENTRICULAR HEMODYNAMIC INDICES AS PREDICTORS OF THE NEED FOR AND OUTCOME OF POST-CARDIOTOMY MECHANICAL INTRAAORTIC BALLOON PUMP SUPPORT.

Preoperative cardiac catheterization data of 21 patients requiring intraaortic balloon pumping (IABP) for weaning from cardiopulmonary bypass were analyzed and compared with similar data in 28 patients who underwent nearly similar operative procedures, but did not require IABP for weaning. Cardiac index (CI) and systemic vascular resistance (SVR) were found to have predictive value for the need of IABP for weaning from cardiopulmonary bypass and differentiated survival from non-survival. Left ventricular end diastolic pressure (LVEDP) was not found to be predictive. Ejection fraction (EF) was significantly lower in those who required IABP than those who did not; EF did not predict the outcome. Pulmonary capillary wedge pressure ([unk]), pulmonary artery pressure ([unk]) and pulmonary vascular resistance (PVR) were predictive of the need for IABP, but not the outcome. Left ventricular minute work index (LVMWI) was significantly lower in those requiring IABP, right ventricular minute work index (RVMWI) was predictive of survival with IABP. Together, LVMWI and RVMWI were predictive of the need for and outcome of IABP following cardiopulmonary bypass. Twenty-seven of 28 control RVMWI's were normal. No patient requiring IABP had depressed RVMWI's preoperatively. Elevated preoperative RVMWI's were associated with 80% survival with postcardiotomy IABP; normal RVMWI's were associated with a 56% survival with post-cardiotomy IABP. Elevated preoperative RVMWI's reflected moderate to maximal right ventricular compensatory capacity in response to depressed left ventricular function. Normal preoperative RVMWI's in the presence of depressed LVMWI's were indicative of decreased right ventricular compensatory capacity in post-cardiotomy IABP-support settings. Right ventricular function is as important as left ventricular function as a prognosticator for the need and outcome of IABP support of the failing post-cardiotomy circulation.

Journal Article↗
PubMed1979

CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT.

An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.

Journal Article↗
PubMed1979

Efficacy of nitroprusside therapy in postcardiotomy low-output syndrome necessitating intra-aortic balloon counterpulsation.

Serial hemodynamic measurements were obtained before, during, and after nitroprusside therapy over a 24 hour period in 19 patients requiring intra-aortic balloon pumping (IABP) for successful weaning from cardiopulmonary bypass. Nitroprusside, administered in doses ranging from 0.5 to 5 micrograms/kg/min, effected significant reductions in mean aortic pressure and systemic vascular resistance within 20 to 30 minutes. Mean aortic pressure decreased from 108 +/- 22 mm Hg to 85 +/- 27 mm Hg (p less than 0.005). Systemic vascular resistance decreased from 2,705 +/- 1,072 to 1,942 +/- 823 dynes sec cm-5 (p less than 0.005). 2n response to nitroprusside-induced decreases in left venticular afterload, cardiac indes increased from 1.83 +/- 0.58 to 2.04 +/- 0.54 L/min/m2 (p less than 0.025). Pulmonary capillary wedge pressure (PCW), right atrial pressure, right and left ventricular minute work indices, and the rate-pressure products did not change, indicating that nitroprusside administration during IABP further increased cardiac output without increasing ventricular filling pressure, ventricular work, or indices of myocardial oxygen consumption. The data suggest that nitroprusside, in conjunction with volume loading to optimal preload levels (PCW = 15 to 18 mm Hg), augments ventricular performance in postcardiotomy low-output syndrome by lowering impedance to left ventricular ejection through a direct dilator effect on vascular smooth muscle, without a direct effect on cardiac muscle. Thus it is a valuable pharmacologic adjunct during mechanical (IABP) support of the failing circulation.

Blood Pressure↗
PubMed1978

Molecular, microscopic, microstructural and mechanical methods of analyzing pseudoneointimal linings within partial artificial hearts in man and the calf.

Ex vivo molecular, microscopic (cellular), microstructural and mechanical methods have been utilized to evaluate biologic, blood-interfacing linings (pseudoneointimal) formed on textured, fibril-flocked pumping surfaces within abdominal left ventricular assist devices (ALVADs) on partial artificial hearts. Thus far, seventeen human and twenty bovine pseudoneointimal linings (1--28 day pumping durations) have been evaluated by these methods. The results indicate that pseudoneointima begins developing within 24 hours after contact of the pumping surface with blood and is well developed at five days. The linings exhibit surface immunofluorescent fibrinogen activity, viable surface macrophages and histiocytes and scattered erythrocytes at ALVAD removal. Structurally similar linings (20 micrometer to 500 micrometer in thickness) develop in calves and in man. Mechanically, pseudoneointima is a stable, adherent, highly compliant, isotropic structural material. It is linearly elastic and strain-rate independent, with small viscous energy losses under physiologic strains. The methods employed for the evaluation of pseudoneointima provide useful information to determine the suitability of textured or rough surfaces for blood interfacing. The cumulative results indicate that the textured surface approach is useful for intermediate-term clinical ALVAD utilization.

Animals↗
PubMed1978

Intra-aortic balloon pumping: theory and practice. Experience with 325 patients.

Intra-aortic balloon pumping to support the failing circulation is now an accepted therapeutic modality. The device is simple. Insertion can be accomplished rapidly and efficiently in emergency rooms, coronary care units, cardiac catheterization suites and operating rooms, preoperatively, intraoperatively and postoperatively. The hemodynamic effects are immediate and predictable, and the accruing clinical results show increasing survival and hospital discharge rates. In these institutions, mechanical support of the circulation by this and more advanced methods has been formalized within the responsibility of a Circulatory Support Service. The purpose of this report is to summarize some observations and analyses which have been made during care of 325 consecutive postcardiotomy and/or postinfarction cardiogenic shock patients. Historical, theoretical, basic, and applied aspects and current results are included. Foremost are the straightforward concepts of considering the heart as a pump, the failing heart as a failing pump and intra-aortic balloon pumping as a temporary intravascular, auxiliary pump, capable of stabilizing or reversing that failure if utilized early in its evolution.

Adult↗
PubMed1977

An intracorporeal (abdominal) left ventricular assist device. Initial clinical trials.

We have initiated clinical trials with an intracorporeal (abdominal) partial artificial heart and ten preterminal postcardiotomy patients have been studied. During profound left ventricular failure, the device captures the entire cardiac output from the apex of the left ventricle at low pressures (20 to 40 mm Hg) and ejects (at 80 to 150 mm Hg) into the infrarenal abdominal aorta; the biological aortic valve opens only intermittently and the entire systemic circulation is pump generated. The device is six to ten times more effective than intra-aortic balloon pumping in man and has maintained systemic perfusion during clinical asystole and ventricular fibrillation. We have documented that the profoundly depressed postcardiotomy left ventricle, initially incapable of ejection, can recover during total left ventricular unloading with the abdominal left ventricular assist device support over a seven-day period.

Abdomen↗
PubMed1977

Prognostic indices for survival during postcardiotomy intra-aortic balloon pumping. Methods of scoring and classification, with implications for left ventricular assist device utilization.

To define more clearly a salvageable patient for possible utilization of a left ventricular assist device prior to multiple organ failure and irretrievability during postcardiotomy intra-aortic balloon pumping (IABP), we made prospective and retrospective analyses to determine prognostic indices for survival. Serial left ventricular function curves (IABP on-off), scoring methods, hemodynamic and renal function tracking trajectories, survival versus nonsurvival data envelopes, and classification methods were developed and used. All patients requiring postcardiotomy IABP support who were in Class A survived; 80 percent of the patients in Class B survived. All patients who remained in Class C for 12 hours or more following operation with IABP support died. These preliminary analyses suggest that the postcardiotomy IABP-supported patient with a score of less than 6 who remains in Class C for 12 hours or more is at the highest possible risk and is a probably candidate for more effective support with a left ventricular assist device.

Assisted Circulation↗
PubMed1976

Production of controlled reversible left ventricular failure in calves using intracoronary lidocaine hydrochloride: a useful method of evaluating left ventricular assist devices.

The experimental production of stable, controlled, short-term left ventricular failure is valuable in the evaluation of implantable circulatory support systems. Acute or chronic left ventricular failure produced by occlusion or embolization of coronary arteries results in muscle dysfunction and degrees of failure that may be difficult to control. The effects of varying amounts of intracoronary lidocaine were studied during short- and long-term evaluations of intracorporeal left ventricular assist pumping. In 8 Hereford calves the left main coronary artery was cannulated with an intracoronary catheter in open and closed chest preparations. Dose-related negative inotropic effects were noted when lidocaine was injected at individual doses of 50, 75, and 100 mg. Following 100 mg doses, mean aortic pressure, cardiac output, and maximum rate of rise of left ventricular pressure decreased; left ventricular end-diastolic pressure increased fourfold. Similar effects were noted with short continuous infusions of lidocaine. The initial responses to injection or continuous infusions, if effective, were noted within 40 to 60 seconds. Several episodes of failure could be produced with either method following recovery periods of 10 to 15 minutes. In all instances, actuation of a left ventricular assist device immediately reversed the hemodynamic effects of the pharmacologically induced failure.

Animals↗
PubMed1976

Chronic evaluations of ventricular ejection phase dynamics during abdominal left ventricular assist device (ALVAD) pumping in the awake, unanesthetized calf.

In 1974, between 2 and 8% of the 50,000 adult patients undergoing cardiac surgery in this country succumbed in the early post-operative period from left ventricular failure, despite various methods of pharmacologic and/or mechanical support. Our laboratories have concentrated on the development, modification, evaluation, and validation of an abdominally positioned left ventricular assist device which has the potential of reducing these mortalities. Continuous testing in animals, for periods exceeding 2 mos, satisfied reliability, durability and longevity requirements. The cumulative results of these investigations were reviewed at the National Heart and Lung Institute on August 21, 1975. Authorization for clinical trials of the device according to specific criteria and protocols46 was approved on November 1, 1975. The ALVAD is now in the early stages of clinical testing. The results of the current experiments demonstrate that ventricular outflow impedance and prosthetic inflow impedance are the major determinants of left ventricular assist device hemodynamic effectiveness. By markedly reducing outflow impedance, the ALVAD profoundly lowers ventricular pressure-work and oxygen demands while simultaneously increasing ventricular performance and maintaining or augmenting systemic perfusion. Moreover, our studies indicate that improved device designs (intended for intermediate and long-term implantation) and maximal performance can be achieved by focusing on these central determinants.

Animals↗