Biomedical subjects

J Zelano

Publications and source records attributed to J Zelano.

4 recordsLinked to original sources

PubMed1995

Triiodothyronine improves left ventricular function without oxygen wasting effects after global hypothermic ischemia.

Cardiopulmonary bypass results in a "euthyroid sick" state. Recently, interest has focused on the relationship between low serum triiodothyronine levels and postoperative cardiovascular hemodynamics. The present study was undertaken to more clearly define the acute effects of triiodothyronine on myocardial mechanics and energetics after hypothermic global ischemia using an ex-vivo canine heart preparation to model the clinical condition. Experiments were performed on isolated hearts subjected to hyperkalemic arrest with 90 minutes of hypothermic (10 degrees C) ischemia. Isolated hearts were cross-perfused by euthyroid support dogs in which triiodothyronine levels spontaneously decreased by 65% to 75% (p < 0.01) after the initiation of cross-perfusion. In nine heart preparations, triiodothyronine (Triostat) was given as a bolus dose (0.2 micrograms/kg) after 1 hour of baseline data collection with a subsequent measurable rise in serum triiodothyronine levels (p < 0.01). In six postischemic hearts, reverse triiodothyronine was given as a 0.2 micrograms/kg bolus. Triiodothyronine was also administered to a group of eight nonischemic, continuously perfused isolated hearts. Intrinsic myocardial contractility was assessed by analysis of the preload recruitable stroke work area, energetic efficiency from the myocardial oxygen consumption-pressure-volume area relationship, and coronary vascular resistance from analysis of coronary flow and perfusion pressure. Acute administration of triiodothyronine to postischemic hearts improved the preload recruitable stroke work area from 9.5 +/- 1.42 to 14.9 +/- 2.03 x 10(7) erg/ml, a 56% increase from baseline (p < 0.001), but had no effect on the preload recruitable stroke work area of the nonischemic hearts. The inotropic response resulting from triiodothyronine treatment did not alter the myocardial oxygen consumption-pressure-volume area relationship. Triiodothyronine treatment was associated with significantly decreased coronary resistance and increased coronary flow through a range of diastolic loading conditions in the postischemic hearts. The biologically inactive thyroid hormone metabolite reverse triiodothyronine was without effect on any of the measured parameters. On the basis of these results, we conclude that the low triiodothyronine state of cardiopulmonary bypass can be reproduced in this isolated heart model and that acute triiodothyronine treatment results in a unique inotropic action manifest only in the postischemic reperfused myocardium and is accomplished without oxygen wasting effects.

Animals↗

PubMed1993

Ischemic tolerance of the arrested heart during warm cardioplegia.

Normothermic blood cardioplegia has recently generated interest as an alternative method of myocardial protection during cardiopulmonary bypass (CPB) surgery. One disadvantage is the obligatory interruption of coronary flow during the distal coronary anastomosis. This study was designed to determine the safe normothermic ischemic time of the arrested and decompressed heart. Under normothermic CPB (37 degrees C), initial cardioplegic arrest was induced with 750 cc of warm (37 degrees C) hyperkalemic blood cardioplegia in 21 adult dogs. The heart then received warm blood cardioplegia either continuously (50 cc/min), every 5 min (250 cc each) or every 10 min (350 cc each) for a total equivalent ischemic time of 30 min (n = 7 in each group). Left ventricular pressure-volume (PV) loops were measured by micromanometer and conductance (volume) catheters before, at 60 and 90 min after aortic cross-clamping. Systolic function was measured as the preload recruitable stroke work area derived from the stroke work-end diastolic volume relationship, and the diastolic stiffness constant (k) was derived from the exponential diastolic PV relationship. The q5 min group sustained minor deterioration in diastolic function while its systolic function was well maintained during recovery. There were significant reductions in both the diastolic and systolic functions in the q10 min group. The maximum drops in the septal wall pH during aortic cross-clamping were 0.05 +/- 0.02 (not significant), 0.19 +/- 0.06 (P < 0.05), and 0.40 +/- 0.09 (P < 0.01) for the continuous, q5 min and q10 min groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

PubMed1993

The effects of warm versus cold blood cardioplegia on endothelial function, myocardial function, and energetics.

BACKGROUND: Recent interest in the use of normothermic blood cardioplegia is based on theoretical advantages over the traditional method of hypothermic myocardial protection. This study was designed to compare the effects of warm and cold blood cardioplegia on left ventricular functions and energetics and coronary responsiveness. MATERIALS AND METHODS: Two groups of mongrel dogs (n = 7 each) underwent either normothermic cardiopulmonary bypass (CPB) with continuous warm (37 degrees C) blood cardioplegia or hypothermic (26 degrees C) CPB with a single dose of cold (4 degrees C) blood cardioplegia supplemented with topical cooling during 30 minutes of aortic clamping. There was no deterioration in the endothelium-dependent and -independent coronary relaxation as tested by the infusion of acetylcholine and nitroglycerin after cardioplegic arrest for either group. At 60 minutes of reperfusion, both groups had complete recovery of left ventricular contractility as measured by the preload recruitable stroke work area derived from the measurement of the ventricular pressure (micromanometer catheter) and volume (conductance catheter) relation. The analysis of myocardial energetics in terms of the myocardial oxygen consumption-pressure volume area relation did not reveal any significant changes between the y-intercepts and the slopes of the two groups. CONCLUSIONS: For 30 minutes of aortic cross-clamp time, continuous warm cardioplegia did not provide any benefit over a single injection of cold cardioplegia in coronary endothelial and smooth muscle function, myocardial function, and energetics.

Animals↗

PubMedDate not supplied

An automated system for the analyses of temporal speech patterns: description of the hardware and software.

A system (WELMAR II) is described for analyzing time patterns of speech on small computers. Temporal speech patterning refers to the pacing of the sounds and silences that make up a stream of speech. The system is particularly useful for research involving clinical populations since it has been shown that speech rhythms are sensitive to interpersonal influence, to dimensions of personality, and to psychological pathology.

Humans↗