The effect of Gram negative endotoxin on the calcium uptake activity of sarcoplasmic reticulum isolated from canine myocardium

Dantrolene ameliorates the metabolic hallmarks of sepsis in rats and improves survival in a mouse model of endotoxemia

Sepsis is the systemic inflammatory response resulting from serious infection and is the most common cause of death in intensive care units. Intracellular free calcium concentration ([Ca2+]i) is an important regulator of numerous cellular processes and when increased excessively may act as a potent cellular toxin. To determine if [Ca2+]i is responsible for the major metabolic changes which are hallmarks of sepsis, we examined if sodium dantrolene, a drug which decreases release of calcium from sarcoplasmic reticulum, affected the metabolic abnormalities in plasma and epitrochlearis muscles of rats made septic by cecal ligation and perforation. Dantrolene when added in vitro or when given in vivo decreases many of the metabolic hallmarks of sepsis--i.e., muscle protein breakdown approximately 30%, muscle glucose transport approximately 38%, muscle lactate formation approximately 28%, and plasma lactate approximately 29% (P < 0.05). In addition, we examined the ability of dantrolene to improve survival in a mouse model of endotoxemia. Dantrolene caused > 2-fold improvement in survival when it was administered concurrently with endotoxin (54% vs. 20% survival in dantrolene-treated and control mice, respectively (P < 0.001). Our results are consistent with the hypothesis that an increase in [Ca2+]i plays an important role in the metabolic abnormalities which occur during sepsis and that dantrolene administration may be an effective therapeutic strategy.

Inotropic response to digoxin and dopamine in patients with severe sepsis, cardiac failure, and systemic hypoperfusion

We studied the inotropic response to dopamine and digoxin in 20 patients with severe sepsis and left ventricular failure. Left ventricular failure was defined as a left ventricular stroke work index less than or equal to 40 g.m/m2 at a pulmonary artery wedge pressure greater than or equal to 15 mm Hg. Hemodynamic assessment was obtained before and following administration of digoxin 10 micrograms/kg IV or dopamine, 5 to 12 micrograms/kg/min IV. Patients treated with digoxin demonstrated a significant increase in LVSWI. The LVSWI increased 13 +/- 10 percent in the dopamine-treated patients compared with 74 +/- 16 percent in the digoxin patients (p less than 0.02). We conclude that digoxin exhibited significant inotropic activity in patients with sepsis.

A comparison of the cardiovascular effects of dobutamine and a new dopamine derivative (D4975) during shock induced by E. coli endotoxin

1 The effects of a newly developed dopamine-xanthine derivative, 7-propyl-theophylline-dopamine (D4975) and of dobutamine have been examined in anaesthetized cats before and after the induction of shock with E. coli endotoxin. 2 Both D4975 and dobutamine caused dose-related increases in left ventricular (LV) dP/dtmax (and LVdP/dt at fixed isovolumic pressures. Significantly smaller increases in LVdP/dtmax occurred as early as 0.5 to 1 h after endotoxin, with maximal attenuation at 1 to 2 h and some improvement in sensitivity in cats surviving 2 to 4 h. The maximum response to each drug was markedly reduced in shock. 3 Neither D4975 nor dobutamine had significant effects on heart rate. D4975 caused dose-related increases in systemic arterial blood pressure which were smaller during shock, the changes in responsiveness following those in LVdP/dtmax. 4 Possible mechanisms responsible for changing myocardial sensitivity to these and other agents are discussed. It is concluded that D4975 may be more useful in the treatment of shock than either dopamine or dobutamine because (a) it is more potent during shock than dobutamine (perhaps as a result of phosphodiesterase inhibition by the theophylline component of D4975); (b) its action is longer-lasting than dobutamine or dopamine and (c) like dobutamine, its effect on heart rate is insignificant.

Myocardial failure with altered response to adrenaline in endotoxin shock

1 There is a growing concensus that myocardial performance in the early stages of experimental endotoxic and septic shock is relatively normal; however, recent reports have identified an intermediate phase of shock when myocardial dysfunction is clearly apparent.2 The mechanism of dysfunction has become a subject of intense investigation. A current view is that altered myocardial responsiveness to circulating catecholamines may play an important role in the dysfunction observed after endotoxin administration. The present studies, in which an isolated working heart preparation of the dog was used, were designed to test this hypothesis. This particular experimental preparation was selected to provide an adequate interpretation of results; cardiac output, afterload, and concentrations of adrenaline reaching the coronary vascular bed were controlled in all experiments. Responses to infusions of adrenaline were recorded in the ;steady-state' condition. Control (non-shocked) heart responses to adrenaline were highly reproducible in terms of inotropic, chronotropic and coronary vascular behaviour.3 Results from the study document myocardial dysfunction within 4-6 h following an LD(70) endotoxin administration on the basis of increased left ventricular end diastolic pressure (LVEDP), decreased cardiac power and myocardial efficiency, and depressed negative and positive dP/dt parameters.4 Findings suggest significantly altered responsiveness of the myocardium to infused adrenaline at rates of 1, 2, and 5 mug/min with concentrations between 10 and 1 ng/ml blood. LVEDP was elevated while calculated power and efficiency parameters remained significantly below control values during infusion of adrenaline in endotoxin-treated hearts. Depressions of responsiveness were interpreted to occur on the basis of failure to restore positive and negative dP/dt to normal values and depressed coronary blood flow responses during adrenaline administration. Increases in coronary flow were regularly less in experimental hearts than the controls. Heart rate responses to adrenaline in both failing and non-failing hearts were identical.5 In conclusion, it is suggested that myocardial contractile and relaxation characteristics and coronary vascular responses to adrenaline infusion are depressed in endotoxin shock during the period of demonstrated myocardial dysfunction. No distinct causal relationships were observed between the altered myocardial responsiveness and pathogenesis of heart dysfunction since myocardial dysfunction and altered responsiveness to adrenaline were generally observed together. Myocardial oedema formation after endotoxin as previously reported by this laboratory may bear a relationship to the depressed negative dP/dt response to adrenaline.

Myocardial and circulatory effects of E. coli endotoxin; modification of responses to catecholamines

1. The predominant acute effect of E. coli endotoxin in anaesthetized, ventilated cats was pulmonary hypertension resulting from a 8-12 fold increase in pulmonary vascular resistance. This was followed by decreases in left ventricular (LV) and systemic arterial pressures and in LV dP/dt max. Recovery occurred within 2-4 min and was dependent upon increased sympathetic drive; recovery did not occur in cats treated with the beta-adrenoceptor blocking drug alprenolol.2. The pulmonary vasoconstriction was reduced in cats given compound 48/80 and evidence is presented that it results primarily from histamine release.3. Over the 2-3 h period following endotoxin injection, systemic arterial pressure tended to decrease and heart rate and myocardial metabolic heat production to increase. Myocardial blood flow and LV dP/dt remained fairly stable until the terminal stages of shock.4. The predominant delayed effect of E. coli endotoxin in cats were a markedly reduced stroke volume, an increase in peripheral vascular resistance and a severe metabolic acidosis (arterial base excess-20 mEq/litre). Arterial pO(2) and pCO(2) were not significantly affected. It is concluded that myocardial contractility is maintained at this time through the release of catecholamines and that endotoxin itself depresses contractility.5. The effects of adrenaline and noradrenaline infusions on systolic and diastolic blood pressures, heart rate, cardiac output, myocardial blood flow and LV dP/dt max were markedly reduced in the period 2-3 h after endotoxin. In a few animals some recovery of the response to noradrenaline occurred and was associated with a general circulatory improvement and a reduced metabolic acidosis.