The effect of intravenous potassium on myocardial contractility and cardiac dynamics

Rapid Transfusion Devices for Hemorrhagic Cardiothoracic Trauma

Cardiothoracic trauma patients are frequently hypovolemic and hypothermic and may require massive transfusion, which can itself causesuch complications as acidosis, electrolyte imbalance (hypocalcemia and hyperkalemia), hypothermia, di lutional coagulopathy, and adultrespiratory distress syn drome. At the present time, there are a number of rapid infu sion devices such as Level I® (capable of delivering 37°C at a flow rate of up to 600 ml/min), Fluid Management System® (FMS®) (which can deliver 37.5°C of fluid at a flow rate of up to 500 ml/min), Rapid Infusion System® (RIS®) (which can pro vide up to 1,500 ml of 37°C fluid in one and one half minutes), and Rapid Solution Administration Set® (RSASO) (which can not only deliver a maximum of 2,200 m/min, but can warm the fluid to normothermia at a flow rate of 500 ml/min). However, pressurized devices such as Level IO can cause air embolism, interstitial infiltration and the compartment syndrome, and the flow rate is not operator-controlled. Devices such as FMS®, RIS®, and RSAS® incorporate a cardiotomy reservoir which has the potential for clot formation when any calcium-con taining solution is added. In this article, rapid infusion devices are compared, and complications associated with massive transfusion are described.

Postreperfusion syndrome: hypotension after reperfusion of the transplanted liver

Sixty-nine patients undergoing liver transplantation were evaluated to elucidate the relationship between hypotension and physiological changes seen on reperfusion of the grafted liver. Measured variables included hemodynamic profiles, core temperature, serum potassium, ionized calcium levels, arterial blood-gas tensions, and acid-base state. Measurements were taken 60 minutes after skin incision (baseline), 5 minutes before reperfusion, and 30 seconds and 5 minutes after reperfusion. On the basis of changes in mean arterial pressure (MAP) patients were divided in two groups. Group 1 (n = 49) maintained MAP greater than 70% and group 2 (n = 20) had MAP less than 70% of the baseline value for at least 1 minute within 5 minutes after reperfusion. On reperfusion, changes common to both groups were 27% increase in cardiac filling pressures, 23% base deficit, and 30% serum potassium level and a decrease of 16% in cardiac output and 9% in temperature. Compared with group 1, group 2 had greater decrease in systemic vascular resistance (SVR) (1097 +/- 868 and 741 +/- 399 dyn.s-1. cm-5, respectively, P < .05) and higher potassium level (4.5 +/- 0.8 and 5.3 +/- 0.8 mmol/L, P < .05). Collectively in both groups, there was no correlation between MAP and physiological variables; however, there was a poor correlation with SVR (r = .32, P < .01). Reperfusion hypotension seen in group 2 patients correlated only with a decrease in systemic vascular resistance (r = .5, P < .05). Acute hyperkalemia, hypothermia, and acidosis do not appear to be major causes of reperfusion hypotension.

Effects of certain antibiotics on isometric contractions of isolated rat heart muscle

The direct effects of potassium-penicillin-G, kanamycin, streptomycin and chloramphenicol on isometric contraction of isolated rat heart muscle were examined. Potassium-penicillin-G did not depress myocardial contractility but rather increased it. Those increases are not due to penicillin itself but due to a small amount of K+ in potassium-penicillin-G. Kanamycin and streptomycin did show not only direct myocardial depressants effects but concentration-dependent depressions. The depression produced by kanamycin could be restored to normal by adding Ca++ to the bath solution. Chloramphenicol did not show any significant concentration-dependent depression in our studies. We conclude that it is important to be aware of the potential depression of cardiac function by antibiotics, particularly in patients who have diminished cardiac reserve and who are undergoing surgical procedures under anesthesia which may also depress cardiac function.

Influence of extracellular potassium concentration on myocardial uptake and inotropic effect of tritiated digoxin

Because of conflicting reports on the influence of extracellular potassium concentration ([K] 0 ) on the inotropic action of cardiac glycosides, we compared the effects of varying [K] 0 (1.5, 4.5, and 7.5m M ) on the inotropic action and myocardial concentration of tritiated digoxin (5 x 10 -7 M ) using the isolated cat papillary muscle. The time course of the inotropic response to digoxin was significantly altered by [K] 0 in an inverse manner; the rate of change of the active tension response to digoxin (g/mm 2 · min -1 ) was 0.048±0.004 with low [K] 0 , 0.025±0.003 with normal [K] 0 and 0.014±0.002 with high [K] 0 . There were no differences, however, in the peak inotropic responses achieved at each [K] 0 . Muscles were analyzed for 3 H-digoxin content after 45 minutes, and at the time of the peak inotropic response. The relationships found between [K] 0 and 3 H-digoxin content were similar to those found between [K] 0 and active tension. Moreover, a significant positive correlation between digoxin content and the increment in active tension was observed. Thus, an inverse relationship exists between [K] 0 and the rate of development of the inotropic response to digoxin, changes that may be due to a [K] 0 induced alteration in myocardial digoxin content.

Studies on digitalis. 13. A comparison of the effects of potassium on the inotropic and arrhythmia-producing actions of ouabain

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