Negative inotropic effect of lidocaine in patients with coronary arterial disease and normal subjects

Pulmonary Doppler flow velocity pattern during caudal epidural anaesthesia in children

BACKGROUND

Haemodynamic effects of caudal anaesthesia in children have not been fully investigated. In the present study, we evaluated pulmonary haemodynamics during caudal anaesthesia in otherwise healthy children using Doppler-echocardiography.

METHODS

Fifteen children undergoing elective lower abdominal surgery were randomly divided into two groups: nine children received 1.5% lidocaine and six physiological saline in the caudal epidural space. General anaesthesia was slowly induced and maintained using nitrous oxide and sevoflurane in oxygen. An epidural catheter was inserted into the caudal epidural space. Haemodynamic data including those with echocardiography were measured before and after epidural administration of lidocaine or saline.

RESULTS

Mean blood pressure, end diastolic diameter of the left ventricle, ejection fraction of the left ventricle and mean velocity circumferential fibre shortening did not change in either group following caudal epidural block. Indices of pulmonary Doppler flow velocity, including peak velocity of pulmonary flow and acceleration-to-ejection time ratio, demonstrated a significant decrease after caudal lidocaine, but not after saline.

CONCLUSIONS

Our data suggest that pulmonary Doppler flow velocity changes during caudal epidural anaesthesia, probably due to an increase in the pulmonary arterial resistance.

Changes in systolic time intervals-a non-invasive marker for the haemodynamic effects of sumatriptan

AIMS

This study assessed the use of systolic time intervals (STI) as a potential non-invasive marker of the haemodynamic effects of sumatriptan, a 5HT1 receptor agonist.

METHODS

Twenty-six patients undergoing diagnostic cardiac catheterization participated. STIs were derived from haemodynamic pressure tracings at baseline, following placebo injection and following either subcutaneous (n=18) or intravenous injection (n=8) of sumatriptan.

RESULTS

Sumatriptan (i.v. or s.c.) was associated with significant increases in mean arterial pressure (95% C.I. 9,14mmHg, P=0.0001), total electromechanical systole (95% C.I.8,36ms, P<0.0001), pre-ejection period (95%C.I. 8,21ms, P=0.0001) and left ventricular ejection time (95% C.I. 2,12ms, P=0.004). Conclusion STI responses were consistent with sumatriptan-induced changes in afterload. In summary, the measurement of STIs is a potential non-invasive method of investigating the influence of serotonergic compounds on the cardiovascular system.

Lidocaine prophylaxis for fatal ventricular arrhythmias after acute myocardial infarction

OBJECTIVE

To compare the efficacy and safety of a 40-hour lidocaine infusion after completion of a 8-hour open-label infusion for prophylaxis of primary ventricular fibrillation in patients with uncomplicated acute myocardial infarction.

METHODS

This was a double-blind, randomized placebo-controlled trial held in the coronary care unit of a large nonprofit hospital. We studied 200 patients with uncomplicated acute myocardial infarction in Killip class I or II who came to the hospital within 6 hours of onset of symptoms and 22 patients who had ventricular fibrillation before the start of the study. Intervention consisted of an 8-hour lidocaine infusion followed by placebo or lidocaine for an additional 40 hours. The infusion rate was adjusted in patients > or = 70 years old and in those < 50 kg or > or = 90 kg. Measurements recorded were baseline demographic characteristics, incidence of ventricular arrhythmias, adverse reactions, and death.

RESULTS

New congestive heart failure developed during the randomized phase in 9% of patients receiving lidocaine and in 2% of patients receiving placebo (p = 0.03). Ventricular fibrillation did not occur during the treatment period, and sustained ventricular tachycardia developed in one patient receiving placebo. The in-hospital mortality rate was comparable in both groups (4% versus 2%; p = 0.68) but was much higher (13.6%) in patients with initial ventricular fibrillation not included in the randomized study.

CONCLUSIONS

A 40-hour age- and weight-adjusted lidocaine infusion administered after an initial 8-hour infusion provoked more congestive heart failure than placebo. In view of the absence of ventricular fibrillation episodes with both infusions, caution should be used when lidocaine is administered for longer than 8 hours in patients with uncomplicated myocardial infarction.

The pharmacokinetics of lignocaine and beta-adrenoceptor antagonists in patients with acute myocardial infarction

Lignocaine (lidocaine) and beta-adrenoceptor antagonists are widely used after acute myocardial infarction. The therapeutic value of these agents depends on the achievement and maintenance of safe and effective plasma concentrations. Lignocaine pharmacokinetics after acute myocardial infarction (MI) are controlled by a number of variables. The single most important is left ventricular function, which affects both volume of distribution and plasma clearance. Other major factors include bodyweight, age, hepatic function, the presence of obesity, and concomitant drug therapy. Lignocaine is extensively bound to alpha 1-acid glycoprotein, a plasma protein which is also an acute phase reactant. Increases in alpha 1-acid glycoprotein concentration occur after an acute MI, decreasing the free fraction of lignocaine in the plasma and consequently decreasing total plasma lignocaine clearance without altering the clearance of non-protein-bound lignocaine. Complex changes in lignocaine disposition occur with long term infusions, and therefore early discontinuation of lignocaine infusions (within 24 hours) should be undertaken whenever possible. Because the risk of ventricular tachyarrhythmia declines rapidly after the onset of an acute MI, lignocaine therapy can be rationally discontinued within 24 hours in most patients. Lignocaine has a narrow toxic/therapeutic index, so that pharmacokinetic factors are critical in dose selection. In contrast, beta-adrenoceptor antagonists' adverse effects are more related to the presence of predisposing conditions (such as asthma, heart failure, bradyarrhythmias, etc.) than to plasma concentration. The pharmacokinetics of beta-adrenoceptor antagonists are important to help assure therapeutic efficacy, to provide information about the anticipated time course of drug action, and to predict the possible role of ancillary drug effects (such as direct membrane action) and loss of cardioselectivity. Lipid solubility is the main determinant of the pharmacokinetic properties of a beta-adrenoceptor antagonist. Lipid-soluble agents like propranolol and metoprolol are well absorbed orally, and undergo rapid hepatic metabolism, with important presystemic clearance and a short plasma half-life. Water-soluble drugs like sotalol, atenolol, and nadolol are less well absorbed, and are eliminated more slowly by renal excretion. Clinical assessment of beta-adrenoceptor antagonism is more valuable than plasma concentration determinations in evaluating the adequacy of the dose of a particular beta-adrenoceptor antagonist.(ABSTRACT TRUNCATED AT 400 WORDS)

Uncorrected pre-ejection period: a simple non-invasive measurement for pharmacodynamic screening of inotropic activity

Since heart rate (HR) is an important determinant of the duration of systole, systolic time intervals (STI) from 8 healthy subjects were examined after infusion of atropine. As no overall correlation was found between HR and pre-ejection period (PEP), the results confirm the need for individual estimates of the correction of the left ventricular ejection time (LVET) and the total electromechanical systole (OS2). In the same subjects the sensitivity of PEP to minor negative inotropic effects of mexiletine and disopyramide measured at Cmax was confirmed. Thus, in addition to its simplicity and reliability, the sensitivity of the uncorrected PEP should encourage use of this technique as part of any screening system for the early detection of an inotropic effect of new chemical entities.

Cardiac and microcirculatory effects of different doses of prostaglandin E1 in man

A cumulative dose response to intravenous PGE1 was established in 12 healthy volunteers. Systolic time intervals, including pre-ejection period (PEP), the ventricular ejection time (VET) and the RR-interval, were continuously determined, and transcutaneous oxygen pressure (tcpO2) was recorded. RR-intervals fell in a dose dependent manner, reaching a significantly lower level at 128 ng.kg-1.min-1 of PGE1 (basal value 842 ms falling to 756 ms). PEP decreased from 89 ms to 74 ms and the ratio PEP/VET decreased from 35% to 30%, indicating increased myocardial contractility. The maximal increase in tcpO2 was 125% on the calf and 60% on the foot. The peak tcpO2 was observed at an infusion rate of 16 ng.kg-1.min-1 PGE1. A decline in tcpO2 was seen at infusion rates greater than 64 ng.kg-1.min-1 PGE1 indicating a decrease in skin perfusion. The results indicate that the effects of intravenous PGE1 on skin perfusion occur at a lower threshold than the increase in myocardial contractility. A maximal increase in skin perfusion can be achieved with doses of PGE1 devoid of systemic haemodynamic effects.

Systolic time intervals in evaluation of the negative inotropic effect after single oral doses of mexiletine and disopyramide

A placebo-controlled, single blind, crossover study was done to evaluate the inotropic effects of single oral doses of mexiletine and disopyramide assessed by the measurement of Systolic Time Intervals (STI). Each of 8 healthy volunteers received five treatments in random order: 200 and 400 mg mexiletine, 100 and 200 mg disopyramide, and placebo. There was a significant increase in cumulated PEP after 400 mg mexiletine and 200 mg disopyramide. There was no significant change in LVET and QS2. Peak plasma levels were in the lower range of the reputed antiarrythmic levels. Plasma concentration-effect relationships are discussed. Although the study revealed large inter- and intrasubject variability in the measured STIs, it is concluded that a negative inotropic effect was detected despite the low plasma levels of the minor negative inotropic drugs.

Hemodynamic effects of antiarrhythmic drugs

In order to use antiarrhythmic drugs safely, one must understand their hemodynamic effects. Quinidine and the calcium antagonists have direct cardiac effects and frequently opposing autonomically mediated or indirect cardiac effects. Lidocaine is exceptionally well tolerated, even by patients with severe left ventricular dysfunction. Phenytoin and procainamide have the potential for serious adverse effects, but are generally well tolerated at usual doses. Disopyramide causes serious depression of left ventricular function in many patients because of its direct myocardial depressant and peripheral vasoconstricting actions. Although bretylium causes an immediate increase in contractility, it can ultimately result in important hypotension. In this review the in vitro and in vivo hemodynamic effects of these and other antiarrhythmic drugs are discussed to provide information that will assist the clinician in using these drugs properly.

Effect of procainamide on left ventricular performance in patients with primary myocardial disease

The effect of procainamide (P) on left ventricular function as measured by the systolic time intervals (STI) was studied in 14 patients with primary myocardial disease. P, 7.5 mg/kg body weight, was given intravenously at a rate of 100 mg per minute. Administration of P produced a decrease in left ventricular performance as manifest by a significant prolongation of the pre-ejection period corrected for heart rate (PEPI) and an increase of the PEP to the left ventricular ejection time (LVET) ratio. The peak effect on PEPI and PEP/LVET occurred at 2 minutes after P administration (delta PEPI + 14 +/- 1.9 ms, p < 0.001, delta PEP/LVET + 0.052 +/- 0.007, p < 0.001) with values returning towards baseline by 60 min. In 6 of the patients P blood levels were measured simultaneously with the STI measurements. Changes in PEPI and PEP/LVET directly parallel changes of P blood levels. It is concluded that P given intravenously at the usual therapeutic doses decreases left ventricular performance in patients with primary myocardial disease. These changes in left ventricular performance directly parallel procainamide blood levels.

Changes in diastolic time with various pharmacologic agents: implication for myocardial perfusion

Diastolic time (DT) is calculated as the cycle length (RR) minus electromechanical systole (QS2). The ratio of DT (RR-QS2) to RR interval times 100, or the percent diastole (%D), varies nonlinearly with heart rate (HR), increasing rapidly with decreasing HR. The effect of commonly used cardioactive agents on %D was studied in five groups of normal subjects. In group 1 (n = 12), propranolol (160 mg daily) increased %D from 55.9 +/- 1.7 to 64.7 +/- 1.3 (p less than 0.001) by slowing HR. In group 2 (n = 12), dobutamine (2.5 micrograms/kg/min) increased %D from 56.4 +/- 1.4 to 61.8 +/- 1.3 (p less than 0.005) by shortening the QS2. In group 3 (n = 10), Cedilanid-D (1.6 mg i.v.) increased %D from 55.5 +/- 1 to 63.2 +/- 0.7 (p less than 0.001), both by slowing the HR and shortening the QS2. In group 4 (n = 12), isoproterenol (2 micrograms/min) increased HR and shortened the QS2 significantly. The net result was a significant reduction of %D from 56.1 +/- 1.4 to 53.5 +/- 1.1, (p less than 0.05). In group 5 (n = 15), a 100-mg bolus of i.v. lidocaine did not have a significant effect on %D. This study indicates that cardiovascular drugs may have significant effects on the relative duration of diastole either by affecting HR or the duration of systole. This may have clinical implications for patients with coronary artery disease and patients with left ventricular hypertrophy, since in both cases coronary flow in mostly diastolic.

The hemodynamic effects of intravenous tocainide in patients with heart disease

In order to evaluate its hemodynamic actions, tocainide, a new orally effective antiarrhythmic drug, was given intravenously over a 15 minute period to 12 patients with compensated left ventricular dysfunction. Doses were 0.5 (4 patients) or 0.75 (8 patients) mg/kg/min. Hemodynamics and drug plasma concentrations were measured at the end and 15 minutes after the end of the infusion. Tocainide infusion produced small but statistically significant increases in the pulmonary and systemic vascular resistance, aortic and pulmonary arterial pressure, and left and right ventricular end-diastolic pressure. There was no significant change in left ventricular dp/dt, heart rate, or cardiac index. In patients with compensated left ventricular dysfunction, tocainide produces a small rise in vascular resistance and arterial pressure. Overall cardiac function is maintained with a small increase in left ventricular end-diastolic pressure.