Cardiac and peripheral vascular effects of lidocaine and procainamide

Intra-arterial lidocaine administration of lidocaine in middle meningeal artery for short-term treatment of subarachnoid hemorrhage-related headaches

BACKGROUND AND PURPOSE

We report short- and intermediate-term effects on headaches with intra-arterial injection of lidocaine in the middle meningeal artery in patients with severe headaches associated with subarachnoid hemorrhage.

METHODS

We treated seven patients with intra-arterial lidocaine in doses up to 50 mg in each middle meningeal artery via a microcatheter bilaterally (except in one patient). We recorded the maximum intensity of headache (graded by 11-point numeric rating scale) prior to procedure and every day for the next 10 days or discharge, whichever came first. We identified changes in the middle meningeal artery pre- and post-intra-arterial lidocaine administration and quantified from Grade 0 (no change) to Grade 5 (severe narrowing or near occlusion of anterior and posterior dural branches or proximal middle meningeal artery that precludes adequate imaging of distal branches).

RESULTS

We observed improvement in severity of headaches of headache in all seven subarachnoid hemorrhage patients. The resolution of headache was immediate and complete in four patients, unilateral immediate resolution in one patient, and delayed complete resolution in patient. Two patients met the definition of severe headache (defined as 2 or more days with maximum pain scores of 8 or greater or need for 3 or more different analgesics for 2 or more days) post-lidocaine treatment. One of these patients had are lapse in headache with the severity matching pretreatment severity and required a second treatment. On analysis of angiographic data, there was consistent narrowing of middle meningeal arteries after administration of intra-arterial lidocaine and was graded as 5 in 2 arteries, 4 in 10 arteries, and 3 in 2 arteries.

CONCLUSIONS

We found that intra-arterial injection of lidocaine can result in consistent amelioration of headache in patients with subarachnoid hemorrhage. The therapeutic benefit may be related to vasoconstriction (reversal of vasodilation) in the middle meningeal arteries after administration of lidocaine.

Lidocaine as an anti-arrhythmic drug: Are there any indications left?

Lidocaine is classified as a class Ib anti-arrhythmic that blocks voltage- and pH-dependent sodium channels. It exhibits well investigated anti-arrhythmic effects and has been the anti-arrhythmic of choice for the treatment of ventricular arrhythmias for several decades. Lidocaine binds primarily to inactivated sodium channels, decreases the action potential duration, and increases the refractory period. It increases the ventricular fibrillatory threshold and can interrupt life-threatening tachycardias caused by re-entrant mechanisms, especially in ischemic tissue. Its use was pushed into the background in the era of amiodarone and modern electric device therapy. Recently, lidocaine has come back into focus for the treatment of acute sustained ventricular tachyarrhythmias. In this brief overview, we review the clinical pharmacology including possible side effects, the historical course, possible indications, and current Guideline recommendations for the use of lidocaine.

An in Vivo Mouse Model to Investigate the Effect of Local Anesthetic Nanomedicines on Axonal Conduction and Excitability

Peripheral nerve blocks (PNBs) using local anesthetic (LA) are superior to systemic analgesia for management of post-operative pain. An insufficiently short PNB duration following single-shot LA can be optimized by development of extended release formulations among which liposomes have been shown to be the least toxic. In vivo rodent models for PNB have focused primarily on assessing behavioral responses following LA. In a previous study in human volunteers, we found that it is feasible to monitor the effect of LA in vivo by combining conventional conduction studies with nerve excitability studies. Here, we aimed to develop a mouse model where the same neurophysiological techniques can be used to investigate liposomal formulations of LA in vivo. To challenge the validity of the model, we tested the motor PNB following an unilamellar liposomal formulation, filled with the intermediate-duration LA lidocaine. Experiments were carried out in adult transgenic mice with fluorescent axons and with fluorescent tagged liposomes to allow in vivo imaging by probe-based confocal laser endomicroscopy. Recovery of conduction following LA injection at the ankle was monitored by stimulation of the tibial nerve fibers at the sciatic notch and recording of the plantar compound motor action potential (CMAP). We detected a delayed recovery in CMAP amplitude following liposomal lidocaine, without detrimental systemic effects. Furthermore, CMAP threshold-tracking studies of the distal tibial nerve showed that the increased rheobase was associated with a sequence of excitability changes similar to those found following non-encapsulated lidocaine PNB in humans, further supporting the translational value of the model.

Comparison of Acute Hemodynamic Effects of Lidocaine and Procainamide for Postoperative Ventricular Arrhythmias in Dogs

Heart rate and systolic, diastolic, and mean pressures were measured in two groups of dogs during treatment of postoperative ventricular arrhythmias either with intravenous (IV) 2% lidocaine hydrochloride or procainamide hydrochloride. Hemodynamic parameters were not significantly changed after IV administration of either drug. Additionally, changes in hemodynamic parameters for dogs treated with 2% lidocaine were not significantly different from those of dogs treated with procainamide. When dosed appropriately in the clinical setting, one bolus of IV procainamide was safe for the treatment of postoperative ventricular arrhythmias.

Experimental model for comparative evaluation of pharmacologically induced vasodilation of arterial wall mechanical properties

Arterial wall compliance (C) and distensibility coefficient (DC) are key factors of pathologic physiology, especially in arteries less than 2 mm in diameter. The aim of this study was to design an experimental model allowing comparative measurement of C and DC during pharmacologically induced vasodilation on small-diameter arteries. Both femoral arteries were exposed in eight New Zealand White rabbits. Diameter (d) and systolic/diastolic diameter changes (deltad) were measured simultaneously, and C and DC were calculated before and after topical application of 1 mL of 4% papaverine on the right side and topical application of 1 mL of 1% lidocaine on the left side. Diameter measurements were performed by echo tracking with 20-MHz implanted microprobes. After papaverine and lidocaine application, respectively, d increased from 1.36 mm to 2.23 mm (P < 0.0001) and from 1.45 mm to 2.4 mm (P < 0.0001), deltad increased from 0.0568 mm to 0.0571 mm (P = 0.34) and from 0.064 mm to 0.077 mm (P < 0.01), C increased from 5.7 x 10(-3) mm/mm Hg to 6 x 10(-3) mm/mm Hg (P < 0.02) and from 6.23 x 10(-3) mm/mm Hg to 8.49 x 10(-3) mm/mm Hg (P < 0.01), and DC decreased from 4.22 x 10(-3) mm Hg(-1) to 2.61 x 10(-3) mm Hg(-1) (P < 0.0004) and from 4.36 x 10(-3) mm/mm Hg to 3.46 x 10(-3) mm/mm Hg (P < 0.005). Papaverine- and lidocaine-induced changes were significantly different for deltad, C, and DC (P < 0.01). These results suggest that, unlike that with papaverine, lidocaine-induced vasodilation leads the artery up to the nonlinear part of its pressure/diameter relationship, with decreased distensibility contrasting with increased diameter and compliance. Our experimental model may be useful to compare the effects of different vasoactive drugs at different concentrations on the mechanical properties of the arterial wall.

Utilization of an isolated, blood-perfused canine papillary muscle preparation as a model to assess efficacy and adversity of class I antiarrhythmic drugs

To develop a model to predict the efficacy and adversity of class I antiarrhythmic drugs, intraventricular conduction time (IVCT), coronary blood flow (CBF), developed tension of papillary muscle (DT) and idioventricular automaticity rate (VR) were measured following drug administration in an isolated canine papillary muscle preparation cross-circulated with the heparinized blood of a donor dog. Tetrodotoxin, the prototypic fast Na+ channel blocker, and class I drugs increased IVCT and CBF, but decreased DT and VR, in a dose-dependent manner. The profiles of known class I drugs, procainamide, disopyramide, lidocaine, mexiletine and flecainide were similar, but the potencies of each drug were different. Two new class I drugs, ME3202 and AN-132, were also tested and found to have effects that were similar to that of tetrodotoxin. There was a good correlation between the doses of drugs prolonging IVCT by 50% and the canine antiarrhythmic plasma concentrations in our previous study. This model can also be used to estimate the use-dependency and the kinetics of use-dependent sodium channel block; however, it is not suitable for extensive investigation of cellular and molecular mechanisms. Thus, the use of this model facilitates the comparison of multiple cardiac effects of class I drugs and may be an effective way to better assess new antiarrhythmic drugs.

Effects of phenylephrine and ephedrine on pulmonary arterial pressure in patients with cervical or lumbar epidural anesthesia, or enflurane anesthesia

The authors studied systemic and pulmonary hemodynamic changes with ephedrine (EP) or phenylephrine (PH) when used to normalize arterial hypotension resulting from acute sympathectomy due to cervical or lumbar epidural anesthesia, or enflurane anesthesia in 52 patients. Both EP (0.2±0.05 mg·kg^-1) and PH (0.025±0.008 mg·kg^-1) produced a significant increase in pulmonary arterial pressure (PAP) with a concomitant increase in arterial pressure (AP). In the patients anesthetized with cervical epidural block and NO₂-O₂, systolic PAP increased from 22±5 to 28±8 mmHg with EP and from 23±6 to 32±10 mmHg with PH in response to approximately 30 mmHg increase of AP, and the ratio of the increment of systolic PAP to systolic AP (ΔPAP/ΔAP) was 0.15±0.08 with EP and 0.20±0.13 with PH (P<0.05); these changes did not differ significantly from those observed in the patients having lumbar epidural or enflurane-N₂O-O₂ anesthesia. The influence on cardiac output (CO) differed significantly between EP and PH; EP increased CO in all three groups (P<0.05), while PH did not elicit any significant changes in CO. A significant relationship between PAP and AP was found in patients given EP; the regression equation was ΔPAP=0.22×ΔAP-2.9 (r=0.77). The relationship in patients given PH was less significant (r=0.38). The results indicated that EP and PH elicit pulmonary hypertensive effect similarly in the patients with a high level of epidural anesthesia and that although both drugs act differently (EP mainly due to increases in the blood flow and PH solely due to its pulmonary vasconstrictive action), the increases in PAP were predictable, to some extent, from the increase of AP in anesthetized humans without predominant cardiopulmonary disorders.

Inhibitory effects of procainamide on sympathetic nerve activity in humans

In experimental animals, procainamide causes hypotension and reductions in efferent vasoconstrictor sympathetic outflow that may result from ganglionic blockade or central nervous system sympathetic inhibition. To test the hypothesis that procainamide decreases sympathetic nerve activity (SNA) in humans, we recorded postganglionic SNA in seven normal subjects in the baseline state and during infusions of procainamide HCl at 50 mg/min (loading) and 8 mg/min (maintenance). At the end of the loading infusion, mean arterial pressure (MAP) had decreased from 88.5 +/- 2.4 (mean +/- SEM) to 81.5 +/- 3.2 mm Hg (p less than 0.05), central venous pressure from 6.7 +/- 0.7 to 5.4 +/- 0.9 mm Hg (p less than 0.05), forearm vascular resistance (FVR) from 28 +/- 4.8 to 22.3 +/- 5.1 resistance units (p less than 0.05), and SNA from 259 +/- 47 to 94 +/- 26 units/min (p less than 0.05). These changes persisted during the maintenance infusion. Increased levels of SNA, FVR, and MAP provoked by the cold pressor test were reduced significantly by intravenous procainamide. In eight other subjects, intravenous procainamide HCl (15 mg/kg at 50 mg/min) caused dose-dependent inhibition of SNA that reversed as blood concentrations fell during drug washout. To determine if procainamide causes direct vasodilation, in nine subjects, graded infusions were delivered into the brachial artery at doses that produced no systemic effect. Ipsilateral FVR tended to increase during local intra-arterial infusion of procainamide. These data show that intravenous procainamide causes hypotension, vasodilation, and sympathetic withdrawal. Vasodilation does not result from a direct vasorelaxant effect of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of lignocaine on coronary blood flow, systolic myocardial function and myocardial high energy phosphate stores in swine

1. To investigate the effect of lignocaine upon coronary blood flow, myocardial systolic wall function and high energy phosphate stores, lignocaine was administered as a rapid intravenous injection to 14 open chest anaesthetized swine. 2. Before and after injection, measurements were made of coronary blood flow by electromagnetic flow probe, per cent wall thickening by ultrasonic crystals, adenosine triphosphate (ATP) and creatine phosphate (CP) content by myocardial biopsy, and arterial pressure by central aortic catheter. The animals were divided into two groups based on whether or not they received a continuous low-dose infusion of lignocaine prior to the study. Group I received the continuous low-dose infusion of lignocaine and group II did not. 3. With a 2 mg/kg lignocaine injection, peak diastolic coronary flow rose significantly in groups I and II by 27 +/- 7 and 29 +/- 7% respectively. This was followed by a significant decline in per cent wall thickening in groups I and II of -11 +/- 2 and -19 +/- 6% respectively. In group I myocardial CP content decreased after lignocaine injection by 58 +/- 6% and ATP tended to rise even though systolic and diastolic pressure did not change significantly. In group II neither CP nor ATP changed significantly, but systolic and diastolic blood pressure decreased significantly. 4. Repeat lignocaine injections were given over a wider dosage range (0.5-4.0 mg/kg) to determine dose-response for lignocaine versus coronary blood flow. Coronary blood flow increased and per cent wall thickening decreased as doses of lignocaine were increased. 5. It was concluded that rapid intravenous lignocaine injection appeared to cause a dose-dependent coronary dilatation and systolic dysfunction. Pre-treatment with low-dose continuous infusion of lignocaine appeared to result in a decrease in CP and a rise in ATP when compared with no pre-treatment--despite a similar effect on myocardial function and coronary blood flow.

Are antiarrhythmic drugs safe?

The indications for antiarrhythmic therapy are far from clearly defined and the choice of treatment is usually based on empiric strategies. Antiarrhythmic agents can have serious side effects. Systemic adverse effects are usually use-related and reversible with withdrawal of the drug. Impairment of left ventricular function is considerable in patients with heart failure. The most important, life-threatening side effect of antiarrhythmic drugs is their proarrhythmic tendency which gives rise to certain concern about their clinical use. Aggravation of arrhythmia often occurs without symptoms, goes unrecognized by the patient, and is exposed only by monitoring, exercise testing, or invasive electrophysiological testing. Patient monitoring with electrolyte measurement, Holter recording, and electrophysiological reassessment can reveal or reduce the proarrhythmic risk but cannot eliminate the problem completely. The institution of antiarrhythmic therapy should be considered in highly symptomatic or life-threatening arrhythmias after careful consideration of the benefit-risk ratio.

Comparative hemodynamic effects of procainamide, tocainide, and encainide in severe chronic heart failure

Many of the newer antiarrhythmic agents are said to cause minimal myocardial depression, but their hemodynamic effects have not been invasively evaluated and compared in patients with severe chronic heart failure. In a randomized, crossover study, the hemodynamic responses to single oral doses of procainamide (750 mg), tocainide (600 mg), and encainide (50 mg) given to 21 patients with severe chronic heart failure were compared. Cardiac performance decreased with all three drugs, but the magnitude of deterioration differed among the three agents. Stroke volume index decreased with procainamide (-5 +/- 1 ml/m2, p less than 0.001), tocainide (-7 +/- 1 ml/m2, p less than 0.001), and encainide (-8 +/- 1 ml/m2, p less than 0.001), but the decline was significantly greater with encainide than with procainamide (p less than 0.05). Similarly, left ventricular filling pressure increased with tocainide and encainide (+4 +/- 1 and +5 +/- 2 mm Hg, respectively; both p less than 0.05), but not with procainamide; the increase was significantly greater with tocainide and encainide than with procainamide (p less than 0.001). These deleterious hemodynamic effects were accompanied by worsening symptoms of heart failure in six patients with encainide and seven patients with tocainide but in only two patients with procainamide. Serum levels for all drugs were in the therapeutic range. In conclusion, although the three type I antiarrhythmic agents tested may all adversely affect left ventricular function in patients with heart failure, encainide and tocainide are more likely than procainamide to cause hemodynamic and clinical deterioration.

Acute effect of lidocaine on coronary blood flow and myocardial function

The acute effects of lidocaine on coronary blood flow, hemodynamic parameters, and wall function were studied in 14 anesthetized pigs. Lidocaine was infused intravenously as a bolus (dosage range from 1.5 to 4.0 mg/kg). At ten to thirty seconds after infusion, coronary blood flow reached 154 +/- 38% (mean +/- SD) of the baseline resting flow (p less than 0.001). The double product, an estimate of myocardial oxygen demand, decreased from a baseline value of 9221 +/- 2174 to 8008 +/- 1923 mmHg beats/min (p less than 0.01). Sixty seconds postinfusion myocardial function decreased from baseline wall thickening of 46 +/- 25% to 41 +/- 17% (p = 0.04). An acute bolus of lidocaine appears to transiently increase coronary blood flow, by decreasing coronary vascular resistance, and also decrease myocardial function. Thus, an acute lidocaine bolus may favorably alter the myocardial oxygen supply/demand ratio.

Effects of intracoronary propranolol on coronary blood flow and regional myocardial function in dogs

The study was conducted to evaluate the effects of intracoronary administration of dl-propranolol on coronary blood flow and regional myocardial function in anesthetized open-chest dogs. The results were compared with those obtained with d-propranolol, atenolol and lidocaine. Bolus intracoronary injections of dl-propranolol (0.02-2 mg) dose dependently produced transient increases in coronary blood flow and subsequent depression in regional segment shortening which qualitatively resembled those produced by the dextro isomer (0.02-2 mg) and lidocaine (0.2-10 mg). Atenolol (up to 2 mg) was almost devoid of these effects. Isoproterenol-induced responses were abolished by dl-propranolol and atenolol but only incompletely blocked by d-propranolol. These results demonstrate that propranolol at high doses has direct coronary vasodilating and cardiodepressant effects in situ, and indicate that the major part of these effects can be attributed to the membrane-stabilizing action rather than beta-adrenoceptor blockade.

Haemodynamic effects of intravenous bupivacaine during high thoracic epidural anaesthesia

Administration of small doses of bupivacaine epidurally at the upper thoracic level will partially block the cardiac sympathetic nerves but not the sympathetic outflow via the adrenals. Local anaesthetics have direct systemic effects on the myocardium and the systemic circulation. The present study aimed to examine the effect of high thoracic epidural anaesthesia (TEA) in elderly patients, and to examine the effect of raising plasma bupivacaine concentrations in these patients, who had earlier had the sympathetic innervation of the heart blocked by thoracic epidural anaesthesia. Fifteen elderly patients scheduled for thoracotomy took part in the study. All received high thoracic epidural anaesthesia including the upper five thoracic dermatomes. When epidural block was established, ten patients received bupivacaine 3 mg/min intravenously for 20 min, while five patients received a corresponding volume of normal saline solution. After TEA was established, heart rate, mean arterial blood pressure and cardiac output decreased. When bupivacaine was given to these patients intravenously during the block, mean arterial blood pressure increased, while cardiac output decreased still more. The mechanisms behind these effects seem to be a direct constriction of the systemic blood vessels and a depressive effect on the myocardium, which was blocked from the influence of the cardiac sympathetic nerves by the high thoracic epidural block.

The effect of intranasally administered nitroglycerin on the blood pressure response to laryngoscopy and intubation in patients undergoing coronary artery by-pass surgery

The effect of intranasally administered nitroglycerin (NTG) on the cardiovascular response to laryngoscopy and intubation was studied. Thirty patients scheduled to undergo coronary artery by-pass surgery under thiopentone, enflurane and pancuronium anaesthesia were randomly divided into three groups. Group I received lignocaine 1.5 mg/kg i.v. prior to laryngoscopy and intubation (control group). Group II received lignocaine 1.5 mg/kg i.v. and in addition 2 mg nitroglycerin (NTG) was given intranasally. Group III received only 2 mg NTG intranasally. In Group I laryngoscopy and intubation caused a significant increase in mean arterial pressure (MAP) (P less than 0.01), heart rate (HR) (P less than 0.01) and rate pressure product (RPP) (P less than 0.01) compared to preoxygenation values. In Group II and III MAP and RPP remained unchanged, whereas HR increased (P less than 0.01 and P less than 0.01 respectively). It can be concluded that intranasally administered NTG effectively attenuates the pressor response to laryngoscopy and intubation in patients presenting for coronary artery by-pass surgery and that it is more effective and convenient method than intravenous lignocaine.

Effect of procainamide on myocardial contractile function and digoxin inotropy

The effect of procainamide and digoxin, singly and together, on peak active force and rate of force development of isolated right ventricular papillary muscles from adult cats was examined. Procainamide (1.5 X 10(-5) M) increased force and rate of force development in each muscle with further increments in performance up to 2.4 X 10(-4) M in most muscles. The maximal increases in force (+/- SEM) averaged 75 +/- 13% above control values. Essentially no response to procainamide was observed when basal levels of contractile state were increased by increasing stimulus frequency or calcium concentrations of the bathing solution. Propranolol (10(-6) M) markedly reduced and verapamil (10(-7) M) abolished the inotropic effect of procainamide. Exposing muscles to procainamide (1.5 or 3 X 10(-5) M) before or after the administration of digoxin (2 or 4 X 10(-7) M) did not alter the inotropic action of either drug. Thus, procainamide in concentrations that are in the therapeutic range in human patients has potent positive inotropic effects that may be masked at high levels of contractile state. This action of procainamide appears to be due to an effect on calcium channels, which in part may be due to beta-adrenergic receptor stimulation. These concentrations of procainamide do not alter the inotropic response to digoxin.

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.

Inhibition of cardiac sympathetic nerve activity during intravenous administration of lidocaine

The antiarrhythmic action of lidocaine has been attributed solely to its direct electrophysiological effects on the heart. However, lidocaine is particularly effective in treating ventricular arrhythmias associated with increased sympathetic activity, e.g., in myocardial infarction and digitalis toxicity. We tested the hypothesis that lidocaine administered intravenously depressed cardiac sympathetic nerve activity (CSNA). We measured CSNA in six dogs in control state and after lidocaine in doses of 0.625, 1.25, and 2.5 mg/kg i.v. over 2 min. These doses of lidocaine produced graded decreases of CSNA of -8 +/- 2, -18 +/- 1, and -41 +/- 5%, respectively (P less than 0.05, mean +/- SE). In six additional experiments the bolus of lidocaine was followed by an infusion for 20 min (1.25 mg/kg followed by 100 micrograms/kg per min and 2.5 mg/kg followed by 200 micrograms/kg per min). Infusion of lidocaine maintained depression of CSNA at a level that was 23 +/- 3 and 35 +/- 5% less than control (P less than 0.05), respectively, at plasma lidocaine levels of 5.2 +/- 0.6 and 7.5 +/- 1.4 micrograms/ml, respectively. CSNA returned to control during recovery periods. CSNA did not decrease with the passage of time or administration of vehicle. In five dogs with vagi intact, carotid sinuses isolated and held at a pressure of 100 mmHg, and aortic baroreceptors denervated, administration of lidocaine (2.5 mg/kg followed by 200 micrograms/kg per min) decreased renal nerve activity to 71 +/- 8% of control. Increases in left ventricular systolic pressure and maximum derivative of pressure with respect to time (dP/dtmax) resulting from electrical stimulation of preganglionic sympathetic nerves were not significantly altered by lidocaine, but were markedly attenuated by hexamethonium, a ganglionic blocker. In conclusion, lidocaine administered intravenously produces dose-dependent and sustained decreases in cardiac sympathetic nerve activity. These decreases can occur with therapeutic plasma levels. We speculate that this effect is due to central nervous system effects of the drug and that this effect may contribute to the antiarrhythmic actions of lidocaine.

Benzyl carbamyl analogue of lignocaine: vasodepressor mechanism of action

1. The benzyl carbamyl analogue of lignocaine [2-(diethylaminoacetamido)-3-carbamyl-4-methyl-5-benzylpyrrole] at an intravenous dose of 4 mg/kg caused a blood pressure decrease of 54 mmHg. 2. A greater hypotensive effect was observed in hypertensive compared to normotensive animals. Anaesthesia magnified the vasodepressor effect in both groups. 3. The analogue did not possess centrally-mediated effects on blood pressure but exerted its hypotensive effect via a peripheral mechanism. 4. The analogue produced a relaxant effect on intestinal and vascular smooth muscle while exerting minimal effects on muscarinic, sympathetic, or ganglionic nicotinic receptors. 5. The analogue exhibited less cardiac depressant action on left ventricular rate (dp/dt) and force of contraction than lignocaine. 6. Lethal effects for the analogue were first observed at 16 mg/kg following intravenous administration and at 500 mg/kg following intraperitoneal administration. 7. In conclusion, the benzyl carbamyl analogue exhibited direct vascular smooth muscle relaxant activity with less cardiac or CNS side effects than lignocaine.

Extracorporeal pump assistance--novel treatment for acute lidocaine poisoning

Accidental bolus administration of lidocaine ranging in dosages from 1000 mg to 2000 mg has caused death in humans. Because lidocaine clearance depends upon hepatic blood flow, drug clearance in a hypotensive overdosed patient is poor so that a drug overdose is likely to be irreversible. Traditional approaches to drug removal include hemodialysis and charcoal hemoperfusion. Neither treatment would be effective for lidocaine overdose because the drug is a myocardial depressant and because the clearance rates of these techniques are 100-200 ml/min. Hepatic clearance of lidocaine is 1000 ml/min in a human with normal cardiac output. We have tested a new concept for removal of high clearance drugs that are associated with myocardial depression. Cardiac bypass support was used in a dog experiment to demonstrate that restoration of cardiac output could restore high clearance of lidocaine. Sixteen anesthetized dogs were given 30 mg/kg boluses of lidocaine. In one group of eight dogs, toxicity was treated with antiarrhythmic drugs, pressor drugs and cardioversion. Six out of eight of these animals died within 30 min after lidocaine infusion. In the second group of eight dogs, an extracorporeal bypass pump was used for 90 min after the lidocaine injection. None of these assisted animals died. Drug clearance in dogs treated with the extracorporeal pump was compared to drug clearance in eight dogs that received non-toxic lidocaine doses of 3 mg/kg. Drug clearance was 39.75 +/- 4.16 ml/kg/min in the overdosed animals compared to 38.29 +/- 8.6 ml/kg/min in the non-toxic animals. Thus, drug clearance was normal in dogs treated with the extracorporeal pump. These experiments suggest that short-term support of the circulation with an extracorporeal pump could theoretically be effective in reducing patient mortality from acute massive lidocaine overdose.

Hemodynamic effects of n-acetylprocainamide compared with procainamide in conscious dogs

We examined the hemodynamic actions of clinically relevant i.v. doses (20 mg/kg and 10 mg/kg) of n-acetyl procainamide (NAPA) in conscious dogs preinstrumented with a left ventricular (LV) micromanometer, LV and aortic catheters, and ultrasonic crystals for measurement of LV internal diameter shortening (% delta D). Within 30 seconds after the 20-mg/kg dose, there were significant increases in heart rate (27 +/- 7 beats/min, mean +/- SEM; n = 6), maximum dP/dt (655 +/- 206 mm Hg/sec), and % delta D (2.2 +/- 0.9%; all p less than or equal to 0.05). However, by 6 hours after the dose there were reductions compared with control in peak LV pressure (19 +/- 9 mm Hg), dP/dt (610 +/- 210 mm Hg/sec), and % delta D (2.3 +/- 0.6%; all p less than or equal to 0.05). In contrast, equimolar doses of procainamide or drug vehicle alone evoked no response, as did NAPA after pretreatment with reserpine (0.25 mg/kg/day for 2 days) or hexamethonium (10-15 mg/kg). These data suggest NAPA produces a biphasic hemodynamic response with enhancement of LV performance early and a decrease later; this response is different from that of the parent compound, procainamide. These effects are likely mediated by the adrenergic nervous system at either a ganglionic or a central level.

The effects of bupivacaine and chloroprocaine as local anesthetics for epidural anesthesia of fetal heart rate monitoring parameters

The effects of saline-induced pressure-volume changes in the epidural space, and bupivacaine and chloroprocaine as local anesthetics for epidural anesthesia, on various fetal heart rate monitor parameters were investigated in 34 low-risk women. Epidural space pressure-volume changes, bupivacaine, and chloroprocaine had no effect on the incidence of pathologic periodic fetal heart rate changes, the level of the baseline fetal heart rate, or the level of uterine activity units. Epidural space pressure-volume changes and chloroprocaine did not affect fetal heart rate variability. The use of bupivacaine was associated with a significant increase in fetal heart rate variability

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.

Lidocaine increases prostacyclin in the rat

In the rat, the effect of intravenous lidocaine was evaluated on plasma prostacyclin concentration as well as the concentration of prostacyclin in aortic ring incubation chambers and in the effluent of isolated perfused lungs. Prostacyclin was assayed using a radioimmunoassay for its stable product 6-Keto PGF1 alpha. Lidocaine in therapeutic doses (2 mg/kg) will significantly increase 6-Keto PGF1 alpha in plasma as well as in aortic ring incubation chambers and in the effluent of isolated perfused lungs when compared to saline treated controls.

A preclinical study of EO-122, a new lidocaine-like antiarrhythmic drug

The 2,6-dimethylanilide of quinuclidine-3-carboxylic acid hydrochloride (EO-122), a new structural analog of lidocaine, has been shown to possess potent antiarrhythmic activity in experimentally induced arrhythmias in animals. Restoration of normal sinus rhythm and suppression of ouabain-induced arrhythmia in cats and dogs, and of coronary occlusion-induced arrhythmia in dogs, followed a single IV injection of 1--3 mg/kg, with an onset of 2 minutes and a duration of 20--240 minutes. Occlusion-induced arrhythmia was likewise suppressed after an oral dose of 10--20 mg/kg, with an onset of 11--65 minutes and a duration of 25--120 minutes. Under similar conditions, lidocaine was either totally ineffective or of ultra-short duration. The bioavailability of EO0122 by the oral route exceeded 80% of the oral dose. Therapeutic blood concentrations were in the range 0.5--7 microgram/ml. At about 5 microgram/ml there was a slight depression of cardiac function in the anesthetized cat, but not in the conscious dog. In cats, complete A-V block occurred at concentrations of 60--70 microgram/ml. The IV LD50 in mice was 22 mg/kg, and in rabbits 8.5 mg/kg. No overt signs of neurotoxicity could be observed at any dose of EO-122. The pharmacokinetic profile of the drug fits a two-compartment open model, with t1/2 congruent to 150 min and Vd (SS) congruent to 1.5 l/kg.

The Swan-Ganz pulmonary artery catheter. Incidence of complications, with particular reference to ventricular dysrhythmias, and their prevention

A series of seventy-three adult patients undergoing open-heart surgery was studied, in whom a Swan-Ganz pulmonary artery catheter was inserted. The incidence of complications occurring during insertion and use of the catheter was noted, and a controlled trial carried out to determine the efficacy of lignocaine 1 mg/kg iv in preventing ventricular dysrhythmias during passage of the catheter. A significant decrease in dysrhythmia rate was observed. Ways of minimising or preventing other complications are discussed.

Comparative antiarrhythmic efficacy of intravenous N-acetylprocainamide and procainamide

Ten patients with persistent ventricular arrhythmia were studied in a comparison of the antiarrhythmic efficacy of N-acetylprocainamide (NAPA) and procainamide (PA). Each patient performed three exercise tests for 40 min., on different days, with submaximal and fixed work loads. During the first exercise test no drug was administered. During the following two tests PA and NAPA, respectively, were administered by intravenous infusion. The electrocardiogram was continously recorded and was analyzed minute by minute. Blood samples for determination of plasma drug concentration were frequently collected. Exercise alone did not significantly change the incidence of arrhythmia. Both PA and NAPA showed a similar and significant antiarrhythmic effect. A blood pressure fall was seen in two patients after administration of each drug. No other adverse reaction was observed.

Effects of tocainide on left ventricular performance at rest and during acute alterations in heart rate and systemic arterial pressure. An echocardiographic study

Images

Sympathetic nervous system response to lidocaine induced seizures in cats

The effect on arterial pressure, EEG, preganglionic sympathetic nervous activity and pulse rate of repeated intravenous administrations of lidocaine (3 mg/kg) was investigated in cats anaesthetized with nitrous oxide. A continuous high voltage, burst-suppression EEG indicating constant seizure activity was found, whereas arterial pressure and sympathetic nervous activity did not change significantly. Although the onset of EEG seizure activity did not change the mean sympathetic activity level, the pattern of firing changed dramatically as every EEG seizure triggered a burst of sympathetic impulses. Barostatic reflexes were active after lidocaine administration unless seizure activity occurred. Thiopental 5 mg/kg given intravenously to cats during continuous lidocaine-induced EEG seizures always abolished the seizure activity without excessive depression of arterial pressure.

Myocardial function and coronary blood flow response to acute ischemia in chronic canine diabetes

To examine the influence of preexistent diabetes mellitus on left ventricular performance and coronary blood flow responses to acute ischemia, mild normoglycemic diabetes was induced in nine mongrel dogs after three doses of alloxan, (20 mg/kg, iv), at monthly intervals. Hemodynamic measurements and coronary blood flow (85Kr clearance) were obtained before and after the onset of ischemia. This was produced by occlusion of the proximal left anterior descending coronary artery via a balloon-type catheter in nine intact anesthetized diabetic dogs and 10 nondiabetic dogs. During the 1st hour of ischemia in the diabetic group, the end-diastolic pressure rose from 7 +/- 1.1 (mean +/- SE) mm Hg to 23.8 +/- 2.3 without a significant increase of end-diastolic volume. In controls end-diastolic pressure rose from 8.6 +/- 1.1 mm Hg to 15.3 +/- 1.4, and end-diastolic volume was significantly increased, so that the ratio of end-diastolic pressure and volume was significantly higher in the diabetic group (P less than 0.005). Although indices of contractility did not differ, stroke volume and work reductions were significantly greater in diabetics, despite the fact that coronary blood flow was reduced to a similar extent. Size of the ischemic areas appeared comparable as judged by distribution of dye injected distal to the occlusion. Since potassium loss and sodium gain in the inner and outer layers of ischemic tissue did not differ between the two groups, the intensity of ischemia seemed similar. Glycogenolysis was unimpaired in the diabetic ischemic muscle but triglyceride levels remained elevated. Morphologically the diabetic myocardium was characterized by a diffuse accumulation of periodic acid-Schiff-positive glycoprotein in the interstitium, which was thought to limit diastolic filling of the ischemic ventricle and to contribute to the substantial reduction of ventricular performance.

Human hepatic blood flow and its relation to systemic circulation during intravenous infusion of lidocaine

Twelve healthy young volunteers were studied before and during intravenous administration of lidocaine at a dose rate of 2 or 4 mg/min. Five additional volunteers, who did not receive lidocaine solution but were given the same amount of physiological saline, were studied in the same manner. Heart rate, cardiac output, mean arterial blood pressure, mean right atrial blood pressure, estimated hepatic blood flow and plasma concentration of lidocaine were measured repeatedly. The results showed an increase in heart rate, cardiac output and mean arterial blood pressure, the latter two variables in relation to the plasma concentration of lidocaine. The estimated hepatic blood flow increased, partly as a result of the reduction of splanchnic vascular resistance and partly due to the stimulation of cardiac output. The decrease in splanchnic vascular resistance was proportional to the plasma concentration of lidocaine.

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

The effect of administration of lidocaine on left ventricular performance was studied using systolic time intervals in nine normal subjects, eight patients with stable angina, and 15 patients with acute myocardial infarction. The greatest response in systolic time intervals occurred at three minutes after intravenous injection of lidocaine (100 mg), with values returning to baseline at 10 to 15 minutes. Administration of lidocaine produced a significant prolongation of the preejection period (PEP) corrected for heart rate in all groups and a prolongation of the ratio of PEP to left ventricular ejection time (PEP/LVET) in patients with angina. The group with acute myocardial infarction exhibited a hyperadrenergic state, as shown by a short baseline QS2I. The QS I was lengthened by administration of lidocaine in all groups, but this was more profound in those with acute myocardial infarction. These changes in systolic time intervals were still present at two hours after injection in six patients with acute myocardial infarction in whom an infusion of lidocaine followed the initial bolus. The effect of administering lidocaine after intravenous injection of propranolol (5 mg) was also studied in six normal subjects. Although propranolol therapy along prolonged the PEP/LVET, a further significant prolongation followed subsequent injection of lidocaine.

Cardiovascular reactions to laryngoscopy and tracheal intubation following small and large intravenous doses of lidocaine

The efficacy of intravenously administered lidocaine 0.75 mg/kg and 1.5 mg/kg to protect against cardiovascular reactions associated with laryngoscopy and tracheal intubation was studied in two comparable groups of ten patients and compared with a similar control group of ten patients given only saline. Following laryngoscopy and tracheal intubation, the 1.5 mg/kg dose afforded complete protection against cardiac arrhythmias of all types. The smaller dose was ineffectual in this respect. While the larger dose caused borderline protection against hypertension and tachycardia, the smaller dose prevented only the rise in systolic blood pressure. Possible mechanisms to account for these observations are discussed. These include a direct myocardial depressant effect, a central stimulant effect, a peripheral vasodilating effect and finally an effect on synaptic transmission.

Haemodynamic effects of procainamide and phenytoin at apparent therapeutic plasma levels

The haemodynamic effects of procainamide and phenytoin after intravenous administration to 19 patients with suspected congenital heart lesions were studied. The drugs were injected into the pulmonary artery in a dose of 5 mg per kg bodyweight, at an infusion rate of 50 mg per minute, thus giving plasma concentrations within the suggested therapeutic ranges. The diastolic pressures in the pulmonary artery and the right ventricle were reduced by procainamide and the converse effect was noted after phenytoin. The heart rate was significantly increased by both drugs but with phenytoin this effect was only transitory. The latter drug also caused a small and transient fall in cardiac output and mean arterial pressure. It was concluded that of the two drugs phenytoin seemed to have the most marked myocardial depressant effect.

Comparison of the coronary collateral circulation in dogs and baboons after coronary occlusion

The relevance to man of experimental observations on coronary collateral blood flow (CCBF) in dogs has been questioned. The effect of 2 to 3 hour coronary occlusions in the anesthetized dog and a primate, the baboon, were therefore compared, with CCBF measured by injections of 85Kr distal to occlusion with precordial counting. Before killing, additional isotope was infused to compare inner/outer wall flow distribution and myocardial tissue samples were analyzed for electrolyte content. Effects of nitrates on hemodynamics and metabolism were also compared in dog and baboon. Similar values for CCBF and resistance following occlusions were found in dog and baboon (flow approximately 25 per cent control, calculated resistance increase four- to sevenfold). Greater subendocardial ischemia in both species was indicated by isotope distribution less to the inner wall, but electrolyte changes (k+ less and Na+ greater in the ischemic area compared to nonischemic) were similar transmurally in both species. Hemodynamic responses to nitrate infusion (isosorbide dinitrate) were similar, with increase in CCBF and decrease in resistance. In neither group were inner/outer wall isotope distribution or electrolyte changes influenced by nitrate. The coronary collateral response to occlusion is similar in dog and baboon in terms of both hemodynamics and metabolic changes. After 2 to 3 hours of coronary occlusion some hemodynamic benefit may be demonstrated with nitrates but no metabolic advantage, at least in the central area of ischemia.

Comparative effects of lidocaine and procainamide on acutely impaired hemodynamics

Controversy exists regarding the relative safety of intravenously administered lidocaine and procainamide to patients with acutely impaired hemodynamics. Accordingly, their effects were studied in 15 such patients, 14 with acute myocardial infarction and one with cardiomyopathy and severe congestive heart failure. All had elevated levels of pulmonary capillary wedge pressure (greater than 15 mm Hg) and/or low cardiac index (less than 2.5 liters/min/m2). Patients were given lidocaine, a 100 mg bolus followed by a 3 mg/min infusion and, after at least a 30 minute recovery period, procainamide, a 100 mg bolus over 2 minutes followed by a 20 mg/min infusion for 20 to 25 minutes. Hemodynamic measurements were compared early and late in the infusion of each drug. Small, clinically insignificant differences were observed in the hemodynamic responses to the drugs, and no clinically significant deterioration occurred with either. Conventional therapeutic doses of intravenous procainamide can be administered by this regimen, to patients with acute myocardial infarction complicated by cardiac failure or low cardiac output, without producing deleterious hemodynamic effects.

Hemodynamic consequences of cardiac dysrhythmias

To understand the hemodynamic changes produced by arrhythmias is to understand cardiovascular physiology. The changes in rate are accompanied by changes in contractility, receptor stimulation, peripheral vascular response, and flow to other vital organs. In addition, one must keep in mind the underlying pathology of the cardiovascular system. As a therapeutic program is initiated and adjusted, it must be done in accordance with the changes produced in the hemodynamics as well as the rhythm.

Antiarrhythmic, haemodynamic and metabolic effects of 3alpha-amino-5alpha-androstan-2beta-ol-17-one hydrochloride in greyhounds following acute coronary artery ligation

1 The antiarrhythmic, haemodynamic and metabolic effects of a new amino steroid, ORG6001, have been investigated in experimental acute myocardial infarction in anaesthetized greyhounds. 2 ORG6001 administered either intravenously (2-10 mg/kg) or orally (50 mg/kg) significantly reduced the incidence of ventricular ectopic beats in the first 30 min after ligation of the left anterior descending coronary artery. 3 In dogs pretreated with ORG6001, metabolic changes indicative of myocardial ischaemia (lactate production and potassium efflux) were less marked than those occurring in control animals. 4 Antiarrhythmic doses of ORG6001 caused only minimal transient haemodynamic effects. 5 These results suggest that ORG6001 may possess distinct advantages over presently-used antiarrhythmic drugs in the prevention and treatment of the early arrhythmias which occur after myocardial infarction.

Effects of N-acetylprocainamide as compared with procainamide in isolated rat atria

The actions of procainamide and its major metabolite N-acetylprocainamide were tested and compared on isolated rat atria. While procainamide exerted a negative chronotropic and iontropic effect, N-acetylprocainamide had the opposite effect. It is suggested that a N-acetylprocainamide-induced increase in myocardial work can counteract the negative inotropic action of procainamide and thus to some extent explain the variable results with the latter compound on myocardial performance reported from in vivo experiments. Procainamide increased the refractory period and reduced the excitability of isolated rat atria. N-acetylprocainamide, on the other hand, caused negligible effects on these parameters.

The effect of lidocaine on peripheral hemodynamics

Lidocaine was given in increasing step-wise dose concentrations of 1, 2, 3, 4, and 5 mg/minute and the resulting serum concentrations correlated with the effect of this agent on the peripheral vasculature of seven patients. Lidocaine infusion causes an immediate sustained increase in mean calf venous capacitance but little effect on mean diastolic blood pressure. In high concentration levels this agent causes an increase in mean calf blood flow and systolic blood pressure. Its effect on calf vascular resistance is variable, but there is a tendency to reduce resistance, particularly at a high concentration level. The effect of lidocaine infusion rate on serum lidocaine levels was such that the greater the infusion rate, the higher the resultant serum lidocaine levels.

Ischemic heart failure: sustained inotropic response to small doses of I-epinephrine without toxicity

As a prelude to a study of severe ischemic heart failure, the therapeutic response of the ischemic ventricle to epinephrine and acetylstrophanthidin in nontoxic doses was determined in 24 intact anesthetized dogs undergoing a first episode of acute regional ischemia. A thrombotic obstruction was produced in the left ventricular dysfunction. The elevation of end-diastolic pressure and reduced stroke volume in control dogs were not significantly altered by administration of strophanthidin. Epinephrine (0.05 mug/kg per min) elicited a significant reduction in end-diastolic pressure and increase in stroke volume. The latter was not attended by an increased incidence of ventricular fibrillation, whereas fibrillation occurred in half of the group given strophantihidin. Thus, the catecholamine was selected to study pump failure. Severe ischemic heart failure was assessed in two groups with scar from previous infarction for up to 4 hours. By 60 minutes of ischemia the increase in end-diastolic pressure and volume and decrease in stroke volume and ejection fraction were comparable in both groups. Thereafter, alternate animals received small doses of epinephrine (0.05 to 0.15 mug/kg per min) with graded increments at 60 minute intervals to counter tachyphylaxis and findings were compared with those in control dogs. Over the subsequent 3 hours, there was progressive deterioration of left anterior descending coronary artery, affecting ventricular function in the untreated group with an increase in end-diastolic pressure from 10 plus or minus 1 to 33 plus or minus 2.4 mm Hg. End-diastolic volume increased by 63 percent; stroke volume and ejection fraction decreased by 48 and 66 percent, respectively. The infusion of epinephrine was attended by a significantly lower end-diastolic pressure of 20 plus or minus 2.5 mm Hg, whereas end-diastolic volume, stroke volume and ejection fraction were restored to control levels after 4 hours of ischemia. Mortality in the untreated group was 62 percent by 4 hours; all seven animals in the treated group survived.