Cocaethylene is as cardiotoxic as cocaine but is less toxic than cocaine plus ethanol

Cocaethylene is a pharmacologically active cocaine metabolite that is produced in the liver by the transesterification of cocaine only in the presence of ethanol. The acute cardiovascular effects of cocaethylene are not known. We compared the acute cardiovascular effects of cocaethylene with cocaine and with cocaine plus ethanol in 18 dogs. We administered cocaethylene 7.5 mg/kg to 6 dogs, cocaine 7.5 mg/kg to 6 dogs, and cocaine 7.5 mg/kg plus ethanol 1 gm/kg to 6 dogs. The dose of each drug was chosen to produce in dogs the concentrations of cocaethylene or cocaine that have been measured in patients who have experienced cardiotoxic reactions to cocaine or cocaine plus ethanol. Arterial, left ventricular (LV), pulmonary artery wedge pressures (PAWP), the maximum rate of LV pressure rise [(dP/dt)max] and fall [(dP/dt)min], and heart rate (HR) were continuously measured. Stroke volume was determined 3 times during the first hour after drug administration then hourly for four hours. The concentrations of cocaethylene and cocaine peaked in the serum at 3717 +/- 651 ng/ml and 4140 +/- 459 ng/ml, respectively, two minutes after each bolus. The median half-life of cocaethylene was 144.3 minutes whereas the median half-life of cocaine was 96.7 minutes (p < 0.01). Cocaethylene maximally decreased (dP/dt)max by 44%, (dP/dt)min by 29%, and stroke volume by 28% (all p < 0.01) and increased the PAWP by 50% (p < 0.02) and the HR by 13% (p = NS) during the first hour. Cocaine maximally decreased (dP/dt)max by 40%, (dP/dt)min by 31%, and the stroke volume by 26% and increased the PAWP by 100% and the HR by 46% (all p < 0.01) during the first hour. Ethanol plus cocaine maximally decreased (dP/dt)max by 68%, (dP/dt)min by 78% and the stroke volume by 49% and increased the PAWP by 118% and the HR by 74% (all p < 0.01) during the first hour. In this last group, (dP/dt)max and stroke volume remained depressed by approximately 20% (p < 0.01) for five hours. We conclude that cocaethylene is as toxic as cocaine to the myocardium but is less toxic than ethanol plus cocaine.

Cocaethylene causes dose-dependent reductions in cardiac function in anesthetized dogs

Twelve million Americans abuse both cocaine and ethanol each year because this drug combination produces a pronounced and prolonged euphoria. However, these substances in combination are substantially more toxic than either drug alone. This toxicity may be due to cocaethylene, which has been detected in the serum of patients who have used cocaine and ethanol and two require emergency treatment. Cocaethylene is a pharmacologically active cocaine metabolite formed in the liver only in the presence of ethanol. To investigate the cardiovascular effects of cocaethylene, we randomized 15 mongrel dogs to receive 11.25 mg/kg (n = 4), 7.5 mg/kg (n = 6), or 3.75 mg/kg (n = 5) of cocaethylene as an intravenous (i.v.) bolus. These doses were chosen to achieve serum concentrations of cocaethylene consistent with those observed in patients with cocaine and ethanol toxicity. The ECG and the femoral arterial, left ventricular (LV), and pulmonary artery pressure were measured continuously, and cardiac output (CO) and serum levels of cocaethylene were monitored at specific intervals before and after drug administration. The maximal rate of increase and decrease in LV pressure (LVP), i.e., (dP/dt)max and (dP/dt)min, were determined as our indexes of ventricular contractility and relaxation. Cocaethylene concentrations peaked 2-4 min after each bolus and then decreased in a curvilinear manner. Cocaethylene's half-life (t1/2) was 150 +/- 15.1 min (mean +/- SEM). The greatest hemodynamic changes occurred at the peak cocaethylene serum concentrations in each group. In comparison with control measurements, cocaethylene in concentrations of 11.25 and 7.5 mg/kg decreased (dP/dt)max by 81 and 43% and decreased (dP/dt)min by 80 and 36%, respectively. In these two groups, cocaethylene decreased stroke volume (SV) by 29 and 33% and reduced mean arterial pressure (MAP) by 65 and 30%, respectively. Cocaethylene increased pulmonary artery wedge pressure (PAWP) by 70 and 67% in the 11.25- and 7.5-mg/kg groups. These hemodynamic changes persisted for 60 min after the bolus administration. In each of the three groups, cocaethylene increased the QRS interval duration by 60, 32, and 44% and the QTc interval by 38, 21, and 17%. These ECG changes persisted for 120 min. These experiments suggest cocaethylene depresses the myocardium. Cocaethylene may be a major contributor to the delayed but substantial cardiotoxicity that occurs in individuals who use both cocaine and ethanol.

Cocaine plus ethanol is more cardiotoxic than cocaine or ethanol alone

OBJECTIVES

The purpose of this study was to determine the hemodynamic effects of recreational/toxic doses of ethanol, or cocaine, or ethanol followed by cocaine.

DESIGN

Prospective, randomized study.

SETTING

University research laboratory.

SUBJECTS

Eighteen healthy, adult mongrel dogs.

INTERVENTIONS

Dogs were randomized to receive ethanol (1 g/kg iv) over 20 mins and a 10-mL bolus of 0.9% sodium chloride, or 5% dextrose in water, over 20 mins, and then a cocaine bolus (7.5 mg/kg), or ethanol (1 g/kg iv), over 20 mins, and then a cocaine bolus (7.5 mg/kg).

MEASUREMENTS AND MAIN RESULTS

Arterial, left ventricular, and pulmonary arterial pressures, mixed venous blood oxygen saturation, and heart rate (HR) were continuously recorded in each dog. The maximal rate of left ventricular pressure increase (dP/dtmax) and decrease (dP/dtmin), stroke volume, HR, pulmonary artery occlusion pressure (PAOP), and plasma concentrations of ethanol and cocaine were measured at baseline, after ethanol or placebo infusions, and then after a cocaine or placebo bolus at specific time intervals over a 5-hr study period. The plasma ethanol concentration increased to 160 +/- 8 mg/dL at 30 mins after the start of the infusion, and then decreased to 30 +/- 8 mg/dL at 180 mins. The plasma cocaine concentration increased to 4587 +/- 383 ng/mL within 2 mins of the bolus injection, and then decreased and approached the baseline at 240 mins. Immediately after injection, ethanol plus cocaine synergistically decreased dP/dtmax by 70% and dP/dtmin by 81% (both p < .001). In addition, immediately after injection, ethanol plus cocaine maximally decreased the stroke volume by 34% (p < .05) and maximally increased the HR by 89% and PAOP by 127% (both p < .002). The dP/dtmax and the stroke volume remained decreased by 15% to 20% for 5 hrs (p < .05). Cocaine alone, immediately after injection, maximally decreased dP/dtmax and dP/dtmin by 40% (p < .02), and caused a 26% decrease in stroke volume (p = .05), a 48% increase in HR (p < .02), and a 75% increase in PAOP. The decrease in dP/dtmax persisted for approximately 60 to 90 mins. Ethanol alone produced transient 6% to 13% decreases in dP/dtmax, dP/dtmin, and stroke volume (NS) and small (9%) increases in the HR (NS) during the first hour after injection.

CONCLUSION

Cocaine combined with ethanol produces a significant synergistic depression of ventricular contraction and relaxation that substantially exceeds the arithmetic sum of the depressive effects of either cocaine or ethanol alone.

Oxygen transport variables in the identification and treatment of tissue hypoxia

Critically ill patients have greater than normal oxygen demands because of enhanced energy requirements placed on them by the stress of acute illness, blood and fluid loss, surgery, wound healing, and hospitalization. Early recognition of major alterations in oxygen transport variables, oxygen delivery, oxygen consumption, and the oxygen extraction ratio, by the critical care team assists in the prevention and treatment of tissue hypoxia in seriously ill and injured patients. Supranormal levels of oxygen delivery are required to meet these increased oxygen demands, to prevent tissue hypoxia, and to correct tissue oxygen debt. The critical care team should promptly determine the patient's oxygen transport variables on admission to the intensive care unit to provide a starting point for patient resuscitation. When deviations from supranormal values of oxygen transport variables in these patients are identified, specific interventions that improve oxygen delivery to peripheral tissues should be implemented and evaluated for their effectiveness in normalizing the oxygen extraction ratio. When serial measurements of oxygen delivery, oxygen consumption, and the oxygen extraction ratio follow each therapeutic intervention that is directed at increasing oxygen delivery, the survival rate of critically ill patients is significantly improved.

Cocaine significantly impairs myocardial relaxation

OBJECTIVES

To determine the immediate effects of intravenous "recreational" doses of cocaine on myocardial ventricular relaxation and contraction and on coronary blood flow. To determine the cardiac effects of cocaine after the administration of propranolol, as propranolol has been used to limit the cardiovascular effects of cocaine.

DESIGN

Prospective study.

SUBJECTS

Twenty mongrel dogs.

INTERVENTIONS

We continuously recorded central aortic pressure, left atrial and ventricular pressures, coronary artery blood flow, and electrocardiograms in each dog. We determined from the left ventricular pressure waveforms the maximum rate of pressure increase [(dP/dt)max] and the time constant of isovolumic ventricular relaxation as our indices of ventricular contraction and relaxation.

MEASUREMENTS AND MAIN RESULTS

In our initial series of experiments, we obtained pressure, coronary artery blood flow, and electrocardiographic recordings in ten anesthetized dogs before and for 40 mins after the intravenous administration of cocaine, in doses of 2.5 and then 5 mg/kg. In our second series of experiments in ten additional dogs, we injected 0.5 mg/kg of propranolol intravenously 30 mins before the injection of cocaine (2.5 mg/kg), and obtained hemodynamic and electrocardiographic recordings before and for 40 mins after the injection of propranolol and cocaine. Cocaine, 2.5 mg/kg, abruptly increased the time constant of isovolumic ventricular relaxation from 22.9 +/- 1.2 to 29 +/- 2.2 msecs at 1 min (p < .05) and to 35.3 +/- 2 msec at 40 mins (p < .01) but did not significantly change the mean arterial pressure, left atrial pressure, heart rate, coronary blood flow, or the maximum rate of left ventricular pressure increase [(dP/dt)max]. Cocaine also progressively displaced the electrocardiographic ST segments by 3.2 +/- 0.6 mm (p < .01) over 40 mins. Cocaine, 5 mg/kg, rapidly increased the time constant of isovolumic ventricular relaxation from 28.5 +/- 2.5 to 41 +/- 3 msecs in 1 min (p < .05) and to 48.7 +/- 4 msecs at 40 mins (p < .01) and reduced (dP/dt)max from 2905 +/- 370 to 1422 +/- 121 mm Hg/sec at 1 min (p < .01); (dP/dt)max returned to 2351 +/- 415 mm Hg/sec during the next 39 mins. Cocaine did not significantly change either the mean arterial or left atrial pressures. However, this dose of cocaine did decrease, over 40 mins, the heart rate from 184 +/- 11 to 139 +/- 11 beats/min (p < .01) and reduced coronary blood flow by 20% (p < .01). Cocaine also displaced the electrocardiographic ST segments by 3.3 mm over 40 mins (p < .05). Cocaine and propranolol abruptly increased the time constant of isovolumic ventricular relaxation from 26.4 +/- 1.3 to 43.2 +/- 2.1 msecs (p < .01) at 1 min and to 46.8 +/- 1.5 msecs at 3 mins (p < .01). The time constant of isovolumic ventricular relaxation remained abnormally increased at 43.0 +/- 1.4 msecs at 40 mins. Cocaine and propranolol reduced (dP/dt)max from 2760 +/- 458 mm Hg/sec to a minimum value of 1400 +/- 119 mm Hg/sec at 2 mins (p < .01). However, (dP/dt)max then returned to 2201 +/- 359 mm Hg/sec during the next 38 mins. Cocaine and propranolol did not significantly change the mean arterial and left atrial pressures, or heart rate, but did reduce coronary blood flow, over 40 mins, by 25% (p < .001). Cocaine also maximally displaced the electrocardiographic ST segments by 1 +/- 0.2 mm (p < .01).

CONCLUSIONS

Cocaine substantially impairs myocardial ventricular relaxation for periods of at least 40 mins. Propranolol significantly intensifies cocaine's depressant effect on ventricular relaxation.

Vagal stimulation during muscarinic and beta-adrenergic blockade increases atrial contractility and heart rate

We determined the effects of continuous cardiac vagal nerve stimulation on atrial contractility and on heart rate in mongrel dogs in which we blocked the muscarinic and beta-adrenergic receptors. Each dog received atropine, 0.5 mg/kg and propranolol, 0.5-1 mg/kg. We stimulated the cardiac vagus nerves in each dog for three separate 5-min periods at frequencies of 0 (control), 20, and 40 Hz (5 ms, 15 V) and measured the changes in atrial contractility and heart rate. Vagal nerve stimulation increased right atrial contractility from the control value by 27% at 20 Hz and by 19% during stimulation at 40 Hz (P < 0.001). Vagal nerve stimulation also increased the heart rate from 114 +/- 5 beats/min during the control period to 146 +/- 10 beats/min (P < 0.01) during stimulation at a frequency of 20 Hz and to 140 +/- 11 beats/min (P < 0.05) during stimulation at 40 Hz. Injection of the vasoactive intestinal peptide (VIP) antagonist, [4Cl-D-Phe6,Leu17]VIP, directly into the dog right coronary artery in concentrations of 0 (control), 2, and 4 micrograms/kg did not influence spontaneous atrial contractility or the heart rate. However, 4 micrograms/kg of the VIP antagonist significantly reduced the augmentation in right atrial contractility and the increase in heart rate during vagal nerve stimulation. Our experiments suggest that cardiac vagal nerve stimulation, during muscarinic and beta-adrenergic receptor blockade, releases VIP or a 'VIP-like substance', that significantly augments atrial contractility and increases heart rate.

Effects of autonomic nerve stimulation, asynchrony, and load on dP/dtmax and on dP/dtmin

We studied asynchronous depolarization effects on mechanical responses to autonomic nerve stimulation (ANS) in 21 dogs with AV nodal block. In 11 of these dogs, we kept mean aortic pressure (AoP) at 85 mmHg and paced the hearts at 120 beats/min. We paced, in random order, either the LV apex or the RV anterior or lateral wall to increase the asynchrony of ventricular contraction and relaxation. During pacing at each site, we determined maximum rate of LVP rise (dP/dtmax) and fall (dP/dtmin) before and during stimulation of cardiac sympathetic and vagal nerves and during combined nerve stimulation. Changing the pacing site from LV to RV decreased dP/dtmax and also dP/dtmin (P less than 0.001); the decrease was most pronounced when we shifted pacing from LV apex to RV anterior wall. Sympathetic stimulation increased (P less than 0.0001) and vagal stimulation decreased (P less than 0.001) dP/dtmax and dP/dtmin during pacing at each site. Effect of vagal stimulation was substantially enhanced during concomitant sympathetic stimulation. However, the magnitude of changes in dP/dtmax and also in dP/dtmin due to nerve stimulations during pacing at each ventricular site was similar. In 10 additional dog experiments, we also varied AoP from a mean value of 74 to 113 mmHg during pacing at each site. An increase in AoP augmented dP/dtmax by a mean value of 582 mmHg/s and increased dP/dtmin by a mean value of 617 mmHg/s (both P less than 0.0001). Sympathetic stimulation increased, whereas vagal stimulation decreased, dP/dtmax and dP/dtmin at each afterload (P less than 0.001).

Vagal stimulation attenuates sympathetic enhancement of left ventricular function

We studied the effects of stimulation of the vagal and sympathetic cardiac nerves on left ventricular contraction and relaxation in 16 anesthetized dogs. In each experiment, we paced the ventricles at a fixed rate of 120 beats/min, and we kept the systemic arterial pressure constant. We used the maximum rates of left ventricular pressure rise (dP/dtmax) and fall (dP/dtmin) as our indexes of ventricular contraction and relaxation. Sympathetic nerve stimulation at a frequency of 6 Hz increased dP/dtmax by 802 mmHg/s and raised dP/dtmin by 847 mmHg/s above the control level. The effect of vagal nerve stimulation was directly dependent on the level of sympathetic stimulation. In the absence of sympathetic stimulation, vagal nerve stimulation at a frequency of 5 Hz decreased dP/dtmax by 187 mmHg/s and reduced dP/dtmin by 199 mmHg/s below the control level. When the sympathetic stimulation was 6 Hz, vagal nerve stimulation at 5 Hz decreased dP/dtmax by 513 mmHg/s and reduced dP/dtmin by 709 mmHg/s. Furthermore, propranolol, in doses of 1.5 mg/kg, abolished any significant vagal effect on ventricular contraction or relaxation. We conclude that combined sympathetic-vagal stimulation results in a substantial antagonistic interaction such that vagal stimulation significantly attenuates the sympathetic enhancement of left ventricular function.

Autonomic nervous stimulation affects left ventricular relaxation more than left ventricular contraction

We studied the effects of stimulation of the vagal and also the sympathetic efferent cardiac nerves on left ventricular (LV) relaxation and contraction in 11 anesthetized, open-chest dogs. In each dog, we paced the ventricles at a fixed rate of 120 beats.min-1 and kept the systemic arterial pressure constant. The maximum rate of LV pressure decline, (dP/dt)min, and the time constant of LV isovolumic pressure decline, tau, were used as our indexes of LV relaxation. The maximum rate of LV pressure rise, (dP/dt)max, was used as our measure of LV contractility. Vagal stimulation decreased (dP/dt)min more than (dP/dt)max (P less than 0.01) when examined at frequencies that ranged from 2 to 12 Hz. Vagal stimulation at 12 Hz reduced (dP/dt)min by 26% (P less than 0.001) and increased tau by 57% (P less than 0.0001) but decreased (dP/dt)max by only 20%. Sympathetic stimulation, at frequencies that ranged from 2 to 12 Hz, increased (dP/dt)min more than (dP/dt)max (P less than 0.001). Sympathetic stimulation at 12 Hz increased (dP/dt)min by 130% (P less than 0.0001) whereas it increased (dP/dt)max by 60% (P less than 0.0001). Sympathetic stimulation at 12 Hz decreased tau by 74% (P less than 0.0001). Our studies suggest that cardiac autonomic nerve stimulation affects left ventricular relaxation more than left ventricular contraction.

Vagal stimulation decreases rate of left ventricular relaxation

We determined the effects of vagal stimulation on the time constant (tau) of left ventricular isovolumic pressure decay and on the maximum rates of left ventricular pressure change (dP/dt) during contraction and relaxation in anesthetized dogs. In each dog, the atria were paced at a constant rate of 150 beats/min. We recorded left ventricular pressure waveforms in the absence (control) and in the presence of vagal stimulation at frequencies of 1, 2, and 3 Hz. During the control periods and during vagal stimulation at each frequency, we determined tau, the maximal rate of contraction, and the maximal rate of relaxation from left ventricular pressure waveforms recorded at medium (100 mmHg), high (130 mmHg), and low (73 mmHg) afterloads. Vagal stimulation at a frequency of 3 Hz increased tau by 23%. This effect of vagal stimulation on tau was most pronounced at the high afterload. Vagal stimulation at 3 Hz decreased the maximal rate of relaxation by 19%, but it decreased the maximal rate of contraction by only 8%. Thus vagal stimulation significantly decreased the rate of left ventricular relaxation and had a greater depressant effect on ventricular relaxation than on contraction.

Heart rate and coronary flow effects on the cardiac response to sympathetic stimulation

We studied the effects of changes in heart rate and coronary blood flow on the decay of the cardiac inotropic response to sympathetic stimulation in 10 anesthetized dogs. After we induced complete heart block, we paced the ventricles at rates of 90, 120 and 150.min-1. At each pacing frequency, we perfused the left main coronary artery with blood at a baseline flow and at a flow 85% above the baseline rate. At each combination of pacing frequency and flow, we stimulated the left ansa subclavia supramaximally at a frequency of 5 Hz for 2 min. To assess the rate of norepinephrine removal from the ventricular myocardium, we measured the 50% decay time of the left ventricular inotropic response [(dP/dt)max] immediately after cessation of sympathetic stimulation. We found that the inotropic response decayed faster (P = 0.03) when the coronary artery blood flow was high than when the flow was baseline. The effect of heart rate on the decay of the left ventricular inotropic response depended on the level of the coronary blood flow. When the blood flow was baseline, the inotropic response decayed more rapidly (P = 0.001) when the heart rate was 150.min-1 than when it was 90 or 120.min-1. However, when the flow was high, heart rate did not affect the response decay significantly. We conclude that the mechanical contraction of the ventricles facilitates the washout of norepinephrine from the cardiac interstitium and into the coronary circulation by virtue of a massaging action.

Increased heart rate accelerates norepinephrine washout from normal myocardium

We determined whether a change in heart rate affected the decay of the ventricular inotropic response to sympathetic stimulation in an experimental group and in a control group of anesthetized dogs. We induced complete heart block in each animal and paced the ventricles at rates of 90, 120, and 150 min-1 during two observation periods. In the experimental group, desipramine hydrochloride was given during the second period to block the neuronal uptake mechanism. The control animals did not receive desipramine during either period. The time required for the ventricular inotropic response to decay by 50% after cessation of a 2-min train of sympathetic stimulation was used as an index of the rate of norepinephrine washout from the myocardial interstitium. As we increased the pacing rate over the range of 90-150 min-1 in the experimental group, the mean decay half times (+/- SE) decreased by 36 +/- 4% (P less than 0.001) before desipramine and by 26 +/- 6% (P less than 0.001) in the presence of desipramine. These decrements in the decay half times were not significantly different from each other. The mean decay half times decreased by 36 +/- 4% (P less than 0.001) in the control dogs; the effects did not change appreciably from the first to the second observation period. We conclude that an increase in pacing frequency facilitates the washout of norepinephrine from the ventricular myocardium; this facilitation is equally pronounced regardless of whether the neuronal uptake mechanism is intact or suppressed.

Rate of acetylcholine hydrolysis affects the phase dependency of cardiac responses to vagal stimulation

The influence of the rate of acetylcholine hydrolysis on the magnitude and phase dependency of the cardiac chronotropic response to vagal stimulation was studied in anaesthetised dogs. In one group of animals the chronotropic response to tonic vagal stimulation varied directly with the dose of physostigmine. In a second group of animals one brief stimulus burst was delivered to the right vagus nerve during each cardiac cycle, and the timing (phase) of the stimulus was varied within the cycle. Before physostigmine was given the phase of the stimulus had a substantial influence on the chronotropic response. When each stimulus burst contained 6 pulses the response was changed from its minimum to its maximum value (mean (SEM) change 0.338(0.081) s) when the phase was shifted by a mean value of 0.091(0.031) s. After physostigmine (0.3 mg X kg-1) was given the change in response produced by a phase shift was much less pronounced. A mean shift in phase of 0.593(0.052) s was required to change the chronotropic response from its minimum to its maximum value, and the mean difference between the minimum and maximum response was only 0.140(0.032) s. Hence the rate of acetylcholine hydrolysis in the cardiac tissues is an important determinant of the phase dependency of the chronotropic response to repetitive vagal stimulation-that is, the slower the rate of hydrolysis the less the change in the chronotropic response elicited by a given change in stimulus timing.

Clinical characteristics and resource utilization of ICU patients: implications for organization of intensive care

We reviewed the clinical characteristics and resource utilization of 391 medical (M) and 315 surgical (S) ICU patients. In general, MICU patients had more physiologic derangement, as determined by the admission, maximal, and average acute physiology scores (APS). SICU patients had more frequent therapeutic interventions as measured by admission, maximal, and average therapeutic intervention scoring system values. Notably, 40% of MICU and 30% of SICU patients never received any active interventions and were admitted strictly for monitoring purposes. Patients on admission with APS less than or equal to 10 had markedly shorter ICU stays, with almost 50% less treatment than patients with APS over 10. Fifty-six percent of patients with APS less than or equal to 10 did not require any active intervention. In contrast, 83% of patients with APS greater than 10 had considerable intensive interventions. These patients required mechanical ventilation, invasive monitoring, and vasoactive drugs more than twice as often as patients with lower APS scores. Consideration should be given, therefore, to the organization of ICUs according to the patient's severity of illness.

Cardiopulmonary effects of oleic acid-induced pulmonary edema and mechanical ventilation

In order to define the mechanisms whereby cardiac output and arterial oxygen transport are reduced by acute permeability pulmonary edema and by positive end-expiratory pressure (PEEP), hemodynamic, respiratory, and lung water changes were measured in 12 mechanically ventilated dogs prior to the injection of oleic acid and at 1, 2.5, and 4 hr after the injection. Measurements were performed at each interval before and after the addition of 20 cm H2O PEEP. Positive end-expiratory pressure was not continued between measurements. One hour after the oleic acid injection, the lung water content and the pulmonary vascular resistance had increased more than 100% while the right ventricular (RV) volume, RV stroke volume, and PaO2 had decreased more than 35%. Each application of PEEP increased the PaO2 to control levels. However, PEEP also significantly increased the lung water content and pulmonary vascular resistance, and decreased the RV volume and stroke volume by 33%. The extravasation of fluid from the intravascular to the interstitial and alveolar spaces of the lung with oleic acid pulmonary edema is associated with substantial decreases in right ventricular volume and stroke volume and significant increases in the pulmonary vascular resistance. Treatment with 20 cm H2O PEEP further increases the lung water content and pulmonary vascular resistance and substantially reduces the right ventricular volume and stroke volume.

Effects of positive end-expiratory pressure on the right ventricle

Transmural cardiac pressures, stroke volume, right ventricular volume, and lung water content were measured in normal dogs and in dogs with oleic acid-induced pulmonary edema (PE) maintained on positive-pressure ventilation. Measurements were performed prior to and following application of 20 cmH2O positive end-expiratory pressure (PEEP). Colloid fluid was given during PEEP for ventricular volume expansion before and after the oleic acid administration. PEEP significantly increased pleural pressure and pulmonary vascular resistance but decreased right ventricular volume, stroke volume, and mean arterial pressure in both normal and PE dogs. Although the fluid infusion during PEEP raised right ventricular diastolic volumes to the pre-PEEP level, the stroke volumes did not significantly increase in either normal dogs or the PE dogs. The fluid infusion, however, significantly increased the lung water content in the PE dogs. Following discontinuation of PEEP, mean arterial pressure, cardiac output, and stroke volume significantly increased, and heart rate did not change. The failure of the stroke volume to increase despite significant right ventricular volume augmentation during PEEP indicates that positive-pressure ventilation with 20 cmH2O PEEP decreases right ventricular function.

Adenocarcinoma of the lung presenting with pericardial tamponade: report of a case and review of the literature

In a patient with cancer, a diagnosis of cardiac tamponade should be considered when there is dyspnea, cough, thready pulse or pulsus paradoxus, low systolic blood pressure, engorged neck veins, an enlarged cardiac silhouette, and total or ventricular electrical alternans. Immediate pericardiocentesis is indicated in such patients to avoid the risk of sudden death. A pericardial window should be created for more prolonged palliation of cardiac tamponade. Cytologic examination of the pericardial fluid often reveals malignant or highly suspect cells. Metastatic carcinomas from the lung and breast are the most common tumors that involve the heart when they spread in a retrograde fashion through the cardiac lymphatic system. Total pericardiectomy for the treatment of cardiac tamponade that is due to cancer is not generally advisable. Radiation therapy in the cardiac area with or without systemic chemotherapy is effective in decreasing the amount and the recurrence of neoplastic pericardial effusion.

Acute ethylene glycol poisoning

Ethylene glycol, a major constituent of antifreeze, is metabolized by alcohol dehydrogenase to glycoaldehyde, glycolate, glyoxylate, and oxalate. The metabolites of ethylene glycol cause severe metabolic acidosis and central nervous system, pulmonary, and renal damage. Ethanol competes with ethylene glycol as an alternate substrate of alcohol dehydrogenase. Two cases of ethylene glycol poisoning associated with serum concentrations of 59 and 150 mg/dl are reported. One patient was protected from the toxic effects of the metabolites because of concomitant ethanol ingestion. In patients with unexplained anion and osmol gaps, early diagnosis and therapy with ethanol and hemodialysis help prevent the toxic manifestations of ethylene glycol poisoning.

A computer-assisted monitoring system for arrhythmia detection in a medical intensive care unit

The arrhythmia detection capability of a computer-assisted monitoring system (CAMS) was studied in a large multidisciplinary ICU during an 18-month period. Four patient categories were evaluated: critically ill patients on mechanical volume respirators (group 1), patients with uncomplicated acute myocardial infarction (group 2), pacemaker-dependent patients (group 3), and patients on telemetry monitoring (group 4). ECG abnormalities were interpreted by the computer algorithm and recorded on paper. The same ECG abnormalities were analyzed independently by at least two critical care physicians unaware of the computer interpretations. The incidence of false-positive diagnoses (computer system errors) ranged from 10 in 1000 beats in groups 1, 2, and 4, to 20 in 1000 beats in group 3. Movement artifact accounted for 55.3% of all false-positive diagnoses. Of the total number of beats interpreted by the computer, 0.8% were false negatives and 3.8% were true positives. The most frequent true positive was pacemaker malfunction, which was diagnosed with 94% accuracy by the arrhythmia detection system. Significantly, rhythm abnormalities occurred as frequently in patients ventilated with mechanical respirators as in patients with acute myocardial infarction.

Blood volume following diuresis induced by furosemide

Changes in blood volume were investigated following intravenous injection of a single dose of furosemide in 21 patients with pulmonary edema. In a subset of 10 patients in whom the blood urea nitrogen level was 11.4 +/- 2.2 mg/dl and the serum creatinine level was 1.3 +/- 0.1 mg/dl and in whom total urine output exceeded 1 liter over a four- to six-hour interval ("diuretic" group), no significant change in plasma or total blood volume was observed, nor were there any significant changes in hematocrit. In a "nondiuretic" group of 11 patients who had moderately decreased renal function (blood urea nitrogen level 59.3 +/- 13.0 mg/dl and serum creatinine level 2.3 +/- 0.3 mg/dl) and in whom total urine output was less than 1 liter over the four- to six-hour interval, there was a significant increase in blood volume with a concomitant decrease in hematocrit and hemoglobin levels. Furosemide-induced diuresis therefore did not deplete intravascular volume. To the contrary, actions of furosemide that were independent of its diuretic action were associated with an expansion of plasma volume in the absence of diuresis. This may be related to the venous capacitance effects of furosemide with lowering of venous resistance and, therefore, lowering of the capillary hydrostatic pressure. In addition, there was an increase in colloid osmotic pressure. Both mechanisms increase the effective oncotic pressure gradient, which favors reabsorption of extravascular (edema) fluid. It is concluded that intravascular volume was therefore replenished at a rate equal to or in excess of the volume removed by diuresis.

Hemodynamic effects of pentobarbital therapy for intracranial hypertension

Barbiturate therapy has been employed for reduction of increased intracranial pressure (ICP) after acute brain injury and also for cerebral resuscitation. However, this treatment may be complicated by hypotension with an adverse impact on survival. We, therefore, investigated the acute hemodynamic effects of pentobarbital (PB) when administered in loading doses of 4-7 mg/kg and maintenance doses of 1-4 mg/kg. After pentobarbital therapy, HR, mean arterial pressure (MAP), and rectal temperature were significantly reduced. Four episodes of hypotension and 6 episodes of oliguria were observed during the initial 12 h of therapy in close relationship to reduced cardiac output, stroke volume, and MAP. These abnormalities were corrected by infusion of colloid-containing fluids. We postulate that increases in venous capacitance, hypovolemia, and decreased barostatic reflexes, rather than depression of myocardial function, accounted for the hemodynamic abnormalities.

Use of methylprednisolone in patients following acute myocardial infarction. Hemodynamic and metabolic effects

Hemodynamic and metabolic effects of methylprednisolone were investigated in a double-blind study of 28 patients with acute myocardial infarction (AMI), confirmed by unequivocal electrocardiographic and enzyme changes. Measurements were performed prior to and at 1.5, 3, 4, 4.5, 12 and 24 hours following infusion of methylprednisolone (13 patients) or placebo (15 patients). Although systemic vascular resistance decreased from 1,750 to 1,420 dynes . sec . cm-5 (p less than .001) and cardiac index increased from 2.77 to 3.10 L/min/m2 (p less than .02) between 0 and 4.5 hours, an abnormal increase in blood lactate was observed in 10 of the 13 patients following administration of methylprednisolone (3.0 vs 1.2 mM/L, p less than .001). Lactate elevation appeared one hour after infusion of methylprednisolone, was maximal at 12 hours, and persisted for more than 24 hours. There was no significant change in blood lactate in placebo treated patients. A transient but significant decrease in plasma volume was also observed following infusions of methylprednisolone. The elevation of blood lactate could not be explained by the reduction in plasma volume since the most striking increases in lactate were observed 12 hours following the initial infusion of methylprednisolone when the plasma volume was returning to the control value. No significant differences in other hemodynamic or metabolic parameters, infarct size or patient survival were observed between the two groups. We conclude that the hemodynamic benefits of glucocorticoids characterized by increased cardiac output and lowered systemic vascular resistance are counterbalanced by the potentially unfavorable conditions of lactate elevation and volume depletion.

Effects of methylprednisolone on P50, 2,3 diphosphoglycerate and arteriovenous oxygen difference in acute myocardial infarction

In a double-blind randomized study, 30 mg/kg of methylprednisolone sodium succinate (MPN) or 15 mg/kg of mannitol placebo (PL) were infused in 28 patients after acute myocardial infarction. Measurements were obtained immediately before and after for 24 hours after the initial infusion. The partial pressure of oxygen at 50% saturation of hemoglobin (P50) did not change significantly in vitro or in vivo after MPN, whereas 2,3 diphosphoglycerate (2,3 DPG) increased from 13.2 to 14.2 mumol/g Hb (p < 0.05) in the group receiving PL. The arteriovenous oxygen difference (Ca-VO2) remained constant after MPN or PL. The cardiac index (CI) increased after MPN (p < 0.02) associated with an increase in the oxygen consumption index (CI X A-V O2) from 146 to 170 ml/min/m2 (p < 0.05). These data show that MPN increases CI after acute myocardial infarction, but has no specific effects on P50, 2,3 DPG or Ca-VO2.

Measurement of toe temperature for assessing the severity of acute circulatory failure

The temperature gradient between the ventral surface of the first toe and the ambient temperature was measured and compared with established hemodynamic measurements in 71 critically ill patients. Thirty-two patients had acute myocardial infarctions, 21 patients had primary bacteremia and 18 patients had primary hypovolemia which followed acute blood loss. The temperature gradient served as a more predictable indicator of survival or fatality than either arterial pressure or cardiac index in each group of patients. Patients who improved after treatment and survived had increases in the toe minus ambient temperature gradient to more than 4 degrees C., whereas a gradient of less than 3 degrees over an interval of 12 hours was typically observed in patients who subsequently died. These observations indicate that the toe minus ambient temperature gradient provides a valuable, inexpensive and noninvasive monitor of tissue perfusion in critically ill patients.

Effect of afterload reduction on plasma volume during acute heart failure

Previous investigations in our unit indicated that acute cardiogenic pulmonary edema is associated not only with an increase in left ventricular end-diastolic pressure and pulmonary arterial wedge pressure but also with a relative increase in colloid osmotic (oncotic) pressure and peripheral hemoglobin concentration. This combination of changes suggested that acute congestive heart failure with pulmonary edema, unlike chronic congestive heart failure, is associated with a contraction of intravascular blood volume. In this study, plasma volume changes were measured before and during the treatment of acute cardiogenic pulmonary edema in 14 patients with arteriosclerotic heart disease. The plasma volume measurement in all 14 patients before the initiation of treatment was either normal or decreased. After treatment with the alpha adrenergic blocking agent phentolamine, the plasma volume increased rather than decreased when measured 4 and 12 hours after the initiation of treatment. During this time colloid osmotic pressure and peripheral hemoglobin concentration progressively decreased. These findings suggest that acute cardiogenic pulmonary edema is associated with the extravasation of large quantities of plasma water from the intravascular compartment into the interstitial compartment and contraction of the intravascular plasma volume. The treatment of acute cardiogenic pulmonary edema is associated with the return of hypo-oncotic fluid from the interstitial compartment back into the intravascular compartment with expansion of plasma volume and reduction of colloid osmotic pressure and hemoglobin concentration.

Relationship between colloid osmotic pressure and pulmonary artery wedge pressure in patients with acute cardiorespiratory failure

Close relationships between progressive respiratory failure, roentgenographic signs of pulmonary opacification and decreases in the difference between colloid osmotic pressure of plasma and the pulmonary artery wedge pressure (colloid-hydrosatic pressure gradient) were demonstrated in 49 critically ill patients with multisystem failure, in patients in shock. The potential importance of this relationship is underscored by the observation that fatal progression of pulmonary edema was related to a critical reduction in the colloid-hydrostatic pressure gradient to levels of less than 0 mm Hg. More often, reduction in colloid osmotic pressure rather than increases in left ventricular filling pressure (pulmonary artery wedge pressure) accounted for the decline in colloid-hydrostatic pressure gradient. Routine measurement of colloid osmotic pressure, preferably in conjunction with pulmonary artery wedge pressure, is likely to improve understanding of the mechanisms of acute pulmonary edema.

The measurement of the work of breathing for the clinical assessment of ventilator dependence

The work of breathing was measured in 10 normal subjects and in 28 critically ill patients with acute complications of obstructive pulmonary disease treated with assisted ventilation. The measurement of the work of breathing was found to be a useful objective variable for determining the capability for independent ventilation. Dependence on mechanical ventilation was observed when the respiratory work was greater than or equal to 1.7 kg-m/min. Patients were ordinarily capable of spontaneous ventilation when the respiratory work was less than or equal to 1.0 kg-m/min. Discontinuation of assisted ventilation was likely to be successful in those patients whose respiratory work was less than or equal to 1.5 kg-m/min if the patient was able to increase and maintain his work capability by a factor of two when breathing against an inspiratory resistance of 5 cm H2O for 10 min. Failure to increase the respiratory work when breathing against an inspiratory resistance indicated limitations in respiratory mechanics and was associated with the need for prolonged assisted ventilation. The measurement of the work of breathing against an inspiratory resistance of 5 cm H2O was useful in the identification and quantification of ventilatory reserve in patients with obstructive pulmonary disease.

Afterload reduction with phentolamine in patients with acute pulmonary edema

Phentolamine in amounts of 10 to 40 microgram/kg/min was infused intravenously for the emergency treatment of acute pulmonary edema due to left ventricular failure. Fourteen patients with arteriosclerotic heart disease, ranging in age from 52 to 87 years, had clinical and roentgenographic signs of pulmonary edema. The pulmonary artery wedge pressure was increased to an average of 24 mm Hg and the cardiac index was decreased to 1.9 liters/min/m2 or less prior to the administration of phentolamine. A reduction in the pulmonary artery wedge pressure to 14 mm Hg and an increase in the cardiac index to 2.5 liters/min/m2 was observed in response to this alpha adrenergic blocking agent. Reduction in peripheral resistance with phentolamine was associated with reversal of pulmonary edema.

First annual Herbert S. Shubin Memorial Lecture. Acute circulatory failure (shock) associated with cardiogenic pulmonary edema

Our findings confirm that acute pulmonary edema, when caused by left ventricular failure, represents a form of acute perfusion failure (shock) with metabolic acidemia, lactacidemia, and a reduction in forward blood flow. It is associated with a marked increase in peripheral resistance and an increase in venous capacitance. Most importantly, acute pulmonary edema is associated with a reduction in the intravascular blood volume. Acute pulmonary edema is not fundamentally different from other types of shock in which the shock state is initiated by one primary defect, and during the course of its progression, other primary mechanisms are called into action. In the instance of acute cardiogenic edema, the primary defect is cardiac pump failure and the secondary defects include hypovolemia and distributive defects associated with arterial vasoconstriction and expanded venous capacitance. Furosemide reverses acute pulmonary edema by increasing rather than decreasing intravascular blood volume with consequent improvement in the distributive and hypovolemic defects. Under extreme conditions, the volume defect in acute pulmonary edema may be so great that the patient presents with primary hypovolemia. The utilization of volume repletion is warranted under these circumstances.