Responses of older men with and without chronic obstructive pulmonary disease to prolonged ozone exposure

Measurement of cardiac output by Doppler echocardiography were compared to simultaneous measurements by thermodilution in 9 conscious horses. In the Doppler technique, mean blood flow velocities for estimation of cardiac output were recorded from the aorta and pulmonary artery. The flow area of each vessel was calculated from the vessel diameter, measured from a 2-dimensional ultrasound image. Differences in the site and method of measuring the vessel diameter altered the estimation of cardiac output by the Doppler method. Cardiac output was modified by the i.v. infusion of 4 micrograms/kg bwt/min dopamine and 4 micrograms/kg bwt/min dobutamine and by the i.v. administration of 10 micrograms/kg bwt detomidine and 20 micrograms/kg bwt butorphanol. Doppler measurements of cardiac output correlated closely with measurement by thermodilution. Measurements from the aortic outflow correlated more closely with thermodilution, than those from the pulmonary artery (r = 0.89 and r = 0.77, respectively). Doppler measurements when the mean flow velocity was recorded from the aorta and the flow area was measured from the ascending aorta using the leading edge method. There was no significant bias between the 2 techniques when Doppler flow velocities were recorded by this method and the limits of agreement were narrow (+/- 12.26 l/min). The differences between the 2 methods increased with increasing cardiac output. Doppler echocardiography is a safe noninvasive method of measuring cardiac output in horses. The agreement between Doppler echocardiography and thermodilution in this study is similar to that reported in man and is similar to that reported between thermodilution and other techniques in man.     

Measurement of cardiac output with continuous thermodilution. b1 Clinical experience with the Intellicath-Vigilans system

BACKGROUND: Thermodilution cardiac output measurements are commonly obtained by a manual bolus technique with a pulmonary artery catheter. METHODS: A new thermodilution catheter has been developed which utilizes an integral thermal filament and provides semicontinuous online cardiac output. The response of this new device in 25 patients undergoing coronary artery bypass grafting was examined. A total of 250 data pairs was obtained; the cardiac outputs ranged from 2.2 to 11.9 lts.min. RESULTS: The linear regression is represented by the following equation: continuous thermodilution = 0.7196 bolus thermodilution +1.038. The correlation coefficient was 0.75; the mean bias was 0.493 +/- 1.034. CONCLUSIONS: The new technique provides acceptable accuracy in many clinical situations except when sudden haemodynamic changes occur.     

Noninvasive assessment of cardiac output in critically ill patients by analysis of the finger blood pressure waveform

OBJECTIVE: To assess whether the measurement of cardiac output by computer-assisted analysis of the finger blood pressure waveform can substitute for the thermodilution method in critically ill patients. DESIGN: Prospective data collection. SETTING: Emergency department in a 2000-bed inner city hospital PATIENTS: Forty-six critically ill patients requiring invasive monitoring for clinical management were prospectively studied. INTERVENTIONS: Under local anesthesia a 7-Fr pulmonary artery catheter was inserted via the central subclavian or jugular vein. Cardiac output was determined by the use of a cardiac output computer and injections of 10 mL ice-cold glucose 5%. Noninvasive cardiac output was calculated from the finger blood pressure waveform by the use of the test software program. MEASUREMENTS AND MAIN RESULTS: Three hundred twenty-three pairs of invasive and noninvasive hemodynamic measurements were collected in intervals of 30 mins from 46 patients (mean age 61.9 +/- 12.4 yrs; 35 male, 11 female). The average cardiac index during the study period was 2.83 L/min/m2 (range 0.97 to 5.56). The overall discrepancy between both measurements was 0.14 L/min/m2 (95% confidence interval: 0.10-.018, p < .001). Seventy-five (23.2%) measurements had an absolute discrepancy > +/- 0.50 L/min/m2. Noninvasive and invasive comparisons of mean differential cardiac output were out of phase for 9.7% of all readings. CONCLUSION: Computer-assisted analysis of finger blood pressure waveform to assess cardiac output is not a substitute for the thermodilution method due to a high percentage (23.2%) of inaccurate readings; however, it may be a useful tool for the detection of relative hemodynamic trends in critically ill patients.     

Effects of long term oxygen therapy in patients with idiopathic pulmonary fibrosis. I. Effect on the course of the primary disease and on pulmonary circulation

The study was performed in 18 patients (15 F and 3-M) aged 35-57 yers (mean 46 +/- 7) diagnosed as idiopathic lung fibrosis. Ten patients (group A) recived standard treatment (prednisone 10-15 mg/day) and supplementary home oxygen therapy (mean 16.4 h/day) for a period of 4 years. During exacerbations antibiotics, theophylline and expectorants were prescribed. Eight patients (group B) receiving the same treatment without home oxygen, served as controls. At study entry lung function test (TLC, VL, Dlco), blood gases, hematocrit, hemodynamic parameters of the pulmonary circulation and thermodilution cardiac output were measured in all patients. The measurements were repeated after 4 years of follow-up. At follow-up examination no differences in pulmonary function parameters were shown between the groups. Mean pulmonary artery pressure and pulmonary vascular resistance were significantly lower in patients receiving home oxygen therapy (group A) as compared with those treated pharmacologically only (group B). Best effects of oxygen therapy were observed in patient with lower pulmonary artery pressures at study entry.     

Hemodynamic effects of the implantation of an intracaval oxygenator

Treatment of severe respiratory failure by extracorporeal membrane oxygenation (ECMO) is complex. However, there is now an intravascular gas exchanger (IVOX) available that provides extrapulmonary gas transfer without requiring an extracorporeal blood path. The present study was performed to determine the hemodynamic effects resulting from the intracaval placement of the intravascular device. A bovine model (n = 6; body-weight = 72 +/- 5 kg) was selected for temporary lung support with the intravascular device. The latter was placed in the caval axis under fluoroscopic control after full instrumentation of the animal for hemodynamic measurements including a pulmonary artery catheter for determination of cardiac output by thermodilution and continuous readout of mixed venous oxygen saturation. All measurements were taken after a stabilization period of 15 min. The heart rate moved from 65 +/- 8 before to 72 +/- 10 after implantation and 68 +/- 9 after onset of intravascular gas exchange (NS). Right atrial pressure was 13 +/- 3 mm Hg before, 12 +/- 3 mm Hg after implantation and 10 +/- 3 mm Hg after onset (NS) whereas femoral venous pressure moved from 14 +/- 3 mm Hg to 17 +/- 4 mm Hg (p < 0.05) and remained at 17 +/- 4 mm Hg after onset. Cardiac output was 5.3 +/- 0.7 l/min before, 5.4 +/- 0.7 l/min after implantation and 5.3 +/- 1.1 l/min after onset (NS) while mixed venous oxygen saturation dropped from 60 +/- 7% to 54 +/- 11% and moved to 57 +/- 11 after onset of the device (NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical, biological, and immunophenotypical characteristics of B-cell chronic lymphocytic leukemia with trisomy 12 by fluorescence in situ hybridization

Intra-aortic balloon pumping is frequently used in patients with cardiogenic shock when oliguria persists despite maximal pharmacologic support. The objective of this study was to measure the effect of intra-aortic balloon pumping on renal blood flow, renal oxygen delivery, and renal oxygen consumption in such patients. Central hemodynamics, renal blood flow, and oxygen transport were measured in 10 patients in low cardiac output states. Measurements were made with and without intra-aortic balloon counterpulsation. Renal blood flow was measured by continuous renal vein thermodilution. Small improvements were observed in cardiac output (3.1 +/- 0.8 vs 3.5 +/- 0.8 L/min, P < .01) and pulmonary capillary wedge pressure (22 +/- 5.6 vs 19 +/- 5.3 mmHg, P < .05), but mean arterial blood pressure was unchanged (69 +/- 11 vs 69 +/- 5 mmHg, not significant). Baseline renal blood flow was reduced to approximately 37%, renal oxygen delivery to 31%, and renal oxygen consumption to 60% of normal values. No significant improvement was seen in single-kidney renal blood flow (184 +/- 108 vs 193 +/- 107 mL/min), renal oxygen delivery (28 +/- 16 vs 30 +/- 16 mL/min), or renal oxygen consumption (4.9 +/- 2.0 vs 4.7 +/- 2.5 mL/min) in response to 1:1 counterpulsation. In comparison with measurements made during short-term suspension of counterpulsation, 1:1 aortic balloon pumping failed to result in an increase in renal blood flow, oxygen delivery, or oxygen consumption from the low levels observed in these patients.     

Application of color Doppler flow mapping to calculate orifice area of St Jude mitral valve

BACKGROUND: The effective orifice area (EOA) of a prosthetic valve is superior to transvalvular gradients as a measure of valve function, but measurement of mitral prosthesis EOA has not been reliable. METHODS AND RESULTS: In vitro flow across St Jude valves was calculated by hemispheric proximal isovelocity surface area (PISA) and segment-of-spheroid (SOS) methods. For steady and pulsatile conditions, PISA and SOS flows correlated with true flow, but SOS and not PISA underestimated flow. These principles were then used intraoperatively to calculate cardiac output and EOA of newly implanted St Jude mitral valves in 36 patients. Cardiac output by PISA agreed closely with thermodilution (r=0.91, Delta=-0.05+/-0.55 L/min), but SOS underestimated it (r=0.82, Delta=-1.33+/-0.73 L/min). Doppler EOAs correlated with Gorlin equation estimates (r=0.75 for PISA and r=0.68 for SOS, P<0.001) but were smaller than corresponding in vitro EOA estimates. CONCLUSIONS: Proximal flow convergence methods can calculate forward flow and estimate EOA of St Jude mitral valves, which may improve noninvasive assessment of prosthetic mitral valve obstruction.     

Lack of restriction of growth for aquareovirus in mammalian cells

OBJECTIVES: We examined the effects of chronic type A endothelin receptor (ETA) blockade in a dog model of pacing-induced cardiomyopathy. METHODS: Eight dogs received an ETA antagonist, LU 135252 (50 mg/kg orally daily) and nine dogs received a matching placebo starting at day three of pacing and continued for the remainder of the three weeks of pacing. RESULTS: In the placebo group, the mean pulmonary artery pressure and left ventricular end diastolic pressure increased from 16 +/- 3 and 8 +/- 2 mmHg, respectively, at baseline to 40 +/- 11 and 34 +/- 7 mmHg, respectively, at two weeks (both p < 0.001 versus baseline). Cardiac output declined from 3.5 +/- 0.7 to 1.9 +/- 0.6 l/min (p < 0.001). In the treatment group, LU 135252 attenuated the increase in mean pulmonary artery and left ventricular end diastolic pressure (16 +/- 3 and 9 +/- 1 mmHg at baseline to 29 +/- 3 and 27 +/- 3 mmHg, respectively, at two weeks (p < 0.001), and the decline in cardiac output (3.2 +/- 0.3 to 2.6 +/- 0.8 l/min, p < 0.01; p < 0.05 versus placebo for the three parameters). Systemic and pulmonary vascular resistance increased only in the placebo group. Left ventricular end-diastolic volume increased to a similar degree. However, LU 135252 attenuated the increase in plasma norepinephrine level (placebo, 1.2 +/- 0.5 to 3.7 +/- 1.9 pmol/l; treatment, 0.8 +/- 0.3 to 2.4 +/- 0.6 pmol/l; both p < 0.001 versus baseline; p < 0.05 versus placebo). CONCLUSION: Our results suggest that endothelin-1 plays a role in the hemodynamic perturbations in canine pacing-induced cardiomyopathy. The favourable hemodynamic effects without concomitant aggravation of neurohormonal activation suggests that ETA receptor blockade may be beneficial in the treatment of heart failure.     

Neither dopamine nor dobutamine corrects mesenteric blood flow depression caused by positive end-expiratory pressure in a rat model of acute lung injury

OBJECTIVE: To determine if either dopamine or dobutamine would counteract the deleterious effect that positive end-expiratory pressure (PEEP) has on cardiac output and mesenteric blood flow in a rat model of acute lung injury. DESIGN: Prospective, randomized, controlled trial in a clinically relevant model of acute lung injury. SETTING: Microcirculation research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: The animals were anesthetized with pentobarbital (30 mg/kg) by intraperitoneal injection. They underwent tracheostomy, jugular and femoral vein cannulation, femoral artery cannulation, carotid artery thermistor placement, and bowel preparation for in vivo video microscopy. Acute lung injury was created by administering 0.1 N hydrochloric acid (1 mL/kg) via the tracheostomy. Dopamine or dobutamine (2.5 or 12.5 microg/kg/min), followed by two intravenous fluid boluses, was administered to rats ventilated with 5, 10, 15, and 20 cm H2O of PEEP. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure, thermodilution cardiac output, mesenteric arteriolar diameter, and red blood cell velocity were measured and mesenteric blood flow was calculated. Cardiac output was depressed in rats exposed to 20 cm H2O of PEEP by 32+/-2%. The corresponding values for cardiac output depression at 20 cm H2O of PEEP in rats receiving 2.5 and 12.5 microg/kg/min of dopamine and 2.5 and 12.5 microg/kg/min of dobutamine were 31+/-1%, 21+/-1%, 29+/-0%, and 24+/-2%, respectively. Mesenteric blood flow was depressed in rats ventilated with 20 cm H2O of PEEP by 74+/-3%, while the corresponding values in rats exposed to 20 cm H2O of PEEP and receiving 2.5 or 12.5 microg/kg/min of dopamine or 2.5 or 12.5 microg/kg/min of dobutamine were 86+/-3%, 77+/-3%, 73+/-3%, and 66+/-3%, respectively. Fluid boluses did not correct the deficits in cardiac output or mesenteric blood flow caused by the combination of acute lung injury and PEEP. CONCLUSIONS: The higher doses of dopamine and dobutamine partially, but insignificantly, corrected the cardiac output depression caused by PEEP in a model of acute lung injury. Neither dose of dopamine nor dobutamine was able to improve PEEP-induced mesenteric blood flow depression.     

Hemodynamics in sepsis: its relationship to pulmonary complication

Serial clinical observations and hemodynamic measurements were made on seventeen patients with sepsis and ten control cases. Control patients were slightly hypovolemic immediately after operation. In the eleven high flow patients, that is, those with the initial cardiac index higher than 3.0 liters/min/m(2), we observed characteristic hemodynamics with lowered vascular resistance, higher cardiac output and hypotension. The anomalous vascular resistance began to return to normal approximately 48 hr after operation. In three cases pulmonary complication developed at this time and therefore pulmonary artery pressure and/or pulmonary wedge pressure exceeded the normal range. In these cases treatment was aimed at lowering the pulmonary pressure. Pulmonary complication was improved when these pressures returned within normal range. In the seven low flow patients, that is, those with cardiac index lower than 2.9 liters/min/m(2), we observed decreased cardiac index with increased systemic and pulmonary vascular resistance. In these cases pulmonary complication appeared to develop by increased permeability of the pulmonary capillary wall. Elevated pulmonary artery pressure might accelerate the progress of the complication. Monitoring and controlling pulmonary artery pressure and pulmonary wedge pressure were effective in prevention and treatment of pulmonary complication in this group.     

Evaluation of a pulsatile pediatric ventricular assist device in an acute right heart failure model

BACKGROUND: The development of pulsatile ventricular assist devices for children has been limited mainly by size constraints. The purpose of this study was to evaluate the MEDOS trileaflet-valved, pulsatile, pediatric right ventricular assist device (stroke volume = 9 mL) in a neonatal lamb model of acute right ventricular failure. METHODS: Right ventricular failure was induced in ten 3-week-old lambs (8.6 kg) by right ventriculotomy and disruption of the tricuspid valve. Control group 1 (n = 5) had no mechanical support whereas experimental group 2 (n = 5) had right ventricular assist device support for 6 hours. The following hemodynamic parameters were measured in all animals: heart rate and right atrial, pulmonary arterial, left atrial, and systemic arterial pressures. Cardiac output was measured by an electromagnetic flow probe placed on the pulmonary artery. RESULTS: All results are expressed as mean +/- standard deviation and analyzed by Student's t test. A p value less than 0.05 was considered statistically significant. Base-line measurements were not significantly different between groups and included systemic arterial pressure, 80.6 +/- 12.7 mm Hg; right atrial pressure, 4.6 +/- 1.6 mm Hg; mean pulmonary arterial pressure, 15.6 +/- 4.2 mm Hg; left atrial pressure, 4.8 +/- 0.8 mm Hg; and cardiac output, 1.4 +/- 0.2 L/min. Right ventricular injury produced hemodynamics compatible with right ventricular failure in both groups: mean systemic arterial pressure, 38.8 +/- 10.4 mm Hg; right atrial pressure, 16.8 +/- 2.3 mm Hg; left atrial pressure, 1.4 +/- 0.5 mm Hg; and cardiac output, 0.6 +/- 0.1 L/min. All group 1 animals died at a mean of 71.4 +/- 9.4 minutes after the operation. All group 2 animals survived the duration of study. Hemodynamic parameters were recorded at 2, 4, and 6 hours on and off pump, and were significantly improved at all time points: mean systemic arterial pressure, 68.0 +/- 13.0 mm Hg; right atrial pressure, 8.2 +/- 2.3 mm Hg; left atrial pressure, 6.4 +/- 2.1 mm Hg; and cardiac output, 1.0 +/- 0.2 L/min. CONCLUSIONS: The results demonstrate the successful creation of a right ventricular failure model and its salvage by a miniaturized, pulsatile right ventricular assist device. The small size of this device makes its use possible even in small neonates.     

Determination of heart time volume using the Fick principle in the early postoperative phase after correction of congenital heart defects. Comparison of the calculation of arterio-mixed venous oxygen differences and pulmonary oxygen uptake with the calculation of arterial-central venous oxygen differences and pulmonary oxygen uptake

Comparison of the calculation by means of the arterio-mixed venous oxygen difference and the oxygen uptake with the calculation by means of the arterio-central venous oxygen difference and the oxygen uptake. OBJECTIVE: How reliable is the measurement of cardiac output on Fick's principle without a pulmonary artery catheter? SETTING: PICU in an University hospital. DESIGN: In the postoperative period following complete repair of congenital heart disease we carried out 91 simultaneous measurements of blood gases in 45 infants and children (mean age 18.6 months, mean body weight 8.9 kg) from a systemic artery, the A. pulmonalis, and the V. cava superior. We also determined the pulmonary oxygen uptake in 24 patients (48 measurements). Cardiac output was calculated on Fick's principle using the arterio-mixed venous oxygen difference and the pulmonary oxygen uptake (HZV a-pa) and compared to the cardiac output derived from the central venous values (HZV a-zv). We differentiated between patients with a left to right shunt of 10% or more postoperatively (group A, n = 18) and all others (group B, n = 27). RESULTS: In both groups the correlation coefficient between HZV a-zv and HZV a-pa was high (group A: r = 0.97, group B: r = 0.94). In group A HZV a-pa (mean: 1958 ml/min) was higher than HZV a-zv (mean: 1340 ml/min), group B showed the opposite situation (mean HZV a-pa: 1136 ml/min, mean HZV a-zv: 1373 ml/min). With the Wilcoxon signet-rank test we found significant differences between the partial pressure of oxygen and the saturation of central venous and mixed venous blood samples in both groups, but HZV a-zv and HZV a-pa were different significantly on a level of p < or = 0.01 only in group A. CONCLUSIONS: In both groups HZV a-pa and HZV a-zv correlated well. Therefore, if a pulmonary artery catheter is not inserted; the course of the cardiac output can be calculated with acceptable reliability from the central venous blood gases. By means of Fick's principle the pulmonary blood flow is determined, which is higher than the systemic blood flow in cases of left to right shunting, because of the recirculation in the pulmonary blood circuit. Interpreting the results this has to be taken into account.     

Massive verapamil overdose complicated by noncardiogenic pulmonary edema

We describe two cases of pulmonary edema, bradycardia, and hypotension associated with massive verapamil overdose. A noncardiogenic etiology of the pulmonary edema was indicated in one patient by normal thermodilution cardiac output and pulmonary artery occlusion pressure, and in the other patient by a normal echocardiogram. We hypothesize that calcium channel blocker overdose predisposes patients to develop pulmonary edema.     

Evaluation of a continuous cardiac output and mixed venous oxygen saturation catheter in critically ill surgical patients

OBJECTIVE: To evaluate the agreement of continuous cardiac output and mixed venous oxygen saturation measurements, obtained with a modified pulmonary artery catheter, with those values obtained by standard intermittent bolus thermodilution and cooximetry. DESIGN: Prospective, clinical investigation. SETTING: A surgical intensive care unit in a tertiary referral center. PATIENTS: Twenty-one adult critically ill surgical patients, requiring pulmonary artery catheter monitoring. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A modified pulmonary artery catheter capable of continuous monitoring of cardiac output and mixed venous oxygen saturation was used with either an 8.5-Fr or a 9-Fr introducer. At random intervals, the continuous cardiac output measurement was compared with the cardiac output obtained using standard intermittent bolus thermodilution. The system was calibrated every 24 hrs for mixed venous oxygen saturation monitoring. Each saturation obtained by the laboratory cooximeter was compared with that value recorded using the catheter. Data points for 202 pairs of cardiac output (21 patients, 31 catheters) and 65 pairs of mixed venous oxygen saturation (20 patients, 28 catheters) were obtained. The bias and precision of the cardiac output data were 0.49 and 1.01 L/min, respectively. The agreement between the continuous and bolus values decreased as the cardiac output increased. Heart rate did not affect the agreement between the continuous and bolus techniques. The bias and precision of the mixed venous oxygen saturation data were -0.57% and 3.76%, respectively. The hematocrit did not affect the bias or precision of the venous saturation data over the hematocrit range observed (23.2% to 44.6%). Fewer catheter malfunctions were observed when the catheter was used with a 9-Fr introducer than with an 8.5-Fr introducer. CONCLUSIONS: The test catheter adequately measures continuous cardiac output and mixed venous oxygen saturation in the clinical setting. Because intermittent bolus thermodilution is not a true "gold standard" for cardiac output determination, new techniques compared with bolus thermodilution may fail to achieve accuracy expectations. A 9-Fr introducer is recommended, as fiberoptic damage may have occurred when the 8.5-Fr introducer was used.     

Validity of cardiac output measurement by the thermodilution method in the presence of acute tricuspid regurgitation

Evaluation of patients with acute tricuspid insufficiency may include assessment of cardiac output by the thermodilution method. The accuracy of estimates of thermodilution-derived cardiac output in the presence of tricuspid insufficiency has been questioned. This study was designed to determine the validity of the thermodilution technique in a canine model of acute reversible tricuspid insufficiency. Cardiac output as measured by thermodilution and electromagnetic flowmeter was compared at two grades of regurgitation. The relationship between these two methods (thermodilution/electromagnetic) changed significantly from a regression slope of 1.01 +/- 0.18 (mean +/- standard deviation) during control conditions to a slope of 0.86 +/- 0.23 (p < 0.02) during severe regurgitation. No significant change was observed between control and mild regurgitation or between the initial control value and a control measurement repeated after tricuspid insufficiency was reversed at the termination of the study. This study shows that in a canine model of severe acute tricuspid regurgitation the thermodilution method underestimates cardiac output by an amount that is proportional to the level of cardiac output and to the grade of regurgitation.     

Lithium dilution cardiac output measurement: a comparison with thermodilution

OBJECTIVE: To compare the results of cardiac output measurements obtained by lithium dilution and thermodilution. DESIGN: Case series, observational study. SETTING: High-dependency postoperative unit and intensive care unit of a teaching hospital. PATIENTS: Forty patients were studied. Thirty-four patients had undergoing heart surgery requiring cardiopulmonary bypass within the previous 2 days; the diagnoses in the other patients were myocardial infarct (n = 2), septicemia (n = 2), adult respiratory distress syndrome, and pericardectomy. INTERVENTIONS: Cardiac output was measured five times in each patient, using lithium dilution (single measurement) and bolus thermodilution (series of three to six measurements according to standard clinical practice, taking the average of the closest three). In a subgroup of 14 patients, cardiac output was also measured using "continuous thermodilution." MEASUREMENTS AND MAIN RESULTS: Comparing lithium dilution with bolus thermodilution, the mean of the differences (lithium dilution-thermodilution) was -0.25 +/- 0.46 [SD] L/min. Linear regression analysis gave y = 0.31 + 0.89x (r2 = .94) for lithium dilution vs. thermodilution. CONCLUSIONS: The overall agreement between the two methods was good. The variability of the thermodilution measurements was greater than that of the lithium dilution measurements. The lithium dilution method is at least as accurate as bolus thermodilution and, since pulmonary artery catheterization is not needed, it has the advantages of being safe and quick to perform.     

Hemodynamic mechanism of vasovagal syncope

Vasovagal syncope is a common clinical problem, however the hemodynamic mechanism is not clearly understood. The aim of the present study was to investigate the circulatory control mechanism of vasovagal syncope provoked by the head-up tilt test. Thirty two patients with recurrent unexplained syncope were studied using a head-up (60 degrees) tilt test. The electrocardiogram, arterial blood pressure, pulmonary arterial pressure and central venous pressure were monitored continuously, and the cardiac output was measured by the thermodilution method. Twenty patients (62.5%) had positive tilt test responses, of which 12 developed typical vasovagal syncope with marked hypotension and bradycardia; the others developed hypotension without bradycardia. There were five women and seven men with a mean age (+/- SD) of 53.3 +/- 15 years. The effect of head-up tilt resembled that of hypovolemia. The central venous pressure, pulmonary capillary wedge pressure and cardiac output declined with an increase of heart rate and systemic vascular resistance. However the mean blood pressure was maintained. During vasovagal syncope, the heart rate and blood pressure fell precipitously and significantly, the cardiac index was reduced from 2.22 +/- 0.43 to 1.51 +/- 0.32 liters/min/m2 (p value < 0.05) and the systemic vascular resistance index decreased from 3,689 +/- 859 to 1,999 +/- 543.9 dynes s cm5/m2 (p value < 0.05). The results of our study showed that both reduction of cardiac output and withdrawal of sympathetic vasoconstriction tone contribute to the development of hypotension in vasovagal syncope.     

A comparison of hemodynamic parameters derived from transthoracic electrical bioimpedance with those parameters obtained by thermodilution and ventricular angiography

OBJECTIVE: To determine the limits of agreement between the cardiac output and volumetric data estimated by impedance cardiography with the cardiac output determined by thermodilution and the left ventricular ejection fraction and end-diastolic volume estimated from left ventriculography. DESIGN: A prospective study. SETTING: The cardiac catheterization laboratory of a university-affiliated teaching hospital. PATIENTS: Twenty-four patients with coronary artery disease undergoing elective left- and right heart catheterization. INTERVENTIONS: Cardiac output was measured by the thermodilution method and the ejection fraction and left ventricular volumetric data were determined by ventriculography. These same measurements were obtained by simultaneously performed impedance cardiography using a commercially available bioimpedance device. MEASUREMENTS AND MAIN RESULTS: The patients' mean cardiac output was 4.6 +/- 1.7 L/min by bioimpedance and 5.0 +/- 1.1 L/min by thermodilution. The limits of agreement between the two methods was -4.1 to 3.5 L/min. The 95% confidence intervals for the lower and upper limits of agreement were -2.7 to -5.5 L/min and 2.1 to 4.9 L/min, respectively. The mean ejection fraction was 63 +/- 8% by bioimpedance and 53 +/- 15% by ventriculography. The limits of agreement between the ejection fraction estimated by bioimpedance and ventriculography was -35% to 37%. The 95% confidence intervals for the lower and upper limits of agreement were -22% to -48% and 24% to 50%, respectively. The mean left ventricular end-diastolic volume was 108 +/- 47 mL, as estimated by bioimpedance, and 121 +/- 35 mL, as estimated by ventriculography. The limits of agreement between the left ventricular end-diastolic volume as estimated by bioimpedance and ventriculography was -139 to 113 mL. The 95% confidence intervals for the lower and upper limits of agreement were -184 to -94 mL and 68 to 158 mL, respectively. CONCLUSIONS: The 95% confidence range defining the limits of agreement between cardiac output and volumetric data estimated by bioimpedance, with the cardiac output measurement by thermodilution and the volumetric data estimated from left ventriculography, were wide, making the degree of agreement clinically unacceptable. In the opinion of the authors, impedance cardiography should not replace invasive hemodynamic monitoring at this time.     

Aerosolized prostacyclin and iloprost in severe pulmonary hypertension

OBJECTIVE: To compare the effects of aerosolization of prostacyclin and its stable analog iloprost with those of nasal oxygen, inhaled nitric oxide, and intravenous prostacyclin on hemodynamics and gas exchange in patients with severe pulmonary hypertension. DESIGN: Open uncontrolled trial. SETTING: Justus-Liebig-University, Giessen Germany. PATIENTS: 4 patients with primary pulmonary hypertension and 2 patients with severe pulmonary hypertension associated with calcinosis, the Raynaud phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia (the CREST syndrome). All were classified as New York Heart Association class III or class IV. INTERVENTION: Short-term applications of O2, inhaled nitric oxide, intravenous prostacyclin, aerosolized prostacyclin, and aerosolized iloprost during repeated catheter investigation of the right side of the heart within a 1-month period. One patient had long-term therapy with inhaled iloprost. RESULTS: Aerosolized prostacyclin decreased pulmonary artery pressure in 6 patients from (mean +/- SE) 62.3 +/- 4.1 mm Hg to 50.8 +/- 5.5 mm Hg and reduced pulmonary vascular resistance from 1721 +/- 253 dyne/s cm-5 to 1019 +/- 203 dyne/s cm-5, and it increased cardiac output from 2.75 +/- 0.21 L/min to 4.11 +/- 0.54 L/min, mixed venous oxygen saturation from 51.1% +/- 3/4% to 66.3% +/- 4.1% and arterial oxygen saturation from 90.6% +/- 2.7% to 93.8% +/- 23% (P<0.05 for all changes). Mean systemic arterial pressure was only slightly affected. The responses lasted for 10 to 30 minutes after inhalation was terminated. Aerosolized iloprost had an identical efficacy profile but was associated with a longer duration of the pulmonary vasodilatory effect (60 min to 120 min). In comparison, intravenous prostacyclin reduced pulmonary vascular resistance with corresponding efficacy but produced a more pronounced decline in systemic artery pressure and no clinically significant decrease in pulmonary artery pressure. Nitric oxide and O2 were less potent pulmonary vasodilators in these patients. In one patient, 1 year of therapy with aerosolized iloprost (100 microgram/d in six aerosol doses) resulted in sustained efficacy of the inhaled vasodilator regimen and clinical improvement. CONCLUSION: Aerosolization of prostacyclin or its stable analog iloprost causes selective pulmonary vasodilatation, increases cardiac output, and improves venous and arterial oxygenation in patients with severe pulmonary hypertension. Thus, it may offer a new strategy for treatment of this disease.     

Amrinone versus dopamine-nitroglycerin after reconstructive surgery for complete atrioventricular septal defect

OBJECTIVES: To compare the effectiveness and safety of amrinone and a combination of dopamine and nitroglycerin in infants after reconstructive surgery for congenital heart disease. DESIGN: A prospective, randomized, double-blind study. SETTING: Pediatric intensive care unit in a university hospital. PARTICIPANTS: Thirty-two infants with complete atrioventricular septal defect. INTERVENTIONS: Amrinone loading dose, 2 mg/kg, followed by a maintenance infusion, 7.5 micrograms/kg/min, was given to 17 infants before separation from cardiopulmonary bypass. The remaining 15 patients received a combination of dopamine, 5 micrograms/kg/min, and nitroglycerin, 1 microgram/kg/min. MEASUREMENTS AND MAIN RESULTS: The circulatory state of the patients was evaluated from 4 to 18 hours after cardiopulmonary bypass. The systemic blood flow index, calculated using the Fick principle, was higher in the amrinone group (2.5 +/- 0.7 L/min/m2) compared with the dopamine-nitroglycerin group (2.0 +/- 0.6 L/min/m2, mean +/- SD). The pulmonary blood flow index in the amrinone group was higher (2.9 +/- 0.6 L/min/m2) than in the dopamine-nitroglycerin group (2.2 +/- 0.6 L/min/m2); no significant difference was noted in the mean pulmonary artery pressure. The oxygen extraction ratio was higher in the dopamine-nitroglycerin group (0.41 +/- 0.07) compared with the amrinone group (0.34 +/- 0.08). Despite lower platelet counts in the amrinone group, no hemorrhagic complications were seen in any patient. CONCLUSIONS: With this dosage regimen, amrinone provides a higher cardiac output, more favorable oxygen dynamics, and lower pulmonary vascular resistance than dopamine and nitroglycerin.