Thermodilution Pulmonary Artery Catheter Research Articles

Effect of oxygen on pulmonary hemodynamics and incidence of atrial fibrillation after noncardiac thoracotomy

Objective: The mechanism of postthoracotomy atrial fibrillation (AF) could be related to right ventricular (RV) strain. The effect of oxygen on the occurrence of postoperative AF and on RV function was studied. Design: A prospective, randomized study. Setting: A university hospital. Participants: Twenty-four noncardiac thoracotomy patients. Interventions: At the end of the postoperative anesthesia care unit period, the patients were randomly allocated to receive 35% oxygen until either the third (P = prolonged group) or the first postoperative morning (S = short group). Measurements and Main Results: Measurement of hemodynamic variables using a thermodilution pulmonary artery catheter, oxygenation, concentration of plasma atrial natriuretic peptide (ANP) and Holter monitoring were started preoperatively and continued for the 3 postoperative days (PODs). Systolic RV pressure (systolic RVP) and pulmonary vascular resistance (PVR) increased postoperatively only in group S. Major changes in RV performance were not seen with echocardiography or the thermodilution method in any patient. Silent episodes of AF occurred in three patients (25%) in group P and in one patient (8%) in group S (not significant [NS]) without deviations in plasma ANP concentration. On each of the 3 PODs, all patients were exposed to 60% oxygen for 15 minutes. Systolic RVP decreased significantly during the exposure to 60% oxygen only in group S, but not in patients developing AF. Predictive factors for AF were a high preoperative PVR, intraoperative bleeding necessitating volume loading, and elevated systolic RVP immediately after thoracotomy. Conclusion: Short episodes of AF occurred irrespective of the length of oxygen therapy. Occurrence of AF could not be explained by changes in RV function.

Prostaglandin E1 antagonizes hypoxic pulmonary vasoconstriction but reduces systemic blood pressure in dogs

To investigate whether prostaglandin E1 (PGE1) directly inhibits hypoxic pulmonary vasoconstriction in dogs. Prospective, longitudinal study. University research laboratory. Six mongrel dogs in vivo. The left thorax of anesthetized and ventilated dogs was opened and the left lower lobe was separately ventilated. The tip of the thermodilution pulmonary artery catheter was introduced into the left lower lobe pulmonary artery. The left lower lobe was ventilated with hyperoxic (95% oxygen and 5% CO2) or hypoxic (95% nitrogen and 5% CO2) gas. By manipulating the occluders placed on both pulmonary arteries, blood flow in the left lower lobe was regulated. Continuous pressure-flow plots for the left lower lobe were then obtained. Measurements included continuous pressure-flow plot generation, thermodilution cardiac output and blood flow in the left lower lobe, and blood gas analysis. Alveolar hypoxia of the left lower lobe caused blood flow in the left lower lobe to decrease from 371.8 +/- 63.4 to 95.0 +/- 23.4 mL/min and shifted the pressure-flow plot to the right, with a decreased slope and with an increase in the pressure-axis intercept. Subsequently, systemic venous infusion of PGE1 at a rate of 0.3 microg/kg/min had no effect on the pressure-flow plot configuration, blood flow in the left lower lobe, pulmonary vascular resistance, systemic vascular resistance, and PaO2. However, there was a decrease in the pressure-axis intercept of the pressure-flow plot. Infusion of PGE1 at a rate of 3.0 microg/kg/min (high-dose) during hypoxia reduced pulmonary vascular resistance and systemic vascular resistance by 19% and 25%, respectively, and returned the pressure-flow plot toward normal while blood flow in the left lower lobe increased to 122.6 +/- 21.0 mL/min. Consequently, PaO2 decreased from 270 +/- 31 to 144 +/- 32 torr (36.0 +/- 4.1 to 19.2 +/- 4.3 kPa). High-dose PGE1 essentially inhibits hypoxic pulmonary vasoconstriction, at the expense of a deterioration in pulmonary gas exchange and systemic blood pressure in dogs.

Increased artificial deadspace ventilation is a safe and reliable method for deliberate hypercapnia.

To develop a simple method in an animal model to achieve deliberate hypercapnia, which can be used easily and safely to regulate the pulmonary vascular resistance without changing mean airway pressure and compromising oxygenation. Prospective study, with each animal used as its own control. Minipigs, weighing 11 to 14 kg (n = 7). A quadrilumen thermodilution pulmonary artery catheter was placed in minipigs via the internal jugular vein. Systemic blood pressure was measured with use of a femoral arterial catheter. The animals' lungs were ventilated with an FIO2 of 1.0, and a stable state of eucapnia was achieved and maintained for 30 mins. The artificial deadspace was increased every 30 mins, by connecting 45-mL (3- to 4-mL/kg) corrugated tube segments until a total deadspace volume of 180 mL was added. Hemodynamic performance was evaluated at baseline and after 45 mL (3 to 4 mL/kg), 90 mL (6 to 8 mL/kg), 135 mL (9 to 11 mL/kg), and 180 mL (12 to 15 mL/kg) of added deadspace. Data were indexed to the animal's weight (in kg). Increased artificial deadspace produced a significant (p < .05) increase in PaCO2. These increases in PaCO2 were associated with significant (p < .05) increases of 23%, 32%, 45%, and 46% in the mean pulmonary vascular resistance values, and 6%, 16%, 23%, and 23% in the mean pulmonary arterial pressure, respectively. The systemic pH was decreased from a mean baseline value of 7.45 to 7.39, 7.28, 7.20, and 7.11, respectively. There were no significant changes in PaO2, oxygen consumption, systemic vascular resistance, and cardiac output throughout the experiments. A gradual increase in artificial deadspace ventilation produces a state of deliberate hypercapnia. In our animal model, a moderate increase in artificial deadspace significantly increased the pulmonary vascular resistance but was not associated with detrimental respiratory acidemia. Larger volumes of added artificial deadspace had no detrimental effect on cardiac output, oxygen content, oxygen consumption, and systemic vascular resistance, but were associated with significant respiratory acidemia and therefore should be avoided.

Are patients chronically treated with β 1-adrenoceptor antagonists in fact β-blocked?

Objective : To determine cardiovascular β-receptor function in patients with ischemic heart disease chronically treated with β 1-adrenoceptor antagonists. Design : Prospective, single-blind, nonrandomized clinical trial. Setting : University Department of Cardiothoracic Anesthesia. Participants : Forty middle-age men scheduled for primary elective coronary artery bypass surgery. Twenty patients were treated with β 1-antagonists. Interventions : After induction of anesthesia, increasing intravenous bolus doses of isoproterenol were administered in order to increase heart rate more than 25 BPM. From this dose-response curve, the isoproterenol dose needed to increase heart rate by exactly 25 BPM was calculated. Measurements and Main Results : Baseline cardiovascular variables and the pharmacodynamic responses to isoproterenol were monitored with catheters in the radial and the pulmonary artery (thermodilution catheter). Heart rate was continuously calculated from the electrocardiogram. The hemodynamic status after induction of a standardized fentanyl anesthesia and the chronotropic and inotropic responses to the isoproterenol titration procedure were identical in the 20 β 1-blocked patients and in the 20 control patients. The median dose of isoproterenol needed to increase heart rate 25 BPM was 10.9 μg in the β-blocked patients and 9.4 μg in the control group. Conclusion : Patients chronically treated with β 1-antagonists compensate for the perturbation to such a degree that cardiovascular β-receptor function is in fact normal.

Lack of agreement between bioimpedance and continuous thermodilution measurement of cardiac output in intensive care unit patients.

BACKGROUND: Bolus thermodilution is the standard bedside method of cardiac output measurement in the intensive care unit (ICU). The Baxter Vigilance monitor uses a modified thermodilution pulmonary artery catheter with a thermal filament to give a continuous read-out of cardiac output. This has been shown to correlate very well with both the 'gold standard' dye dilution method and the bolus thermodilution method. Bioimpedance cardiography using the Bomed NCCOM 3 offers a noninvasive means of continuous cardiac output measurement and has been shown to correlate with the bolus thermodilution method. We investigated the agreement between the continuous bioimpedance and continuous thermodilution methods, enabling acquisition of a large number of simultaneous measurements. RESULTS: A total of 2390 paired data points from seven patients were collected. There was no correlation (r2 = 0.01) between the methods. The precision (1.16 l/min/m2) of agreement between the Vigilance and the Bomed, assessed by the Bland-Altam method, was very poor although the bias (-0.16 l/min/m2) appeared fair. CONCLUSIONS: The Bomed NCCOM 3 bioimpedance monitor shows poor agreement with the Baxter Vigilance continuous thermodilution monitor in a group of general ICU patients and cannot be recommended for cardiac output monitoring in this situation.

The use of esmolol in whole-body hyperthermia: Cardiovascular effects

Whole-body hyperthermia (WBH) is a well-described investigational adjunct to systemic chemotherapy for the treatment of advanced malignancies. The hemodynamic consequences of this physiologic state may include tachycardia, which can produce acute myocardial ischemia in patients with coronary artery disease. Ischemic heart disease is currently considered a contraindication to WBH. We chose to investigate the consequences of using a new β1-adrenergic antagonist, esmolol, to attempt to control the tachycardia associated with WBH. After institutional approval and patient consent, nine consecutive patients with normal cardiac function presenting for WBH with carboplatin infusion were studied. Along with standard monitors, radial arterial and oximetric thermodilution pulmonary artery catheters were placed. Patients were sedated and heated in a radiant warmer (Enthermics). Spontaneous ventilation was maintained and hemodynamic data were gathered at 37°C, and at 41.8°C (before, during and after esmolol infusion). Heart rate and cardiac output increased (by 46% (p = 0.001) and 35% (p=0.04) respectively) while mean arterial pressure and systemic vascular resistance fell (by 18% (p = 0.02) and 44% (p = 0.006) respectively) during hyperthermia. Heart rate was significantly reduced during esmolol administration (mean dose 180 μg/kg/min) in the absence of changes in cardiac index and calculated oxygen delivery. Ventricular filling pressures and stroke work were unchanged. No heart failure, pulmonary edema, or other adverse event was observed. Hemodynamic changes seen during esmolol administration were completely reversed 15 min after the infusion was stopped. We conclude that the administration of moderate doses of esmolol is safe for this population of patients undergoing WBH, and that this technique raises the question of whether patients with ischemic heart disease could safely undergo WBH.

Comparison of the Use of a Propofol Infusion in Cardiac Surgical Patients with Normal and Low Cardiac Output States

Objectives: This study compared the hemodynamic effects of a propofol infusion with fentanyl analgesia in patients undergoing cardiac surgery with normal and low cardiac output states. Low cardiac output was defined as a cardiac index less than 2.5 L/min/m2 with a minimum pulmonary capillary wedge pressure of 7 mmHg. Design: A prospective and open study. Setting: A single center cardiothoracic unit within a teaching hospital. Participants: Patients were assigned to group P, poor cardiac output or group N, normal cardiac output, after thermodilution pulmonary artery catheter assessments. Interventions: Both groups received a propofol infusion, 8 mg/kg/hr, until induction of anesthesia, followed by 4 mg/kg/hr until the intensive care unit. Fentanyl, 15 μg/kg, and pancuronium, 0.15 mg/kg, were administered after induction. The lungs were ventilated with oxygen. Measurements and Main Results: Hemodynamic assessments were repeated at intervals until cardiopulmonary bypass. Changes within and between groups were compared using t tests on percentage change from baseline. Group N had significantly greater decreases in cardiac index, stroke volume, and left ventricular stroke work index than group P. There were comparable decreases in mean arterial pressure on induction of anesthesia, 14% and 8% in group N and group P, respectively. In both groups, right ventricular ejection fraction was unchanged. Conclusions: The use of a propofol infusion for induction and maintenance of anesthesia in patients with low cardiac output states undergoing cardiac surgery is not contraindicated.

Mediastinal tube placement in children with pneumomediastinum

To describe the technique, hemodynamic response, and complication rate after the insertion of a percutaneous mediastinal tube for drainage of pneumomediastinum. A combined retrospective and prospective study in mechanically ventilated children with pneumomediastinum. Multidisciplinary pediatric intensive care unit at a children's hospital. The medical records and chest radiographs of 25 (15 retrospective and 10 prospective) patients who had placement of a mediastinal tube for drainage of pneumomediastinum from 1990 to 1995 were reviewed. Hemodynamic data were collected prospectively in the ten consecutive children from January 1994 to April 1995. Mediastinal tube placement: The subxyphoid area was cleansed with povidone-iodine and draped. An 18-gauge, thin-walled introducer needle was inserted 1 to 2 cm below the xyphoid process at an angle of 20 degrees from the anterior abdominal wall, directed at the substernal space. Either a 9-Fr or 11-Fr pericardiocentesis catheter was inserted over a wire and advanced to the third intercostal space. The catheter was secured and connected to 10 cm H2O suction, using a standard thoracostomy tube drainage device. The size of the mediastinal air column on a lateral chest radiograph was measured before and after placement of the mediastinal tube. The mean change in the size of the mediastinal air column was -1.6 cm (median -1.5, p < .001). In the ten prospective patients, hemodynamic data were recorded immediately before and after placement of a mediastinal tube from previously placed arterial and central venous pressure catheters. The mean hemodynamic changes after the mediastinal tube placement were: heart rate -4 beats/min (median = -1, p = .14); systolic blood pressure 16 mm Hg (median = 10, p = .007); diastolic blood pressure 11 mm Hg (median = 11, p = .005); mean arterial pressure 12 mm Hg (median = 8, p = .005); and central venous pressure -2 mm Hg (median = -1, p = .04). In four patients with pulmonary artery thermodilution catheters, the mean increase in cardiac index immediately following placement of the mediastinal tube was 34%. No complications, including bleeding, cardiac puncture, or infection occurred. These findings suggest that hemodynamic compromise commonly accompanies pneumomediastinum in children. Decompression of the mediastinal space and drainage of the pneumomediastinum, using this simple bedside technique for continuous drainage, can be performed rapidly and safely in children, resulting in immediate hemodynamic improvement, and allowing for continuous drainage.

Noninvasive physiologic monitoring of high-risk surgical patients.

To study the feasibility of multicomponent noninvasive monitoring, consisting of a new bioimpedance method for estimating cardiac output together with routine pulse oximetry and transcutaneous oximetry, and to compare physiologic data obtained noninvasively with hemodynamic and oxygen transport data obtained by standard invasive pulmonary artery thermodilution catheter to evaluate circulatory function in high-risk surgical patients. Prospective descriptive analysis of the time course of physiologic patterns in surgical patients. University-run county hospital. Seventy-one consecutively monitored, high-risk critically ill surgical patients in their perioperative period. Simultaneous measurements by invasive and noninvasive methods to describe and compare the temporal physiologic patterns of survivors and nonsurvivors. The new impedance cardiac output estimations closely approximated those of the thermodilution method (r = 0.82, P < .001). Episodes of hypotension, tachycardia, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oximetry, reduced oxygen delivery, and low oxygen consumption occurred with both groups but were more pronounced in the nonsurvivors than in the survivors. Noninvasive monitoring provided information similar to that of the thermodilution method. Both approaches indicated low flow and poor tissue perfusion (oxygenation) that was worse in the nonsurvivors. The multicomponent noninvasive monitoring provides continuous online, real-time displays of physiologic data that allow immediate recognition of circulatory dysfunction as well as the means to titrate therapy to appropriate predetermined therapeutic goals. The noninvasive systems are easy to apply, safe, inexpensive, reasonably accurate, and cost-effective.

Ultrafiltration after cardiopulmonary bypass in children: effects on hemodynamics, cytokines and complement

The purpose of the study was to evaluate the clinical and hemodynamic effect of intraoperative extracorporeal ultrafiltration (UF) and its potential in reducing the plasma concentration of circulating cytokines and complement activation products following open heart surgery in children. Eighteen children with congenital heart disease were prospectively randomized into a control group (n = 9) and a group who underwent UF (n = 9). Serial plasma samples for measurements of circulating cytokines (interleukin 6 (IL-6), tumor necrosis factor alpha (TNF), and its soluble receptor (sTNF receptor)), and complement factors (C3 activation products (C3a and C3bc) and terminal complement complex (TCC)) were obtained before, during and up to 48 h after cardiopulmonary bypass (CPB). A pulmonary artery thermodilution catheter was introduced preoperatively for hemodynamic monitoring. Postoperative hemodynamics were similar in both groups. Plasma levels of IL-6, sTNF receptors, C3a, C3bc and TCC increased significantly perioperatively (P < 0.01) in both groups. TNF was detected transiently in 16 patients perioperatively and in 4 of the 9 ultrafiltrate samples in concentrations similar to the plasma levels. Complement activating products were not detected in the ultrafiltration samples except for small amounts of C3a in two cases. Compared to the control group the plasma levels of C3a, C3bc and TCC were unaffected by the ultrafiltration procedure. The level of IL-6 and sTNF receptors increased significantly after 15 min of UF but there was no significant difference between the two groups postoperatively. In this study no clinical or hemodynamic effect was registered after UF. TNF and C3a were occasionally detected in the ultrafiltrate but we were unable to demonstrate reduction of these or any of the other markers tested in the group subjected to ultrafiltration.

Right ventricular function after coronary artery bypass grafting in patients with and without revascularization of the right coronary artery

To evaluate the influence of revascularization of a stenosis of the right coronary artery on right ventricular function. Prospective study. Single institutional study in a university hospital. 20 patients with different degrees of stenosis of the right coronary artery undergoing elective coronary artery bypass grafting. In 10 patients, bypass surgery included revascularization of a significant stenosis of the right coronary artery (group 1). In 10 other patients, the pathology of the right coronary artery was judged to be not significant, without indication for revascularization (group 2). Using the fast-response thermodilution pulmonary artery catheter, right ventricular function was estimated perioperatively. After termination of extracorporeal circulation, there was an increase in right ventricular volumes in group 2 (p < 0.05) and an initial decrease in group 1 (p < 0.05), with higher volumes in group 2 compared with group 1 (p < 0.05). The ejection fraction increased in group 1 (p < 0.05) and decreased in group 2 after operation (p < 0.05), with higher values in group 1 compared with group 2 (p < 0.05). In addition to these findings, the pressure-volume relationship showed a leftward and upward shift in group 1 and a rightward shift in group 2 postoperatively. These results indicate that right ventricular depression can occur after bypass grafting in patients with a moderate stenosis of the right coronary artery that is not revascularized. Revascularization of more severe stenosis of the right coronary artery appears to preserve postoperative right ventricular function.

Comparison of continuous with intermittent bolus thermodilution cardiac output measurements

Few complete studies have been published to validate the agreement between continuous cardiac output and intermittent thermodilution cardiac output. To analyze the agreement between cardiac output measurements by the continuous thermodilution method and the intermittent bolus thermodilution method, using a continuous cardiac output catheter in postoperative cardiothoracic surgery patients. A convenience sample of 14 adult cardiothoracic surgical patients with thermodilution pulmonary artery catheters placed preoperatively was used. A total of 214 comparison measurements of cardiac output by both the continuous and intermittent thermodilution methods were taken on patient admission to the critical care unit, every 4 hours, and with any change greater than 10% from baseline readings. The intraclass correlation between continuous cardiac output and intermittent cardiac output was .89. The limits of agreement were -1.34 to 1.18 L/min, indicating that in 95% of readings the difference between continuous cardiac output and intermittent cardiac output were within this range. The continuous cardiac output monitoring method shows clinically acceptable agreement with the intermittent cardiac output method.

Effects of thoracic epidural analgesia on coronary hemodynamics and myocardial metabolism in coronary artery bypass surgery

A possible influence of thoracic epidural analgesia on coronary hemodynamics and myocardial metabolism in coronary artery bypass grafting was investigated. The study was prospective and randomized. The study was performed in a university hospital. Thirty male patients less than 65 years of age and with ejection fraction greater than 0.5 participated. They were randomized into 3 groups: the high fentanyl (HF) group receiving high-dose fentanyl (55 micrograms/kg) anesthesia, the HF + thoracic epidural analgesia (TEA) group receiving the same general anesthesia plus thoracic epidural analgesia, and the low-fentanyl (LF) + TEA group receiving low-dose fentanyl (15 micrograms/kg) anesthesia plus thoracic epidural analgesia. A thoracic epidural catheter, a peripheral and central venous catheter, a radial artery catheter, a thermodilution pulmonary artery catheter, and a coronary sinus reverse thermodilution catheter were inserted. Coronary circulatory parameters, myocardial oxygenation, and myocardial substrate utilization were investigated before bypass and for 9 hours after bypass. Before bypass, the most striking finding was a reduction in myocardial lactate extraction in all groups, but also coronary flow and myocardial oxygen consumption decreased compared with baseline. After bypass, the only significant finding was a lower coronary vascular resistance early postoperatively in the epidural groups, but coronary blood flow was adequate in all groups. Myocardial metabolism was essentially unchanged both with and without epidural analgesia after bypass. With regard to the coronary circulation and myocardial metabolism, no hard data supporting the use of thoracic epidural analgesia in coronary artery bypass grafting were found.

Dopamine-1-receptor stimulation and mucosal tissue oxygenation in the porcine jejunum.

To evaluate the effects of dopamine-1-receptor stimulation on intestinal mucosal tissue oxygenation. Prospective, experimental, controlled trial. Animal research laboratory. Anesthetized domestic pigs (30 to 45 kg). A small segment of the jejunal mucosa and serosa was exposed by midline laparotomy and antimesenteric incision. Fenoldopam, a selective dopamine-1-receptor agonist, was infused in steps, exponentially increasing from 0.6 to 9.6 micrograms/kg/min via a central venous catheter (n = 8, fenoldopam group), whereas a second group (n = 6, saline group) was only given the solvent. Systemic hemodynamics as well as systemic and jejunal acid base and blood gas variables were measured using an arterial catheter, a thermodilution pulmonary artery catheter, and a jejunal venous catheter. Jejunal mucosal and serosal tissue PO2 were measured by means of Clark-type surface oxygen electrodes. Oxygen saturation and relative concentration of mucosal microvascular hemoglobin were measured by means of tissue reflectance spectrophotometry. In the fenoldopam group, systemic oxygen delivery (12.5 +/- 0.8 mL/kg/min at baseline) increased by 56% (p < .001) above baseline values. Mean arterial pressure remained unchanged. Fenoldopam produced a 51% increase in mucosal PO2 (23.8 +/- 2.8 torr [3.2 +/- 0.4 kPa] at baseline; p < .001) and a 31% increase in mucosal hemoglobin oxygen saturation (55.4 +/- 8.3% at baseline; p < .001), but not change in serosal PO2 (58 +/- 4.8 torr [7.7 +/- 0.6 kPa] at baseline). Fenoldopam improves tissue oxygenation of the porcine jejunum in a dose-related manner. This effect is limited to the inner mucosal layer. Dopamine-1-receptor agonists should be evaluated in patients presenting with signs of intestinal mucosal ischemia.

Comparison of the use of a propofol infusion in cardiac surgical patients with normal and low cardiac output states

This study compared the hemodynamic effects of a propofol infusion with fentanyl analgesia in patients undergoing cardiac surgery with normal and low cardiac output states. Low cardiac output was defined as a cardiac index less than 2.5 L/min/m2 with a minimum pulmonary capillary wedge pressure of 7 mmHg. A prospective and open study. A single center cardiothoracic unit within a teaching hospital. Patients were assigned to group P, poor cardiac output or group N, normal cardiac output, after thermodilution pulmonary artery catheter assessments. Both groups received a propofol infusion, 8 mg/kg/hr, until induction of anesthesia, followed by 4 mg/kg/hr until the intensive care unit. Fentanyl, 15 micrograms/kg, and pancuronium, 0.15 mg/kg, were administered after induction. The lungs were ventilated with oxygen. Hemodynamic assessments were repeated at intervals until cardiopulmonary bypass. Changes within and between groups were compared using t tests on percentage change from baseline. Group N had significantly greater decreases in cardiac index, stroke volume, and left ventricular stroke work index than group P. There were comparable decreases in mean arterial pressure on induction of anesthesia, 14% and 8% in group N and group P, respectively. In both groups, right ventricular ejection fraction was unchanged. The use of a propofol infusion for induction and maintenance of anesthesia in patients with low cardiac output states undergoing cardiac surgery is not contraindicated.

A comparison between the haemodynamic effects of oral nifedipine and intravenous dihydralazine in patients with severe pre-eclampsia

To compare the effects of a single oral dose of nifedipine with those of intravenous dihydralazine on central haemodynamics in pregnant women with severe pre-eclampsia. A prospective comparative study. The High Risk Obstetric Unit, University Hospital Rotterdam Dijkzigt, Rotterdam. Twenty patients with severe pre-eclampsia between 27 and 35 weeks gestation with normal cardiac filling pressures and without fetal distress. A pulmonary artery thermodilution catheter and a radial artery line were placed. Ten patients chewed a 10-mg capsule of nifedipine and 10 patients received dihydralazine by intravenous infusion at a rate of 1-3 mg/h. Arterial pressures, heart rate, cardiac output and pulmonary capillary wedge pressure were determined before and after drug administration. Fetal condition was continuously monitored by cardiotocography. The reduction in arterial blood pressure obtained with both drugs was similar, and was associated with a similar rise in heart rate and cardiac output and a similar reduction in systemic vascular resistance. Pulmonary capillary wedge pressures decreased significantly less with nifedipine than with dihydralazine. Signs of fetal distress occurred in none of the nifedipine-treated patients, but in five of the patients treated with dihydralazine. From the haemodynamic viewpoint nifedipine seems to be a useful agent in the treatment of hypertensive emergencies in pregnancy.

Continuous haemodynamic monitoring in children: use of transoesophageal Doppler

A wide range of invasive and non-invasive techniques for monitoring the haemodynamic condition of critically ill patients is now available. A general reluctance on the part of paediatric intensive care specialists to use pulmonary artery thermodilution catheters and the need for constant realignment of hand-held Doppler probes has necessitated the search for a technique which is relatively non-invasive and provides continuous information on the haemodynamic condition of critically ill paediatric patients. We sought to establish if transoesophageal Doppler fulfilled these criteria. Eleven children who had recently undergone cardiac surgery were studied. Median age was 39 months and weight 14.9 kg. Five simultaneous pairs of measurements of cardiac index (CI: thermodilution) and minute distance (MD: transoesophageal Doppler) were made, as a baseline, when each child was haemodynamically stable. Following a fluid challenge, five repeat pairs of measurements were made. The mean percentage changes for CI and MD were 16.4% (range 5.3-44%) and 16.6% (3.4-47.7%), respectively. The average coefficients of variation for measurements of CI and MD were 3.5% and 2.9%, respectively. The mean difference in percentage change between CI and MD was -0.5% (95% confidence interval for the bias -4% to 3%; limits of agreement -10.7 to +9.7%). Our study indicates that transoesophageal Doppler is reproducible, easy to use and provides clinically acceptable information when following changes in CI in haemodynamically stable paediatric patients.

The effect of patient position on the reproducibility of cardiac output measurements

To determine the effect of patient position on the reproducibility of cardiac output measurements. Prospective, two-group quasi-experimental design. Convenience sample. The study involved two intensive care units in two adult acute care hospitals. Thirty patients admitted to the intensive care unit who had a thermodilution pulmonary artery catheter in place. Ages ranged from 39 to 80 years (mean of 66.4 +/- 11.3 years). Thermodilution cardiac output measurements. The subjects were placed in one of two groups, initially by flipping a coin then into alternate groups. Group A subjects were placed supine, and after 5 minutes had cardiac output measurements performed. They were then placed in the 45-degree upright position, and after an additional 5 minutes had cardiac output measurements performed. Group B subjects were first placed in the 45-degree upright position, and after 5 minutes had cardiac output measurements performed. They were then placed in the supine flat position, and after an additional 5 minutes had cardiac output measurements performed. Seventy percent (n = 30) of the sample population displayed a lower cardiac output in the 45-degree upright position than that obtained in the supine position, with the decrease ranging from 1% to 32% (mean decrease 11%). Forty percent (n = 30) of cardiac output measurements obtained in the 45-degree upright were greater than or equal to 10% less than those obtained in the supine flat position. The differences in cardiac output were analyzed with the paired t test. which produced a 95% confidence interval from -0.539 to -0.083. The two-group Wilcoxon test was used to analyze the mean cardiac output with the patient in the supine, flat position and in the 45-degree upright position. The mean cardiac output at 0 degrees was found to be statistically significant higher (p = 0.0083) than the mean cardiac output at 45 degrees. The effect of coexisting variables was analyzed with the Kruskal-Wallis. The use of vasoconstrictors was the only variable that had a statistically significant change in cardiac output associated with a change in position. These results indicate that cardiac output measurements are affected by alterations in patient position. To ensure accurate comparisons between consecutive cardiac output measurements, the researchers recommend that the position in which the cardiac output measurements are performed be documented and the cardiac output measurements be conducted in a uniform position.

Application of a transpulmonary double indicator dilution method for postoperative assessment of cardiac index, pulmonary vascular resistance index, and extravascular lung water in children undergoing total cavo-pulmonary anastomosis: preliminary results in six patients

Total cavo-pulmonary anastomosis (TCPA) is used for the functional correction of an increasing spectrum of congenital heart diseases. The passive pulmonary perfusion after surgical exclusion of the right ventricle has significant implications for the postoperative hemodynamic management of these patients. Because conventional pulmonary artery thermodilution catheters present methodologic problems in patients after TCPA, important cardiovascular variables such as cardiac index (CI) and pulmonary and systemic vascular resistance indices (PVRI, SVRI) usually cannot be assessed directly. In a preliminary series of six patients undergoing TCPA (age 6–22 years), the applicability of a transpulmonary double indicator dilution technique for postoperative determinations of CI, PVRI, SVRI, and extravascular lung water (EVLW) was investigated. After central venous injection of ice-cold indocyanine green (5 mg), thermal and dye dilution curves were recorded in the abdominal aorta using a combined 4F fiberoptic thermistor catheter. Qualitative assessment of the tracer curves did not show major differences in measurements in patients with pulsatile perfusion of the lungs. CI, SVRI, and EVLW could be determined by use of standard algorithms. Pulmonary perfusion pressure for the calculation of PVRI was based on the gradient between central venous and left atrial pressure. The quality of indicator dilution curves allowed determination of flow-related variables in 33 of a total of 34 sets of measurements. No catheter-related problems occurred during or after the period of investigation. Postoperative EVLW was within the range that is commonly accepted as normal for adults. Mean PVRI initially decreased during the postoperative course but showed a significant increase after extubation. It was concluded that a transpulmonary double indicator dilution method using combined thermal/fiberoptic detection in the abdominal aorta can be usefully applied for extended hemodynamic monitoring in children and young adults undergoing TCPA.

Injectate port selection affects accuracy and reproducibility of cardiac output measurements with multiport thermodilution pulmonary artery catheters

To compare the accuracy and reproducibility of thermodilution cardiac output measurements obtained from the injectate and infusion ports of a multilumen pulmonary artery catheter. The thermodilution results were compared with an independent measure of flow obtained from an electromagnetic flow meter. In an experimental study conducted at an animal research laboratory of a health sciences university, two virgin western breed ewes were surgically instrumented with an inferior vena cava occluder, which reduced venous return and thus lowered cardiac output, and an ascending aortic electromagnetic flow probe, which provided an independent reference measure of cardiac output. On the day of study, a multilumen pulmonary artery catheter was inserted. Cardiac output was manipulated over a range of 2.9 to 12.1 L/min with i.v. isoproterenol or inferior vena cava occlusion. Approximately 30 simultaneous thermodilution and electromagnetic flow meter measurements of cardiac output were obtained from both the infusion and injectate ports in each of the two subjects. Correlation coefficients were lower and standard error of the estimates was higher for the infusion port (r = .83; SEE = 1.19 L/min) vs the injectate port (r = .94; SEE = .74 L/min), indicating reduced reproducibility with infusion port thermodilution cardiac output determinations. Accuracy was also adversely influenced in the infusion port results. The linear regression for the infusion port data intercepted the Y axis at +2.64 L/min, indicating significant overestimation of cardiac output at flows of less than 5 L/min and underestimation of flow when cardiac output exceeded 8 L/min. The use of the infusion port for the measurement of thermodilution cardiac output measurements may result in nonreproducible and inaccurate results.