Asian Cardiovasc Thorac Ann 1998;6:295-299
© 1998 Asia Publishing EXchange Pte Ltd
Technique to Monitor Pulmonary Artery Pressure After Pediatric Cardiac Surgery
Kanchi Muralidhar, MD,
Devi Prasad Shetty, MS1
Department of Cardiac Anaesthesia
1 Department of Cardiac Surgery Manipal Heart Foundation Bangalore, India
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For reprint information contact: Kanchi Muralidhar, MD Department of Cardiac Anaesthesia Manipal Heart Foundation 98 Rustom Bagh Airport Road Bangalore 560017, India Tel:91 80 528 7749 Fax:91 80 526 8912 Email:mhfbg{at}giasbg01.vsnl.net.in
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ABSTRACT
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Pulmonary hypertensive crisis is a recognized cause of sudden deterioration and death after correction of congenital heart disease. In phase 1 of this study, pulmonary artery pressure was monitored continuously in 200 high-risk children aged 9 days to 5 years using pulmonary artery pressure monitoring lines inserted through the right internal jugular vein. The success rate for placement of catheter tips in the pre-incision period was not high but all could be placed in the pulmonary artery before right atrial closure prior to separation from cardiopulmonary bypass. Complications related to the technique were transient ventricular or atrial arrhythmias during insertion and slipping or coiling of the catheter in the right ventricle. Carotid arterial puncture in 2 patients and pneumothorax in another 2 were additional complications. In phase 2, the directly measured pulmonary artery pressure was compared to that measured by echocardiography in 20 high-risk patients aged 7 days to 10 years weighing 2.6 to 26 kg. Systolic pulmonary artery pressure ranged from 16 to 58 mm Hg (mean, 38.1 ± 12.5 mm Hg) measured by the catheter and 21 to 54 mm Hg (mean, 39.7 ± 11.7 mm Hg) measured by echocardiography, showing excellent correlation (r = 0.97). Our study indicates that percutaneous insertion of a pulmonary artery pressure line in infants and children undergoing open-heart surgery is safe and practical for those at risk of postoperative pulmonary hypertensive crisis.
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INTRODUCTION
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A major challenge in pediatric cardiology is to understand and control postoperative pulmonary hypertensive crises (PHC). In patients with increased pulmonary blood flow as a result of a large left-to-right shunt, pulmonary capillaries become muscularized and react to various stimuli. Patients with truncus arteriosus, atrioventricular septal defect, or total anomalous pulmonary venous drainage are most at risk. However, PHC can complicate the postoperative course of other operations such as ventricular septal defect repair, aortopulmonary window, or the arterial switch operation for neonatal transposition.1 Postoperative mortality has been attributed to acute rises in pulmonary artery pressure and pulmonary vascular resistance. However, incidents of PHC have been sporadically described, their etiology is unclear, and therapy remains empirical.2–4
A pulmonary artery catheter in patients at risk of developing PHC is extremely useful for the diagnosis and management of such crises. Continuous monitoring of pulmonary arterial pressure is advantageous in the management of life-threatening episodes of pulmonary vasoconstriction because it allows prompt recognition of the cause of clinical deterioration, ensures accurate use of pulmonary vasodilators, and avoids the inevitable delay during the passage of a floatation catheter into the pulmonary artery. In addition, pulmonary artery pressure monitoring is a useful guide in determining the time of weaning from mechanical ventilation. Transthoracic catheters are practical but have a significant incidence of complications such as intrapericardial bleeding on removal, leading to hypotension or cardiac tamponade.5 Swan-Ganz catheters are expensive, technically difficult to insert, and time consuming in small infants.
This study was conducted in two phases. In phase 1, we evaluated the safety and efficacy of pulmonary artery pressure monitoring lines inserted percutaneously through the right internal jugular vein. In phase 2, the directly measured pulmonary arterial pressure via a monitoring line was compared with that obtained by echocardiography in infants and children undergoing open-heart surgical procedures.
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PATIENTS AND METHODS
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Phase 1 of this study involved 200 pediatric patients less than 5 years of age in whom percutaneous insertion of a pulmonary artery pressure monitoring line was employed. Institutional approval and parental consent was obtained before performance of the procedure. All patients in this study had severe pulmonary hypertension preoperatively and PHC was expected to complicate the postoperative course. Preanesthetic medication consisted of oral trimeprazine and atropine, anesthesia was induced with O2 and halothane or sevoflurane and maintained with oxygen, halothane or isoflurane, pancuronium bromide, morphine, and intermittent positive-pressure ventilation after endotracheal intubation. Cardiopulmonary bypass was established using the standard technique with a membrane oxygenator and cold crystalloid cardioplegia. In 20 patients, deep hypothermia and circulatory arrest were employed. Cardiopulmonary bypass was terminated with the aid of dopamine, dobutamine, or isoprenaline infusions. Continuous infusion of glyceryl trinitrate, sodium nitroprusside, or phenoxybenzamine was used for control of pulmonary arterial pressure. All patients were electively ventilated postoperatively until they were considered fit for tracheal extubation.
For the purpose of continuous pressure measurement, catheters were placed percutaneously after anesthetic induction and endotracheal intubation. The right internal jugular vein was identified with a polytetrafluoroethylene intravenous cannula (Venflon 2, 22G/32 mm; BOC Ohmeda, Helsingborg, Sweden) and cannulated with a hydrophilic hydrometer coated polyurethane Hydrocath 22G/10 cm or 20G/15–20 cm central venous catheter (Ohmeda Ltd, Swindon, Wiltshire, UK) using the Seldinger technique. The full length of the catheter was inserted at this stage under sterile conditions to ensure sufficient length for positioning the tip of the catheter into the pulmonary artery. All catheters were inserted by the first author who has over 15 years of experience in cardiac anesthesia. The catheter was connected to a pressure transducer but no attempt was made at this stage to direct the catheter tip into the pulmonary artery. A triple-lumen catheter of appropriate size was also inserted either through the right internal jugular vein or the femoral vein for central venous pressure measurement and administration of vasoactive agents.
After the surgical repair when the cardiac chambers were still open and before the termination of cardiopulmonary bypass, the pulmonary artery pressure line was adjusted by the surgeon so as to position its tip in the pulmonary artery. Care was taken to avoid inclusion of the catheter in the sutures used to close the cardiac chambers. Prior to closure of the chest, the patency and function of the pressure monitoring catheter was confirmed, excess line was withdrawn, and the external end of the catheter was sutured to the skin. The position of the monitoring line was checked postoperatively by a chest radiograph. Pulmonary arterial pressure was monitored continuously by the pressure transducer and the catheter was flushed intermittently with heparinized saline solution. The standard catheter care protocol was observed in the intensive care unit. Treatment was initiated and modified on the basis of pulmonary artery pressure measurements and systemic venous oxygen saturation. The pulmonary artery pressure line was removed electively after discontinuation of mechanical ventilation and tracheal extubation, irrespective of the presence of a chest tube drain. Incidents of complications were noted.
Phase 2 of the study was conducted on 20 additional patients at high risk of developing PHC. The anesthetic management and insertion of the pulmonary artery pressure catheter were carried out as described for phase 1. Pulmonary arterial pressure was measured both directly through the catheter and indirectly by transthoracic or transesophageal echocardiography using the tricuspid regurgitation method. In this method, the pressure gradient between the right ventricle and the right atrium during systole is estimated by measuring the maximal velocity of the regurgitant jet and the right ventricular systolic pressure is estimated by adding the pressure gradient to the right atrial pressure.6 The numerical data were expressed as mean ± standard deviation. Linear regression analysis was employed for calculation of the correlation coefficient.
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RESULTS
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Phase 1
The demographic and other data of the 200 patients enrolled over a period of 4 years in phase 1 of the study are shown in Table 1
. The youngest patient, an infant with transposition of the great arteries, was 9 days old and the eldest was a 5-year-old child with a ventricular septal defect and severe pulmonary arterial hypertension. The preoperative diagnoses of the patients are shown in Table 2. After establishing cardiopulmonary bypass and during intracardiac repair, the majority of the pulmonary artery pressure lines were found coiled in the right atrium (126), some were coiled in the right ventricle (38), a few had reached the pulmonary artery (14), and the remainder (22), were in the inferior vena cava. Before closure of the cardiac chambers, the catheter tip was positioned in the pulmonary artery. The time taken to insert the line varied from 5 to 10 minutes and this did not unduly extend the period of anesthesia. The presence of an extra monitoring line in the surgical field was not considered to be an inconvenience and avoiding the need to place a transthoracic monitoring line was considered advantageous. Complications related to the use of the pulmonary artery pressure line are shown in Table 3. It is worth noting that complications such as bleeding on removal and catheter retention that can be encountered with the transthoracic route were totally eliminated.
Phase 2
The demographic and diagnostic data of the 20 patients in phase 2 of the study are shown in Tables 1
and 2. The mean (± standard deviation) systolic pulmonary arterial pressure measured by the catheter was 38.1 ± 12.5 mm Hg (range, 16 to 58 mm Hg) and that measured by echocardiography was 39.7 ± 11.7 mm Hg (range, 21 to 54 mm Hg). The correlation coefficient was 0.97.
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DISCUSSION
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Increased pulmonary artery pressure and pulmonary vascular resistance after repair of congenital heart disease with a left-to-right shunt or pulmonary venous obstruction is a recognized cause of sudden postoperative deterioration and death. The presence of a large left-to-right shunt may lead to hypertrophy of the media of the pulmonary arteries with extension of muscle from the media into the acinar arteries and arterialization of the pulmonary veins. Such changes are most marked in patients with total anomalous pulmonary venous drainage who have large left-to-right shunts and pulmonary venous hypertension but they have also been described in infants with isolated nonrestrictive ventricular septal defects7,8 PHC is thought to result from the interaction of pulmonary vascular endothelium with platelets and leukocytes. Platelets and leukocytes degranulate after hypothermic cardiopulmonary bypass and release potent vasoconstrictive agents, in particular thromboxanes and leukotrienes.9 Episodes of PHC are potentially fatal but respond to early diagnosis and treatment. Specific monitoring in the form of continuous pulmonary artery pressure measurement is definitely indicated in high-risk patients.
Pulmonary arterial pressure can be monitored using Swan-Ganz catheters in adults and older children. A transvenous pulmonary artery catheter may be placed using the balloon floatation method via the internal jugular approach in children weighing more than 7 kg. A 5 F catheter is used for those with body weights between 7 and 25 kg.10 In neonates, the insertion of a 4 F Swan-Ganz catheter requires a cut-down of the external jugular or the right internal jugular vein.11 Although Pollack and colleagues12 reported the successful passage of 22 floatation catheters in children, only 25% of his patients were below 12 kg of body weight, time taken for the passage of the catheter exceeded one hour in 50% of cases, and 5 catheters had to be removed within 24 hours because of catheter-related problems. Thus, Swan-Ganz catheters are technically difficult to insert in infants and small children and frequently require fluoroscopy. In addition, they are expensive and small Swan-Ganz catheters are not readily available in many centers including ours.
The second alternative is to use a transthoracic catheter for measurement of pulmonary arterial pressure which provides important physiologic data, but carries a small but real risk of serious complications. Complications reported after transthoracic insertion of intracardiac monitoring lines are of two general types: (1) catheter retention, the catheter cannot be physically removed at the time desired and this requires local exploration, subxiphoid removal, or reexploration after sternotomy; (2) intrapericardial bleeding, sequelae of this bleeding include increased chest tube drainage (10 to 20 mL·kg–1), transfusion for volume or hemoglobin repletion, bleeding of sufficient severity to prompt reexploration and suturing of the insertion site, cardiac tamponade requiring cardiopulmonary resuscitation or reexploration sternotomy, and death. In a series of 5666 pediatric patients and 6690 transthoracic intracardiac monitoring lines, the pulmonary artery pressure catheters had the highest rate of complications and these were also the most serious including cardiac tamponade, cardiac arrest, and death.5 In a series of 45 selected infants and children with transthoracic pulmonary artery pressure monitoring lines, 43% of the patients needed transfusion; the blood loss related to catheter removal was replaced either with crossmatched blood or plasma protein fraction, two catheters were difficult to remove, and one death was indirectly related to catheter removal.13
As an alternative to Swan-Ganz catheters and transthoracic monitoring lines, we routinely use the technique of percutaneous insertion of a pulmonary artery pressure line in high-risk infants and children. Use of this technique was reported in 4 patients in a series of 20 high-risk infants and neonates where the monitoring line was placed percutaneously via the internal jugular vein.14 Our experience with the use of this technique has demonstrated that the method is safe, simple, practical, and cost-effective in patients undergoing open cardiac surgical procedures. It has the advantage of avoiding bleeding after removal of the catheter in the intensive care unit.15 However, it is unsuitable for insertion in patients in the intensive care unit as it requires the surgeon to position the catheter tip in the pulmonary artery in the operating room when the cardiac chambers are open. The most common complication associated with this technique was a transient arrhythmia due to contact of the catheter tip or guidewire with the right ventricle during insertion, which did not require any treatment other than withdrawal of the catheter or guidewire by 1 to 2 cm. The catheter is not flow directed and hence the majority of these catheters need readjustment by the surgeon to position the tip in the pulmonary artery. The second phase of our study demonstrated an excellent correlation between the percutaneously monitored pulmonary arterial pressure and that measured by echocardiography. However, echocardiography although noninvasive, suffers from the disadvantage that it is not continuous and hence likely to miss the onset of an acute unexpected crisis.
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Acknowledgments
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The authors are greatly indebted to the staff members of the Departments of Cardiac Surgery, Anaesthesia, and Echocardiography at B.M. Birla Heart Research Centre, Calcutta, and Manipal Heart Foundation, Bangalore, for their cooperation and help in conducting this study.
Presented at The 10th Annual Meeting of the European Association of Cardiothoracic Anaesthesiologists, Madrid, Spain, June 15–17, 1995 (Phase 1) and at The World Conference of Anaesthesiologists, Sydney, Australia, April 14–20, 1996 (Phase 2).
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ABSTRACT
INTRODUCTION
