Superior Vena Cava Pressure Research Articles

One and One-Half Ventricle Repair: Results and Concerns

The study was designed to assess the long-term results of one and one-half ventricular repair on systemic and pulmonary circulation, right ventricular growth and function, and the prevalence of arrhythmias. Eighty-four patients undergoing one and one-half ventricular repair between January 1990 and December 2003 were studied. Age was 4 to 504 months (mean, 47.9 +/- 57.3 months). Sixty-nine survivors underwent serial echocardiography, radionuclide studies, cardiac magnetic resonance imaging, and cardiac catheterization. Operative and late mortality were 10.7% and 8%, respectively. Perioperative and postoperative supraventricular arrhythmias were observed in 14.3% and 15.9% of patients, respectively. Risk factors for supraventricular arrhythmias included systemic ventricular dysfunction, heterotaxy syndrome, and Ebstein's anomaly. Mean late postoperative superior vena caval pressure was 14.2 +/- 1.52 mm Hg and right atrial pressure was 6.6 +/- 0.74 mm Hg. At a median follow-up of 87 months, actuarial survival was 81.9% +/- 0.04%, and 89.8% were in New York Heart Association class I or II. Serial cine-magnetic resonance imaging demonstrated significant growth of tricuspid valve and right ventricular cavity in 45% of patients. One and one-half ventricular repair can be performed with an acceptable risk. The operation maintains a low pressure in the inferior vena caval tributaries, and reverses the Fontan paradox. Patients with tripartite right ventricles demonstrated a tendency toward enlargement of the pulmonary ventricular chamber commensurable with somatic growth.

Paroxysmal cough injury, vascular rupture and‘shaken baby syndrome’

It is widely assumed that subdural and retinal haemorrhage in infants can only result from traumatic rupture of vulnerable blood vessels. An alternative aetiology, that of vascular rupture resulting from excessive intraluminal pressure, is presented in three disease conditions. (1) Perlman et al., studying premature neonates requiring mechanical ventilation for respiratory distress syndrome, observed "cough-like" fluctuations in oesophageal pressure greater than 18 cms H2O, whose timing matched fluctuations in anterior cerebral artery flow. When 14 out of 24 neonates were paralysed (to prevent abdominal muscle activity) intraventricular haemorrhage developed in all 10 controls but in only one of the paralysed group during paralysis. (2) New analysis of pressure data extracted from a previous study of prolonged expiratory apnoea showed alveolar collapse induced 100 mmHg intrathoracic cough pressure surges. Superior vena cava pressures up to 50 mmHg were implied, and radial artery systolic pressures over 180 mmHg recorded. (3) Bordetella pertussis bacteria attach to cilia in the airways, but do not invade the underlying tissue. The irritation causes the powerful coughing paroxysms of whooping cough. Brain haemorrhages and retinal detachment have been observed to result from the high intravascular pressures produced. The data suggest that any source of intense airway irritation not easily removed (laryngeal infection, inhalation of regurgitated feed, fluff, smoke etc.) could induce similar bleeding, a paroxysmal cough injury (PCI). Additional objective evidence of inflicted trauma is necessary to distinguish between 'shaken baby syndrome' and PCI.

Cerebral ischemia caused by obstructed superior vena cava cannula is detected by near-infrared spectroscopy

Objective: Bicaval venous cannulation is being used with increasing frequency in neonates and infants to avoid circulatory arrest. However, superior vena cava (SVC) cannula obstruction may result in cerebral ischemia with no change in blood pressure or mixed venous O 2 saturation. The authors hypothesized that near-infrared spectroscopy (NIRS) would allow noninvasive detection of SVC cannula obstruction. Methods: Fifteen Yorkshire piglets (9.07 ± 0.20 kg) underwent total cardiopulmonary bypass (CPB) (100 mL/kg/min, pH-stat strategy, hematocrit of 20%) with ascending aortic and bicaval cannulations. Femoral arterial and SVC pressure were monitored as well as mixed venous O 2 saturation. NIRS monitoring of tissue oxygenation index (TOI) as well as oxyhemoglobin and deoxyhemoglobin (HHb) was undertaken. Animals were cooled to an esophageal temperature of 25°C over 20 minutes. CPB flow was reduced to 50 mL/kg/min for 20 minutes. Animals then underwent a 60-minute study period of continuous CPB at 50 mL/kg/min with manipulation of the SVC cannula: group 1, open; group 2, partial occlusion; and group 3, complete occlusion. Animals were rewarmed to 37°C at full flow with the SVC cannula open. Cerebral blood flow was assessed at onset of CPB, at end of cooling, at end of low flow, at end of SVC manipulation period, and at end of rewarming using radioactive microspheres. Results: CBF decreased to 27.9 ± 1.5 mL/min/100 g with complete occlusion ( p < 0.01 v group 1: 39.7 ± 1.9, group 2, 38.3 ± 2.0 mL/min/100 g) with no change in arterial pressure or mixed venous saturation. There were also significant differences in cerebral oxygen delivery between group 3 and other groups ( p < 0.01). SVC pressure increased to 19.5 ± 4.5 and 32.5 ± 3.1mmHg with partial and complete occlusion. NIRS indicated significant cerebral ischemia with a decrease in TOI ( p < 0.05; group 3 v group 1 and 2) and an increase in HHb ( p < 0.05; group 3 v group 1). At the end of the study, significant acidosis was found in group 3 compared with group 1 ( p < 0.05). Conclusion: SVC cannula obstruction causes cerebral ischemia with no change in blood pressure or venous oxygen saturation. In view of the difficulties and risks of CVP monitoring in babies, it is recommended to use other monitoring modalities such as NIRS to assess adequacy of cerebral perfusion if bicaval cannulation is used in neonates and infants.

The clinical investigation of extracorporeal vein bypass during lobectomy combined with superior vena cava graft for lung cancer

To evaluate the benefits of three methods of extracorporeal vein bypass from superior vena cava (SVC) to femoral vein during lobectomy and SVC graft in patients with lung cancer. Fifty-five cases selected from the patients with lung cancer who had undergone lobectomy combined with SVC graft by sortilege were divided into 3 groups: blood discarding group ( n =20), blood drainage group ( n =20) and extracorporeal bypass group ( n =15). The mean arterial pressure (MAP) and SVC pressure were continuously monitored during the SVC graft. Hemoglobin (Hb) was measured before and during the SVC clamping and after the SVC off clamping. During SVC clamping, the patients in extracorporeal bypass group had a significantly lower SVC pressure than blood discarding group and blood drainage group, and there were significant decreases in MAP and Hb and increase in blood loss in blood discarding group than the other two groups. All the patients underwent a smooth operation and safely returned to intensive care unit. None of them involved any neurologically injured signs and symptoms. Extracorporeal SVC bypass can maintain a very stable hemodynamics and low SVCP during SVC resection and artificial vessel graft, which is an avail of brain perfusion and blood saving.

Successful Fontan procedure for asplenia with pulmonary atresia and major aortopulmonary collateral arteries

Asplenia with a single ventricle and major aortopulmonary collateral arteries (MAPCAs) is a rare congenital cardiac anomaly. In this patient group achievement of the Fontan procedure depends on ample rehabilitation of the pulmonary arteries to secure sufficient pulmonary vascular beds and the prevention of progressive pulmonary vascular obstructive disease. Here we report a successful 1-stage bilateral unifocalization of the pulmonary blood supply followed by a staged Fontan procedure in a patient with a univentricular heart and MAPCAs. Clinical Summary The patient was given a diagnosis of asplenia, univentricular heart (right ventricular type), common atrioventricular orifice, pulmonary atresia, bilateral superior vena cavas, total anomalous pulmonary venous connection (intracardiac type), and MAPCAs on the basis of echocardiography and cardiac catheterization. His neonatal aortography showed a small central pulmonary artery (3 mm in diameter) and bilateral multiple MAPCAs (Figure 1, A). The patient’s arterial oxygen saturation (Sa O2) was around 80%, and his pulmonary/systemic blood flow ratio (Qp/Qs) was 1.6 with stable hemodynamics. Subsequent cardiac catheterization at 6 month of age revealed a good-sized central pulmonary artery (Figure 1, B) and 5 large MAPCAs. His SaO2 was approximately 87%, and his Qp/Qs had increased to 3.7. At 1 year of age, he underwent a primary complete unifocalization of his bilateral pulmonary arteries, total anomalous pulmonary venous connection repair for progressive pulmonary venous obstruction (Figure 2), and a left modified Blalock-Taussig shunt (polytetrafluoroethylene [PTFE],* 5 mm). The postoperative course was uneventful except for transient bilateral phrenic nerve palsy. He subsequently did well, while becoming increasingly cyanotic. A catheterization at 2 years of age revealed peripheral pulmonary stenosis, low pulmonary vascular resistance (1.2 Wood units), and normal pulmonary blood flow (Qp/Qs 1.0). The patient then underwent a bilateral bidirectional cavopulmonary shunt and take down of his left modified Blalock-Taussig shunt without cardiopulmonary bypass. This postoperative course was also uneventful, with an SaO2 of 85% and superior vena caval pressure of 10 mm Hg. Eight months after the bilateral bidirectional cavopulmonary shunt, a cardiac catheterization was performed, demonstrating good-shaped pulmonary arteries (Figure 3), low pulmonary vascular resistance (1.4 R*U), low pulmonary artery pressure (mean, 10 mm Hg), and low pulmonary blood flow (Qp/Qs 0.8). Two weeks before definitive surgical intervention, he underwent balloon angioplasty for peripheral pulmonary stenoses and coil embolization of aortopulmonary collateral arteries. At 3 years of age, a fenestrated modified Fontan procedure was performed. An 18-mm PTFE tube graft with a 4-mm PTFE tube graft anastomosed in end-to-side fashion was used for the extracardiac total cavopulmonary connection. The 4-mm PTFE tube graft was anastomosed to the common atrium as a fenestration. The patient was hemodynamically stable intraoperatively, with superior vena caval and inferior vena caval pressures of 11 mm Hg, a common atrial pressure of 4 mm Hg, and an SaO2 of 94%. The patient returned to the cardiovascular intensive care unit in stable condition and was extubated 3 hours after the operation. His postoperative course was uneventful. He was transferred to the general ward on the first postoperative day and discharged home 13 days later without any complications. Three months after the Fontan procedure, another cardiac catheterization was performed, demonstrating a spontaneously occluded tube graft fenestration, an Sa O2 of 96%, low pulmonary artery pressure (mean, 12 mm Hg), and excellent Fontan circulation.

Upper extremity peripheral venous pressure measurements accurately reflect pulmonary artery pressures in patients with cavopulmonary or Fontan connections.

After the bidirectional cavopulmonary or Fontan operation, the physiologic consequence is passive flow of the systemic venous return to the pulmonary arteries. Knowledge of pulmonary artery pressure (PA) is valuable in the management of these patients, and obtaining this information without the need for a central line or cardiac catheterization would be advantageous. The aim of this study was to evaluate the correlation between upper extremity peripheral venous (PV) pressures and PA or superior vena cava (SVC) pressures in patients who have undergone cavopulmonary or Fontan connections. During cardiac catheterization, 19 patients with complex cyanotic heart disease who had undergone a cavopulmonary shunt or Fontan procedure were studied. Simultaneous pressure measurements were obtained from the peripheral intravenous line placed prior to the procedure and the SVC or PA. The mean pressures were compared. The mean PV pressure was 17.5 +/- 5.6 mmHg. The mean SVC or PA pressure was 16.1 +/- 5.4 mmHg. The mean difference was 1.5 +/- 1.5 mmHg ( p < 0.001). The correlation coefficient PV to SVC or PA pressure was 0.97 ( p < 0.001). PV pressure measurements taken from an upper extremity accurately reflect PA pressures in patients who have undergone a cavopulmonary shunt or Fontan procedure.

Procoagulant and anticoagulant factor abnormalities following the fontan procedure: increased factor VIII may predispose to thrombosis

Objective Using age-matched controls, this study prospectively evaluated coagulation factor abnormalities and hemodynamic variables in children who had undergone the Fontan operation. Methods Coagulation factors were assayed in 20 children (mean age 6.4 ± 2.9 years), at a mean 3.7 ± 2.3 years after the Fontan procedure; 24 healthy children (mean age 6.8 ± 2.8 years) were assayed as controls. Concentration of factors II, V, VII, VIII, IX, X; ATIII; plasminogen; proteins C and S; fibrinogen; serum albumin; and liver enzymes were measured. Normal reference intervals based on the control patients were determined using 95% confidence limits. Patient demographic, hemodynamic variables, and elapsed time after the Fontan procedure were evaluated as possible predictors of coagulation abnormalities. Results Concentrations of protein C; factors II, V, VII, X; plasminogen; and ATIII were significantly lower in Fontan patients compared with age-matched controls ( P < .01); factor VIII was significantly elevated in 6 patients (35%), 2 of whom had a thromboembolic event. A higher superior vena cava pressure was predictive of an elevated factor VIII level ( P = .003). No other specific hemodynamic variables were predictive of a procoagulant or anticoagulant abnormality. Conclusion Procoagulant and anticoagulant factor levels were significantly lower in patients after the Fontan operation independent of hemodynamic variables peculiar to the Fontan circulation. Increased factor VIII level requires further evaluation as a cause of thrombosis in patients with Fontan physiology and may also indicate a subset of these patients in whom anticoagulation is indicated.

Peri-operative comparison of different transient external shunt techniques in bidirectional cavo-pulmonary shunt.

In patients with functional single ventricular physiology, the avoidance of cardiopulmonary bypass offers many advantages including earlier extubation, decreased necessity of inotropic support, improved hemodynamical status and reduced likelihood of post-operative prolonged pleural effusion. We believe that the bidirectional cavopulmonary anastomosis operations may be performed with transient external shunt techniques. The purpose of this prospective study is the peri- and post-operative comparison of different transient external shunt methods used in bidirectional cavopulmonary shunt operations. Between years 1997 and 2000, 30 patients have undergone bidirectional cavo-pulmonary shunt operation by using three different types of external shunt. The mean patient age was 13 months (range, 3 months-3 years). Previous operations had been performed in ten patients (33%). All patients were divided into three groups according to type of external shunt used. In group A (ten patients), the transient external shunt was constructed between superior vena cava and right atrium by uniting two standard venous cannulas with a Y-connector. In group B (ten patients), the external shunt was performed with a single short venous cannula constructed between superior vena cava and right atrium. In group C (ten patients), the external shunt was constructed between superior vena cava and left pulmonary artery by using a single short venous cannula. During operation, central venous pressure (CVP), arterial O(2) saturation and mean arterial blood pressure were recorded continuously. All operations are completed without the establishment of cardiopulmonary bypass. Hospital mortality was 3.3%. One patient in group A died because of low cardiac output at the end of postoperative day 2. All patients were extubated within 4h. In groups A-C mean superior vena caval pressures were measured 28, 24 and 21 mmHg, respectively during superior vena cava-right pulmonary artery anastomosis. In both groups A and B patients, arterial O(2) saturation decreased to a minimum 53+/-2 and 53+/-2%, respectively during the operation. In the group C, minimum arterial O(2) saturation was measured 82+/-2%. Although mean arterial pressure decreased in all groups during clampage; in group C patients, this drop is not significant. Based on the study presented here, bidirectional cavo-pulmonary anastomosis can be carried out by using different types of transient external shunt. The best hemodynamical condition and arterial O(2) levels were achieved with the shunt constructed between superior vena cava and left pulmonary artery.

Central Venous Catheter Tip and Perforation

In Response: Drs. Caruso, Gravenstein et al. make several important points about cardiac and great vessel perforation risk with central venous catheters (CVC). Their data in adults delineating the location of the pericardial reflection are important and reinforce the concept that placement of the catheter tip in the proximal superior vena cava (SVC) is the desired location in these patients, reducing the likelihood of cardiac tamponade in case of SVC perforation. Another potential advantage of a CVC in the proximal SVC during cardiac surgery with bypass involving bicaval cannulation is that SVC pressure can be measured as an indicator of cerebral venous drainage, although other modalities such as near infrared spectroscopy may be a more sensitive indicator of SVC obstruction (1). To our knowledge, no similar study of the location of the pericardial reflection has been done in pediatric patients, particularly in infants. In small pediatric patients, the SVC is often short, i.e., 4–5 cm total length, leaving little room for error in placement. If the CVC is placed too far cephalad in a short SVC, a proximal port, which is 1–1.5 cm from the tip, may not be intravascular, leading to extravasation of important or caustic drugs and fluids (2). The pericardium is usually incised in congenital heart surgery patients, providing drainage in case of perforation. Thus, we believe that a CVC tip position in the mid or distal SVC of a small patient is acceptable. We agree that if at all possible, CVC should be parallel to the SVC wall, and believe that this, along with keeping the CVC tip above the right atrium, and using a “soft” catheter material such as soft polyurethane, are the most important principles in pediatric patients to prevent perforation. For this reason, we avoid left internal jugular or subclavian lines unless there is no other option. In our study (3), we originally intended to derive formulae for left sided catheters as well, but only 11 of 463 CVC (2.4%) were left sided over a 1-year period. Besides increased perforation risk, the reason to avoid left sided CVC in congenital heart surgery patients is the existence of a persistent left sided SVC in 5–10% of these patients, which drains to the coronary sinus or left atrium in most cases (4). Rather than a left sided CVC, we currently place femoral venous central lines. Central venous pressure in the inferior vena cava (IVC) is identical to that in the SVC in pediatric patients without increased abdominal pressure or IVC obstruction (5). If a left sided CVC must be placed, the tip should be either in the distal SVC near the SVC-right atrial junction, where it is likely to be parallel to the vein wall, or at the midline in the innominate vein parallel to its wall, where perforation risk is minimal. Pigtail catheters are indeed made only in adult 7 fr sizes. In a controlled study in adults, pigtail versus standard CVC were compared in 205 patients (6). There was no difference in perforation rate, (none in either group attributable to the CVC), but there was more difficulty in insertion of the pigtail catheters, compared with standard CVC. We would be concerned that a pediatric pigtail catheter would have distal tip diameter comparable with the width of the SVC in small patients, increasing risk of SVC thrombosis, which is a devastating complication in small infants, with a high mortality rate (7). Imaging all CVC as soon as possible to determine tip location should be done to detect and correct malposition. When available, transesophageal echocardiography to assist during placement of the CVC is a highly accurate method of ensuring a location in the SVC (8). Dean B. Andropoulos, MD Stephen A. Stayer, MD

Central Venous Catheter Tip and Perforation

In Response: Drs. Caruso, Gravenstein et al. make several important points about cardiac and great vessel perforation risk with central venous catheters (CVC). Their data in adults delineating the location of the pericardial reflection are important and reinforce the concept that placement of the catheter tip in the proximal superior vena cava (SVC) is the desired location in these patients, reducing the likelihood of cardiac tamponade in case of SVC perforation. Another potential advantage of a CVC in the proximal SVC during cardiac surgery with bypass involving bicaval cannulation is that SVC pressure can be measured as an indicator of cerebral venous drainage, although other modalities such as near infrared spectroscopy may be a more sensitive indicator of SVC obstruction (1). To our knowledge, no similar study of the location of the pericardial reflection has been done in pediatric patients, particularly in infants. In small pediatric patients, the SVC is often short, i.e., 4–5 cm total length, leaving little room for error in placement. If the CVC is placed too far cephalad in a short SVC, a proximal port, which is 1–1.5 cm from the tip, may not be intravascular, leading to extravasation of important or caustic drugs and fluids (2). The pericardium is usually incised in congenital heart surgery patients, providing drainage in case of perforation. Thus, we believe that a CVC tip position in the mid or distal SVC of a small patient is acceptable. We agree that if at all possible, CVC should be parallel to the SVC wall, and believe that this, along with keeping the CVC tip above the right atrium, and using a “soft” catheter material such as soft polyurethane, are the most important principles in pediatric patients to prevent perforation. For this reason, we avoid left internal jugular or subclavian lines unless there is no other option. In our study (3), we originally intended to derive formulae for left sided catheters as well, but only 11 of 463 CVC (2.4%) were left sided over a 1-year period. Besides increased perforation risk, the reason to avoid left sided CVC in congenital heart surgery patients is the existence of a persistent left sided SVC in 5–10% of these patients, which drains to the coronary sinus or left atrium in most cases (4). Rather than a left sided CVC, we currently place femoral venous central lines. Central venous pressure in the inferior vena cava (IVC) is identical to that in the SVC in pediatric patients without increased abdominal pressure or IVC obstruction (5). If a left sided CVC must be placed, the tip should be either in the distal SVC near the SVC-right atrial junction, where it is likely to be parallel to the vein wall, or at the midline in the innominate vein parallel to its wall, where perforation risk is minimal. Pigtail catheters are indeed made only in adult 7 fr sizes. In a controlled study in adults, pigtail versus standard CVC were compared in 205 patients (6). There was no difference in perforation rate, (none in either group attributable to the CVC), but there was more difficulty in insertion of the pigtail catheters, compared with standard CVC. We would be concerned that a pediatric pigtail catheter would have distal tip diameter comparable with the width of the SVC in small patients, increasing risk of SVC thrombosis, which is a devastating complication in small infants, with a high mortality rate (7). Imaging all CVC as soon as possible to determine tip location should be done to detect and correct malposition. When available, transesophageal echocardiography to assist during placement of the CVC is a highly accurate method of ensuring a location in the SVC (8). Dean B. Andropoulos, MD Stephen A. Stayer, MD

Pressures in the superior and inferior vena cava and intra-abdominal pressure

Pressures in the superior and inferior vena cava and intra-abdominal pressure

PH-stat blood gas management provides better cerebral perfusion during deep hypothermic retrograde cerebral perfusion

We performed a retrospective comparative clinical study to evaluate whether pH-stat (n=14) or alpha-stat strategy (n=15) provides better perfusion or oxygen metabolism during hypothermic retrograde cerebral perfusion (RCP). The pH-stat group showed significantly lower superior vena cava (SVC) pressure (21+/-4 versus 27+/-6 mmHg, P<0.0001), apparently lower retrograde cerebral vascular resistance index (7.4+/-2.1 versus 10.1+/-3.8 dynes/s cm(-5) m(-2), P=0.009) but there were no significant differences in RCP flow index, oxygen supply or oxygen extraction between groups. Further studies are necessary to determine which blood gas management is better for RCP, however, pH-stat strategy should be useful in deep hypothermic RCP.

Bidirectional Glenn Shunt: 170 Cases

Between June 1997 and July 2000, 170 patients aged 0.5 to 20 years received a bidirectional Glenn shunt without the use of a temporary shunt or cardiopulmonary bypass. Arterial oxygen saturation rose from 78% ± 8.5% preoperatively to 90% ± 4.3% postoperatively. Hemodynamic studies showed a mean postoperative superior vena cava pressure of 13 ± 2 mm H2O. One patient had desaturation and the shunt was taken down, 5 required reexploration for bleeding, and 8 needed prolonged drainage of 9 to 19 days, 2 of whom had chylothorax. Hospital stay was 9.3 ± 3.5 days. There were 3 late operative deaths (1.8%) from low output syndrome. In 20 patients, bilateral bidirectional Glenn shunts were instituted. Three patients under-went a subsequent Fontan procedure without cardiopulmonary bypass. The bidirectional Glenn shunt remains an excellent palliative procedure as a preliminary step to a Fontan operation, or as an integral part of a Fontan or modified Fontan operation when the procedure is deferred because of age, weight, or cardiac malformations characterized by a hypoplastic right or left ventricle.

Association between increased central venous pressure and hydrocephalus in children undergoing cardiac catheterization. A prospective study.

The relationship between increased central venous pressure (CVP) and development of hydrocephalus has been extensively discussed in the neuropediatric literature. However, the possibility of a direct connection has not been systematically examined. The purpose of this prospective study was to examine whether there was a correlation between elevated CVP and hydrocephalus in children undergoing cardiac catheterization. We used cardiac catheterization to measure the right atrial and superior vena caval pressure in 37 children (mean age 30 months) with congenital heart malformations. The children had CVP higher than normal (mean 10.2+/-3.1 mmHg, range 4-18). To evaluate the size of the lateral and fourth ventricles, we performed CT scans of the brain on each child. Abnormal scans were found in 15/37 children, showing brain atrophy (12/37), ventriculomegaly (3/37), and focal infarction (1/37). Cerebral atrophy was more likely to occur in young children (P<0.001). The average head circumference among these children was less than 2SD below the mean for healthy children of comparable ages. Using a correlation coefficient regression model, no relationship was found between CVP and ventricular diameters or head circumference. These results argue against the hypothesis that mild to moderately elevated venous pressure is involved in the mechanism and development of pediatric hydrocephalus.

Invited commentary

This is another helpful paper from the Toronto Hospital for Sick Children. Postoperative pericardial and pleural effusions are not uncommon, especially in postoperative patients with certain congenital heart diagnoses. Conditions that result in elevated right atrial or superior vena caval pressures not infrequently have pericardial and pleural effusions postoperatively, and it is not surprising that the large database from Toronto confirms prior findings that those same patients are the ones more likely to experience chylous effusions. The authors also remind us that the increased lymphatic permeability associated with the lymphatic dysplasia contributes to chylous effusions (7 of 16 chylopericardium patients had Trisomy 21). Although the reported overall incidence of chylous pericardium is low, a full 15% of symptomatic postoperative pericardial effusions that required drainage were chylous in nature. Not surprisingly, 15% of the patients with an associated chylous pleural effusion had chylous pericardial effusions.In this series only 2 patients, once their diagnosis of chylous pericardial effusion was established could be treated with diet alteration alone, most requiring pericardial drainage by means of a tube or a pericardial window. Only 3 thoracic duct ligations were done, and all were associated with chylous pleural and pericardial drainage. It is important to note that in the authors’ experience, failure to respond to aspirin or anti-inflammatory medical treatment for pericardial effusion occurred in 8 of the 16 patients and raised the suspicion that the effusion was, in fact, chylous. The findings of this study support the observations of many that patients with both pleural and pericardial effusions postoperatively should be suspected of having chylous effusions, especially if the postoperative courses have been associated with elevated pressures in the superior vena cava or right atrium. If the patient is a child with Trisomy-21, the titer of suspicion should be much higher. This is another helpful paper from the Toronto Hospital for Sick Children. Postoperative pericardial and pleural effusions are not uncommon, especially in postoperative patients with certain congenital heart diagnoses. Conditions that result in elevated right atrial or superior vena caval pressures not infrequently have pericardial and pleural effusions postoperatively, and it is not surprising that the large database from Toronto confirms prior findings that those same patients are the ones more likely to experience chylous effusions. The authors also remind us that the increased lymphatic permeability associated with the lymphatic dysplasia contributes to chylous effusions (7 of 16 chylopericardium patients had Trisomy 21). Although the reported overall incidence of chylous pericardium is low, a full 15% of symptomatic postoperative pericardial effusions that required drainage were chylous in nature. Not surprisingly, 15% of the patients with an associated chylous pleural effusion had chylous pericardial effusions. In this series only 2 patients, once their diagnosis of chylous pericardial effusion was established could be treated with diet alteration alone, most requiring pericardial drainage by means of a tube or a pericardial window. Only 3 thoracic duct ligations were done, and all were associated with chylous pleural and pericardial drainage. It is important to note that in the authors’ experience, failure to respond to aspirin or anti-inflammatory medical treatment for pericardial effusion occurred in 8 of the 16 patients and raised the suspicion that the effusion was, in fact, chylous. The findings of this study support the observations of many that patients with both pleural and pericardial effusions postoperatively should be suspected of having chylous effusions, especially if the postoperative courses have been associated with elevated pressures in the superior vena cava or right atrium. If the patient is a child with Trisomy-21, the titer of suspicion should be much higher.

Factors influencing arterial oxygenation early after bidirectional cavopulmonary shunt without additional sources of pulmonary blood flow

Objectives: Although the arterial oxygen saturation after bidirectional cavopulmonary shunting should theoretically be homogeneous if additional pulmonary flow is obliterated, the arterial oxygen saturation has been found to vary in clinical practice. Knowledge of the preoperative and operative determinants of arterial oxygen saturation early after bidirectional cavopulmonary shunting may lead to a better understanding of this unique physiology. Methods: Thirty-five patients who underwent bidirectional cavopulmonary shunting with obliteration of additional pulmonary flow were included in this study. The arterial oxygen saturation was determined at the 5 time points over a 48-hour period. Multivariable regression analysis was used to identify the independent predictors of the arterial oxygen saturation. Results: No significant interval changes occurred in the arterial oxygen saturation during the 48 hours after bidirectional cavopulmonary shunting, which ranged from 61.6% to 95.6%. There was a significant inverse correlation between the postoperative superior vena cava pressure and the arterial oxygen saturation (P =.003). A low arterial oxygen saturation early after bidirectional cavopulmonary shunting was a predictor of mortality or exclusion from univentricular repair within 24 months (P =.012, odds ratio = 1.14). Of 11 factors identified by univariable analysis, multiple regression analysis indicated that age less than 8 months at the time of shunting (P <.0001) and ventricular volume overload (P =.002) predicted a lower arterial oxygen saturation after bidirectional cavopulmonary shunting. Conclusions: Even without additional sources of pulmonary blood flow, several preoperative factors, including younger age and severe ventricular volume overload, predicted a decrease in the arterial oxygen saturation early after bidirectional cavopulmonary shunting. This, in turn, predicted poor outcome during 2 years of follow-up. (J Thorac Cardiovasc Surg 2000;120:589-95)

Is maintained cranial hypothermia the only factor leading to improved outcome after retrograde cerebral perfusion? An experimental study with a chronic porcine model

Background: Previous studies have shown that retrograde cerebral perfusion can improve neurologic outcome after prolonged hypothermic circulatory arrest. Here we have compared two temperatures of retrograde cerebral perfusion (15°C and 25°C) with hypothermic circulatory arrest at systemic hypothermia of 25°C to clarify whether the possible benefit of retrograde cerebral perfusion may only be due to improved cooling effect. Methods: Eighteen pigs (23-27 kg) were randomly assigned to undergo 15°C retrograde cerebral perfusion at systemic hypothermia of 25°C, 25°C retrograde cerebral perfusion at 25°C systemic hypothermia, or hypothermic circulatory arrest at 25°C for 40 minutes. Flow was adjusted to maintain superior vena cava pressure at 20 mm Hg during retrograde cerebral perfusion. Hemodynamic, electrophysiologic, metabolic, and temperature monitoring were performed until 4 hours after the start of rewarming. Daily behavioral assessment was done until death or until the animals were killed on day 7. Histopathologic analysis of the brain was carried out on all animals. Results: Epidural temperatures were lower in the 15°C retrograde cerebral perfusion group during the intervention ( P < .05). In the 15°C retrograde cerebral perfusion group, 4 (67%) of 6 animals survived for 7 days compared with 3 (50%) of 6 in both the 25°C retrograde cerebral perfusion and hypothermic circulatory arrest groups. The median total histopathologic score was 5 in the 15°C retrograde cerebral perfusion group and 7 in the 25°C retrograde cerebral perfusion group ( P = .04). Conclusions: These findings suggest that enhanced cranial hypothermia is the major beneficial factor of retrograde cerebral perfusion when careful attention is paid to its implementation. (J Thorac Cardiovasc Surg 2000;119:1021-9)

Cold retrograde cerebral perfusion improves cerebral protection during moderate hypothermic circulatory arrest: A long-term study in a porcine model

Background: Deep hypothermic circulatory arrest is an effective method of cerebral protection, but it is associated with long cardiopulmonary bypass times and coagulation disturbances. Previous studies have shown that retrograde cerebral perfusion can improve neurologic outcomes after prolonged hypothermic circulatory arrest. We tested the hypothesis that deep hypothermic retrograde cerebral perfusion could improve cerebral outcome during moderate hypothermic circulatory arrest. Methods: Twelve pigs (23-29 kg) were randomly assigned to undergo either retrograde cerebral perfusion (15°C) at 25°C or hypothermic circulatory arrest with the head packed in ice at 25°C for 45 minutes. Flow was adjusted to maintain superior vena cava pressure at 20 mm Hg throughout retrograde cerebral perfusion. Hemodynamic, electrophysiologic, metabolic, and temperature monitoring were carried out until 4 hours after the start of rewarming. Daily behavioral assessment was performed until elective death on day 7. A postmortem histologic analysis of the brain was carried out on all animals. Results: In the retrograde cerebral perfusion group, 5 (83%) of 6 animals survived 7 days compared with 2 (33%) of 6 in the hypothermic circulatory arrest group. Complete behavioral recovery was seen in 4 (67%) animals after retrograde cerebral perfusion but only in 1 (17%) animal after hypothermic circulatory arrest. Postoperative levels of serum lactate were higher, and blood pH was lower in the hypothermic circulatory arrest group. There were no significant hemodynamic differences between the study groups. Conclusions: Cold hypothermic retrograde cerebral perfusion during moderate hypothermic circulatory arrest seems to improve neurologic outcome compared with moderate hypothermic circulatory arrest with the head packed in ice. (J Thorac Cardiovasc Surg 1999;118:938-45)

Postoperative brain complications following retrograde cerebral perfusion.

This study was undertaken to investigate the neurological risk factors associated with the retrograde cerebral perfusion (RCP) technique, by examining the relationship between intraoperative parameters and post-operative brain complications. A total of 12 patients who underwent surgery for thoracic aortic aneurysms using the RCP technique were included in this study. Profound hypothermia was induced through cardiopulmonary bypass which was established with a femoral arterial cannula and bicaval return. During RCP, a venous drainage cannula from the superior vena cava (SVC) was switched over to the arterial return circuit, and oxygenated blood was retrogradely infused through the SVC. The perfusion flow rate was maintained at 273 +/- 113 ml/min and the SVC pressure was maintained at 15 +/- 6 mmHg. The RCP time was 68 +/- 27 min with a range of 27-130 min, and the lowest rectal temperature was 16 +/- 1 degrees C. The total elapsed time until emergence from anesthesia after the operation was 12 +/- 6 h. The operation time correlated with the awakening time (r = 0.729, P = 0.0088). Longer RCP times of up to 101 and 130 min tended to result in post-operative brain damage. The lowest rectal temperature also correlated with the awakening time (r = 0.697, P = 0.0149), and an inverse correlation between the SVC pressure and the awakening time was observed (r = -0. 727, P = 0.0091). These findings demonstrate the importance of reducing both the RCP and operation times to decrease the incidence of brain damage. If carried out under optimal conditions, including perfusion pressure and brain temperature, RCP could be marginally prolonged safely without causing major neurological complications.

Bidirectional Glenn shunt in association with congenital heart repairs: the 1 [formula omitted] ventricular repair

Background. The bidirectional Glenn shunt has been used to incorporate a smaller tripartite ventricle into the circulation and create pulsatile pulmonary artery flow. We reviewed our operative experience and assessed hemodynamics of the bidirectional Glenn shunt in 1 1 2 ventricular repair or in conjunction with other repairs of congenital heart defects. Methods. Between 1992 and 1998, 15 patients (mean age, 8.1 ± 7.9 years) had bidirectional Glenn shunt in association with repair of congenital heart defects. Eighty-seven percent had at least one previous operation. All patients had simultaneous or previous intracardiac repair and had bidirectional Glenn shunt to volume unload the small right ventricle (group A, n = 7), to unload the poorly functioning right ventricle (group B, n = 2), to redirect superior vena cava–pulmonary venous atrial connection to treat cyanosis (group C, n = 2), or to unload the pulmonary left ventricle for residual intracavitary hypertension in patients with L-transposition of the great arteries, ventricular septal defect, and pulmonary stenosis (group D, n = 4). Intraoperative hemodynamic assessment was done in 2 patients in group A by selective use of inflow occlusion and flow probes. Results. All patients survived. Four patients had successful, concurrent arrhythmia circuit cryoablation for Wolf-Parkinson-White syndrome (n = 1) or atrial reentry tachycardia (n = 3). Superior and inferior vena caval flow averaged 36% and 64% of cardiac output, respectively. Postoperative superior vena caval pressure (n = 13) was 13.7 ± 4.0 mm Hg with pulmonary arterial flow pattern contributed by the ventricle in systole (pulsatile) and the superior vena cava in diastole (laminar). Conclusions. The bidirectional Glenn shunt is an effective adjunct to congenital heart repair to treat pulmonary ventricular pressure-volume problems and anomalous superior vena caval to left atrial connections.