540019 case-report2014
PRF0010.1177/0267659114540019PerfusionIssitt et al.
Case Report
Tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral vessels
Perfusion 2014, Vol. 29(6) 567–570 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0267659114540019 prf.sagepub.com
RW Issitt,1,2 DA Robertson,1 RM Crook,1 NT Cross,1 M Shaw1 and VT Tsang2,3
Abstract Major aortopulmonary collateral arteries (MAPCAs) provide significant issues during cardiopulmonary bypass, including flooding of the surgical field which requires significant blood volumes to be returned to the extracorporeal circuit via handheld suckers. This has been shown to be the major source of gaseous microemboli and is associated with adverse neurological outcome. Use of pH-stat has been previously shown to decrease the shunt through MAPCAs via an unknown mechanism. Here, we report the associated benefits of pH-stat in decreasing sucker usage and gaseous microemboli in a patient with known MAPCAs presenting for repair of tetralogy of Fallot and pulmonary atresia. Keywords cardiac anatomy/pathologic anatomy; CPB; physiology/pathophysiology; collateral blood flow (lungs); CHD; tetralogy of Fallot; embolism (gaseous)
Case Report Cyanotic congenital cardiac lesions are commonly associated with aortopulmonary collateral vessels, representing a physiological shunt that, during cardiopulmonary bypass (CPB), results in reduced systemic perfusion due to the lower pressure throughout the pulmonary system.1 The result of this is a flooded surgical field in which the surgeon will ask for reduced flow to enable visualisation of the cardiac structures; this exacerbates the reduced systemic flow and lower perfusion pressures. Intervention with vasoconstrictive agents to reverse the lower systemic pressures initiates a downward spiral of increased field flooding and reducing CPB output. Sakamoto et al. introduced a method for calculating systemic pulmonary collateral circulation (SPCC), which involved the measurement of arterial and venous flow; venous flow representing the systemic circulation and the difference between arterial and venous being the percentage of flow passing through the collateral vessels.1 A 7-month-old female presented with tetralogy of Fallot and pulmonary atresia for surgical repair. The patient also had a right-sided aortic arch with aberrant left subclavian artery giving rise to a large tortuous duct, providing pulmonary blood flow, an anomalous right upper pulmonary vein (RUPV) draining into the right atrium and a large left superior vena cava (SVC) draining
into the left atrium. There was also right lung hypoplasia with obliterated pleural space. It was also noted that a large bore major aortopulmonary collateral artery (MAPCA) could be seen on echocardiography (ECHO), although it was difficult to determine the exact origination of the vessel. The operative plan was to perform a full Fallot’s repair to allow the child to grow before repair of the anomalous RUPV (there was concern that the Warden’s procedure would cause obstruction from the right SVC). A median sternotomy was performed and bypass was established in the normal manner. After 1Department
of Clinical Perfusion, Great Ormond Street Hospital, London, UK 2Institute of Cardiovascular Science, University College London, UK 3Department of Cardiothoracic Surgery, Great Ormond Street Hospital, London, UK Corresponding author: Mr Richard Issitt Department of Clinical Perfusion Great Ormond Street Hospital Level 3 Cardiac Theatres Morgan Stanley Clinical Building Great Ormond Street London, WC1N 3JH UK. Email: [email protected]
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
568
Perfusion 29(6)
0.8 0.7
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Time
Figure 1. GME, Venous flow and pCO2 data.
A: aortic cross-clamp; B: initiation of pH-stat; C: removal of the cross-clamp. pCO2 values given at α-stat levels.
ligation and division of the patent ductus arteriosus (PDA), the ventricular septal defect (VSD) was closed and a 5mm Gore-Tex® tube was used for the right ventrical-pulmonary artery (RV-PA) conduit through a limited right ventriculotomy. The left SVC was snared at the beginning of the operation and clipped to approximately half its original size following weaning from CPB. Full ligation of the left SVC was not undertaken to prevent venous congestion. On right atriotomy, visualisation of the cardiac structures was limited due to the volume of blood returning from the pulmonary veins, particularly the anomalous
RUPV; the only source of blood flow to which was through collateral vessels. This led to an increased reliance on the handheld suckers, with a noted increase in the number of gaseous microemboli detected from the outlet of the venous reservoir (BCC200, GAMPT mbH, Merseberg, Germany) and a drop in systemic venous return as measured via the venous flow probe (Figure 1). The corresponding SPCC represented 28.3% of the total cardiac output from the CPB circuit. Previous studies have shown that an increased CO2 content limits the collateral blood flow via an unknown mechanism in patients cooled to nasopharyngeal temperatures of
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
569
Issitt et al.
27-28°C1 and so, blood gas management was changed from alpha-stat to pH-stat with a view to reducing the temperature once the pCO2 had reached 5.3kPa (pHstat; 8kPa α-stat). There was an immediate increase in venous return and an associated decrease in suction blood return to a SPCC of 1.3% (95.4% reduction, corresponding to a 40% decrease in suction pump revolutions per minute requirement) as the CO2 content increased, despite remaining at approximately 34°C (range 33.8-35.1°C). The number of microemboli entering the circuit also dramatically dropped, representing the decreased sucker requirement and increased systemic flow. Cerebral near-infrared spectroscopy (NIRS) increased from 61% to 76% with the increase in pCO2. No change was observed with the reduction in pCO2 following cross-clamp release. Following release of the cross-clamp, blood gas management was reverted to alpha-stat management (Figure1). The haematocrit fell slightly during the operation from 32% preoperatively to 28% at the end of CPB. This was increased to 40% following modified ultrafiltration. The total CPB time was 19 minutes and the cross-clamp time 12 minutes. The cardiac index remained above 3 L/min/m2 (0.60.62 L/min) and lactate below 2 mmol/L throughout the procedure, suggesting adequate systemic perfusion was achieved. No neurological sequelae were observed during the hospital stay and the patient continues to do well in the outpatient setting. The CPB circuit consisted of the Baby RX05 oxygenator and hard-shell venous reservoir (Terumo, Tokyo, Japan) with a 3/16x1/4 tubing set. The Stöcket S5™ (Stöckert, Sorin Group GmbH, Munich, Germany) heart-lung machine with pole-mounted roller pumps was used with a 3T™ heater/chiller (Stöckert, Sorin Group). The total base prime volume was 330 mL. This consisted of packed red blood cells (PRBC) of the patient’s blood group, a synthetic colloid (Gelofusine, B. Braun Melsungen AG, Melsungen, Germany), a crystalloid (Plasmalyte A, Baxter, Norfolk, UK) with mannitol 20% w/v (Mannitol, Baxter, Thetford, UK) 2.5 mL/kg and heparin 1000 unit/mL, 1.5 mL (Wockhart, Wrexham, UK). Biochemical compatibility was then attained using sodium bicarbonate as a buffering agent. The patient was systemically cooled to a nasopharyngeal temperature of 34°C and myocardial protection was achieved with 30 mL/kg of cold blood cardioplegia (4:1 blood:cardioplegia to a final concentration of 20 mmol) of St Thomas’s Solution (Harefield Formulation, IVEX Pharmaceuticals, Larne, Northern Ireland). pH-stat blood gas management was achieved by adding CO2 into the gas supply up to a temperature-corrected value of 5.3 kPa. Bicaval cannulation was achieved using 14Fr and 16Fr venous cannulae (DLP, Medtronic Inc, Kerkrade, the Netherlands). A vent was placed into the left atrium. Measurement of the SPCC was undertaken
with a flow probe (Stöckert, Sorin Group GmbH) placed onto the venous line of the CPB circuit, as previously described.1 Cerebral saturation was monitored using NIRS placed on both left and right forehead (Foresight, CAS Medical Systems, Branford, CT, USA).
Comment The presence of MAPCAs in paediatric patients with cyanotic anomalies will vary, depending on the severity of the cyanosis and the age of the patient and is an important risk factor in surgical repair.2 Whilst pH-stat blood management has long been associated with increase cerebral blood flow, previous studies have shown how pH-stat management, in conjunction with deep hypothermia, has also decreased the systemic pulmonary collateral circulation.1 However, the original research by Sakamoto et al. used a roller pump inserted into the venous line as a crude measurement of venous return. There are problems associated with this; it creates a mechanical obstruction to passive venous flow and creates an unintentional possibility of user bias. Our method of measuring venous flow removed both of these factors. There are several possibilities as to the exact mechanisms by which the CO2 phenomenon is achieved. Firstly, the vasodilatation of the cerebral vessels caused by pH-stat may decrease the systemic vascular resistance and, thereby, produce a path of lesser resistance. During pH-stat, NIRS increased (61% to 76%), suggesting cerebral vascular dilatation. However, the heart-lung bypass machine calculates the systemic vascular resistance (SVR) throughout the bypass period with an SVR before initiation of pH-stat of 6711.61 dyne·sec·cm−5 and during pH-stat of 6483.54 dyne·sec·cm−5. Therefore, a change of 228.07 dyne·sec·cm−5 seems unlikely to explain the decrease in SPCC from 28.3% to 1.3% of total cardiac output from the CPB circuit. However, the SVR should not be viewed as an absolute measure because of the influence of the collateral flow vessels and should be regarded as indicative only. The second mechanism may be a direct effect on the pulmonary vasculature of either CO2 or an associated factor (such as decreased pH). Morray and colleagues have previously observed a correlation between the percentage of inspired CO2, mean pulmonary artery pressure and pulmonary vascular resistance index, suggesting a pulmonary vasodilating effect of the CO2mediated alkolosis.3 Further work by Chang et al. confirmed this, but also found the effect occurred in the presence of unaltered PaCO2, suggesting pH rather than CO2 is the contributing factor.4 However, this scenario does not fit with CPB, as pH-stat blood gas management keeps the pH unaltered and allows the pCO2 to rise. Therefore, further research is required to elucidate the exact mechanism that occurs.
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
570
Perfusion 29(6)
In conclusion, in a patient with pulmonary atresia and tetralogy of Fallot, we found that the use of pHstat blood gas management was associated with decreased systemic pulmonary collateral circulation and a dramatic decrease in GME entrained from the handheld suckers. We believe that this is the first report indicating this effect in conjunction with mild hypothermic conditions and presents a refined method of measuring SPCC. Declaration of conflicting interest The authors declare that there is no conflict of interest.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
References 1. Sakamoto T, Kurosawa H, Shin‘oka T, Aoki M, Isomatsu Y. The influence of pH strategy on cerebral and collateral circulation during hypothermic cardiopulmonary bypass in cyanotic patients with heart disease: results of a randomized trial and real-time monitoring. J Thorac Cardiovasc Surg 2004; 127: 12–19. 2. Ichikawa H, Yagihara T, Kishimoto H, et al. Extent of aortopulmonary collateral blood flow as a risk factor for Fontan operations. Ann Thorac Surg 1995; 59: 433–437. 3. Morray JP, Lynn AM, Mansfield PB. Effect of pH and pCO2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension. J Pediatr 1988; 113: 474–479. 4. Chang AC, Zucker HA, Hickey PR, Wessel DL. Pulmonary vascular resistance in infants after cardiac surgery: role of carbon dioxide and hydrogen ion. Crit Care Med 1995; 23: 568–574.
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
PRF0010.1177/0267659114540019PerfusionIssitt et al.
Case Report
Tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral vessels
Perfusion 2014, Vol. 29(6) 567–570 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0267659114540019 prf.sagepub.com
RW Issitt,1,2 DA Robertson,1 RM Crook,1 NT Cross,1 M Shaw1 and VT Tsang2,3
Abstract Major aortopulmonary collateral arteries (MAPCAs) provide significant issues during cardiopulmonary bypass, including flooding of the surgical field which requires significant blood volumes to be returned to the extracorporeal circuit via handheld suckers. This has been shown to be the major source of gaseous microemboli and is associated with adverse neurological outcome. Use of pH-stat has been previously shown to decrease the shunt through MAPCAs via an unknown mechanism. Here, we report the associated benefits of pH-stat in decreasing sucker usage and gaseous microemboli in a patient with known MAPCAs presenting for repair of tetralogy of Fallot and pulmonary atresia. Keywords cardiac anatomy/pathologic anatomy; CPB; physiology/pathophysiology; collateral blood flow (lungs); CHD; tetralogy of Fallot; embolism (gaseous)
Case Report Cyanotic congenital cardiac lesions are commonly associated with aortopulmonary collateral vessels, representing a physiological shunt that, during cardiopulmonary bypass (CPB), results in reduced systemic perfusion due to the lower pressure throughout the pulmonary system.1 The result of this is a flooded surgical field in which the surgeon will ask for reduced flow to enable visualisation of the cardiac structures; this exacerbates the reduced systemic flow and lower perfusion pressures. Intervention with vasoconstrictive agents to reverse the lower systemic pressures initiates a downward spiral of increased field flooding and reducing CPB output. Sakamoto et al. introduced a method for calculating systemic pulmonary collateral circulation (SPCC), which involved the measurement of arterial and venous flow; venous flow representing the systemic circulation and the difference between arterial and venous being the percentage of flow passing through the collateral vessels.1 A 7-month-old female presented with tetralogy of Fallot and pulmonary atresia for surgical repair. The patient also had a right-sided aortic arch with aberrant left subclavian artery giving rise to a large tortuous duct, providing pulmonary blood flow, an anomalous right upper pulmonary vein (RUPV) draining into the right atrium and a large left superior vena cava (SVC) draining
into the left atrium. There was also right lung hypoplasia with obliterated pleural space. It was also noted that a large bore major aortopulmonary collateral artery (MAPCA) could be seen on echocardiography (ECHO), although it was difficult to determine the exact origination of the vessel. The operative plan was to perform a full Fallot’s repair to allow the child to grow before repair of the anomalous RUPV (there was concern that the Warden’s procedure would cause obstruction from the right SVC). A median sternotomy was performed and bypass was established in the normal manner. After 1Department
of Clinical Perfusion, Great Ormond Street Hospital, London, UK 2Institute of Cardiovascular Science, University College London, UK 3Department of Cardiothoracic Surgery, Great Ormond Street Hospital, London, UK Corresponding author: Mr Richard Issitt Department of Clinical Perfusion Great Ormond Street Hospital Level 3 Cardiac Theatres Morgan Stanley Clinical Building Great Ormond Street London, WC1N 3JH UK. Email: [email protected]
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
568
Perfusion 29(6)
0.8 0.7
9
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17:57:00
17:56:00
17:55:00
17:54:00
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17:52:00
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Ven Flow
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17:43:00
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17:42:00
Flow (L/min)
6
0.5
pCO2 (kPa)
7
0.6
pCO2
Time
Figure 1. GME, Venous flow and pCO2 data.
A: aortic cross-clamp; B: initiation of pH-stat; C: removal of the cross-clamp. pCO2 values given at α-stat levels.
ligation and division of the patent ductus arteriosus (PDA), the ventricular septal defect (VSD) was closed and a 5mm Gore-Tex® tube was used for the right ventrical-pulmonary artery (RV-PA) conduit through a limited right ventriculotomy. The left SVC was snared at the beginning of the operation and clipped to approximately half its original size following weaning from CPB. Full ligation of the left SVC was not undertaken to prevent venous congestion. On right atriotomy, visualisation of the cardiac structures was limited due to the volume of blood returning from the pulmonary veins, particularly the anomalous
RUPV; the only source of blood flow to which was through collateral vessels. This led to an increased reliance on the handheld suckers, with a noted increase in the number of gaseous microemboli detected from the outlet of the venous reservoir (BCC200, GAMPT mbH, Merseberg, Germany) and a drop in systemic venous return as measured via the venous flow probe (Figure 1). The corresponding SPCC represented 28.3% of the total cardiac output from the CPB circuit. Previous studies have shown that an increased CO2 content limits the collateral blood flow via an unknown mechanism in patients cooled to nasopharyngeal temperatures of
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
569
Issitt et al.
27-28°C1 and so, blood gas management was changed from alpha-stat to pH-stat with a view to reducing the temperature once the pCO2 had reached 5.3kPa (pHstat; 8kPa α-stat). There was an immediate increase in venous return and an associated decrease in suction blood return to a SPCC of 1.3% (95.4% reduction, corresponding to a 40% decrease in suction pump revolutions per minute requirement) as the CO2 content increased, despite remaining at approximately 34°C (range 33.8-35.1°C). The number of microemboli entering the circuit also dramatically dropped, representing the decreased sucker requirement and increased systemic flow. Cerebral near-infrared spectroscopy (NIRS) increased from 61% to 76% with the increase in pCO2. No change was observed with the reduction in pCO2 following cross-clamp release. Following release of the cross-clamp, blood gas management was reverted to alpha-stat management (Figure1). The haematocrit fell slightly during the operation from 32% preoperatively to 28% at the end of CPB. This was increased to 40% following modified ultrafiltration. The total CPB time was 19 minutes and the cross-clamp time 12 minutes. The cardiac index remained above 3 L/min/m2 (0.60.62 L/min) and lactate below 2 mmol/L throughout the procedure, suggesting adequate systemic perfusion was achieved. No neurological sequelae were observed during the hospital stay and the patient continues to do well in the outpatient setting. The CPB circuit consisted of the Baby RX05 oxygenator and hard-shell venous reservoir (Terumo, Tokyo, Japan) with a 3/16x1/4 tubing set. The Stöcket S5™ (Stöckert, Sorin Group GmbH, Munich, Germany) heart-lung machine with pole-mounted roller pumps was used with a 3T™ heater/chiller (Stöckert, Sorin Group). The total base prime volume was 330 mL. This consisted of packed red blood cells (PRBC) of the patient’s blood group, a synthetic colloid (Gelofusine, B. Braun Melsungen AG, Melsungen, Germany), a crystalloid (Plasmalyte A, Baxter, Norfolk, UK) with mannitol 20% w/v (Mannitol, Baxter, Thetford, UK) 2.5 mL/kg and heparin 1000 unit/mL, 1.5 mL (Wockhart, Wrexham, UK). Biochemical compatibility was then attained using sodium bicarbonate as a buffering agent. The patient was systemically cooled to a nasopharyngeal temperature of 34°C and myocardial protection was achieved with 30 mL/kg of cold blood cardioplegia (4:1 blood:cardioplegia to a final concentration of 20 mmol) of St Thomas’s Solution (Harefield Formulation, IVEX Pharmaceuticals, Larne, Northern Ireland). pH-stat blood gas management was achieved by adding CO2 into the gas supply up to a temperature-corrected value of 5.3 kPa. Bicaval cannulation was achieved using 14Fr and 16Fr venous cannulae (DLP, Medtronic Inc, Kerkrade, the Netherlands). A vent was placed into the left atrium. Measurement of the SPCC was undertaken
with a flow probe (Stöckert, Sorin Group GmbH) placed onto the venous line of the CPB circuit, as previously described.1 Cerebral saturation was monitored using NIRS placed on both left and right forehead (Foresight, CAS Medical Systems, Branford, CT, USA).
Comment The presence of MAPCAs in paediatric patients with cyanotic anomalies will vary, depending on the severity of the cyanosis and the age of the patient and is an important risk factor in surgical repair.2 Whilst pH-stat blood management has long been associated with increase cerebral blood flow, previous studies have shown how pH-stat management, in conjunction with deep hypothermia, has also decreased the systemic pulmonary collateral circulation.1 However, the original research by Sakamoto et al. used a roller pump inserted into the venous line as a crude measurement of venous return. There are problems associated with this; it creates a mechanical obstruction to passive venous flow and creates an unintentional possibility of user bias. Our method of measuring venous flow removed both of these factors. There are several possibilities as to the exact mechanisms by which the CO2 phenomenon is achieved. Firstly, the vasodilatation of the cerebral vessels caused by pH-stat may decrease the systemic vascular resistance and, thereby, produce a path of lesser resistance. During pH-stat, NIRS increased (61% to 76%), suggesting cerebral vascular dilatation. However, the heart-lung bypass machine calculates the systemic vascular resistance (SVR) throughout the bypass period with an SVR before initiation of pH-stat of 6711.61 dyne·sec·cm−5 and during pH-stat of 6483.54 dyne·sec·cm−5. Therefore, a change of 228.07 dyne·sec·cm−5 seems unlikely to explain the decrease in SPCC from 28.3% to 1.3% of total cardiac output from the CPB circuit. However, the SVR should not be viewed as an absolute measure because of the influence of the collateral flow vessels and should be regarded as indicative only. The second mechanism may be a direct effect on the pulmonary vasculature of either CO2 or an associated factor (such as decreased pH). Morray and colleagues have previously observed a correlation between the percentage of inspired CO2, mean pulmonary artery pressure and pulmonary vascular resistance index, suggesting a pulmonary vasodilating effect of the CO2mediated alkolosis.3 Further work by Chang et al. confirmed this, but also found the effect occurred in the presence of unaltered PaCO2, suggesting pH rather than CO2 is the contributing factor.4 However, this scenario does not fit with CPB, as pH-stat blood gas management keeps the pH unaltered and allows the pCO2 to rise. Therefore, further research is required to elucidate the exact mechanism that occurs.
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
570
Perfusion 29(6)
In conclusion, in a patient with pulmonary atresia and tetralogy of Fallot, we found that the use of pHstat blood gas management was associated with decreased systemic pulmonary collateral circulation and a dramatic decrease in GME entrained from the handheld suckers. We believe that this is the first report indicating this effect in conjunction with mild hypothermic conditions and presents a refined method of measuring SPCC. Declaration of conflicting interest The authors declare that there is no conflict of interest.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
References 1. Sakamoto T, Kurosawa H, Shin‘oka T, Aoki M, Isomatsu Y. The influence of pH strategy on cerebral and collateral circulation during hypothermic cardiopulmonary bypass in cyanotic patients with heart disease: results of a randomized trial and real-time monitoring. J Thorac Cardiovasc Surg 2004; 127: 12–19. 2. Ichikawa H, Yagihara T, Kishimoto H, et al. Extent of aortopulmonary collateral blood flow as a risk factor for Fontan operations. Ann Thorac Surg 1995; 59: 433–437. 3. Morray JP, Lynn AM, Mansfield PB. Effect of pH and pCO2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension. J Pediatr 1988; 113: 474–479. 4. Chang AC, Zucker HA, Hickey PR, Wessel DL. Pulmonary vascular resistance in infants after cardiac surgery: role of carbon dioxide and hydrogen ion. Crit Care Med 1995; 23: 568–574.
Downloaded from prf.sagepub.com at GEORGE WASHINGTON UNIVERSITY on February 5, 2015
