Year : 2009 | Volume
: 12 | Issue : 2 | Page : 146--148
Decompression of superior vena cava during bidirectional Glenn shunt
Venugopal Kulkarni, Ravikiran Mudunuri, Krishnaprasad Mulavisala, R Jagannath Byalal
Department of Cardiac Anaesthesia, Axon Anaesthesia Associates, Care Hospital, Hyderabad, India
Axon Associates, Care Hospitals, Road No. 1, Banjara Hills, Hyderabad - 500 034
Patients undergoing bi-directional Glenn shunt for various congenital anomalies of the heart will have their superior vena cava (SVC) clamped during the procedure. The duration of the procedure is variable, ranging from five to 30 minutes. This can affect the cerebral perfusion due to raised venous pressure [Cerebral blood flow = Mean arterial pressure − (Intracranial pressure + Central venous pressure)]. Shunting away the SVC blood is a well known technique to counter this problem, but we describe two cases where a novel technique was successfully used to decompress the SVC.
|How to cite this article:|
Kulkarni V, Mudunuri R, Mulavisala K, Byalal R J. Decompression of superior vena cava during bidirectional Glenn shunt.Ann Card Anaesth 2009;12:146-148
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Kulkarni V, Mudunuri R, Mulavisala K, Byalal R J. Decompression of superior vena cava during bidirectional Glenn shunt. Ann Card Anaesth [serial online] 2009 [cited 2021 Nov 29 ];12:146-148
Available from: https://www.annals.in/text.asp?2009/12/2/146/53447
Bi-directional Glenn Shunt is a commonly performed procedure in the treatment of various cyanotic congenital heart diseases which eventually lead to single or one-and-a-half ventricle repair. It can be performed with or without cardio-pulmonary bypass as far as the pulmonary perfusion is maintained. , During the procedure, the superior vena cava (SVC) is clamped and the proximal pressures can rise as high as 40 to 55 mmHg. This impairs blood flow to the brain (Cerebral perfusion pressure = Mean arterial pressure - Central venous pressure). About 50 to 60% of the cardiac output returns via the SVC during infancy. This exaggerates the rise in the pressure following application of the clamp. The strategies to protect the brain are:
Establishing bypass, cooling and low flows when on bypass.Veno-venous , /veno-atrial shunts to drain the SVC when performed without bypass.Minimizing the duration of the clamp.Draining SVC, improving the cerebral perfusion, is one of the best ways of cerebral protection. We report cases of draining the right internal jugular vein via the central venous catheter to reduce SVC pressure.
A three-year-old child, of Indian origin, with pulmonary stenosis, VSD, PFO and hypoplastic right ventricle was posted for bi-directional Glenn shunt, enlargement of the PFO and ligation of main pulmonary artery with a prospective uni-ventricular physiology. Pre-operatively, pulse oximetry revealed room air saturations between 70 to 75%. There was no history of bleeding/clotting problems in the family and the neurological assessment was normal. The hemoglobin concentration was 16 g/dl and platelet count was 1.4 x 10 6 /Ál.. Liver and renal function tests were within normal limits.
Anesthesia was induced with sevoflurane, and the trachea was intubated with 5.0 mm ID uncuffed tube following administration of vecuronium and fentanyl. Left femoral artery was catheterized for invasive pressure monitoring. Right femoral vein and right internal jugular veins were cannulated with triple lumen (5.5 F, 8 cm) and single lumen (20G) catheters respectively to measure inferior and superior venacaval pressures independently. After peri- cardiotomy, adequate heparinization (3mg/kg) and ACT of greater than 480, cardio-pulmonary bypass was established. Pressure in the RIJV was between 7 to 9 mmHg. We connected the 20 G cannula in the RIJV to the venous reservoir, with two three-way stopcocks and an extension line, were able to simultaneously monitor the SVC pressure. The SVC was clamped and divided to establish an anastomosis with right pulmonary artery. The SVC pressure measured reached 45mmHg. The SVC was decompressed by opening the three-way stopcock into the venous reservoir and this blood was re- circulated following oxygenation. With the help of another three- way stopcock and 10 ml Luerlock syringe, blood was actively aspirated from the RIJV and pushed into the venous reservoir. The SVC pressures dropped and were maintained between 15 and 18 mmHg.
A two-year-old child weighing 7 kg, with tricuspid atresia, severe right ventricular tract outflow tract obstruction and an atrial septal defect was posted for off pump bi-directional Glenn shunt. The main, right and left pulmonary arteries measured 7 mm, 8 mm and 6 mm respectively. The pre-operative hemoglobin was 17 g/dl, platelets 99,000/ Ál and the oxygen saturations were 68 to 75%.
Anesthesia was induced with sevoflurane, and the trachea was intubated with 5.0 mm ID uncuffed tube following administration of pancuronium and fentanyl. Left femoral artery was catheterized for invasive pressure monitoring. Right femoral vein and right internal jugular veins were canulated with triple lumen (5.5 F, 8 cm) and single lumen catheters (20 G) respectively to measure inferior and superior venacaval pressure independently. The pressure in the RIJV and the femoral vein measured between 10 to 12 mmHg. With the help of two three-way stopcocks near the transducer, we were able display either the SVC or inferior venacaval pressure on the monitor. A 10 ml Luer lock was connected to the other three-way with sterile precautions and care to avoid air. After heparinization (1mg/kg), SVC was clamped and divided to establish an anastomosis with right pulmonary artery. The SVC pressures measured reached 38 mmHg. During this period, blood from the right internal jugular vein was aspirated and injected into the femoral vein. This manoeuvre reduced and maintained the RIJV pressures between 10 and 15 mmHg. We believe this measure during SVC clamp maintains the cerebral perfusion and also minimizes the risk of cerebral edema.
Both the patients recovered well in the intensive care unit without any neurological issues.
The SVC is clamped while performing a bi-directional Glenn shunt. This can hamper cerebral perfusion. The duration of clamp application can vary from as low as five but may be required for up to 30 minutes. The procedure is usually performed at the age of three to six months (weighing between three and six kg) when their cardiac output will be ranging from 0.3 to 0.6 lmin.  The SVC in this age group carries nearly 50% of the cardiac output.  The drainage per minute, by whatever means, should be equal to this flow to minimize the rise in SVC pressures and maintain adequate cerebral perfusion pressure.
Flow depends on the viscosity and density of the fluid, the width and the length of the tubing and the difference in the height between the RIJV and the venous reservoir. With a small cannula in the RIJV, increased viscosity of blood in patients with cyanotic heart diseases makes it very difficult for gravity alone to achieve these flows. So, one has to actively aspirate and push the blood into the venous reservoir. With a 10ml syringe, we had to aspirate at least 35 times per minute in this particular case to achieve complete drainage of the SVC. We were able to achieve about 20 times per minute. Though 20 G cannula would be sufficient to decompress the SVC at three to six months of age, a bigger, short cannula (18 G) in the RIJV is of greater help in bigger children.
Post-operative recovery of the children was good and the neurological assessment was normal. Decompression of the SVC can be done irrespective of whether the Glenn shunt is done on or off cardiopulmonary bypass. When on pump the SVC blood is drained in to the venous reservoir and when off into the inferior vena cava. Aseptic precautions must be ensured. Air should be strictly avoided especially when the procedure is done off pump. This technique can only add to the cerebral protection by reducing the SVC pressures and improving the cerebral perfusion.
Veno-atrial or veno-pulmonary shunts no doubt are the best means to decompress the superior vena cava while it is clamped for anastamosis. But the disadvantages include shunt dysfunction, possibility of using roller pump to effectively drain, distortion of anatomy of pulmonary artery making them less suitable for future Fontan procedure and supra-ventricular arrhythmias while establishing the shunt. These risks can be avoided with the method we have reported. However, adequate sterile precautions have to be exercised during these maneuvers and inadvertent injection of air should be avoided by meticulous de-airing. Possiblity of infection and air embolism should be borne in mind.
Mr. Naveen Kumar, Chief Perfusionist, Care Hospitals, Banjara Hills.
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