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An Interesting Case
The Anesthetic and Cardiopulmonary Bypass Management of an 800g Premature Neonate for the Arterial Switch Operation

PRO vs. CON
Should NIRS Monitoring Be Considered Standard of Care on Every Case Involving CPB?

Literature Reviews
1. Perioperative stroke in infants undergoing open heart operations for congenital heart disease.
2. Brain maturation is delayed in infants with complex congenital heart defects.

The Anesthetic and Cardiopulmonary Bypass Management of an 800g Premature Neonate for the Arterial Switch Operation

By Erin A. Gottlieb MD and Dean B. Andropoulos MD
Division of Pediatric Cardiovascular Anesthesiology
Baylor College of Medicine
Texas Children’s Hospital
Houston, TX

This patient was a female triplet delivered at 28 1/7 weeks of gestation. APGARS were 7 & 8. She was desaturated to the 60s with no increase in saturation with supplemental oxygen. Transthoracic echocardiogram revealed d-transposition of the great arteries with intact ventricular septum (d-TGA/IVS), PFO and PDA. Prostaglandin E₁ was started to maintain ductal patency, and plans were made for surgical intervention.

On the day of surgery, the patient was 20 days old and was transported to the operating by a neonatal transport team. She was intubated with a 2.5 uncuffed oral endotracheal tube. Vascular access included a 1 Fr neo-PICC and a 24g peripheral IV.

After the placement of routine monitors, the patient was induced with fentanyl 10 mcg and pancuronium 0.15mg. A right radial 24g arterial line and a right femoral 2.5 Fr 5 cm central venous line were placed percutaneously. The 2.5 uncuffed endotracheal tube was exchanged for a 3.0 uncuffed tube uneventfully due to leak. The patient’s temperature was maintained at 35-36°C. Infusions were PGE₁ and D₁₀Plasmalyte (2 cc/hr), and blood glucose was monitored closely. The maintenance anesthetic consisted of fentanyl, midazolam and low concentration isoflurane. The Dräger Apollo machine ventilator was used (North American Dräger, Telford , PA ). A oxygen saturation in the low 90s was maintained on an FiO₂ of 0.3, and PaCO₂ was kept in the 40-50s without difficulty. Cerebral saturation (rSO₂) ranged from 50-69 in the prebypass period. Hypotension was treated with calcium chloride 10 mg given twice and phenylephrine 1 mcg given once. Systemic anticoagulation was achieved with heparin 400 units.

The cardiopulmonary bypass prime consisted of 175 cc of reconstituted, washed whole blood (packed RBC and FFP). The goal mean arterial pressure was 30 mmHg, and flows was 150cc/kg or 120-130 cc/min. A 6 Fr Maquet was used for the arterial cannula, and a 14 Fr Polystan was used for the venous cannula. Standard crystalloid cardioplegia and zero balance ultrafiltration were used. The initiation and weaning of cardiopulmonary bypass was controlled by a custom venous occluder. After initiation of cardiopulmonary bypass, the patient was cooled to 22° C over more than 30 minutes. Phentolamine 0.25 mg was given at the beginning of bypass to vasodilate and promote even cooling. The bypass time was 267 minutes, the aortic cross clamp time was 139 minutes, and the period of deep hypothermic circulatory arrest was 5 minutes. The rSO₂ ranged from 62-93 on CPB.

Separation from CPB was uneventful on milrinone 0.375 mcg/kg/min (no loading dose), nitroglycerin 1 mcg/kg/min, CaCl₂ 10 mg/kg/hr, epinephrine 0.03 mcg/kg/hr and inhaled nitric oxide (iNO) at 10 ppm. Protamine 5.2 mg was administered, and 5 cc of platelets were given empirically after protamine. The rSO₂ ranged from 64-71 in the post-bypass period. There was a short period of instability associated with sternal closure with desaturation, ST changes and hypotension which was treated with a CaCl₂ bolus, epinephrine bolus (2 mcg), 5% albumin (5 cc), an increase in iNO to 20 ppm and an increase in ventilation. The sternum remained closed.

The patient was transported to the Cardiovascular Intensive Care Unit (CVICU) on a Giraffe Omnibed (Ohmeda Medical, Laurel, MD). Vasoactive drugs on arrival to CVICU were nitroglycerin 1 mcg/kg/min, CaCl₂ 10 mg/kg/hr, epinephrine 0.07 mcg/kg/min and iNO at 20 ppm. Total fentanyl dose was 175 mcg (206 mcg/kg), and total midazolam dose was 0.7 mg (0.8 mg/kg).

The patient recovered in the CVICU for a number of days and was subsequently transferred to the NICU until she was ready for discharge home. At her last clinic visit, she was doing well with no evidence of neurological injury.

The careful preparation that went into this case was critical to its successful completion. A multidisciplinary team with members from Neonatology, Cardiovascular Anesthesiology, Cardiovascular Surgery, Cardiovascular Intensive Care, Nursing and Perfusion made a plan for the preoperative, operative and postoperative care of this patient. In the operating room, the patient was attended to by two attending surgeons, two attending anesthesiologists, two perfusionists, two scrub nurses and two circulating nurses. Preoperatively, the patient was cared for in the NICU with cardiology input. Postoperatively, the patient was cared for in the CVICU by both NICU and CVICU attending physicians and nurses, practitioners familiar with both very low birth weight, premature and postoperative cardiac surgery patients.

Lung immaturity was carefully considered. Oxygen saturation in the 80s with a PaCO₂ in the 40s was considered adequate. The patient was ventilated with the Dräger Apollo machine ventilator in pressure control mode with careful monitoring of exhaled tidal volumes to detect changes in compliance. Surfactant was available, though not used, for administration prior to separation from cardiopulmonary bypass.

In order to decrease the risk of retinopathy of prematurity, the patient’s eyes were kept covered as much as possible, and exposure to bright light was avoided. The lowest FiO₂ possible was used to maintain the SpO₂ in the 80s pre-bypass and 88-93 post-bypass. In addition, wide fluctuations in PaO2 were avoided.¹

The immaturity of the brain was also an important consideration. It is known that cerebral autoregulation is not preserved during hypothermic CPB and that flow is pressure passive at moderate and profound hypothermia in infants.² In addition, there are concerns about the possibility of anesthesia-induced neuronal cell loss in the developing brain.^3-5

The timing of operation for d-TGA/IVS is controversial. The arguments for early operation include minimizing deconditioning of the left ventricle, minimizing infection and hospital acquired illness and avoiding prolonged PGE₁ infusion. The arguments for postponing surgery include the possibility of stabilizing comorbidities such as NEC or IVH, allowing the patient to grow and allowing further brain maturity which may decrease the risk of white matter injury. However, the risk factors for morbidity and mortality from the arterial switch operation are age > 30 days, gestational age and birth weight.^6-9

References

¹ Spaeth JP, O’Hara IB, and Kurth CD. Anesthesia for the Micropremie. Semin Perinat 1998;22:390-401.

²Ramamoorthy C and Andropoulos DB.  Neurological monitoring and Outcome. In: Andropouls DB, Stayer SA and Russell IA, editors.  Anesthesia for Congenital Heart Disease, 2nd ed.  Oxford, UK: Wiley-Blackwell; 2010, in press.

³Loepke AW. Developmental neurotoxicity of sedatives and anesthetics: A concern for neonatal and pediatric critical care medicine. Pediatr Crit Care Med 2009;11:000-000.

⁴Jevtovic-Todorovic V and Olney JW. PRO: Anesthesia-Induced Developmental Neuroapoptosis: Status of the Evidence. Anesth Analg 2008;106:1659-1663.

⁵Loepke AW, McGowan Jr FX and Soriano SG. CON: The Toxic Effects of Anesthetics in the Developing Brain: The Clinical Perspective. Anesth Analg 2008;106:1664-1669.

⁶Qamar ZA, Goldberg CS, Devaney EJ, et al. Current Risk Factors and Outcomes for the Arterial Switch Operation. Ann Thorac Surg 2007;84:871-9.

⁷Duncan BW, Poirier NC, Mee RBB, et al. Selective Timing for the Arterial Switch Operation. Ann Thorac Surg 2004;77:1691-7.

⁸Roussin R, Belli E, Bruniaux J, et al. Surgery for Transposition of the Great Arteries in Neonates Weighing Less than 2,000 Grams: A Consecutive Series of 25 Patients. Ann Thorac Surg 2007;83:173-8.

⁹Dibardino DJ, Allison AE, Vaughn WK, et al. Current Expectations for Newborns Undergoing the Arterial Switch Operation. Ann Surg 2004;239:588-598.

© 2010 CONGENITAL CARDIAC ANESTHESIA SOCIETY