Year : 2008 | Volume
: 11 | Issue : 2 | Page : 132--134
Role of alpha adrenergic antagonism in a child with a bidirectional Glenn shunt undergoing cleft palate repair
Madan Mohan Maddali1, Valakatte Seetharam Vinayakumar1, Chona Thomas2,
1 Department of Anesthesia, Royal Hospital, Mucat, Oman
2 Department of Plastic and Reconstructive Surgery, Khoula Hospital, Muscat, Oman
Madan Mohan Maddali
Department of Anaesthesia, Royal Hospital, P.B. No.: 1331, PC: 111, Seeb, Muscat
|How to cite this article:|
Maddali MM, Vinayakumar VS, Thomas C. Role of alpha adrenergic antagonism in a child with a bidirectional Glenn shunt undergoing cleft palate repair.Ann Card Anaesth 2008;11:132-134
|How to cite this URL:|
Maddali MM, Vinayakumar VS, Thomas C. Role of alpha adrenergic antagonism in a child with a bidirectional Glenn shunt undergoing cleft palate repair. Ann Card Anaesth [serial online] 2008 [cited 2022 May 21 ];11:132-134
Available from: https://www.annals.in/text.asp?2008/11/2/132/41586
A bidirectional Glenn [BDG] shunt is a type of cavopulmonary shunt that is performed in patients where an anatomical biventricular repair is not possible due to hypoplasia or absence of one of the ventricles. In this palliative cardiac surgical procedure, blood from the superior vena cava [SVC] passes through the lungs and blood from the inferior vena cava [IVC] enters the systemic circulation through an atrial septal defect, bypassing the lungs. This intracardiac shunt results in reduced arterial oxygen saturations [SaO 2 ], which vary between the middle to upper 80s. An elevated SVC pressure [SVCP] is also a consequence of the Glenn circulation.
Cleft palate repair in patients with a BDG shunt might be associated with increased bleeding due to the elevated SVCP, and hypoxemia could be a problem due to the inherent low SaO 2 levels. The anaesthetic management in this situation is discussed.
A cleft palate repair was planned in a 4-year-old girl [weight, 16.5 kg] with tricuspid atresia in whom a BDG shunt had been performed one year ago.
Preoperatively, the child was active, with mild cyanosis and clubbing. The SpO 2 on room air was 86% to 88%. Her preoperative haemoglobin was 13.7 g/dL with normal coagulation, hepatic and renal function. The chest X-ray showed mild cardiomegaly, clear lung fields, equal bilateral pulmonary vascular markings, and normal diaphragmatic contour. The 12-lead ECG demonstrated a normal sinus rhythm, right atrial enlargement, left-axis deviation with the QRS pattern consistent with left ventricular hypertrophy. The P-waves were tall ( >5 mm) and peaked in lead II. The child was on digoxin, ACE inhibitors, diuretics, and aspirin. Aspirin was stopped 1 week prior to the cleft palate repair.
The child received oral midazolam [30 minutes before surgery] and chloral hydrate syrup [2 hours before surgery] as premedication. Under routine American Society of Anesthesiologists [ASA] monitoring, an inhalation induction of general anaesthesia and tracheal intubation was performed with incremental concentrations of sevoflurane in air and oxygen. A peripheral venous access was procured; antibiotic prophylaxis followed; and anaesthesia maintained with IV fentanyl, IV rocuronium, and sevoflurane [end-tidal concentration, 0.5%-1.5%] in air and oxygen.
Haemodynamic monitoring included cannulation of the right dorsalis pedis artery, right internal jugular vein [5 F, paediatric two-lumen central venous catheter with Blue FlexTip® , Arrow International, Inc., Reading, PA], and the left femoral vein [5.5 F multi-lumen central venous catheter, Arrow International, Inc., Reading, PA].
The catheter in the right internal jugular vein was fixed at the 6-cm mark at the skin level using a nomogram [1.7 + (0.07 × height in centimeters] for identifying the distance between the skin puncture site and the SVC-RA [superior vena cava - right atrial] junction.  The distal lumen of the catheter in this child was presumed to reflect pulmonary artery pressure [PAP]; and the proximal lumen, the SVCP. As the child had a large atrial septal defect, the distal lumen of the venous catheter in the femoral vein was presumed to reflect the left atrial pressure [LAP].
Thirty minutes into surgery, there was a rise in SVCP and PAP and a fall in mean arterial pressure [MAP] and SaO 2 [Table 1]. The heart rate slowed down to 80 bpm from a basal rate of 120 bpm, though sinus rhythm was maintained. The surgeon also noticed increased ooze from the operative site. The mean airway pressure and the EtCO 2 trace did not indicate any airway obstruction. There were no signs of increased sympathetic activity to suggest light planes of anaesthesia. Ventricular function was presumed to be normal, as LAP was not elevated. Abnormal head position and compression or kinking of the major vessels in the root of the neck resulting in inadequate venous drainage as possible causes of elevation of SVCP with increased venous ooze were excluded by head elevation and reduced neck extension. CO 2 accumulation as a cause for increased cerebral blood flow resulting in increased SVCP was excluded by arterial blood gas analysis, which revealed normal PaCO 2 levels [pH, 7.368; PaCO 2 , 36.7 mm Hg; PaO 2 , 52.6 mm Hg; and SpO 2 , 88.4%].
Presuming that pulmonary vascular resistance [PVR] was probably elevated, attempts were made to reduce the PVR by hyperventilation and higher inspired oxygen concentrations with additional fentanyl boluses. This did not result in any improvement. At this stage, IV phentolamine mesylate infusion [ROGITINE® , Novartis Pharmaceuticals; dose, 5-20 µg/kg/min] was commenced, initially at the lower dose and then guided by the SVCP and MAP titrated to the higher dose. Once phentolamine was started, the haemodynamics gradually improved [Table 1], the surgical field cleared, and the procedure was completed in 2 hours with minimal blood loss [50 ml]. A total of 400 ml of fluids [200 ml of Ringer lactate and 200 ml of gelofusine (B. Braun Melsungen AG, Melsungen, Germany)] was administered through one of the lumens of the triple-lumen catheter in the femoral vein with meticulous care to avoid air bubbles.
Phentolamine infusion and elective ventilation were continued for 24 hours, and the child made an uneventful recovery. The catheter in the right internal jugular vein was removed following completion of surgery for fear of thrombus formation if left in situ for a prolonged period of time.
Following a BDG shunt, patients with good haemodynamics have age-appropriate blood pressures; with the systemic venous pressure, which reflects pulmonary artery (PA) pressure [measured in the SVC proximal to the SVC-PA anastomosis], ranging from 12 to 15 mm Hg and left atrial or common atrial pressure ranging from 5 to 8 mm Hg. Acutely elevated systemic venous pressures [reflective of PA pressures] in the range of 20 to 25 mm Hg may be tolerated for a short period of time in the postoperative period but would need to be decreased with medical management. The blood flow through the pulmonary artery depends on the transpulmonary gradient [systemic venous pressure - common atrial pressure]. Any factor that would increase PVR or PAP [hypoxia, hypercarbia, acidosis, hyperinflation of lungs, atelectasis, sympathetic stimulation, etc.] would reduce flow through the pulmonary circuit. Reduced pulmonary blood flow results in systemic hypotension, desaturation, and higher central venous pressures.
Management of arterial blood gases is fundamental in the reduction of PVR; and hence, pulmonary blood flow. Hyperventilation with high FiO 2 , and systemic alkalinisation with sodium bicarbonate would produce maximum reductions in PVR.
During artificial ventilation in patients with a cavopulmonary shunt, decreasing the duration of inspiration is usually the best strategy to maximise pulmonary blood flow.  Ventilatory strategies include provision of high tidal volume ventilation and a prolonged expiratory phase with low mean airway pressure. As pulmonary blood flow occurs predominantly during exhalation, an inspiratory-to-expiratory ratio of 1:3 or higher is preferred. Positive end expiratory pressure (PEEP) may be used judiciously to maintain functional residual capacity. Pressure-regulated volume control (PRVC) mode (volume-targeted ventilation with decelerating flow wave pattern) has been found to decrease peak inspiratory pressure,  which may be useful in patients with a BDG shunt. Jet ventilation is an effective alternative mode of ventilation that achieves alkalinisation at lower mean airway pressures and significantly improves cardiac output in these patients.
At the time of the reported incident, the child had a mean arterial pressure of 45 mm Hg [70/35 mm Hg S/D] with a decreased SaO 2 and elevated PAP. After excluding other causes of venous congestion, we presumed that the rise in PAP was related to the changes in PVR.
Pulmonary hypertensive crisis typically occurs in high-risk infants after open-heart surgery. Elevated PAP [>15 mm Hg mean PAP] would have precluded a BDG shunt, in the first place. However, in the dynamic intraoperative period, triggers like anaesthetic or surgical stress, artificial ventilation, secretions could increase the PVR, as in the present case. The improvements in SaO 2 and the haemodynamics following phentolamine administration suggest that pulmonary hypertension could have been a possibility.
When the crisis occurred, the ventilatory parameters were adjusted to reduce the PVR. Despite these attempts, hypotension/desaturation persisted, and an alpha-adrenergic blocker was considered in view of its effect on the PVR.
Had inhaled nitric oxide been available, it would have been the drug of choice in managing patients with elevated PVR perioperatively. IV nitroglycerine, another option, has unpredictable pulmonary vasodilatory effect. From our institutional experience with pulmonary hypertension management in paediatric cardiac surgery, IV phentolamine was found to be a good alternative with a short duration of action. The systemic vasodilation that the drug produces can be easily countered with short-acting peripheral vasoconstrictors. Had this strategy not worked, milrinone would have been the alternative.
The hazard of trauma to the SVC-PA anastomosis site and the danger of a thrombus formation should be kept in mind during cannulation of neck veins in patients with a prior BDG shunt. The duration for which the catheter was left in situ was short, and a central venous catheter with a flexible tip was inserted over a "J" tip polytetrafluoro ethylene (PTFE)-coated spring-guide wire spring-guided wire using the earlier mentioned nomogram for identifying the depth of SVC-RA junction from the skin puncture site. However, there was an element of risk involved in manipulating the catheter across the end-to-side anastomosis.
After a successful BDG procedure, no gradient should exist between the SVC and the PA. Following the BDG shunt and prior to the cleft palate repair, the child was doing well with no signs of SVC obstruction and there was no gradient across the anastomosis as was confirmed by echocardiography. The 2-mm Hg gradient between SVC and PA that was noticed after the right internal jugular vein cannulation could have been due to a technical error in the monitoring system. Errors in monitoring are usually dispelled on direct measurement of intra-chamber pressures. At the time of BDG shunt creation, direct transduction of pressures detected no gradient across the SVC-PA anastomosis. Therefore, the efficacy of the anastomosis was never at question in this child. What was topical was that SVCP increased in step with PAP.
We have described successful management of a child with a bidirectional Glenn shunt who underwent a cleft palate repair where IV phentolamine, an alpha-adrenergic blocking drug, was used to reduce the PVR and SVCP. This reduced venous congestion in the surgical field and allowed successful completion of the surgery with minimal blood loss.
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