F97 Arch Dis Child Fetal Neonatal Ed: first published as 10.1136/adc.2004.064337 on 21 February 2005. Downloaded from RECENT ADVANCES The intensive care of infants with hypoplastic left heart syndrome U Theilen, L Shekerdemian ............................................................................................................................... Arch Dis Child Fetal Neonatal Ed 2005;90:F97–F102. doi: 10.1136/adc.2004.051276 Until a little over two decades ago, hypoplastic left heart excessive pulmonary blood flow, an important subgroup may have inadequate inter-atrial mix- syndrome was considered an inoperable and fatal ing due to a restrictive atrial septal defect (ASD). condition, with most deaths occurring in early infancy, and This results in global hypoperfusion, with pro- almost all of those affected dying before their first birthday. found hypoxaemia and acidosis, severe pulmon- ary venous hypertension, and overwhelming However, the advent of surgical palliation and advances in pulmonary venous congestion on chest x ray. peri-operative care, have offered hope to these patients These infants are generally unresponsive to and their families. measures aimed at improving pulmonary flow such as aggressive mechanical ventilation with ........................................................................... high inspired oxygen fractions or nitric oxide, and if left untreated they rapidly develop ypoplastic left heart syndrome (HLHS) is a progressive pulmonary venous hypertension. continuum which can affect all left sided This is associated with increased mortality in Hcardiac structures, from the mitral valve to infants with HLHS.34 the aortic arch. Since Norwood’s first description A restrictive ASD requires urgent intervention. of surgical palliation in 1981,1 HLHS has been If this has been diagnosed antenatally, delivery managed either by staged palliation in the should be planned in a centre able to urgently majority of cases, or, in a minority, by primary institute cardiopulmonary bypass. Decompres- cardiac transplantation. In this article we will sion can be achieved by open surgical septec- discuss the early medical and surgical manage- tomy, or by the transcatheter route. In a recent copyright. ment of the neonate with HLHS, focusing on the series of 355 neonates with HLHS, 21 required evolution of new surgical strategies, and on the interventional cardiac catheterisation for crea- changing emphasis of peri-operative circulatory tion or enlargement of restrictive or absent ASD.5 management on the intensive care unit. A number of transcatheter techniques have been used. The Rashkind balloon atrial septostomy INTENSIVE CARE OF THE INFANT WITH (often unsuccessful) and blade septectomy (car- HLHS rying a high risk of tamponade) have been more The primary goal of peri-operative care of the recently superseded by techniques using trans- neonate undergoing stage 1 palliation (Norwood atrial needle puncture followed either by serial operation or its modifications) is to optimise balloon dilatation (septoplasty) or stent implan- systemic oxygen delivery and organ perfusion. tation (see fig 1). This must be addressed as early as possible, and Following relief of inter-atrial restriction, a few in most cases the critical period begins before days should be allowed before stage 1 palliation. http://fn.bmj.com/ transfer to a cardiac centre.2 This allows for resolution of organ damage secondary to severe hypoxia, and for improve- 5 PREOPERATIVE STABILISATION ment in lung function. The arterial duct In the preoperative period, systemic perfusion is Respiratory management critically dependent on a patent arterial duct, a All neonates with HLHS should have continuous non-restrictive inter-atrial communication, and monitoring of their oxygen saturation. In the on September 29, 2021 by guest. Protected good right ventricular function. The arterial duct preoperative setting, the systemic, pulmonary, is the main source of systemic blood flow, and and coronary circulations run in parallel, and are provides retrograde filling to the aortic arch, all supplied by the right ventricle.6 The balance See end of article for diminutive ascending aorta, and coronary between pulmonary flow (Qp) and systemic flow authors’ affiliations arteries. Babies with HLHS require prostaglandin (Qs) is critically important: an excess of one will ....................... E to maintain ductal patency. This should be by definition compromise the other. The balance Correspondence to: commenced in the delivery room if the diagnosis between pulmonary and systemic flow depends Dr L Shekerdemian, has been made prenatally, or otherwise as soon on the relative resistances in the two circulations. Intensive Care Unit, Royal 2 Deliberate or inadvertent manipulation of the Children’s Hospital, as the diagnosis is suspected. Early intervention Flemington Road, with prostaglandin maximises systemic perfu- pulmonary resistance (primarily with changes in Parkville, Victoria 3052, sion, and optimises the condition of the infant respiratory management), or of the systemic Australia; before surgery. resistance (using pharmacotherapy), will result lara.shekerdemian@ rch.org.au The inter-atrial communication Abbreviations: ASD, atrial septal defect; ECLS, Accepted 7 June 2004 In contrast to the majority of HLHS patients, in extracorporeal life support; HLHS, hypoplastic left heart ....................... whom low systemic perfusion is in the context of syndrome; PVR, pulmonary vascular resistance www.archdischild.com F98 Theilen, Shekerdemian Arch Dis Child Fetal Neonatal Ed: first published as 10.1136/adc.2004.064337 on 21 February 2005. Downloaded from Box 1: Guide to immediate respiratory management of infants prior to surgery for HLHS Indications for intubation N Apnoeas or severe respiratory distress N Significant metabolic acidosis* N Significant pulmonary overcirculation* N Severe myocardial dysfunctionÀ *Markers of systemic hypoperfusion with a high risk of end- organ dysfunction; persistent tachypnoea ÀPerinatal asphyxia and metabolic acidosis in the ‘‘col- lapsed’’ neonate; coronary hypoperfusion in the infant with excessive pulmonary flow Ventilation` and target blood gases N PaCO2 35–45 mm Hg N pH 7.35–7.40 N PaO2 30–45 mm Hg N SaO2 70–85% Figure 1 Transthoracic echocardiogram of infant with HLHS, showing a stent across the inter-atrial septum, allowing free mixing of blood `Ventilate initially using FiO2 0.21, PEEP 4–5 cm H2O between the left atrium (LA) and right atrium (RA). Haemoglobin should be maintained at 140–160 g/l in changes in this balance in favour of one or other circuit. The most common early sign of pulmonary overcirculation is 10 anaesthetised infants with unoperated HLHS were an increase in arterial oxygen saturation, and seemingly evaluated in a prospective, randomised, crossover trial.14 minor increases in saturation can result in significant Both manoeuvres similarly decreased Qp:Qs and arterial increases of pulmonary flow.7 If left untreated, the later, oxygen saturations. Hypercarbia, but not hypoxia, increased more sinister manifestations of systemic hypoperfusion may systolic and diastolic blood pressure, and also increased the copyright. result; these are metabolic acidosis, diastolic hypotension, mixed venous and cerebral oxygen saturations, suggesting coronary ischaemia, and myocardial and end-organ dysfunc- improved systemic oxygen delivery. tion. The sequelae of this—mesenteric ischaemia leading to severe necrotising enterocolitis,8 and hypoxic-ischaemic or Pharmacotherapy haemorrhagic cerebral damage—can ultimately preclude Intravenous vasodilators are frequently used to optimise surgical intervention. systemic blood flow, and two main classes of agent are used Initial respiratory care of the neonate with known or in the preoperative setting. Sodium nitroprusside is a suspected HLHS should be targeted at avoiding pulmonary vasodilator with a rapid onset of action, and has the potential overcirculation. This pre-emptive approach is by far prefer- advantages of a relatively titratable dose dependent effect, able to treatment of unwanted sequelae. Pulmonary blood and a short half life.15 Phenoxybenzamine, an a-adrenergic flow in the neonate is exquisitely sensitive to alveolar oxygen, receptor blocker, was shown to reduce Qp:Qs in a prospective carbon dioxide, and pH. Immediate management should study of 15 patients with HLHS.16 Higher superior vena cava therefore include the routine avoidance of factors which saturation and a narrower arteriovenous oxygen difference http://fn.bmj.com/ increase pulmonary flow (such as excessive oxygen admin- were noted, indicating improved systemic oxygen delivery istration or respiratory alkalosis), or with early intervention with phenoxybenzamine. In another study, the use of peri- using strategies which modestly increase pulmonary vascular operative phenoxybenzamine was associated with increased resistance (PVR), and the careful introduction of systemic survival.17 Systemic vasodilators should be used carefully in vasodilators. The basic goals of respiratory management of order to avoid excessive hypotension, which can to an extent infants with HLHS are described in box 1. Mechanical be avoided if the intravascular volume status is adequate. ventilation is not mandatory in stable infants; indeed, in a However, systemic blood pressure is a poor marker of on September 29, 2021 by guest. Protected series of 171 babies with HLHS, 30% did not require systemic blood flow. A lower mean arterial pressure