Accepted Article
DR SHANNON MORRISON (Orcid ID : 0000-0002-7408-2710)
Article type
: Letter
Handling Section Editor: Dr Chandra Ramamoorthy
Anaesthetic management of uncorrected Tetralogy of Fallot and mitochondrial disorder: a role for Dexmedetomidine
Authors: 1. 2. 3. 4.
Shannon Morrison1 Michael Ranger1 Benjamin Anderson2 Scott Fox2
Affiliations: 1. Queensland Children’s Hospital Department of Anaesthesia Brisbane, Australia 2. Queensland Children’s Hospital Department of Cardiology Brisbane, Australia
Corresponding author: Dr S Morrison Queensland Children’s Hospital 501 Stanley Street South Brisbane, QLD 4101 Email:
[email protected] MeSH keywords: Dexmedetomidine, Tetralogy of Fallot, Mitochondrial Diseases, Cardiac Catheterization
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/pan.13570 This article is protected by copyright. All rights reserved.
Accepted Article
Introduction
The case presented is a patient with uncorrected cyanotic congenital heart disease (CHD) and a mitochondrial disorder, and highlights the need for understanding of the physiological sequelae and impact of anaesthesia for these disorders.
Case
A 9-year-old boy with uncorrected Tetralogy of Fallot (TOF) and mitochondrial disorder presented for palliative right ventricular outflow tract (RVOT) stent insertion. Given the severity of his developmental delay and guarded prognosis, definitive surgical management was not undertaken earlier in life. The patient presented with sequelae of cyanotic heart disease including hypoxia (saturations 70% on room air), polycythaemia (Hb 242g/L) and hypercyanotic spells despite beta-blocker therapy. There was significantly limited flow through the RVOT and a reliable echocardiographic gradient could not be obtained.
Intranasal dexmedetomidine 2mcg/kg was used as premedication with favourable anxiolytic effect. An inhalational induction was performed using a combination of oxygen, sevoflurane and nitrous oxide. Intravenous access was established, a bolus dose of fentanyl 1.5mcg/kg administered, and the patient was intubated with a cuffed endotracheal tube without muscle relaxant. A radial arterial line was sited. Anaesthesia was maintained on a combination of dexmedetomidine infusion 0.2 – 0.7mcg/kg/hr, remifentanil infusion 0.05 – 0.07mcg/kg/min and 0.3 MAC sevoflurane. The patient was ventilated on 100% oxygen with pressure-control ventilation, targeting an end-tidal CO2 of 35 – 40mmHg and arterial saturations of 85%. Blood pressure remained stable within an age appropriate range with a phenylephrine infusion of 50mcg/hr, and heart rate remained stable at 50 – 60bpm. The patient received a total of 20mL/kg of 0.9% sodium chloride intraoperatively.
RVOT stenting was performed with telescoped Omnilink stents, with evidence of increased pulmonary blood flow (increased blood pressure, end-tidal CO2 and oxygenation). Saturations improved to 96%, and the inspired oxygen concentration was weaned. The patient was successfully extubated, whilst maintaining a low dose dexmedetomidine infusion and subsequently transferred uneventfully to the paediatric intensive care unit (PICU). The saturations settled at 88% on room air, and the patient was discharged from PICU the following day. The patient had significant improvement in growth and quality of life at three-month follow-up.
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Accepted Article
Discussion
TOF is the most common cause of cyanotic CHD. Features include the anatomical quartet of an outlet ventricular septal defect, RVOT obstruction, right ventricular hypertrophy and an overriding aorta (1). Uncorrected TOF has a mortality rate of 70% by the age of ten years, however survival into adulthood is possible (1).
Mitochondrial disorders are a heterogenous group, and patients often have perioperative issues including epilepsy and altered metabolic function (2). Propofol has been shown to have mitochondrial depressant effects, particular inhibition of the OXPHOS complex I, transport of long-chain fatty acids and beta-oxidation; and is not recommended for use in patients with mitochondrial disorders (2). Dexmedetomidine provides a safe alternative, and additionally has been shown to result in achievement of early extubation following cardiac procedures more frequently than propofol-based sedation (3).
TOF and mitochondrial disorders both present risks to anaesthesia, with control of physiologic stress, maintenance of stable haemodynamics and essential respiratory function. Dexmedetomidine is a centrally acting alpha-2-adrenergic agonist, and provides sedation, anxiolysis, decreases perioperative opioid requirements, lowers the MAC for volatile anaesthetic agents and reduces the incidence of emergence delirium (3), thereby making it an ideal agent for use in this case.
Intranasal dexmedetomidine has been shown to be more efficacious than oral midazolam in producing sedation, anxiolysis, acceptance of facemask and inhalational induction, and provides less cardiovascular variability (4). There is an increasing body of evidence supporting the use of dexmedetomidineas a co-anaesthetic agent in cardiac catheterisation procedures, as a result of the beneficial haemodynamic profile and the opioid and MAC-sparing effects (3, 4).
Emergence delirium is relatively common following paediatric procedures. Intraoperative dexmedetomidine has been shown to have a prophylactic effect in preventing emergence agitation in children receiving volatile anaesthesia without any associated increase in time to extubation or discharge (4).
Disclosures: ETHICS: Nil required FUNDING: Funded by departmental resources DISCLOSURES: Nil
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References
Accepted Article
1. Lovell AT. Anaesthetic implications of grown-up congenital heart disease. British journal of anaesthesia. 2004;93(1):129-39. 2. Driessen JJ. Neuromuscular and mitochondrial disorders: what is relevant to the anaesthesiologist? Current opinion in anaesthesiology. 2008;21(3):350-5. 3. Easley RB, Tobias JD. Pro: dexmedetomidine should be used for infants and children undergoing cardiac surgery. J Cardiothorac Vasc Anesth. 2008;22(1):147-51. 4. Mahmoud M, Mason KP. Dexmedetomidine: review, update, and future considerations of paediatric perioperative and periprocedural applications and limitations. British journal of anaesthesia. 2015;115(2):171-82.
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