Introduction: NS is a relatively common (1 in 1000-2500 live births) autosomal-dominant mutation in the Ras/mitogen-activated protein kinase (MAPK) signal transduction pathway associated with characteristic cardiac, facial, musculoskeletal, and hematologic anomalies.
Case description: A 41 year-old male with NS was admitted for decompensated diastolic heart failure. Past medical & surgical history was notable for chronic atrial fibrillation, severe pulmonary hypertension, severe COPD (FEV1<35%), mechanical aortic valve replacement at age 6 and re-do at age 16, and cervical C1-4 spinal fusion. TEE performed on admission was notable for severe MR, severe pulmonary HTN (PAP 64), but preserved LVEF of 65%. After being medically optimized, the patient was taken for MV replacement surgery.
Given classic features of NS (small face, micrognatia, limited mouth opening, protuberant upper teeth, short neck) and limited head extension from prior cervical fusion, awake fiberoptic intubation was performed after lidocaine topicalization of the oropharynx and premedication with IV midazolam). After induction of anesthesia, the right internal jugular vein was cannulated for central venous access. Bypass catheters were placed in the femoral vessels by CT surgery prior to sternotomy in the event that CPB became emergent. Sternotomy was then performed and followed by extensive lysis of adhesions. On-pump mitral valve replacement was uneventful. There was no abnormal bleeding. Patient was taken to ICU intubated.
The patients’ postop course was complicated by severe hypoxic respiratory failure and prolonged mechanical ventilation, severe thrombocytopenia, acute renal failure requiring CVVH, and acute pancreatitis. Despite these complications, the patient was discharged on post-op day 15.
Discussion:
Characteristic features of NS and their anesthetic implications include:
- Musculoskeletal: short statue, kyphoscoliosis- difficulty administering neuroaxial anesthesia.
- Craniofacial abnormalities: short webbed neck (pterygium colli), micrognathia, limited mouth opening, teeth misalignment – difficult intubation.
- Pulmonary abnormalities: chest deformity (pectus excavatum of pectus carinatum), along with kyphoscoliosis – lung disease.
- Congenital heart disease: commonly subvalvular pulmonary stenosis and hypertrophic cardiomyopathy, less frequently ASD, VSD, aortic coarctation - hemodynamic instability
- Bleeding disorders – factors XI, XII or VIII deficiency, thrombocytopenia- increased blood loss
- CNS: epilepsy, intellectual disability- make it challenging to provide care to these patients, who often require general anesthesia for simple diagnostic and therapeutic procedures.
- Skin and connective tissue: lymphedema of hands and feet, hyperkeratosis –difficult IV access.
- Although cases of MH (malignant hyperthermia) have been described in NS patients, NS is not associated with MH, therefore MH precautions are not necessary.
Conclusion: Anesthesiologists should be familiar with Noonan syndrome as relatively common congenital disease, which can pose challenges with airway management, excessive bleeding and implications of congenital or acquired heart disease.
