Myotonic dystrophy: Preop eval
Myotonia = delayed relaxation of skeletal muscle after voluntary contraction

Associated conditions:

Diabetes mellitus
Thyroid dysfunction
Adrenal insufficiency
Cardiac

Atrioventricular conduction delay
Atrial tachydysrhythmias
Diastolic dysfunction
Cardiomyopathy
Mitral valve prolapse
Sudden death secondary to third-degree atrioventricular block or ventricular dysrhythmias.

Pulmonary

Restrictive lung disease
Mild hypoxemia
Diminished ventilatory responses to hypoxia and hypercapnia
Brainstem respiratory control mechanisms may also be defective
Diminished cough effectiveness, may lead to pneumonia
GI

Increased risk of gastric aspiration.
(Pharyngeal muscle weakness + delayed gastric emptying)
[Barash 6e p624]