UBP 2.2 (Short Form): Pediatrics – Scoliosis

Question 1

What is the Cobb angle?

(A 28 kg, 11-year-old male presents for posterior repair of kyphoscoliosis. His mother states that he has Duchenne’s muscular dystrophy (DMD), has been wheelchair bound since he was 9 years old, and has experienced increasing shortness of breath over the past 6 months. Vital Signs: P = 108 b/min; BP = 100/64 mmHg; R = 12)

Answer 1

The Cobb angle is used to measure the severity of scoliosis.
It is a measure of the angle of perpendicular lines drawn from the upper surface of the most cephalad tilted vertebrae and the lower surface of the most caudad tilted vertebrae.

Angles greater than 10 degrees are considered abnormal and

surgery is recommended for angles greater than 40-50 degrees.

Pulmonary dysfunction is associated with angles greater than 60-65 degrees.

Cobb angles around 70 degrees often result in pulmonary hypertension during exercise, while

angles around 110 degrees lead to pulmonary hypertension at rest.

Figure: Measuring the Cobb Angle

Question 2

Are you concerned about his shortness of breath?

(A 28 kg, 11-year-old male presents for posterior repair of kyphoscoliosis. His mother states that he has Duchenne’s muscular dystrophy (DMD), has been wheelchair bound since he was 9 years old, and has experienced increasing shortness of breath over the past 6 months. Vital Signs: P = 108 b/min; BP = 100/64 mmHg; R = 12)

Answer 2

I am concerned, because his progressively increasing shortness of breath potentially represents significant cardiopulmonary dysfunction secondary to neuromuscular scoliosis and/or DMD.

The chest wall deformity associated with significant kyphoscoliosis can lead to –

• impaired pulmonary development (occurs when scoliosis develops before 5 years of age, impairing normal lung development),
• restrictive lung disease with increased work of breathing (decreased chest wall compliance), and
• ventilation/perfusion mismatching.

Subsequent hypoxia, hypoxic pulmonary vasoconstriction, and hypercapnia eventually lead to pulmonary hypertension and right ventricular failure.

Moreover, the abnormal production of dystrophin that occurs with DMD may lead to:

1. cardiomyopathy, ventricular dysrhythmias, and mitral regurgitation secondary to the replacement of myocardium with connective tissue and/or fat;
2. decreased pulmonary reserves, an ineffective cough, retained pulmonary secretions, and recurrent pneumonia secondary to chronic respiratory muscle weakness;
3. chronic aspiration, secondary to impaired laryngeal reflexes;
4. nocturnal oxygen desaturation and sleep apnea, which may contribute to pulmonary hypertension and cor pulmonale.

Question 3

What would be the primary focus of your physical exam?

(A 28 kg, 11-year-old male presents for posterior repair of kyphoscoliosis. His mother states that he has Duchenne’s muscular dystrophy (DMD), has been wheelchair bound since he was 9 years old, and has experienced increasing shortness of breath over the past 6 months. Vital Signs: P = 108 b/min; BP = 100/64 mmHg; R = 12)

Answer 3

I would begin by obtaining a thorough history concerning –

• his exercise tolerance,
• the progression and severity of his shortness of breath,
• any cardiac dysrhythmias (the loss of myocardial tissue associated with DMD can lead to dysrhythmias as well as cardiomyopathy and mitral valve regurgitation), and
• the onset and progression of his DMD and kyphoscoliosis.

I would then identify the location, extent, and severity of his spinal deformity, and focus on a careful assessment of his airway, neurologic function, and cardiopulmonary status.

To further evaluate his cardiopulmonary status I would examine him for dyspnea, wheezing, pulmonary edema, heart murmurs (scoliosis is associated with mitral valve prolapse and DMD can lead to mitral valve regurgitation), jugular venous distension, enlarged liver, and lower extremity edema.

I would also obtain –

• an ECG
  
  • (DMD is associated with tachycardia, tall R waves in V1, prominent Q waves in the limb leads, a shortened PR wave, and inverted T waves),
• pulmonary function tests
  
  • (helps to determine the severity of the patient’s restrictive lung disease and facilitates decisions regarding post-operative ventilatory support),
• an ABG
  
  • (helpful to identify any hypoxemia or acidosis that may be contributing to pulmonary hypertension), and
• a CXR
  
  • (helpful in identifying cardiomegaly or pneumonia).

Finally, for this wheelchair-bound patient, I would order –

• a stress echocardiogram to identify any –
  
  • pulmonary hypertension (right ventricular and/or atrial hypertrophy),
  • cardiomyopathy, or
  • mitral valve prolapse (10-25% of patients with DMD).

Further evaluation would include:

1. a careful airway exam focusing on neck mobility (the presence of cervical scoliosis may compromise airway management), size of the tongue (30% of patients with DMD exhibit macroglossia), and difficulty swallowing (patients with DMD often have diminished airway reflexes and an increased risk for aspiration);
2. a complete blood count; and
3. a neurologic assessment to identify preexisting neurologic deficits (to avoid confusion should neurologic deficits be observed postoperatively).

Question 4

The surgeon says he may wish to perform a “wake-up” test. He has mentioned this to the patient who is now very serious. What would you say to this 11-year-old boy?

(A 28 kg, 11-year-old male presents for posterior repair of kyphoscoliosis. His mother states that he has Duchenne’s muscular dystrophy (DMD), has been wheelchair bound since he was 9 years old, and has experienced increasing shortness of breath over the past 6 months. Vital Signs: P = 108 b/min; BP = 100/64 mmHg; R = 12)

Answer 4

I would tell him that sometime during the case I would whisper his name in his ear and ask him to wiggle his fingers and toes. I would let him know that he would probably not remember anything about waking up, but if he did, he would be very sleepy, would not feel any pain, and would go right back to sleep after wiggling his toes.

Question 5

Would you order any premedication?

(A 28 kg, 11-year-old male presents for posterior repair of kyphoscoliosis. His mother states that he has Duchenne’s muscular dystrophy (DMD), has been wheelchair bound since he was 9 years old, and has experienced increasing shortness of breath over the past 6 months. Vital Signs: P = 108 b/min; BP = 100/64 mmHg; R = 12)

Answer 5

GIven the delayed gastric emptying and diminished laryngeal reflexes associated with DMD, I would administer metoclopramide, an H2-receptor antagonist, and a non-particulate antacid.

Recognizing that this patient will be in the prone position for an extended period of time and that airway management may be challenging (i.e. cervical scoliosis and/or hypertrophy of the tongue secondary to DMD), I would consider an antisialogogue to reduce oral secretions that could inhibit airway management or loosen the tape used to secure the endotracheal tube (it would also be reasonable to avoid this drug due to the potential for worsening tachycardia).

Moreover, if the patient were currently receiving steroids (used to increase muscle mass in DMD), I would provide steroid supplementation.

Finally, I would consider a bronchodilator if PFTs indicated the presence of obstructive airway disease (i.e. infection).

This increasing shortness of breath experienced by this wheelchair-bound patient potentially represents significant cardiopulmonary compromise secondary to DMD and kyphoscoliosis.
Therefore, I would try to avoid any premedications that might contribute to respiratory depression.