Pediatric Examination and Board Review (24 page)

8.
(B)
The goal of mechanical ventilation should be gas exchange that is acceptable if not normal, especially when ventilatory support parameters accelerate to the point at which they are toxic themselves. Recent advances in the understanding of ventilatorassociated lung injury in the adult have been applied to children with significant pulmonary disease. In these children, it is important to reduce tidal volumes to 6-8 mL/kg or less, to use PEEP to reduce FIO
₂
to less than 60%, and to employ a long inspiratory time. Although AHRF is a significant cause of morbidity in the ICU, it is rarely the primary cause of mortality. In general, patients who have hypoxic respiratory failure succumb from the other failed organ system(s) that accompany this particular insult.

9.
(A)
When there is consolidation, areas of the lung are perfused but not ventilated. Despite exposure to 100% oxygen, venous admixture will persist in the unventilated lung. Although the patient remains relatively desaturated, the impact of FIO
₂
will not be linear. Therefore, it is imperative to protect the patient from toxic oxygen exposure (>60% FIO
₂
). In the patient with persistent AHRF, high-frequency oscillatory ventilation has been useful for treatment, as have nitric oxide, surfactant, and ECMO. As a substitute for conventional mechanical ventilation, the oscillator has been perhaps the most useful of these strategies. BiPAP, or noninvasive mechanical ventilation, can also be used to supply positive pressure to support patients with less severe disease.

10.
(D)
Heliox is a mixture of helium and oxygen. Helium is less dense than oxygen and when mixed together improves the flow characteristics of gas in patients with airway obstruction. Unfortunately, to achieve the beneficial flow characteristics, the helium must be present at 60% or more, and thus the maximum FIO
₂
is limited to 40%. A higher FIO
₂
is usually desired in AHRF.

11.
(A)
Lipid-laden macrophages discovered in her endotracheal aspirate confirm the suspicion of reflux disease and aspiration.

12.
(B)
This child presents to the clinician as neurologically impaired with respiratory insufficiency. Her initial evaluation should have led one to suspect GERD because hoarseness in a child is not a “normal” finding. The hoarseness could be the result of vocal cord disturbances, either physiologic or anatomic. However, a more common scenario in an impaired 3-year-old who develops persistent hoarseness is undetected GERD.

13.
(A)
Following recovery, this child will require a full evaluation. GERD is particularly common in infants. At 4 months of age, it is present in 50-70% of infants but typically resolves by 1 year of age. A minority of infants go on to develop other symptoms, including dysphagia, arching of the back during feedings, refusal to eat, and failure to thrive. GERD can also be a cause of ALTE, stridor, chronic cough, recurrent pneumonia, reactive airway disease, and hoarseness. In preschool children, GERD presents with intermittent vomiting and symptoms of esophagitis. In older children and adolescents, the cardinal symptom is chronic heartburn or regurgitation. Hoarseness, asthma, chronic cough, and chronic esophagitis may also occur. Significant GERD can be severe enough to waken patients from sleep, may be exacerbated by emotional stress, and usually is postprandial.

In the child with GERD, the assessment and treatment recommendations are summarized as follows:

• For the infant with recurrent vomiting, the history and physical examination are sufficient to make the diagnosis of GERD. Further testing is not necessary, particularly in children in whom growth is uninterrupted. Reassurance and thickening of feeds may be all that is necessary.

• In the neonate and infant with recurrent vomiting and poor weight gain, a comprehensive investigation for other causes of vomiting and failure to thrive is indicated. An upper GI series to rule out anatomic abnormalities that would result in vomiting and an upper GI endoscopy are recommended.

• In the child or adolescent with vomiting and heartburn, an upper GI series or upper tract endoscopy is indicated followed by lifestyle changes: for example, food restrictions, weight loss, smoking cessation. This patient may also require a trial of medication to reduce acid production.

• In children with apnea or ALTE, a pH probe is the diagnostic evaluation test of choice. In fact, at all ages, a pH probe, properly done, is the gold standard of diagnosis.

14.
(A)
Long-term health issues in survivors of acute hypoxic respiratory failure include poor exercise tolerance, difficulty in return to work or school, and persistent symptoms of small airway obstruction or reactive airway disease.

15.
(E)
Untreated GERD can lead to significant chronic obstructive lung disease, bronchiectasis, esophageal dysphasia, and, ultimately, esophageal carcinoma. Treatment of significant GERD begins with medical management: in a 2-4 week trial using H
₂
blockers or proton pump inhibitors (PPIs). Should the medical management trial be unsuccessful or if the child suffers severely from GERD with respiratory insufficiency, surgical intervention may be necessary. The most commonly performed operation is a Nissen fundoplication, which now can be done using a laparoscopic approach with minimal perioperative risk. Restriction of the size of the lower esophageal sphincter can be done endoscopically using radiofrequency ablation (the Stretta system). This procedure is commonly performed in adults and is increasingly performed in children. It is particularly useful in the high–surgical risk child with GERD.

S
UGGESTED
R
EADING

DiMarino M, Rattan S. Pathophysiology of gastroesophageal reflux disease.
Resid Staff Physician.
2003;49(6):12-16..

Herbst JJ, Minton SD, Book LSL. Gastroesophageal reflex causing respiratory distress and apnea in newborn infants.
J Pediatr.
1979;95(5)part 1:763-768.

Hrabovsky EE, Mullett MD. Gastroesophageal reflux and the premature infant.
J Pediatr Surg.
1986;21(7):583-587.

St. Cyr JA, Ferra TB, Thompson TR, et al. Nissen fundoplication for gastroesophageal reflux in infants.
J Cardiovascular Surg.
1986;92(4):661-666.

Vecchia LKD, Grosfeld JL, West KW, et al. Reoperation after Nissen fundoplication in children with gastroesophageal reflux.
Ann Surg.
1997;226(3):315-323.

CASE 12: A 16-YEAR-OLD BOY WITH VERY HIGH BODY TEMPERATURE

A 16-year-old boy is brought to the emergency department by EMS with a temperature of 42°C and seizure activity. He was transferred from a surgery center at 9 am following dental extractions, for which he had received a brief general anesthetic and was in the recovery room when he became febrile and hemodynamically unstable. He has a cardiac rhythm with a pulse but is making little respiratory effort. Before his arrival he was intubated and IV access was established. He was given a dose of lorazepam before transport. The past history is remarkable for depression for which he takes phenelzine, a monoamine oxidase (MAO) inhibitor. Drug use was denied by his parents.

On physical examination the boy is unresponsive. His vital signs are blood pressure: 150/86, pulse: 140, respiratory rate: 22 (hand ventilation), temperature: 42.5°C. Auscultation of the chest reveals normal breath sounds. The rhythm is sinus tachycardia, with peaked T waves. There are no murmurs. The only other part of the physical examination that is abnormal is the neurologic examination. The boy remains unresponsive to pain or voice. His pupils are 4 mm bilaterally, symmetric, and reactive to light. Muscle tone is increased with generalized hyperreflexia and myoclonus.

SELECT THE ONE BEST ANSWER

1.
The intervention least likely to be immediately useful in this setting is

(A) obtaining a complete blood count and differential

(B) obtaining blood and urine samples for toxicology

(C) obtaining an ECG

(D) obtaining a blood gas, serum electrolytes, and a serum CK level

(E) all of the above

2.
The results of the blood gas are as follows: pH: 7.07, PCO
₂
: 74, PO
₂
: 98, base excess (BE): −8. This is best described as a

(A) respiratory acidosis and metabolic alkalosis

(B) metabolic acidosis with respiratory compensation

(C) mixed acidosis

(D) mixed alkalosis

(E) metabolic alkalosis

3.
The diagnosis of malignant hyperthermia is supported by all of the following except

(A) hyperkalemia

(B) CK elevation

(C) acidosis

(D) hypocarbia

(E) temperature elevation

4.
Malignant hyperthermia is treated by

(A) external cooling

(B) mannitol

(C) dantrolene

(D) all of the above

(E) none of the above

5.
Malignant hyperthermia is best characterized as

(A) a genetic disorder of calcium metabolism

(B) an allergic drug reaction

(C) a disorder of temperature regulation

(D) an increase of the hypothalamic temperature set point

(E) an idiopathic disorder

6.
The drug screen is positive for amphetamines. The street drug likely to be responsible for this is