Pediatric Critical Care Medicine Board Review Practice Questions
2004
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QUESTION

183. A 13-year-old male with known sickle cell disease is admitted with one day of fever, cough and tachypnea. He now reports that he has chest pain. A chest x-ray shows a focal infiltrate in the right middle lobe. You are concerned about acute chest syndrome.

Of the following which of the interventions would be LEAST likely to benefit the patient.

A) Partial exchange transfusion
B) Oxygen therapy
C) Aggressive hydration at 2 times maintenance requirements
D) Simple blood transfusion
E) Antibiotic treatment to cover atypical as well as encapsulated organisms

ANSWER

183.     C     Aggressive hydration at 2 times maintenance requirements

Patients with sickle cell disease developing acute chest syndrome will not benefit from over hydration. This can lead to pulmonary edema and worsening respiratory status. However the other interventions will likely benefit the patient

Acute chest syndrome occurs when red blood cells sickle in the pulmonary vasculature. This is often precipitated by pneumonia. Since the child with sickle cell disease is at risk for bacterial infection due to a non functional spleen, aggressive antibiotic coverage is warranted. Encapsulated organisms are especially dangerous for these patients (e.g. S. pneumoniae, N. meningitides, H. influenza, and Salmonella species). Atypical organisms have been implicated as well (primarily Mycoplasma pneumoniae).

Simple blood transfusion is often attempted to increase the patient’s hematocrit and decrease the percentage of sickle cells. This will increase oxygen delivery as well as reduce the risk of continued intravascular sickling of red blood cells. If treatment with simple transfusion is inadequate then partial exchange transfusion is indicated. Oxygen therapy is helpful for these patients as well.

1. Rogers MC, Helfaer MA Eds. Handbook of Pediatric Intensive Care. 3rd ed. Lippincott, Williams & Wilkins, Baltimore, MD. 1999:756-766.

QUESTION

222. All of the following statements concerning malignant hyperthermia (MH) are correct EXCEPT?

A) The most common trigger for malignant hyperthermia is haloperidol
B) The patient may become flaccid and bradycardic
C) An increase in end tidal CO2 or PaCO2 may be the first sign of malignant hyperthermia
D) An increase in myoplasmic calcium ion is the underlying biochemical event responsible for the manifestations of MH
E) Patients who have had a successful anesthetic procedure are not at risk for MH

ANSWER

222.     B     The patient may become flaccid and bradycardic

Malignant hyperthermia (MH) is a clinically heterogeneous disorder in which a pharmacological trigger induces a marked increase in the metabolic rate of genetically abnormal muscle. The increase in metabolic rate produces an acid load that overwhelms the endogenous buffering capacity of the body and the ability of the lungs to excrete CO2. The increased oxygen demand and sympathetic response challenge the cardiovascular system.

The underlying biochemical defect results in a sudden increase in the concentration of calcium ion in the sarcoplasm. Muscle rigor occurs as a result of calcium-induced activation of adenosine triphosphatase. The metabolic rate is increased by calcium-induced activation of glycogen phosphorylase and other enzymes. Patients may develop MH even if they have had a normal anesthetic course in the past.

An episode of MH presents with many nonspecific symptoms. Hypercarbia is the earliest sign. Tachycardia and dysrhythmias also occur. Masseter spasm or inability to open the jaw is an early sign of MH. Temperature elevation occurs later. Potential triggers of MH in humans include potent inhalation anesthetics such as halothane, enflurane, isoflurane, and desflurane. Depolarizing neuromuscular blocking drugs, such as succinylcholine, are also potent triggers of MH. The combination of succinylcholine with a potent inhalational agent are additive in their causation of MH. A large number of drugs such as local anesthetics, droperidol, ketamine, calcium, digitalis, methylxanthines, anticholinergics, anticholinesterases, and sympathomimetic drugs have all been considered potential triggers.

1. Fuhrman BP, Zimmerman JJ, Eds. Pediatric Critical Care, 2nd ed. Mosby, St Louis, MO. 1998: 1380-1389.

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