Pediatric Primary Care Case Studies (93 page)

Here are the initial laboratory studies and data that are important to help you determine the probability of potential differential diagnoses related to the cause of Emma’s syncopal episode and to assist you in developing a management plan.

Blood studies with normal values indicated in parentheses:

   Na (sodium): 145 (136–146 ) mmol/L; K (potassium): 5 (3.5–5.0) mmol/L; Cl (chloride): 110 (95–108) mmol/L; BUN (blood urea nitrogen): 5 (7–18) mg/dL; HCO
₃
(bicarbonate): 28 (22–30) mmol/L; CR (creatinine): 0.79 (0.8–1.2) mg/dL; glucose: 69 (70–99) mg/dL

   WBC (white blood cell count): 13.3 (4.0–14.0) × 1,000 cells/mm
³
; hemoglobin: 15 (12.0–16.0) g/dL; hematocrit: 42 (36.0–46.0) %; PLT: 223 (150–400) × 10
³
/mm
³

   Opiate screen: Negative

   ETOH (alcohol): Nondetected

   Serum pregnancy: Negative

   UA (urinalysis): Negative

The results of these laboratory studies and your complete physical exam allow you to rule out dehydration, hypoglycemia, anemia, pregnancy, and drug and alcohol use as the etiology of Emma’s syncopal episode.

At this point, what are the differential diagnoses you should consider in this case?

Upon review of your differential diagnosis you note the following:

Neurologic:
Both seizure and cerebral concussion diagnoses are unlikely due to lack of history or physician findings that indicate trauma, headaches, or seizure activity.

Cardiac:
A cardiac problem is an unlikely diagnosis with a normal ECG. You know that syncope that occurs during physical exertion is very concerning for a cardiac etiology, whereas syncope after exertion may occur with vaso-vagal syncope or cardiac conditions (Driscoll et al., 1997).

•   
Cardiac arrhythmias including long QT syndrome:
Unlikely diagnosis due to a physical examination with normal cardiac sounds and normal ECG without prolonged QT or other cardiac arrhythmias or structural abnormalities and no family history of sudden death.

•   
Neurocardiogenic/vasovagal:
This is your most likely diagnosis due to a history of syncope after physical exertion associated with change of posture, dizziness, blurred vision, and short recovery. Finally, there is no evidence by history of seizure activity or a prolonged postictal period associated with loss of bowel or bladder control.

Pregnancy:
This is not supported by history, physician exam, and/or laboratory testing.

Psychogenic:
There is no presyncopal report of hyperventilation or breath holding. There is a remote possibility that an added benign cause of syncope could be due to recent school change, family stressors, and divorce; however, this is not supported by report and family history from Emma, Mrs. Kaplan, or her coach.

•   
Hyperventilation or breath holding:
Not supported by history.

•   
Hysteria (somatization disorder) or a conversion disorder:
Not supported by Emma’s report, coach’s report, and mother’s history.

Medications or illicit drugs including antidepressant drugs or toxins: carbon monoxide poisoning, inhalant/huffing:
Not supported by history and laboratory testing.

Dehydration/volume depletion:
Not supported by physical exam, weight loss, vital signs, and laboratory findings.

What other tests do you need to make your diagnosis and then decide on a plan of care?

Laboratory Blood Work

In the asymptomatic patient, laboratory blood work is rarely helpful; however, specific laboratory tests may be useful.

•   Bedside blood glucose for children who present immediately after the episode

•   Hematocrit for children who are at risk for anemia

•   Urine pregnancy test in postmenarchal females

•   Urine toxicology screen in patients with altered metal status

Electrocardiogram, Echocardiogram, and Imaging Studies

Cost Effectiveness of Testing

In a study of 480 pediatric patients, an abnormal history, physical examination, or electrocardiogram identified 21 of the 22 patients with a cardiac cause of syncope. Electrocardiography provides a screening protocol that allows the identification of a cardiac cause of syncope in the overwhelming majority of pediatric patients. In the absence of ECG changes, the echocardiogram does not contribute to the evaluation of syncope in children (Ritter et al., 2000).

In a retrospective review of 169 pediatric patients with new onset syncope, the results revealed the cost based on testing for fiscal year 1999. A total of 663 tests were performed at a cost of $180,128. Only 26 tests (3.9%) were diagnostic in 24 patients (14.2%). The average cost per patient was $1,055, and the cost per diagnostic result was $6,928. Echocardiograms, chest radiographs, cardiac catheterizations, electrophysiology studies, and serum evaluations were not diagnostic. Thus, the evaluation of pediatric syncope remains expensive and the above testing has a low diagnostic yield. An approach that focuses on the use of testing to verify findings from the history and physical examination or exclude life-threatening causes is justified (Steinberg & Knilans, 2005).

Given your list of possible diagnoses and the information regarding the value of various tests, you decide that you need to order a 12-lead ECG, which reveals a normal sinus rhythm. In Emma’s case, the results for all of the listed studies conducted on her were normal.