Clinical Practice Case 7
Case 7
A 3-month-old girl is brought to the emergency department because of poor feeding and listless behaviour that has worsened over the past hours. She had a several-day history of vomiting and watery diarrhea, but those symptoms had resolved yesterday. Despite improved diarrhea and no vomiting, she is still not taking liquids well.
General Assessment
As you enter the room you note that the infant appears listless. She is breathing rapidly with increased effort as exhibited by mild to moderate retractions. Her colour appears mottled.
7 A
What is your initial impression of the infant's condition based on your general assessment? Are any interventions indicated to treat a life-threatening condition? If so, what are the interventions?
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The general assessment suggests there is poor perfusion, altered mental status, and increased work of breathing. It is not immediately clear if the infant requires bag-mask ventilation.
This infant requires intervention with at least oxygen administration and a rapid primary assessment to determine if the clinical problem is respiratory, circulatory, or both. You will need additional help, so you should activate the emergency response system appropriate for your work environment. You (or colleagues) should place the infant on a cardiac monitor and pulse oximeter and administer high-flow oxygen.
Primary Assessment
After calling for help, you provide high-flow oxygen and attach her to the monitor and pulse oximeter. Her heart rate is 210 /min with a regular rhythm, respiratory rate is 50/min, blood pressure is 55/40 mmHg, and the axillary temperature is 970F (36.1 °C).
On examination, the infant has little response to verbal or painful stimulation. There is increased respiratory effort with mild to moderate retractions. Auscultation reveals reduced distal air entry and scattered inspiratory moist crackles at both lung bases. The cardiac rhythm is rapid and regular without an identifiable murmur, but heart sounds are difficult to hear secondary to her breathing noises and rapid heart rate. Her brachial and femoral pulses are weakly palpable, but the distal pulses are not palpable. The extremities are cool and mottled below the elbows and knees. Capillary refill time in the foot is >6 seconds. The skin is mottled without rash
7B
How would you categorize the infant's condition now?
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This infant has hypotensive shock
7C
What are your decision and actions now?
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This infant requires urgent intervention including administration of high-flow oxygen (if not already started) and rapid establishment of vascular access. If peripheral or central venous access cannot be rapidly obtained, I0 access is appropriate in this infant with hypotensive shock. The cause of the patient's condition is not clear, and you should consider hypovolemic shock because of the history of vomiting and diarrhea.
The severity of the infant's clinical condition, however, is not consistent with the history, which should suggest that something else is causing this child's hypotensive shock state. The 2 common types of shock that can result in this more severe clinical condition are septic and cardiogenic shock. The narrow pulse pressure is more consistent with cardiogenic shock rather than septic shock, especially since there is an increased work of breathing with moist bilateral crackles.
In view of these considerations, the decision is how to begin therapy. To treat the hypotension, a fluid bolus is indicated, but with the possibility of cardiogenic shock, an appropriate approach is to give a rapid bolus of 5 to 10 ml/kg of an isotonic crystalloid with careful assessment during the fluid bolus and reassessment after the bolus.
The advanced provider may determine that it is appropriate to take over the work of breathing through intubation and mechanical ventilation. But this is a high-risk procedure in patients with cardiogenic shock because their blood pressure and cardiac output may be very dependent on the intrinsic stress hormone response. If sedation is given, the patient's blood pressure may fall precipitously, leading to cardiac arrest.
Thus you should anticipate the need for vasoactive drug support and use only the minimal amount of sedation required to permit intubation. If there is time before intubation, you should request preparation of an epinephrine infusion.
Case Progression
After obtaining vascular access and administering a fluid bolus of isotonic crystalloid, you repeat your examination and obtain a focused history:
- Her most recent illness began with vomiting and diarrhea (signs). She was a term newborn and had done well until the present illness.
- She has no allergies, is not on any medications.
- Her Past medical history is otherwise unremarkable.
- The vomiting lasted about 1 day, and then she had 5 to 6 loose bowel movements a day. She was wetting her diaper well until the last 24 hours when her parents noted that she was more fussy and irritable and would not take her bottle well. Her older brother also had gastroenteritis symptoms last week, and he is now recovered (event).
After the fluid bolus, the infant appears to have an increased work of breathing with grunting respirations. Moist crackles remain bilaterally. Auscultation of the heart is unchanged. Her heart rate fluctuates between 200/min and 210/min. Respiratory rate ranges from 50/min to 60/min. Blood pressure is 60/45 mm Hg with no improvement in her pulses. The pulse oximeter is reading intermittently with displayed Sp02 of 92% to 95% on 100% high-flow oxygen. The infant's liver is firm and palpable 3 cm below the costal margin. A bedside glucose test is 80 mg%.
7D
What do you think is happening? Why is there no improvement after the fluid bolus?
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The history of a prior gastroenteritis leading to this clinical illness suggests an acute viral myocarditis in view of the poor response to a fluid bolus. This case illustrates the importance of reassessment and maintaining a willingness to reconsider your initial clinical impression based on the patient's response to interventions. This infant appeared to have gastroenteritis, but the response to fluid suggests that this diagnosis is incorrect. Instead, the likelihood of cardiogenic shock is increased considering the described response.
7E
What are your decisions and actions now?
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This infant requires urgent interventions to improve cardiac output and support adequate oxygenation and ventilation. In children with hypotensive cardiogenic shock, the first priority is to increase the blood pressure to provide adequate perfusion of the heart and help restore adequate perfusion to the brain and other organs. In the short term, an inotropic and vasopressor agent such as epinephrine may be started.
Subsequent therapy is focused on reducing myocardial work, so a vasodilator is often used with or without additional inotropic support.
In addition, treatment of cardiogenic shock includes interventions to reduce metabolic demand by taking over the work of breathing and reducing temperature if the patient is febrile.
7F
What laboratory and radiographic studies (tertiary assessment) would be helpful now?
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As in all children (especially infants) with shock, you should evaluate the serum glucose to determine if the child is hypoglycemic (a bedside glucose test is appropriate).
The advanced provider will use additional objective measures of the adequacy of cardiac output to meet metabolic demand by measuring the degree of metabolic acidosis with evaluation of an arterial or venous blood gas. A venous blood gas from a central venous line also provides objective information on the degree of oxygen extraction by noting the venous oxygen saturation and the difference between the arterial and venous oxygen saturation Normal venous oxygen saturation should be about 70% to 75%.
Evidence for end-organ dysfunction includes evaluation of the BUN and creatinine as well as liver function studies. A chest x-ray will help assess the cardiac size, which will help confirm whether the heart is enlarged or underfilled and will demonstrate if there is x-ray evidence of pulmonary edema consistent with the clinical examination. An ECG will help determine if there is an arrhythmia, and it may show findings (e.g, enlarged cardiac silhouette) consistent with myocarditis or a pericardial effusion. An echocardiogram helps to objectively evaluate cardiac function and heart chamber size.
Case Progression
Following appropriate interventions, a colleague places a femoral venous line. Laboratory studies were sent. The venous blood gas was pH 7.25, PCO2, 39, P02 23, HC03 -13, base deficit - 10.5, oxygen saturation 44%. Venous lactate is 7.5 mmol/L.
The white blood cell count, platelet count, and hemoglobin are all unremarkable. Sodium is 135 mEq/L, potassium 4.4 mEq/L, chloride 97 mEq/L, total C02 12 mEqlL, BUN 23 mg/dL, and creatinine 1.1 mg/dL. A chest x-ray shows bilateral diffuse alveolar infiltrates with an increased cardiac silhouette size. An ECG shows a narrow-complex tachycardia with small QRS complexes across all the limb leads.
7G
How do you interpret the laboratory data?
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The advanced provider will know that the venous blood gas confirms the presence of a significant metabolic acidosis with an increased lactate concentration.
The low venous oxygen saturation also indicates that there is increased oxygen extraction because of low cardiac output and tissue oxygen delivery.
The elevated BUN and creatinine are evidence of renal dysfunction, most likely due to inadequate renal perfusion.
The chest x-ray confirms an enlarged heart size.
The ECG is consistent with myocarditis (small QRS complexes).
Case Conclusion
In view of the laboratory findings, the patient is started on milrinone (a loading dose followed by a continuous infusion). (Note: The approach to vasoactive drug support is complex, and you should seek consultation). Sometimes catecholamine support with agents such as dobutamine may be indicated. But in general, a vasodilator is preferred in this setting if blood pressure is adequate.
An esophageal temperature was 39.9°C whereas the rectal temperature was only 37.5°C. A nasogastric tube is placed, and 50 mL of iced saline is instilled and then removed every 5 minutes to reduce core temperature. To eliminate the work of breathing, you provide mechanical ventilation with sedation. An arterial line is placed for monitoring blood pressure and obtaining blood samples for repeat laboratory studies. The infant's distal pulses are now palpable with a blood pressure of 75/45 mm Hg and heart rate of 175/min. To improve oxygenation, the PEEP is set to 7 cm H20.
Summing Up
This case illustrates the clinical manifestations of cardiogenic shock. Initial presentation in some infants and children may be consistent with hypovolemic or septic shock. The presence of grunting in a child with poor perfusion suggests the presence of pulmonary edema and is most consistent with cardiogenic rather than hypovolemic or septic shock.
The characteristics of cardiogenic shock include marked tachycardia with tachypnea and often an increased work of breathing. The presence of grunting in a child with poor perfusion suggests the presence of pulmonary edema secondary to cardiogenic shock. Note that cardiogenic pulmonary edema results in a clinical picture of lung tissue disease requiring the same approach to intervention as when there is a primary respiratory process. Mechanical ventilation with increased PEEP is often needed following intubation to recruit (reopen) collapsed alveoli and maintain adequate oxygenation and ventilation.
