Clinical Practice Case 5

This infant has a worrisome clinical picture with tachypnea and decreased response to her parents and her environment. Based on the history of vomiting and diarrhea, she likely had a viral gastroenteritis and now has hypovolemia secondary to fluid loss. The infant's appearance with decreased responsiveness suggests that this infant is in shock.

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Based on your general assessment, it is appropriate to provide oxygen and call for help to obtain vascular access and get assistance in providing care for this infant.

This infant appears to have an open airway and is breathing adequately, so ventilation is not needed. To obtain more objective data about the infant's condition, you should rapidly proceed to the primary assessment and place the infant on a cardiac monitor and pulse oximeter. Once vascular access is established, begin rapid fluid resuscitation.

The vital signs confirm your initial clinical impression that the infant is in shock.

Lower limits of systolic blood pressures that are considered to define hypotension are

• <60 mm Hg in infants during the first month of life
• <70 mm Hg for infants from 1 month to 12 months of age
• <70 mm Hg + (2 x age in years) for children from 1 to 10 years of age

If a blood pressure measurement device is not readily available, the absence of detectable distal pulses is consistent with hypotensive shock. Indeed, if peripheral pulses are difficult to palpate, you should interpret the results of automated blood pressure devices cautiously because they are not highly reliable in this situation. The failure of a pulse oximeter to detect the pulse when placed on the extremities should raise your concern that the child has poor distal perfusion and is in shock.

Since this infant is in hypotensive shock, you must quickly establish vascular access to enable administration of one or more isotonic crystalloid fluid boluses. Brief attempts to gain peripheral venous access are appropriate. But if they are not rapidly successful, then place an IO needle because the infant is in hypotensive shock.

Laboratory studies will be helpful to objectively determine the severity of shock. You should obtain a bedside glucose determination as soon as possible because infants in shock are at high risk for hypoglycemia.

Shock is a clinical condition in which tissue perfusion is inadequate to meet metabolic demand. In this infant global cardiac output is apparently reduced, but remember that in some forms of shock, cardiac output may be increased (e.g. septic shock). 

Obtain a focused history while you implement the above interventions. The duration of the child's symptoms, allergies, use of any medications, past medical history, fast, feeding, and any events leading up to the infant's presentation are important history elements. The infant most likely has a viral gastroenteritis based on the history, but you should carefully look for the presence of signs suggesting a different cause, such as sepsis. Look for the presence of a skin rash or bruising. Assess the abdomen (ie, is the abdomen distended and tender?) for signs of a potential surgical problem, such as an acute abdomen.

In this infant with hypotensive shock, it is inappropriate to make multiple attempts to insert a peripheral IV catheter. A highly skilled provider may elect to attempt central venous catheter placement, but the most appropriate next step for most providers is to place an IO catheter.

As soon as the needle is placed, you should deliver 20 ml/kg of isotonic crystalloid, such as normal saline. Remember to use a 3- way stopcock or pressure bag to rapidly deliver the fluid since it will generally not flow rapidly through a small peripheral IV or I0 needle.

The fluid should be given as rapidly as feasible, ideally over less than 15 minutes.

If blood is aspirated at the time the 10 access is confirmed, you should perform a bedside glucose determination.

When you reassess the infant, she is slightly improved, but she remains very tachycardic and her distal pulses are still not palpable. These findings indicate that another isotonic crystalloid fluid bolus is indicated.

The following tertiary studies may help assess the severity of acidosis and the presence of hyponatremia or hypernatremia:

• Blood sample to evaluate serum electrolytes
• Repeat bedside glucose test
• Complete blood count will help determine if the infant is anemic, and the white blood cell count may help identify if the infant is at increased risk of bacterial sepsis (either a high or low white blood cell count); it will also confirm whether the infant has adequate oxygen­carrying capacity (ie, hemoglobin concentration)
• Blood and urine cultures if sepsis is considered a risk based on the history and examination
• Urine analysis

It is helpful to place a bladder catheter both to monitor the volume of urine produced and to obtain a urine sample for analysis. Remember that the initial volume of urine in the bladder does not determine the current urine output since you don't know how long the urine has been in the bladder. An indwelling bladder catheter will permit ongoing assessment of urine production, which provides indirect evidence of the effectiveness of renal perfusion.

The infant's normal white blood cell count and platelet count suggests that the infant does not have bacterial sepsis. The hemoglobin concentration is adequate, so the infant is not anemic.

The advanced care provider will calculate the anion gap at 23 mEq/L (including potassium in the calculation); this is an elevated anion gap. It is, however, not as wide as expected by the child's clinical condition. The chloride is relatively high and the bicarbonate is low. It is likely that this infant has a mixed anion gap and non-anion gap acidosis with the latter caused by the loss of bicarbonate in watery diarrhea. This is important to recognize since it will be more difficult to correct the metabolic acidosis without the administration of bicarbonate or a substance that can be readily converted to bicarbonate (eg, acetate). Thus, some advanced providers may change the child's IV fluid to use potassium acetate rather than potassium chloride in this setting. There are different approaches that may be used in this situation, such as adding sodium bicarbonate to half-normal saline or using potassium acetate in the IV maintenance fluids.

The glucose concentration remains low, so you should administer another bolus of glucose and begin a maintenance of glucose infusion. The electrolytes show that the infant's serum sodium concentration is normal, so administration of an isotonic IV fluid such as normal saline or lactated Ringer's solution is appropriate.