may reveal leukocytosis and/or thrombocytosis CSF usually shows a pleocytosis, with a lymphocytic predominance Sterile pyuria is sometimes noted In some cases of Kawasaki disease, findings consistent with myocardial ischemia or an arrhythmia may be noted on ECG, and coronary artery aneurysms may be discovered with an echocardiogram Endocrine Disorders (See Chapter 89 Endocrine Emergencies ) Infants with congenital adrenal hyperplasia (CAH) usually present in the first few weeks of life with a history of vomiting, lethargy, or irritability Signs of marked dehydration may be present with tachycardia and possibly hypothermia History may reveal that these infants have been poor feeders since birth and the symptoms may be progressive over a few days The physical examination can be helpful in females if ambiguous genitalia are noted The presence of marked hyponatremia with severe hyperkalemia on laboratory evaluation suggests CAH Other findings in this disorder include hypoglycemia and metabolic acidosis Evaluate for peaked T waves or arrhythmias on ECG as hyperkalemia may result in sudden cardiac arrest Elevated 17-hydroxyprogesterone and renin, with decreased serum aldosterone and cortisol, confirm the diagnosis of CAH Metabolic Disorders Prolonged diarrhea or vomiting can produce hypoglycemia, dehydration, electrolyte disturbances, and acid–base abnormalities such that an infant will appear quite ill Young infants with diarrhea may develop marked hyponatremia caused by sodium losses or iatrogenic water intoxication The latter occurs when well-meaning parents feed excess free water or improperly mix concentrated formula, leading to a rapid drop in serum sodium Such infants may appear lethargic, with slow respirations, hypothermia, and, possibly, seizures that are difficult to control Likewise, dehydrated infants with hypernatremia may be lethargic or irritable, with muscle weakness, seizures, or coma Persistent vomiting may lead to hypochloremic alkalosis with hypokalemia, causing weakness or cardiac dysfunction (see Chapters 22 Dehydration and 100 Renal and Electrolyte Emergencies ) A special cause of hyponatremic dehydration to consider is cystic fibrosis Vague symptoms in the history include poor feeding, poor growth, and increased lethargy The parents may report that the infant gets ill in hot weather and that the baby’s skin tastes salty The baby may have also had meconium plug syndrome (transient distal colonic obstruction caused by inspissated meconium), prolonged jaundice, or prior pulmonary symptoms such as cough, tachypnea, or pneumonia Laboratory tests show profound hyponatremia that is not accounted for by gastrointestinal losses A sweat test or DNA analysis will help confirm the diagnosis Rare inborn errors of metabolism, such as inherited urea cycle disorders , may produce vomiting in young infants, who will then present with lethargy, seizures, or coma resulting from metabolic acidosis, hyperammonemia, or hypoglycemia (see Chapter 95 Metabolic Emergencies ) Galactosemia is due to a genetic defect in the metabolism of galactose and presents with vomiting, acidosis, failure to thrive, and jaundice when exposed to this sugar Hypoglycemia and liver dysfunction with coagulopathy are often present, and many develop urinary tract infections or sepsis due to gram-negative organisms Testing with a CBC, electrolytes, bicarbonate, blood glucose, liver function (including coagulation studies), urinalysis for ketones, and plasma ammonia levels is indicated in young infants with gastroenteritis, lethargy, or irritability to evaluate for metabolic conditions Collect extra plasma (2 mL) and urine (5 mL) for additional testing, ideally before providing fluid resuscitation and dextrose Inquiry about neonatal screening is important; consider sending a follow-up blood filter paper specimen to the newborn screening laboratory Rapid bedside testing for glucose and sodium is recommended for immediate recognition and therapy Hypoglycemia also can be secondary to sepsis, certain drugs, or alcohol intoxication Young infants are incapable of accidental ingestions, but one should consider toxins (see Chapter 102 Toxicologic Emergencies ) in certain cases Wellmeaning parents may rarely cause salicylism in their attempts to aggressively treat fever with aspirin Affected infants can then present with vomiting, hyperpnea, hyperpyrexia, convulsions, or coma The history of medication given is crucial because the physical examination will not distinguish this ill baby from the infant with sepsis The laboratory evaluation may lead to the suspicion of a metabolic problem because abnormalities of sodium, blood sugar, or acid–base balance are often found Moreover, hypokalemia can be seen in salicylism, as well as abnormal liver function or renal function studies An elevated salicylate level in the serum confirms the diagnosis of aspirin poisoning, but in chronic poisoning, the aspirin level may be relatively low, even in patients with a fatal course Carbon monoxide poisoning may present as an unknown intoxication when families are unaware of a defective heating system in the home A history of sluggishness, poor feeding, vomiting, and other family members who are also ill with headache, syncope, or flu-like symptoms that improve after leaving the home environment, suggest this poisoning The classic “cherry red” skin color may be lacking, and physical examination may reveal only lethargy Elevation of the carboxyhemoglobin level is diagnostic Renal Disorders (See Chapter 100 Renal and Electrolyte Emergencies ) A young infant may also appear extremely ill because of renal failure or dysplasia Posterior urethral valves, especially in males, can cause bladder outlet obstruction and resultant renal failure Approximately one-third of these cases are diagnosed by week of age, but more than half go undetected for the first few months of life The parents may give a history of vomiting, poor appetite, inadequate weight gain, or an abdomen that appears swollen A careful review of systems may reveal a weak urinary stream On physical examination, hypertension or an abdominal mass (hydronephrosis) may be detected, as well as urinary ascites A suprapubic ultrasound may demonstrate the dilated posterior urethra and bladder and a voiding cystourethrogram will show a dilated posterior urethra, hypertrophy of the bladder neck, and trabeculated bladder The serum creatinine and blood urea nitrogen levels may be markedly elevated Urosepsis is a possible complication of posterior urethral valves Hematologic Disorders Any infant with severe anemia caused by aplastic disease, hemolytic process, or blood loss can look quite ill (see Chapter 93 Hematologic Emergencies ) Disorders of hemoglobin such as methemoglobinemia can also cause an infant to appear toxic and may be inherited or acquired Transient methemoglobinemia in infants is occasionally caused by environmental toxicity from oxidizing agents such as nitrates found in well water or oxidant drugs (e.g., topical benzocaine in teething gels) This intoxication presents with cyanosis, poor feeding, failure to thrive, vomiting, diarrhea, and lethargy In other patients, the oxidant stress is less obvious, causing severe diarrhea and metabolic acidosis It is postulated that the infectious agent that causes the diarrhea or the secondary metabolic acidosis may produce an oxidant stress that leads to methemoglobin formation These infants are lethargic, with hypothermia, tachycardia, tachypnea, and hypotension, and often appear mottled, cyanotic, or ashen One key to the diagnosis of methemoglobinemia is that oxygen administration does not affect the cyanosis (similar to CHD with right-to-left shunt) Laboratory tests show a profound acidosis (pH 6.9 to 7.2), yet the PaO is normal despite the cyanosis Leukocytosis and thrombocytosis are present, and prerenal azotemia may be noted The blood itself may appear chocolate brown (most easily noted when a drop of blood on filter paper is waved in the air and compared with a normal control), and methemoglobin levels will be elevated up to 65% (normal 0% to 2%) Hemoglobin electrophoresis will be normal (except in rare cases of hemoglobin M), as is the glucose-6-phosphate dehydrogenase assay in most cases With appropriate treatment, the methemoglobin level returns to normal However, death can occur from methemoglobinemia in infants if not treated promptly Kernicterus, or bilirubin encephalopathy (see Chapter 96 Neonatal Emergencies ), should be considered in the septic-appearing infant with neurologic findings This usually occurs in the first week of life in jaundiced neonates due to the deposition of indirect bilirubin in the basal ganglia and brainstem nuclei Premature infants are more susceptible to kernicterus, but the majority of infants who develop kernicterus are healthy, term infants who predominantly breast-feed Lethargy and decreased feeding present early, and with progression the infant will develop respiratory distress and neurologic signs, including decreased reflexes, a high-pitched cry, arching, opisthotonic posturing, twitching of the extremities, and convulsions The neonate can even develop a bulging fontanel, making it difficult to differentiate from meningitis on clinical examination Laboratory evaluation is crucial; obtain total and direct bilirubin counts, a CBC, blood typing, and Coombs test Kernicterus usually does not develop until the total bilirubin level has exceeded 25 to 30 mg/dL, but toxicity has occurred at levels as low as 20 mg/dL Gastrointestinal Disorders (See Chapter 91 Gastrointestinal Emergencies ) Gastroenteritis in an infant can rapidly lead to profound dehydration and shock Hypoglycemia is also common in these young infants and can cause lethargy and coma Bacterial infections such as Salmonella may cause sepsis in a young infant, and viral agents may mimic this A history of bloody diarrhea suggests bacterial gastroenteritis A CBC with many band forms despite a normal white blood cell (WBC) count suggests Shigella infection Stool cultures will diagnose infections, but a few days are needed for bacterial isolation and viral isolation takes even longer Rapid PCR detection of common gastrointestinal pathogens in stool is available at many institutions Fluid resuscitation may improve the infant’s appearance and make dehydration the likely diagnosis There are several intra-abdominal surgical emergencies that mimic sepsis The underlying pathophysiology is some combination of hypovolemia, electrolyte disturbances, hypoglycemia, and/or metabolic acidosis Small bowel obstruction (SBO) caused by volvulus , intussusception , or incarcerated hernia will generally