Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (274 page)

During the Neonatal Period

   Respiratory distress syndrome (RDS) is diagnosed by clinical findings, increased work of breathing, increased oxygen requirement, and chest radiograph showing diffuse reticular ground glass appearance and air bronchial grams. Arterial blood gas measurements will reveal hypoxia and elevated CO
₂
. Chemistry may reveal hyponatremia due to water retention.

   Hypoglycemia and hypocalcemia may be monitored with serum chemistry.

   Anemia of prematurity due to insufficient erythropoietin production and shorter RBC life span of approximately 35–50 days (term infant = 60–70 days) may be detected on hemogram. Hematocrit at term is usually 60%; this drops rapidly over the first 2 weeks and by 4 weeks reaches 35% on average with a nadir at 8–10 weeks of 30%. Preterm infants’ HCT averages 41% at 26–30 weeks, 45% at 28 weeks, and 47% at 32 weeks.
¹

   Hemolytic disease of the newborn (erythroblastosis fetalis) due to Rh/ABO immunization may result in anemia with extramedullary hematopoiesis and ultimately organ failure and death. Maternal and fetal ABO and Rh testing should be performed. In addition, a direct antiglobulin (Coombs) test will be positive.

   Infections are more common in preterm than in term newborns (e.g., lateonset nosocomial infection by coagulase-negative staphylococci and fungi with central venous catheters; sepsis or pneumonia due to amnionitis); appropriate culture should be performed.

   Neonatal hyperbilirubinemia (see Chapter
5
).

Reference

1.  Gilbert-Barness E, Barness LA.
Clinical Use of Pediatric Diagnostic Tests
. Philadelphia, PA: Lippincott Williams & Wilkins; 2003.

OBSTETRIC DISORDERS

AMNIOTIC FLUID EMBOLISM

Amniotic fluid embolism is an emergency occurring during labor or shortly after delivery with cardiogenic shock, respiratory failure, and frequently death. The diagnosis is made on physical examination with rapidly progressive hypotension progressing to shock. Blood tests will show a consumptive coagulopathy (DIC), hypoxemia, and acidosis. Unfortunately, many cases are confirmed only at autopsy. Amniotic debris consisting of squamous cells, mucin, and lanugo from the fetus can be found in the peripheral blood or on autopsy sections of the lung in the mother (see eBook Figure 8-12).

CHORIOAMNIONITIS
^*

   Definition and Etiology

   Intra-amniotic infections (IAI) include infections of amniotic fluid, membranes, or placenta. IAIs are a significant cause of fetal demise, premature delivery, neonatal sepsis and pneumonia, and maternal bacteremia and sepsis (see eBook Figure 8-13).

   Most IAIs are caused by vaginal microorganisms that gain access to the uterine cavity. These ascending infections are most common as a result of premature rupture of the fetal membranes. Fetal infection may also be caused by hematogenous transmission from the maternal circulation. This route is most common for viral pathogens.

   The etiology is broad. Mixed infections are common. Pathogens associated with IAI include the following: Anaerobes, including
Bacteroides
spp.,
Fusobacterium
spp., and anaerobic gram-positive cocci;
E. coli
,
Proteus mirabilis
, and other enteric gram-negative rods;
Enterococcus
spp.;
Listeria monocytogenes;
group B
Streptococcus
, and group A
Streptococcus
;
Ureaplasma urealyticum
and
Mycoplasma hominis
. Nonbacterial pathogens include
Toxoplasma gondii
and viruses (e.g., CMV, HSV, rubella).