Dating of Asphyxiant Injury
For the forensic neuropathologist (see above), the important questions are: When did the asphyxia occur? What caused it? Did medical malpractice play a role?
The questions can be answered postmortem if the asphyxia can be differentiated from mechanical trauma or other types of injury. The important morphological criteria are summed up in Table 22.2, published by Squier (1993) (see also: pp. 414, 429, 433, 435, 436, 439).
If the child survives, it can be difficult for the clinician as an expert witness to make this distinction. Shevell (2001) has proposed the following operational definition that provides criteria for identifying whether an asphyxia occurred during the antepar-tum, intrapartum, or post partum period.
Antepartum criteria include the mother's report of diminished fetal movement, parameters of impaired fetal growth, and a non-reactive non-stress test (Shevell et al. 1999).
Intrapartum criteria include meconium staining, abnormalities in the fetal heart rate (e.g., late decelerations, bradycardia, etc.), significant metabolic acidosis in a cord or early infant blood sample (pH<7.0, base excess >12), and persistently low Apgar score (<6 beyond 5 min) (Shevell et al. 1999).
The major clinical postpartum criterion is neonatal encephalopathy (see above) marked by alterations in consciousness and tone, brain stem function, seizures, etc.
The American College of Obstetrics and Gynecology and the American Academy of Pediatrics (1992) highlight four diagnostic criteria for perinatal asphyxia:
1. Profound metabolic acidosis
2. Apgar score less than or equal to 5 beyond 5 min
3. Observation of a neonatal encephalopathy
4. Observation of multi-organ dysfunction
These criteria have been largely endorsed by Mac-Lennan and Force (1999).
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