Birth Asphyxia: A Review of the Clinical Problem
Outcome Studies of Birth Asphyxia
Clearly, there is considerable evidence that the global mortality rate due to birth asphyxia is very high. It is also recognized that recovery from birth asphyxia is often associated with permanent handicaps.
Saroj Saigal of McMaster University, Hamilton, Canada first reviewed existing follow-up studies on victims of perinatal asphyxia in the developed world. She found that, even from those regions, data on this subject is limited, with very few longer-term studies to school-age.
Her review of a population-based study from Western Australia (1993-96 births) indicated that the outcome (death and disability) was directly related to the severity of neonatal encephalopathy (NE) (1) (Figure 4.1, 4.2). It was evident that “moderate/severe” NE was clearly associated with permanent neurologic and developmental delay and cognitive problems. Subjects with history of seizures were three times more likely to develop cerebral palsy than those without.
One of the earliest and longest duration studies of NE was reported from Alberta, Canada. The incidence of impairments (CP, blindness, cognitive delay and hearing loss) was 16% for all grades of NE. However, scores on intellectual language and achievement measures were significantly below those with mild NE and the comparison group. Children with mild NE had school performance scores similar to those of their peers. A summary of outcome studies of birth asphyxia in children in the developed world (2-5) is shown in Figures 4.3 and 4.4.
Dr. Saigal then explored studies regarding permanent residua in survivors of NE associated with perinatal asphyxia in the developing world. The evidence was extremely sparse.
One excellent prospective study was done in Kathmandu, Nepal (6) (Figure 4.5). In that study 97% of patients with severe NE died. Moderate NE survivors had a high risk (59%) of major impairments (Figure 4.6). The authors of the Kathmandu study then compared their results to a study carried out in the UK using similar criteria for assessment of NE. All cases of severe HIE had poor outcomes. However, the death and disability incidences after moderate HIE were 15-25% in the UK, but were 71% in the Kathmandu study. Several other studies showed similar disparities between outcomes in developed and developing regions .
Dr. Saigal indicated that there is a “crying need” for more information on outcomes following NE. However she acknowledged that conducting outcome studies in developing regions is very difficult. Among the hindrances are poverty, illiteracy, lack of financial resources to conduct such studies, non-standardized definitions of NE and poor compliance. In addition, the conventional tests for follow-up evaluation have involved complex psychomotor testing which would not be easily applicable in the developing world (Figure 4.7, 4.8).
Dr. Saigal indicated that the question is who should be followed and how. She recommended that a population-based, community survey could be performed using standardized definitions of NE with an ideal study period of 2-3 years (Figure 4.9). She defined the criteria for such a study and discussed simpler, cost-effective measures using questionnaires which could be applied in a community setting. These are presented in the following section entitled “Examples of Available Questionnaire and Criteria for Severe Disability” (Figure 4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20, 4.21, 4.22, 4.23, 4.24, 4.25 - see below for links to each figure)
3. Pierrat V, Haouari N, Liska A, Thomas D, Subtil D, Truffert P, on behalf of the Groupe d’Etudes en Epidemiologie Perinatale. Prevalence, causes, and outcome at 2 years of age of newborn encephalopathy: population based study. Arch Dis Child Fetal Neonatal Ed 2005;90:F257-F261.
5. Miller SP, Weiss J, Barnwell A, Ferriero DM, Latal-Hajnal B, Ferrer-Rogers A, Newton N, Partridge JC, Glidden DV, Vigneron DB, Barkovich AJ. Seizure-associated brain injury in term newborns with perinatal asphyxia. Neurology 2002;58:542-548.