IVH is a common problem in premature neonates that can lead to significant neurological complications and even death. Our study reveals an overall IVH incidence of 25% confirming the high prevalence in preterm infants. Fortunately, most cases were low grade; 22% were classified as mild IVH (grade I and II) and only 3% were classified as severe IVH (grade III and IV). The standard protocol in our NICU is consistent with national guidelines and includes a screening HUS once in the first week of life and a second follow-up HUS, at either DOL 28 or 36 weeks PMA, whichever comes first. It is generally assumed that infants with no IVH or low grade IVH do not progress. Our study revealed that the rate of progression was indeed quite low in our cohort, with only 4 out of 343 (1.2%) progressing from a negative or mild IVH to a severe grade. Each of these 4 infants required mechanical ventilation for at least 40 days. Thus, in the absence of prolonged mechanical ventilation or clinical suspicion of clinical deterioration, our data suggests that additional HUS studies for mild cases of IVH may be extraneous.
Concern for progression of IVH warrants performance of additional HUS. However, in the absence of clinical deterioration or suspicion of worsening of HUS, additional HUS studies may be unnecessary. 331 HUSs in our cohort were felt to be potentially unnecessary; chart review did not reveal risk factors for IVH progression (hypotension, sudden onset of anemia, etc.). HUS studies are relatively low cost, minimally invasive, and the scans and results can be completed quickly, typically within hours. However, babies in the NICU are typically quite ill, connected to multiple monitors, and are subjected to many different screening tests, procedures, and exams. Reducing any one of these diminishes the burden on the baby. HUSs also require time and resources of NICU providers and staff. Eliminating even a fraction of the 331 HUSs considered excessive would translate into significant cost savings as well as a savings of valuable NICU time and resources.
In our analysis, we excluded 237 infants because they did not receive a HUS during DOL 3-10. While this is a substantial portion of our population, our hospital’s protocol for routine head ultrasound screening begins at DOL 3. This is because any HUS performed before DOL3 is done primarily for clinical suspicion of IVH and not for routine screening. In fact, because of the potential for false negative scans on DOL1, and the increased sensitivity of later head ultrasounds, most institutions have initial screens on DOL3, as is our policy. HUS performed prior to DOL 3 are more commonly conducted, not for routine screening, but for clinical suspicion of hemorrhage. However, given this large portion of infants, we reran our analyses on the total cohort. Of the 237 excluded infants, 230 had scans on DOL 0-2 indicating a strong clinical suspicion in the group. If an infant’s clinical course is severe enough to require HUS before DOL 3, their chance of having an abnormal HUS increases significantly. However, the focus of this study was to look at the progression of standard screening HUS based on risk factors, and not clinical status.
When examined the outcomes of the 230 infants, they differed in a number of ways, including demographics, clinical course, and progression of IVH. We noted that significantly more infants had grade IV IVH on initial HUS in the excluded cohort. The average birth weight was significantly lower in the excluded cohort (967.8 grams), considered extremely low birth weight, in comparison to the study cohort who had an average birth weight of 1214.54 grams. Significantly more infants developed bacterial sepsis, required steroids for chronic lung disease, were still on oxygen at 36 weeks, and were more likely to be discharged with oxygen. They also had significantly more surgery for NEC, suspected NEC or bowel perforation, further supporting that these babies were indeed sicker, more complicated infants. In fact, these infants’ IVH progression was more frequent than our original cohort’s pattern, suggesting these infants had severe clinical courses requiring HUS’s for clinical suspicion and not routine screening. Thus, excluding these cases allowed us to appropriately focus on evaluating IVH progression during routine head ultrasound screening. Even so, the overall progression of IVH in both cohorts of infants with no IVH or mild IVH on initial HUS was still quite low (2.3%), proving that mild IVH rarely progresses to a more severe grade.
Surprisingly, 88 infants lacked HUS data and were also excluded. However, most of these infants were primarily > 30 weeks GA and thus, a HUS was presumably deemed unnecessary. Still, the protocol is in place to detect IVH early and to minimize neurologic injury. The finding that many premature infants did not have an ultrasound or had an ultrasound outside of the protocol window has prompted a quality improvement project and focus on protocol compliance at our institution to address this concern.
HUSs remain a necessary screening tool, allowing clinicians to identify babies with more severe grades of IVH. Those infants that are determined to have grade III or IV IVH, may require intervention including shunting, drainage, or even craniotomy. The screening HUS at 28 weeks or 36 weeks gestational age is performed to screen for periventricular leukomalacia (PVL). PVL is coagulative and necrotic injury of the white matter of the brain near the lateral ventricles which can result in severe neurologic deficits(14). Early detection and treatment is important for successful outcomes in both of these high-risk populations.
The limitations of this study include the retrospective chart review study design as well as being a single-center cohort. The potential inter-radiologist variability was addressed by having one radiologist read and grade a random sampling of HUS in our study and cross-reference accuracy to verify validity. Of the randomly sampled HUSs that were reread, no HUS interpretation changed from mild to severe IVH during this regrade; those that were originally graded as mild IVH were graded as mild IVH this time, as well. We interpreted these findings as confirmation that there is minimal radiologist variability, and any variability that is present does not impact the severity of the grading.
This is one of the larger single-center studies in the current literature. Given the rapid changes in the field of neonatology (differences in utilization of steroids, changes in surfactant utilization and ventilator management strategies, etc.) this study also reflects more recent neonatology practice, as the larger prior epidemiologic studies describing IVH and HUS screening recommendations were published over 7 years ago(2, 3, 12).