Foundations of knowledge about neonatal pain.

This review appraises trends in the neonatal pain research literature. We searched the literature produced from 1941 to 2001. Information about the model of pain, measures of pain, design, and sample characteristics is included for each citation. Gaps in knowledge are attributed to specific conceptual and methodological problems, including the lack of basic knowledge about pain behavior, over-reliance on an invasive short-term pain model, pain measurement issues, and lack of knowledge about confounders. Ethological research methods could be used to expand basic knowledge about newborn pain.