Validation of two scoring systems which assess the degree of physiologic instability in critically ill newborn infants.

Modifications of the Physiologic Stability Index (PSI) and Therapeutic Intervention Scoring System (TISS) were used to evaluate the physiologic stability and need for therapeutic intervention in 55 infants hospitalized in the newborn ICU. After modifying the PSI to reflect neonatal physiology, we found that PSI scores correlated significantly with TISS values (r = .75, p less than .001) and Nursing Utilization Management Intervention System (NUMIS) classifications (r = .62, p less than .001). TISS values also correlated with NUMIS scores (r = .72, p less than .001). PSI and TISS scores increased significantly with each increase in NUMIS classification (p less than .001 for all comparisons). PSI and TISS scores decreased significantly between admission and either discharge (n = 41) or day 14 of hospitalization (n = 14, p less than .001). PSI and TISS scores were greater on days 1 and 5 in infants with hyaline membrane disease when compared with infants with transient tachypnea (p less than .001). Infants with PSI scores greater than or equal to 4 and TISS scores greater than or equal to 7 on day 1 took significantly longer to achieve adequate protein-calorie intakes than infants with lower first-day scores (p less than .002). The modified PSI and the TISS scoring systems are both useful objective measurements of the degree of physiologic instability in newborn infants requiring intensive care, and both scores identify those at increased risk for nutritional morbidity.