Non-invasive measurement of local tissue perfusion and its correlation with hemodynamic indices during the early postnatal period in term neonates

Noninvasive Monitoring to Demonstrate Postoperative Differences in Regional Hemodynamics in Newborn Infants With d-Transposition of the Great Arteries and Hypoplastic Left Heart Syndrome

BACKGROUND

The adequacy of tissue O₂ delivery in infants receiving intensive care is difficult to measure directly. Regional O₂ (rSO₂) and fractional tissue O₂ extraction (FTOE), the ratio of O₂ consumption to O₂ delivery, obtained from newer noninvasive tools, such as near-infrared spectroscopy (INVOS) and microvascular tissue oximetry (T-Stat) can provide important information on the adequacy of tissue oxygenation and aid in managing critically ill infants.

METHODS

We prospectively evaluated differences in rSO₂ and FTOE in 26 infants with hypoplastic left heart syndrome (HLHS) (n = 12) or d-transposition of the great arteries (d-TGA) (n = 14). Continuous noninvasive monitoring of SpO₂, heart rate, and perfusion index with pulse oximetry, cerebral-rSO₂ and renal-rSO₂ with INVOS, and buccal tissue oxygenation using T-Stat were performed during immediate postoperative period for 24 hours.

RESULTS

The SpO₂ and rSO₂ in infants with d-TGA were higher compared with the infants with HLHS at all measured sites (buccal mucosa, cerebral, and renal). Significant regional differences were also observed in FTOE across all infants with the highest at the buccal mucosa tissue level, followed by cerebral and renal measurement sites. As compared with infants with d-TGA, infants with HLHS had higher regional FTOE and heart rate, with a lower arterial O₂ content and perfusion index.

CONCLUSIONS

Our study demonstrates the utility of noninvasive hemodynamic monitoring to assess regional oxygenation and perfusion, as evidenced by significant differences in infants with HLHS and d-TGA, conditions with different circulation physiologies. Such comprehensive monitoring can potentially aid in evaluating treatment strategies aimed at preventing organ damage from O₂ insufficiency.

Evidence-based versus pathophysiology-based approach to diagnosis and treatment of neonatal cardiovascular compromise

With the advances in biomedical research and neonatal intensive care, our understanding of cardiovascular developmental physiology and pathophysiology has significantly improved during the last few decades. Despite this progress, the current management of circulatory compromise depends primarily on experts' opinions rather than high level of evidence. The lack of reliable, accurate, continuous and preferably non-invasive monitoring techniques has further limited our ability to collect the information needed for the design and execution of more sophisticated clinical trials with a better chance to provide the evidence we need. Given the lack of randomized, placebo-controlled trials investigating clinically relevant outcomes of novel treatments of neonatal cardiovascular compromise, we must now use the available lower level of evidence and our present understanding of developmental physiology and pathophysiology when providing cardiovascular supportive care to critically ill neonates. However, with recent advances in cardiovascular monitoring capabilities, direct and more objective assessment of the changes in cardiovascular function, organ blood flow, and tissue oxygenation have become possible. These advances have helped in our clinical assessment and enabled us to start designing more sophisticated interventional clinical trials using clinically relevant endpoints.