PEDIATRICS Vol. 106 No. 4 October 2000, pp. 828

COMMENTARY:
Commentary on Cerebral Intravascular Oxygenation Correlates With Mean Arterial Pressure in Critically Ill Premature Infants

Since the original work of Wigglesworth and Pape¹ and Perlman et al,² fluctuations in cerebral perfusion have been recognized as a major causal factor in the pathogenesis of germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH) in the very preterm infant. Lou and colleagues,³ in their pioneering studies using the ¹³³Xenon clearance technique, first suggested that some critically ill infants might have a pressure-passive cerebral circulation, thus allowing abrupt changes in arterial blood pressure to be transmitted directly to the brain microvasculature. This was supported by the work of Pryds,⁴ who found that preterm infants with evidence of a pressure-passive cerebral circulation did indeed have a greater risk of GMH-IVH, compared with those with apparently intact cerebrovascular control mechanisms.

Tsuji and colleagues⁵ have added further weight to this concept with the provocative and interesting study published in this volume. They used the statistical coherence between continuous measurements of mean arterial blood pressure and cerebral oxygenation (determined by near infrared spectroscopy) as an index of impaired cerebrovasculature autoregulation. Infants with impaired regulation in the first 3 days of life had a significantly greater incidence of hemorrhagic and ischemic lesions. It is plausible that impaired regulation is more likely in the presence of very large fluctuations in arterial blood pressure. It would be interesting to know whether the magnitude of blood pressure swings was also positively related to the likelihood of developing a lesion. The first cranial ultrasound examination was on day 3 in this study, and it remains possible that in some infants impaired vascular regulation was a consequence of cerebral injury rather than a causal factor. Other studies have suggested that an initial period of hypoperfusion may predispose to subsequent hemorrhage,^6,7 possibly by impairing the integrity of the capillaries within the subependymal germinal matrix. It seems likely that both these mechanismsischemia/reperfusion vascular injury and the transmission of abrupt changes in perfusion via a pressure-passive circulationare important in the pathogenesis of GMH-IVH and further studies are required to illuminate the precise pathogenetic sequence.

Near infrared spectroscopy has been used in preterm infants undergoing intensive care since the mid 1980s,^8,9 but progress has been frustratingly slow. Although the technique has still to demonstrate real clinical utility in the care of the critically-ill newborn, this latest study provides fresh impetus to those of us who believe that continuous optical monitoring of the brain offers a genuine prospect of "brain-oriented intensive care" in the neonatal nursery.

John Wyatt, BSc, MBBS, FRCP
Judith Meek, MBBS, PhD, MRCP
Department of Paediatrics
University College London
London, United Kingdom

FOOTNOTES

Received for publication Aug 8, 2000; accepted Aug 8, 2000.

ABBREVIATIONS

GMH-IVH, germinal matrix hemorrhage-intraventricular hemorrhage.

REFERENCES

1. Wigglesworth JS, Pape KE. Haemorrhage, Ischaemia and the Perinatal Brain. London, United Kingdom: William Heinemann; 1979
2. Perlman JM, McMenamin JB, Volpe JJ Fluctuating cerebral blood-flow velocity in respiratory-distress syndrome: relation to the development of intraventricular hemorrhage. N Engl J Med 1983; 309:204-209 [Abstract]
3. Lou HC, Lassen NA, Friis-Hansen B Impaired autoregulation of cerebral blood flow in the distressed newborn infant. J Pediatr 1979; 94:118-121 [CrossRef][Medline]
4. Pryds O Control of cerebral circulation in the high-risk neonate. Ann Neurol 1991; 30:321-329 [CrossRef][Medline]
5. Tsuji M, Saul JP, du Plessis A, Eichenwald E, Sobh J, Crocker R, Volpe JJ Cerebral intravascular oxygenation correlates with mean arterial pressure in critically ill premature infants. Pediatrics 2000; 106:625-632 [Abstract/Free Full Text]
6. Meek JH, Tyszczuk L, Elwell CE, Wyatt JS Low cerebral blood flow is a risk factor for severe intraventricular haemorrhage. Arch Dis Child Fetal Neonatal Ed 1999; 81:F15-F18 [Abstract/Free Full Text]
7. Kluckow M, Evans N Low superior vena cava flow and intraventricular haemorrhage in preterm infants. Arch Dis Child Fetal Neonatal Ed 2000; 82:F188-F194 [Abstract/Free Full Text]
8. Brazy JE, Lewis DV, Mitnick MH, Jobsis vandervliet FF Noninvasive monitoring of cerebral oxygenation in preterm infants: preliminary observations. Pediatrics 1985; 75:217-225 [Abstract/Free Full Text]
9. Wyatt JS, Cope M, Delpy DT, Wray S, Reynolds EO Quantification of cerebral oxygenation and haemodynamics in sick newborn infants by near infrared spectrophotometry. Lancet 1986; 2:1063-1066 [CrossRef][Medline]