Effects of repeated indomethacin administration on cerebral oxygenation and haemodynamics in preterm infants: combined near infrared spectrophotometry and Doppler ultrasound study

Management of patent ductus arteriosus in preterm infants--where do we stand?

Patent ductus arteriosus (PDA) in preterm infants is a controversial topic in the management of preterm neonates. There are no generally accepted guidelines for diagnosis, treatment, and follow-up of PDA, and few publications have covered the whole topic or have been conclusively summarized to give a proper direction for the treating physician. Major issues remain to be clarified, both with respect to diagnosis and treatment. The definition of hemodynamic significance varies because of different use of echocardiographic criteria and uncertainty about the role of biomarkers. The detailed risks and benefits of available treatment alternatives are still under investigation. There has been a general shift in the management of PDA in preterm neonates from the "aggressive approach" to a more "conservative approach," but the effects of this strategy on morbidity in a longer time perspective are not fully known. An individualized therapeutic strategy with special emphasis on identification of hemodynamically significance seems to be the way forward. In this review we put forward the scientific background in favor of a seemingly growing body of evidence against active treatment, but we raise caution against shying away from all forms of treatment or instituting them too late. Finally, we try to integrate the current knowledge into suggestions for the management of PDA in premature infants.

Managing the patent ductus arteriosus in the premature neonate: a new look at what we thought we knew

Over recent years, the clinical approach to patency of the ductus arteriosus in the premature neonate has been the subject of intensive reevaluation. What had once been considered inherently obvious is no longer to be taken for granted. In this review we will focus on some of the controversies surrounding various aspects of the pharmacologic treatment regimens for patent ductus arteriosus closure. The pros and cons of prophylactic vs therapeutic indomethacin, of early vs late therapy, of high- vs low-dose indomethacin, of single vs multiple courses of treatment, and of ibuprofen vs indomethacin will be considered. In addition, the possibility that patency of the ductus arteriosus is merely a physiological manifestation of extreme prematurity, and thus does not necessarily need to be therapeutically closed, has become a viable approach in some cases. As such, we will examine echocardiographic and biochemical criteria aimed at determining the clinical and hemodynamic significance of ductal shunting, and thereby of the need to treat. Finally, we speculate on potential therapeutic directions for the future, including individualized treatment regimens and multidrug treatment cocktails for those who fail initial monodrug therapy.

Cerebral Oxygenation Monitoring: A Strategy to Detect IVH and PVL

Premature infants are at risk for intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL) theorized to be a result from fluctuations in cerebral blood flow. Monitoring cerebral oxygenation offers a method to observe changes in cerebral blood flow that may be beneficial for detecting and preventing IVH and PVL. This article explains the potential for cerebral oxygenation monitoring in detecting IVH and PVL using cerebral oximetry, reviews current knowledge known about cerebral oxygenation, and describes current challenges for cerebral oxygenation to be the next neuroprotective vital sign.

Does indomethacin for closure of patent ductus arteriosus affect cerebral function?

OBJECTIVE

To study whether indomethacin used in conventional dose for closure of patent ductus arteriosus affects cerebral function measured by electroencephalograms (EEG) evaluated by quantitative measures.

STUDY DESIGN

Seven premature neonates with haemodynamically significant persistent ductus arteriosus were recruited. EEG were recorded before, during and after an intravenous infusion of 0.2 mg/kg indomethacin over 10 min. The EEG was analysed by two methods with different degrees of complexity for the amount of low-activity periods (LAP, "suppressions") as an indicator of affection of cerebral function.

RESULTS

Neither of the two methods identified any change in the amount of LAPs in the EEG as compared to before the indomethacin infusion.

CONCLUSION

Indomethacin in conventional dose for closure of patent ductus arteriosus does not affect cerebral function as evaluated by quantitative EEG.

Effects of skin on bias and reproducibility of near-infrared spectroscopy measurement of cerebral oxygenation changes in porcine brain

The influence of skin on the bias and reproducibility of regional cerebral oxygenation measurements is investigated using cw near-infrared spectroscopy (NIRS). Receiving optodes are placed over the left and right hemispheres of a piglet (C3, C4 EEG placement code) and one transmitting optode centrally (Cz position). Optical densities (OD) are measured during stable normo, mild, and deep hypoxemia. This is done for skin condition 1: all optodes on the skin; skin condition 2: transmitting optode on the skin and one receiving optode on the skull; and skin condition 3: all optodes on the skull. Absolute changes of oxy- (cO2Hb), deoxyhemoglobin (cHHb), and total hemoglobin (ctHb) concentrations [micromolL] are calculated from the ODs. These absolute changes are calculated for each skin condition with respect to normoxic condition. Additionally, for skin condition 2, the difference of concentration changes between receiver 1 (skull) and receiver 2 (skin) is calculated. The effect of skin removal is an average increase of attenuation changes by a factor of 1.66 (=0.51 OD) and of the concentration changes due to the arterial oxygen saturation steps by 23%. We conclude that skin significantly influences regional oxygenation measurements. Nevertheless, it is hypothesized that the estimated concentration changes are dominated by changes of the oxygenation in the brain.

Oxygenation and hemodynamics in left and right cerebral hemispheres during induction of veno-arterial extracorporeal membrane oxygenation

OBJECTIVE

Oxygenation and hemodynamics in the left and right cerebral hemispheres were measured during induction of veno-arterial extracorporeal membrane oxygenation (VA-ECMO).

STUDY DESIGN

Using near infrared spectrophotometry, effects of right common carotid artery (RCCA) and right internal jugular vein (RIJV) ligation and start of VA-ECMO on concentrations of oxyhemoglobin, deoxyhemoglobin, and cerebral blood volume (CBV) were evaluated in 10 newborn infants. Mean cerebral blood flow velocity (CBFV) in the major cerebral arteries was compared before and after the start of VA-ECMO (pulsed Doppler ultrasonography).

RESULTS

RCCA ligation caused a decrease in oxyhemoglobin concentration and an increase in deoxyhemoglobin concentration. RIJV ligation caused no changes. Sixty minutes after the start of VA-ECMO, oxyhemoglobin concentration and CBV had increased, and deoxyhemoglobin concentration had decreased. There were no differences between the hemispheres. Mean CBFV had increased in the left internal carotid artery, and it increased equally in both middle cerebral arteries. Flow direction was reversed in the right internal carotid artery. Three patients had asymmetric cerebral lesions, not related to differences in the measurements between the cerebral hemispheres.

CONCLUSION

The initiation of VA-ECMO causes changes in cerebral oxygenation and hemodynamics but without a difference in effect on left and right cerebral hemispheres.

The light still shines, but not that brightly? The current status of perinatal near infrared spectroscopy

Efforts have been made to find new, non-invasive methods for assessing tissue oxygenation and haemodynamics, particularly in the brain of the fetus and the newborn infant. Near infrared spectroscopy (NIRS) is a developmental technique that provides just such a method, allowing calculation of variables such as cerebral blood flow and cerebral blood volume. It can also measure peripheral oxygen consumption. This review is based on our long experience of using NIRS. Basic principles, techniques, validation, and clinical applications are highlighted. Although more than two decades have passed since its introduction, NIRS remains very much a developmental technique, despite technical progression. A great deal more research is required for NIRS to become a routine clinical tool.

Ductus arteriosus with left-to-right shunt during venoarterial extracorporeal membrane oxygenation: effects on cerebral oxygenation and hemodynamics

OBJECTIVE

To investigate the effect on cerebral oxygenation and hemodynamics of a patent ductus arteriosus with left-to-right shunt during venoarterial extracorporeal membrane oxygenation in a lamb model.

DESIGN

Prospective intervention study in animals.

SETTING

Animal research laboratory of a university medical center.

SUBJECTS

Six anesthetized newborn lambs with patent ductus arteriosus and left-to-right shunt, installed on venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

Six lambs of 140 days gestational age were prepared to keep the ductus arteriosus open by infiltration of the vessel wall with formaline 10%. The animals were installed on standard venoarterial extracorporeal membrane oxygenation. With a mechanical occluder, the ductus was closed.

MEASUREMENTS AND MAIN RESULTS

Changes of mean arterial blood pressure and carotid artery blood flow were measured simultaneously. Using near infrared spectrophotometry, we calculated changes in cerebral concentration of oxyhemoglobin and deoxyhemoglobin (reflecting changes in cerebral oxygen supply) and total hemoglobin (reflecting changes in cerebral blood volume). Also, cerebral oxygen delivery before and after ductus closure was calculated. Before ductus closure there was a left-to-right shunt with a mean +/- SEM of 41 +/- 20% of total body blood flow. Closure of the ductus resulted in an immediate increase in mean arterial blood pressure and carotid artery blood flow. The concentration of oxyhemoglobin increased and the concentration of deoxyhemoglobin decreased, representing increased cerebral oxygen supply. The concentration of total hemoglobin was unchanged, representing unchanged cerebral blood volume. There was an increase in cerebral oxygen delivery.

CONCLUSIONS

In this lamb model, a considerable left-to-right shunt over the ductus during venoarterial extracorporeal membrane oxygenation reduced cerebral circulation and oxygenation.

New technologies in pediatric neurology. Near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a relatively new technology that offers the enormous advantage of making measurements in vivo of changes in cerebral hemodynamics and oxygenation. Because NIRS is noninvasive and portable, it can provide real-time measurements of these changes at the bedside. Thus NIRS is ideally suited to the study of many physiological and pathological processes affecting the brain, particularly in the infant or young child in the intensive care unit or operating room. This review outlines the basic principles, advantages, and limitations of the current state of NIRS technology. An emphasis is placed on the animal and clinical studies that are relevant to the field of child neurology, with an eye to the future evolution and potential applications of this promising technique.

Comparative evaluation of the effects of indomethacin and ibuprofen on cerebral perfusion and oxygenation in preterm infants with patent ductus arteriosus

OBJECTIVE

To compare the effects on cerebral perfusion and oxygenation of intravenous ibuprofen and indomethacin as treatment for patent ductus arteriosus in preterm infants.

STUDY DESIGN

Sixteen infants receiving mechanical ventilation (< 31 weeks gestation) with patent ductus arteriosus received either 0.2 mg/kg indomethacin (n = 8) or 10 mg/kg ibuprofen (n = 8) infused over 1 minute. Near-infrared spectroscopy was used to measure changes in cerebral blood volume and in oxidized cytochrome oxidase concentration. Cerebral blood flow velocity in the pericallosal artery was measured using Doppler ultrasonography.

RESULTS

Indomethacin caused a significant reduction of CBV (maximal changes in cerebral blood volume: -320 +/- 171 microL/100 gm) and, in four of eight patients, a fall in oxidized cytochrome oxidase concentration (maximal change in oxidized cytochrome oxidase concentration in the eight patients: -0.68 +/- 0.98 mumol/L, NS). Cerebral blood flow velocity fell significantly. Ibuprofen caused no significant reduction of cerebral blood volume, oxidized cytochrome oxidase concentration, or cerebral blood flow velocity, whereas a significant increase of cerebral blood volume (+207 +/- 200 microL/100 gm) was observed after 60 minutes. Ductus closure was seen in six of eight infants after the first dose of indomethacin and in five of eight infants after the first dose of ibuprofen. The therapeutic cycle involved administration of a second and third dose, provided no side effects occurred. Treatment was effective in all infants.

CONCLUSION

Compared with indomethacin, treatment with ibuprofen does not significantly reduce cerebral perfusion and oxygen availability; the observed increase in cerebral blood volume requires further investigation.

Near-infrared spectroscopy: theory and applications

In conclusion, NIRS appears to offer both a new monitoring modality and new information about cerebral oxygenation. Technical problems in the application of this technology persist, most notably determination of pathlength and the volume of tissue interrogated. Those familiar with the history of pulse oximetry will recall that although Millikan developed an ear oximeter in 1947, it was not until Aoyagi combined recognition of the pulse signal with spectroscopy in the 1970s that oximetry was transformed into a clinically applicable monitor. In much the same way, NIRS may find the same tremendous usefulness as a noninvasive monitor of cerebral oxygen utilization, pending resolution of the remaining technical problems.