Noninvasive evaluation of splanchnic tissue oxygenation using near-infrared spectroscopy in preterm neonates

Correlation of abdominal rSO2 with superior mesenteric artery velocities in preterm infants

OBJECTIVE

Near-infrared spectroscopy (NIRS) is used to monitor brain and kidney perfusion in at-risk premature and term neonates. Although NIRS holds potential for bedside monitoring of intestinal perfusion, there is insufficient evidence showing correlation with mesenteric blood flow. To determine if an association exists between abdominal regional oxygen saturation (A-rSO2) and mesenteric blood flow, we compared changes in A-rSO2 to changes in blood flow velocity in the superior mesenteric artery (SMA) before and after feedings in very-low birthweight infants.

STUDY DESIGN

A-rSO2 was continuously monitored midline below the umbilicus for 3 days in 18 stable 25 to 31 week bolus-fed infants (median BW 1203 g, median age 5 days). We compared change in SMA velocity from immediately before to 10 min and 60 to 120 min after feeding with change in A-rSO2 over the same time. Spearman's rank correlation was used to ascertain if a significant association existed.

RESULT

Change in A-rSO2 was significantly associated with change in systolic, diastolic, and mean SMA velocity from fasting to 60 to 120 min after feeding (P=0.016, 0.021, 0.010) and from 10 min after a feed to 60 to 120 min after feeding (P=0.009, 0.035, 0.032).

CONCLUSION

In very preterm infants, A-rSO2 reflects blood flow in the SMA and can provide non-invasive continuous monitoring of intestinal perfusion. Further studies are indicated to determine the sensitivity of NIRS to detect early intestinal pathology in this population.

Limited short-term prognostic utility of cerebral NIRS during neonatal therapeutic hypothermia

OBJECTIVE

We evaluated the utility of amplitude-integrated EEG (aEEG) and regional oxygen saturation (rSO2) measured using near-infrared spectroscopy (NIRS) for short-term outcome prediction in neonates with hypoxic ischemic encephalopathy (HIE) treated with therapeutic hypothermia.

METHODS

Neonates with HIE were monitored with dual-channel aEEG, bilateral cerebral NIRS, and systemic NIRS throughout cooling and rewarming. The short-term outcome measure was a composite of neurologic examination and brain MRI scores at 7 to 10 days. Multiple regression models were developed to assess NIRS and aEEG recorded during the 6 hours before rewarming and the 6-hour rewarming period as predictors of short-term outcome.

RESULTS

Twenty-one infants, mean gestational age 38.8 ± 1.6 weeks, median 10-minute Apgar score 4 (range 0-8), and mean initial pH 6.92 ± 0.19, were enrolled. Before rewarming, the most parsimonious model included 4 parameters (adjusted R(2) = 0.59; p = 0.006): lower values of systemic rSO2 variability (p = 0.004), aEEG bandwidth variability (p = 0.019), and mean aEEG upper margin (p = 0.006), combined with higher mean aEEG bandwidth (worse discontinuity; p = 0.013), predicted worse short-term outcome. During rewarming, lower systemic rSO2 variability (p = 0.007) and depressed aEEG lower margin (p = 0.034) were associated with worse outcome (model-adjusted R(2) = 0.49; p = 0.005). Cerebral NIRS data did not contribute to either model.

CONCLUSIONS

During day 3 of cooling and during rewarming, loss of physiologic variability (by systemic NIRS) and invariant, discontinuous aEEG patterns predict poor short-term outcome in neonates with HIE. These parameters, but not cerebral NIRS, may be useful to identify infants suitable for studies of adjuvant neuroprotective therapies or modification of the duration of cooling and/or rewarming.

Transfusion-related necrotizing enterocolitis: a conceptual framework

Necrotizing enterocolitis (NEC) is a disease primarily of prematurity characterized by partial or entire gut necrosis and is associated with significant mortality and morbidity. Recent studies report that approximately 25% to 35% of very low-birth-weight infants less than 1500 g receiving packed red blood cell transfusions develop temporally associated NEC, known as transfusion-related NEC (TR-NEC). Although there are many known risk factors for NEC, this article focuses on 3 contributing factors: packed red blood cell transfusions, enteral feedings, and gastrointestinal immaturity. Previous data suggest that these factors may interact to affect neonatal intestinal tissue oxygenation, which may lead to tissue ischemia, resulting in intestinal injury. This article presents a conceptual framework that combines current theoretical perspectives for TR-NEC, and reviews previous research examining related variables and how their interaction may increase the risk for TR-NEC development. In addition, incorporation of the proposed framework to guide future research and nursing care in this area is discussed.

Global perfusion assessment and tissue oxygen saturation in preterm infants: where are we?

Near infrared spectroscopy (NIRS) monitoring is a new challenge for clinicians who deal with early detection of dangerous hypoperfusion in the brain, as well as in splanchnic and renal districts in critically ill preterm infants. Previous studies performed on infants and children with congenital heart disease, demonstrated the efficacy of this non-invasive method in managing hypoperfusive states pre, post and during cardiac surgery. Its use has improved post surgery outcome. NIRS monitoring has been used also to assess therapeutic intervention utility. Early identification of silent hypoperfusion has made NIRS use in preterm infants very interesting for neonatologists, especially where other techniques have failed. In this work, literature on this topic has been carefully examined, particularly the "two site NIRS" use in preterm infants, to evaluate how regional splanchnic oxygen saturation changes, both in physiological events, such as enteral feeding and in hemodynamic disorders, that occur in patients with significant patent ductus and in hypoperfusive states that lead to necrotizing enterocolitis.

Red blood cell transfusion-related necrotizing enterocolitis in very-low-birthweight infants: a near-infrared spectroscopy investigation

BACKGROUND

Recent evidence suggests that antecedent red blood cell (RBC) transfusions increase the risk for necrotizing enterocolitis (NEC), the most common gastrointestinal emergency encountered by very-low-birthweight (VLBW) infants. The underlying mechanism for this association is unknown. Altered oxygenation of the mesenteric vasculature during RBC transfusion has been hypothesized to contribute to NEC development and was investigated in this study.

STUDY DESIGN AND METHODS

Oxygenation patterns among four VLBW infants who developed transfusion-related NEC (TR-NEC) were compared to four VLBW infants with similar gestational age who were transfused but did not develop NEC (non-NEC). Cerebral and mesenteric patterns were recorded before, during, and 48 hours after RBC transfusion using near-infrared spectroscopy (NIRS) technology. Percentage change from mean baseline regional oxygen saturation values and cerebrosplanchnic oxygenation ratios were analyzed.

RESULTS

All TR-NEC infants (24-29 weeks' gestation; 705-1080 g) demonstrated greater variation in mesenteric oxygenation patterns surrounding transfusions than non-NEC infants (27.6-30 weeks' gestation; 980-1210 g). TR-NEC infants received larger mean volumes of total blood (27.75 ± 8.77 mL/kg) than non-NEC infants (15.25 ± 0.5 mL/kg).

CONCLUSION

Wide fluctuation and decreases in mesenteric oxygenation patterns are more pronounced in TR-NEC infants, especially before TR-NEC onset, compared to non-NEC infants. Greater total volume of infused blood was associated with TR-NEC in preterm infants. Using NIRS, larger prospective studies are needed to further evaluate potential risk factors for NEC in this high-risk population.

Newer monitoring techniques to determine the risk of necrotizing enterocolitis

Necrotizing enterocolitis affects up to 10% of neonates who are born weighing less than 1500 g. It has a high rate of morbidity and mortality, and predicting infants who will be affected has so far been unsuccessful. In this article, a number of new methods are discussed from the literature to determine if any currently available techniques may allow for the identification of patients who are at increased risk for developing this potentially lethal disease.

Cerebral and somatic rSO2 in sick preterm infants

Near infrared spectroscopy (NIRS) measures the regional tissue oxygen saturation (rSO2) of various organs and provides a reflection of the balance between tissue oxygen supply and demand. Oxymetry assessed via NIRS has been proposed as a 'standard of care' and today it is already widely used in the NICU. This approach allows detection of any acute change in cerebral haemodynamics and continuous monitoring of cerebral and somatic oxygenation. This work describes three clinical cases of preterm VLBW infants which showed special points of interest during both cerebral and somatic NIRS monitoring.

Does treatment of patent ductus arteriosus with cyclooxygenase inhibitors affect neonatal regional tissue oxygenation?

The effect of patent ductus arteriosus (PDA) treatment with cyclooxygenase (COX) inhibitors (indomethacin [INDO] and ibuprofen [IBU]) on regional oxygenation requires further clarification. The authors hypothesized that both INDO and IBU reduce regional tissue oxygenation in preterm neonates with PDA but that the risk is not uniform for different tissues and other factors may contribute. Regional cerebral (rSO(2-C)), renal (rSO(2-R)), and mesenteric (rSO(2-M)) tissue oxygenation measured by near-infrared spectroscopy and peripheral arterial oxygen saturation measured by pulse oximetry were recorded simultaneously before, during, and after treatment with the first dose of INDO or IBU in very preterm-born infants with PDA. Tissue-specific fractional oxygen extraction (FOE) was calculated using the rSO(2-C), rSO(2-R), rSO(2-M), and corresponding SpO(2) measurements. The findings showed a significant reduction in rSO(2-C), rSO(2-R), and rSO(2-M) and an increase in regional FOE after treatment with COX inhibitors in approximately one third of the 38 enrolled infants, which were associated with increased baseline regional tissue oxygen saturation (p < 0.01). However, the infants with posttreatment reduction of tissue oxygenation had significantly lower baseline rSO(2-C) (66.7 ± 8.1 vs 69.7 ± 8.1 %), rSO(2-R) (55.2 ± 10.8 vs 62.7 ± 11.8 %) and especially rSO(2-M) (37.8 ± 11.4 vs 46.7 ± 16.0 %) than the neonates with unchanged or increased tissue oxygenation. The two groups did not differ in terms of the risk for posttreatment reduction in regional tissue oxygenation with respect to either INDO or IBU treatment and their respective blood levels. Treatment of PDA with either INDO or IBU is associated with a 30-40 % risk for a reduction in regional tissue oxygenation, which is more pronounced in mesenteric tissue than in cerebral or renal tissue. Despite the inconsistency, reduction of regional tissue oxygenation in preterm infants with PDA is more likely associated with the administration of INDO than with the administration of IBU.

Episodes of apnea, desaturation and bradycardia and the development of necrotizing enterocolitis in preterm infants: a case-control study

OBJECTIVE

To investigate for any association between episodes of apnea, desaturation and bradycardia and necrotizing enterocolitis (NEC).

METHODS

Case-control study in infants of gestational age < 30 weeks. For each NEC case we selected two controls. During the period from 2001 to 2007, data were extracted from the nurse's notes of the patient's medical records. A p < 0.05 was statistically significant.

RESULTS

A total of 38 out of 394 infants had NEC (9.6%). There were no significant differences in baseline characteristics between the 2 groups, except for a lower proportion of infants who were receiving breast milk in the NEC group (p = 0.02). There was no difference in the overall number of apneas & bradycardias or severe episodes of desaturation & bradycardia between the 2 groups.

CONCLUSION

No association between episodes of apnea, severe desaturations or bradycardia and development of NEC was observed in this preterm population.

Understanding near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a noninvasive technique that monitors regional tissue oxygenation reflecting perfusion status. Near-infrared spectroscopy has the ability to continuously and simultaneously monitor tissue perfusion in different organ systems at the bedside without interrupting routine care. Research has demonstrated its benefit in monitoring cerebral, intestinal, and renal perfusion to detect potential ischemic episodes. Near-infrared spectroscopy can augment current physiologic monitoring to increase awareness of abnormal perfusion status in the preterm population and potentially reduce risks associated with many diseases that may lead to ischemic injury. This article provides an overview describing NIRS technology and function, its current use in neonatology, and pertinent research findings illustrating its benefit in the neonatal population. Near-infrared spectroscopy may evolve into an important diagnostic and prognostic tool for neonatal treatment and outcome.

Regional tissue oxygenation in preterm born infants in association with echocardiographically significant patent ductus arteriosus

OBJECTIVE

To analyze the levels of regional tissue oxygenation in preterm infants in association with echocardiographically significant patent ductus arteriosus (PDA).

STUDY DESIGN

Preterm infants with gestational age less than 32 week were enrolled before the first dose of the pharmacological treatment for the PDA. Non-invasive near-infrared spectroscopy (NIRS) technology was utilized to measure cerebral (rSO(2)-C), renal (rSO(2)-R) and mesenteric (rSO(2-M)) tissue oxygenation for approximately 60 min. Regional fractional oxygen extraction (FOE) was calculated using simultaneously measured arterial saturation (SaO(2)). We analyzed regional tissue oxygenation and oxygen extraction, hemodynamic parameters, and demographic and clinical information in association with the size of the PDA (moderate vs large).

RESULT

Among the 38 enrolled infants, the majority were diagnosed with a large (63.2%, n=24) and the rest with a moderate-sized PDA. Infants with large and moderate PDA were comparable in terms of gestational age, study age and weight, mode of delivery and hemodynamic parameters. A significantly higher proportion of infants with a moderate PDA were mechanically ventilated as compared with those with a large PDA. We found no significant differences in the rSO(2)-C and rSO(2)-R, irrespective of the type of respiratory support. However, in infants with a large PDA on continuous nasal positive airway pressure (NCPAP), the rSO(2)-M was lower and mesenteric FOE was higher than that in mechanically ventilated neonates with a large PDA, and in those with moderate PDA irrespective of the type of respiratory support.

CONCLUSION

The PDA size did not affect cerebral and renal tissue oxygenation, but the mesenteric tissue oxygenation was decreased in infants with a large PDA on NCPAP.