Evolution of Early Cerebral NIRS in Hypoxic Ischaemic Encephalopathy

Analgesia and sedation strategies in neonates undergoing whole-body therapeutic hypothermia: A scoping review

BACKGROUND

Therapeutic hypothermia (TH) is a widely practiced neuroprotective strategy for neonates with hypoxic-ischemic encephalopathy. Induced hypothermia is associated with shivering, cold pain, agitation, and distress.

OBJECTIVE

This scoping review determines the breadth of research undertaken for pain and stress management in neonates undergoing hypothermia therapy, the pharmacokinetics of analgesic and sedative medications during hypothermia and the effect of such medication on short- and long-term neurological outcomes.

METHODS

We searched the following online databases namely, (i) MEDLINE, (ii) Web of Science, (iii) Cochrane Library, (iv) Scopus, (v) CINAHL, and (vi) EMBASE to identify published original articles between January 2005 and December 2022. We included only English full-text articles on neonates treated with TH and reported the sedation/analgesia strategy used. We excluded articles that reported TH on transport or extracorporeal membrane oxygenation, did not report the intervention strategies for sedation/analgesia, and reported hypoxic-ischemic encephalopathy in which hypothermia was not applied.

RESULTS

The eligible publications (n = 97) included cohort studies (n = 72), non-randomized experimental studies (n = 2), pharmacokinetic studies (n = 4), dose escalation feasibility trial (n = 1), cross-sectional surveys (n = 5), and randomized control trials (n = 13). Neonatal Pain, Agitation, and Sedation Scale (NPASS) is the most frequently used pain assessment tool in this cohort. The most frequently used pharmacological agents are opioids (Morphine, Fentanyl), benzodiazepine (Midazolam) and Alpha2 agonists (Dexmedetomidine). The proportion of neonates receiving routine sedation-analgesia during TH is center-specific and varies from 40-100% worldwide. TH alters most drugs' metabolic rate and clearance, except for Midazolam. Dexmedetomidine has additional benefits of thermal tolerance, neuroprotection, faster recovery, and less likelihood of seizures. There is a wide inter-individual variability in serum drug levels due to the impact of temperature, end-organ dysfunction, postnatal age, and body weight on drug metabolism.

CONCLUSIONS

No multidimensional pain scale has been tested for reliability and construct validity in hypothermic encephalopathic neonates. There is an increasing trend towards using routine sedation/analgesia during TH worldwide. Wide variability in the type of medication used, administration (bolus versus infusion), and dose ranges used emphasizes the urgent need for standardized practice recommendations and guidelines. There is insufficient data on the long-term neurological outcomes of exposure to these medications, adjusted for underlying brain injury and severity of encephalopathy. Future studies will need to develop framework tools to enable precise control of sedation/analgesia drug exposure customized to individual patient needs.

The Use of Cerebral Near-Infrared Spectroscopy in Neonatal Hypoxic-Ischemic Encephalopathy: A Systematic Review of the Literature

BACKGROUND

Cerebral near-infrared spectroscopy (cNIRS) is a noninvasive technology used to trend cerebral perfusion at the bedside. cNIRS has potential as a valuable tool in the evaluation of infants with suspected hypoxic-ischemic encephalopathy (HIE). Trending cerebral perfusion with cNIRS can provide information regarding cerebral metabolism as HIE is evolving, which may offer insight into the extent of brain injury.

PURPOSE

The purpose of this systematic review is to investigate the use of cNIRS as a neurocritical tool in the management of neonatal HIE by evaluating its ability to detect acute neurological compromise, including acute brain injury and seizure activity, as well as its potential to identify infants at high risk for long-term neurodevelopmental impairment.

METHODS

A literature search was conducted using PubMed, CINAHL, and Web of Science databases to review articles investigating cNIRS technology in the acute management of HIE.

RESULTS

Eight studies were identified and included in this systematic review. Correlations were observed between cNIRS trends and neurological outcomes as later detected by MRI. cNIRS has potential as a bedside neuromonitoring tool in the management of HIE to detect infants at high risk for brain injury.

IMPLICATIONS FOR PRACTICE

Existing research supports the value of trending cNIRS in HIE management. Documented normal cNIRS values for both term and preterm infants in the first few days of life is approximately 60% to 80%. A steadily increasing cNIRS reading above an infant's baseline and a value of more than 90% should prompt further evaluation and concern for significant neurological injury.

Comparison of the SenSmart™ and the INVOS™ neonatal cerebral near-infrared spectrometry devices

Objectives

To determine the correlation and agreement between the SenSmart™ and the INVOS™ devices of neonatal cerebral regional oxygen saturation (CrSO2) measurements using neonatal sensors. The secondary objective was to develop a regression model that predicts CrSO2-INVOS values using CrSO2-SenSmart indices and determine whether the values between the devices are interchangeable.

Methods

A prospective, cross-sectional study was conducted in infants during the first 4 weeks of life. Simultaneous, bilateral CrSO2 was measured using the SenSmart™X100 (CrSO2-SenSmart) or INVOS™ 5100C (CrSO2-INVOS) device in each frontoparietal area for 2 h. Five-minute CrSO2 values were extracted for analysis.

Results

Thirty infants were recruited with 720 pairwise measurements and 26 (84%) were evaluated in the first week of life. Mean gestational age of the preterm and term infants was [30.9 ± 2.8 (n = 14) and 38.8 ± 1.1 (n = 16)] weeks, respectively. Overall CrSO2- was 77.08 ± 9.70% and 71.45 ± 12.74% for the SenSmart and INVOS, respectively (p < 0.001). The correlation coefficient (r) between the CrSO2-SenSmart and INVOS was 0.20 (p < 0.001). The mean difference between the CrSO2-SenSmart and INVOS was 5.63 ± 13.87% with -21.6% to 32.8% limits of agreement. The r and mean difference was 0.39 (p < 0.001) and 8.87 ± 12.58% in preterm infants, and 0.06 (p = 0.27) and 2.79 ± 14.34 in term infants.

Conclusion

The CrSO2-SenSmart tended to read higher than the CrSO2-INVOS device. There was no correlation between the CrSO2-SenSmart and the CrSO2-INVOS in term infants and it was weak in preterms. Due to imprecise agreement, the CrSO2-SenSmart values are not interchangeable with those of the CrSO2-INVOS.

Optimal neuromonitoring techniques in neonates with hypoxic ischemic encephalopathy

Neonates with hypoxic ischemic encephalopathy (HIE) are at significant risk for adverse outcomes including death and neurodevelopmental impairment. Neuromonitoring provides critical diagnostic and prognostic information for these infants. Modalities providing continuous monitoring include continuous electroencephalography (cEEG), amplitude-integrated electroencephalography (aEEG), near-infrared spectroscopy (NIRS), and heart rate variability. Serial bedside neuromonitoring techniques include cranial ultrasound and somatic and visual evoked potentials but may be limited by discrete time points of assessment. EEG, aEEG, and NIRS provide distinct and complementary information about cerebral function and oxygen utilization. Integrated use of these neuromonitoring modalities in addition to other potential techniques such as heart rate variability may best predict imaging outcomes and longer-term neurodevelopment. This review examines available bedside neuromonitoring techniques for the neonate with HIE in the context of therapeutic hypothermia.