Transcutaneous monitoring in the newborn infant

Neonatal encephalopathy occurs in 2 to 5/1000 live births and is principally related to hypoxic-ischemic injury to the newborn brain in the immediate peripartum period. In the last decade, there have been significant advances in neuroprotection that have been successful in reducing the risk of death and disability in infants who have suffered from a potential hypoxic-ischemic cerebral injury. The advent of therapeutic hypothermia has led to a major focus on the early clinical recognition of infants that may benefit from such therapies. In addition, optimal recognition and therapeutic targeting of neonatal seizures, with other neuroprotective approaches, have been emphasized. This chapter will summarize the clinical presentation, neuropathological correlates, neurodiagnostic evaluation, prognosis, and management of this condition.

Encephalopathy of prematurity (EOP) is a histologically defined condition common in preterm infants characterized by cerebral white matter injury/periventricular leukomalacia with a variety of associated neuronal/axonal deficits. The fetal/maternal and neonatal conditions leading to EOP are those typically associated with cerebral ischemia and systemic infection/inflammation. Recognizing the neurologic correlates of EOP for infants in the NICU is challenging because the clinical manifestations are not particularly distinctive. As a result, the diagnosis of EOP relies heavily on EEG and neuroimaging studies, mainly head ultrasound and EEG. Infants with EOP have a high incidence of chronic neurodevelopmental impairment in a variety of areas—motor coordination, visual function, cognitive function, language ability, socialization, and behavior. These impairments can be predicted, to some degree, with neuroimaging findings and their known neuropathologic correlates. Clinical management of preterm infants during the neonatal period may influence outcome, and relevant elements include administration of steroids prior to delivery as well as management of oxygen levels, carbon dioxide levels, blood pressure, glucose levels, seizures, and patent ductus arteriosus. Neuroprotective strategies that might mitigate the effects of EOP are currently under evaluation. Among these are erythropoietins, epidermal growth factor, insulin-like growth factor, and stem cell administration. Finally, the environment of the NICU itself is important for optimizing neurodevelopmental outcomes. Factors such as auditory exposure, visual exposure, and human contact should be taken into account in NICU management.

To continuously measure arterial blood gases (ABGs), to calculate the percentage of anticipated changes over time, and to develop recommendations for sampling frequencies of arterial blood gases in patients undergoing thoracoscopic surgery.

Prospective, observational clinical trial.

University hospital.

43 consecutive elective patients undergoing thoracoscopic surgery with one-lung ventilation.

A Paratrend 7 probe for continuous arterial partial pressure of oxygen and arterial partial pressure of carbon dioxide measurement was introduced through a radial artery cannula in the awake patient before surgery. Data were collected throughout the procedure until patients left the operating room. Afterward, time courses of arterial blood gas values were transformed into frequency space by fast Fourier transform analysis, and the expected deviations in arterial blood gases were calculated over time.

Forty-three consecutive patients undergoing thoracoscopic surgery were included, and arterial blood gas values were measured during a total of 141.5 h. Critical arterial partial pressure of oxygen values ≤60 mmHg were recorded in 16 patients for a total of 4.5 hours. Fourier amplitude spectra showed comparable characteristics of arterial partial pressure of oxygen and arterial partial pressure of carbon dioxide time courses in all patients. It takes only 5, 10, or 20 minutes for the arterial partial pressure of oxygen to change 10%, 20%, or 40%, respectively (95% confidence).

Current standards to monitor arterial blood gases are not sufficient to detect and prevent hypoxemic events during thoracoscopic surgery with one-lung ventilation. Intermittent arterial blood gas analyses must be performed more frequently, up to every 10 minutes, to detect changes of 20% in arterial partial pressure of oxygen.

This review focuses on the development, current techniques, and clinical use of continuous intravascular blood gas monitoring (CIBM) devices in anaesthesia and intensive care. The operating principles, range of application, performance, limitations, costs, and impact on patient treatment and outcome, are discussed. Studies of early and currently available CIBM devices were analysed. At present, the Paratrend 7+^® (PT7+^®) for adults and Neotrend™ (NT™) for newborns are the only commercially available CIBM systems. The PT7+^® contains three optical sensors to measure Po₂, Pco₂ and pH, as well as a thermocouple to measure temperature. The NT™ is a modification of the PT7+^® to continuously monitor Po₂, Pco₂, pH and temperature in newborns. Under laboratory conditions, good performance over a wide range of blood gas values was observed with the Paratrend 7^® (PT7^®). Performance in the clinical setting was not as satisfactory, especially for Po₂ values. However, the performance and accuracy of CIBM devices appear to be sufficient for clinical use and they are being used clinically in selected patient groups. Several factors affecting the performance of CIBM are considered.