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Abstract Various investigators using near infrared spectroscopy (NIRS) have reported differing patterns of cytochrome C oxidase (cytochrome a,a3) redox status in similar brain oxygenation studies. We investigated whether distinctive differences could be due to combinations of variations in temperature, hematocrit, pH, and glucose. Methods: Thirty-six healthy 10 kg commercial juvenile swine on cardiopulmonary bypass underwent 2–8 sequential periods of circulatory arrest. Prior to each arrest, key physiological variables were adjusted to match a random selection of one of 81 combinations of high, normal, or low levels of hypothermia, hematocrit, pH, and serum glucose. In the course of the study, the combinations were repeated twice to yield 162 NIRS data sets. Results: The mean rate of change in net oxidized minus reduced cytochrome a,a3 redox status in the brain following 7.5 min of ischemia was 0.49 ± 0.26 µmol L-1 min-1, and, the corresponding mean magnitude of change was -1.23 ± 0.57 µmol L-1. The rate of change was influenced by temperature but not by hematocrit, pH, or glucose, either singly or in combination. Conclusion: The respiratory response in mitochondria during systemic circulatory arrest is significantly influenced by temperature.

We compared the percentage haemoglobin oxygenation indices from two near infrared spectrophotometers (NIRS) to determine whether the devices reported similar changes in response to induced changes in oxygenation. Methods.24 healthy juvenile swine undergoing cardiac bypass surgery had INVOS 5100 and NIRO-300 sensors applied to the brow. Induced events included circulatory arrest, altered blood flow rate, core cooling, and re-warming. Results.The average data collection was 4 hours 36 minutes and had an r= 0.82 mean correlation between the INVOS and NIRO. The total resting baseline collection from all trials (8,590 pairs) had a correlation of r= 0.62. The average relationship between the INVOS and NIRO was non-linear: an INVOS regional oxygen saturation index (rSO2) of 0% was equivalent to a NIRO tissue oxygenation index (TOI) of 36.2%; values were equal at 56.8%; and an (rSO2) of 100% was equivalent to a TOI 85.9%. There was good or excellent agreement (r> 0.5) between the (rSO2) and TOI patterns of change during induced events in 96% of trials. The INVOS and N IRO were most closely correlated when an attenuation filter was used to obtain identical emitter/detector separations. Conclusions.There was close agreement between the INVOS 5100 and NIRO-300 in response to major physiological change, although absolute values of (rSO2) and TOI were not identical. There was less agreement during baseline measurements or minimal physiologic change.

Purpose:Neurologic complications occur following cardiopulmonary bypass surgery. We conducted a randomized, controlled, single-blind study to determine the effect of propofol on the redox status of cytaa3, and to evaluate its potential for decreasing neurologic complications.

Near infrared spectroscopy (NIRS) clinical trials conducted over a seven year period have identified instrument engineering problems related to fiber optic failure, electromagnetic interference, chromophore algorithms, and computational software. These problems have caused confusion amongst clinicians at the bedside, rejection of large volumes of data, repeated reanalysis of data, and a significant diversion of project resources away from clinical studies and into engineering solutions. This article summarizes previously published studies and presents new data which, together, emphasize the need for improvements in NIRS technology. Instrument designers need to be aware of the need for these improvements if NIRS is to serve clinicians better during research designed to rationally define clinical management protocols. © 1998 Society of Photo-Optical Instrumentation Engineers.

Conflicting patterns of change in cytochrome c oxidase (Cyt a,a₃) redox status have been obtained between different near-infrared spectrophotometers when making measurements during tissue ischaemia. This study identifies possible sources of error that could be the cause of the discrepancy. A single set of optical density data was repeatedly analysed using each of the absorption spectra from 13 publications. In addition, changes in Cyt a,a₃ redox status were calculated from the data set using three numerical methods, five computer software routines, eight displacements in wavelength, and ten incremental changes in the value of absorption or concentration coefficients. All Cyt a,a₃ absorption spectra resulted in algorithms yielding similar patterns of change, regardless of the numerical method or computer process employed (0.9996 average r², coefficient of correlation). However, a significantly different pattern of change in Cyt a,a₃ redox status, resembling that reported by Piantadosi [Piantadosi CA (1993) Methods Toxicol. 2:107-126], was obtained when either the wavelengths, and/or the absorption values were altered to simulate erroneous values. This implies that all of the present algorithms are valid (including those of Piantadosi), but that microchip encoding errors may exist in the instrument used by Piantadosi.

This study measured the distances between the tips of the transverse processes of adjacent lumbar vertebrae L1L4 in the same subjects after 1 day of normal activities and again the next morning.

Abstract: Conflicting patterns of change in cytochrome c oxidase (Cyt a,a3) redox status have been obtained between different near-infrared spectrophotometers when making measurements during tissue ischaemia. This study identifies possible sources of error that could be the cause of the discrepancy. A single set of optical density data was repeatedly analysed using each of the absorption spectra from 13 publications. In addition, changes in Cyt a,a3 redox status were calculated from the data set using three numerical methods, five computer software routines, eight displacements in wavelength, and ten incremental changes in the value of absorption or concentration coefficients. All Cyt a,a3 absorption spectra resulted in algorithms yielding similar patterns of change, regardless of the numerical method or computer process employed (0.9996 averager 2, coefficient of correlation). However, a significantly different pattern of change in Cyt a,a3 redox status, resembling that reported by Piantadosi [Piantadosi CA (1993) Methods Toxicol. 2:107–126], was obtained when either the wavelengths, and/or the absorption values were altered to simulate erroneous values. This implies that all of the present algorithms are valid (including those of Piantadosi), but that microchip encoding errors may exist in the instrument used by Piantadosi.

This study was done to produce enhanced fetal biometry charts and graphs presenting percentile values as a function of fetal age. The relationships between the ultrasound measurements of 10 fetal parameters and menstrual age were determined by a cross-sectional study. Data were obtained from 508 to 790 fetuses. Anatomic structures were scanned and measured 3 times during 1 routine sonographic examination. The study group consisted of 1,396 Caucasian women who had normal singleton fetuses with confirmation of menstrual dates by sonography before 14 weeks and for whom complete pregnancy outcome information was available. For each of the 10 parameters, percentile curves were derived for the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles. Ready-to-use fetal measurement charts and graphs are presented in a format giving the percentile values as a function of fetal age. There were no significant differences between male and female fetuses. These fetal biometry charts and graphs, obtained from a North American Caucasian population, enhance previously published data. © 1998 John Wiley & Sons, Inc. J Clin Ultrasound 26:433–453, 1998.

Introduction:Family-oriented communication with parents by transport teams eases the stress associated with transferring children to tertiary care. This study was conducted to determine the duration of family-oriented visits and whether the visit contributed significant cost to the mission. Method:Data collection was prospective and double-blind; questions were incorporated into another study. Subjects were infants or children requiring assisted ventilation and air transport to tertiary care. Time from completion of stabilization to departure and reasons for any delay were recorded. Cost of contact time longer than 20 minutes (total acceptable time for family visit and transfer to vehicle) was calculated at paramedic overtime at $0.82/minute and aircraft wait time at $200/hour if incurred. Results:Forty-six patients were enrolled. In 16 cases (35%), time between completing stabilization and hospital departure exceeded 20 minutes, with “family visit” listed as the explanation. Nine of these visits incurred overtime, and two incurred aircraft wait costs. Total costs for providing communication visits more than 10 minutes long were $607 or approximately $13 per patient. Conclusion:The costs for visit time longer than 10 minutes are small compared with the documented benefits of family-oriented communication. However, transport personnel must be mindful of the potential to incur additional cost through overtime, aircraft wait time, or pilot replacement.

Purpose: Near infrared spectroscopy (NIRS) monitors absolute changes in concentration of chromophores from an unquantified baseline. A change in oxygenation is required to obtain information. Clinically, knowing initial chromophore concentration is desirable. We sought absolute initial concentrations by combining NIRS measurements with simultaneous Eppendorf histograph measurement (absolute values of tissue partial pressure of oxygen (pO2)). Methods: There were 22 trials on 9 occasions in 2 adult volunteers. Following local anaesthetic, the histograph probe was inserted into the forearm muscle and NIRS optodes applied. A sphygmomanometer cuff was inflated over the upper arm to produce ischaemia and hypoxia. Change in pO2 was determined as a percentage of the initial pO2. Change in HbO2 was measured, and the initial HbO2 calculated by assuming the percentage change in HbO2 equaled the percentage change in pO2. Results: Mean percentage change in pO2 was 20.7 ± 9.6. Mean change in HbO2 was 22.4 ± 3.4 µmol/l(tissue). Calculated initial HbO2 was 146.4 ± 108.7 µmol/l(tissue), range 51 to 508 µmol/l(tissue). Correlation (r2) between pO2 and HbO2 was 0.97 ± 0.03. Conclusion: Although changes in pO2 and HbO2 were highly correlated, calculation of initial absolute concentration of HbO2 was not achieved by this method. A reliable method of obtaining absolute concentrations of HbO2in vivo remains to be found.

During cardiac surgery, bypass pumps rely on pressure monitors to evaluate flow. We studied whether it would be possible to optimize pump flow by monitoring changes in cerebral cytochrome a,a3 using NIRS to maintain cyt redox status at its pre-bypass level. Method: 18 healthy 7–45 kg swine were placed on bypass for repeated cycles of cooling and re-warming from 36 to 15 to 36°C in 3°C steps. Between each cycle, the swine's bypass pump blood flow rate was adjusted to restore cytochrome redox status to its pre-bypass value. Results: In all swine trials, the number of pump flow alterations imposed by NIRS monitoring ranged from 0 to 42, the average being 14 per trial. The best trial had 22 pump flow adjustments during which the range of cytochrome redox status change was 0.50±0.06 µmol?l–1. The average trial had a range of cytochrome redox status change of 1.50±0.22 µmol?l–1. Conclusion: NIRS-driven alterations in pump flow rate to maintain pre-bypass cytochrome redox status can be achieved successfully in the animal model.

Near infrared spectroscopy (NIRS) monitors changes in oxygenated haemoglobin (HbO2), and redox status of cytochromeaa3 (cyt) continuously and non-invasively in living tissue. We present examples where clinically relevant changes in HbO2 and/or cyt were detected in real time, allowing intervention to avert potentially harmful hypoxic-ischaemic damage to the brain and/or spinal cord. Brain monitoring: In children undergoing surgery on cardiopulmonary bypass, observations include that: atrial fibrillation (cardiac arrhythmia) lowered cerebral HbO2 concentration; concealed haemorrhage decreased cerebral HbO2 concentration; inadequate level of anaesthetic resulted in spikes of changes in volume with interventions such as suturing; circulatory arrest reduced brain HbO2 and cyt redox status; and bypass pump problems compromised cerebral blood flow. Spinal cord monitoring: In the experimental animal, we observed that NIRS detected ischaemic change immediately following aortic compression, spinal column distraction (instrumentation to separate the vertebrae), and hypoxia. In an infant requiring release of a congenitally tethered spinal cord, we observed that traction on the spinal cord of the infant resulted in decreased total haemoglobin concentration. Summary: NIRS brain monitoring probably represents the “standard of care” during cardiac surgery because adverse events can be detected and quantified. Similarly, spinal cord monitoring could reduce ischaemic spinal cord damage in spinal cord surgery and aortic aneurysm repair.