Temperature, hematocrit, pH, and glucose 4-way ANOVA of cytochrome C oxidase redox status during systemic cold circulatory arrest in swine.

UNLABELLED: 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 micromol L(-1) min(-1), and, the corresponding mean magnitude of change was -1.23 +/- 0.57 micromol 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.

Brain, spine, and muscle cytochrome Cu-A redox patterns of change during hypothermic circulatory arrest in swine.

Past near infrared spectroscopy (NIRS) studies have reported different changes in cytochrome C oxidase (Cyt) redox status during similar interventions that cause tissue ischaemia. We investigated whether there were distinctive differences when NIRS signals were obtained simultaneously from different tissues during total circulatory arrest. Forty-two healthy 10 kg commercial swine (Sus scrofa) on cardiopulmonary bypass, each underwent 2 to 8 sequential periods of hypothermic circulatory arrest for 7.5 min. Prior to each arrest, key physiologic variables were adjusted to 1 of 81 combinations of high, normal, or low levels of core temperature, hematocrit, pH, and serum glucose. Each combination was repeated at least twice. Simultaneous NIRS monitoring yielded 202 brain, 191 spine, and 199 muscle Cyt data sets, which were then classified into 13 distinctive patterns of change. The data sets always differed between tissues in the same arrest trial and subject. Typically, brain Cyt rapidly became more reduced at the start of arrest and changed little thereafter, muscle Cyt behaved comparably to brain Cyt but continued to become reduced throughout the arrest, and spine Cyt either did not change status or gradually became more reduced over the course of arrest. The spine pattern's mean rate of change was 12 times slower than those of the brain or muscle. The Cyt patterns of change were classified into 13 groups which were significantly related to core temperature in the brain and spine, and hematocrit in muscle. The respiratory response in mitochondria during systemic circulatory arrest differs between brain, spine and muscle tissues in the same subject.

Solid breast masses diagnosed as fibroadenoma at fine-needle aspiration biopsy: acceptable rates of growth at long-term follow-up.

PURPOSE: To determine what growth rate is acceptable before recommending histologic diagnosis of solid breast lesions diagnosed as fibroadenoma at fine-needle aspiration biopsy (FNAB). MATERIALS AND METHODS: For 1,070 consecutive patients with breast lesions diagnosed as fibroadenoma at FNAB, three measurements of each mass were performed at the initial visit when FNAB was performed and at each follow-up ultrasonographic examination. Changes in volumes were calculated. At one or more visits, 194 masses showed an increase in volume. Nonfibroadenomas were excluded, and the data were used for comparison. Percentiles (90th and 95th) for percentage change in volume per month were used to determine acceptable changes in dimensions (specifically, greatest anteroposterior, parallel-to-skin, and perpendicular-to-skin dimensions). RESULTS: There were 567 interval measurements of 179 masses in 173 patients younger than 50 years and 50 measurements of 15 masses in 14 patients 50 years or older at the time of FNAB. The 95th percentile for percentage change in volume per month was approximately 16% for patients younger than 50 years; the 90th percentile was approximately 13% for patients 50 years or older. The 95th percentile mean change in dimension in a 6-month interval for those younger than 50 years was 20%; the 90th percentile change for those 50 years or older was also 20%. All excised masses with slower growth proved benign at histologic examination. CONCLUSION: Solid breast masses diagnosed as fibroadenomas at FNAB may be safely followed up if volume growth rate is less than 16% per month in those younger than 50 years and less than 13% per month in those 50 years or older. Acceptable mean change in dimension for a 6-month interval is 20% for all ages.

Near infrared spectroscopy for intraoperative monitoring of the spinal cord.

STUDY DESIGN: Animal model study of three healthy commercial pigs was conducted. OBJECTIVE: To determine whether near infrared spectroscopic monitoring of the spinal cord is feasible, and whether changes in near infrared spectroscopy correlate with changes in blood flow to the cord or operative maneuvers. SUMMARY OF BACKGROUND DATA: Near infrared spectroscopy is a noninvasive continuous monitoring tool capable of measuring absolute changes in the concentration of three chromophores: oxygenated hemoglobin, deoxygenated hemoglobin, and cytochrome aa3, the terminal enzyme in the electron transfer chain and a measure of cellular energy equilibrium. Near infrared spectroscopy has been used to monitor the brain intraoperatively in multiple circumstances. The authors hypothesized that near infrared spectroscopy could be used to monitor the spinal cord's cellular energy equilibrium during spinal surgery (i.e., that vascular compromise could be identified before irreversible damage occurred). METHODS: The posterior elements of the spine were exposed, and near infrared spectroscopy optodes (fiberoptic bundles) were sutured to either the lamina or the spinous processes of T9, T10, or both and directed toward the spinal cord. Interventions included manipulation of oxygen saturation and distraction of the T9-T10 disc space. RESULTS: With reduced oxygen delivery (lower arterial oxygen saturation and blood flow), oxygenated hemoglobin concentration decreased and deoxygenated hemoglobin concentration increased. With distraction, blood volume (oxygenated hemoglobin plus deoxygenated hemoglobin) decreased, and cytochrome aa3 became more oxidized. Changes were apparent within 1 second of the intervention beginning, and recovery to the baseline of near infrared spectroscopy occurred with relief of each intervention. CONCLUSIONS: This near infrared spectroscopy technique monitors changes in oxygenation of the spinal cord, and therefore appears capable of intraoperative warning about impending vascular compromise of the spinal cord.

Comparison of two spatially resolved NIRS oxygenation indices.

UNLABELLED: 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 NIRO 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.