Effects of hemoglobin concentration, skull thickness, and the area of the cerebrospinal fluid layer on near-infrared spectroscopy measurements.

BACKGROUND: Previous studies documented that near-infrared spectroscopy values were affected by factors related to optical path length, such as hemoglobin concentration, the differential path length factor, skull thickness (t-skull), and the area of the cerebrospinal fluid layer (a-CSFL). Lately, the NIRO-100 (Hamamatsu Photonics, Hamamatsu, Japan) has provided a tissue oxygen index (TOI) that theoretically is not supposed to be affected by optical path length. Therefore, the authors hypothesized that TOI is not influenced by the above-described individual factors. METHODS: Cardiac surgical or neurosurgical 103 patients (65 men and 39 women; aged 63 +/- 14 yr) were studied. TOI and regional cerebral oxygen saturation (rSO2) (INVOS 4100; Somanetics, Troy, MI) were measured sequentially on patients in a resting state. The t-skull and a-CSFL were calculated using computed tomographic image slices of the head corresponding with the position of near-infrared spectroscopy sensors. The effects of these two factors, hemoglobin concentration and mean arterial pressure, on TOI and rSO2 values were evaluated by linear regression analysis. RESULTS: Simple linear regression analysis showed that mean arterial pressure (r = 0.27, P = 0.008), t-skull (r = 0.22, P = 0.034), a-CSFL (0.26, P = 0.012), and hemoglobin concentration (r = 0.42, P < 0.0001) were significant determinants of rSO2. Multiple linear regression analysis showed that hemoglobin concentration (r = 0.34, P < 0.001), a-CSFL (r = -0.252, P = 0.012), and t-skull (r = 0.22, P = 0.037) were significant determinants of rSO2. On the other hand, simple and multiple linear regression analysis showed that there was no significant determinant of TOI. CONCLUSION: rSO2 values were affected by hemoglobin concentration, a-CSFL, and t-skull, but TOI values were not affected by individual factors.

Measurements of optical pathlength using phase-resolved spectroscopy in patients undergoing cardiopulmonary bypass.

BACKGROUND: Near infrared spectroscopy (NIRS) has been used during cardiac surgery to monitor cerebral oxygenation although the validity of this technique has yet to be established. Although optical pathlength included in the algorithm for calculating NIRS values is supposed to be constant, recent evidence has suggested that optical pathlength could be affected by acute hemodilution in animals. We conducted the present study to investigate whether optical pathlength changes during cardiopulmonary bypass (CPB), and whether these changes affect NIRS values in adult patients. METHODS: Nine patients undergoing elective cardiac surgery with CPB were enrolled in this study. Optical pathlength and cerebral NIRS values (oxyhemoglobin [DeltaO(2)Hb] and tissue oxygen index) were measured by phase-resolved spectroscopy and NIRO 100, respectively. Optical pathlength, hemoglobin concentration, and NIRS values were measured at the following points: 1) after the induction of anesthesia, 2) 10 min after the start of CPB, 3) 60 min after the start of CPB, and 4) 1 h after CPB. The associations between optical pathlength and other variables were analyzed by Pearson correlation coefficients and multiple regression analysis. RESULTS: Optical pathlength significantly increased starting at 27.7-30.8 cm at 10 min, and 31.3 cm at 60 min after the start of CPB (P < 0.0001). Hemoglobin concentrations significantly decreased (from 11.2 to 7.1 g/dL at 10 min and 7.7 g/dL at 60 min P < 0.0001). There was a significant correlation (r = 0.55, P < 0.001) between percentage changes in pathlength and hemoglobin concentration. Multiple regression analysis showed that optical pathlength was a significant determinant of DeltaO2Hb. CONCLUSION: The results indicate that optical pathlength can change during CPB and its changes may affect DeltaO2Hb.

Successful management of cesarean section in a patient with Romano-Ward syndrome using landiolol, a selective and short-acting beta1 receptor antagonist.

Romano-Ward (R-W) syndrome is an autosomal dominant hereditary disorder and is characterized by a prolonged QT interval on the electrocardiogram (ECG), syncope, and sudden death. We report here a case of cesarian section in a patient with R-W syndrome whose QT prolongation was successfully managed with landiolol, a selective beta1 receptor blocker. A 25-year-old woman with R-W syndrome was scheduled for cesarean section. In the operating room, the patient's ECG showed tachycardia (102 beats x min(-1)) and marked QT prolongation (QTc = 0.56 s). After spinal anesthesia, the patient's heart rate (HR) increased to 130 beats/min accompanied by a slight decrease in arterial blood pressure to 97/57 mmHg and the QTc was prolonged to 0.57 s. Landiolol was continuously infused at a rate of 0.04 mg.kg(-1) x min(-1) and the HR gradually decreased to 80-90 beats x min(-1) accompanied by the normalization of QTc to 0.48 s. We thought that the use of landiolol was more rational and was preferable to a nonselective beta receptor blocker for a term-pregnant woman because blockade of the beta2 receptor might cause uterine contraction. After the use of landiolol, intraoperative and postoperative courses in both the patient and the baby were uneventful.