Effect of posture and extracranial contamination on results of cerebral oximetry by near-infrared spectroscopy.

BACKGROUND: Near-infrared spectroscopy (NIRS)-based cerebral oximetry is a noninvasive technology used to estimate regional cerebral oxygen saturation (rSO2). Extracranial blood flow is known to substantially affect rSO2 values measured by most clinically available devices. Several studies have also reported that the Trendelenburg position and upright position have a larger effect on rSO2 measurements than the supine position. Therefore, we investigated the effect of these two positions (the Trendelenburg position versus the upright position) and extracranial contamination on rSO2 measurements obtained using two commercially available devices and one prototype device. METHODS: Twelve healthy volunteers were enrolled in the study. They each had three cerebral oximetry devices applied to their forehead (FORE-SIGHT ELITE™, CAS Medical Systems Inc., Branford, CT, USA; INVOS 5100c™, Medtronic, Minneapolis, MN, USA; and NIRO-TRS, Hamamatsu Photonics, Hamamatsu, Japan). A circumferential pneumatic head cuff was positioned proximal to the NIRS cerebral oximetry sensors. We measured rSO2, heart rate (HR), and blood pressure (BP) in six conditions (supine, Trendelenburg and upright positions, with and without scalp ischemia induced by head cuff inflation) every 5 min with each oximetry device. Total hemoglobin (tHb), which is associated with cerebral blood volume (CBV) as measured by positron emission tomography, was measured using the NIRO-TRS device to determine extracranial blood volume in each position. RESULTS: Measurements of rSO2 with all the devices were affected by extracranial contamination. The percentage of extracranial contamination was highest with INVOS 5100c™ in the upright position (INVOS, 21.3%; FORE-SIGHT, 14.3%; NIRO-TRS, 3.6%). Measurements of rSO2 obtained in the upright position were significantly lower than those obtained in the supine position, using INVOS-5100c™ and FORE-SIGHT ELITE™ (71 vs. 74% and 67 vs. 72%, respectively), but not using NIRO-TRS (62 vs. 64%). A significant decrease in tHb was observed after head cuff inflation in the supine and Trendelenburg positions (supine, 0.132-0.123 µmol/l; Trendelenburg, 0.133-0.125 µmol/l). CONCLUSIONS: Except when using NIRO-TRS, measurements of rSO2 in the forehead are significantly lower when measured in the upright position than in the supine position. All devices in this study were affected by extracranial contamination.

A Retrospective Examination of the Efficacy of Paravertebral Block for Patients Requiring Intraoperative High-Dose Unfractionated Heparin Administration During Thoracoabdominal Aortic Aneurysm Repair.

OBJECTIVE: Postoperative respiratory complications are serious and frequently observed among patients who undergo thoracoabdominal aortic aneurysm (TAAA) repair. Paravertebral block (PVB) can provide effective analgesia for relief of postoperative thoracotomy pain and may reduce respiratory complications. However, the impact of PVB on postoperative pain and respiratory function in patients who undergo TAAA repair requiring intraoperative high-dose heparin administration is unknown. This study examined the efficacy of PVB on postoperative pain and respiratory function after TAAA repairs. DESIGN: Retrospective, observational cohort study. SETTING: Single center in Japan. PARTICIPANTS: Fifty-eight consecutive patients who underwent TAAA repair from March 2013 to October 2014. INTERVENTIONS: Application of thoracic PVB. MEASUREMENT AND MAIN RESULTS: A total of 56 patients were analyzed. Two patients were excluded because 1 patient was dead within 24 hours after surgery and 1 patient was 9 years old. Patients with PVB were defined as group P (n = 17), and patients without PVB as group C (n = 39). There was no significant difference in baseline characteristics between the 2 groups. Both postoperative pain at rest and postoperative pain while coughing were assessed using a numeric rating scale (NRS); the incidence of reintubation and noninvasive positive-pressure ventilation (NPPV) also were compared between the 2 groups. The NRS score of postoperative pain at rest was significantly lower in group P (group P: Median 2, interquartile range 1 to 3; group C: Median 6, interquartile range 5 to 7; p = 0.000), and the NRS score of postoperative pain while coughing was significantly lower in group P (group P: Median 5, interquartile range 3.5 to 6.5; group C: Median 8, interquartile range 7 to 10; p = 0.000). Reintubation rate was significantly lower in group P (group P: 0%, group C: 23%, p = 0.045); the incidences of NPPV (group P: 12%, group C: 46%, p = 0.016) and postoperative pneumonia were significantly lower in group P (group P: 0%, group C: 28%, p = 0.024). CONCLUSIONS: PVB significantly reduced postoperative pain at rest and while coughing and significantly reduced the reintubation rate, the rate of NPPV use, and postoperative pneumonia without complications. PVB could be a safe and an effective analgesic method that reduces postoperative respiratory exacerbation in patients who undergo TAAA repair.

Inaccuracy of the FloTrac/Vigileo™ system in patients with low cardiac index.

OBJECTIVES: The goal of this study was to compare cardiac output derived from the FloTrac/Vigileo™ system (CO(FT)) with cardiac output measured by 3-dimensional transesophageal echocardiography (CO3D) in patients with severe heart failure undergoing cardiac resynchronization therapy. The impact of preoperative systemic vascular resistance index on the accuracy of the FloTrac/Vigileo™ system also was investigated. DESIGN: Prospective clinical study. SETTING: Cardiac surgery operating room of a single cardiovascular center. PARTICIPANTS: Forty-one patients undergoing elective cardiac resynchronization therapy lead implantation. INTERVENTIONS: CO3D as the reference method and CO(FT) were determined simultaneously after induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Linear regression analysis showed a poor correlation between CO3D and CO(FT) (R² = 0.16). Bland-Altman plots showed wide limits of agreement between CO3D and CO(FT.). Bias was 0.60 ± 0.63 L/min with a high percentage error of 58.2%. Subgroup analysis showed that the percentage error between CO3D and CO(FT) was 74.1% in patients with a cardiac index<2.2 L/min/m(2) and 17.2% in patients with a cardiac index ≥ 2.2 L/min/m(2). Systemic vascular resistance index was significantly higher in patients with a cardiac index<2.2 L/min/m(2) (3,037 ± 820 v 2,461 ± 878; p = 0.039). CONCLUSIONS: The FloTrac/Vigileo™ system is not accurate in patients with low cardiac output, especially those with a cardiac index<2.2 L/min/m(2). A high systemic vascular resistance index in patients with low cardiac index may contribute to this inaccuracy.

Anesthetic management of pregnant women with stroke.

Stroke during pregnancy is rare, but after occurring, most patients develop serious neurological conditions. Hemorrhagic stroke, including intracerebral hemorrhage and subarachnoid hemorrhage, often requires emergency surgical intervention. In addition to significant maternal physiological changes, the potential for fetal harm should be considered during anesthetic management of these patients. Whether cesarean section or neurosurgical intervention should be prioritized or performed simultaneously in pregnant women with stroke is an important issue. Whether the patients receive general or spinal and epidural anesthesia is another clinically significant issue. Finally neurosurgeons, anesthesiologists, and obstetricians should cooperate to manage pregnant women with stroke.

Clinical validity of cerebral oxygen saturation measured by time-resolved spectroscopy during carotid endarterectomy.

BACKGROUND: Near-infrared spectroscopy has been used clinically to continuously and noninvasively monitor cerebral oxygen saturation (ScO2). However, there is no gold standard for measuring absolute values of ScO2. Although time-resolved spectroscopy (TRS) is one of the most reliable algorithms that reliably calculate absolute values of ScO2, there are very few clinical studies available. To evaluate the clinical relevance of ScO2 measurements using TRS, we compared ScO2 with jugular venous oxygen saturation (SjO2) during carotid endarterectomy. We also investigated factors associated with cerebral oxygen desaturation during clamping of the carotid artery. METHODS: Sixty patients who underwent carotid endarterectomy were enrolled. ScO2 was measured by TRS-20 using TRS at 10 minutes before and after clamping of the carotid artery and 10 minutes after unclamping. SjO2 was measured simultaneously. The relationship between ScO2, SjO2, and estimated ScO2 (0.75×SjO2+0.25×SaO2) were examined by simple regression and the Bland-Altman analysis. Factors related to ScO2<60% were investigated by logistic regression analysis. RESULTS: There was a significant correlation between ScO2 and SjO2 (r=0.49, P<0.002). Bland-Altman analysis revealed narrow limits of agreement between ScO2 and SjO2 (bias, 9.2%; precision, 12.6%), as well as ScO2 and estimated ScO2 (bias, -1.3%; precision, 9.7%). Impaired cerebral hemodynamics (Powers stage 2 or Kuroda type 3) was significantly associated with ScO2<60%. CONCLUSIONS: ScO2 measured by TRS and SjO2 showed narrow limits of agreement. Reduced ScO2 was significantly associated with impaired cerebral hemodynamics.

[Bladder temperature versus tympanic temperature in patients undergoing abdominal aortic aneurysm surgery].

BACKGROUND: Inaccurate measurements of body temperature might be associated with complications during the perioperative period. We conducted a retrospective cohort study to compare the bladder temperature and the tympanic membrane temperature in patients undergoing open repair of abdominal aortic aneurysm. METHODS: Fifteen adult patients who had undergone general anesthesia with/without epidural anesthesia were included in the present cohort. The bladder and the tympanic temperatures were simultaneously recorded at 6 points during surgery. One-way repeated measures ANOVA and Bland-Altman analysis were performed to assess statistical significance. The two-tailed P values less than 0.05 were considered statistically significant. RESULTS: No difference was found between the bladder and the tympanic temperatures before abdominal aortic cross-clamping. However, during and after cross-clamping, the bladder temperature values were likely to be lower compared with the tympanic values. The average temperature difference (+/- 2 SD) was 0.4 degrees C (+/- 1.1 degrees C) (95% CI: -1.21-0.78). CONCLUSIONS: The tympanic membrane might be a reliable site for core body temperature measurement in abdominal aortic aneurysm surgery patients.

[Two cases showing the absence of motor evoked potentials without developing postoperative paraplegia following thoracoabdominal aortic repair--role of epidural cooling, spinal drainage and aorto-iliac side-arm conduit distal perfusion].

We describe two cases which developed loss of motor evoked potentials from bilateral lower limbs following thoracoabdominal aortic repair. Paraplegia was suspected in both cases; however, one case of Crawford type 2 aneurysm showed transient left leg monoplegia with a sensory deficit and the other case of aortic pseudoaneurysm showed no neurologic dysfunction postoperatively. We employed epidural cooling and spinal drainage for spinal protection and distal perfusion was provided through aorto-iliac side-arm conduit. Despite the prolonged spinal ischemia during thoracoabdominal aortic repair, spinal drainage and epidural cooling were very helpful for protecting the spinal cord from ischemia. The interpretation of MEPs seems very difficult especially when the potentials remain absent even after reconstruction or reperfusion of segmental arteries, because variety of intraoperative factors may affect them.

Spinal cord ischemia after endovascular aortic repair versus open surgical repair for descending thoracic and thoracoabdominal aortic aneurism.

PURPOSE: Thoracic endovascular aortic repair (TEVAR) an emerging less invasive alternative to surgery, is now being increasingly employed, but spinal cord ischemia (SCI) is still a threat with this procedure. Delayed paraplegia has been frequently observed after TEVAR, suggesting there may be different courses of SCI between TEVAR and the conventional open surgical repair (OSR) of thoracic and thoracoabdominal aneurysms. Therefore, we conducted a study to investigate the risk factors for and the course of SCI after TEVAR and OSR. METHODS: We studied a series of 414 OSR and 94 TEVAR patients prospectively. Postoperative motor function, sensory disturbance, and bladder disturbance were assessed daily to evaluate the course of SCI. Previously reported risk factors for SCI were investigated. RESULTS: Spinal cord ischemia occurred in 6 patients (6.4 %) in the TEVAR group, and in 18 patients (4.3 %) in the OSR group, resulting in no significant difference (p = 0.401). A greater percentage of patients (n = 4, 66.7 %) with SCI in the TEVAR group had a delayed onset, compared with 16.7 % (n = 3) in the OSR group (p = 0.038). The rate of recovery of walking function after SCI and the incidence of sensory disturbance and bladder dysfunction was similar in the two groups. Multivariate analysis demonstrated that, in the TEVAR group, the stent length of aortic coverage was a significant risk factor for SCI. CONCLUSION: The incidence of SCI was similar in the OSR and TEVAR groups, but delayed SCI occurred more frequently in the TEVAR group. Except for the delayed onset of SCI, SCI showed a similar course of recovery in the two groups.

Clinical comparison of an echocardiograph-derived versus pulse counter-derived cardiac output measurement in abdominal aortic aneurysm surgery.

OBJECTIVE: To compare cardiac output (CO) measurements acquired using the Flotrac/Vigileo system (Edwards Lifesciences, Irvine, CA) and CO measured by transesophageal echocardiography using the product of the aortic valve area, the time integral of flow at the same site, and the heart rate during abdominal aortic aneurysm (AAA) surgery. DESIGN: A prospective clinical study. SETTING: Cardiac surgery operating room of 1 heart center hospital. PARTICIPANTS: Twenty patients undergoing elective AAA surgery. INTERVENTIONS: CO was determined simultaneously using the Flotrac/Vigileo system (CO(AP)) and transesophageal echocardiography (CO(TEE)) as the reference method at 8 time points during AAA surgery. MEASUREMENTS AND MAIN RESULTS: One hundred sixty simultaneous datasets were obtained. The authors observed a significant correlation between CO(AP) and CO(TEE) values (R = 0.56, p < 0.001). Bland-Altman analysis of CO(AP) and CO(TEE) showed a bias of 0.12 L/min and limits of agreement from -1.66 to 1.90 L/min, with a percentage error of 41%. Just after aortic clamping, CO(AP) significantly increased, but CO(TEE) decreased in comparison with previous measurements. There was a significant association among changes in CO(AP) and pulse pressure, heart rate, and central venous pressure (CVP). However, changes in CO(TEE) were only associated with variations in heart rate. CONCLUSIONS: CO(AP) values were not clinically acceptable for use in AAA surgery because of wide variations during aortic clamping and declamping. Changes in pulse pressure, heart rate, and CVP were associated with significant changes in CO(AP), whereas only changes in heart rate showed associated changes in CO(TEE).

Risk factors of stroke and delirium after off-pump coronary artery bypass surgery.

Off-pump coronary artery bypass surgery (CABG) has not abolished the risk of postoperative stroke and delirium seen for on-pump CABG. Advanced arteriosclerotic changes are common in both on-pump and off-pump CABG. We sought to analyze if advanced arteriosclerotic changes are risk factors of stroke or transient ischemic attack (TIA), and delirium after off-pump CABG. Patients undergoing off-pump CABG between 2001 and 2005 were reviewed using medical records (n=685). Potential risk factors of postoperative stroke and delirium were identified from previous studies. Further, variables retrieved from carotid artery duplex scanning as indices of advanced arteriosclerosis, were examined. The incidences of postoperative stroke/TIA and delirium after off-pump CABG were 2.6% (n=18) and 16.4% (n=112), respectively. Carotid artery stenosis >50% was a significant risk factor of stroke or TIA (P=0.02) as well as delirium (P=0.04) after off-pump CABG. A history of atrial fibrillation (AF) (P=0.037) or diabetes mellitus (P=0.041) was a risk factors of postoperative stroke or TIA. In contrast, age over 75 years (P=0.006), creatinine >1.3 mg/dl (99 µmol/l) (P=0.011), a history of hypertension (P=0.001), past history of AF (P=0.024), and smoking (P=0.048) were significant risk factors of postoperative delirium.