Broadband and tunable optical parametric generator for remote detection of gas molecules in the short and mid-infrared.

The development of a novel broadband and tunable optical parametric generator (OPG) is presented. The OPG properties are studied numerically and experimentally in order to optimize the generator's use in a broadband spectroscopic LIDAR operating in the short and mid-infrared. This paper discusses trade-offs to be made on the properties of the pump, crystal, and seeding signal in order to optimize the pulse spectral density and divergence while enabling energy scaling. A seed with a large spectral bandwidth is shown to enhance the pulse-to-pulse stability and optimize the pulse spectral density. A numerical model shows excellent agreement with output power measurements; the model predicts that a pump having a large number of longitudinal modes improves conversion efficiency and pulse stability.

Cognitive dysfunction following desflurane versus sevoflurane general anesthesia in elderly patients: a randomized controlled trial.

UNLABELLED: As life expectancy increases, more patients ≥65 years undergo general anesthesia. Anesthetic agents may contribute to postoperative cognitive dysfunction, and incidence may differ with anesthetic agents or intraoperative anesthesia depth. Responses to anesthetic adjuvants vary among elderly patients. Processed electroencephalography guidance of anesthetic may better ensure equivalent cerebral suppression. This study investigates postoperative cognitive dysfunction differences in elderly patients given desflurane or sevoflurane using processed electroencephalography guidance.IRB approved, randomized trial enrolled consenting patients ≥65 years scheduled for elective surgery requiring general anesthesia ≥120 minute duration. After written informed consent, patients were randomly assigned to sevoflurane or desflurane. No perioperative benzodiazepines were administered. Cognitive impairment was measured by an investigator blinded to group assignment using mini-Mental Status Examination (MMSE) at baseline; 1, 6, and 24 hours after the end of anesthesia. Mean arterial pressure was maintained within 20% of baseline. Anesthetic dose was adjusted to maintain moderate general anesthesia per processed electroencephalograpy (Patient State Index 25 to 50). The primary outcome measure was intergroup difference in MMSE change 1 hour after anesthesia (median; 95% confidence interval).110 patients consented; 26 were not included for analysis (no general anesthesia; withdrew consent; baseline MMSE abnormality; inability to perform postoperative MMSE; data capture failure); 47 sevoflurane and 37 desflurane were analyzed. There were no significant differences in patient characteristics; intraoperative mean blood pressure (desflurane 86.4; 81.3 to 89.6 versus sevoflurane 82.5; 80.2 to 86.1 mmHg; p = 0.42) or Patient State Index (desflurane 41.9; 39.0 to 44.0 versus sevoflurane 41.0; 37.5 to 44.0; p = 0.60) despite a lower MAC fraction in desflurane (0.82; 0.77 to 0.86) versus sevoflurane (0.96; 0.91 to 1.03; p < 0.001). MMSE decreased 1 hour after anesthesia (p < 0.001). The decrease at one hour was larger in sevoflurane (-2.5; -3.3 to -1.8) than desflurane (-1.3; -2.2 to -0.5; p = 0.03). MMSE returned to baseline by 6 hours after anesthesia. CONCLUSIONS: For elderly patients in whom depth of anesthesia is maintained in the moderate range, both desflurane and sevoflurane are associated with transient decreases in cognitive function as measured by MMSE after anesthesia, with clinically insignificant differences between them in this setting. TRIAL REGISTRY: ClinicalTrials.gov NCT01199913.

Who is at risk for postdischarge nausea and vomiting after ambulatory surgery?

BACKGROUND: About one in four patients suffers from postoperative nausea and vomiting. Fortunately, risk scores have been developed to better manage this outcome in hospitalized patients, but there is currently no risk score for postdischarge nausea and vomiting (PDNV) in ambulatory surgical patients. METHODS: We conducted a prospective multicenter study of 2,170 adults undergoing general anesthesia at ambulatory surgery centers in the United States from 2007 to 2008. PDNV was assessed from discharge until the end of the second postoperative day. Logistic regression analysis was applied to a development dataset and the area under the receiver operating characteristic curve was calculated in a validation dataset. RESULTS: The overall incidence of PDNV was 37%. Logistic regression analysis of the development dataset (n=1,913) identified five independent predictors (odds ratio; 95% CI): female gender (1.54; 1.22 to 1.94), age less than 50 yr (2.17; 1.75 to 2.69), history of nausea and/or vomiting after previous anesthesia (1.50; 1.19 to 1.88), opioid administration in the postanesthesia care unit (1.93; 1.53 to 2.43), and nausea in the postanesthesia care unit (3.14; 2.44-4.04). In the validation dataset (n=257), zero, one, two, three, four, and five of these factors were associated with a PDNV incidence of 7%, 20%, 28%, 53%, 60%, and 89%, respectively, and an area under the receiver operating characteristic curve of 0.72 (0.69 to 0.73). CONCLUSIONS: PDNV affects a substantial number of patients after ambulatory surgery. We developed and validated a simplified risk score to identify patients who would benefit from long-acting prophylactic antiemetics at discharge from the ambulatory care center.

Use of sugammadex in patients with a history of pulmonary disease.

STUDY OBJECTIVE: To evaluate the safety and efficacy of sugammadex for reversal of rocuronium-induced neuromuscular blockade in patients with pulmonary disease. DESIGN: Phase III, randomized, multicenter, parallel-group, comparative, safety-assessor blinded study. SETTING: Nine hospital sites. PATIENTS: 77 ASA physical status 2 and 3 patients, aged ≥ 18 years, with a history of pulmonary disease, and scheduled for surgery with general anesthesia requiring neuromuscular blockade. INTERVENTIONS: Following anesthesia induction, patients received rocuronium 0.6 mg/kg with 0.15 mg/kg maintenance doses as needed. Patients were randomized to receive sugammadex 2 mg/kg or 4 mg/kg after the last rocuronium dose at reappearance of the second twitch. MEASUREMENTS: Safety evaluations included adverse events, laboratory parameters, vital signs, and evidence of recurrent or residual neuromuscular blockade. Efficacy was evaluated as the time from sugammadex administration to recovery of the train-of-four (TOF) ratio to ≥ 0.9. MAIN RESULTS: Safety was comparable between doses, with no evidence of residual or recurrent neuromuscular blockade. Two bronchospasm cases were reported (4 mg/kg group), both in patients with asthma who received desflurane for anesthesia maintenance. Geometric mean (95% confidence interval) times to a TOF ratio of ≥ 0.9 were 2.1 (1.7 - 3.1) min (2 mg/kg) and 1.8 (1.5 - 2.7) min (4 mg/kg). CONCLUSION: Sugammadex 2 mg/kg and 4 mg/kg were well tolerated and effective in patients with a history of pulmonary disease. Bronchospasm is a possibility when administering sugammadex to patients with underlying pulmonary disease.

Evaluation of pulse cooximetry in patients undergoing abdominal or pelvic surgery.

BACKGROUND: Intraoperative transfusion decisions generally are guided by blood loss estimation and periodic invasive hemoglobin measurement. Continuous hemoglobin measurement by pulse cooximetry (pulse hemoglobin; Rainbow® SET Pulse CO-Oximeter, Masimo Corporation, Irvine, CA) has good agreement with laboratory hemoglobin in healthy volunteers and could aid transfusion decision-making. Because intraoperative physiology may alter performance of this device, this study investigated pulse hemoglobin during surgery. METHODS: Ninety-one adult patients undergoing abdominal or pelvic surgery in which large blood loss was likely were studied. Time-matched pulse hemoglobin measurements were recorded for each intraoperative arterial hemoglobin measurement obtained. Agreement between measurements was assessed by average difference (mean ± SD, g/dl), linear regression, and multiple measures Bland-Altman analysis. RESULTS: The average difference between 360 time-matched measurements (bias) was 0.50 ± 1.44 g/dl, with wider limits of agreement (-2.3 to 3.3 g/dl) than reported in healthy volunteers. The average difference between 269 paired sequential pulse and arterial hemoglobin changes was 0.10 ± 1.11 g/dl, with half between -0.6 and 0.7 g/dl of each other. The bias was larger in patients with blood loss of more than 1,000 ml; hemoglobin less than 9.0 g/dl; any intraoperative transfusion; or intraoperative decrease in arterial hemoglobin at the time of sampling ≥2 g/dl (all P < 0.001). The range of bias was narrower at deeper anesthesia (P < 0.001). CONCLUSIONS: Evaluation of the sensor and software version tested suggests that although pulse cooximetry may perform well in ambulatory subjects, in patients undergoing surgery in which large blood loss is likely, an invasive measurement should be used in transfusion decision-making.

The accuracy of noninvasive and continuous total hemoglobin measurement by pulse CO-Oximetry in human subjects undergoing hemodilution.

BACKGROUND: Total hemoglobin (tHb) is one the most frequently ordered laboratory measurements. Pulse CO-Oximetry™ (Masimo Corp., Irvine, CA) is a multi-wavelength spectrophotometric method for noninvasive and continuous hemoglobin monitoring (SpHb). In this study, we evaluated the accuracy of SpHb compared with laboratory CO-Oximeter measurement of tHb from arterial blood samples in 20 healthy volunteer subjects undergoing hemodilution. METHODS: After enrollment, approximately 500 mL of blood was drawn from subjects through an arterial or venous catheter. Each subject then rapidly received crystalloid i.v. fluid to compensate for the decrease in intravascular volume and reduce the hemoglobin concentration. Subjects received a maximum of 30 mL/kg i.v. fluid. SpHb was continuously monitored and recorded, and serial arterial blood samples were taken during the procedure. SpHb accuracy was analyzed by pairing SpHb and tHb measurements after the arterial blood draw with the resulting tHb test result. Bias, precision, and the average root-mean-square error were calculated. RESULTS: One hundred sixty-five tHb measurements were collected. The average decrease in tHb during the blood removal and hemodilution procedure was 2.4 ± 0.8 g/dL (mean ± SD). The average difference between 335 paired measurements of SpHb and tHb was -0.15 g/dL, 1 SD of the difference was 0.92 g/dL, and the average root-mean-square difference was 0.94 g/dL. The difference between SpHb and tHb was <2.0 g/dL for 97% of the measurements. The difference was <1.5 g/dL for 97% of the measurements when tHb was <10 g/dL. CONCLUSIONS: Pulse CO-Oximetry-based SpHb measurement is accurate within 1.0 g/dL (1 SD) compared with laboratory CO-Oximeter tHb measurement in subjects undergoing hemodilution.

Neuroprotective effect of volatile anesthetic agents: molecular mechanisms.

INTRODUCTION: Intra-operative cerebral ischemia can be catastrophic, and volatile anesthetic agents have been recognized for their potential neuroprotective properties since the 1960s. In this review, we examine the neuroprotective effects of five volatile anesthetic agents in current or recent clinical use: isoflurane, sevoflurane, desflurane, halothane and enflurane. METHODS: A review of publications in the National Library of Medicine and National Institutes of Health database from 1970 to 2007 was conducted. RESULTS: Volatile anesthetic agents have been shown to be neuroprotective in multiple animal works of ischemic brain injury. Short-term neuroprotection (<1 week post-ischemia) in experimental cerebral ischemia has been reported in multiple works, although long-term neuroprotection (> or = 1 week post-ischemia) remains controversial. Comparison works have not demonstrated superiority of one specific volatile agent over another in experimental models of brain injury. Relatively few human works have examined the protective effects of volatile anesthetic agents and conclusive evidence of a neuroprotective effect has yet to emerge from human works. CONCLUSION: Proposed mechanisms related to the neuroprotective effect of volatile anesthetic agents include activation of ATP-dependent potassium channels, up-regulation of nitric oxide synthase, reduction of excitotoxic stressors and cerebral metabolic rate, augmentation of peri-ischemic cerebral blood flow and up-regulation of antiapoptotic factors including MAP kinases.

Simvastatin treatment in surgically induced brain injury in rats.

BACKGROUND: HMG-CoA reductase inhibitors (Statins) have been shown to reduce blood brain barrier (BBB) disruption and improve neurologic outcome in cerebrovascular disorders. Brain injury due to neurosurgical procedures can lead to post-operative complications such as brain edema and altered neurologic function. The objective of this study was to evaluate whether simvastatin reduces brain edema by preventing BBB disruption and improves neurologic status after surgically-induced brain injury (SBI). METHODS: Animals were pretreated for seven days with vehicle or simvastatin i.p. daily, after which they underwent SBI. Neurologic evaluation was assessed at 24 hours post-SBI and the animals were sacrificed for brain water content calculation and BBB evaluation. FINDINGS: Brain water content was significantly increased in the right frontal lobe in all SBI groups as compared to the left frontal lobe. There was no significant difference in brain water content in the right frontal lobe between simvastatin and vehicle treated groups. Evans blue testing did not show a significant difference in disruption of the BBB between groups. Neurologic scores were not significantly different. CONCLUSIONS: Simvastatin did not reduce brain water content, protect the BBB, or improve neurologic scores after SBI.

3% hypertonic saline following subarachnoid hemorrhage in rats.

BACKGROUND: Hypertonic saline (HTS) has been proposed as a treatment after aneurysmal subarachnoid hemorrhage (SAH) to minimize ischemic brain injury due to its osmotic and rheologic properties. Although the benefits of 7.2% HTS use in brain injury have been studied, there is a paucity of data on the use of 3%HTS. METHODS: We investigated whether 3%HTS can reduce brain water content and improve neurologic function after SAH in the rodent model compared to 0.9% saline solution (NS). Neurologic testing was conducted at 24 hours post-SAH prior to sacrificing animals for brain water content evaluation. FINDINGS: There was significant potentiation of brain water content in the right hemisphere between 3%HTS and NS groups. The modified Garcia score was not significantly different between the two groups; however, the vibrissae-stimulated forelimb placement test showed significantly lower scores in the HTS group. 3%HTS does not decrease brain edema or improve neurologic deficits as compared to NS. In fact, our study showed 3%HTS potentiated brain edema and worsened neurologic deficits in the rat SAH model. CONCLUSIONS: Given the potential adverse effects of HTS therapies, including hyperchloremic acidosis, and the lack of benefit found in our study, more investigation is required to evaluate the clinical use of 3%HTS in the setting of SAH.

The hemodynamically unstable patient in the intensive care unit: hemodynamic vs. transesophageal echocardiographic monitoring.

OBJECTIVE: Transesophageal echocardiography is a diagnostic and monitoring modality. The objectives of our study were to compare the diagnoses obtained with continuous transesophageal echocardiography and hemodynamic monitoring in the intensive care unit, to determine interobserver variability of diagnosis obtained with both modalities, and to evaluate its impact. DESIGN: Prospective cohort study. SETTING: Surgical intensive care unit. PATIENTS: Consecutive hemodynamically unstable patients after cardiac surgery. INTERVENTIONS: At admission, unstable patients were monitored during 4 hrs with transesophageal echocardiography and standard hemodynamic monitoring. The critical care physician evaluated the patients based on all information except the transesophageal echocardiography at 0, 2, and 4 hrs and formulated a hypothesis on the most likely cause of hemodynamic instability. Transesophageal echocardiography information was provided after each evaluation. To evaluate interobserver variability, all the hemodynamic and echocardiographic information was gathered, randomized, and evaluated by five clinicians for the hemodynamic data and five echocardiographers for the transesophageal echocardiography data. The evaluators were blinded to all other information. Kappa statistics were used to evaluate agreement. Impact of transesophageal echocardiography was assessed retrospectively by using the Deutsch scale. RESULTS: Twenty patients qualified for the study. The agreement between the hemodynamic and echocardiographic diagnosis showed a kappa at admission, 2 hrs, and 4 hrs of 0.33, 0.47, and 0.28. The interobserver agreement for the initial diagnosis (p =.014) and between all evaluators (p <.001) was significantly higher in the echocardiographic compared with the hemodynamic group. The transesophageal echocardiographic information was considered retrospectively to be essential in 34% and valuable in 34% of cases. CONCLUSIONS: These observations support the belief that transesophageal echocardiographic monitoring in the intensive care unit is associated with higher interobserver agreement in diagnosing and excluding significant causes of hemodynamic instability for postoperative cardiac surgical patients.