Lingzhong Meng

Effect of phenylephrine and ephedrine bolus treatment on cerebral oxygenation in anaesthetized patients

BACKGROUND How phenylephrine and ephedrine treatments affect global and regional haemodynamics is of major clinical relevance. Cerebral tissue oxygen saturation (Sct(O2) )-guided management may improve postoperative outcome. The physiological variables responsible for Sct(O2) changes induced by phenylephrine and ephedrine bolus treatment in anaesthetized patients need to be defined. METHODS A randomized two-treatment cross-over trial was conducted: one bolus dose of phenylephrine (100-200 µg) and one bolus dose of ephedrine (5-20 mg) were given to 29 ASA I-III patients anaesthetized with propofol and remifentanil. , mean arterial pressure (MAP), cardiac output (CO), and other physiological variables were recorded before and after treatments. The associations of changes were analysed using linear-mixed models. RESULTS The CO decreased significantly after phenylephrine treatment [▵CO = -2.1 (1.4) litre min(-1), P<0.001], but was preserved after ephedrine treatment [▵CO = 0.5 (1.4) litre min(-1), P>0.05]. The was significantly decreased after phenylephrine treatment [▵ = -3.2 (3.0)%, P<0.01] but preserved after ephedrine treatment [▵ = 0.04 (1.9)%, P>0.05]. CO was identified to have the most significant association with (P<0.001). After taking CO into consideration, the other physiological variables, including MAP, were not significantly associated with (P>0.05). CONCLUSIONS Associated with changes in CO, decreased after phenylephrine treatment, but remained unchanged after ephedrine treatment. The significant correlation between CO and implies a cause-effect relationship between global and regional haemodynamics.

Awake craniotomy to maximize glioma resection: methods and technical nuances over a 27-year period

OBJECT Awake craniotomy is currently a useful surgical approach to help identify and preserve functional areas during cortical and subcortical tumor resections. Methodologies have evolved over time to maximize patient safety and minimize morbidity using this technique. The goal of this study is to analyze a single surgeons experience and the evolving methodology of awake language and sensorimotor mapping for glioma surgery. METHODS The authors retrospectively studied patients undergoing awake brain tumor surgery between 1986 and 2014. Operations for the initial 248 patients (1986-1997) were completed at the University of Washington, and the subsequent surgeries in 611 patients (1997-2014) were completed at the University of California, San Francisco. Perioperative risk factors and complications were assessed using the latter 611 cases. RESULTS The median patient age was 42 years (range 13-84 years). Sixty percent of patients had Karnofsky Performance Status (KPS) scores of 90-100, and 40% had KPS scores less than 80. Fifty-five percent of patients underwent surgery for high-grade gliomas, 42% for low-grade gliomas, 1% for metastatic lesions, and 2% for other lesions (cortical dysplasia, encephalitis, necrosis, abscess, and hemangioma). The majority of patients were in American Society of Anesthesiologists (ASA) Class 1 or 2 (mild systemic disease); however, patients with severe systemic disease were not excluded from awake brain tumor surgery and represented 15% of study participants. Laryngeal mask airway was used in 8 patients (1%) and was most commonly used for large vascular tumors with more than 2 cm of mass effect. The most common sedation regimen was propofol plus remifentanil (54%); however, 42% of patients required an adjustment to the initial sedation regimen before skin incision due to patient intolerance. Mannitol was used in 54% of cases. Twelve percent of patients were active smokers at the time of surgery, which did not impact completion of the intraoperative mapping procedure. Stimulation-induced seizures occurred in 3% of patients and were rapidly terminated with ice-cold Ringers solution. Preoperative seizure history and tumor location were associated with an increased incidence of stimulation-induced seizures. Mapping was aborted in 3 cases (0.5%) due to intraoperative seizures (2 cases) and patient emotional intolerance (1 case). The overall perioperative complication rate was 10%. CONCLUSIONS Based on the current best practice described here and developed from multiple regimens used over a 27-year period, it is concluded that awake brain tumor surgery can be safely performed with extremely low complication and failure rates regardless of ASA classification; body mass index; smoking status; psychiatric or emotional history; seizure frequency and duration; and tumor site, size, and pathology.

The impact of phenylephrine, ephedrine, and increased preload on third-generation Vigileo-FloTrac and esophageal doppler cardiac output measurements.

BACKGROUND:Cardiac output (CO) monitoring based on pulse contour analysis (Vigileo-FloTrac) has the potential to be used for goal-directed fluid therapy in the perioperative setting. However, factors such as vasopressor usage may impact Vigileo-FloTracs reliability in tracking CO changes. We tested third-generation Vigileo-FloTrac systems ability to accurately measure the changes in CO induced by vasopressor administration and increased preload in comparison with esophageal Doppler measurements. METHODS:In 33 anesthetized patients, CO was monitored simultaneously by the third-generation Vigileo-FloTrac and esophageal Doppler. Hemodynamic challenges included phenylephrine (to increase vasomotor tone), ephedrine (to increase myocardial contractility and heart rate), and whole-body tilting (to increase preload). Measurements were performed before and after each intervention. RESULTS:Overall, 176 pairs of CO measurements were obtained. The difference between paired pulse contour and Doppler measurements of CO was 0.14 ± 2.13 L/min (mean ± SD), and the percentage error (2 SD of the difference divided by the mean CO of the reference method) was 66%. The trending ability of pulse contour versus Doppler was 23% (concordance, the percentage of the total number of data points that are in 1 of the 2 quadrants of agreement) after phenylephrine treatment, 69% (concordance) after ephedrine treatment, and 96% (concordance) after whole-body tilting. CONCLUSIONS:The pulse contour method of measuring CO, as implemented in the third-generation Vigileo-FloTrac device, accurately tracks changes in CO when preload changes. However, the pulse contour method does not accurately track changes in CO induced with phenylephrine and ephedrine.

Cardiac Output and Cerebral Blood Flow: The Integrated Regulation of Brain Perfusion in Adult Humans.

Cerebral blood flow (CBF) is rigorously regulated by various powerful mechanisms to safeguard the match between cerebral metabolic demand and supply. The question of how a change in cardiac output (CO) affects CBF is fundamental, because CBF is dependent on constantly receiving a significant proportion of CO. The authors reviewed the studies that investigated the association between CO and CBF in healthy volunteers and patients with chronic heart failure. The overall evidence shows that an alteration in CO, either acutely or chronically, leads to a change in CBF that is independent of other CBF-regulating parameters including blood pressure and carbon dioxide. However, studies on the association between CO and CBF in patients with varying neurologic, medical, and surgical conditions were confounded by methodologic limitations. Given that CBF regulation is multifactorial but the various processes must exert their effects on the cerebral circulation simultaneously, the authors propose a conceptual framework that integrates the various CBF-regulating processes at the level of cerebral arteries/arterioles while still maintaining autoregulation. The clinical implications pertinent to the effect of CO on CBF are discussed. Outcome research relating to the management of CO and CBF in high-risk patients or during high-risk surgeries is needed.

Regulation of cerebral autoregulation by carbon dioxide.

Cerebral autoregulation describes a mechanism that maintains cerebral blood flow stable despite fluctuating perfusion pressure. Multiple nonperfusion pressure processes also regulate cerebral perfusion. These mechanisms are integrated. The effect of the interplay between carbon dioxide and perfusion pressure on cerebral circulation has not been specifically reviewed. On the basis of the published data and speculation on the aspects that are without supportive data, the authors offer a conceptualization delineating the regulation of cerebral autoregulation by carbon dioxide. The authors conclude that hypercapnia causes the plateau to progressively ascend, a rightward shift of the lower limit, and a leftward shift of the upper limit. Conversely, hypocapnia results in the plateau shifting to lower cerebral blood flows, unremarkable change of the lower limit, and unclear change of the upper limit. It is emphasized that a sound understanding of both the limitations and the dynamic and integrated nature of cerebral autoregulation fosters a safer clinical practice.

Comparison of noninvasive cardiac output measurements using the Nexfin monitoring device and the esophageal Doppler

STUDY OBJECTIVE To evaluate the validity of cardiac output (CO) measurements obtained using the Nexfin device in comparison to those obtained with the esophageal Doppler in steady-state conditions and after phenylephrine administration. DESIGN Prospective observational study. SETTING Operating room of a North American academic medical center. PATIENTS 25 ASA physical status 1, 2, and 3 patients referred for abdominal or orthopedic surgeries. INTERVENTIONS After endotracheal intubation, patients who presented with a 20% or greater decrease in mean arterial pressure (MAP) received an intravenous (IV) bolus of 100 μg of phenylephrine. If MAP was still 20% lower than the patients baseline level at least 10 minutes after the first vasopressor treatment, a second bolus of 100 μg of phenylephrine was given. MEASUREMENTS CO was measured simultaneously by esophageal Doppler (CO(ED)) and Nexfin (CO(NXF)) at baseline and when blood pressure peaked after an IV 100 μg phenylephrine bolus. Comparisons were then made between the two devices to evaluate the ability of the Nexfin device to track changes in CO. MAIN RESULTS 66 pairs of data were obtained. Mean CO(ED) and CO(NXF) were 4.7 ± 1.8 L/min and 5.6 ± 2.0 L/min, respectively. There was a significant relationship between CO(ED) and CO(NXF) (r(2) = 0.82; P < 0.001). The agreement between CO(ED) and CO(NXF) was 0.88 ± 0.86 L/min (Bland Altman). The mean percent error (Critchley and Critchley) of CO(NXF) versus CO(ED) was 37%. Trending analysis found a 94% concordance between changes in CO(ED) and CO(NXF) after phenylephrine administration. CONCLUSIONS Intraoperative CO measurement using the Nexfin device has a strong correlation with CO measured by esophageal Doppler.

The Potential Benefits of Awake Craniotomy for Brain Tumor Resection: An Anesthesiologist's Perspective.

Awake craniotomy for brain tumor resection is becoming a standard of care for lesions residing within or in close proximity to regions presumed to have language or sensorimotor function. Evidence shows an improved outcome including greater extent of resection, fewer late neurological deficits, shorter hospital stay, and longer survival after awake brain tumor resection compared with surgery under general anesthesia. The surgeon’s ability to maximize tumor resection within the constraint of preserving neurological function by intraoperative stimulation mapping in an awake patient is credited for this advantageous result. It is possible that the care provided by anesthesiologists, especially the avoidance of certain components of general endotracheal anesthesia, may also be important in the outcome of awake brain tumor resection. We present our interpretation of the evidence that we believe substantiates this proposition. However, due to the lack of direct evidence based on randomized-controlled trials and the heterogeneity of anesthetic techniques used for awake craniotomy, our perspective is largely speculative and hypothesis generating that needs to be validated or refuted by future quality research.

Recent trends in the anesthetic management of craniotomy for supratentorial tumor resection.

Purpose of review The article reviews the recent evidence on the anesthetic management of patients undergoing craniotomy for supratentorial tumor resection. Recent findings A rapid recovery of neurological function after craniotomy for supratentorial tumor allows for the prompt diagnosis of intracranial complications and possibly an early hospital discharge. Intraoperative esmolol infusion was shown to reduce the anesthetic requirements, and may facilitate a more rapid recovery of neurological function. Outpatient craniotomy for supratentorial tumor resection has been associated with several clinical and economic benefits, but has not gained widespread use because of skepticism and medical-legal concerns. Awake craniotomy is associated with advantageous outcomes compared with surgery under general anesthesia, and is regarded as the standard of care for tumors that reside in or in close proximity to the eloquent brain. Recent studies have demonstrated that intraoperative electroacupuncture, dexmedetomidine, pregabalin, and lidocaine may facilitate postcraniotomy pain management. The use of volatile anesthetic agents in cancer surgery is associated with a worse survival compared with intravenous anesthetics, possibly by hindering immunologic defenses against cancer cells. Summary Recent evidence has yielded valuable information regarding anesthetic management of patients undergoing supratentorial tumor craniotomy. Despite a plethora of studies that compare short-term outcomes using different anesthetic and analgesic regimens, randomized controlled trials that examine the long-term outcomes (i.e., neurocognitive function, quality of life, tumor recurrence, and survival) that are of particular interest to patients are needed.

Association of intraoperative cerebral and muscular tissue oxygen saturation with postoperative complications and length of hospital stay after major spine surgery: an observational study

Background. Compromised tissue oxygenation is one of the root causes of dysfunction of various organs and postoperative complications. Oxygenation of different tissue beds may follow different patterns of change during physiological derangement. Methods. Patients undergoing elective major posterior spine surgery participated in this prospective observational study. Cerebral tissue oxygen saturation (SctO 2 ) was monitored on the upper forehead and muscular tissue oxygen saturation (SmtO 2 ) on the lower leg. The associations of various oxygenation indices with postoperative composite complications and length of hospital stay (LOH) were investigated. Results. The number of composite complications per patient was 3  (2) while the LOH was 6 (3) days (n = 102). Multiple SmtO 2 indices (maximum, minimum, mean, median, and area under curve (AUC)) were associated with composite complications (univariate analysis, P  < 0.05). No SctO 2 indices were associated with complications. Multiple SmtO 2 indices (maximum, mean, median, and AUC) showed differences ( P  < 0.05) between patients with composite complications ≤3 and >3, respectively. SmtO 2 standard deviation, AUC, and AUC weighted, and SctO 2 standard deviation, were associated with LOH (univariate analysis, P  < 0.05). Two SmtO 2 indices (AUC and AUC weighted), showed differences ( P  < 0.05) between the patients with an LOH ≤6 and >6 days, respectively. SmtO 2 , but not SctO 2 , indices improved the adjusted R 2 for composite complications (+54.0%, P  = 0.0001) and LOH (+19.0%, P  = 0.02) based on multiple linear models. Conclusions. Muscular tissue oxygenation has a stronger association with postoperative complications and length of hospital stay than cerebral tissue oxygenation after major spine surgery.

Severe Intraoperative Hyperglycemia Is Independently Associated With Postoperative Composite Infection After Craniotomy: An Observational Study

BACKGROUND: Postoperative infection after craniotomy carries an increased risk of morbidity and mortality. Identification and correction of the risk factors should be prioritized. The association of intraoperative hyperglycemia with postoperative infections in patients undergoing craniotomy is inadequately studied. METHODS: A total of 224 patients were prospectively enrolled in 2 major medical centers to assess whether severe intraoperative hyperglycemia (SIH, blood glucose ≥180 mg/dL) is associated with an increased risk of postoperative infection in patients undergoing craniotomy. Arterial blood samples were drawn and analyzed immediately after anesthetic induction and again before tracheal extubation. The new onset of any type of infection within 7 days after craniotomy was determined. RESULTS: The incidence of new postoperative composite infection was 10% (n = 22) within the first week after craniotomy. Weight, sex, American Society of Anesthesiologists score, preoperative and/or intraoperative steroid use, and diabetes mellitus were not associated with postoperative infection. SIH was independently associated with postoperative infection (odds ratio [95% confidence interval], 4.17 [1.50–11.56], P = .006) after fitting a multiple logistic regression model to adjust for emergency surgery, length of surgery, and age ≥65 years. CONCLUSIONS: SIH is independently associated with postoperative new-onset composite infections in patients undergoing craniotomy. Whether prevention of SIH during craniotomy results in a reduced postoperative risk of infection is unknown and needs to be appraised by further study.