Comparison of the Effects of Propofol and Sevoflurane Induced Burst Suppression on Cerebral Blood Flow and Oxygenation: A Prospective, Randomised, Double-Blinded Study.

OBJECTIVE: Pharmacologically induced electroencephalogram (EEG) silence increases tolerance of ischemic period by reducing cerebral metabolism. We hypothesized that sevoflurane, a cerebral vasodilator, will maintain cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) better than propofol, a cerebral vasoconstrictor, during EEG silence. To validate this, we compared the effect of sevoflurane and propofol on CBF and CMRO2 during surgical plane of anasthesia (SP) and burst suppression on EEG (BS). METHODS: We conducted a prospective, double-blinded trial where patients undergoing neurosurgery were randomized to receive propofol or sevoflurane. Mean velocity (MV) and pulsatility index (PI) of bilateral middle cerebral arteries (MCA) were measured as surrogate of CBF. Jugular venous oxygen saturation (SjvO2) and arteriovenous oxygen difference (AjvDO2) were obtained to assess CMRO2. The values were compared between groups using Student t test and within the group with analysis of variance at SP and BS. RESULTS: BS decreased MV and increased PI in propofol group (P < 0.001 and P < 0.02 on normal side, P < 0.004 and P < 0.001 on tumor side). There was no significant change in sevoflurane group. BS with sevoflurane increased SjvO2 (P < 0.001) and decreased AjvDO2 (P < 0.001). Change in SjvO2 and AjvDO2 with propofol at SP and BS was variable. CONCLUSIONS: In our study, sevoflurane had a safer profile on cerebral oxygenation during BS while not altering the CBF, suggesting increased availability of oxygen. Propofol, on the other hand, produced cerebral vasoconstriction with BS. The effect of propofol on oxygenation was unpredictable, with low SjvO2 and high AjvDO2 even at surgical plane of anesthesia.

A Study Comparing Propofol Auto-coinduction and Standard Propofol Induction in Patients Undergoing General Anesthesia Without Midazolam Pretreatment: A Prospective Randomized Control Trial.

BACKGROUND: Propofol has emerged as an induction agent of choice over the past two decades due to its quick, smooth induction and rapid recovery. The main concern for an anesthesiologist is the hemodynamic instability caused by the standard induction dose of propofol (2-3 mg/kg). AIM: We aim to study the efficacy of propofol auto-coinduction technique in comparison to the standard propofol induction technique in terms of the total induction dose requirement of propofol, the incidence of hemodynamic side effects and pain on injection, and the incidence of fentanyl-induced cough (FIC) in the absence of a synergistic agent like midazolam. MATERIALS AND METHODS: This was a prospective, observer-blinded, randomized controlled trial. The study was initiated after obtaining the institutional ethics committee approval and is registered in the Clinical Trials Registry India. Eighty American Society of Anesthesiology Physical Status I and II patients, of either sex, aged between 18 and 55 years, and scheduled for elective surgeries under general anesthesia were randomized into two equal groups. Patients allocated to Group I (auto-coinduction) received 20% of the calculated dose of injection propofol 2 mg/kg (i.e., 0.4 mg/kg) as the priming dose followed by injection fentanyl 1 µg/kg after 1 min and the remaining propofol was administered in titrated doses till loss of verbal response after 2 min. In Group II (control), patients received injection fentanyl 1 µg/kg followed by single bolus dose of injection propofol up to 2 mg/kg till loss of verbal response. Midazolam was not used for premedication or induction. Intubation was carried out only after ensuring achievement of optimum depth of anesthesia using bispectral index scale. The total dose of propofol administrated for induction, occurrence of pain on injection, severity of cough after fentanyl administration, hemodynamic parameters, and apneic episodes were recorded. STATISTICAL ANALYSIS: All data were expressed as mean ± 2 standard deviation. For statistical analysis, SPSS software version 16 (SPSS Inc., 2007, Chicago, IL, USA) was used. RESULTS: The mean dose of injection propofol required for induction was significantly lower in Group I (67.0 ± 17.9 mg) when compared with Group II (111.3 ± 17.6 mg) (P < 0.01). The mean heart rate was significantly higher (P < 0.01) and the mean blood pressure was significantly lower in Group II (P < 0.01) when compared to Group I at 1 min postinduction, immediately after intubation, and 5 min after induction. The incidence of complications such as hypotension, pain on injection, and FIC was higher in Group II (50%) as compared to Group I (18%). CONCLUSION: In our study, we found that the induction dose requirement of propofol was significantly lower in the auto-coinduction group when compared to the conventional induction group. The auto-coinduction technique offered a stable hemodynamic profile, reduced pain on injection, and less incidence of FIC as compared to the conventional propofol induction technique.

Anesthetic management of a patient with polycythemia vera for neurosurgery.

Polycythemia vera (PV) is a myeloproliferative disorder characterized by excess red cell clonality. The increased number of red blood cells can lead to increased viscosity of the blood and ultimately compromise the blood supply to the end organs. Thromboembolic and hemorrhagic complications can also develop. Patients with PV presenting with neurological diseases that require surgical intervention are at an increased risk due to various factors, such as immobility, prolonged surgical time, hypothermia and dehydration. We report anesthetic management of a patient with PV who underwent neurosurgical intervention for vestibular schwannoma excision.

Cerebral vascular effects of loading dose of dexmedetomidine: A Transcranial Color Doppler study.

BACKGROUND: Dexmedetomidine has been widely used in critical care settings because of its property of maintaining stable hemodynamics and inducing conscious sedation. The use of dexmedetomidine is in increasing trend particularly in patients with neurological disorders. Very few studies have focused on the cerebral hemodynamic effects of dexmedetomidine. This study is aimed to address this issue. METHODS: Thirty patients without any intracranial pathology were included in this study. Middle cerebral artery flow velocity obtained from transcranial color Doppler was used to assess the cerebral hemodynamic indices. Mean flow velocity (mFV), pulsatility index (PI), cerebral vascular resistant index (CVRi), estimated cerebral perfusion pressure (eCPP), and zero flow pressure (ZFP) were calculated bilaterally at baseline and after infusion of injection Dexmedetomidine 1 mcg/Kg over 10 min. RESULTS: Twenty-six patients completed the study protocol. After administration of loading dose of dexmedetomidine, mFV and eCPP values were significantly decreased in both hemispheres (P < 0.05); PI, CVRi, and ZFP values showed significant increase (P < 0.05) after dexmedetomidine infusion. CONCLUSION: Increase in PI, CVRi, and ZFP suggests that there is a possibility of an increase in distal cerebral vascular resistance (CVR) with loading dose of dexmedetomidine. Decrease in mFV and eCPP along with an increase in CVR may lead to a decrease in cerebral perfusion. This effect can be exaggerated in patients with preexisting neurological illness. Further studies are needed to evaluate the effect of dexmedetomidine on various other pathological conditions involving brain like traumatic brain injury and vascular malformations.

Fluoroscopy assisted tracheal intubation in a case of anticipated difficult airway: Fail safe devices can also fail.

Difficulty in airway management is the most important cause of major anesthesia-related morbidity and mortality. Unexpected difficulties may arise even with proper preanesthesia planning. Here, we report a case of anticipated difficult airway primarily planned for flexible fibreoptic bronchoscope assisted intubation, but due to unexpected failure of light source, fluoroscopy was used, and the airway was successfully secured.

Effect of Loading Dose of Dexmedetomidine on Dynamic Cerebral Blood Flow Autoregulation in Patients With Intracranial Glial Neoplasms.

BACKGROUND: Dexmedetomidine has been widely used in neuroanesthesia and critical care settings. The effects of dexmedetomidine on cerebral vascular autoregulation and hemodynamics in patients with intracranial pathology are not well defined. This study is aimed to address this issue. METHODS: Fifteen patients with unilateral supratentorial glial tumor (group S) and 15 patients without any intracranial pathology (group C) were included in this study. Transient hyperemic response testing was conducted bilaterally in both groups with transcranial color Doppler. Dynamic autoregulation was assessed with transient hyperemic response ratio (THRR) and strength of autoregulation (SA) at baseline and after infusion of inj. dexmedetomidine (1 mcg/kg) over 10 minutes. RESULTS: THRR and SA values in the hemisphere that had tumor (group S) showed no difference from baseline after a loading dose of dexmedetomidine (P=0.914, 0.217). In the nontumor hemisphere of group S and in both the hemispheres of group C, significant reduction in THRR and SA values were observed (P<0.001) after administration of a loading dose of dexmedetomidine. THRR values were higher in the tumor hemisphere when compared with the nonpathologic hemispheres (P<0.001), suggesting the possibility of baseline hyperemia. CONCLUSIONS: In the hemisphere that had glial tumor, autoregulatory indices showed no significant change after dexmedetomidine. It can be because of abnormal vascular architecture and its altered reactivity to dexmedetomidine, or because of baseline hyperemia itself, but the exact mechanism needs to be elucidated. In the nonpathologic hemispheres, THRR and SA values were decreased, suggesting impaired autoregulation with the use of loading dose of dexmedetomidine.

Transesophageal echocardiographic evaluation of left ventricular systolic and diastolic function in response to 20% mannitol and 3% hypertonic saline infusion in neurosurgical patients undergoing craniotomy.

BACKGROUND: Mannitol and hypertonic saline (HS) are routinely used during craniotomy. Both increase myocardial preload and reduce afterload, and may improve cardiac output. It is not currently known whether this results in an improvement in the global myocardial function. Thus, the aim of this study was to compare the effects of a single equiosmolar bolus of 20% mannitol (5 mL/kg) or 3% HS (5 mL/kg) on the global myocardial function by tissue Doppler-derived myocardial performance index (TD-MPI) in patients undergoing craniotomy. METHODS: Fifty adult patients were included and randomized to receive either mannitol or 3% HS. Transesophageal echocardiography was performed in all patients. Early (E) and late (A) peak mitral inflow velocity, early diastolic mitral annular velocity (E prime), isovolumetric relaxation time (IVRT), ejection time (ET), and isovolumetric contraction time (IVCT) were recorded at baseline and at 15, 30, 60, and 120 minutes after administration of the hyperosmolar solutions. TD-MPI was calculated as IVRT+IVCT/ET. RESULTS: There were no significant differences in the TD-MPI (HS vs. mannitol: 0.43 vs. 0.44 [baseline], 0.45 vs. 0.43 [15 min], 0.44 vs. 0.45 [30 min], 0.47 vs. 0.45 [60 min], 0.45 vs. 0.46 [120 min]), E/A ratio, IVCT, and E/E' either within or between the 2 groups at any time point. IVRT was prolonged in HS group as compared with baseline at 15, 30, and 60 minutes postinfusion. ET was decreased in both the groups at 120 minutes postinfusion. Neither of these altered the TD-MPI. CONCLUSIONS: Equiosmolar administration of 20% mannitol and 3% HS did not show any difference in global myocardial performance as measured by TD MPI.

A retrospective analysis of stridor after vestibular schwannoma surgery.

BACKGROUND: Transient lower cranial nerve deficits may occur after surgery in the posterior cranial fossa. Stridor has been reported after cerebellopontine angle epidermoid resection. The aim of this retrospective study is to find out whether any preoperative, intraoperative, and postoperative factors lead to stridor after resection of vestibular schwannoma. METHODS: Data of patients who underwent vestibular schwannoma resection from 2006 to 2011 were collected. We collected the following factors--age, sex, weight, diabetes, hypertension, preoperative cranial nerve deficits, tumor characteristics, intraoperative use of nitrous oxide, difficult endotracheal intubation, duration of surgery, postoperative cough and swallowing difficulty, limb weakness, and facial edema. Data of patients who developed stridor were compared with those who did not develop stridor. Odds ratio (OR) was used to assess the risk of developing stridor with each factor. RESULTS: Thirteen patients (4.65%) developed stridor in immediate postextubation period. The risk of stridor was significantly high in patients who had difficult intubation (OR=9.56), longer duration of surgery (P=0.034) and in patients who developed facial edema (OR=13.33), upperlimb weakness (OR=32.88), poor cough (OR=7.72), and swallowing difficulty (OR=24.97) in the postoperative period. CONCLUSIONS: The identification of the exact etiology of stridor often is difficult. Our results suggest that stridor may be more likely in patients who were difficult to intubate, had longer duration of surgery, who develop facial and neck edema and upperlimb weakness, poor cough, and swallowing after surgery. Establishing airway patency with intubation of the trachea may be required if patients develop oxygen desaturation due to stridor.