Minimum Alveolar Concentration Research Articles

Electroencephalogram Mechanism of Dexmedetomidine Deepening Sevoflurane Anesthesia.

Dexmedetomidine, as an α2-adrenoceptor agonist, plays anti-sympathetic, sedative and analgesic roles in perioperative period. Also, dexmedetomidine can reduce the minimal alveolar concentration (MAC) of sevoflurane and the risk of postoperative cognitive dysfunction (POCD) induced by sevoflurane anesthesia. But so far, the electroencephalogram (EEG) mechanism of dexmedetomidine deepening sevoflurane anesthesia is not clear. In this study, by analyzing the changes of the power spectrum and bicoherence spectrum of EEG before and after dexmedetomidine infusion, the EEG mechanism of dexmedetomidine deepening sevoflurane anesthesia was studied. We analyzed dexmedetomidine-induced changes in power spectrum and bicoherence spectrum in 23 patients under sevoflurane anesthesia. After anesthesia induction, the sevoflurane concentration was maintained at 0.8 MAC for 15 min, and then dexmedetomidine was administered at a loading dose of 0.8 μg/kg in 10 min, followed by a maintenance rate of 0.5 μg⋅kg–1⋅h–1. Frontal EEG data from 5 min before and 10 min after dexmedetomidine infusion were compared. After dexmedetomidine infusion, the mean α power peak decreased from 6.09 to 5.43 dB and shifted to a lower frequency, the mean θ bicoherence peak increased from 29.57 to 41.25% and shifted to a lower frequency, and the median α bicoherence peak increased from 41.49 to 46.36% and shifted to a lower frequency. These results demonstrate that dexmedetomidine deepens sevoflurane anesthesia, and enhances α and θ bicoherences while shifting peak values of these bands to lower frequencies through regulating thalamo-cortical reverberation networks probably.

Anesthetic Stability of Propofol, Dexmedetomidine, and Isoflurane by Measuring Bispectral Index (BIS) and Hemodynamic Indices: A Comparative Study

BackgroundHemodynamic changes and anesthetic awareness occurring during surgery under general anesthesia is a great concern for both surgeon and anesthesiologist. Maintenance of the adequate depth of anesthesia throughout the intraoperative period is important in maintaining hemodynamic stability, preventing intraoperative awareness, and avoiding postoperative recall.AimThis study aims to predict the anesthetic stability of propofol, dexmedetomidine, and isoflurane by measuring bispectral index (BIS) and hemodynamic indices.Materials and methodsThis is a prospective comparative study. Sixty patients of either sex, aged 18-60 years, with American Society of Anesthesiologist (ASA) physical status classification I and II, undergoing elective surgical procedures requiring general anesthesia were allocated into three groups of 20 each. Patients in each group were administered standard general anesthesia with routine hemodynamic monitoring along with BIS, and values were recorded at baseline and thereafter at every five-minute interval for the duration of surgery. Anesthesia was maintained in Group P using a bolus dose of propofol 1 milligram.kg-1 for 10 minutes followed by propofol infusion 50-75 microgram.kg-1.minute-1, Group D with a bolus dose of dexmedetomidine 1 microgram.kg-1 for 10 minutes followed by infusion 0.2-0.7 microgram.kg-1.hour-1, and Group I with isoflurane at 1 minimum alveolar concentration (MAC) for 10 minutes and then maintained between 0.5 MAC and 1.5 MAC until the duration of surgery. To maintain the surgical plane of anesthesia, the BIS score was monitored between 40 and 65. The quantitative variables were expressed as mean±SD and compared between groups using Student’s unpaired t-test. Data analysis was done using SPSS Statistics for Windows version 20.0 (IBM Corp., Armonk, NY, USA). A p-value of <0.05 was considered statistically significant.ResultsDuring intergroup comparison among study drugs, the mean BIS values were statistically significant among the groups (p<0.05). Hemodynamic indices were significantly better maintained in the dexmedetomidine group as compared to the isoflurane and propofol groups throughout the intraoperative period (p<0.05).ConclusionDexmedetomidine is better than propofol and isoflurane in maintaining the BIS score and hemodynamic parameters during the intraoperative period.

This Month in Anesthesiology

This Month in Anesthesiology

End-tidal Anesthetic Concentration: Monitoring, Interpretation, and Clinical Application

Age-adjusted fraction of minimum alveolar concentration derived from end-tidal anesthetic partial pressure measurement remains a useful drug advisory display to help prevent awareness if interpreted with proper understanding of the quantal and probabilistic nature of minimum alveolar concentration, semantics, drug interactions, and hysteresis.

Determination of the minimum alveolar concentration of isoflurane in donkeys.

To determine the minimum alveolar concentration (MAC) of isoflurane in donkeys and characterize recovery from anesthesia. 7 healthy castrated male adult donkeys. Anesthesia was induced with propofol and maintained under mechanical ventilation with 1.3% isoflurane end-tidal concentration (ETiso). The MAC of isoflurane was determined after a 60-minute propofol washout period using the bracketing method. A continuous noxious electrical stimulation was applied to the oral mucosa for 1 minute or until the donkey moved. The ETiso was increased or decreased by 10% depending on the response, and MAC was defined as the average of 2 ETiso values allowing and preventing movement in response to stimulation. Arterial blood gases were measured during anesthesia and the recovery period. Unassisted recovery was timed, and a quality score was assigned from 1 (very poor) to 5 (excellent). The mean dose of propofol required for induction was 3.0 ± 0.6 mg/kg. The MAC of isoflurane was 1.44 ± 0.13%. One donkey was excluded from the study because it was still responsive when stimulated at ETiso of 2.8%. Immediately after extubation, the median (range) partial pressure of oxygen in the arterial blood was 63 (minimum to maximum, 46 to 72) mm Hg and 3 donkeys were hypoxemic (partial pressure of arterial oxygen < 60 mm Hg). The median time to standing was 13 (7 to 38) minutes, while the recovery score was 3 (2 to 5). The MAC of isoflurane in donkeys is similar to that reported in other species. Oxygen support should be provided to donkeys during recovery from isoflurane anesthesia to prevent hypoxemia.

Cardiovascular and Gas Exchange Effects of Individualized Positive End-Expiratory Pressures in Cats Anesthetized With Isoflurane.

ObjectivesTo compare the effects of four levels of end-expiratory pressure [zero (ZEEP) and three levels of positive end-expiratory pressure (PEEP)] on the cardiovascular system and gas exchange of cats anesthetized with isoflurane and mechanically ventilated for 3 h with a tidal volume of 10 ml/kg.Study DesignProspective, randomized, controlled trial.AnimalsSix healthy male neutered purpose-bred cats.MethodsAnesthesia was induced with isoflurane and maintained at 1.3 minimum alveolar concentration. PEEP of maximal respiratory compliance (PEEPmaxCrs) was identified in a decremental PEEP titration, and cats were randomly ventilated for 3 h with one of the following end-expiratory pressures: ZEEP, PEEPmaxCrs minus 2 cmH2O (PEEPmaxCrs−2), PEEPmaxCrs, and PEEPmaxCrs plus 2 cmH2O (PEEPmaxCrs+2). Cardiovascular and gas exchange variables were recorded at 5, 30, 60, 120, and 180 min (T5 to T180, respectively) of ventilation and compared between and within ventilation treatments with mixed-model ANOVA followed by Dunnet's and Tukey's tests (normal distribution) or Friedman test followed by the Dunn's test (non-normal distribution). Significance to reject the null hypothesis was considered p < 0.05.ResultsMean arterial pressure (MAP—mmHg) was lower in PEEPmaxCrs+2 [63 (49–69); median (range)] when compared to ZEEP [71 (67–113)] at T5 and stroke index (ml/beat/kg) was lower in PEEPmaxCrs+2 (0.70 ± 0.20; mean ± SD) than in ZEEP (0.90 ± 0.20) at T60. Cardiac index, oxygen delivery index (DO2I), systemic vascular resistance index, and shunt fraction were not significantly different between treatments. The ratio between arterial partial pressure and inspired concentration of oxygen (PaO2/FIO2) was lower in ZEEP than in the PEEP treatments at various time points. At T180, DO2I was higher when compared to T5 in PEEPmaxCrs. Dopamine was required to maintain MAP higher than 60 mmHg in one cat during PEEPmaxCrs and in three cats during PEEPmaxCrs+2.ConclusionIn cats anesthetized with isoflurane and mechanically ventilated for 3 h, all levels of PEEP mildly improved gas exchange with no significant difference in DO2I when compared to ZEEP. The PEEP levels higher than PEEPmaxCrs−2 caused more cardiovascular depression, and dopamine was an effective treatment. A temporal increase in DO2I was observed in the cats ventilated with PEEPmaxCrs. The effects of these levels of PEEP on respiratory mechanics, ventilation-induced lung injury, as well as in obese and critically ill cats deserve future investigation for a better understanding of the clinical use of PEEP in this species.

The Effect of Pregabalin on the Minimum Alveolar Concentration of Sevoflurane: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial.

BackgroundPregabalin is commonly used perioperatively to reduce post-operative pain and opioid consumption and to prevent the development of chronic pain. It has been shown to reduce anesthetic consumption in balanced anesthesia, but studies investigating its effect on the minimum alveolar concentration (MAC) of volatile anesthetics are lacking. The aim of this study was to investigate the effect of two different doses of pregabalin on the MAC of sevoflurane.MethodsIn a randomized, double-blinded, placebo controlled clinical study, 75 patients were assigned to receive placebo, 300 mg pregabalin, or 150 mg pregabalin, as a capsule 1 h before anesthesia induction with sevoflurane only. After equilibration, the response to skin incision (movement vs. non-movement) was monitored. The MAC was assessed using an up- and down-titration method.ResultsThe MAC of sevoflurane was estimated as 2.16% (95% CI, 2.07–2.32%) in the placebo group, 1.44% (95% CI, 1.26–1.70%) in the 300 mg pregabalin group, and 1.81% (95% CI, 1.49–2.13%) in the 150 mg pregabalin group. We therefore report a 33% reduction in the MAC of sevoflurane in the 300 mg pregabalin group as compared to placebo. The MAC of the 150 mg pregabalin group was reduced by 16% as compared to placebo but was not statistically significant.ConclusionsThe administration of 300 mg pregabalin reduced the MAC of sevoflurane by 33%, while the administration of 150 mg pregabalin did not significantly reduce the MAC of sevoflurane. Pregabalin use led to a small reduction in post-operative pain levels but increased side effects in a dose-dependent manner.

Pupil response to painful stimuli during inhalation anaesthesia without opioids in children.

Pupil dilation reflex measured by a pupillometer is known to be a useful parameter for assessing the response to perioperative noxious stimuli. In children, pupillometer can reflect changes after painful stimuli during anaesthesia or guide anaesthesia to reduce opioid consumption. However, to date, there are no data regarding pupil response during inhalation anaesthesia with analgesia by intravenous acetaminophen in children. We planned a prospective, single-armed study of children aged between 3 and 12 years who underwent surgery under general anaesthesia. Anaesthesia was maintained by 1 minimum alveolar concentration (MAC) of sevoflurane, and 15 mg/kg of acetaminophen was administered. Patients' left eye was examined using a pupillometer after induction, before and after skin incision and train-of-four stimulus. Pupil diameter and other pupillometric parameters were recorded. Increase in heart rate by 15% was regarded as insufficient analgesia to skin incision and indicative powers of pupillometric parameters for insufficient analgesia were examined by receiver-operating characteristics. A total of 33 patients were included. Enlarged pupil, large increase in pupil diameter and low neurological pupil index (NPi) after skin incision were good indicators of insufficient analgesia for skin incision. Children with insufficient analgesia showed abnormal NPi value. However, increase in pupil diameter and decrease in NPi were observed even in patients without increase in the heart rate after the skin incision. We suggest dilation of the pupil and decrease in NPi can indicate response to noxious stimuli in children. Regardless of sufficiency of analgesia, pupil dilation and decrease in NPi were observed after skin incision in children under general anaesthesia with 1 MAC of sevoflurane and intravenous acetaminophen.

Minimum Alveolar Concentration of Isoflurane in Rats Chronically Treated with the Synthetic Cannabinoid WIN 55,212-2.

Simple SummaryThe minimum alveolar concentration of isoflurane (inhaled anesthetic required to prevent movement in 50% of subjects exposed to a supramaximal noxious stimulus) was determined in 24 male rats chronically treated with the synthetic cannabinoid WIN 55,212-2 to evaluate the interaction of isoflurane with chronically administered cannabinoid agonist. The minimum alveolar concentration was determined in one group without treatment, in rats treated for 21 days with WIN 55,212-2, and another group 8 days after stopping treatment for 21 days with cannabinoid. We believe it is necessary to study the effects of chronic consumption of these substances on the requirements of inhalation anesthetics in patients that will be submitted to general anesthesia. The administration for 21 days of WIN 55,212-2 increases the minimum alveolar concentration of isoflurane in rats; this effect does not disappear after 8 days of discontinuing treatment with the synthetic cannabinoid.The minimum alveolar concentration MAC of isoflurane was measured in rats chronically treated with WIN 55,212-2. Methods: The MAC of isoflurane was determined in 24 male rats from expiratory samples at time of tail clamping under the following conditions: without treatment MAC(ISO), in rats treated for 21 days with WIN 55,212-2 MAC(ISO + WIN55), and in rats 8 days after stopping treatment with WIN 55,212-2 (MACISO + WIN55 + 8D). Results: The MAC(ISO) was 1.32 ± 0.06. In the MAC(ISO + WIN55) group, the MAC increased to 1.69 ± 0.09 (28%, p-value ≤ (0.0001). Eight days after stopping treatment with WIN55, the MAC did not decrease significantly, 1.67 ± 0.07 (26%, p-value ≤ 0.0001). Conclusions: The administration of WIN 55,212-2 for 21 days increases the MAC of isoflurane in rats. This effect does not disappear 8 days after discontinuation of treatment with the synthetic cannabinoid.

The effect of a ketamine constant rate infusion on cardiovascular variables in sheep anesthetized at the minimum alveolar concentration of sevoflurane that blunts adrenergic responses.

To evaluate the effect of a constant rate infusion of ketamine on cardiac index (CI) in sheep, as estimated using noninvasive cardiac output (NICO) monitoring by partial carbon dioxide rebreathing, when anesthetized with sevoflurane at the previously determined minimum alveolar concentration that blunts adrenergic responses (MACBAR). 12 healthy Dorset-crossbred adult sheep. Sheep were anesthetized 2 times in a balanced placebo-controlled crossover design. Anesthesia was induced with sevoflurane delivered via a tight-fitting face mask and maintained at MACBAR. Following induction, sheep received either ketamine (1.5 mg/kg IV, followed by a constant rate infusion of 1.5 mg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (placebo). After an 8-day washout period, each sheep received the alternate treatment. NICO measurements were performed in triplicate 20 minutes after treatment administration and were converted to CI. Blood samples were collected prior to the start of NICO measurements for analysis of ketamine plasma concentrations. The paired t test was used to compare CI values between groups and the ketamine plasma concentrations with those achieved during the previous study. Mean ± SD CI of the ketamine and placebo treatments were 2.69 ± 0.65 and 2.57 ± 0.53 L/min/m2, respectively. No significant difference was found between the 2 treatments. Mean ketamine plasma concentration achieved prior to the NICO measurement was 1.37 ± 0.58 µg/mL, with no significant difference observed between the current and prior study. Ketamine, at the dose administered, did not significantly increase the CI in sheep when determined by partial carbon dioxide rebreathing.

Repeated Neonatal Exposure to Sevoflurane Induces Age-Dependent Impairments in Cognition and Synaptic Plasticity in Mice

Background: Sevoflurane is a volatile anesthetic that is widely used in pediatric anesthesia due to its low toxicity. However, whether neonatal exposure to sevoflurane induces long-lasting cognitive impairment remains unclear. It has been reported that neuronal injury is the main cause of sevoflurane-induced learning and memory disabilities in the development of brain. But, the specific mechanism is not well elucidated. The injury of synapse occurs earlier than that of neuronal cell in brain injury. The synaptic plasticity is involved in learning and memory. Methods: We compared the learning and memory ability of neonatal mice to sevoflurane for once or three times in vitro and synaptic plasticity as well as neuronal excitability in vivo. In this study, neonatal C57BL/6J mice were exposed to 3% sevoflurane for 2 h on postnatal day 7 (P7) or once daily for 3 consecutive days (P7/8/9). The Morris water maze test was performed to evaluate the cognitive performance on P31 and P61, respectively. Theta burst stimulation-induced long-term potentiation (LTP) was measured in acute hippocampal slices from P38 and P68 mice to assess the synaptic plasticity. Primary hippocampal neurons were isolated from 24-h-old mice and exposed to different doses of sevoflurane (1, 2, and 3 minimum alveolar anesthetic concentration [MAC]) for 6 h to examine the neuronal excitability. Results: The results showed that compared with the control, repeated exposure to sevoflurane resulted in significant cognitive impairment in adolescent mice, while showing no effect on adult mice. Repeated exposure to sevoflurane remarkably attenuated hippocampal LTP of adolescent mice, which turned to normal in adult mice. No significant difference of LTP was observed between control mice and one-dose sevoflurane-treated mice both in adolescent and adult mice. In primary hippocampal neurons, 2 MAC and 3 MAC sevoflurane delayed neuronal excitation and dose-dependently reduced the number of evoked action potentials compared with control. These effects disappeared after a 24-h recovery. Conclusions: These data suggested that sevoflurane may impair cognitive performance and neuronal plasticity when administered repeatedly or in a high MAC during infancy, which is noticeable during adolescence but alleviates during adulthood.

Serendipity: Being in the Right Place at the Right Time.

Effect of Nitrous Oxide and of Narcotic Premedication on the Alveolar Concentration Required for Anesthesia. By , Eger EI II. Anesthesiology 1964; 25:302-6. Hyperthermia during Anesthesia. By Saidman LJ, Havard ES, Eger EI II. JAMA 1964; 190:1029-32. The minimum alveolar concentration (MAC) of an inhaled anesthetic preventing movement in response to a surgical incision as a measure of equipotency was "invented" in 1964 at the University of California, San Francisco. The principal advantage of MAC is that it allows the pharmacologic effects of inhaled anesthetics to be compared against each other at a similar anesthetic depth. Thus, if the hemodynamic effect (hypotension, decreased cardiac output) of anesthetic "A" is greater than that of anesthetic "B," the anesthesiologist may elect to use "A" in patients with myocardial dysfunction. A rare side effect of a volatile anesthetic is that in some patients, malignant hyperthermia may occur with or without succinylcholine use. This phenomenon was detected in a patient in whom halothane MAC was being measured. The availability of the Severinghaus blood gas device allowed for the first ever measurement of the metabolic and respiratory acidemia that accompanies malignant hyperthermia.

A comparative randomized study of awareness during two anesthetic induction techniques in old aged patients using isolated forearm technique

Background &amp; Objective: Awareness under anesthesia is defined as intraoperative consciousness and/or postoperative recall of surgical events. The isolated forearm technique (IFT) is a technique that has the ability to assess consciousness of the external world through a verbal command during general anesthesia. It provides live information about the presence of consciousness.&#x0D; We compared inhalational induction technique versus intravenous induction technique regarding awareness during laryngoscopy and intubation in elderly patients.&#x0D; Design: A prospective, randomized trial&#x0D; Methodology: A total of 50 patients scheduled for elective surgery under general anesthesia; aged 60 to 80 years were recruited. Patients were randomized into either Group A (inhalational induction group) or Group B (total intravenous induction group). Awareness reaction using IFT technique was observed during laryngoscopy and intubation phase to identify awareness incidence. A patient was considered a responder if IFT score &gt; 2.&#x0D; Results: At laryngoscopy and intubation phase, 32% of cases had an awareness reaction in intravenous induction group (Group B): While in the inhalational induction group (Group A), only 8% of cases had an awareness reaction. Additionally, none of the patients, suffered from postoperative explicit recall as detected by modified Brice questionnaire (MBQ).&#x0D; Conclusions: On the basis of the results of our study, we conclude that intravenous induction of general anesthesia may subject old aged patients to a higher incidence of awareness when compared to inhalational induction technique.&#x0D; Trial Registration: NCT05019560&#x0D; Abbreviations: TIVA - Total intravenous anesthesia; IFT - Isolated forearm technique; MBQ - Modified Brice questionnaire; BISTM -Bispectral Index™; ETAC - End-tidal anesthetic concentration; MAC – Minimum alveolar concentration&#x0D; Key words: Awareness; The modified Brice questionnaire; Elderly patients; Isolated forearm technique; Sevoflurane; TIVA&#x0D; Citation: Ibrahim TH, Ayoub AH, Ibrahim IM, Ismaiel MAA, Mostafa RH. A comparative randomized study of awareness during two anesthetic induction techniques in old aged patients using isolated forearm technique. Anaesth. pain intensive care 2022;26(1):81-88.&#x0D; DOI: 10.35975/apic.v26i1.1772&#x0D; Received: November 14, 2021, Reviewed: December 18, 2021, Accepted: December 22, 2021

Cardioprotective Mechanisms of Interrupted Anesthetic Preconditioning with Sevoflurane in the Setting of Ischemia/Reperfusion Injury in Rats

Background: Anesthetic preconditioning (AP) is known to mimic ischemic preconditioning. The purpose of this study was to investigate the effects of an interrupted sevoflurane administration protocol on myocardial ischemia/reperfusion (I/R) injury. Methods: Male Wistar rats (n = 60) were ventilated for 30 min with room air (control group, CG) or with a mixture of air and sevoflurane (1 minimum alveolar concentration—MAC) in 5-min cycles, alternating with 5-min wash-out periods (preconditioned groups). Cytokines implicated in the AP response were measured. An (I/R) lesion was produced immediately after the sham intervention (CG) and preconditioning protocol (early AP group, EAPG) or 24 h after the intervention (late AP group, LAPG). The area of fibrosis, the degree of apoptosis and the number of c-kit+ cells was estimated for each group. Results: Cytokine levels were increased post AP. The area of fibrosis decreased in both EAPG and LAPG compared to the CG (p &lt; 0.0001). When compared to the CG, the degree of apoptosis was reduced in both LAPG (p = 0.006) and EAPG (p = 0.007) and the number of c-kit+ cells was the greatest for the LAPG (p &lt; 0.0001). Conclusions: Sevoflurane preconditioning, using an interrupted anesthesia protocol, is efficient in myocardial protection and could be beneficial to reduce perioperative or periprocedural ischemia in patients with increased cardiovascular risk.

Blood pressure nomograms for children undergoing general anesthesia, stratified by age and anesthetic type, using data from aretrospective cohort at a tertiary pediatric center.

Reference values for non-invasive blood pressure (NIBP) are available for children undergoing general anesthesia, but have not been analyzed by type of anesthetic. This study establishes age-specific pediatric NIBP reference values, stratified by anesthetic type: inhalational anesthesia (IHA), total intravenous anesthesia (TIVA), and mostly intravenous anesthesia (MIVA, an inhalational induction followed by intravenous maintenance of anesthesia). NIBP measurements were extracted from a de-identified vital signs database for children < 19years undergoing anesthesia between Jan/2013-Dec/2016, excluding cardiac surgery. We automatically rejected artifacts and randomly sampled 20 NIBP values per case. Anesthetic phase (induction/maintenance) was identified using operating room booking times for procedure start, and anesthetic types were identified based on intraoperative minimum alveolar concentration values in the different phases of the anesthetic. From 36,347 cases in our operating room booking system, we matched 24,457 cases with available vital signs. Of these, 20,613 (84%) had valid NIBP data and could be assigned to one anesthetic type: TIVA 11,819 [57%], IHA 4,752 [23%], and MIVA 4,042 [20%]. Mean NIBP during anesthesia increased with age, from median values of 48mmHg (TIVA), 45mmHg (IHA), and 41mmHg (MIVA) in neonates, to 70mmHg (TIVA), 68mmHg (IHA), and 64mmHg (MIVA) in 18-year-olds, respectively. In children < 1year, mean NIBP values were 4mmHg higher with TIVA than IHA (p < 0.001). These pediatric NIBP reference values contribute to ongoing debate about alarm limits based on age and anesthetic type, and may motivate prospective studies into the effects of different anesthesia regimes on vital signs.

Ethanol reduces the minimum alveolar concentration of sevoflurane in rats

A high number of trauma patients are under the influence of alcohol. Since many of them need immediate surgical procedures, it is imperative to be aware of the interaction of alcohol with general anesthesia. To counter challenges that arise from clinical studies, we designed an animal experiment in which 48 adult Wistar rats either received 1 g · kg−1 ethanol, 2 g · kg−1 ethanol or placebo via intraperitoneal application. Subsequently, they were anesthetized with an individual concentration of sevoflurane. The minimum alveolar concentration (MAC) of the different groups was assessed using Dixon’s up-and-down design and isotonic regression methods. The bootstrap estimate of the MAC of sevoflurane in the placebo group was 2.24 vol% (95% CI 1.97–2.94 vol%). In the low dose ethanol group, the bootstrap estimate was 1.65 vol% (95% CI 1.40–1.98 vol%), and in the high dose ethanol group, it was 1.08 vol% (95% CI 0.73–1.42 vol%). We therefore report that intraperitoneal application of 1 g · kg−1 or 2 g · kg−1 ethanol both resulted in a significant reduction of the MAC of sevoflurane in adult Wistar rats: by 26.3% and 51.8% respectively as compared to placebo.

Value of Ultrasonic Image Features in Diagnosis of Perinatal Outcomes of Severe Preeclampsia on account of Deep Learning Algorithm.

This study is aimed at discussing the value of ultrasonic image features in diagnosis of perinatal outcomes of severe preeclampsia on account of deep learning algorithm. 140 pregnant women singleton with severe preeclampsia were selected as the observation group. At the same time, 140 normal singleton pregnant women were selected as the control group. The hemodynamic indexes were detected by color Doppler ultrasound. The CNN algorithm was used to classify ultrasound images of two groups of pregnant women. The differential scanning calorimetry (DSC), mean pixel accuracy (MPA), and mean intersection of union (MIOU) values of CNN algorithm were 0.9410, 0.9228, and 0.8968, respectively. Accuracy, precision, recall, and F1-score were 93.44%, 95.13%, 95.09%, and 94.87%, respectively. The differences were statistically significant (P < 0.05). Compared with the normal control group, the umbilical artery (UA), uterine artery-systolic/diastolic (UTA-S/D), uterine artery (UTA), and digital video (DV) of pregnant women in the observation group were remarkably increased; the minimum alveolar effective concentration (MCA) of the observation group was obviously lower than the MCA of the control group, and the differences between groups were statistically valid (P < 0.05). Logistic regression analysis showed that UA-S/D, UA-resistance index (UA-RI), UTA-S/D, UTA-pulsatility index (UTA-PI), DV-peak velocity index for veins (DV-PVIV), and MCA-S/D were independent risk factors for the outcome of perinatal children with severe preeclampsia. In the perinatal management of severe epilepsy, the combination of the above blood flow indexes to select the appropriate delivery time had positive significance to improve the pregnancy outcome and reduce the perinatal mortality.

Is Ultrasound-Guided Transversus Abdominis Plane Block Superior to a Caudal Epidural or Wound Infiltration for Intraoperative and Postoperative Analgesia in Children Undergoing Unilateral Infraumbilical Surgery? A Double-blind Randomized Trial.

ABSTRACTBackground and Aim:Caudal block (CB) is the standard of care in pediatric surgeries. Ultrasound (USG) transversus abdominis plane (TAP) block has also been used as an effective regional anesthesia technique. We compared the duration of postoperative and intraoperative analgesia between TAP block, CB, and local wound infiltration (LI) in children undergoing unilateral infraumbilical abdominal surgery.Materials and Methods:One hundred and twenty children, 3–10 years old and American Society of Anesthesiologists Grade I and II, undergoing elective unilateral infraumbilical abdominal surgery were allocated to three groups. Group TAP: USG-guided TAP block with 0.5 ml/kg of 0.25% bupivacaine; Group CB: CB with 0.75 ml/kg of 0.25% bupivacaine; and Group LI: Local wound infiltration along the incision with 0.5 ml/kg of 0.25% bupivacaine. The primary outcome was the efficacy of postoperative analgesia using modified objective pain score (MOPS), and the secondary outcome was to determine intraoperative analgesia with fentanyl requirement and minimum alveolar concentration (MAC) hour of isoflurane among the three groups.Results:The MOPS was statistically better in Group TAP compared to group CB and group LI at 8 and 24 h postoperatively. The mean ± standard deviation duration of postoperative analgesia in groups CB, LI, and TAP was 6.84 ± 0.47, 2.3 ± 1.26, and 9.78 ± 1.02 h, respectively. The intraoperative requirement of fentanyl and MAC hour was least in Group CB.Conclusion:We found that USG-guided TAP block is a good alternative, with longer and effective postoperative analgesia compared to CB. However, the quality of intraoperative analgesia was best in group CB. Local infiltration was a poor alternative.

Comparison between Sevoflurane and Isoflurane for Controlled Hypotensive Anaesthesia in Patients undergoing Craniotomy for Supratentorial Intracranial Surgery: A Randomised Single-blinded Study

Introduction: The controlled hypotensive anaesthesia technique is widely used for decades to create a bloodless surgical field and decrease intraoperative blood loss during neurosurgical procedures. Inhalation agents like isoflurane and sevoflurane provide the benefit of being hypnotic and hypotensive agents at clinical concentrations and predictable dose-dependent effects made them popular in neurosurgery. Aim: To compare the effects of sevoflurane and isoflurane for producing controlled hypotensive anaesthesia in surgeries for supratentorial brain tumours. Materials and Methods: Sixty-six patients of either sex in the age group of 20-60 years, with American Society of Anaesthesiologists (ASA) Grade I and II posted for elective craniotomy for supratentorial brain tumour under general anaesthesia were enrolled for this study. Patients were randomly allocated to two aesthetic regimens: Group I received isoflurane 1 Minimum Alveolar Concentration (MAC), and Group S received sevoflurane 1 MAC. The Systolic Blood Pressure (SBP) was lowered to less than 100 mmHg before the skin incision and was maintained throughout the surgery.If the blood pressure was not maintained within the above-mentioned range, then injection propofol bolus dose of 20 mg was given intravenously. The quality of the surgical field, brain relaxation, blood loss, duration of surgery, and postoperative complications were compared. Time taken for onset and recovery of controlled hypotension and the requirement of propofol for maintaining controlled hypotension in both groups were also compared. Results: The group S had better brain relaxation (N=26 vs N=20), less blood loss (241.5±61.62 vs 380.65±203.9 mL), and a shorter duration of surgery (135.45±25.6 vs 171.4±60.5 minutes) than group I. Group S had a few patients who required propofol (5 vs 17) to maintain controlled hypotension. The mean time to achieve the target Mean Arterial Pressure (MAP) and time to recovery was faster in group S (10.55±2.54 minutes) vs 15.35±0.99 minutes in group I and 12.95±3.24 minutes in Group S vs 17.85±2.21 minutes in Group I, respectively; p&lt;0.001). Conclusion: Sevoflurane is a safer and more potent drug than isoflurane to achieve controlled hypotension during surgery for a supratentorial brain tumour.

Effectiveness of Low Dose Dexmedetomidine for an Oligaemic Field in Middle Ear Surgery: A Randomised Control Trial

Introduction: Microscopic middle ear surgeries are best done under hypotensive anaesthesia to provide an oligaemic field. Dexmedetomidine is an α2 agonist which produces hypotension by sympathetic response blockade. Aim: To study the effectiveness of low dose dexmedetomidine in providing an oligaemic field. The additional requirement of inhalational agent required to maintain the oligaemic field in the control group, intubation response and postoperative analgesia were also assessed. Materials and Methods: The randomised, placebo-controlled double-blind study was conducted by recruiting 48 patients in the study, who were divided into two groups i.e, study group (n=24) and placebo group (n=24). The study group received low dose dexmedetomidine infusion (0.5 μg/kg loading dose followed by 0.2 μg/kg/hr) and placebo group received weightadjusted saline. The quality of the surgical field was assessed on a score of 0-5. The Minimum Alveolar Concentration (MAC) of inhalational agent needed, postoperative sedation score and pain score were noted. All the data were recorded in Statistical Package for Social Sciences (SPSS) software, version 22.0. Results: The mean score of quality of the surgical field in the study group was 2.00±0.59, compared to 3.50±0.88 in the placebo group. The mean MAC of isoflurane was 1.32±0.31 in the placebo group and 0.85±0.23 in the study group (p-value=0.03). The study group had a Ramsay sedation score of 3.08±0.65 compared to 2.29±0.75 in the placebo group at 5 minutes after extubation (p-value &lt;0.001). The mean pain score in the dexmedetomidine group in 10 minutes postoperative period was 1.83±2.25, while in placebo group it was 3.25±1.96 (p-value=0.025). However, over the next 20-60 minutes postoperative period the pain score between the two groups were comparable, with no significant difference in analgesia, postoperative shivering and other side-effects. Conclusion: A low dose dexmedetomidine can effectively provide a bloodless field for middle ear microsurgical procedures.