Different Stages Of Anesthesia Research Articles

Putting the Pacific fat sleeper Dormitator latifrons (Pisces: Eleotridae) to sleep: effects of clove oil and lidocaine anesthetic.

Among the different handling techniques in aquaculture, the use of anesthetics has had a growing interest focused on guaranteeing animal welfare, and reducing possible stress situations during general handling. The aim of this study was to present the use of eugenol and lidocaine with non-invasive anesthesia procedures in Dormitator latifrons, in which the different stages of anesthesia (induction and recovery) were determined. One hundred and twenty healthy fish of average weight of 73.59 ± 13.53 g and standard length of 17 ± 1.36 cm were used. The experimental fish were subjected to fasting for 24 h prior to the tests. Five fish were subjected to eugenol (25, 50, 100, and 200 µL/L), and lidocaine (100, 200, 300, and 400 mg/L), in triplicate. The time to reach deep and recovery anesthesia were recorded and the data analyzed using ANOVA (α= 0.05). Organisms exposed to anesthetics evidenced early episodes of fast, short-distance swimming (initial hyperactivity) for short periods of time. Survival was 100% with both compounds and concentrations. Fish exposed to a eugenol concentration of 200 µL/L had longer anesthesia times and took longer time to recover (P<0.05). The most effective concentrations for eugenol and lidocaine were of 200 µL/L and 400 µL/L in juvenile fish, promoting rapid inductions, without compromising the conditions for the recovery of the fish. This work provides practical information for handling and transportation D. latiforns with the least possible stress and ensuring animal welfare.

A Deep Learning Framework for Anesthesia Depth Prediction from Drug Infusion History.

In the target-controlled infusion (TCI) of propofol and remifentanil intravenous anesthesia, accurate prediction of the depth of anesthesia (DOA) is very challenging. Patients with different physiological characteristics have inconsistent pharmacodynamic responses during different stages of anesthesia. For example, in TCI, older adults transition smoothly from the induction period to the maintenance period, while younger adults are more prone to anesthetic awareness, resulting in different DOA data distributions among patients. To address these problems, a deep learning framework that incorporates domain adaptation and knowledge distillation and uses propofol and remifentanil doses at historical moments to continuously predict the bispectral index (BIS) is proposed in this paper. Specifically, a modified adaptive recurrent neural network (AdaRNN) is adopted to address data distribution differences among patients. Moreover, a knowledge distillation pipeline is developed to train the prediction network by enabling it to learn intermediate feature representations of the teacher network. The experimental results show that our method exhibits better performance than existing approaches during all anesthetic phases in the TCI of propofol and remifentanil intravenous anesthesia. In particular, our method outperforms some state-of-the-art methods in terms of root mean square error and mean absolute error by 1 and 0.8, respectively, in the internal dataset as well as in the publicly available dataset.

Intraoperative Awareness in Patients Undergoing Cardiac Surgery in an Academic Center in the North of Iran.

Coronary artery bypass grafting (CABG) has distinctive characteristics that may increase the risk of awareness during general anesthesia (AGA). This study was conducted to assess the incidence of AGA in cardiac surgery in an academic hospital in Guilan, Iran. This descriptive cross-sectional study was performed in Dr. Heshmat Hospital in Rasht, Iran. Eligible patients candidates for CABG were enrolled in the survey in 2022. After surgery, when the patient was cooperative enough, a questionnaire including demographic data and specialized questions related to different stages of anesthesia was completed via face-to-face interviews. The data were analyzed using IBM SPSS Statistics 21 with chi-square, Fisher's exact, and t-test. The data from 322 patients were analyzed, of whom 14 (4.3%) experienced AGA. Among them, the "feeling of fear and anxiety" reported by 9 (39.1%) cases was the most common awareness state. "Dreaming during surgery and anesthesia" and "feeling unable to move during anesthesia,", each reported by 6 (26.1%) cases, were the other common types of awareness state. None of the demographic data had a significant association with the occurrence of AGA. The incidence of AGA during CABG was almost acceptable according to the credible evidence.

Intraoperative Awareness During Cesarean Delivery Under General Anesthesia

Background: General anesthesia (GA) for caesarean section (CS) has distinctive characteristics that may increase the risk of awareness during GA (AGA). Objectives: The aim of this study was to investigate the incidence of unintended awareness during GA (AGA) in CS. Materials &amp; Methods: This cross-sectional descriptive study was performed in Alzahra Hospital in Rasht City, Iran. Eligible women with term pregnancy candidates for CS under GA were enrolled in this survey from May 2018 to August 2021. After delivery, a questionnaire including demographic data and questions related to different stages of anesthesia was completed via a faceto- face interview. The collected data were analyzed using repeated measurement, the Chi-square, Fisher exact, and t-test in SPSS v. 21. Results: The data from 174 women were analyzed, and 12 (6.9%) experienced AGA. Among them, dreaming and feeling the manipulation of the surgical area (27.8%) were the most common reported awareness states. Body mass index had a significant (P=0.034) relationship with AGA, but age (P=0.843), the level of education (P=0.714), history of anesthesia (P=0.552), 5-minute Apgar score (P=0.49), and surgery time (P=0.686) had no significant relationship with AGA. Conclusion: The incidence of AGA during CS was almost close to the high limit established by the credible evidence, and a significant number of the women were not in completely acceptable conditions. Therefore, the management of GA for CS should be revised in this academic hospital.

Effect of general inhalational anesthesia on intraocular pressure measurements in normal and glaucomatous children.

To investigate the agreement between the intraocular pressure (IOP) measurements in the awake condition and under different stages of general inhalational anesthesia using sevoflurane in both glaucomatous and normal children. A prospective study was performed on 43 glaucomatous children and 30 age-matched controls. Baseline IOP of one eye was measured immediately before general anesthesia using Perkins tonometer and then re-measured under light, intermediate, and deep anesthesia, and then after intubation. Depth of anesthesia was determined using bispectral index pediatric sensor. The agreement between the IOP measurements before and during different stages of anesthesia was analyzed using Bland-Altman plots. Systematic and proportionate deviations between the IOP measurements were analyzed. The mean age was 58.6 ± 41.99months. The mean IOP was significantly lower at all stages of anesthesia in both groups. The coefficient of variation was over 20% in all measurements under anesthesia. For all IOP measurements during anesthesia, the limits of agreement were > 7mmHg difference in the control group and > 20mmHg in the glaucomatous group. The best agreement was with the IOP measurement after intubation (mean limit of agreement of -1.4mmHg, 1.96s range, -8.8-6mm Hg) in the control group and with the IOP measurement under intermediate anesthesia (mean limit of agreement of -4.2mmHg, 1.96s range, -15.1-6.8mm Hg) in the glaucomatous group. Inhalational anesthesia has variable effects on IOP measurement at all stages of anesthesia. Caution should be taken when extrapolating the true IOP from these measurements.

Comparison of the effects of butorphanol–midazolam–medetomidine and butorphanol–azaperone–medetomidine in wild common palm civets (Paradoxurus musangus)

ObjectiveTo assess the efficacy of butorphanol–azaperone–medetomidine (BAM) and butorphanol–midazolam–medetomidine (BMM) protocols for immobilization of wild common palm civets (Paradoxurus musangus) with subsequent antagonization with atipamezole. Study designProspective, randomized, blinded clinical trial. AnimalsA total of 40 adult wild common palm civets, 24 female and 16 male, weighing 1.5–3.4 kg. MethodsThe civets were randomly assigned for anesthesia with butorphanol, azaperone and medetomidine (0.6, 0.6 and 0.2 mg kg–1, respectively; group BAM) or with butorphanol, midazolam and medetomidine (0.3, 0.4 and 0.1 mg kg–1, respectively; group BMM) intramuscularly (IM) in a squeeze cage. When adequately relaxed, the trachea was intubated for oxygen administration. Physiological variables were recorded every 5 minutes after intubation. Following morphometric measurements, sampling, microchipping and parasite treatment, medetomidine was reversed with atipamezole at 1.0 or 0.5 mg kg–1 IM to groups BAM and BMM, respectively. Physiological variables and times to reach the different stages of anesthesia were compared between groups. ResultsOnset time of sedation and recumbency was similar in both groups; time to achieve complete relaxation and tracheal intubation was longer in group BAM. Supplementation with isoflurane was required to enable intubation in five civets in group BAM and one civet in group BMM. All civets in group BAM required topical lidocaine to facilitate intubation. End-tidal carbon dioxide partial pressure was lower in group BAM, but heart rate, respiratory rate, rectal temperature, peripheral hemoglobin oxygen saturation and mean arterial blood pressure were not different. All civets in both groups recovered well following administration of atipamezole. Conclusions and clinical relevanceBoth BAM and BMM combinations were effective for immobilizing wild common palm civets. The BMM combination had the advantage of producing complete relaxation that allowed intubation more rapidly.

Гемодинаміка при корекції лійкоподібної деформації грудної клітки за Nuss

Introduction. The hemodynamic parameters during the Nuss procedure for repair of pectus excavatum are under the influence of surgical procedures and anesthetic components especially regional blocks. The aim of the study: analysing the hemodynamic parameters during the Nuss procedure for repair of pectus excavatum under the combination of general anesthesia with different regional analgesia techniques. Materials and methods. The observative prospective study inclueded 60 adolescents (boys/girls=47/13) undergone the Nuss procedure for repair of pectus excavatum under the combination of general anesthesia with different types of regional blocks. The patients were randomized into three groups (n=20 in each) according to the regional analgesia technique: standart epidural anaesthesia in the dermatome of maximal deformity (SEA), high epidural anaesthesia in Th2-Th3 level (HEA) and bilateral paravertebral anaesthesia (PVA). The deformity severity by Haller index in all patients was 3.9 [3.6–4.1]. The blood pressure (BP) and heart rate (HR) were analyzed at different stages of anesthesia and surgery. Results. SEA resulted to significant derease in BP up to 30% compared to initial level before anesthesia. In the HEA group the decrease in BP was moderate and in PVA group the BP did not decrease at all. The sternal elevation and applying capnothorax increased BP without increasing HR. The bar rotation provided a little hemodynamic change in spite of being the most traumatic moment of such surgery. Under PVA HR was moderately increased but BP was almost unchanged, and the intraoperative infusion volume was the smallest in PVA group. HEA provided more stable hemodynamics in comparison to SEA. At the end of surgery hemodynamic parameters almost the same as initial before surgery. Conclusions. During the Nuss procedure for pectus excavatum repair the blood pressure decreased significantly under the standart epidural anaesthesia in the dermatome of maximal deformity, moderately – under the high epidural anaesthesia in Th2-Th3 level and was stable under the bilateral paravertebral anaesthesia. HR decreased under epidural blocks but not under PVA. The sternal elevation and applying capnothorax increased BP. The initial hemodynamic parameters before surgery did not correlate with the severity of deformity according to the Haller index. The study was conducted in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the institution. Informed consent of parents and children was obtained for the study. The author declares no conflict of interest. Key words: hemodynamics, pectus excavatum, Nuss procedure, epidural anaesthesia, paravertebral anaesthesia.

The effect of fresh gas flow during induction of anaesthesia on sevoflurane usage: a quality improvement study.

Reducing fresh gas flow during inhalational anaesthesia results in cost savings and decreases environmental impact. We are interested in the influence of fresh gas flow on the early (induction) phase of overall fresh gas flow and vapour consumption. This stage is often excluded in studies of fresh gas flow. Data were collected from 3199 sevoflurane anaesthetics over an 11-month period in four operating theatres. We determined fresh gas flow at different stages of anaesthesia, and developed an explanatory model for the influence of the 'induction' period. Following a three-month collection of baseline data we emphasised the importance of the early phase to our department repeatedly over a two-week period. We explored the relationship between fresh gas flow and total vapour usage, and used a simple mathematical model to explore the effect of changes in the fresh gas flow and duration of the 'induction' phase. Mean fresh gas flow was 1.15l.min-1 in the baseline period and 0.91l.min-1 in the twomonths following our educational effort (p=0.0005). In the following sixmonths, mean fresh gas flow was 1.17l.min-1 (p=0.7726 compared with baseline). These results were driven by changes in both fresh gas flow and duration of the initial high-flow period. We found some correlation (R2 =0.85) between overall fresh gas flow and vapour consumption; a 1l.min-1 increase in fresh gas flow consumes an additional 18ml.hr-1 of liquid sevoflurane. This preliminary study demonstrates that an episode of high fresh gas flow at the start of anaesthesia has a large and modifiable effect on overall fresh gas flow and vapour consumption. We also confirmed the linear relationship between fresh gas flow and vapour usage.

Development, Optimization, and Validation of the HS-SPME/GC-MS Method for the Residual Determination of Menthol in Fish

In this study, the development, validation, and residual determination of the menthol anesthetic in fish fillets, cultivated in the pisciculture station of the Federal University of Lavras. The fish were submitted to anesthesia with menthol in different concentrations (50, 75, 100, 125, and 150 μg mL−1) and slaughtered at the times of 0, 12, 24, and 48 h after anesthesia. The objective of the study was to detect traces of anesthetic and to determine the time required for clearance of menthol from animal tissue, stipulating a residual time for elimination of contamination. The headspace solid-phase microextraction (HS-SPME) technique coupled with gas chromatography and mass spectrometry (GC-MS) was applied to residual determination. In order to optimize the methodology, the central composite design (CCD) was employed and, analyzing the obtained response surfaces, it was verified that the optimal working condition was 3 g of salt, 20 min of extraction, and a temperature of 50 °C. The proposed method was validated by obtaining the limits of detection (LD) and quantification (LQ) of 0.015 and 0.046 μg kg−1, respectively, precision and accuracy within the acceptable. The methodology was applied for the residual determination of menthol in fish from tilapia species, in different stages of anesthesia, with a residual period of 48 h for total elimination of this compound in fish tissues. With the obtained results, it is verified that the methodology developed using HS-SPME was efficient for determination of menthol in fish tissues.

Anaesthetic responses and reflexes to propofol and its combination in swine

To determine the effectiveness of propofol alone (P), and the combination of xylazine-propofol (XP), xylazineketamine (XK), xylazine-thiopentone (XT), anaesthetic protocols were studied in randomly selected 16 healthy indigenous pigs of either sexes, age 12 to 15 months and weight ranging from 12 to 16 kg. The responses of propofol and the combinations in different stages of anaesthesia were closely monitored. Various reflex responses and muscle tenacity were also observed concurrently during the period of anaesthesia. The study found the shortest (0.29±0.02 min) induction period with XT anaesthesia and the longest (2.95±0.21 min) by XK; whereas, induction of anaesthesia with P and XP was 0.4±0.08 and 0.41±0.08 min respectively. The time required for maximum depth of anaesthesia was the shortest in P (7.50±0.65 min) than the combinations. However, the anaesthetic protocol with XP produced the highest (65.25±3.30 min) duration of anaesthesia than the shortest (10.75±1.75 min) extent with P. Moreover, time to recovery from anaesthesia was higher (83.25±2.14 min) in XT and shorter (18.50±1.32 min) in P protocol. Good muscle relaxation was observed in XP, XK and XT combinations. Palpebral, conjunctival, jaw, tail and digital reflexes were almost absent in XP and XT combinations. The study concluded that propofol itself is a safe anaesthetic for short surgical interventions and its combination with xylazine is to be recommended for prolonged surgical procedures in swine.

Impact of inducing general anesthesia with Propiscin (etomidate) on the physiology and health of European perch (Perca fluviatilis L.)

The aim of the study was to describe the course and timing of the different stages of anesthesia induced with Propiscin (etomidate) on juvenile European perch (experiment I) and to describe the effect of immersing specimens of this species had on selected hematological and biochemical parameters (experiment II). The study was conducted on material with body weights (BW) of 162.98 (experiment I) and 171.60 g (experiment II). In experiment I, general anesthesia was induced with two different anesthetic concentrations (1 or 2 ml l−1; anesthesia time 10 min). In experiment II, blood was drawn for hematological and biochemical analyses from the fish that had been exposed to anesthetic immersion baths with two different concentrations of Propiscin (1 and 2 ml l−1) and for different exposure times (3 and 10 min). Blood samples were collected immediately following immersion (0 h) and 24 h later (24 h). Specimens that were immersed at the higher concentration of anesthetic achieved subsequent stages of general anesthesia two times faster (P ≤ 0.05). However, during recovery, some statistically significant differences were observed, but these lasted only until stage I was achieved. Among the hematological parameters (0 h), significant differences were observed in hematocrit (HCT) and mean corpuscular volume (MCV), while among the biochemical determinations (0 h), statistically significant differences were noted in the concentrations of glucose, calcium, lactate, and ammonia. After 24 h, the levels of these parameters in all fish groups returned to initial values. The hematological and biochemical tests conducted permit concluding that the anesthetic tested, at the concentrations (1 and 2 ml l−1) and the exposure times of up to 10 min at which it was tested, is safe and can be used successfully to induce general anesthesia in perch.

Linear and non-linear heart rate metrics for the assessment of anaesthetists’ workload during general anaesthesia

BackgroundExcessive workload may impact the anaesthetists’ ability to adequately process information during clinical practice in the operation room and may result in inaccurate situational awareness and performance. This exploratory study investigated heart rate (HR), linear and non-linear heart rate variability (HRV) metrics and subjective ratings scales for the assessment of workload associated with the anaesthesia stages induction, maintenance and emergence. MethodsHR and HRV metrics were calculated based on five min segments from each of the three anaesthesia stages. The area under the receiver operating characteristics curve (AUC) of the investigated metrics was calculated to assess their ability to discriminate between the stages of anaesthesia. Additionally, a multiparametric approach based on logistic regression models was performed to further evaluate whether linear or non-linear heart rate metrics are suitable for the assessment of workload. ResultsMean HR and several linear and non-linear HRV metrics including subjective workload ratings differed significantly between stages of anaesthesia. Permutation Entropy (PeEn, AUC=0.828) and mean HR (AUC=0.826) discriminated best between the anaesthesia stages induction and maintenance. In the multiparametric approach using logistic regression models, the model based on non-linear heart rate metrics provided a higher AUC compared with the models based on linear metrics. ConclusionsIn this exploratory study based on short ECG segment analysis, PeEn and HR seem to be promising to separate workload levels between different stages of anaesthesia. The multiparametric analysis of the regression models favours non-linear heart rate metrics over linear metrics.

Using a pulse oximeter to determine clinical depth of anesthesia-investigation of the utility of the perfusion index.

Peripheral vasodilation is a well-recognized side effect of general anesthesia, and induces changes in the amplitude of the pulse plethysmograph (PPG) waveform. This can be continuously quantitaed using the Perfusion Index (PI), a ratio of the pulsatile to nonpulsatile signal amplitude in the PPG waveform. We hypothesized that the perfusion index would rise with the induction of anesthesia in children, and fall with emergence, and performed a prospective, observational study to test this. Our primary aim was to test whether the different clinical stages of anesthesia were associated with changes in the perfusion index, and the secondary aim was to test the correlation between the normalized perfusion index and the MAC value. Twenty-one patients between the ages of 1 and 18 undergoing minor procedures with no anticipated painful stimuli were recruited. Patients with significant illnesses were excluded. Data collection commenced with a preinduction baseline, and data were collected continuously, with event marking, until completion of the anesthesia and removal of the pulse oximeter. Data collected included perfusion index, heart rate, and anesthetic gas concentration values. A normalized perfusion index was calculated by subtracting the initial baseline perfusion index value from all perfusion index values, allowing changes, from a standardized initial baseline value of zero, to be analyzed. During induction, the mean normalized perfusion index rose from 0.0 to 4.2, and then declined to 0.470 when the patients returned to consciousness. P < 0.001 using repeated measures anova test. The normalized perfusion index was correlated with MAC values (r2 = 0.33, 95% CI 0.18-0.47, P < 0.01). The perfusion index changed significantly during different stages of anesthesia. There is a significant correlation between the perfusion index, measured by pulse oximetry, and the MAC value, in pediatric patients undergoing minor procedures.

Indução anestésica do extrato aquoso de cunambí, Clibadium surinamense linn para a realização de biometrias em tambaquis, Colossoma macropomum

RESUMO A biometria é uma etapa importante do processo de manejo realizada em peixes durante o cultivo. Porem essa pratica expõe os peixes a elevados níveis de estresses que podem ocasionar a debilidade ou ate mesmo a mortalidade dos peixes. O uso de anestésicos naturais como o cunambi, Clibadium surinamense é uma alternativa para minimizar os danos provocados pelo manuseio durante a biometria. O objetivo deste trabalho foi avaliar o cunambí como anestésico para juvenis de tambaqui. Para tanto, foram utilizadas três concentrações de extrato aquoso da planta (0,5, 1,5 e 2,5ml/L). Foram expostos individualmente 3 peixes (17,24g ± 14,01 e 9,18 ± 0,91cm) para cada tratamento e observados o tempo de indução e recuperação anestésica. O tratamento de 0,5ml/L necessitou de maior tempo para atingir o estágio de indução desejado de sedação profunda (7,4 minutos), contudo houve diferença significativa em relação às concentrações de 1,5 e 2,5ml/L. A concentração de 0,5 ml/L é a ideal para o procedimento de biometria e breve manejo, pois apesar da demora em induzir o peixe aos diferentes estágios de anestesia, provoca uma rápida recuperação (8,62 minutos) em relação a outros tratamentos 1,5ml/L (16,6 minutos) e 2,5 ml/L (23,7min).

Utilização de eugenol como anestésico em juvenis de Geophagus brasiliensis

The eugenol is the active ingredient of clove oil and it has shown to be effective and safe as fish anesthetic. In this study were evaluated the effects of different concentrations of eugenol for anesthesia, recovery time, blood glucose and hematocrit percentage of pearl cichlid (Geophagus brasiliensis) juveniles. Concentrations of 50, 80, 100, 120, 150, 170 and 200 mg L-1 eugenol were evaluated in terms of time to achieve the different stages of anesthesia and recovery in a completely randomized design (CRD) with 12 repetitions. These results were tested using the Kruskal-Wallis test with subsequent Dunn test. The evaluated concentrations had anesthetic action of the deep induction 172.57 ± 25 s (50 mg L-1) and the period of full recovery of 516.25 ± 102 s (200 mg L-1), with statistical difference between the treatments at all the stages. The eugenol effect on blood glucose and on hematocrit percentage at 0 h after deep anesthesia was evaluated for concentrations of 0; 50; 80; 100; 150; 200 mg L-1, in a completely randomized design with five replications, and the results were assessed by One-Way ANOVA. Glucose and percentage of hematocrit: no statistically significant differences (P>0.05) were observed for these variables. All concentrations of eugenol showed to be effective as an anesthetic for G. brasiliensis and did not affect the survival, blood glucose and the percentage of hematocrit. To minimize adverse effects and achieve faster recovery is indicate the use of 50-80 mg L-1 of eugenol for pearl cichlid juveniles.

Monitoring Depth of Anaesthesia Using Auditory Brainstem Response: An Exploratory Clinical Study

Purpose:Various depth-of-anaesthesia monitors are available, but their trustworthiness is questioned. The aim of this study was to investigate brainstem auditory-evoked potentials during general anaesthesia using a specific audiometry method named SensoDetect Brainstem Evoked Response Audiometry (SD-BERA). Methods:Seven patients with American Society of Anaesthesiologists physical status I and II scheduled for elective orthopaedic surgery were assigned. Brainstem auditory evoked responses were recorded at different stages of anaesthesia. Bispectral index and end-tidal tension of Sevoflurane were measured at the same time. Results:The index (%) from pre-anaesthesia to anaesthesia were significantly reduced 100 [0–0] vs. 53 [49–72], respectively (p=0.0156). At extubation the index were set back to normal level with a significant increase from anaesthetized state, 102 [78–135] (p=0.0156). No significant difference could be observed between pre-anaesthesia and at extubation (p=0.6875).

A technical description of a novel pharmacological anesthesia robot

To control the three components of general anesthesia (hypnosis, analgesia, and neuromuscular blockade), an automated closed-loop, anesthesia-drug delivery system (McSleepy) was developed. Bispectral index was used as the control variable for hypnosis, the analgoscore for analgesia, and phonomyography for neuromuscular blockade. McSleepy can be used to control the induction, maintenance and emergence from general anesthesia. To do so, a large touch screen is used to provide a user friendly interface, permitting bidirectional communication: the user giving information about the different stages of anesthesia, and the system prompting the anesthesiologist to perform certain actions such as mask ventilation, intubation or waking-up the patient using audio clips with voice commands. Several safety features were implemented to provide a secure and reliable anesthesia. Preliminary results of 15 patients are presented in this paper. Evaluation of McSleepy was done through an assessment of its clinical performance and using Varvel's performance indices. The system was found to be clinically useful by providing good precision in drug administration and reliable results for the duration of a general anesthesia.

O uso do óleo de cravo como anestésico em juvenis avançados de tilápia do Nilo (Oreochromis niloticus) - doi: 10.4025/actascianimsci.v34i2.13022

Handling of live fish is inevitable in fish farms and causes a number of adverse physiological reactions, thus requiring the use of anesthetics. The main goal of the present work was to evaluate the efficiency of clove oil as an anesthetic for juvenile tilapia (approximately 55 g and 13 cm) during handling. In the first experiment, fishes were exposed to an anesthetic bath at six concentrations (80, 100, 150, 200, 250 and 300 mg L-1). Subsequently, the induction time was assessed for different stages of anesthesia. In the second experiment, different times of exposure to anesthesia were tested, aiming to assess the safety margin of the anesthetic. Finally, we evaluated the responses to stress after exposure to 250 mg L-1 anesthesia. The following parameters were tested: cortisol, glucose, hematocrit, hemoglobin, and plasma sodium and potassium levels. The concentration of 250 mg L-1 of clove oil is the most appropriate to induce surgical anesthesia, and 150 mg L-1 for biometrics and brief handling. Anesthesia at the ideal concentration for 10 minutes did not result in severe stress. Only blood glucose and hematocrit were affected after anesthesia.

Trial‐to‐trial correlation between thalamic sensory response and global EEG activity

Thalamic gating of sensory inputs to the cortex varies with behavioral conditions, such as sleep-wake cycles, or with different stages of anesthesia. Behavioral conditions in turn are accompanied by stereotypic spectral content of the EEG. In the rodent somatosensory system, the receptive field size of the ventral posteromedial thalamic nucleus (VPM) shrinks when anesthesia is deepened. Here we examined whether evoked thalamic responses are correlated with global EEG activity on a fine time scale of a few seconds. Trial-by-trial analysis of responses of VPM cells to whisker stimulation in lightly anesthetized rats indicated that increased EEG power in the delta band (1-4 Hz) was accompanied by a small, but highly significant, reduction in spontaneous and evoked thalamic firing. The opposite effect was found for the gamma EEG band (30-50 Hz). These significant correlations were not accompanied by an apparent change in the size of the receptive fields and were not EEG phase-related. The correlation between EEG and firing rate was observed only in neurons that responded to multiple whiskers and was higher for the non-principal whiskers. Importantly, the contributions of the two EEG bands to the modulation of VPM responses were to a large extent independent of each other. Our findings suggest that information conveyed by different whiskers can be rapidly modulated according to the global brain activity.

The effect of hypernatremic status on anesthesia

Hypernatremia is defined as plasma Na+ concentration above 145 meq/L (often due to absolute body water loss and not to total sodium excess). Nevertheless, when kidney damage is present, as occurs in renal diseases, hepatic cirrhosis and congestive heart failure, total body sodium can be increased. The present study evaluates the relationship between hypernatremia and response to anesthetic drug ketamine. For this purpose, 3 groups of rats, each consisting of 5 male Wistar rats ,weighing 200 ± 20 g, were chosen for the experiment. The control group used Zanjan city water during the study while the other two groups were maintained on 1% and 2% NaCl solutions. After 2 weeks, the response to anesthetic drug, ketamine (125 mg/kg) was studied. Results: The average serum sodium level in the rats of control group was 131 meq/L. For those on 1 and 2 percent solutions it was 148 meq/L and 165 meq/L. Sensitivity to the anesthetic drug, the speed of recovery from different stages of anesthesia and its total time was significantly increased in the test groups in comparison with the control group. This rise was quite conspicuous in those using 2 percent solutions. The mortality rate in the group using 1 percent solution was 20 percent and that of 2 percent solution was 60 percent. When hypernatremia develops, due to dehydration or any other reason, the anesthetic drug dosage should be reduced because hypernatremia increases the sensitivity to anesthesia and lengthens the recovery time from different stags of it. If the dose reduction is not practiced in hypernatremia, the increased mortality and drug side effects will most probably be encountered.