Min Of Anesthesia Research Articles

Evaluation of the anesthetic depth and bispectral index during propofol sequential target-controlled infusion in dogs.

Background and Aim:The use of anesthetic infusions based on pharmacokinetic values associated with anesthetic plan and bispectral index in dogs have not been well-documented in the literature. This study aimed to evaluate the bispectral index (BIS) change based on pre-propofol and establish clinical anesthetic depth changes during propofol sequential target-controlled infusion (STCI) in dogs with a plasma target of 5 μg/mL.Materials and Methods:Twenty healthy male dogs aged 1-3 years and weighing 9.8-44 kg were recruited. These dogs were pre-medicated intramuscularly with methadone (0.2 mg/kg) and acepromazine (0.03 mg/kg). After 30 min, propofol anesthetic induction and maintenance were initiated using STCI according to dog pharmacokinetic (PK) parameters. Subsequently, the target plasma concentration of propofol was set at 5 μg/mL for both anesthetic induction and the 120 min maintenance. Then, TivaTrainer v.9.1 software was used to calculate anesthetic infusion rates in a TCI plasmatic concentration mode using the PKs model optimized by covariates for propofol TCI in dogs. The BIS value was recorded every 5 min from the beginning of induction until the end of anesthesia. Finally, analysis of variance was performed on numerical data using the Friedman test, followed by the Bonferroni adjustment (p<0.05).Results:A statistical difference was observed between the baseline BIS value (T0), with a median value of 84.5 (81-97), and BIS after every 15 min (T15) of inducing anesthesia. Surgical anesthetic depth was also reached in 18 of 20 dogs after 10 min of infusion and in all dogs after 20 min, with a median BIS value of 72 (53-89) at the time of surgical anesthesia depth. Results also showed no BIS variation (p<0.05) between anesthetic moments after anesthetic induction with a substantial amplitude of BIS in the surgical anesthetic depth. Moreover, the maximum depth of anesthesia in all dogs by clinical evaluation was reached after 20 min of anesthesia and then remained stable throughout the anesthetic period.Conclusion:This study suggested that most dogs (90%) attained a surgical depth of anesthesia within 15 min of STCI onset, with a plasma target of 5 μg/mL and no change in anesthetic depth throughout the period anesthesia lasted. Furthermore, median BIS values remained high even after dogs reached the surgical depth of anesthesia, indicating that the comparison of BIS values of dogs and humans should not be considered for classifying anesthetic and hypnotic depths in dogs.

Effects of Standard and Sustained-release Buprenorphine on the Minimum Alveolar Concentration of Isoflurane in C57BL/6 Mice.

Both standard and sustained-release injectable formulations of buprenorphine (Bup and BupSR, respectively) are used as preemptive analgesics, potentially affecting gas anesthetic requirements. This study tested the effects of Bup and BupSR on isoflurane requirements and confirmed that buprenorphine could reduce isoflurane requirements during a laparotomy in mice. We hypothesized that both Bup and BupSR would significantly decrease the required minimum alveolar concentration (MAC) of isoflurane. C57BL/6 mice received either isotonic crystalloid fluid (control), Bup (0.1 mg/kg), or BupSR (1.2 mg/kg) subcutaneously 10 min prior to the induction of anesthesia. Each anesthetized mouse was tested at 2 isoflurane concentrations. A 300-g noxious stimulus was applied at each isoflurane concentration, alternating between hindfeet. In addition, a subset of mice underwent terminal laparotomy or 60 min of anesthesia after injection with Bup, BupSR, or saline to ensure an appropriate surgical plane of anesthesia. Mice were maintained at the lowest isoflurane concentration that resulted in 100% of mice at a surgical plane from the aforementioned MAC experiments (control, 2.0%; Bup and BupSR, 1.7%). Analysis showed that both Bup and BupSR significantly decreased isoflurane requirements by 25.5% and 14.4%, respectively. The isoflurane MAC for the control injection was 1.80% ± 0.09%; whereas Bup and BupSR decreased MAC to 1.34% ± 0.08% and 1.54% ± 0.09%, respectively. Sex was not a significantly different between the injection groups during MAC determination. All of the mice that underwent surgery achieved a surgical plane of anesthesia on the prescribed regimen and recovered normally after discontinuation of isoflurane. Lastly, heart and respiratory rates did not differ between mice that underwent surgery and those that were anesthetized only. Bup and BupSR are MAC-sparing in male and female C57BL/6 mice and can be used for effective multimodal anesthesia.

Comparison of Use of Isoflurane or Sevoflurane for Anaesthesia Induced by Mask in Calves

Background: Inhalation anaesthesia is an effective and reliable general anaesthesia method for inactivity, analgesia, and unconsciousness in extensive surgical procedures. Although widely used, especially in small animals, there are very few studies investigated the reliability and superiority of inhalation anaesthesia in surgical procedures for ruminants. This study intended to evaluate the anaesthetic effects of isoflurane and sevoflurane in different surgical cases with endotracheal intubation following the induction of anaesthesia using a calve-specific facemask, which is not yet a routine option in cattle.Materials, Methods &amp; Results: The study was conducted on 14 calves, from new-born up to 3 months-old, that undergoing various surgical operations. The animals were divided into isoflurane and sevoflurane groups, and each group contained 7 animals. In all cases, atropine (0.04 mg/kg was administered intramusculer as premedication before 15 min from anaesthesia induction. For induction, the anaesthetic agent was given at an inspiratory concentration of 3-5% in the isoflurane group and at an inspiratory concentration of 5 - 7% in the sevoflurane group during 5 min via mask at 15min after atropine administration. In both groups, endotracheal intubation was performed (about 1-3 min) after of general anaesthesia symptoms starting. At 5min after induction, anaesthesia was continued at 1.5 - 3% in the isoflurane group and at 2.5 - 4% in the sevoflurane group during operation. The animals were monitored during anaesthesia and, anaesthetic effect, reaction of the calve, pronounced side effects, Heart Rate (HR), Systolic Arterial Blood Pressure (SABP), Diastolic Arterial Blood Pressure (DABP), Mean Arterial Blood Pressure (MABP), Respiration Rate (RR), Pulse Rate (PR), Arterial Oxygen Saturation (SpO2) were recorded at before anaesthesia, the premedication period, 5, 15, 30, 45, 60, 75 and 90min of anaesthesia. During anaesthesia, from the clinical parameters, mucosal capillary refilling time was evaluated by applying finger pressure to the oral mucosa. Mucous membrane color was determined by observing the oral mucosa. The time for palpebral reflex and swallowing reflex disappearance was measured and processed into individual forms. Anaesthesia induction and reanimation times were determined and recorded in the forms. After the operation, the return of the swallowing reflex and the time to stand up were recorded. During the operation, urination, defecation, salivation, vomiting, animal reactions, the shape and duration of the reamination period were recorded. In the isoflurane group anaesthesia induction was 3.71 ± 0.28 min, head movements started and came to the sterno- abdominal position at 4.57 ± 0.36 min, got up at 8.71 ± 0.42 min without assistance, meanwhile. In sevoflurane group, anaesthesia induction was 2.57 ± 0.20 min, head movements started and came to the sterno- abdominal position at 3.86 ± 0.40 min, the time to stand up was determined as 6.43 ± 0.29 min. During anaesthesia, HR, SABP, DABP, MABP, RR, PR, SpO2 findings were within physiological acceptable limits in 2 groups. In terms of indicators, there were no obvious differences in either group. The results revealed no significant difference between groups during anaesthesia.Discussion: The isoflurane and sevoflurane anaesthesia used in this study provided an adequate anaesthetic effect in calves characterized by adequate analgesia and muscle relaxation without any complications. The results of our study revealed that there was no significant difference between isoflurane and sevoflurane in calves. Both anaesthetic agents can be used safely for general anaesthesia in calves.

Comparison of Clinical and Hemodynamic Effects of Isoflurane and Sevoflurane Anesthesia in Calves

Background: Inhalation anesthesia is the preferred method for use on many animal species, including ruminants, due to its superiority over the injectable anesthetics. The most commonly used inhalation anesthetics are isoflurane and sevoflurane The aim of the study was to investigate the effects of isoflurane and sevoflurane anesthesia on the cardiovascular system of calves.Materials, Methods &amp; Results: A total of 20 calves (11 male, 9 female) between 1 and 6 months in age and 50 to 85 kg in body weight were used. The calves were divided randomly into two groups of 10 each, with one group being administered isoflurane and the other sevoflurane. An intramuscular dosage of 0.1 mg/kg of xylazine was administered to the calves as premedication. Induction was performed 10 min after calves were given an intramuscular dosage of 4 mg/kg of ketamine. Inhalation anesthesia was maintained with isoflurane or sevoflurane in 100% oxygen saturation. Before anesthesia, after induction and at intervals of 5, 10, 15, 20, 25, 30, 45, and 60 min of anesthesia, the body temperature, heart rate, and respiratory rate of the calves were recorded. Additionally, before anesthesia, after induction and at intervals of 15, 30, 45, and 60 min of anesthesia, serum electrolyte (Na+, Ca++, K+, Mg++) and blood gases (pH, pCO2, pO2, HCO3-, TCO2, O2Sat, HCT) were evaluated from blood samples taken from both groups. The second derivation, durations and amplitudes of the P and T waves, the durations and amplitudes of the QRS complex, and the durations of PQ and QT intervals were evaluated on the ECGs recorded before anesthesia, after induction and during anesthesia. Following anesthesia termination, the extubation time and the time it took for straightening of the head and standing up were recorded. Decrease in heart rate and body temperature were found significant in two of the groups. Decrease in respiratory rate compared to initial values after premedication was statistically significant for both groups. However, during anesthesia, an increase occurred. This incresae in respiration rate was not statistically significant compared to initial values. The incease in the values of pCO2, pO2, HCO3 and the decrease in the values of pH and Hct comparing the initial values was found statistically significant in both groups.Discussion: In ruminants, isoflurane has an induction concentration of 3-5% and an anesthetic concentration of 1.5-3%, while sevoflurane has an induction concentration of 4-6% and an anesthetic concentration of 2.5-4%. In this study, the concentration of isoflurane was 2.3% (2-5) and the of sevoflurane was 4.07% (3-5) for surgery. In the isoflurane group, extubation, straightening of the head and standing up times were 12.40 ± 3.77 min, 20.4 ± 1.57 min, and 30.80 ± 1.89 min, respectively. In the sevoflurane group, extubation, straightening of the head and standing up times were 13.40 ± 4.99, 19.2 ± 1.49, and 28.0 ± 1.83 min, respectively. Although the calves in the isoflurane group were extubated earlier than those of the sevoflurane group, the time elapsed for straightening of the head and standing up were longer than that of the sevoflurane group. The anesthesia protocol provided a smooth anesthetic administration, general anesthesia and awakening. In conclusion, the effects of isoflurane and sevoflurane anesthesia on the cardiovascular and respiratory system were similar, and although the changes that emerged during anesthesia were statistically significant, it was nonetheless found that the changes were within the physiological limits.

A Comparasion of Laboratory and Cardiopulmonary Effects of Desflurane, Detomidine and Medetomidine Anaesthetic Combinations in Horses

Background: Equine anesthesia morbidity and mortality rates are greater than in other domestic animals because of hypotension and hypoventilation. The important features desired in general anesthesia for horses are a rapid effect, rapid emergence and balanced anesthesia. The long duration of action of currently used anesthetic agents cause various complications in horses. The aim of the present study was to compare the clinical effects of combination of the anesthetics desflurane, detomidine and medetomidine in horses.Materials, Methods &amp; Results: Eight healthy mixed-breed horses (four males and four females) with weighing 275 ± 56 kg [mean ± standard deviation (SD)] and aged 6.8 ± 5 years [(mean ± SD)] were used for this study. The horses were placed into one of four groups: group I (detomidine-desflurane), group II (detomidine-desflurane-atipamezole), group III (medetomidinedesflurane), or group IV (medetomidine-desflurane-atipamezole). Horses were rested for 15 days before each group starts to study. Intravenous detomidine (25 µg/kg) was used for premedication in groups I and II, and intravenous medetomidine (7 µg/ kg) was used for premedication in groups III and IV. Ketamine hydrocholoride (2 mg/kg) and midazolam (0.03 mg/kg) were intravenously administered in the same syringe to induce anesthesia. After induction of anesthesia, horses were placed in the left lateral recumbent position, and the trachea was intubated with a cuffed endotracheal tube with an internal diameter of 28 mm. The endotracheal tube was attached to a large animal circle breathing system anesthesia machine, and anesthesia was maintained with desflurane for 90 min. The initial dosage of desflurane was 14% + 4 L O2/min, and was reduced by 2% every 10 min over the first 30 min of anesthesia. After 30 min, the desflurane dose was changed to 8% + 4 L, which was maintained until the end of anesthesia (90 min). After 90 min, the administration of desflurane was discontinued, and all animals were supported by O2, with groups II and IV receiving 0.06 mg/kg atipamezole in addition to oxygen. Anaesthetic action times, hematological parameters, blood gas levels, electrolyte levels, biochemical values, electrocardiography values and end-tidal carbon dioxide volume were measured before, during, at the end of, and 24 h after anesthesia.Discussion: In this study, medetomidine (7 µg/kg) and detomidine (25 µg/kg) were intravenously administered, which was adequate and suitable for sedating horses. At the end of anesthesia, 0.06 mg/kg atipamezole was intravenously administered in groups II and IV. However, atipamezole did not affect the clinical parameters. Stress, excitement, fear, catecholamine exchange in blood circulation, hyperglycemia, and hypoxia can all cause changes in venous blood parameters. These are potential reasons for the changes in venous blood parameters (i.e., WBC and Hb) observed at the beginning of and during anesthesia in the present study. During and after the anesthetic period, serum biochemical values can be different from baseline values. They are dependent on the effects of anesthetic agents. During anesthesia, the decrease and increase of biochemical values stabilize the changes in the enzyme system that develops because of the effects of anesthetic agents. In the present study, it was considered that the changes in the biochemical values aimed to stabilize the changes induced by anesthesia. Regarding the electrolyte parameters evaluated in the study, there was a statistical difference detected in Na values between 90 min after induction of anesthesia and 24 h after induction of anesthesia in group IV. However, in previous studies, the changes in Na values did not influence the cardiac pressure during general anesthesia. In our study, significant changes were not seen in any electrolyte parameters except Na, and atrioventricular block was not detected in ECG traces. Generally, decreased ETCO2 levels are evidence of lung perfusion deficiency. It depends on the effects of anesthetic agents on the cardiopulmonary, cardiovascular, and respiratory systems. In particular, the higher pressure and dose of desflurane supress respiratory system. Oxygen supplementation in general anesthesia increases respiratory rate, but a-2 agonists and ketamine-midazolam effects can eliminate the increasing respiratory rate in general anesthesia.

Risk Factors for Pressure Ulcers at the Ala of Nose in Oral Surgery.

A quality review revealed pressure ulcers at the ala of nose in 16 cases (2.2%) over 3 years. We therefore retrospectively investigated the risk factors for alar pressure ulcers from nasal tubes. Male gender was the highest risk factor (odds ratio = 9.1411; 95% confidence interval = 1.680-170.58), and the second highest risk factor was duration of anesthesia (odds ratio = 1.0048/min of anesthesia; 95% confidence interval = 1.0034-1.0065). Male gender and duration of anesthesia appear to be risk factors for nasal tube pressure ulcers at the ala of nose in patients.

Continuous noninvasive cardiac output in children: is this the next generation of operating room monitors? Initial experience in 402 pediatric patients.

Electrical Cardiometry(™) (EC) estimates cardiac parameters by measuring changes in thoracic electrical bioimpedance during the cardiac cycle. The ICON(®), using four electrocardiogram electrodes (EKG), estimates the maximum rate of change of impedance to peak aortic blood acceleration (based on the premise that red blood cells change from random orientation during diastole (high impedance) to an aligned state during systole (low impedance)). To determine whether continuous cardiac output (CO) data provide additional information to current anesthesia monitors that is useful to practitioners. After IRB approval and verbal consent, 402 children were enrolled. Data were uploaded to our anesthesia record at one-minute intervals. Ten-second measurements (averaged over the previous 20 heart beats) were downloaded to separate files for later comparison with routine OR monitors. Data from 374 were in the final cohort (loss of signal or improper lead placement); 292,012 measurements during 58,049 min of anesthesia were made in these children (1 day to 19 years and 1 to 107 kg). Four events had a ≥25% reduction in cardiac index at least 1 min before a clinically important change in other monitored parameters; 18 events in 14 children confirmed manifestations of other hemodynamic measures; eight events may have represented artifacts because the observed measurements did not seem to fit the clinical parameters of the other monitors; three other events documented decreased stroke index with extreme tachycardia. Electrical cardiometry provides real-time cardiovascular information regarding developing hemodynamic events and successfully tracked the rapid response to interventions in children of all sizes. Intervention decisions must be based on the combined data from all monitors and the clinical situation. Our experience suggests that this type of monitor may be an important addition to real-time hemodynamic monitoring.

General anaesthesia versus combined spinal epidural anaesthesia in the presence of mild to moderate pericardial effusion: A study of volunteers undergoing caesarean section

Study objectiveThis study evaluated the haemodynamic effects of general anaesthesia versus combined spinal epidural anaesthesia in patients undergoing caesarean section in the presence of mild to moderate pericardial effusion.DesignA prospective randomized study.SettingThe study setting included a hospital where a surgical team performed elective caesarean section in the presence of mild to moderate pericardial effusion.Patients and interventionsThirty healthy patients were randomly divided into two groups, general anaesthesia (GA) (group I) and combined spinal epidural (CSE) anaesthesia (group II).Measurements and main resultsHeart rate, central venous pressure, mean arterial blood pressure, and pulmonary capillary wedge pressure were measured 10 min before anaesthesia, after 20 and 30 min of anaesthesia, and 30 min after recovery. Blood loss was significantly lower in group II [465.33 (72.78) ml] as compared to group I [548.20 (22.73) ml]. The pain score in group II was significantly lesser [1.66 (0.72)], than in group I [2.60 (0.73)]. The HR was significantly higher in group I as compared to that in group II at 20 and 30 min after anaesthesia, and 30 min after surgery, being 81.53 (2.72), 94.80 (3.12) and 82.8 (2.85) (beats/min), respectively. However, the CVP was significantly higher in the group I at 20 and 30 min after induction, being 8.40 (0.63) and 7.80 (0.67) (cmH2O) respectively. The MAP was significantly higher in group II than in group I at 20 and 30 min after induction, being 80.86 (1.30) and 81.00 (1.00) (mmHg) respectively. The PCWA was significantly higher in group I compared to group II at 20 and 30 min after induction, being 10.13 (1.35) and 11.80 (0.94) (mmHg), respectively.ConclusionCSE anaesthesia appeared to be more advantageous, in patients undergoing caesarean section with mild to moderate pericardial effusion, with less haemodynamic changes, decreased blood loss, and better postoperative analgesia than general anaesthesia patients.

Hemodynamic effects of a right lumbar–pelvic wedge during spinal anesthesia for cesarean section

Background Aortocaval compression is a major cause of maternal hypotension. A randomized controlled trial was designed to determine the effectiveness of a mechanical intervention using a right lumbar–pelvic wedge in preventing hypotension after spinal anesthesia for cesarean delivery. Methods Eighty healthy women undergoing elective cesarean section were randomly allocated immediately after spinal blockade to either a lumbar–pelvic wedge positioned under the right posterior–superior iliac crest (Wedge group, n = 40) or the complete supine position (Supine group, n = 40). Hemodynamic values, vasopressor consumption and adverse effects were collected during the surgical procedure. Hypotension was defined as a reduction in systolic blood pressure of 25% from baseline. Patient allocation, management and data collection were performed by a single unblinded anesthetist. Results There was no difference in the incidence of hypotension between the two groups (42.5% vs. 50%, P = 0.51). During the first 5 min, blood pressure decreased less in the Wedge group. There were significant differences in median [interquartile range] vasopressor requirements between the Wedge group and the Supine group (1 [0–2] vs. 3 [1–4] mg, P < 0.01) and in nausea during the procedure (6 vs. 22 patients, P < 0.01). Conclusion In our study population the use of right lumbar–pelvic wedge was not effective in reducing the incidence of hypotension during spinal anesthesia for cesarean section. Patients in whom the wedge was used had higher systolic blood pressure values during the first 5 min of anesthesia and fewer episodes of nausea. The risk of hypotension remains substantial.

Tolazoline antagonises ketamine–xylazine anaesthesia in an endangered Black buck (Antilope cervicapra)

Seventy-seven anaesthetic events were carried out in 22 captive adult Black bucks (Antilope cervicapra) of either sex with a combination of 2 mg kg−1 ketamine hydrochloride with 0.25 mg kg−1 xylazine hydrochloride using a dart delivered from a blowpipe. Randomised anaesthetised animals received an intravenous injection of either yohimbine hydrochloride (0.125 or 0.25 mg kg−1) or tolazoline hydrochloride (1 or 2 mg kg−1) after 30–40 min of anaesthesia to antagonise the anaesthetic effects. Ketamine–xylazine induced smooth, rapid and reliable anaesthesia within 5–7 min of darting with no clinical adverse effects and causalities during or post-anaesthesia. Yohimbine failed to antagonise the anaesthetic effects of ketamine–xylazine in the Black buck. On the other hand, tolazoline was found to be very effective in hastening recovery in dose-dependent manner within 0.5–1.5 min. This study documents the first report of ketamine–xylazine anaesthesia and its antagonism by tolazoline in captive Black buck.

EFFECT OF ANAESTHETIC AGENTS ON P‐WAVE DISPERSION ON THE ELECTROCARDIOGRAM: COMPARISON OF PROPOFOL AND DESFLURANE

Anaesthetics influence cardiac electrical activity by various mechanisms; thus, they may have pro-arrhythmic or anti-arrhythmic actions. Increased P-wave dispersion is associated with a risk of paroxysmal atrial fibrillation. The aim of the present study was to analyse the impact of propofol and desflurane on changes in P wave dispersion, which may reflect the anti-arrhythmic effects of these drugs. Fifty patients undergoing scheduled surgery were included in the study. Patients were divided into two equal groups: a propofol group and a desflurane group. Patients in the propofol group were initially administered 2.5 mg/kg propofol, followed by infusion of 6 mg/kg per h propofol. Anaesthesia in the desflurane group was achieved using inhalation induction, with concentrations up to 8-12.5 vol%. When signs of adequate anaesthesia were observed, the concentration of desflurane was reduced to 6 vol%. An electrocardiogram (ECG) was obtained before induction and then again 1, 3 and 5 min after the initiation of propofol infusion or the induction of anaesthesia in the desflurane group; additional measurements were performed after tracheal intubation. P-wave dispersion was assessed by differences in maximal and minimal P-wave duration on a 12-lead ECG. P-wave dispersion did not change over time in the desflurane group. In the propofol group, there was a significant decrease in P-wave dispersion after 3 and 5 min of anaesthesia. Significant differences were observed between study groups after 1, 3 and 5 min of anaesthesia, and disappeared after tracheal intubation. Mean and maximal P-wave duration did not change in either group. In conclusion, propofol decreases P-wave dispersion and this seems to be connected with the anti-arrhythmic properties of the drug.

Effects of 2-phenoxyethanol Anaesthesia on Haematological Profile on Common Carp (Cyprinus carpio) and Rainbow Trout (Oncorhynchus mykiss)

The aim of this study was to assess changes in haematological profile of common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) after the exposure to anaesthetic 2-phenoxyethanol. The haematological profile was assessed before, immediately after 10 min of anaesthesia and 24 h after the anaesthesia with recommended concentration of 0.30 ml l-1 2-phenoxyethanol. The 10-min exposure to 2-phenoxyethanol of common carp caused the significant increase (p &lt; 0.01) in the haematocrit value and relative and actual count of monocytes immediately after the anaesthesia. These values returned back to normal within 24 hours. In rainbow trout, 2-phenoxyethanol anaesthesia had no effect on the haematological profile. Results of the examinations suggest that the use of 2-phenoxyethanol at the concentration of 0.30 ml l-1 does not cause irreversible damage of the blood in common carp and rainbow trout.

CHEMICAL IMMOBILIZATION OF RHEBOK (PELEA CAPREOLUS) WITH CARFENTANIL–XYLAZINE OR ETORPHINE–XYLAZINE

Twelve adult rhebok (Pelea capreolus) were immobilized using a combination of 0.4 mg/kg xylazine and either 0.01 mg/kg of carfentanil (n = 6) or 0.01 mg/kg etorphine (n = 6), delivered i.m. using a remote injection system. Induction and recovery times, heart rate, respiratory rate, rectal temperature, oxygen saturation, end-tidal CO2 (ETCO2), anesthetic depth, indirect blood pressure, and arterial blood gases were recorded. Rhebok were not intubated but nasal oxygen was administered. Forty minutes after induction, anesthesia was antagonized with naltrexone and yohimbine. Mean initial heart rate was significantly higher in the carfentanil group than in the etorphine group. Mean initial oxygen saturation was consistent with hypoxia in both the carfentanil group and the etorphine group. In both groups, arterial pH decreased and partial pressure of carbon dioxide increased during the first 15 min of anesthesia, and values were similar in both groups. These findings were consistent with respiratory acidosis and decreased ventilation. Values for respiratory rate, temperature, oxygen saturation, ETCO2, and blood pressure were similar for both groups at all time periods. During the first 5 min of anesthesia, rhebok in the carfentanil group were more responsive to stimuli than rhebok in the etorphine group. After administration of antagonists, time to first arousal was significantly shorter in the etorphine group than in the carfentanil group. Although cardiopulmonary values were similar for the two groups, rhebok in the carfentanil group were at a comparatively lighter plane of anesthesia, and some individuals in this group required additional manual and chemical restraint for medical procedures to be performed. In conclusion, for captive adult rhebok, 0.01 mg/kg of etorphine and 0.4 mg/kg of xylazine are recommended over 0.01 mg/kg carfentanil and 0.4 mg/kg xylazine because of qualitatively better anesthetic episodes and shorter recovery times.

Hemorrhage during Isoflurane–Nitrous Oxide Anesthesia

The objective of this study was to determine whether endothelin-A receptor blockade (ETAB) impairs hemodynamic and hormonal regulation compared with controls and angiotensin II receptor blockade (AT1B) during hypotensive hemorrhage in dogs under isoflurane-nitrous oxide anesthesia. Six dogs were studied in four protocols: (1) control experiments (controls); (2) ETA blockade using ABT-627 (ETAB); (3) AT1 blockade using losartan (AT1B); and (4) combined AT1B and ETAB (AT1B + ETAB). After a 30-min awake period, isoflurane-nitrous oxide anesthesia was established (1.3 minimum anesthetic concentration). After 60 min of anesthesia, 20 ml blood/kg body weight was withdrawn within 5 min, and the dogs were observed for another hour. Thereafter, the blood was retransfused, and the dogs were observed for a final hour. Anesthesia: Cardiac output decreased in all protocols, whereas mean arterial pressure decreased more in AT1B and AT1B + ETAB than in controls and ETAB. Hemorrhage: After 60 min, cardiac output had decreased less in controls than in all other protocols. Mean arterial pressure decreased more during ETAB than in controls, but most severely during AT1B and AT1B + ETAB. Angiotensin II increased further only in controls and ETAB, whereas vasopressin and catecholamines increased similarly in all protocols. Retransfusion: Mean arterial pressure remained below controls in all protocols but was lowest when the AT1 receptor was blocked. Cardiac output fully recovered in all but the ETAB protocol. ETAB impairs long-term hemodynamic regulation after hemorrhage and retransfusion during anesthesia despite an activation of vasoconstrictive hormones. This suggests that endothelins have a role in long-term cardiovascular regulation. AT1B impairs both short- and long-term blood pressure regulation during anesthesia and after hemorrhage.

Combined Medetomidine and Ketamine for Short-term Anaesthesia in Ferrets – a Clinical Study

Combined Medetomidine and Ketamine for Short-term Anaesthesia in Ferrets – a Clinical Study

Changes in hemodynamic variables and catecholamine levels after rapid increase in sevoflurane or isoflurane concentration with or without nitrous oxide under endotracheal intubation.

Rapid increases in concentrations of isoflurane and desflurane in oxygen have been shown to increase sympathetic activity. The aim of this study was to determine whether concomitant administration of nitrous oxide would reduce these sympathomimetic effects of volatile anesthetics. Eighty healthy patients in whom the trachea was intubated and mechanically ventilated were given 15 min of anesthesia with either N(2)O (67%)-O(2)-sevoflurane (GOS), O(2)-sevoflurane (OS), N(2)O (67%)-O(2)-isoflurane (GOI), or O(2)-isoflurane (OI) (n = 20 per group). The inspired concentration of sevoflurane was 0.85% (0.5 minimum alveolar concentration [MAC]), and that of isoflurane was 0.6% (0.5 MAC). Fifteen minutes after endotracheal intubation, baseline and arterial blood sample data were obtained. Immediately after that, a sudden administration of 2.9 MAC volatile anesthetics was performed. Systolic and diastolic arterial pressures, heart rate, and end-tidal carbon dioxide concentration were obtained at 0.5, 1, 1.5, 2, 3, 4, and 5 min after that. To measure catecholamine levels, arterial blood samples were obtained 2 and 5 min after the trial started. Except for the OI group, systolic and diastolic arterial pressure progressively decreased after the abrupt increase in the concentration of volatile anesthetics. Except for the OS group, the heart rate increased after the abrupt increase in the concentration of volatile anesthetics. In the OI group, the end-tidal concentration of carbon dioxide increased at 0.5 and 1 min, suggesting that a slight hyperdynamic state occurred. However, it decreased progressively after the abrupt increase in volatile anesthetic concentration in the other groups. Plasma norepinephrine levels increased progressively in all groups. Even if nitrous oxide was added to isoflurane or sevoflurane, the increase in heart rate could not be avoided. Contrary to previous reports, severe hyperdynamic circulation was not observed after a rapid increase in isoflurane concentration.

The estimation of inspired desflurane concentration in a low-flow system.

We have examined the predictability of inspired desflurane concentration during low-flow anaesthesia using a to-and-fro breathing system. Twenty-two adult patients requiring mechanical ventilation of the lungs during surgery took part in the study. Using a fresh gas flow of 1 l.min-1, the ratio of inspired desflurane concentration to desflurane vaporizer setting was found to be approximately 0.75 after 9 min of anaesthesia and at 2 l.min-1 fresh gas flow the ratio was approximately 0.9 after 2 min of anaesthesia. These ratios were maintained throughout the procedure, except for a few minutes following each change in vaporizer setting.

The estimation of inspired isoflurane concentration in a low‐flow system

We have examined the predictability of inspired isoflurane concentration during low-flow anaesthesia using a to-and-fro breathing system. Twenty one adult patients requiring mechanical ventilation of the lungs during surgery took part in this study. Using a fresh gas flow of 2 l.min-1, the ratio of inspired isoflurane concentration to isoflurane vaporizer setting was found to be approximately 4/5th after 5 min of anaesthesia. The ratio was maintained throughout the procedure, except for a few minutes following each change in vaporizer setting.

Influence of serum concentrations of catecholamines and i.v. or volatile anaesthesia on evoked electromyography in the hand

We have examined the correlation between serum concentrations of catecholamines and the evoked electromyographic (EEMG) response from the first dorsal interosseous muscle of the hand in 20 patients during minor surgery under propofol or enflurane anaesthesia without neuromuscular blocking drugs. The supinated forearm, with the wrist fully extended, was strapped firmly to an armboard and immobilized with adhesive tape. In the propofol group, the mean EEMG response to the first stimulus in the train-of-four (T1) decreased to 83.0% (95% confidence intervals (CI) 78.7-87.3%) of baseline, while in the enflurane group the mean EEMG T1 response decreased to 84.0% (95% CI 81.6-86.4%) of baseline. The decrease in the EEMG response occurred over 20 min and did not correlate with plasma concentrations of adrenaline or noradrenaline (correlation coefficients all < 0.26). We conclude that the decrease in EEMG response during the first 30 min of anaesthesia occurred during both i.v. and inhalation anaesthesia, and that changes in plasma concentrations of catecholamines did not cause the decrease in the EEMG response.

Utilisation de l'halothane en circuit semi-fermé

Halothane was administered to 10 ASA or 11 patients undergoing elective peripheral surgery. The vaporizer was included in the delivery gas line of the semiclosed system. Löwe's square root of time model of uptake was used to calculate the required doses of halothane. In order to reach an alveolar concentration corresponding to 1.3 MAC, 0.5 vol % of halothane (1.3 MAC) combined with 60 vol % of nitrous oxide (0.6 MAC) were administered at a fresh of 20 ml·kg −1. The ventilation controlled in order to maintain end-tidal CO 2 partial pressure at a 5 vol %. Inspiratory halothane concentration was measured during the inspiratory plateau. The alveolar fraction was defined as being the mean end expiratory concentration. The latter was well above the theoretical values during the first 9 min of anaesthesia (0.85 % at the 4 th min). This concentration then decreased progressively, becoming less than the expected value after 15 min (0.4 % at the 30 th min). Löwe's model would therefore seem to lead to a gross overestimation of the amount of anaesthetic vapour to be delivered to a patient at the beginning of anaesthesia, and an underestimation thereafter.