Influence of Bispectral Index Monitoring on Isoflurane Minimum Alveolar Concentration in Off Pump Cardiac Surgeries

Off pump CABG is the most commonly performed cardiac surgical procedure involving multi vessel grafting through median sternotomy. Approach of lateral and posterior walls of heart for grafting, necessitates need for lifting or tilting heart producing elevated atrial pressures, fall in cardiac output and thus profound hypotension. Maintaining delicate balance between myocardial oxygen demand and supply is crucial to prevent myocardial insults and associated sequelae for which the mean arterial pressure is maintained >70 mmHg to facilitate adequate coronary perfusion pressure achieved by infusion of vasopressors like dobutamine and increased preload. Another strategy adopted by anaesthesiologist to limit this hypotension is by reducing isoflurane and thus cardiac surgical patients are prone for awareness. Awareness is the explicit recall of sensory perceptions during anaesthesia.METHODSWe studied 40 patients with ASA physical status II & III, between age group of 18 to 65 years scheduled for elective off pump CABG after institutional ethical committee clearance and written informed consent. Patients were randomly allocated into two groups of 20 each. Group 1 (isoflurane in oxygen given with BIS maintained at 55+/-5) and Group 2 (isoflurane in oxygen given without BIS).Comparison of the two groups was done in terms of gender, age, height, weight, heart rate, hemodynamics, dial concentration, minimum alveolar concentration, drugs consumed, time to extubation and intraoperative awareness. Results were statistically analyzed using independent t test, chi square test and Fischer exact test. Data was presented in terms of mean, median and standard deviation. The 'p' value of <0.05 was considered significant.RESULTSHeart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure were higher in Group 1 compared to Group 2. The dial concentration and minimum alveolar concentration were found to be statistically significant 5 minutes after intubation upto 4.5 hours of the cardiac surgical procedure with 'p' value <0.05. Amount of midazolam and propofol used in Group 1 was higher when compared to Group 2 while there was no statistical significance with use of opioid (fentanyl) or muscle relaxant (pancuronium). Time to extubation and intraoperative awareness were comparable between both the groups.CONCLUSIONSBIS monitoring reduces amount of isoflurane used along with the prevention of awareness in cardiac surgical patients. It helps not only the anaesthesiologist but also the other operation theatre personnel by preventing environmental pollution.

Determination of the minimum alveolar concentration of sevoflurane in patients diagnosed as gastric car-cinoma and treated with neoadjuvant chemotherapy / 临床麻醉学杂志

Objective To determine the minimum alveolar concentration (MAC)of sevoflurane for blunting the responses to surgical incision in 50% adult patients diagnosed as gastric carcinoma and treated with neoadjuvant chemotherapy.Methods Twenty-five ASA physical statusⅠor Ⅱ,and aged 30-50 years patients (14 males and 11 females)diagnosed with gastric carcinoma were enrolled.At least 1 month before the operation,all these patients received 2 cycles (1 chemotherapy cycle was 14 days)of chemotherapy including oxaliplatin and tegafur.At first,the anesthesia induc-tion was started by inhaling 6% sevoflurane.After the patient lost consciousness,the endotracheal in-tubation was performed.And then,the end tidal sevoflurane concentration was adjusted to the target concentration and maintained stable for 15 min.After that,the surgical incision was executed.The Dixon's up-and-down method was used to calculate the MAC.The initial end tidal sevoflurane con-centration was 2.2% and it was increased or decreased by 0.2% in the next patient according to the surgical incision response.If the surgical incision response was positive,the end tidal sevoflurane con-centration was increased;if the surgical incision response was negative,the end tidal sevoflurane con-centration was decreased.The midpoint from negative response to positive response was set as the balance point and the mean value of the concentrations of sevoflurane at all the balance points were calculated as MAC.Results Minor physical activity occurred when the surgical incision started.No body twisting,eye opening or intraoperative awareness occurred.Body moving occurred in 11 patients (44%)when the surgical incision started.The end tidal sevoflurane concentration for blunting the re-sponses to surgical incision in 50% adult patients diagnosed as gastric carcinoma and treated with neo-adjuvant chemotherapy was 1.52%,and the 95% CI was 1.37%-1.65%.Conclusion The MAC of sevoflurane for blunting the responses to surgical incision in 50% adult patients diagnosed as gastric carcinoma and treated with neoadjuvant chemotherapy is 1.52%.

Effects of different concentrations of sevoflurane inhalation combined with propofol anesthesia on rocuronium pharmacodynamics / 天津医药

Objective To investigate the effect of different concentrations of sevoflurane inhalation combined with pro?pofol anesthesia on rocuronium pharmacodynamics. Methods Sixty-seven patients, who underwent elective abdominal op?eration in Tianjin Medical University General Hospital from Nov. 2014 to Feb. 2015, were randomly allocated to three groups:propofol combined 0.5 minimum alveolar concentration (MAC) end-tidal concentration of sevoflurane (group Ⅰ, 24 cases), propofol combined 0.75 MAC end-tidal concentration of sevoflurane (group Ⅱ, 20 cases) and propofol combined 1 MAC end-tidal concentration of sevoflurane (groupⅢ, 23 cases). All those patients were given midazolam 0.05 mg/kg, sufen? tanil 0.3μg/kg, etomidate 0.3 mg/kg for anesthesia induction. Rocuronium was given through the T1 mode of Closed-loop muscle relaxant infusion system and infused by 2ED95(0.6 mg/kg). The following variables were recorded:average consump?tion dosage of rocuronium, recovery index, averaged consumption dosage of propofol and remifentanil. Results The aver?aged consumption dosage of rocuronium was decreased in the three groups in turn[(9.71 ± 2.38 vs 7.50 ± 0.98 vs 6.90 ± 1.14)μg·kg-1·min-1,F=18.562,P0.05]. The average consumption dosage of propofol and remifentanil were lower in groupⅢthan those of groupⅠand groupⅡ(P<0.05). Conclusion High concentration of sevoflurane can enhance neuromuscular blockage effect of rocuronium, and decrease the consumption dosage of propofol and remifentanil.

Determination of sevoflurane minimum alveolar concentration in newborn and adult rats / 临床麻醉学杂志

Objective To measure and compare sevoflurane minimum alveolar concentration (MAC)in newborn and adult rats.Methods The rats were divided into newborn rat (6-8 days) group (25 cases)and adult rat (8-10 weeks)group (25 cases).All rats were settled in the self-made device for anesthesia with inhaled sevoflurane,and the tails of rats were exposed out of the device. Sevoflurane was given via an anesthesia machine.Up-and-down method and clamping tail stimulus were applied to measure the MAC values of sevoflurane in the two groups.1.5% of sevoflurane was set as the initial concentration,and± 0.2% as adjustable gradient.A positive or negative response was judged by clamping tail stimulus in a 20 minutes interval.The mean MAC value of all rats in each group was defined as the MAC value.Results The MAC value of newborn rats was (2.58 ± 0.1 1)%,and the MAC value of adult rats was (2.32 ±0.13)%.A significant difference was found between the two groups (P <0.01).Conclusion The MAC value of newborn rats was much higher than that of adult rats.Newborn rats need a higher concentration of sevoflurane at the same depth of anesthesia when compared with adult rats.

Minimum alveolar concentration of sevoflurane for endotracheal intubation without body movement in premature infants / 临床麻醉学杂志

Objective To determine the minimum alveolar concentration for endotracheal intu-bation (MACEI )of sevoflurane for curbing the responses to endotracheal intubation in 50% premature infants less than 37 weeks of corrected age.Methods Twenty-seven ASA Ⅰ or Ⅱ premature infants less than 37 weeks of corrected age were enrolled in this study.At first,the anesthesia induction was started by inhaling 6% sevoflurane.After the patient lost consciousness,the end tidal sevoflurane concentration (CET Sev)was adjusted to the target concentration and maintained stable for 1 5 min.En-dotracheal tube was then intubated.The up-and-down sequential method was used to calculate the MAC.The initial CET Sev was 3.0% and it was increased or decreased by 0.2% in the next patient ac-cording to the endotracheal intubation response.If the intubation response was positive,the CET Sev was increased;if the intubation response was negative,the CET Sev was decreased.The midpoint from negative response to positive response was set as a balance point and the mean value of the concentra-tions of sevoflurane at all the balance points were calculated as MACEI .Results The end tidal sevoflurane concentration for blunting the responses to endotracheal intubation in 50% premature in-fants was 2.55%±0.20%,and the MAC9 5 was 2.81% (95% confidence interval 2.67%-3.58%). Conclusion The MACEI of sevoflurane for curbing the responses to endotracheal intubation in 50%premature infants less than 37 weeks of corrected age is 2.55%,which is lower than that in the full-term children.

Effect of midazolam pretreatment on desflurane MAC(BAR) at an effect-site concentration of remifentanil 1.0 ng/ml

BACKGROUND: The goal of this prospective study was to determine the effect of midazolam pretreatment on the desflurane requirement for blunting the sympathetic response after surgical incision (minimum alveolar concentration blockade of adrenergic responses, MAC(BAR)) when desflurane is combined with a target-controlled concentration of remifentanil at 1 ng/ml. METHODS: Sixty-five patients aged 30 to 60 years with American Society of Anesthesiologists physical status of I or II who were undergoing general anesthesia for thyroidectomy were registered for this study. The patients were randomly allocated to receive either 30 microg/kg of midazolam (Group M) or isovolemic saline (Group C) intravenously before anesthetic induction. All patients were anesthetized with propofol, rocuronium, desflurane and remifentanil at a target-controlled effect-site concentration of 3 ng/ml at intubation followed by 1 ng/ml throughout the study. Sympathetic responses to surgical incision were determined 10 minutes after stabilization of end-tidal desflurane and target-controlled remifentanil concentrations. The predetermined end-tidal desflurane concentrations and MAC(BAR) for each group were determined using an up-and-down sequential allocation technique. RESULTS: The MAC(BAR) of desflurane with 1 ng/ml remifentanil concentration was 7.1 and 6.8% without and with midazolam pretreatment, respectively, using Dixon's up-and-down method (P = 0.755). CONCLUSIONS: Midazolam administered intravenously before anesthetic induction does not impact the MAC(BAR) of desflurane with an effect-site concentration of remifentanil 1.0 ng/ml.

Farmacologia clínica da metadona peridural e intravenosa em cães / Clinical pharmacology of peridural and intravenous methadone in dogs

A metadona é um opióide que possui potência analgésica semelhante à da morfina. Doses elevadas de metadona intravenosa (0,5-1,0 mg/kg), apesar de reduzirem a concentração alveolar mínima do isoflurano (CAMISO), resultam em maior depressão cardíaca que a observada com a morfina intravenosa (1,0 mg/kg) em cães. Com a hipótese de que a metadona peridural poderia proporcionar vantagens clínicas em relação à metadona intravenosa (maior potencialização da anestesia inalatória e maior eficácia analgésica), os estudos apresentados objetivaram comparar aspectos farmacocinéticos e farmacodinâmicos destas vias de administração da metadona em cães. Nos dois estudos iniciais (Capítulos 1 e 2), os mesmos seis animais foram anestesiados com isoflurano e tratados com metadona (0,5 mg/kg) peridural ou intravenosa em ocasiões distintas. No primeiro estudo (Capítulo 1), para comparação da farmacocinética destas duas vias de administração, a concentração de metadona foi determinada no plasma e no líquor da cisterna magna antes e durante 450 minutos após a administração do opióide. No segundo estudo (Capítulo 2), a CAMISO foi mensurada antes e após 2,5 e 5 horas da administração da metadona, mediante a aplicação da estimulação nociceptiva em membro pélvico e torácico (via peridural) ou em membro pélvico apenas (via intravenosa). No último estudo (Capítulo 3), cadelas apresentando tumores mamários, após serem tratadas de forma preemptiva com metadona (0,5 mg/kg) peridural ou intravenosa (10 animais por grupo), foram submetidas à mastectomia unilateral. Nesta etapa, avaliou-se a concentração expirada de isoflurano (ETISO) necessária à realização da mastectomia e, no período pós-operatório, avaliou-se os escores de dor, limiares nociceptivos mecânicos (LNM) das cadeias mamárias e requerimento de resgates analgésicos...

Methadone is an opioid that has analgesic potency comparable to that of morphine. High doses of intravenous methadone (0.5-1.0 mg/kg), in spite of reducing the minimum alveolar concentration of isoflurane (MACISO), cause greater cardiac depression than intravenous morphine (1 mg/kg) in dogs. The studies presented here aimed to compare some pharmacokinetic and pharmacodynamic aspects of peridural and intravenous methadone in dogs, testing the hypothesis that peridural methadone could result in clinical advantages when compared to intravenous methadone (greater reduction in anesthetic requirements and greater analgesic efficacy). In the first 2 studies (Chapters 1 and 2), the same six animals underwent isoflurane anesthesia and were treated with methadone (0.5 mg/kg) administered via the peridural or intravenous routes during different occasions. During the first study (Chapter 1), in order to compare the pharmacokinetics of these two administration routes, methadone concentrations were determined in plasma and in the cisternal cerebrospinal fluid before and for 450 minutes after opioid injection. During the second study (Chapter 2), MACISO was measured before, 2.5 and 5 hours after methadone injection via nociceptive stimulation of the thoracic and pelvic limb (peridural) or the pelvic limb (intravenous). During the last series of studies (Chapter 3), bitches presented with mammary gland tumors were preemptively treated with peridural or intravenous methadone (0.5 mg/kg) (10 animals per group) and underwent unilateral mastectomy. The end-tidal isoflurane concentration (ETISO) necessary for maintaining surgical anesthesia was evaluated and, during the postoperative period, parameters evaluated included Glasgow pain scores, mechanical nociceptive thresholds (MNT) in the mammary glands, and requirement for supplemental analgesia...

Minimum alveolar concentrations and hemodynamic effects of two different preparations of sevoflurane in pigs

BACKGROUND: Original sevoflurane (Sevo A) is made with water, while a generic sevoflurane (Sevocris) is produced with propylene glycol as a stabilizing additive. We investigated whether the original and generic sevoflurane preparations differed in terms of their minimum alveolar concentration (MAC) values and hemodynamic effects. METHODS: Sixteen pigs weighing 31.6±1.8 kg were randomly assigned to the Sevo A or Sevocris groups. After anesthesia induction via mask with the appropriate sevoflurane preparation (6 percent in 100 percent oxygen), the MAC was determined for each animal. Hemodynamic and oxygenation parameters were measured at 0.5 MAC, 1 MAC and 1.5 MAC. Histopathological analyses of lung parenchyma were performed. RESULTS: The MAC in the Sevo A group was 4.4±0.5 percent, and the MAC in the Sevocris group was 4.1±0.7 percent. Hemodynamic and metabolic parameters presented significant differences in a dose-dependent pattern as expected, but they did not differ between groups. Cardiac indices and arterial pressures decreased in both groups when the sevoflurane concentration increased from 0.5 to 1 and 1.5 MAC. The oxygen delivery index (DO2I) decreased significantly at 1.5 MAC. CONCLUSION: Propylene glycol as an additive for sevoflurane seems to be as safe as a water additive, at least in terms of hemodynamic and pulmonary effects.

The Comparison of Minimum Alveolar Concentration and BIS50 of Inhalation Anesthetics for Evaluation of Anesthetic Potency / 대한마취과학회지

BACKGROUND: The bispectral index (BIS) has been designed to objectively measure the degree of sedation and hypnosis for anesthesia. Although it has been well-known that BIS correlates highly with the concentration of inhalation anesthetics, it is not clear whether analgesic potency expressed as MAC is comparable to hypnotic potency described as BIS50 in inhaled anesthetics. This study was conducted to examine the degree of correspondence by correlating the changes of BIS according to the different MAC of commonly used inhalation anesthetics. METHODS: One hundred ASA class 1 or 2 patients, scheduled for laparoscopic knee surgery were included. Patients were equally divided into 4 groups (n = 25 each) according to the inhalational agent enflurane, isoflurane, desflurane, or sevoflurane. Anesthetic depth for each individual agent was controlled to 2.0, 1.75, 1.5, 1.25, 1.0, 0.75 and 0.5 MAC, respectively. After equilibration for each concentration, BIS values were measured three times at 30 second intervals and an average was obtained. In addition, MAC values for each agent were measured when the bispectral index showed 50. RESULTS: The concentrations of inhaled agents vs. BIS showed high negative correlations (enflurane; -0.91, isoflurane; -0.94, desflurane; -0.84, and sevoflurane; -0.86). BIS50 for each agent was enflurane, 0.93 (1.6 vol%); isoflurane, 0.71 (0.9 vol%); desflurane, 0.95 (5.7 vol%); and sevoflurane, 0.84 MAC (1.7 vol%). Isoflurane-BIS50 showed a significant difference to the others (P<0.05). CONCLUSIONS: We concluded that the MAC of inhalation anesthetics showed poor correlation with BIS, suggesting a difference between the hypnotic and analgesic potency of individual inhaled anesthetic agents.

Effects of Electroacupuncture on Minimum Alveolar Concentration of Isoflurane and Cardiovascular System in Isoflurane Anesthetized Dogs

The effects of electroacupuncture (EA) on the minimum alveolar concentration (MAC) and on the cardiovascular system were evaluated with dogs under isoflurane anesthesia. Eight healthy male beagles were randomly assigned to six study groups (five heads/group) with washout intervals of 7 ~ 31 days between experiments for recovery and anesthetic clearance. MAC of isoflurane and cardiovascular parameters were determined after EA at nonacupoint and and at acupoints LI-4, SP-6, ST-36 and TH-8. Electroacupuncture for 30 minutes at LI-4, SP-6, ST-36 and TH-8 acupoints lowered the MAC of isoflurane by 17.5 +/- 3.1%, 21.3 +/- 8.0%, 20.5 +/- 8.2% and 15.6 +/- 3.1%, respectively (p < 0.05). However, electrical stimulation of nonacupoint did not induce a significant change in MAC of isoflurane. In the cardiovascular system, the ST-36 group did not induce any significant change in cardiovascular parameters. In the TH-8 group, the mean and diastolic arterial pressure and the systemic vascular resistance were decreased. In the LI-4 group, cardiac output and cardiac index decreased after EA. These results indicate that EA at LI-4, SP-6 and ST-36 have advantages in isoflurane anesthesia in terms of reducing the dose of anesthetics and minimizing cardiovascular side effects.

Changes of MAC and electrophsiology during preferentinal delivery of isoflurane to the situ goat spinal cord / 中华麻醉学杂志

Objective:To evaluate the role of spinal cord in anesthesia of isoflurane. Method:The animal models of head bypass were established,which were used to preferentially anesthetized spinal cord, after 9 goats were anesthetized with isoflurane.MAC was determined using tail clamp at prebypass,druing bypass and postbypass. Electroen-cephalogram(EEG),brain stem auditory evoked Potential (BAEP) and visal evoked potential(VEP)were monitored constantly. Result:MAC of isoflurane,the relative power(RP)of ? wave and the latencies of BAEP and VEP were decreased when spinal cord was preferentinally anesthetized (P

Effects of deep hypothermia on MAC,cardiac anesthetic index and myocardial stability of valotile anesthetics / 中华麻醉学杂志

Objective:To investigate the effects of deep hypothermia on MAC,cardiac anesthetic index and myocardial stability of valotile anesthetics. Method: Forty New Zealand white rabbits were randomly divided into 4 groups:halothane, enflurane,isoflurane and sevoflurane. MAC of valotile agents were determined with the test of clamping tail at normal(38 C?0.5 C )and deep hypothermic(23 C?0.5 C )temperatures. The end-tidal valotile agent concentration at which ventricular arrhythmia appeared by increasing valotile agent concentration and stimulating the heart with extrathoracic electric shock(25V 50Hz)were recorded. Result:MAC of halothane, enflurane,isoflurane and sevoflurane were decreased by average percentage of 5.1,3.6,4.4 and 4.3 per degree from 38 C to 23 C respectively. Cardiac anesthetic indexes during deep hypothermia were 4.4,3.18.6.25 and 4.6. There was significantly higher incidence of ventricular fibrilation in halothane and enflurane groups (100％) than that in isoflurane and sevoflurane groups(40％)under 8 MAC anesthetics. Conclusion:Isoflurane is the most suitable valotile agent for deep hypothermic anesthesia, while enflurane is the least.

Relationship between content of norepinephrine or epinephrine in cortex and minimum alveolar concentration of isoflurane / 中华麻醉学杂志

0 05) 97% Spectral edge frequency (SEF) and median power frequency(MPF) decreased after intravenous clonidine(P0 05) Conclusions The contents of NE and E in cortex can indicate the inhabitive degree of isoflurane on consciousness, and the change of MAC of isoflurane is independent of the changes of NE and E contents in cortex,suggesting that the region where to determine the MAC of isoflurane is not at cortex

Influence of trauma on MAC of sevoflurane and plasma ?-endorphin concentration / 中华麻醉学杂志

Objective In order to explore the effects of trauma on MAC and its mechanism, the changes in MAC of sevoflurane and plasma ? endorphin were investigated in state of trauma. Methods Twenty New Zealand rabbits were randomly divided into control group and trauma group. MAP,CVP, P ET CO 2 and ECG were monitored continuously. The MAC of sevoflurane was measured in the two groups. In trauma group, the left femur of rabbits was fractured combined with parenchyma damage.Plasma ? endorphin concentration was assaied at various times in two groups. Results MAC of sevoflurane was 2 2%?0 2% in control group and 1 7%?0 2% in trauma group. Trauma induced increase of plasma ? endorphin concentration significantly 5min and 30min after trauma,? endorphin concentration increased by 44% and 52% in trauma group, respectively. Conclusions MAC of sevoflurane in rabbits is 2 2%?0 2%.Trauma can reduce MAC of inhalational anesthetic significantly. The endogenous ? endorphin releasing enormously induced with trauma may be one of the mechanisms to decrease MAC of inhalational anesthetics.

The Minimum Alveolar Concentration of Isoflurane in Korean Children / 대한마취과학회지

To determine the minimum alveolar concentration (MAC) of isoflurane in korean children, 33 children (preschool age group ; 17, school age group ; 16) were anesthetized with isoflurane in 100% oxygen. The move-no move responses to skin incision were recorded, and MAC was determined using the Litchfield-Wilcoxon method. MAC of isoflurane was determined in two pediatric age groups. MAC was 1.35% in preschool age group (10 month~7,5 yr of age), 1.37% in school age group (8~14 yr of age), 1.36% in all children (10 month~14 yr of age).