The Effects of Open-Lung Strategy on Lung Injury Markers in Patients under General Anesthesia with Low-tidal-volume Ventilation / 中山大学学报(医学科学版)

@#【Objective】To determine the effects of an open-lung strategy（OLS）comprising moderate positive end- expiratory pressure （PEEP） and intermittent recruitment manoeuvres（RMs） on plasma levels of lung epithelial injury markers［i.e. soluble receptor for advanced glycation end products（sRAGE）and Clara cell protein（CC16）］during low- tidal-volume ventilation for surgery.【Methods】One hundred patients who were undergoing laparoscopic colorectal cancer resection under low-tidal-volume ventilation were enrolled in this study. They were randomly assigned（1∶1）to the OLS group（using PEEP of 6~8 cmH2O and intermittent RM），or the NOLS group（without using PEEP and RM）. Blood samples were taken before anesthesia induction（T1），immediately after surgery（T2）and the postoperative day 3（T3）to measure the plasma concentrations of sRAGE and CC16. 【Results】 Significant differences were not observed in the concentrations of sRAGE and CC16 at T1，T2 and T3 between the two groups（all P > 0.05）. For all the enrolled patients， the concentrations of sRAGE at T2 and T3 were higher than that at T1，the concentration of sRAGE at T3 was higher than that at T2，and the concentration of CC16 at T3 was higher than that at T1 and T2（all P < 0.05）.【Conclusions】In patients under general anesthesia with low-tidal-volume ventilation，the using of an OLS comprising medium PEEP and intermittent RMs can not alter plasma levels of lung epithelial injury markers（sRAGE and CC16）in three days after surgery.

Regular transient limb ischemia prevents atherosclerosis progression in hypercholesterolemic rabbits / 中华医学杂志(英文版)

BACKGROUND@#Endothelial dysfunction, the initial pathogenic factor in atherosclerosis, can be alleviated via transient limb ischemia. We observed the effects of regular transient limb ischemia (RTLI) on atherosclerosis in hypercholesterolemic rabbits.@*METHODS@#Twenty-eight rabbits were randomized to control, cholesterol, sham, ischemia groups (n = 7 each) between October 2010 and March 2011. They were fed a normal diet in the control group and hypercholesterolemic diet in other groups for 12 weeks. Six cycles of RTLI were performed once per day on the ischemia group. Serum samples were prepared to measure the total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) before the experiment (W0), at the end of weeks 4, 8, 12 (W4, W8, W12). The whole aorta was harvested at W12 and stained using Sudan IV to identify the plaque. The plaque area was measured using Image J. Results were analyzed by analysis of variance or rank sum test.@*RESULTS@#Concentrations of TC in the cholesterol group were higher than those in the control group at W4 (29.60 [23.75, 39.30] vs. 1.00 [0.80, 1.55], Z = -2.745, P = 0.006), W8 (41.78 [28.08, 47.37] vs. 0.35 [0.10, 0.68], Z = -2.739, P = 0.006), W12 (48.32 [40.04, 48.95] vs. 0.61 [0.50, 0.86], Z = -2.739, P = 0.006). Similar results were obtained for HDL-C and LDL-C. Serum concentrations of TC, HDL-C, and LDL-C in the hypercholesterolemic groups had no differences (all P > 0.05). The percentage of plaque area in the cholesterol group was higher than that in the control group (47.22 ± 23.89% vs. 0, Z = -2.986, P = 0.003). Square root of the percentage of plaque area was smaller in the ischemia group than that in the cholesterol (0.44 ± 0.13 vs. 0.67 ± 0.18, P = 0.014) or sham groups (0.44 ± 0.13 vs. 0.61 ± 0.12, P = 0.049).@*CONCLUSION@#In hypercholesterolemic rabbits, RTLI might prevent atherosclerosis progression by reducing the percentage of plaque area.

Regular transient limb ischemia prevents atherosclerosis progression in hypercholesterolemic rabbits / 中华医学杂志(英文版)

Background:@#Endothelial dysfunction, the initial pathogenic factor in atherosclerosis, can be alleviated via transient limb ischemia. We observed the effects of regular transient limb ischemia (RTLI) on atherosclerosis in hypercholesterolemic rabbits.@*Methods:@#Twenty-eight rabbits were randomized to control, cholesterol, sham, ischemia groups (n=7 each) between October 2010 and March 2011. They were fed a normal diet in the control group and hypercholesterolemic diet in other groups for 12 weeks. Six cycles of RTLI were performed once per day on the ischemia group. Serum samples were prepared to measure the total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) before the experiment (W0), at the end of weeks 4, 8, 12 (W4, W8, W12). The whole aorta was harvested at W12 and stained using Sudan IV to identify the plaque. The plaque area was measured using Image J. Results were analyzed by analysis of variance or rank sum test.@*Results:@#Concentrations of TC in the cholesterol group were higher than those in the control group at W4 (29.60 [23.75, 39.30] vs. 1.00 [0.80, 1.55], Z = –2.745, P = 0.006), W8 (41.78 [28.08, 47.37] vs. 0.35 [0.10, 0.68], Z = –2.739, P = 0.006), W12 (48.32 [40.04, 48.95] vs. 0.61 [0.50, 0.86], Z = –2.739, P = 0.006). Similar results were obtained for HDL-C and LDL-C. Serum concentrations of TC, HDL-C, and LDL-C in the hypercholesterolemic groups had no differences (all P > 0.05). The percentage of plaque area in the cholesterol group was higher than that in the control group (47.22 ± 23.89% vs. 0, Z = –2.986, P = 0.003). Square root of the percentage of plaque area was smaller in the ischemia group than that in the cholesterol (0.44 ± 0.13 vs. 0.67 ± 0.18, P = 0.014) or sham groups (0.44 ± 0.13 vs. 0.61 ± 0.12, P = 0.049).@*Conclusion:@#In hypercholesterolemic rabbits, RTLI might prevent atherosclerosis progression by reducing the percentage of plaque area.

Comparison of safe duration of apnea and intubation time in face mask ventilation with air versus 100% oxygen during induction of general anesthesia / 南方医科大学学报

<p><b>OBJECTIVE</b>To compare the safe duration of apnea and intubation time between face mask ventilation with air and 100% oxygen during induction of general anesthesia.</p><p><b>METHODS</b>Eighty adult patients with ASA class I or II without predicted difficult airways were scheduled for elective surgery under general anesthesia. The patients were randomized to receive anesthesia induction with preoxygenation [Group 1, n=40, fraction of inspired oxygen (FiO)=1] or without preoxygenation (Group2, n=40, FiO=0.21). Two experienced anesthesiologists performed the mask ventilation and tracheal intubation during induction, and the assistants adjusted the oxygen concentration and recorded the pulse oxygen saturation (SpO) and other variables. The cases where SpOdecreased to below 90% before accomplishment of intubation were considered unsuccessful, and mask ventilation with 100% oxygen was given. After tracheal intubation, mechanical ventilation was not initiated until the SpOdecreased to 90%. The number of unsuccessful cases, the safe duration of apnea and intubation time were recorded in the two groups.</p><p><b>RESULTS</b>There was no unsuccessful case in either groups. The safe duration of apnea was 469.5∓143.0 s in Group 1 and 63.6∓20.0 s in Group 2, and the intubation time was 34.4∓12.6 s and 32.8∓9.6 s, respectively. The safe duration of apnea was significantly longer than the intubation time in both groups (P<0.01). The intubation time and the number of cases with SpO≥90% before completion of tracheal intubation were similar between the two groups. The safe duration of apnea was significantly shorter in Group 2 than in Group 1 (P<0.01) and was correlated with the body mass index of the patients (P<0.05).</p><p><b>CONCLUSION</b>Anesthesia induction without preoxygenation can provide sufficient time for experienced anesthesiologists to complete tracheal intubation.</p>

Transfusion of Plasma Collected at Late Phase after Preconditioning Reduces Myocardial Infarct Size Induced by Ischemia-reperfusion in Rats / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Plasma transfusion is a common clinical practice. Remote ischemic preconditioning (RIPC) protects organs against ischemia-reperfusion (IR) injury. Whether preconditioned plasma (PP), collected at late phase after RIPC, could protect organs against IR injury in vivo is unknown. This study explored whether transfusion of PP could reduce myocardial infarct size (IS) after IR in rat in vivo.</p><p><b>METHODS</b>Eighty Lewis rats were randomized to eight groups (n = 10 for each group). Two groups of plasma donor rats donated plasma at 48 h after transient limb ischemia (PP) or control protocol (nonpreconditioned plasma [NPP]). Six groups of recipient rats received normal saline (NS; NS-IR 1, and NS-IR 24 groups), NPP (NPP-IR 1 and NPP-IR 24 groups), or PP (PP-IR 1 and PP-IR 24 groups) at one or 24 h before myocardial IR. Myocardial IR consisted of 30-min left anterior descending (LAD) coronary artery occlusion and 180-min reperfusion. The area at risk (AAR) and infarct area were determined by double-staining with Evans blue and triphenyltetrazolium chloride. IS was calculated by infarct area divided by AAR. This was a 3 × 2 factorial design study, and factorial analysis was used to evaluate the data. If an interaction between the fluid and transfusion time existed, one-way analysis of variance with Bonferroni correction for multiple comparisons was used to analyze the single effects of fluid type when the transfusion time was fixed.</p><p><b>RESULTS</b>IS in the NPP-IR 1 and PP-IR 1 groups was smaller than in the NS-IR 1 group (F = 6.838, P = 0.005; NPP-IR 1: 57 ± 8% vs. NS-IR1: 68 ± 6%, t = 2.843, P = 0.020; PP-IR 1: 56 ± 8% vs. NS-IR 1: 68 ± 6%, t = 3.102, P = 0.009), but no significant difference was detected between the NPP-IR 1 and PP-IR 1 groups (57 ± 8% vs. 56 ± 8%, t = 0.069, P = 1.000). IS in the NPP-IR 24 and PP-IR 24 groups was smaller than in the NS-IR 24 group (F = 24.796, P< 0.001; NPP-IR 24: 56% ± 7% vs. NS-IR 24: 68 ± 7%, t = 3.102, P = 0.026; PP-IR 24: 40 ± 9% vs. NS-IR 24: 68 ± 7%, t = 7.237, P< 0.001); IS in the PP-IR 24 group was smaller than in the NPP-IR 24 group (40 ± 9% vs. 56 ± 7%, t = 4.135, P = 0.002).</p><p><b>CONCLUSION</b>Transfusion of PP collected at late phase after remote ischemic preconditioning could reduce IS, suggesting that late-phase cardioprotection was transferable in vivo.</p>

Application of titrated target-controlled infusion anesthesia in laparoscopic colorectal surgery / 中华胃肠外科杂志

<p><b>OBJECTIVE</b>To evaluate the effect of titrated target-controlled infusion with propofol and remifentanil on anesthetics consumption and anesthesia depth in patients undergoing elective laparoscopic colorectal surgery.</p><p><b>METHODS</b>Sixty ASA I-III patients for elective laparoscopic colorectal surgery were enrolled. Titrated target-controlled infusion (TCI) with propofol and remifentanil was performed. Plasma concentration of the drugs was administered by titrated method to maintain bispectral index (BIS) in the range of 40-60 with systolic blood pressure (SBP) fluctuation within 20% of the basic value. BIS, SBP, plasma concentration of propofol and remifentanil were recorded at different time points. Awareness during operation was inquired postoperatively.</p><p><b>RESULTS</b>During the entire anesthesia period, the blood pressure was stable and BIS was maintained less than 60. There was no awareness during operation. The plasma concentrations (95% confidence interval) for TCI of propofol and remifentanil were 2.55-2.65 mg/L and 4.09-4.26 μg/L respectively when existing surgical stimulation during anesthesia, and the plasma target concentration of propofol was lower than the recommended dosages.</p><p><b>CONCLUSION</b>Titrated target-controlled infusions with propofol and remifentanil for elective laparoscopic colorectal surgery can maintain proper anesthesia depth and reduce the drug consumption.</p>

Effects of plasma collected 48 hours after transient limb ischemia on blood pressure recovery in homogenic rats after myocardial ischemia reperfusion in vivo / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Whether plasma can transfer the protective effect(s) of remote ischemic preconditioning (RIPC) between animals remains unresolved. We therefore investigated the effects of plasma collected 48 hours after transient limb ischemia on blood pressure recovery during myocardial ischemia reperfusion (IR) in homogenic rats.</p><p><b>METHODS</b>Plasma was collected from Lewis rats, and the donor rats were randomly assigned to 2 groups: transient limb ischemia and control (n = 8 each). Transient limb ischemia was achieved by four cycles of 5-minute ischemia and 5-minute reperfusion by noninvasive ligation and deligation of the both legs using elastic rubber bands after anesthesia. In the control group, no ligation was performed. Forty-eight hours later, whole blood was collected, and the plasma spun off. Study Lewis rats underwent 30-minute left anterior descending coronary artery occlusion followed by 180-minute reperfusion, and were randomly assigned to 2 groups (group A and group B, n = 24 each), each further subdivided into 3 subgroups (n = 8 each). The subgroups of group A received normal saline (group A1) , plasma of control rats (group A2), plasma of transient limb ischemia rats (group A3) respectively at 1 hour before IR; the subgroups of group B received normal saline (group B1), plasma of control rats (group B2), plasma of transient limb ischemia rats (group B3) respectively at 24 hours before IR. BIOPAC systems were used to measure hemodynamics of rats during myocardial ischemiareperfusion.</p><p><b>RESULTS</b>Systolic blood pressure (SBP) after IR in group B3 was different from that in groups B1 and B2 (B3 vs. B1, P = 0.007; B3 vs. B2, P = 0.039) at the beginning of reperfusion and 30 minutes after reperfusion. SBP was higher in group B3 than in groups B1 and B2 at the beginning of perfusion (B3 vs. B1, P = 0.010; B3 vs. B2, P = 0.002) and 30 minutes after reperfusion (B3 vs. B1, P = 0.001; B3 vs. B2, P = 0.001). SBP did not differ among subgroups A1, A2 and A3. Diastolic blood pressure and heart rate did not change in group A or group B.</p><p><b>CONCLUSIONS</b>The transfusion of plasma collected 48 hours after transient limb ischemia into homogenic rats 24 hours before IR can improve the SBP recovery during reperfusion. This may suggest that cardioprotective effect of late phase of RIPC is transferable via plasma.</p>

A pilot study of the effect of pressure-driven lidocaine spray on airway topical anesthesia for conscious sedation intubation / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Difficult airway remains not only a challenge to the anesthesiologists, but also a life-threatening event to the patients. Awake intubation is the principal choice to deal with difficult airway, and a key point for awake intubation is airway topical anesthesia. Yet, so far there is no ideal topical anesthesia approach for awake intubation. This study aimed at evaluating the effect of pressure-driven (by 10 L/min oxygen flow) lidocaine spray on airway topical anesthesia in order to find a powerful and convenient method for airway topical anesthesia for conscious sedation intubation.</p><p><b>METHODS</b>Thirty adult patients referred for elective surgery under general anesthesia, aged 18 - C60 years and Mallampati class I or II, were recruited for the study. Before topical anesthesia, the observer's assessment of alert and sedation (OAA/S) scale was controlled between 3 and 4 by intravenous midazolam (0.03 mg/kg), propofol (2 mg×kg(-1)×h(-1)) and remifentanil (0.05 µg×kg(-1)×min(-1)). Ten minutes after sedation, topical anesthesia was performed with the pressure-driven lidocaine spray; the driving pressure was achieved by an oxygen flow of 10 L/min. After topical anesthesia, tracheal intubation was performed and the intubation condition was assessed with modified the Erhan's intubation condition score by an experienced anesthesiologist, and a score of less than 10 was considered to be satisfactory. Attempts to intubate the patient were recorded, and the complications such as local anesthetic toxicity, mucosa injury, and respiration depression were also recorded. The mean arterial blood pressure (MAP), heart rate (HR) and pulse oxygen saturation (SpO2) were recorded at different time points before and after intubation. Patients were asked 24 hours after the operation whether they could recall the events during intubation.</p><p><b>RESULTS</b>All patients were intubated at the first attempt, the average intubation condition score was 7.0 ± 1.1, from 6 to 10, satisfied intubation condition. MAP and HR increased significantly but mildly immediately after the tracheal intubation (P < 0.05), and decreased to the pre-intubation level soon after intubation. There were no related complications and patients had no recall of the intubation procedures.</p><p><b>CONCLUSIONS</b>Topical anesthesia with pressure driven 2% lidocaine spray, where pressure is achieved by 10 L/min oxygen flow, can offer satisfactory intubation conditions for conscious sedation intubation.</p>

Effects of mechanical ventilation and controlled spontaneous respiration on pulmonary function during short duration of general anesthesia with tracheal intubation / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the effects of mechanical ventilation on pulmonary function during short duration of general anesthesia with tracheal intubation, and assess the safety of controlled spontaneous respiration during general anesthesia.</p><p><b>METHODS</b>Fifty-three adult patients (aged 18-55 years, ASA physical status I-II) scheduled for elective unilateral tympanoplasty were randomly assigned into mechanical ventilation group (group M, n=28) and spontaneous respiration group (group S, n=25). Anesthesia induction was performed in group M with intravenous propofol (2 mg/kg), fentanyl (3 microg<kg) and vecuronium (0.1 mg<kg), while with propofol (2 mg/kg), fentanyl (3 microg/kg) and sufficient superficial anesthesia on upper airway mucous membrane in group S. After tracheal intubation, mechanical ventilation began with VT 8 ml<kg and RR 10-12 bpm in group M, and spontaneous respiration was maintained in group S. Anesthesia was maintained by 0.7%-0.8% isoflurane and 60%-70% N(2)O at the end respiratory concentration to control MAC between 1.2-1.3. During the surgery, BIS values were controlled between 40-60, and propofol was administered when necessary. Vecuronium (1-2 mg) was given intermittently to maintain muscle relaxation and neostigmine (1 mg) with atropine 0.5 mg was administered intravenously before extubation in group M. No relaxant was used in group S. The parameters including heart rate (HR), mean blood pressure (MAP), pulse oxygen saturation (SpO(2)), and thoracic fluid content (TFC) were recorded before the induction and at 1, 5, 10, 20, 40, 60, 90, 120, and 150 min after intubation. Arterial blood was drawn immediately and 150 min after intubation for blood gases analysis and Alveolar-arterial oxygen gradient (P(A-a)DO(2)), and the respiratory index (RI) and dead volume/tidal volume (VD/VT) were calculated. The incidences of moving, bucking, swallowing, and status of awareness during surgery procedures were also recorded.</p><p><b>RESULTS</b>A total of 43 patients (group M, n=23; group S, n=20) were included in the study with 10 dropouts due to failed attempt to obtain arterial blood samples (8 patients) or severe bucking during intubation (2 patients). No significant differences were found in HR and MAP between the two groups (P>0.05). The pH and SpO(2) [ (97.9-/+1.00)% at the lowest] and PaO(2) in group S were significantly lower and the PaCO(2) was higher than those in group M (P<0.05). In group S, the pH values were 7.274-/+0.025 and 7.331-/+0.039, PaCO(2) values were 60-/+6 and 53-/+5 mmHg, and PETCO(2) values were 53-/+ 6 and 48-/+7 mmHg, and the PaO(2) values were 143-/+37 and 165-/+49 mmHg immediately and 150 min after the intubation, respectively. These values were considered safe under the concept of permissive hypercapnia. No significant differences were found in the P(A-a)DO(2), RI, VD/VT and TFC between or within the two groups (P>0.05), nor were moving, bucking, swallowing and awareness recorded during the surgical procedures.</p><p><b>CONCLUSION</b>In essentially normal lungs, short-term mechanical ventilation during general anesthesia with tracheal intubation does not damage the lung functions, and spontaneous respiration can offer sufficient oxygen supply without causing harmful carbon dioxide retention.</p>

Effect of fresh gas flow on isoflurane pharmacokinetics during anesthesia induction / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of different fresh gas flow (FGF) rates on isoflurane pharmacokinetics during anesthesia induction.</p><p><b>METHODS</b>Sixty female patients (ASA class I-II, age range of 18-49 years) scheduled for gynecological laparoscopic surgery were randomly divided into groups I, II, and III (n=20) for isoflurane inhalation with FGF rate of 1, 2, and 3 L/min, respectively. Each group was further divided into two equal subgroups according to the setting concentration of the isoflurane vaporizer at 1% (groups I 1, II 1, and III 1) and 2% (groups I 2, II 2, and III 2). Isoflurane with different setting concentrations was administered under different FGFs in the patients after tracheal intubation following anesthesia induction, and the inspiratory concentration (CIiso) and expiratory concentration (CEiso) of isoflurane in the airway were monitored and recorded every 3 min for totalling 18 min, with the observation time points marked as T1 to T6, respectively.</p><p><b>RESULTS</b>CIiso and CEiso varied significantly at different time points and between different subgroups (P<0.05). In each subgroup, CIiso and CEiso increased along with time and reached a relatively stable stage at 9 min, but failed to reach the setting concentration during the observation period. At different observation time points, CIiso and CEiso in the subgroups with setting isoflurane concentration of 2% were almost twice as much as that in the subgroups with setting isoflurane concentration of 1%.</p><p><b>CONCLUSIONS</b>CIiso and CEiso increase along with time lapse in all the groups and reach a relatively stable stage at 9 min after inhalation initiation, but can not reach the setting concentration. The larger the FGF and setting concentration, the faster CIiso and CEiso increase.</p>

Effect of temperature on the activation of myocardial KATP channel in guinea pig ventricular myocytes: a pilot study by whole cell patch clamp recording / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The myocardial ATP sensitive potassium channel (K(ATP) channel) has been known for more than two decades, the properties of this channel have been intensively investigated, especially the myocardial protection effect by opening this channel. Numerous studies, including hypothermic, using K(ATP) agonists to achieve a hyperpolarizing cardioplegic arrest, have shown a better myocardial protection than potassium arrest. However, there is no evidence showing that K(ATP) channel could be opened by its agonists under profound hypothermia. We investigated the effect of temperature on activation of myocardial K(ATP) channel by nicorandil.</p><p><b>METHODS</b>Isolated ventricular myocytes were obtained by collagenase digestion of the hearts of guinea pigs and stored in KB solution at 4 degrees C. With a steady ground current, the myocytes were perfused with 1 mmol/L nicorandil until a steady IK(ATP) occurred. Then the cells were perfused with 1 mmol/L nicorandil plus 1 micromol/L glybenclamide. Currents signals were recorded on whole cells using patch clamp technique at several temperatures. The temperature of the bath solution around myocytes was monitored and was controlled at 4 degrees C, 10 degrees C, 20 degrees C, 25 degrees C and 35 degrees C respectively. About 10 cells were tested at each temperature, the cells were considered useful only when the outward current could be induced by nicorandil and blocked by glybenclamide. All data were analyzed using Graphpad PRISM 3.0 (Graphpad, San Diego, CA, USA). Nonlinear curve fitting was done in Clampfit (Axon) or Sigmaplot (SPSS).</p><p><b>RESULTS</b>At 4 degrees C, 10 degrees C, 20 degrees C, 25 degrees C and 35 degrees C, the time needed to open the myocardial K(ATP) channel was (81.0 +/- 0) minutes, (50.5 +/- 11.7) minutes, (28.8 +/- 2.3) minutes, (9.4 +/- 10.2) minutes and (2.3 +/- 1.0) minutes respectively (P = 0.003). The linear relationship between temperature and time needed to open the channel was y (min) = (4348.790 - 124.277x)/60, where y (min) is time needed to open K(ATP) channel, x is temperature, correlation coefficient r = -0.942 (P = 0.00), regression coefficient b = -124.277 (P = 0.00). The current densities among different temperatures were statistically different (P = 0.022), the current density was greater after the activation of K(ATP) channel at higher temperatures. The lower the temperature, the fewer cells in which K(ATP) channels could be opened. At 4 degrees C, only one cell in which the K(ATP) channel could be opened, took a quite long time (81 minutes) and the I-V curve was quite untypical.</p><p><b>CONCLUSIONS</b>K(ATP) channel activated by nicorandil is temperature dependent and the temperature linearly related to time needed to open K(ATP) channel; the lower the temperature, the longer the time needed to open channel and the smaller the current density. At profound hypothermia, it is difficult to activate K(ATP) channels.</p>

Effects of different fresh gas flow on pharmacodynamics of isoflurane during anesthesia induction / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of different fresh gas flows (FGFs) on the pharmacodynamics of isoflurane during anesthesia induction.</p><p><b>METHODS</b>Sixty female ASA class I or II patients (aged from 18 to 49 years) scheduled for gynecologic laparoscopic surgery were randomly divided into groups I, II, and III (n=20). The FGFs for group I, II, and III was 1, 2 and 3 L/min, respectively, and each group was further divided into two equal subgroups according to the setting concentrations of isoflurane vaporizer (Co), which was 1% in groups I1, II1, and III1 and 2% in groups I2, II2, and III2. Isoflurane at different setting concentration was administered under different FGF in the patients after tracheal intubation following anesthesia induction. The systolic blood pressure (SBP), diastolic blood pressure (DBP), main arterial blood pressure (MAP), heart rate (HR) and bispectral index (BIS) were recorded before anesthesia induction and every 3 min after tracheal intubation. Patients given ephedrine and atropine were also recorded. The patients' consciousness during anesthesia were followed up and recorded. The inspiratory concentration (CIiso) and expiratory concentration (CEiso) of isoflurane in the airway were monitored and recorded every 3 min. The observation after intubation lasted for 18 min, during which stimulation of the patients was avoided, and the operation began after the observation.</p><p><b>RESULTS</b>There was a close correlation between BIS and CIiso and between BIS and CEiso (r=-0.904 and -0.893, respectively). The incidence of hypotension was significantly different between groups III and I (P<0.01), and between the subgroups in groups II and I (P<0.05). No bradycardia occurred and no consciousness reported awareness during anesthesia.</p><p><b>CONCLUSIONS</b>Between the completion of tracheal intubation and beginning of the surgery, 1% or 2% Co under a moderate FGF (1-3 L/min) may guarantee the patients' unconsciousness, but hypotension is less likely under a relatively low flow (1-2 L/min) than a higher flow (3 L/min). Higher FGF and Co result in faster induction of deep anesthesia and higher incidence of hypotension.</p>