The interaction between emulsified isoflurane and lidocaine is synergism in intravenous regional anesthesia in rats.

BACKGROUND: Our previous studies have demonstrated that emulsified isoflurane (EI) produced epidural anesthesia and blockade of nerve conduction. We designed this study to observe whether EI could produce an anesthetic effect in IV regional anesthesia (IVRA) and to investigate the underlying interaction between EI and lidocaine when they were combined in IVRA. METHODS: IVRA was evaluated using tail-flick and tail-clamping tests in a rat model. In experiment 1, Sprague-Dawley rats were assigned to 4 groups (n = 10 per group), receiving 0.5 mL of 8%EI, 0.5% lidocaine, 30% Intralipid, or normal saline to observe whether EI could produce an anesthetic effect in IVRA. In experiment 2, for tail IVRA, EC(50) (median effective concentration) of EI alone and EC(50) of lidocaine alone, as well as EC(50) of lidocaine with the addition of Intralipid (0.0% EI) or with the addition of EI at different concentrations (0.4%, 0.8%, and 1.6%) were determined using an up-and-down method. Isobolographic analysis was used to evaluate the interaction between EI and lidocaine. RESULTS: For experiment 1, successful IVRA was observed in 8 of 10 rats with 8% EI, 10 of 10 rats with 0.5% lidocaine, and 0 of 10 rats with 30% Intralipid or normal saline. The anesthetic effect was not different in onset time (1.5 ± 0.9 vs 1.0 ± 0.0 minutes, P = 0.104) or recovery time (15 ± 9 vs 18 ± 12 minutes, P = 0.394) between 8% EI and 0.5% lidocaine. For experiment 2, EC(50) of EI was 4.467% ± 0.375% and EC(50) of lidocaine was 0.183% ± 0.072%; EC(50) of lidocaine was 0.173% ± 0.036% with the addition of Intralipid, and 0.064% ± 0.008%, 0.035% ± 0.005%, and 0.028% ± 0.006% with the addition of 0.4%, 0.8%, and 1.6% EI, respectively. With the addition of EI, the requirement for lidocaine was reduced in a synergistic manner. CONCLUSIONS: EI produced IVRA, and a synergistic interaction was found between EI and lidocaine for IVRA in a rat tail model.

A model of intravenous regional anesthesia in rats.

BACKGROUND: We developed an IV regional anesthesia (IVRA) model using the tails of rats to allow preclinical evaluation of the safety and efficacy of drugs used in IVRA and analgesia. METHODS: Three sequential experiments were designed to determine local anesthetic and analgesic effects of drugs injected IV in the tail. The anesthesia was assessed by monitoring the response of the tail-clamp (RTC) test on the tail, whereas the analgesia was assessed by recording the latency in the tail-flick test on the tail. In the first 2 experiments, we studied the effects of different environmental temperatures (15 degrees C, 25 degrees C, and 37 degrees C) and length of tourniquet time on the tail-flick and tail-clamp tests, respectively. Based on the outcomes of these 2 experiments, the pharmacological effects of 1% lidocaine (L group) and 0.5% bupivacaine (B group) were compared with normal saline (NS group) to evaluate this model in experiment 3. RESULTS: In experiment 1, compared with its baseline, tail-flick latency increased rapidly in the 15 degrees C group (P < 0.0001), whereas there were no changes in tail-flick latency in the 25 degrees C group (P = 0.3640) and the 37 degrees C group (P = 0.0641) after the first 20 minutes of tail submersion in a water bath. RTCs in all rats were positive during the entire observation period. In experiment 2, tail-flick latency did not change compared with baseline tail-flick latency after the first 20 minutes of tourniquet application (P = 0.0902), but significantly increased at the 30-, 40-, 50-, and 60-minute intervals (P = 0.0001). RTCs in all rats were positive during the experiment. In experiment 3, local anesthesia was generated in the tail (distal to the tourniquet) in the L and B groups with a similar onset time of anesthesia (approximately 1 minute), but with a longer recovery time of anesthesia and analgesia in the B group (56.0 +/- 22.0 minutes) than the L group (31.0 +/- 19.0 minutes), whereas no anesthetic and analgesic effects were observed in the NS group. CONCLUSIONS: A reliable model for studying IVRA and analgesia has been developed in rats.

[Preferential delivery of emulsified isoflurane to peripheral nerves in goats].

OBJECTIVE: To develop a new model for preferential delivery of isoflurane to peripheral nerves in goats, and to identify preliminarily volatile anesthetic action sites. METHODS: Eighteen goats were randomly and equally divided into arterial group, control group and venous group. In the arterial group, emulsified isoflurane was infused into the femoral artery of the goats to deliver isoflurane to the peripheral nerves. In the control group, 30% Intralipid which used as a solvent of emulsified isoflurane was infused via the femoral artery of the goats with the same infusing speed as that of the arterial group. In the venous group, emulsified isoflurane was infused via an ear peripheral vein. Minimum partial pressure (MPP), the partial pressure (Piso) of isoflurane in blood producing immobility in 50% of the goats exposed to noxious stimuli, was determined with an up-and-down method and a noxious stimulus by clamping the dew-claw of the hindlimbs of the goats in the arterial group and the control group, or the dew-claw of the hindlimb of the goats in the venous group. RESULTS: No isoflurane was found in the jugular and femoral veins of the goats in the control group, and normal nociceptive reflexeswere maintained. The MPP of the femoral vein of the goats from the control group did not differ from the MPP of the jugular vein of the goats from the arterial and venous groups. The MPP of femoral vein p was 7 times of that of jugular vein ](38.45 +/- 17. 01) mmHg vs. (5.82 +/- 2.32) mmHg, 1 mmHg = 0.1333 kPa, P < 0.05] in the goats from the arterial group, and 4 times of that of jugular vein in the goats from the venous group [(9.41 +/- 1.61) mmHg, P < 0.05]. The MPP of jugular vein in the goats from the arterial group was about half of that of the goats in the venous group. CONCLUSION: A new model of preferential delivery of isoflurane to the peripheral nerves in goats has been developed. Only Piso higher than that used in clinical anesthetic range has a significant anesthetic effect on peripheral nerves.

Effects of dexmedetomidine on heart rate control and pre-operative outcome in patients with acute aortic dissection: a propensity-matched analysis.

BACKGROUND: The total survival rate in patients with acute aortic dissection (AAD) has been greatly improved because of surgical technique advances. However, the pre-operative mortality rate remained high. In this study, we sought to evaluate the effects of dexmedetomidine (DEX) on heart rate control and preoperative outcome in AAD. METHODS: Retrospectively enrolled 461 patients who were diagnosed with AAD during the first 7-day after admission and divided into two groups according to the use of intravenous DEX: DEX group (91 patients) and Control group (370 patients). The heart rate and systolic blood pressure (SBP) level in both groups were recorded, and the incidence of aortic dissection rupture and pre-operative survival rates within 7 days were considered as the primary clinical outcomes. RESULTS: Compared to the Control group, heart rate of DEX group in the early 3 hours was significantly higher (P=0.009), and the 24-hour heart rate fluctuation was smaller (P=0.012). There was no difference in the systolic blood pressure (SBP) between the two groups, but the 24-hour fluctuation of SBP in DEX group was less (P=0.003). We performed a propensity-matched analysis to minimize selection bias and found that there were 7 (7.9%) patients in the DEX group occurred acute pulmonary edema, 17 (19.1%) patients in the Control group (P=0.047). And the pre-operative survival rates within 7 days were significantly improved in DEX group (P=0.004). And the pre-operative survival rates within 7 days were significantly improved in DEX group (P=0.004). CONCLUSIONS: DEX can be beneficial to facilitate heart rate control, keep SBP more steady, and reduce the incidence of pre-operative aortic rupture in patients with AAD.

Three-dimensional printed navigational template for localizing small pulmonary nodules: A case-controlled study.

BACKGROUND: Localization of small pulmonary nodules is an inevitable challenge for the thoracic surgeon. This study aimed to investigate the accuracy of three-dimensional (3D) printing technology for localizing small pulmonary nodules, especially ground-glass nodules (GGNs). METHODS: This study enrolled patients with peripheral small pulmonary nodules (≤ 2 cm) who required preoperative localization. In the comparison period, patients underwent both computed tomography-guided (CT-G) and 3D-printing template guided (3D-G) localization to compare the accuracies of the two methods. In the testing period, the 3D-printing technique was implemented alone. The 3D-printing physical navigational template was designed based on data from perioperative CT images. Clinical data, imaging data, surgical data, and evaluation index were collected for further analysis. The learning curve of the 3D-printing localization technique was assessed using cumulative sum (CUSUM) analysis and multiple linear regression analysis. RESULTS: In the comparison period (n = 14), the success rates of CT-G and 3D-G were 100% and 92.9% (P = 0.31), respectively; in the testing period (n = 23), the success rate of 3D-G was 95.6%. The localization times of CT-G, 3D-G (comparison), and 3D-G (testing) were 23.6 ± 5.3, 19.3 ± 6.8, and 9.8 ± 4.6 minutes, respectively. The CUSUM learning curve was modeled using the equation: Y = 0.48X2 - 0.013X - 0.454 (R2 = 0.89). The learning curve was composed of two phases, phase 1 (the initial 20 patients) and phase 2 (the remaining 17 patients). CONCLUSIONS: 3D printing localization has adequate accuracy and is a feasible and accessible strategy for use in localizing small pulmonary nodules, especially in right upper lobe. The use of this technique could facilitate lung nodule localization prior to surgery.

Further proof that the spinal cord, and not the brain, mediates the immobility produced by inhaled anesthetics.

BACKGROUND: Previous investigations indicate that the spinal cord, perhaps with a minor cerebral contribution, mediates the capacity of inhaled anesthetics to produce immobility in the face of noxious stimulation. The implications of these investigations may be limited by the trauma associated with their experimental methods (e.g., cardiopulmonary bypass or transection of the spinal cord). The present study avoided such trauma. METHODS: Thirty goats received emulsified isoflurane via either the initial section of the aorta (arterial group; preferential isoflurane delivery to the spinal cord) or an ear vein (venous group; equal delivery of isoflurane to the cord and brain). The authors determined the minimum partial pressure of isoflurane (the isoflurane partial pressure in the blood required to produce immobility in 50% of the goats exposed to a noxious stimulus). RESULTS: For the venous group, the minimum partial pressure in carotid versus femoral arterial blood (9.56 +/- 1.86 mmHg vs. 9.68 +/- 1.90 mmHg) did not differ. For the arterial group, the minimum partial pressure in carotid arterial blood was half that in femoral arterial blood (5.35 +/- 1.45 mmHg vs. 10.97 +/- 3.04 mmHg, P < 0.05). As these data show, the minimum partial pressure in femoral arterial blood did not differ for the arterial group versus the venous group. CONCLUSIONS: In this novel and minimally traumatic model, the anesthetic partial pressure delivered to the spinal cord governed the suppression of movement in response to noxious stimulation. The results indicate that the spinal cord is the primary mediator of immobility and that the brain plays little or no role.

[Protective effect of intralipid on myocardial ischemia/reperfusion injury in isolated rat heart].

OBJECTIVE: To investigate whether intralipid could protect perfused hearts of rats against ischemia/reperfusion (I/R) injury when it was administered before (preconditioning) or after the adverse ischemic event (postconditioning), in order to ascertain if intralipid would be a novel therapeutic strategy for myocardial I/R injury. METHODS: Studies were conducted in Langendorff-perfused isolated rat hearts. Twenty-four male Sprague-Dawley (SD) rats were divided into 3 groups randomly. The experimental procedure consisted of balance perfusion for 50 minutes, warm global ischemia (37 centigrade) for 40 minutes and 120 minutes of reperfusion. Preconditioning of hearts in myocardial preconditioning (I-preC group) consisted of 15 minutes of intralipid followed by 15 minutes of wash out before ischemia for 40 minutes and reperfusion for 120 minutes. In myocardial postconditioning (I-postC group) rat hearts were perfused with intralipid for 15 minutes at the onset of reperfusion. Hearts without intralipid treatment served as ischemic control (ISCH) group. Left ventricular mechanical function [heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular diastolic pressure (LVDP), maximal change rate of intraventricular pressure rise/down (+/-dp/dt max)] were measured during the experiment, cardiac enzyme activity [creatine kinase (CK), lactate dehydrogenase (LDH)] were determined at 20 minutes after balance and 60 minutes after reperfusion. RESULTS: Comparing with ISCH group, the LVDP and +dp/dt max in the I-postC group were significantly higher and LVDEP, -dp/dt max were lower when compared with ISCH groups during reperfusion (all P<0.05). There were no significant differences in above indexes in I-preC group. As compared with the ISCH group, the content of LDH and CK in I-preC and I-postC were significantly lower at 60 minutes after reperfusion (all P<0.05). However, there were no significant differences between the I-preC and I-postC groups with respect to the levels of LDH and CK. The infarct size (IS) of I-preC and I-postC was markedly smaller than that of the ISCH group at 120 minutes of reperfusion [(21.6+/-1.8)%, (15.9+/-1.3)% vs. (46.5+/-3.9)%, both P<0.05]. The IS did not differ between the I-preC and I-postC groups (P>0.05). CONCLUSION: Intralipid administered before or after ischemia can decrease the level of CK, LDH and IS during reperfusion in isolated rat hearts. Intralipid postconditioning improves mechanical function.

[Model establishment for emulsified isoflurane delivered selectively to the goat spinal cord and preliminary research on the immobility mechanism of isoflurane].

OBJECTIVE: To develop a new model of preferentially delivering isoflurane to the goat spinal cord, and to explore preliminarily volatile anesthetic action sites. METHODS: Eighteen goats were randomly and equally divided into group artery and group vein. In group artery, emulsified isoflurane was infused into descending aorta for developing the model to deliver isoflurane to the goat spinal cord. In group vein, emulsified isoflurane was infused via the ear vein. After the end-tidal isoflurane concentration of 1 minimum alveolar concentration (MAC) was maintained for 20 min, the isoflurane partial pressures (P(iso)) in samples which were drawn from the femoral artery and the carotid artery were determined by a gas chromatography. RESULTS: In group vein, there was no statistical difference among all the P(iso). In group artery, the P(iso) of the femoral arterial blood was almost same as that in group vein, but the P(iso) of the carotid arterial blood was near half of that in group vein [(6.07 +/- 3.60) mmHg vs (10.21 +/- 2.41) mmHg, P < 0.05]. CONCLUSION: This new model permits preferentially to deliver the isoflurane to the in situ goat spinal cord, and the results support the importance of the spinal cord in suppressing nociceptive reflex under isoflurane anesthesia.

[Fentanyl hypnotic interaction with emulsified isoflurane].

OBJECTIVES: To explore the effect of fentanyl on 50% effective dose (ED50) of emulsified isoflurane for hypnosis and to define the type of interaction between fentanyl and emulsified isoflurane during rat hypnosis. METHODS: 125 male adult Sprague-Dawley rats (240-300 g) were divided into 5 groups depending on the drugs administered via the tail vein. The up-and-down sequential allocation technique was used to determine ED50 of fentanyl in the loss of righting reflex. According to above experiment results, the up-and-down sequential allocation technique was also used to determine ED50 of emulsified isoflurane combined with different fentanyl dose of 7.2 microg/kg (1/4 ED50), 14.3 microg/kg (1/2 ED50) or 21.5 microg/kg (3/4 ED50), respectively, and also without the fentanyl in the loss of righting reflex. Fentanyl was administered intravenously for 20 s followed by emulsified isoflurane for 10 s. The interval between the two was 1.5 min in groups administered with both. ED50 was calculated by using Dixon-Mood method. The isobolographic and algebraic analyses were used to define the type of interaction between fentanyl and emulsified isoflurane. RESULTS: The body weight and sex of rats was not significantly different between the 5 groups. ED50 was (28.7 +/- 2.1) microg/kg (26.5-30.8 microg/kg) in the fentanyl group, (0.525 +/- 0.032) mL/kg in the fentanyl 7.2 microg/kg +/- isoflurane group, (0.108 +/- 0.019) mL/kg in the fentanyl 14.3 microg/kg+isoflurane group, (0.075 +/- 0.011) mL/kg in the fentanyl 21.5 microg/kg+isoflurane group and (0.670 +/- 0.054) mL/kg in the isoflurane group. The isobolographic analysis indicated that ED50 of isoflurane decreased progressively in a non-linear fashion in the presence of increasing dose of fentanyl. The isobolographic and algebraic analyses demonstrated that the combination use of fentanyl and emulsified isoflurane could produce a synergistic effect on hypnosis. CONCLUSIONS: Fentanyl enhances the hypnotic effect induced by emulsified isoflurane. The administration of associating fentanyl with emulsified isoflurane produces a synergistic effect on rat hypnosis.

Pyrazine-fused isoindigo: a new building block for polymer solar cells with high open circuit voltage.

Pyrazine-fused isoindigo (PzIIG) was designed and synthesized as a novel electron acceptor to construct two D-A conjugated polymers, PzIIG-BDT2TC8 and PzIIG-BTT2TC10. Both the polymers were successfully applied in polymer solar cells, and the PzIIG-BDT2TC8 based solar cell device exhibited a PCE of 5.26% with a high Voc over 1.0 V.

A model for the preferential delivery of isoflurane to the spinal cord of the goat.

To identify the blood supply of the caprine central nervous system, six anaesthetised goats were perfused with coloured suspension into the brachiocephalic artery, the aorta, the iliac artery and the femoral artery. The subsequent distribution indicated that the brain and the main segments of the spinal cord were supplied by the brachiocephalic artery and aorta, respectively. Ten similarly anaesthetised goats then received emulsified isoflurane randomly via either the proximal part of the descending aorta (arterial group) or an ear vein (venous group). In the arterial group, the isoflurane partial pressure (P(iso)) in femoral arterial blood was almost double the P(iso) in jugular venous blood. The model showed that preferential delivery of isoflurane to the goat spinal cord in situ was possible and could be used for further research into the mechanisms of anaesthetic action, particularly factors affecting immobility.