Sevoflurane and Isoflurane Protect the Reperfused Guinea Pig Heart by Reducing Postischemic Adhesion of Polymorphonuclear Neutrophils

Background: Polymorphonuclear neutrophils (PMNs) contribute to reperfusion injury. Because volatile anesthetics can reduce PMN adhesion in the reperfused, nonworking heart, the authors analyzed whether this action of volatile anesthetics affects cardiac performance after ischemia and reperfusion and further clarified the underlying mechanism.

Methods: Isolated guinea pig hearts perfused with crystalloid buffer and performing pressure-volume work were used. Hearts were subjected to 15 min global ischemia and 20 min reperfusion. In the intervention groups an intracoronary bolus of 3 x 106 PMNs was applied in the second min of reperfusion, either in the absence or presence of 0.5 or 1 minimum alveolar concentration sevoflurane or isoflurane. The number of sequestered PMNs was calculated from the difference between coronary input and output (coronary effluent) of PMNs. Performance of external heart work, determined pre- and postischemically, served as criterion for recovery of myocardial function. Additionally, the expression of the integrin CD11b on the cell surface of PMN was measured before and after coronary passage.

Results: Injection of PMN in the reperfusion phase, but not under nonischemic conditions, reduced recovery of external heart work significantly (from 55 +/- 7% to 19 +/- 11%). Addition of sevoflurane or isoflurane in concentrations of 0.5 and 1 minimum alveolar concentration to the perfusate reduced postischemic PMN adhesion from 36 +/- 8% to basal values (20 +/- 7%) and prevented decline of cardiac function. CD11b expression on PMNs increased significantly during postischemic coronary passage under control conditions. Again, both anesthetics in both concentrations inhibited that activation.     

Inhibition of neutrophil activation by volatile anesthetics decreases adhesion to cultured human endothelial cells.

BACKGROUND: Polymorphonuclear leukocytes (neutrophils, PMNs) have been shown to mediate vascular and tissue injury, leading to so-called systemic inflammatory response syndrome. The authors evaluated the effect of volatile anesthetics on neutrophil adhesion to human endothelial cells, focusing on whether the inhibitory effect observed is linked to an alteration in the function of endothelial cells or neutrophils. METHODS: The adhesion of human PMNs was quantified using cultured human umbilical vein endothelial cells (HUVECs). The increase in the number of adhering PMNs was assessed when HUVECs (with 1 mM hydrogen peroxide), PMNs (with 10 nM N-formyl-methionyl-leucyl-phenylalanine), or both were prestimulated. To determine the influence of volatile anesthetics on the adhesion of PMNs, the experiments were performed in the absence or presence of 0.5, 1, and 2 minimum alveolar concentration halothane, isoflurane, or sevoflurane, whereby HUVECs, PMNs, or both were pretreated with gas. RESULTS: Activation of HUVECs with hydrogen peroxide or stimulation of PMNs with N-formyl-methionyl-leucyl-phenylalanine resulted in a 2.5-fold increase in PMN adhesion. Preincubation of PMNs, separately, with halothane, isoflurane, or sevoflurane, respectively, abolished enhanced neutrophil adhesion to hydrogen peroxide-activated HUVECs and adhesion of PMNs prestimulated with N-formyl-methionyl-leucyl-phenylalanine to unstimulated HUVECs (maximal effect at 1 minimum alveolar concentration). No decrease in adhesion was detected when only HUVECs were pretreated with volatile anesthetics. Additional exposure of HUVECs and PMNs to volatile anesthetics had no inhibitory effect on adhesion greater than that seen when only PMNs were treated. Appropriately, the volatile anesthetics abolished the upward regulation of the adhesion molecule CD11b on PMNs (as evaluated at 1 minimum alveolar concentration each), whereas 1 minimum alveolar concentration halothane failed to affect the expression of P-selectin, an adhesion molecule on endothelial cells. CONCLUSIONS: This study indicates that halothane, isoflurane, and sevoflurane inhibit neutrophil adhesion to human endothelial cells at concentrations relevant to anesthesia in a static system. The effects appear to be mediated by inhibition of PMN activation; that is, by attenuating the upward regulation of neutrophil CD11b.     

Halothane, Isoflurane, and Sevoflurane Reduce Postischemic Adhesion of Neutrophils in the Coronary System

Background: Polymorphonuclear neutrophils (PMNs) contribute to postischemic reperfusion damage in many organs and tissues, a prerequisite being adhesion of PMNs to vascular endothelial cells. Because adhesion processes involve orderly interactions of membrane proteins, it appeared possible that "membrane effects" of volatile anesthetics could interfere. We investigated the effects of halothane, isoflurane, and sevoflurane on postischemic adhesion of human PMNs in the intact coronary system of isolated perfused guinea pig hearts.

Methods: The hearts (n = 7-10 per group) were perfused in the "Langendorff" mode under conditions of constant flow (5 ml/min) using modified Krebs-Henseleit buffer equilibrated with 94.4% oxygen and 5.6% carbon dioxide. Global myocardial ischemia was induced by interrupting perfusion for 15 min. In the second minute of reperfusion (5 ml/min), a bolus dose of 6 x 105 PMNs was injected into the coronary system. The number of cells reemerging in the coronary effluent was expressed as a percentage of the total number of applied PMNs. Halothane, isoflurane, and sevoflurane, each at 1 and 2 minimal alveolar concentration (MAC), were vaporized in the gas mixture and applied from 14 min before ischemia until the end of the experiment.

Results: Under nonischemic conditions, 24.7 +/- 1.3% of the injected neutrophils did not reemerge from the perfused coronary system. Subjecting the hearts to global ischemia augmented retention (36.4 +/- 2.8%, P <.05). Application of halothane reduced adhesion of neutrophils to 22.6 +/- 2.1% and 24.2 +/- 1.8% at 1 and 2 MAC, respectively (P < .05). Exposure to 1 and 2 MAC isoflurane was similarly effective, whereas basal adhesion was not significantly influenced. Sevoflurane-treated hearts (1 and 2 MAC) also showed decreased adhesion of PMNs (23 +/- 2.3% and 24.8 +/- 1.8%, respectively; P < .05) and an identical reduction resulted when sevoflurane (1 MAC) was applied only with the onset of reperfusion.     

Sevoflurane and isoflurane do not enhance the pre- and postischemic eicosanoid production in guinea pig hearts

Eicosanoids and volatile anesthetics can influence cardiac reperfusion injury. Accordingly, we analyzed the effects of sevoflurane and isoflurane applied in clinically relevant concentrations on the myocardial production of prostacyclin and thromboxane A2 (TxA2) and on heart function. Isolated guinea pig hearts, perfused with crystalloid buffer, performed pressure-volume work. Between two working phases, hearts were subjected to 15 min of global ischemia followed by reperfusion. The hearts received no anesthetic, 1 minimum alveolar anesthetic concentration (MAC) isoflurane (1.2 vol%), or 0.5 and 1 MAC sevoflurane (1 vol% and 2 vol%), either only preischemically or pre- and postischemically. In additional groups, cyclooxygenase function was examined by an infusion of 1 microM arachidonic acid (AA) in the absence and presence of sevoflurane. The variables measured included the myocardial production of prostacyclin, TxA2 and lactate, consumption of pyruvate, coronary perfusion pressure, and the tissue level of isoprostane 8-iso-PGF2alpha. External heart work, determined pre- and postischemically, served to assess recovery of heart function. Volatile anesthetics had no impact on postischemic recovery of myocardial function (50%-60% recovery), perfusion pressure, lactate production, or isoprostane content. Release of prostacyclin and TxA2 was increased in the early reperfusion phase 5-8- and 2-4-fold, respectively, indicating enhanced AA liberation. Isoflurane and sevoflurane did not augment the eicosanoid release. Only 2 vol% sevoflurane applied during reperfusion prevented the increased eicosanoid formation in this phase. Infusion of AA increased prostacyclin production approximately 200-fold under all conditions, decreased pyruvate consumption irreversibly, and markedly attenuated postischemic heart work (25% recovery). None of these effects were mitigated by 2 vol% sevoflurane. In conclusion, only sevoflurane at 2 vol% attenuated the increased liberation of AA during reperfusion. Decreased eicosanoid formation had no effect on myocardial recovery in our experimental setting while excess AA was deleterious. Because eicosanoids influence intravascular platelet and leukocyte adhesion and activation, sevoflurane may have effects in reperfused tissues beyond those of isoflurane. IMPLICATIONS: In an isolated guinea pig heart model, myocardial eicosanoid release was not increased by isoflurane or sevoflurane, either before or after ischemia. Sevoflurane (2 vol%) but not isoflurane attenuated the increased release of eicosanoids during reperfusion.     

Inhibition of Neutrophil Activation by Volatile Anesthetics Decreases Adhesion to Cultured Human Endothelial Cells

Background: Polymorphonuclear leukocytes (neutrophils, PMNs) have been shown to mediate vascular and tissue injury, leading to so-called systemic inflammatory response syndrome. The authors evaluated the effect of volatile anesthetics on neutrophil adhesion to human endothelial cells, focusing on whether the inhibitory effect observed is linked to an alteration in the function of endothelial cells or neutrophils.

Methods: The adhesion of human PMNs was quantified using cultured human umbilical vein endothelial cells (HUVECs). The increase in the number of adhering PMNs was assessed when HUVECs (with 1 mM hydrogen peroxide), PMNs (with 10 nM N-formyl-methionyl-leucyl-phenylalanine), or both were pre-stimulated. To determine the influence of volatile anesthetics on the adhesion of PMNs, the experiments were performed in the absence or presence of 0.5, 1, and 2 minimum alveolar concentration halothane, isoflurane, or sevoflurane, whereby HUVECs, PMNs, or both were pretreated with gas.

Results: Activation of HUVECs with hydrogen peroxide or stimulation of PMNs with N-formyl-methionyl-leucyl-phenylalanine resulted in a 2.5-fold increase in PMN adhesion. Preincubation of PMNs, separately, with halothane, isoflurane, or sevoflurane, respectively, abolished enhanced neutrophil adhesion to hydrogen peroxide-activated HUVECs and adhesion of PMNs prestimulated with N-formyl-methionyl-leucyl-phenylalanine to unstimulated HUVECs (maximal effect at 1 minimum alveolar concentration). No decrease in adhesion was detected when only HUVECs were pretreated with volatile anesthetics. Additional exposure of HUVECs and PMNs to volatile anesthetics had no inhibitory effect on adhesion greater than that seen when only PMNs were treated. Appropriately, the volatile anesthetics abolished the upward regulation of the adhesion molecule CD11b on PMNs (as evaluated at 1 minimum alveolar concentration each), whereas 1 minimum alveolar concentration halothane failed to affect the expression of P-selectin, an adhesion molecule on endothelial cells.     

Nonuniform behavior of intravenous anesthetics on postischemic adhesion of neutrophils in the guinea pig heart

Adhesion of polymorphonuclear neutrophils (PMN) to the coronary endothelium is a crucial step in the development of ischemic myocardial injury. We tested the possible effects of six widely used IV anesthetics on non- and postischemic coronary adhesion of PMN in isolated perfused guinea pig hearts. Hearts (n = 5-11/group) were perfused under conditions of constant coronary flow. After 15 min global warm ischemia, PMN (10(6)) were infused in the second minute of reperfusion. The number of cells reemerging in the coronary effluent within 2 min was expressed as a percentage of the total number of administered PMN. Anesthetics were given 20 min before ischemia and during reperfusion. In addition, the ability of the drugs to influence the oxidative burst reaction of PMN was assessed by measuring luminol-enhanced chemiluminescence in response to 0.1 microM N-formyl-L-methionyl-L-leucyl-L-phenylalanine. Under nonischemic conditions, 26.3% +/- 0.5% of the injected PMN did not acutely reemerge from the coronary system. Subjecting the hearts to ischemia augmented retention to 40.0% +/- 1.6% (P < 0.05). This postischemic stimulation of adhesion was fully prevented by ketamine (10 microM: 22.8% +/- 1.6%, 20 microM: 26.6% +/- 0.7%), thiopental (25 microM: 24.0% +/- 1.7%, 50 microM: 24.0% +/- 1.4%), and midazolam (1.5 microM: 29.0% +/- 0.9%, 3 microM: 26.4% +/- 1.4%). Propofol also inhibited the augmented postischemic retention at 25 microM (28.7% +/- 2.4%). However, 50 microM propofol, etomidate (0.5 and 1 microM), and fentanyl (1 microM) all had no effect. Only thiopental reduced the nonischemic adhesion value (14.0% +/- 3.7%). This may be linked to the direct antioxidative action of thiopental (50% reduction in oxidative burst activity). Whereas ketamine, midazolam, and propofol did not significantly influence oxidant production by PMN, etomidate and the lipid solvent Intralipid enhanced the burst reaction. This activating effect of the lipid component could explain the biphasic behavior of propofol emulsion. Despite some possible differences in efficacy, several IV anesthetics may protect the heart from PMN-mediated reperfusion injury. Implications: Ketamine, thiopental, and midazolam, but not etomodate or fentanyl, reduce postischemic adhesion of neutrophils in the coronary system of isolated perfused guinea pig hearts, suggesting a role in mitigating myocardial reperfusion injury.     

S(+)-ketamine, but not R(-)-ketamine, reduces postischemic adherence of neutrophils in the coronary system of isolated guinea pig hearts.

Polymorphonuclear neutrophils (PMN) play a crucial role in the initiation of reperfusion injury. In a previous study, we found that ketamine reduced the postischemic adherence of PMN to the intact coronary system of isolated guinea pig hearts. Because ketamine is a racemic mixture (1:1) of two optical enantiomers, we looked for possible differences in action between the stereoisomers. Seventy-six guinea pig hearts were perfused in the "Langendorff" mode under conditions of constant flow (5 mL/min) using modified Krebs-Henseleit buffer. After 15 min of global warm ischemia, freshly isolated human PMN (10(6)) were infused as a bolus into the coronary system during the second minute of reperfusion. PMN adhesion was expressed as the numeric difference between PMN recovered in the effluent and those applied. Series A hearts received 5 microM S(+), 5 microM R(-), or 10 microM racemic ketamine starting 20 min before ischemia and during reperfusion. In Series B hearts, 10 microM nitro-L-arginine, an inhibitor of NO synthase, was added to the perfusate. In Series C, PMN were preincubated for 15 min with 5 microM S(+)- or R(-)-ketamine. Coronary vascular leak was assessed by measuring the rate of formation of transudate on the epicardial surface. Ischemia/reperfusion without anesthetics increased coronary PMN adherence from 25.5% +/-2.3% (basal) to 35.3%+/-1.5% of the number applied. S(+)-ketamine reduced postischemic adherence in each series (A, 25.5%+/-5.1%; B, 22.5%+/-1.7%; C, 25.3%+/-7.7%), as did racemate (A, 26.4%+/-3.7%). Although 5 microM R(-)-ketamine had no effect on adhesion (A, 30.5%+/-6.7%; B, 34.3%+/-5.1%; C, 34.3%+/-4.3%), it significantly increased vascular leak in the presence of NOLAG. These findings indicate stereoselective differences in biological action between the two ketamine isomers: S(+)-ketamine inhibited PMN adherence, R(-)-ketamine worsened coronary vascular leak in reperfused isolated hearts. IMPLICATIONS: In this study, we demonstrated stereoselective differences in the biologic action of the two ketamine isomers in an animal model of myocardial ischemia. Polymorphonuclear neutrophil adherence to the coronary vasculature after ischemia was inhibited by S(+)-ketamine, whereas R(-)-ketamine increased coronary vascular fluid leak.     

The effect of isoflurane on neutrophil selectin and beta(2)-integrin activation in vitro

Isoflurane is reported to reduce ischemia-reperfusion injury. Lower expression of CD11b may be responsible for attenuated postischemic neutrophil adhesion to vascular endothelium. However, neutrophil adhesion to vascular endothelium is a multistep process involving several selectins and beta(2)-integrins. Therefore, we assessed whether isoflurane affects the activation of the selectins P-selectin glycoprotein ligand-1 (PSGL-1) and L-selectin and the beta(2)-integrins CD11a and CD11b. Whole blood was incubated for 60 min with 0.5 or 1 minimum alveolar anesthetic concentration (MAC) isoflurane. After incubation, neutrophils were activated with N-formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol-12-myristate-13-acetate (PMA). Activation of adhesion molecules was evaluated via flow cytometry, and 1 MAC isoflurane reduced the expression of CD11a in the unstimulated samples. After stimulation with FMLP and PMA, shedding of L-selectin was lower in the presence of isoflurane. Furthermore, 1 MAC isoflurane reduced FMLP-induced activation of CD11a and CD11b compared with unexposed blood samples. These results demonstrate that isoflurane affects the activation of three adhesion molecules involved in the multistep process of neutrophil recruitment. First, isoflurane inhibits the activation of L-selectin, which mediates the neutrophil tethering and rolling on the vascular endothelium. Second, isoflurane attenuates the activation of both beta(2)-integrins-CD11a and CD11b-which mediate firm adhesion and transendothelial migration. IMPLICATIONS: Adhesion of neutrophils to endothelial cells in reperfusion injury is mediated by different adhesion molecules. This study indicates that the inhibiting effect of isoflurane on neutrophil recruitment may be mediated by a decreased activation of the L-selectin and by attenuation of the activation of the beta(2)-integrins CD11a and CD11b.     

Recovery of contractile function of stunned myocardium in chronically instrumented dogs is enhanced by halothane or isoflurane

Following brief periods (5-15 min) of total coronary artery occlusion and subsequent reperfusion, despite an absence of tissue necrosis, a decrement in contractile function of the postischemic myocardium may nevertheless be present for prolonged periods. This has been termed "stunned" myocardium to differentiate the condition from ischemia or infarction. Because the influence of volatile anesthetics on the recovery of postischemic, reperfused myocardium has yet to be studied, the purpose of this investigation was to compare the effects of halothane and isoflurane on systemic and regional hemodynamics following a brief coronary artery occlusion and reperfusion. Nine groups comprising 79 experiments were completed in 42 chronically instrumented dogs. In awake, unsedated dogs a 15-min coronary artery occlusion resulted in paradoxical systolic lengthening in the ischemic zone. Following reperfusion active systolic shortening slowly returned toward control levels but remained approximately 50% depressed from control at 5 h. In contrast, dogs anesthetized with halothane or isoflurane (2% inspired concentration) demonstrated complete recovery of function 3-5 h following reperfusion. Because the anesthetics directly depressed contractile function, additional experiments were conducted in which a 15-minute coronary artery occlusion was produced during volatile anesthesia; however, each animal was allowed to emerge from the anesthetized state at the onset of reperfusion. Similar results were obtained in these experiments, demonstrating total recovery of contractile function within 3-5 h following reperfusion. Thus, despite comparable degrees of contractile dysfunction during coronary artery occlusion in awake and anesthetized dogs, the present results demonstrate that halothane and isoflurane produce marked improvement in the recovery of segment function following a transient ischemic episode. Therefore, volatile anesthetics may attenuate postischemic left ventricular dysfunction occurring intraoperatively and enhance recovery of regional wall motion abnormalities during reperfusion.     

Neutrophils pretreated with volatile anesthetics lose ability to cause cardiac dysfunction

BACKGROUND: Volatile anesthetics can precondition the myocardium against functional depression and infarction following ischemia-reperfusion. Neutrophil activation, adherence, and release of superoxide play major roles in reperfusion injury. The authors tested the hypothesis that pretreatment of neutrophils with a volatile anesthetic, i.e., simulated preconditioning, can blunt their ability to cause cardiac dysfunction. METHODS: Studies were performed in 60 buffer-perfused and paced isolated rat hearts. Left ventricular developed pressure served as an index of myocardial contractility. Polymorphonuclear neutrophils and/or drugs were added to coronary perfusate for 10 min, followed by 30 min of recovery. Platelet-activating factor was used to stimulate neutrophils. Pretreatment of neutrophils consisted of incubation with 1.0 minimum alveolar concentration (MAC) isoflurane or sevoflurane for 15 min, followed by washout. Additional studies were performed with 0.25 MAC isoflurane. Effects of superoxide dismutase were compared to those of volatile anesthetics. Superoxide production was measured by spectrophotometry. Neutrophil adherence to coronary vascular endothelium was estimated from the difference between neutrophils administered and recovered in coronary venous effluent. RESULTS: Activated neutrophils caused marked, persistent reduction (> 50%) in left ventricular developed pressure. Isoflurane and sevoflurane at 1.0 MAC and superoxide dismutase abolished this effect. Isoflurane and sevoflurane reduced superoxide production of activated neutrophils by 29% and 33%, respectively, and completely prevented the platelet-activating factor-induced increases in neutrophil adherence. Isoflurane at 0.25 MAC blunted, but did not abolish, the neutrophil-induced decreases in left ventricular developed pressure. CONCLUSION: Neutrophils pretreated with 1.0 MAC isoflurane or sevoflurane lost their ability to cause cardiac dysfunction, while those pretreated with a concentration of isoflurane as low as 0.25 MAC were partially inhibited. This action of the volatile anesthetics was associated with reductions in superoxide production and neutrophil adherence to the coronary vascular endothelium. Our findings suggest that inhibitory actions on neutrophil activation and neutrophil-endothelium interaction may contribute to the preconditioning effects of volatile anesthetics observed in vivo during myocardial ischemia-reperfusion.     

Isoflurane-enhanced Recovery of Canine Stunned Myocardium: Role for Protein Kinase C?

Background: Isoflurane enhances the functional recovery of postischemic, reperfused myocardium by activating adenosine A1 receptors and adenosine triphosphate-regulated potassium channels. Whether protein kinase C is involved in this process is unknown. The authors tested the hypothesis that inhibition of protein kinase C, using the selective antagonist bisindolylmaleimide, attenuates isoflurane-enhanced recovery of stunned myocardium in dogs.

Methods: Fifty dogs were randomly assigned to receive intracoronary vehicle or bisindolylmaleimide (2 or 8 [mu]g/min) in the presence or absence of isoflurane (1 minimum alveolar concentration). Five brief (5 min) coronary artery occlusions interspersed with 5-min reperfusion periods followed by 180 min of final reperfusion were used to produce myocardial stunning. Hemodynamics, regional segment shortening, and myocardial blood flow (radioactive microspheres) were measured at selected intervals.

Results: There were no differences in baseline hemodynamics, segment shortening, or coronary collateral blood flow between groups. Isoflurane significantly (P < 0.05) decreased heart rate, mean arterial pressure, rate pressure product, and the maximum rate of increase of left ventricular pressure (+dP/dtmax) in the presence or absence of bisindolylmaleimide. Sustained contractile dysfunction was observed in dogs that received vehicle (recovery of segment shortening to 12 +/- 8% of baseline), in contrast to those that received isoflurane (75 +/- 7% recovery). Bisindolylmaleimide at a dose of 2 [mu]g/min alone enhanced recovery of segment shortening (50 +/- 7% of baseline) compared with vehicle-pretreated dogs, and isoflurane in the presence of 2 [mu]g/min bisindolylmaleimide further enhanced recovery of contractile function (79 +/- 8% of baseline). In contrast, 8 [mu]g/min bisindolylmaleimide alone (32 +/- 12%) or combined with isoflurane (37 +/- 17%) did not enhance recovery of segment shortening compared with vehicle-pretreated dogs.     

Effects of sevoflurane and isoflurane on cardiac and coronary dynamics in chronically instrumented dogs

To assess the hemodynamic properties of the new inhalational anesthetic sevoflurane, 22 dogs were chronically instrumented for measurement of heart rate, aortic, left ventricular and left atrial pressures, cardiac output, and coronary blood flow. Dogs were randomly assigned to two groups, receiving either 1.2 and 2 MAC of sevoflurane (n = 11) or isoflurane (n = 11). At 1.2 and 2 MAC, sevoflurane produced an increase in heart rate (+60 +/- 12% and +54 +/- 9%, respectively), dose-dependent aortic hypotension (-22 +/- 4% and -38 +/- 4%, respectively), systemic vasodilation (-22 +/- 5% and -19 +/- 5%, respectively), dose-dependent decrease in stroke volume (-31 +/- 6% and -48 +/- 4%, respectively), and left ventricular dP/dt (-40 +/- 4% and -61 +/- 10%, respectively). Cardiac output decreased only at 2 MAC (-17 +/- 6%). Finally, coronary blood flow increased at 1.2 MAC of sevoflurane (+29 +/- 8%). Except for heart rate, sevoflurane and isoflurane produced similar effects. At 1.2 MAC, sevoflurane produced a greater increase in heart rate than isoflurane (+60 +/- 12% vs. +33 +/- 9%). The authors conclude that, except for heart rate, the effects of sevoflurane on cardiac function and coronary blood flow are almost identical to those induced by isoflurane in the chronically instrumented dog.     

Neutrophils Pretreated with Volatile Anesthetics Lose Ability to Cause Cardiac Dysfunction

Background: Volatile anesthetics can precondition the myocardium against functional depression and infarction following ischemia-reperfusion. Neutrophil activation, adherence, and release of superoxide play major roles in reperfusion injury. The authors tested the hypothesis that pretreatment of neutrophils with a volatile anesthetic, i.e., simulated preconditioning, can blunt their ability to cause cardiac dysfunction.

Methods: Studies were performed in 60 buffer-perfused and paced isolated rat hearts. Left ventricular developed pressure served as an index of myocardial contractility. Polymorphonuclear neutrophils and/or drugs were added to coronary perfusate for 10 min, followed by 30 min of recovery. Platelet-activating factor was used to stimulate neutrophils. Pretreatment of neutrophils consisted of incubation with 1.0 minimum alveolar concentration (MAC) isoflurane or sevoflurane for 15 min, followed by washout. Additional studies were performed with 0.25 MAC isoflurane. Effects of superoxide dismutase were compared to those of volatile anesthetics. Superoxide production was measured by spectrophotometry. Neutrophil adherence to coronary vascular endothelium was estimated from the difference between neutrophils administered and recovered in coronary venous effluent.

Results: Activated neutrophils caused marked, persistent reduction (> 50%) in left ventricular developed pressure. Isoflurane and sevoflurane at 1.0 MAC and superoxide dismutase abolished this effect. Isoflurane and sevoflurane reduced superoxide production of activated neutrophils by 29% and 33%, respectively, and completely prevented the platelet-activating factor-induced increases in neutrophil adherence. Isoflurane at 0.25 MAC blunted, but did not abolish, the neutrophil-induced decreases in left ventricular developed pressure.     

Sevoflurane inhalation at sedative concentrations provides endothelial protection against ischemia-reperfusion injury in humans

BACKGROUND: Endothelial cells can be protected against cytokine-induced toxicity by volatile anesthetics. The authors tested whether inhalation of sevoflurane at subanesthetic concentrations provides protection against postocclusive endothelial dysfunction induced by ischemia-reperfusion injury of the forearm in humans. METHODS: Five healthy male volunteers were enrolled in this study with crossover design. Each subject was randomly exposed to 15 min of forearm ischemia in the presence or absence of sevoflurane. Sevoflurane was inhaled at 0.5-1 vol% end-tidal concentrations from 15 min before ischemia until 5 min after the onset of reperfusion. Hyperemic reaction, an indicator of ischemic injury and endothelial function, was determined at 15 and 30 min of reperfusion using venous occlusion plethysmography. Also, markers of leukocyte activation (CD11b, CD42b) were measured by flow cytometry during reperfusion. RESULTS: Fifteen minutes of forearm ischemia followed by reperfusion diminished postocclusive endothelium-dependent hyperemic reaction at 15 and 30 min of reperfusion. Peri-ischemic inhalation of sevoflurane, targeted at 0.5-1 vol% end-tidal concentrations, markedly improved postocclusive hyperemic reaction. In addition, inhalation of sevoflurane attenuated activation of leukocytes, as measured by CD11b expression, after ischemia-reperfusion injury. No changes in CD42b expression were observed after ischemia-reperfusion of the forearm. CONCLUSIONS: These data suggest that human endothelium, a key component of all vital organs, is receptive to protection by sevoflurane in vivo. Peri-ischemic administration of sevoflurane mimics a combination of pharmacologic preconditioning and postconditioning and protects at even low sedative concentrations (< 1 vol%). Inhibition of leukocyte adhesion is likely to be involved in the protection.     

Isoflurane-enhanced recovery of canine stunned myocardium: role for protein kinase C?

BACKGROUND: Isoflurane enhances the functional recovery of postischemic, reperfused myocardium by activating adenosine A1 receptors and adenosine triphosphate-regulated potassium channels. Whether protein kinase C is involved in this process is unknown. The authors tested the hypothesis that inhibition of protein kinase C, using the selective antagonist bisindolylmaleimide, attenuates isoflurane-enhanced recovery of stunned myocardium in dogs. METHODS: Fifty dogs were randomly assigned to receive intracoronary vehicle or bisindolylmaleimide (2 or 8 microg/min) in the presence or absence of isoflurane (1 minimum alveolar concentration). Five brief (5 min) coronary artery occlusions interspersed with 5-min reperfusion periods followed by 180 min of final reperfusion were used to produce myocardial stunning. Hemodynamics, regional segment shortening, and myocardial blood flow (radioactive microspheres) were measured at selected intervals. RESULTS: There were no differences in baseline hemodynamics, segment shortening, or coronary collateral blood flow between groups. Isoflurane significantly (P<0.05) decreased heart rate, mean arterial pressure, rate pressure product, and the maximum rate of increase of left ventricular pressure (+dP/dt(max)) in the presence or absence of bisindolylmaleimide. Sustained contractile dysfunction was observed in dogs that received vehicle (recovery of segment shortening to 12+/-8% of baseline), in contrast to those that received isoflurane (75+/-7% recovery). Bisindolylmaleimide at a dose of 2 microg/min alone enhanced recovery of segment shortening (50+/-7% of baseline) compared with vehicle-pretreated dogs, and isoflurane in the presence of 2 microg/min bisindolylmaleimide further enhanced recovery of contractile function (79+/-8% of baseline). In contrast, 8 microg/min bisindolylmaleimide alone (32+/-12%) or combined with isoflurane (37+/-17%) did not enhance recovery of segment shortening compared with vehicle-pretreated dogs. CONCLUSIONS: The results indicate that protein kinase C inhibition using low doses of bisindolylmaleimide alone produces cardioprotection, and isoflurane further enhances this protection. In contrast, high doses of bisindolylmaleimide are not cardioprotective in the presence or absence of isoflurane. A role for protein kinase C during isoflurane-induced recovery of the stunned myocardium cannot be excluded.     

Endothelin-1 is involved in plasma mediated stimulation of neutrophil adherence during coronary artery bypass grafting.

OBJECTIVE: Myocardial ischaemia followed by reperfusion during coronary artery bypass grafting (CABG) is known to result in the activation of polymorphonuclear neutrophils (PMN). The activation of PMN during ischaemia/reperfusion may be a result of their direct contact with activated endothelial cells and/or an effect of stimuli released from ischaemic myocardium. Increased expression of adhesion molecules on the PMN surface, after activation, leads to coronary capillary plugging with a subsequent decrease in blood flow. The purpose of the study was to evaluate plasma-mediated stimulation of PMN adhesion during CABG and to verify if endothelin-1 (ET-1), known to be a potent stimulus for PMN, is involved in stimulation of neutrophils adhesion mediated by integrins. METHODS: Coronary sinus, peripheral artery and peripheral venous plasma samples were taken from 11 patients undergoing coronary surgery before aortal cross-clamping, at the beginning of reperfusion and 30 min thereafter. PMN isolated from five healthy volunteers were incubated with the plasma (20 samples per patient) in the presence of saline or a specific ET-1 receptor blocker, and PMN adherence to a microtiter plate covered with a monoclonal antibody against CD 18 antigen (beta-subunit of the integrin family of adhesion molecules) was evaluated. RESULTS: We have observed a significant increase in adhesion of PMN incubated in the presence of saline with the plasma taken from coronary sinus at the beginning of reperfusion (7.79+/-1.64% of adhering cells) as compared with plasma obtained before aortal cross-clamping from the same place (6.78+/-1.3%, P = 0.04) and from peripheral artery at the beginning of reperfusion (6.64+/-1.1%, P = 0.04, means +/- SEM). ET-1 receptor blocker, significantly decreased stimulation of PMN adhesion by coronary sinus plasma obtained at the beginning of reperfusion (6.7+/-1.51%, P = 0.02). Plasma levels of ET-1 (ELISA) in the samples taken from coronary sinus at the beginning of reperfusion, were higher than in samples obtained before myocardial ischaemia or 30 min after reperfusion. CONCLUSIONS: We conclude, that soluble stimuli capable of stimulation of PMN adhesion are released following myocardial ischaemia during CABG and ET-1 may be involved in PMN stimulation.     

The anticonvulsant effects of volatile anesthetics on penicillin-induced status epilepticus in cats

Volatile anesthetics may be used to treat status epilepticus when conventional drugs are ineffective. We studied 30 cats to compare the inhibitory effects of sevoflurane, isoflurane, and halothane on penicillin-induced status epilepticus. Anesthesia was induced and maintained with one of the three volatile anesthetics in oxygen. Penicillin G was injected into the cisterna magna, and the volatile anesthetic discontinued. Once status epilepticus was induced (convulsive period), the animal was reanesthetized with 0.6 minimum alveolar anesthetic concentration (MAC) of the volatile anesthetic for 30 min, then with 1.5 MAC for the next 30 min. Electroencephalogram and multiunit activity in the midbrain reticular formation were recorded. At 0.6 MAC, all anesthetics showed anticonvulsant effects. Isoflurane and halothane each abolished the repetitive spike phase in one cat; isoflurane reduced the occupancy of the repetitive spike phase (to 27%+/-22% of the convulsive period (mean +/- SD) significantly more than sevoflurane (60%+/-29%; P < 0.05) and halothane (61%+/-24%; P < 0.05), and the increase of midbrain reticular formation with repetitive spikes was reduced by all volatile anesthetics. The repetitive spikes were abolished by 1.5 MAC of the anesthetics: in 9 of 10 cats by sevoflurane, in 9 of 9 cats by isoflurane, and in 9 of 11 cats by halothane. In conclusion, isoflurane, sevoflurane, and halothane inhibited penicillin-induced status epilepticus, but isoflurane was the most potent. IMPLICATIONS: Convulsive status epilepticus is an emergency state and requires immediate suppression of clinical and electrical seizures, but conventional drugs may be ineffective. In such cases, general anesthesia may be effective. In the present study, we suggest that isoflurane is preferable to halothane and sevoflurane to suppress sustained seizure.     

Isoflurane and sevoflurane during reperfusion prevent recovery from ischaemia in mitochondrial KATP channel blocker pretreated hearts

BACKGROUND AND OBJECTIVE: Inhalation anaesthetics given only during post-ischaemic reperfusion have some protective effect against reperfusion injury in the heart. Adenosine triphosphate-regulated mitochondrial potassium channels have been shown to be an important mediator of cardioprotection. Thus, we investigated whether 5-hydroxydecanoate, a putative mitochondrial potassium channel blocker, prevents the cardioprotective effect of volatile anaesthetics. METHODS: Forty rats were randomly allocated to four groups of equal size: control group, 5-hydroxydecanoate group, 5-hydroxydecanoate + sevoflurane group and 5-hydroxydecanoate + isoflurane group. Seven minutes after the start of perfusion, normal saline (control group) or 5-hydroxydecanoate (the other groups) was administered. Ten minutes after the start of perfusion, the heart was rendered globally ischaemic for 10 min. One minute before the end of the ischaemic period, 2.7% sevoflurane or 1.4% isoflurane were administered in the 5-hydroxydecanoate + sevoflurane or 5-hydroxydecanoate + isoflurane groups respectively. The heart was reperfused for 10 min. RESULTS: Adenosine triphosphate content at the end of reperfusion in the 5-hydroxydecanoate + sevoflurane group was significantly lower (P < 0.05) than those in the control and the 5-hydroxydecanoate + isoflurane groups (19.9 +/- 8.7, 28.1 +/- 3.4 and 30.4 +/- 2.3 micromol g(-1), respectively). In addition, the combination of inhalation anaesthetics and 5-hydroxydecanoate decreased the ratios of recovered hearts from ischaemia (5-hydroxydecanoate + sevoflurane group: 40%, 5-hydroxydecanoate + isoflurane group 50%). CONCLUSION: 5-hydroxydecanoate alone caused no significant changes in haemodynamics and myocardial metabolism. However, the combination of 5-hydroxydecanoate and volatile anaesthetics impaired the recovery from ischaemia. Although animal data cannot be extrapolated to human beings, we suggest that more attention be paid to patients on sulphonylurea drugs, which inhibit potassium channels, when they are anaesthetized with volatile anaesthetics.     

Interactions of nicardipine to inhalation anesthetics sevoflurane and isoflurane

The hemodynamic effects and pharmacokinetics of nicardipine under general anesthesia were compared between two different volatile anesthetics, sevoflurane and isoflurane. Sixteen adult neurosurgery patients were divided into sevoflurane and isoflurane groups. Anesthesia was maintained with either sevoflurane or isoflurane (0.5–1.5%) and nitrous oxide in oxygen. When the blood pressure was stabilized [0.5 minimum alveolar concentration (MAC) in both anesthetics] during surgery, nicardipine 1 mg, i.v. was administered. Plasma catecholamines and nicardipine concentration were measured, and the pharmacokinetics of nicardipine were calculate. The decrease in blood pressure and the increase in heart rate 30 min after nicardipine administration were significant in the isoflurane group but not in the sevoflurane group. Although plasma catecholamine levels increased after nicardipine administration in the isoflurane group, no significant changes were observed in the sevoflurane group. The sevoflurane group had a significantly longer elimination half-life, a larger area under the plasma concentration curve, and smaller clearance of nicardipine compared to the isoflurane group. In summary, the effects of nicardipine on blood pressure and heart rate were significantly longer under isoflurane anesthesia than under sevoflurane anesthesia. However, the etabolism and excretion of nicardipine were significantly delayed under sevoflurane anesthesia.     

Isoflurane and sevoflurane precondition against neutrophil-induced contractile dysfunction in isolated rat hearts

BACKGROUND: The authors tested the hypothesis that pretreatment with isoflurane or sevoflurane can protect the heart against neutrophil-induced contractile dysfunction. METHODS: Studies were conducted in buffer-perfused and paced isolated rat hearts. Left ventricular developed pressure served as an index of contractility. Pretreatment consisted of administration of 1.0 minimum alveolar concentration isoflurane or sevoflurane for 15 min followed by a 10-min washout and was performed in the absence and presence of the adenosine triphosphate-sensitive potassium channel inhibitor glibenclamide (10 microM). Polymorphonuclear neutrophils and platelet-activating factor were then added to the perfusate for 10 min, followed by 30 min of recovery. Neutrophil retention was assessed from the difference between those administered and collected in coronary effluent and measurements of myeloperoxidase in myocardial samples. Isolated hearts were also used to assess the effect of volatile anesthetic pretreatment on cardiac dysfunction caused by enzymatically generated superoxide. In additional studies, the authors evaluated the effect of volatile anesthetic pretreatment on the adherence of neutrophils to isolated rat aortic segments. RESULTS: Platelet-activating factor-stimulated neutrophils caused marked and persistent reductions (> 50%) in left ventricular developed pressure. Pretreatment with either isoflurane or sevoflurane abolished these effects, as well as the associated increases in neutrophil retention. Glibenclamide did not alter these actions of the anesthetics. Pretreatment with either volatile anesthetic attenuated the reductions in left ventricular developed pressure caused by exogenous superoxide and abolished the increases in neutrophil adherence in the aortic segments. CONCLUSION: Isoflurane and sevoflurane preconditioned the heart against neutrophil-induced contractile dysfunction. This action was associated with an inhibition to neutrophil adherence and likely involved an increased resistance of the myocardium to oxidant-induced injury; the adenosine triphosphate-sensitive potassium channels played no apparent role.