Eiji Hashiba

Volatile anesthetics augment expression of proinflammatory cytokines in rat alveolar macrophages during mechanical ventilation

BACKGROUND Previous studies indicate that anesthesia and surgery induce an inflammatory reaction in alveolar macro phages. However,they filed to independently evaluate the relative contributions of factors including mechanical ventilation, general anesthesia, and surgical stress. Therefore, the authors tested the hypothesis that inflammatory reactions at the cellular level in alveolar macrophages are induced within 2 h of inhalation of volatile anesthetics under mechanical ventilation. METHODS After administration of pentobarbital, rats were allocated to the nonventilated control or spontaneous or mechanical ventilation (n = 15/group) for 2 h at a fraction of inspired oxygen (FI(O2)) of 0.21. In a separate series of experiments, rats were mechanically ventilated without volatile anesthesia, or during exposure to halothane, enflurane, isoflurane, or sevoflurane (n = 15/group). Pulmonary lavage was performed, and RNA was extracted from harvested cells. The mRNA for the proinflammatory cytokines interleukin (IL)-1alpha, IL-1beta, IL-6, macrophage inflammatory protein-2 (MIP-2), interferon gamma (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) were measured by semiquantitative reverse transcription-polymerase chain reaction using beta-actin as an internal standard. Pulmonary lavage concentrations of these cytokines were measured by enzyme-linked immunoassay. RESULTS The lavage cell count and cytology were similar in each series of the experiment. Gene expression of MIP-2 and TNF-alpha was greater during mechanical than spontaneous ventilation and nonventilation control However, the concentrations of cytokines except MIP-2 and TNF-alpha were less than detection levels. During exposure to volatile anesthetics, gene expression for IL-1beta, MIP-2, IFN-gamma, and TNF-alpha all increased significantly compared with mechanical ventilation alone. Significant increases in lavage concentrations of MIP-2 and TNF-alpha were also observed. CONCLUSIONS Gene expression of proinflammatory cytokines increase after inhalation of volatile anesthetics under mechanical ventilation. These data indicate that inhalation of volatile anesthetics under mechanical ventilation induces an inflammatory response at the transcriptional level within 2 h.

Supplemental Intraoperative Oxygen Augments Antimicrobial and Proinflammatory Responses of Alveolar Macrophages

Background The first goal was to test the hypothesis that 100% inspired oxygen maintained for approximately 8 h intraoperatively is not associated with impaired pulmonary oxygenation. The authors also tested the hypothesis that intraoperative inhalation of 100% oxygen augments proinflammatory and antimicrobial responses of alveolar macrophages during anesthesia and surgery. Methods The authors studied patients administered 100% oxygen (n = 30) and 30% oxygen (n = 30) during propofol–fentanyl general anesthesia. Alveolar macrophages were harvested by bronchoalveolar lavage immediately, 2, 4, and 6 h after induction of anesthesia, and at the end of surgery.The authors measured “opsonized” and “unopsonized” phagocytosis and microbicidal activity. RNA was extracted from harvested cells and cDNA was synthesized. The expression of interleukin(IL)–1&bgr;, IL-6, IL-8, interferon-&ggr; (IFN-&ggr;) and tumor necrosis factor &agr; (TNF-&agr;) was measured by semiquantitative polymerase chain reaction. Results Gene expression of all proinflammatory cytokines except IL-6 increased fourfold to 20-fold over time in both groups. However, expression of TNF-&agr; and IL-8, IFN-&ggr;, and IL-6 and IL-1&bgr; was 2–20 times greater in patients administered 100% than in those administered 30% oxygen. Unopsonized and opsonized phagocytosis and microbicidal activity decreased progressively, with the decreases being nearly twice as great during inhalation of 30% oxygen versus 100% oxygen. Conclusion Inhalation of 100% oxygen improved intraoperative decreases in phagocytic and microbicidal activity possibly because expression of proinflammatory cytokines was augmented. These data therefore suggest that intraoperative inhalation of 100% oxygen augments antimicrobial and proinflammatory responses in alveolar macrophages during anesthesia and surgery.

The relaxant effect of propofol on guinea pig tracheal muscle is independent of airway epithelial function and beta-adrenoceptor activity.

UNLABELLED Airway epithelium and vascular endothelium modulate the tension of the underlying smooth muscle by releasing relaxing factors such as prostanoids and nitric oxide (NO). We investigated whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. Tracheal spirals of female guinea pigs were mounted in water-jacketed organ baths filled with Krebs-bicarbonate buffer aerated with 95% O2 and 5% CO2 at 37 degrees C. Changes in isometric tension of the specimens were measured with a force-displacement transducer and recorded with a polygraph. Propofol (10(-4) to 10(-3) M) inhibited carbachol (CCh)-, histamine (HA)-, or endothelin-1-induced contractions of the muscles in a dose-dependent manner. Neither mechanical removal of the epithelial layer, chemical inhibition of epithelial synthesis of prostanoids, nor NO affected the relaxant effect of propofol on CCh- or HA-induced tracheal contraction. Furthermore, the blockade of beta-adrenoceptors did not change the relaxant effect of propofol. These results indicate that the relaxant effect of propofol on the airway smooth muscle is independent of the epithelial function or beta-adrenoceptor activity. Propofol is an excellent anesthetic for patients with hyperreactive airways in which the epithelial layer is damaged. IMPLICATIONS Airway epithelium, as well as vascular endothelium, plays an important role in modulating the baseline tone and reactivity of underlying smooth muscle. We investigated, in vitro, whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. We suggest that propofol relaxes airway smooth muscle independently of the epithelial function.

Effects of propofol on bronchoconstriction and bradycardia induced by vagal nerve stimulation

Background:  Vagolysis has been considered as a mechanism by which propofol produces bronchodilation. However, it has also been suggested that propofol‐induced bradycardia may result from increased vagal tone. In this study, we have determined whether propofol has vagolytic effects on both the airway and cardiovascular system.

Urotensin II evokes neurotransmitter release from rat cerebrocortical slices.

Urotensin II (UII) has been reported to modulate rapid eye movement (REM) sleep via activation of brainstem cholinergic neurons and REM sleep is regulated by locus coerleus (LC)-cerebrocortical noradrenergic neurons. We hypothesized that UII may activate LC-cerebrocortical noradrenergic neurons. To test this hypothesis, we have examined the effects of UII on norepinephrine release from rat cerebrocortical slices. In addition, the effect of the putative UT receptor antagonist [Pen(5), DTrp(7), Dab(8)]UII(4-11) (UFP-803) was assessed. We have compared this with other wakefulness-promoting neurotransmitters such as dopamine, glutamate, serotonin and histamine. We also studied the effects of UII and UFP-803 on intracellular Ca(2+) ([Ca(2+)]i) in HEK293 cells stably expressing rat UT receptor (HEK293-rUT cells). UII produced a time- (peaking at approximately 10 min following stimulation with 10nM) and concentration-dependent increase in norepinephrine release with pEC(50) and E(max) (% of basal) values of 8.78+/-0.17 (1.65 nM) and 138+/-2%, respectively. UII also evoked dopamine, serotonin and histamine release with similar pEC(50) values. UII increased glutamate release but only at high concentrations (<100 nM) and this failed to saturate. UII markedly increased [Ca(2+)](i) in HEK293-rUT cells in a concentration-dependent manner with pEC(50) of 8.26+/-0.24. The UT antagonist UFP-803 reversed both UII-increased norepinephrine release from the cerebrocortical slices (pK(B)=8.98) and [Ca(2+)](i) (pK(B)=8.87) in HEK293-rUT cells. Collectively these data suggest that UII evokes the release of norepinephrine via UT receptor activation and produces similar effects on other wakefulness-promoting neurotransmitters: these neurochemical actions of UII may be important for the control of the sleep-wake cycle.

Milrinone attenuates serotonin-induced pulmonary hypertension and bronchoconstriction in dogs

We determined whether milrinone, a phosphodiesterase III inhibitor, attenuates serotonin-induced (5-hydroxytryptamine [5HT]) pulmonary hypertension (PH) and bronchoconstriction. Dogs were anesthetized with pentobarbital (30 mg/kg + 2 mg · kg−1 · h−1). Bronchoconstriction and PH were elicited by 5HT (10 &mgr;g/kg + 1.0 mg · kg−1 · h−1). Pulmonary vascular resistance was used to assess PH. Bronchoconstriction was also assessed by changes in bronchial cross-sectional area obtained from our bronchoscopic method. At 30 min after 5HT infusion started, seven dogs were given milrinone: 0 (saline), 5, 50, 500, and 5000 &mgr;g/kg at 10-min intervals. The other 12 dogs were given milrinone 5000 &mgr;g/kg 30 min after 5HT infusion, and 5 min later were given propranolol 0.2 mg/kg (n = 6) or saline (n = 6) IV. The 5HT significantly increased percentage of pulmonary vascular resistance to 208% ± 27% and decreased percentage of bronchial cross-sectional area to 52% ± 5% of the basal. Milrinone significantly attenuated both PH and bronchoconstriction in a dose-dependent manner. However, −log 50% effective concentration (mean ED50 in &mgr;g/kg) of milrinone for bronchoconstriction: 4.32 ± 0.13 (47.6) was significantly smaller than that for PH: 3.84 ± 0.29 (144.9) (P < 0.01). In addition, the spasmolytic effects of milrinone (5000 &mgr;g/kg) were not antagonized by propranolol, although this dose significantly increased plasma catecholamines. In conclusion, milrinone attenuates 5HT-induced PH and bronchoconstriction; however, this drug may be more sensitive to phosphodiesterase III in the airway smooth muscle than in pulmonary vascular smooth muscle. In addition, the relaxant effects could not be caused by &bgr;-adrenoceptor activation because &bgr;-blocker did not antagonize. Implications: We studied the effects of milrinone on serotonin-induced pulmonary hypertension and bronchoconstriction in dogs. Milrinone produces pulmonary vasodilation and bronchodilation, whose effects may not be caused by &bgr;-adrenoceptor activation. In addition, this drug may be more sensitive to phosphodiesterase III in the airway smooth muscle than that in pulmonary vascular smooth muscle.

Neither dynamic, static, nor volumetric variables can accurately predict fluid responsiveness early after abdominothoracic esophagectomy.

BackgroundHypotension is common in the early postoperative stages after abdominothoracic esophagectomy for esophageal cancer. We examined the ability of stroke volume variation (SVV), pulse pressure variation (PPV), central venous pressure (CVP), intrathoracic blood volume (ITBV), and initial distribution volume of glucose (IDVG) to predict fluid responsiveness soon after esophagectomy under mechanical ventilation (tidal volume >8 mL/kg) without spontaneous respiratory activity.MethodsForty-three consecutive non-arrhythmic patients undergoing abdominothoracic esophagectomy were studied. SVV, PPV, cardiac index (CI), and indexed ITBV (ITBVI) were postoperatively measured by single transpulmonary thermodilution (PiCCO system) after patient admission to the intensive care unit (ICU) on the operative day. Indexed IDVG (IDVGI) was then determined using the incremental plasma glucose concentration 3 min after the intravenous administration of 5 g glucose. Fluid responsiveness was defined by an increase in CI >15% compared with pre-loading CI following fluid volume loading with 250 mL of 10% low molecular weight dextran.ResultsTwenty-three patients were responsive to fluids while 20 were not. The area under the receiver-operating characteristic (ROC) curve was the highest for CVP (0.690) and the lowest for ITBVI (0.584), but there was no statistical difference between tested variables. Pre-loading IDVGI (r = −0.523, P <0.001), SVV (r = 0.348, P = 0.026) and CVP (r = −0.307, P = 0.046), but not PPV or ITBVI, were correlated with a percentage increase in CI after fluid volume loading.ConclusionsThese results suggest that none of the tested variables can accurately predict fluid responsiveness early after abdominothoracic esophagectomy.

The Effects of Benzodiazepines on Urotensin II-Stimulated Norepinephrine Release from Rat Cerebrocortical Slices

BACKGROUND: Urotensin II (UII) and its receptor (UT) are implicated in mood disorders, such as stress and anxiety, and this may result, at least in part, from increased norepinephrine release from the cerebral cortex. Benzodiazepines have been widely used as hypnotics and anxiolytics, producing a decrease in cerebrocortical norepinephrine release. We hypothesized that there was some interaction between benzodiazepines and the UII system in the cerebral cortex. METHODS: In the present study, we have examined the effects of benzodiazepines on UII-increased norepinephrine release from rat cerebrocortical slices and intracellular Ca2+ concentrations ([Ca2+]i) in HEK293 cells expressing rat UT receptor (HEK293-rUT cells). RESULTS: Midazolam, diazepam and flunitrazepam concentration-dependently inhibited UII-evoked norepinephrine release but did not affect [Ca2+]i. The IC50 of midazolam for inhibition of UII-evoked norepinephrine release (0.32 &mgr;M, P < 0.01) was significantly lower than that of diazepam (187 &mgr;M) or flunitrazepam (40 &mgr;M). The inhibitory effects of midazolam on UII-evoked norepinephrine release were significantly attenuated by flumazenil, a benzodiazepine site antagonist. CONCLUSION: The present study suggests that midazolam, at clinically relevant concentration, significantly inhibited UII-evoked norepinephrine release. This inhibitory effect may be partially mediated via central benzodiazepine receptors.

Use of initial distribution volume of glucose to determine fluid volume loading in pulmonary thromboembolism and right ventricular myocardial infarction

We report a case of acute right ventricular myocardial infarction (right AMI) following pulmonary thromboembolism (PTE). Following percutaneous coronary intervention, the patient was treated in our intensive care unit (ICU) with intraortic balloon pumping, anticoagulants, and plasma expansion. Fluid overload may cause a further leftward shift of the interventricular septum in patients with PTE, resulting in decreased cardiac output (CO). The initial distribution volume of glucose (IDVG) has been reported to indicate central extracellular fluid volume. As both PTE and right AMI affect cardiac filling pressures, such as central venous pressure (CVP) and pulmonary artery wedge pressure (PAWP), we measured IDVG in order to evaluate the patient’s cardiac preload, comparing it with the cardiac filling pressures. Fluid volume loading over 12 h yielded an obvious increase in IDVG. However, low arterial blood pressure and CO, associated with high CVP, remained unchanged and were accompanied by deteriorating pulmonary oxygenation. Accordingly, volume loading was discontinued and the rates of infusion of catecholamines were increased instead. At 12 h thereafter, IDVG became normal, and both CO and blood pressure became improved. However, the cardiac filling pressures remained increased. Although the patient died on the subsequent day, this case report could support the usefulness of IDVG as a fluid volume marker in critically ill patients, especially those with right AMI.

Unventilated airway is time-dependently constricted in paralyzed dogs.

Background Apnea has been reported to produce bronchoconstriction and to cause hypoxia, hypercapnia, and modulation of vagal afferent nerves, which also change airway tone. In this study, the authors determined the mechanism of apnea-induced bronchoconstriction. Methods Twenty-eight dogs anesthetized and paralyzed were assigned to four groups (n = 7 each): apnea after artificial ventilation with 50% and 100% O2 groups (apnea–50% O2 and apnea–100% O2 groups, respectively), an apnea plus vagotomy group (fraction of inspired oxygen [Fio2] = 1.0), and a one-lung ventilation group (Fio2 = 1.0). The trachea was intubated with a single- or double-lumen tube in the three apnea groups or the one-lung ventilation group, respectively. The bronchial cross-sectional area (BCA) was assessed by the authors’ bronchoscopic method. In the apnea–100% O2 and apnea plus vagotomy groups, a respirator was turned off for 5 min to produce apnea. In the apnea–50% O2 group, apnea was produced for 3 min. In the one-lung ventilation group, the right lumen was blocked for 5 min, and 15 min later, the left lumen was blocked for 5 min. BCA, arterial oxygen tension (Pao2), and arterial carbon dioxide tension (Paco2) were assessed every minute. Results The BCA in intact dogs time-dependently decreased by approximately 20% and 40% at 3 and 5 min after apnea started, respectively, whereas they did not in vagotomized dogs. In the apnea–50% O2 and apnea–100% O2 groups, bronchoconstriction could occur without hypoxemia, although hypercapnia was observed in all dogs. In the one-lung ventilation group, despite the fact that Paco2 increased by only 2 mmHg without hypoxemia, unventilated BCA time-dependently decreased by 33.6 ± 10.3%, whereas ventilated BCA did not. Conclusion The current study suggests that the unventilated airway may constrict spontaneously. In addition, the airway constriction could be vagally mediated but not due to hypoxia and hypercapnia.