Permissive hypercapnia, involving tolerance to elevated Pa(CO(2)), is associated with reduced acute lung injury (ALI), thought to result from reduced mechanical stretch, and improved outcome in ARDS. However, deliberately elevating inspired CO(2) concentration alone (therapeutic hypercapnia, TH) protects against ALI in ex vivo models. We investigated whether TH would protect against ALI in an in vivo model of lung ischemia-reperfusion (IR). Anesthetized open chest rabbits were ventilated (standard eucapnic settings), and were randomized to TH (FI(CO(2)) 0.12) versus control (FI(CO(2)) 0.00). Pa(CO(2)) and arterial pH values achieved in the TH versus CON groups were 101 +/- 3 versus 44.4 +/- 4 mm Hg and 7.10 +/- 0.03 versus 7.37 +/- 0.03, respectively. Following left lung ischemia and reperfusion, TH versus control was associated with preservation of lung mechanics, attenuation of protein leakage, reduction in pulmonary edema, and improved oxygenation. Indices of systemic protection included improved acid-base and lactate profile, in the absence of systemic hypoxemia. In the TH group, mean BALF TNF-alpha levels were 3.5% of CON levels (p < 0.01), and mean 8-isoprostane levels were 30% of CON levels (p = 0.02). Western blot analysis demonstrated reduced lung tissue nitrotyrosine in TH, indicating attenuation of tissue nitration. Finally, preliminary data suggest that TH may attenuate apoptosis following lung IR. We conclude that in the current model TH is protective versus IR lung injury and mechanisms of protection include preservation of lung mechanics, attenuation of pulmonary inflammation, and reduction of free radical mediated injury. If these findings are confirmed in additional models, TH may become a candidate for clinical testing in critical care.

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Background Postoperative myocardial injury occurs frequently after noncardiac surgery and is strongly associated with mortality. Intraoperative hypotension (IOH) is hypothesized to be a possible cause. The aim of this study was to determine the association between IOH and postoperative myocardial injury. Methods This cohort study included 890 consecutive patients aged 60 yr or older undergoing vascular surgery from two university centers. The occurrence of myocardial injury was assessed by troponin measurements as part of a postoperative care protocol. IOH was defined by four different thresholds using either relative or absolute values of the mean arterial blood pressure based on previous studies. Either invasive or noninvasive blood pressure measurements were used. Poisson regression analysis was used to determine the association between IOH and postoperative myocardial injury, adjusted for potential clinical confounders and multiple comparisons. Results Depending on the definition used, IOH occurred in 12 to 81% of the patients. Postoperative myocardial injury occurred in 131 (29%) patients with IOH as defined by a mean arterial pressure less than 60 mmHg, compared with 87 (20%) patients without IOH (P = 0.001). After adjustment for potential confounding factors including mean heart rates, a 40% decrease from the preinduction mean arterial blood pressure with a cumulative duration of more than 30 min was associated with postoperative myocardial injury (relative risk, 1.8; 99% CI, 1.2 to 2.6, P &lt; 0.001). Shorter cumulative durations (less than 30 min) were not associated with myocardial injury. Postoperative myocardial infarction and death within 30 days occurred in 26 (6%) and 17 (4%) patients with IOH as defined by a mean arterial pressure less than 60 mmHg, compared with 12 (3%; P = 0.08) and 15 (3%; P = 0.77) patients without IOH, respectively. Conclusions In elderly vascular surgery patients, IOH defined as a 40% decrease from the preinduction mean arterial blood pressure with a cumulative duration of more than 30 min was associated with postoperative myocardial injury.

The role of a cytosolic phospholipase A 2 -α (cPLA 2 -α) in neutrophil arachidonic acid release, plateletactivating factor (PAF) biosynthesis, NADPH oxidase activation, and bacterial killing in vitro, and the innate immune response to bacterial infection in vivo was examined. cPLA 2 -α activity was blocked with the specific cPLA 2 -α inhibitor, Pyrrolidine-1 (human cells), or by cPLA 2 -α gene disruption (mice). cPLA 2 -α inhibition or gene disruption led to complete suppression of neutrophil arachidonate release and PAF biosynthesis but had no effect on neutrophil NADPH oxidase activation, FcγII/III or CD11b surface expression, primary or secondary granule secretion, or phagocytosis of Escherichia coli in vitro. In contrast, cPLA 2 -α inhibition or gene disruption diminished neutrophil-mediated E. coli killing in vitro, which was partially rescued by exogenous arachidonic acid or PAF but not leukotriene B 4 . Following intratracheal inoculation with live E. coli in vivo, pulmonary PAF biosynthesis, inflammatory cell infiltration, and clearance of E. coli were attenuated in cPLA 2 -α (−/−) mice compared with wild type littermates. These studies identify a novel * This work was supported by grants from The Physicians of Ontario through The P.S.I. Foundation (Grant 01-12 (to B. B. R.) and 98-049

The bacterial tripeptide formyl-Met-Leu-Phe (fMLP) induces the secretion of enzyme(s) with phospholipase A 2 (PLA 2 ) activity from human neutrophils. We show that circulating human neutrophils express groups V and X sPLA 2 (GV and GX sPLA 2 ) mRNA and contain GV and GX sPLA 2 proteins, whereas GIB, GIIA, GIID, GIIE, GIIF, GIII, and GXII sPLA 2 s are undetectable. GV sPLA 2 is a component of both azurophilic and specific granules, whereas GX sPLA 2 is confined to azurophilic granules. Exposure to fMLP or opsonized zymosan results in the release of GV but not GX sPLA 2 and most, if not all, of the PLA 2 activity in the extracellular fluid of fMLPstimulated neutrophils is due to GV sPLA 2 . GV sPLA 2 does not contribute to fMLP-stimulated leukotriene B 4 production but may support the anti-bacterial properties of the neutrophil, because 10 -100 ng per ml concentrations of this enzyme lead to Gram-negative bacterial membrane phospholipid hydrolysis in the presence of human serum. By use of a recently described and specific inhibitor of cytosolic PLA 2 -␣ (group IV PLA 2 ␣), we show that this enzyme produces virtually all of the arachidonic acid used for the biosynthesis of leukotriene B 4 in fMLP-and opsonized zymosan-stimulated neutrophils, the major eicosanoid produced by these pro-inflammatory cells.

Background-Pharmacological inhibition of cyclooxygenase-2 increases the risk of myocardial infarction (MI) and stroke.Microsomal prostaglandin (PG) E 2 synthase-1 (mPGES-1), encoded by the Ptges gene, functions downstream from cyclooxygenase-2 in the inducible PGE 2 biosynthetic pathway. We caused acute MI in Ptges ϩ/ϩ and Ptges Ϫ/Ϫ mice to define the role of mPGES-1 in cardiac ischemic injury. Methods and Results-Twenty-eight days after MI, Ptges Ϫ/Ϫ mice develop more left ventricular (LV) dilation, have worse LV systolic and diastolic function, and have higher LV end-diastolic pressure than Ptges ϩ/ϩ mice but have similar pulmonary wet-to-dry weight ratios, cardiac mass, infarct size, and mortality. The length-to-width ratio of individual cardiomyocytes is significantly greater in Ptges Ϫ/Ϫ than Ptges ϩ/ϩ mice after MI, a finding consistent with eccentric cardiomyocyte hypertrophy in Ptges Ϫ/Ϫ mice. Expression of atrial natriuretic peptide, brain natriuretic peptide, and ␣-and ␤-myosin heavy chain, markers of ventricular hypertrophy, is higher in the LV of Ptges Ϫ/Ϫ than Ptges ϩ/ϩ mice after MI. Ptges ϩ/ϩ mice express cyclooxygenase-2 and mPGES-1 protein in inflammatory cells adjacent to the infarct after MI but do not express these proteins in cardiomyocytes. Ptges Ϫ/Ϫ mice express cyclooxygenase-2 in inflammatory cells adjacent to the infarct and do not express mPGES-1 in any cells in the heart. Levels of PGE 2 but not PGD 2 , thromboxane A 2 , PGI 2 , or PGF 2␣ are higher in the infarct and LV remote from the infarct after MI in Ptges ϩ/ϩ than Ptges Ϫ/Ϫ mice. Conclusions-In