Alexander Mu, Alexander Romaschin, Albert K.-Y. Tsui, Nadine Shehata,W. Scott Beattie and C. David MazerAbstractPurpose Transfusionof allogeneic red blood cells (RBCs) is one of the main treatments of acuteanemia secondary to blood loss and fluid resuscitation within the operatingroom. Decisions to transfuse blood are based largely on intermediate biologicalmarkers (hemoglobin, arterial oxygen saturation, blood pressure, heart rate)which may not accurately reflect inadequacy of tissue oxygen delivery. Based onexperimental studies, we hypothesized that anemia-induced tissue hypoxiaactivates adaptive mechanisms which promote local vascular nitric oxide (NO)production to improve tissue perfusion and survival during acute anemia. Hemoglobin(Hb) oxidation to methemoglobin (MetHb) may be a byproduct of such local NOproduction. Therefore, we tested the hypothesis that MetHb is a biomarker ofhypoxic-anemic stress during acute hemodilution associated with cardiopulmonarybypass.Methods Withinstitutional ethics approval, routine laboratory arterial blood gas andco-oximetry values were obtained from 295 patients undergoing heart surgeryduring February 1 to September 30, 2010, and the values were assessedretrospectively. All samples with an arterial oxygen saturation value 90% wereincluded (n = 1,421). The maximal change in Hb associated with hemodilution oncardiopulmonary bypass was determined within 48 hr of surgery (n = 180). Achart review was performed to determine the incidence of RBC transfusion andexogenous nitrate administration. All anonymous data were analyzed by linearregression to determine the relationship between Hb and MetHb. A WilcoxonSigned Rank Test and Students t test were used to determine changes in Hb, MetHb,and carboxyhemoglobin (CarboxHb) levels. All data are presented as mean andsignificance was assigned at P < 0.05.Results Asignificant decrease in Hb [118 (20) gL1 vs 94 (18) gL1] was associatedwith an increase in MetHb [0.88 (0.22)% vs 0.95 (0.24)%] (P < 0.001 forboth), but not CarboxHb [1.08 (0.47)% vs 1.08 (0.49)%]. Regression analysisrevealed a significant relationship between the change in Hb and MetHb (F =40.3; P < 0.001) but not between the change in Hb and CarboxyHb (F = 0.2; P= 0.694). This correlation was not influenced by RBC transfusion or exogenousnitrate use.Conclusions A negativecorrelation was observed between the change in Hb and MetHb in patientsundergoing cardiac surgery and cardiopulmonary bypass. These data support thepreviously unreported hypothesis that MetHb may be a marker of anemic stressassociated with reduced tissue perfusion during acute hemodilution in humans.Further prospective studies are needed to determine if these changes in MetHbare linked to adverse outcomes in patients undergoing cardiac surgery.---------------------------------------------------------------------------------------------------------------------------------Short-termpreoperative smoking cessation and postoperative complications: a systematic reviewand meta-analysishttp://www.springerlink.com/content/28103111g1644560/Jean Wong,David Paul Lam, Amir Abrishami, Matthew T. V. Chan and Frances ChungAbstractPurpose Theliterature was reviewed to determine the risks or benefits of short-term (lessthan four weeks) smoking cessation on postoperative complications and to derivethe minimum duration of preoperative abstinence from smoking required to reducesuch complications in adult surgical patients.Source We searchedMEDLINE, EMBASE, Cochrane, and other relevant databases for cohort studies andrandomized controlled trials that reported postoperative complications (i.e.,respiratory, cardiovascular, wound-healing) and mortality in patients who quitsmoking within six months of surgery. Using a random effects model,meta-analyses were conducted to compare the relative risks of complications inex-smokers with varying intervals of smoking cessation vs the risks in currentsmokers.Principalfindings We included25 studies. Compared with current smokers, the risk of respiratorycomplications