We undertook this investigation to assess alterations in shear-mediated platelet function during cardiac surgery and to determine the potential for the PFA-100® to predict post-operative bleeding. Platelet aggregation and PFA-100® closure times were determined in 18 adult patients at five intervals during cardiac surgery. Associations between post-operative bleeding and closure times were examined in an additional 58 patients. Statistical analysis consisted of Student's t, Wilcoxon signed rank, and Spearman correlation tests. All results are reported as mean ± SEM. Collagen/epinephrine closure times were prolonged prior to and throughout surgery. Collagen/adenosine-5′-diphosphate (ADP) closure times were significantly prolonged by heparin administration, 141 ± 15 s versus 115 ± 10 s (P= 0.01), and subsequent initiation of cardiopulmonary bypass (CPB), 203 ± 12 s (P= 0.0001); however, 15 min after protamine administration, closure times returned to near pre-operative values, 138 ± 12 s (P= not significant). In contrast, platelet aggregation in response to ADP remained impaired in 17 of 19 patients after CPB. Neither ex vivo correction of sample hematocrits nor supplementation with Humate P1 affected closure times. Positive and negative predictive values for post-CPB collagen/ADP closure times to predict bleeding were 18 and 96%, respectively. These results suggest that factors both intrinsic and extrinsic to the platelet contribute to reversible shear-mediated platelet dysfunction during CPB, and that the PFA-100® may prove useful after CPB to identify patients unlikely to benefit from platelet transfusions.
Abstract —Cardiac G protein–coupled receptors that couple to Gα s and stimulate cAMP formation (eg, β-adrenergic, histamine, serotonin, and glucagon receptors) play a key role in cardiac inotropy. Recent studies in rodent cardiac myocytes and transfected cells have revealed that one of these receptors, the β 2 -adrenergic receptor (AR), also couples to the inhibitory G protein Gα i (activation of which inhibits cAMP formation). If β 2 ARs could be shown to couple to Gα i in the human heart, it would have important ramifications, because levels of Gα i increase with age and in failing human heart. Therefore, we investigated whether β 2 ARs in the human heart activate Gα i . By photoaffinity labeling human atrial membranes with [ 32 P]azidoanilido-GTP, followed by immunoprecipitation with antibodies specific for Gα i , we found that Gα i is activated by stimulation of β 2 ARs but not of β 1 ARs. In addition, we found that other Gα s -coupled receptors also couple to Gα i , including histamine, serotonin, and glucagon. When coupling of these receptors to Gα i is disrupted by pertussis toxin, their ability to stimulate adenylyl cyclase is enhanced. These data provide the first evidence that β 2 AR and many other Gα s -coupled receptors in human atrium also couple to Gα i and that abolishing the coupling of these receptors to Gα i increases the receptor-mediated adenylyl cyclase activity.
We report the anaesthetic management of a child with Prader–Willi syndrome and mitochondrial myopathy for open heart surgery. We used ketamine, fentanyl, rocuronium and caudal morphine together with a propofol infusion with no untoward effects. The implications of both conditions for anaesthesia are discussed.
Background Platelet ( PLT ) and plasma transfusion remain the mainstay hemostatic therapy for perioperative bleeding. Several studies have indicated that acquired fibrinogen ( FIB ) deficiency can be the primary cause of bleeding after cardiac surgery. The aim of this study was to compare hematologic and transfusion profiles between the first‐line FIB replacement and PLT transfusion in post–cardiac surgical bleeding. Study Design and Methods In this prospective, randomized, open‐label study, 20 adult patients who underwent valve replacement or repair and fulfilled preset visual bleeding scale were randomized to 4 g of FIB or 1 unit of apheresis PLTs . Primary endpoints included hemostatic condition in the surgical field and 24‐hour hemostatic product usage. Hematologic data, clinical outcome, and safety data were collected up to the 28th day postoperative visit. Results In patients who received the first‐line FIB concentrate (n = 10), the visual bleeding scale improved after intervention, and the incidence of PLT transfusion and total plasma donor exposure were lower compared to the PLT group (n = 10). Postintervention FIB level was statistically higher (209 mg/ dL vs. 165 mg/ dL ) in the FIB group than in the PLT group, but PLT count and prothrombin were lower. There were no statistical differences in the postoperative blood loss and red blood cell transfusion between two groups. Conclusions Our preliminary data indicate that the primary FIB replacement may potentially reduce the incidence of PLT transfusion and the number of donor exposures. Plasma FIB level of 200 mg/ dL is attainable with a single dose of 4 g, and this level seems to mitigate bleeding despite moderately decreased thrombin generation.
