Prophylactic treatment with desmopressin does not reduce postoperative bleeding after coronary surgery in patients treated with aspirin before surgery

The synthetic vasopressin analog desmopressin has hemostatic properties and may reduce postoperative bleeding after coronary artery bypass grafting (CABG). A study on the effects of recent aspirin ingestion on platelet function in cardiac surgery showed a greater impairment of platelet function in patients treated with aspirin <2 days before the operation. We evaluated the effects of desmopressin on postoperative bleeding in CABG patients who were treated with aspirin 75 or 160 mg until the day before surgery. The study was a prospective, randomized, double-blinded, placebo-controlled, parallel group trial. One-hundred patients were included and divided into two groups. One group received desmopressin 0.3 micro g/kg and the other received placebo (0.9% NaCl) after the neutralization of heparin with protamine sulfate. Postoperative blood loss was recorded for 16 h. The mean (SD) bleeding was 606 (237) mL in the desmopressin group and 601 (301) mL in the placebo group (P = 0.93), representing no significant difference (95% confidence interval, -107 to 117 mL). We conclude that desmopressin does not reduce postoperative bleeding in CABG patients treated with aspirin until the day before surgery. IMPLICATIONS: Continuation of aspirin until the day before coronary artery bypass grafting may increase postoperative bleeding. The administration of desmopressin to these patients after the neutralization of heparin with protamine sulfate does not reduce postoperative bleeding.     

No association between high-altitude tolerance and the ACE I/D gene polymorphism

PURPOSE: The absence (deletion allele [D]) of a 287 base-pair fragment in the ACE gene is associated with higher ACE tissue activity than its presence (insertion allele [I]) and, as such, may enhance vasoconstriction and fluid retention through increased levels of angiotensin II and aldosterone. Because fluid retention is found in acute mountain sickness (AMS) and exaggerated pulmonary hypertension is essential in the pathophysiology of high-altitude pulmonary edema (HAPE), we hypothesized that the DD genotype is associated with increased susceptibility to these illnesses. METHODS: ACE genotype was thus determined in 83 mountaineers staying over night at 4559 m and related to AMS symptoms. Genotype was similarly determined in 76 mountaineers who had participated in previous studies at 4559 m; 38 of the latter group had a history of HAPE, and 25 had developed HAPE again during these studies. RESULTS: The allele frequency was in Hardy-Weinberg equilibrium in both investigations. Neither the history nor the observed episodes of HAPE nor the prevalence of AMS defined as an AMS-C score >/= 0.70 (environmental symptom questionnaire) in the first study or in both studies taken together were significantly different between the genotypes DD, ID, and II. CONCLUSION: We conclude that I/D-ACE gene polymorphism has no important effect on susceptibility to AMS or HAPE.     

Motor imagery of hand actions: Decoding the content of motor imagery from brain activity in frontal and parietal motor areas

How motor maps are organized while imagining actions is an intensely debated issue. It is particularly unclear whether motor imagery relies on action‐specific representations in premotor and posterior parietal cortices. This study tackled this issue by attempting to decode the content of motor imagery from spatial patterns of Blood Oxygen Level Dependent (BOLD) signals recorded in the frontoparietal motor imagery network. During fMRI‐scanning, 20 right‐handed volunteers worked on three experimental conditions and one baseline condition. In the experimental conditions, they had to imagine three different types of right‐hand actions: an aiming movement, an extension–flexion movement, and a squeezing movement. The identity of imagined actions was decoded from the spatial patterns of BOLD signals they evoked in premotor and posterior parietal cortices using multivoxel pattern analysis. Results showed that the content of motor imagery (i.e., the action type) could be decoded significantly above chance level from the spatial patterns of BOLD signals in both frontal (PMC, M1) and parietal areas (SPL, IPL, IPS). An exploratory searchlight analysis revealed significant clusters motor‐ and motor‐associated cortices, as well as in visual cortices. Hence, the data provide evidence that patterns of activity within premotor and posterior parietal cortex vary systematically with the specific type of hand action being imagined. Hum Brain Mapp 37:81–93, 2016. © 2015 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.     

The effects of isoflurane-induced electroencephalographic burst suppression on cerebral blood flow velocity and cerebral oxygen extraction during cardiopulmonary bypass

We investigated the effects of isoflurane-induced burst suppression, monitored with electroencephalography (EEG), on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and autoregulation in 16 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopulmonary bypass (CPB) with mild hypothermia (32 degrees C) in fentanyl-anesthestized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular vein bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Autoregulation was tested during changes in mean arterial blood pressure (MAP) within a range of 40-80 mm Hg, induced by sodium nitroprusside and phenylephrine before (control) and during additional isoflurane administration to an EEG burst-suppression level of 6-9/min. Isoflurane induced a 27% decrease in CBFV (P < 0.05) and a 13% decrease in COE (P < 0.05) compared with control. The slope of the positive relationship between CBFV and cerebral perfusion pressure (CPP = MAP - JVP) was steeper with isoflurane (P < 0.05) compared with control, as was the slope of the negative relationship between CPP and COE (P < 0.05). We conclude that burst-suppression doses of isoflurane decrease CBFV and impair autoregulation of cerebral blood flow during mildly hypothermic CPB. Furthermore, during isoflurane administration, blood flow was in excess relative to oxygen demand, indicating a loss of metabolic autoregulation of flow. IMPLICATIONS: The effects of isoflurane on cerebral blood flow velocity (CBFV) and oxygen extraction (COE) as a function of perfusion pressure were studied. When added to fentanyl anesthesia, isoflurane induced a 27% and 13% decrease in CBFV and COE, respectively. CBFV became more pressure-dependent with isoflurane indicating an impaired autoregulation.     

An external fixation method and device to study fracture healing in rats

We wished to establish a reproducible model for fracture fixation to be used in fracture healing research and therefore developed an external fixation construct and surgical procedure adapted to Sprague-Dawley rats. We evaluated the mechanical properties of the construct in brass rods and rat bone, in an Instron test machine with axial and transverse loading, and the in vivo performance. We found that the mechanical properties of the construct in brass rods were predictable and could be repeated in rat femora. In all tests, the axial load was about 10 times the transverse for the same degree of deformation. The stiffness among fixators was uniform. 1 mm pins caused about 50% less stiffness than 1.2 mm pins in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) as well as in transverse loading of brass rods (p < 0.001). Loosening of 1 or 2 screws that lock the pins to the fixator reduced stiffness by about 50% in axial loading of rat bone (p = 0.009) and brass rods (p = 0.05). A change in the distance between the bone surface and the fixator was linearly related to the stiffness in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) and in transverse loading of brass rods (p < 0.001). If the bone ends touched each other, the axial stiffness of the construct increased almost 10 times (265 N/mm), as compared to a fracture gap size of 2 mm (31 N/mm). In vivo experiments had a complication rate of less than 10% when we used 1.2 mm pins, 6 mm offset and rats weighing 350-450 g. Our method and device for experimental external fixation of rat femora are reliable and the findings are reproducible. These can be used in bone repair and fracture healing research.     

Systemic and cavernous plasma levels of vasopressin in healthy males during different functional conditions of the penis

The role of the sympathetic adrenergic system in mediating the constant tone of penile flaccidity and returning the erect penis to its flaccid state is fairly well established. However, it is not yet known whether additional nonadrenergic-noncholinergic transmitters are involved in this process. Arginine-vasopressin (AVP, ADH), a pituitary peptide hormone with potent vasoconstrictor activity, may be one of the factors contributing to such control. The present study was undertaken to determine whether or not plasma levels of AVP change during penile flaccidity, tumescence, rigidity, and detumescence. We determined the plasma levels of AVP in the systemic as well as the cavernous blood of 25 healthy adult male volunteers who were exposed to visual and tactile erotic stimuli in order to elicit penile tumescence and erection. Whole blood was aspirated from the corpus cavernosum and the cubital vein, and AVP was quantified in plasma aliquots obtained from the whole blood samples. A marked decline in mean AVP plasma levels from 5.4+/-2.7 ng/l during flaccidity to 2.9+/-2.5 ng/l during rigidity was registered in the systemic blood of the subjects. No further decline was observed when the rigid penis became detumescent. In contrast, no alterations in AVP plasma levels were detected in the cavernous blood under the different penile conditions. The results from our study are contrary to the hypothesis of a local release and uptake of AVP in the cavernous compartment in the control of penile flaccidity and detumescence. Moreover, our findings are not in favour of AVP as an important mediator involved in adrenergic neurotransmission in the corpus cavernosum penis. Nevertheless, our data indicate that the decrease in systemic AVP levels in response to sexual arousal might be a prerequisite to facilitate penile tumescence and rigidity in healthy males.     

Single-dose tranexamic acid reduces postoperative bleeding after coronary surgery in patients treated with aspirin until surgery

Tranexamic acid reduces postoperative bleeding after coronary artery bypass grafting. We evaluated the effects of a single dose of tranexamic acid given immediately before cardiopulmonary bypass (CPB) in patients treated with aspirin until the day before surgery. The study was a prospective, randomized, double-blinded, placebo-controlled, parallel-group trial. Eighty patients were included and divided into two groups: one group received tranexamic acid 30 mg/kg, and one group received placebo (0.9% NaCl) as a bolus injection before CPB. Postoperative blood loss was recorded for 16 h. Transfusions of blood products were recorded for the whole hospital stay. Transfusions of packed red cells were given when the hematocrit value was less than 20% during CPB and less than 25% after surgery. The patients in the tranexamic acid group had significantly less postoperative bleeding compared with the patients in the placebo group (mean [SD]) (475 [274] mL versus 713 [243] mL; P < 0.001). An effective inhibition of fibrinolysis was found in patients receiving tranexamic acid. Tranexamic acid reduces postoperative bleeding in coronary artery bypass grafting patients treated with aspirin until the day before surgery. IMPLICATIONS: Continuation of aspirin medication until the day before coronary artery bypass grafting may increase postoperative bleeding. The administration of a single dose of tranexamic acid (30 mg/kg) immediately before cardiopulmonary bypass significantly reduced postoperative bleeding and inhibited fibrinolysis in these patients.     

Intra-aneurysm pressure measurements in successfully excluded abdominal aortic aneurysm after endovascular repair

PURPOSE: This study was performed to determine intra-aneurysm sac pressure of abdominal aortic aneurysm after endovascular aneurysm repair in patients considered successfully treated with aneurysm shrinkage and absence of endovascular leakage. METHODS: In 10 patients with median aneurysm shrinkage of 12 mm (range, 7 to 22 mm) and median follow-up of 19 months (range, 14-43 months), a percutaneous translumbar intra-aneurysm pressure measurement was made with a 0.014-inch guide wire-mounted pressure sensor and compared with intra-aortic pressure. RESULTS: Median intra-aneurysm systolic/diastolic/mean pressure was 19/18/19 (range, 17-35/13-33/17-31) compared with median intra-aortic pressure of 135/75/99 (range, 126-199/60-95/84-129). Mean intra-aneurysm pressure was 20% of mean intra-aortic pressure (range, 13%-33%). Pulsatility was negligible. CONCLUSION: Successful endovascular aneurysm repair of abdominal aortic aneurysm results in considerable pressure reduction in the aneurysm sac. The ability to monitor intra-aneurysm pressure provides hemodynamic information within the sac, which can be used in conjunction with imaging to determine whether a secondary intervention is warranted.