Coagulation Day 2010: an Austrian survey on the routine of thromboprophylaxis in intensive care

PURPOSE

Venous thromboembolism (VTE) is a common but often overlooked life-threatening complication of critical illness. The aim of this cross-sectional survey was to assess current practice of thromboprophylaxis as well as adherence to international guidelines.

METHODS

After ethics committee approval, all intensive care units in Austrian hospitals treating adult patients were invited to participate in this web-based survey. Anonymized data on each patient treated at the participating intensive care units on Coagulation Day 2010 were collected using an electronic case report form. Risk assessment, choice and monitoring of anticoagulants, means of mechanical prophylaxis, and demographic data were recorded.

RESULTS

Data from 325 critically ill patients were collected. Patients had a median of four risk factors for thrombosis and 6 % suffered from VTE. Of the 325 patients, 80 % received low molecular weight heparins subcutaneously, 10 % received unfractionated heparin intravenously, 1 % received alternative anticoagulants and 9 % received no pharmacological prophylaxis. Mechanical prophylaxis was used in 49 % with a predominant use of graduated compression stockings. In 39 % a combination of pharmacological and mechanical prophylaxis was applied and 5 % received no prophylaxis at all. Overall guideline adherence was 40 % on Coagulation Day 2010.

CONCLUSION

Current practice of thromboprophylaxis is predominantly based on the administration of low molecular weight heparins prescribed at rather arbitrary doses without a discernible relationship to drug monitoring, thromboembolic risk factors, vasopressor use or fluid balance. The use of mechanical prophylaxis, evaluation of risk scores and overall guideline adherence must be further encouraged by education, training and communication.

[Preoperative evaluation of the bleeding history. Recommendations of the working group on perioperative coagulation of the Austrian Society for Anaesthesia, Resuscitation and Intensive Care]

Unexpected bleeding in the perioperative period is largely caused by impaired inherited or drug-induced primary haemostasis. Standard tests for plasma coagulation are predominantly employed to gauge the risk of bleeding. In accordance with several reports the subcommittee for perioperative coagulation (AGPG) of the Austrian Society of Anaesthesia, Resuscitation and Intensive Care (OGARI) recommends the use of a standardised questionnaire to detect an increased risk of bleeding. Accordingly, healthy patients of the American Society of Anesthesiologists (ASA) grades I and II without any suspicion of impaired haemostasis who are scheduled for procedures without expected transfusion requirements, need no standard tests for coagulation. In all other patients (including patients taking medication affecting coagulation, or patients who are unable to provide adequate information) platelet count, platelet function, aPTT, PT, and fibrinogen levels should be assessed.

Lokoregionalanästhesien unter gerinnungshemmender Medikation

More efficacious anticoagulant and antiplatelet agents have been introduced in vascular medicine and in the prevention of perioperative venous thromboembolisms. Patient management should be guided by familiarity with the pharmacology of coagulation-altering drugs and by consensus statements. The present paper reviews recommendations from the Austrian Task Force for Perioperative Coagulation which are based on thorough evaluation of the available pharmacological information and case reports. The consensus statement focuses on neuraxial and peripheral techniques and is designed to encourage safe and quality patient care.

Effects of heparin and aspirin on circulating P-selectin, E-selectin and von Willebrand Factor levels in healthy men

As thrombin stimulates P-selectin expression on platelets and its release into plasma, we hypothesized that enhancing antithrombin activity by unfractionated heparin (UFH) could decrease plasma levels of circulating (c)P-selectin, (c)E-selectin, and von Willebrand Factor (vWF). Hence the effect of UFH and aspirin were examined on these activation markers in healthy volunteers. UFH decreased cP-selectin levels by -10% (CI: -16 - (-4%); P = 0.005) at 24 h, but did not change levels of vWF-Ag. In contrast, aspirin did not affect cP-selectin levels but decreased vWF-Ag levels by -12% (CI: -18 - (-7%); P = 0.005) at 24 h. Neither drug affected cE-selectin levels. Thus, UFH decreases cP-selectin levels, which may reflect decreased platelet activation in vivo. An increase in cP-selectin under UFH therapy should alert the clinician to look for platelet destruction.

Pharmacokinetics of emedastine difumarate, a new anti-histaminic agent in patients with renal impairment

OBJECTIVE

Emedastine difumarate is a new H1 receptor antagonist with well defined pharmacokinetic and pharmacodynamic profiles in healthy volunteers. However, to date it is not known whether impaired renal function in patients with chronic renal insufficiency affects its pharmacokinetics and probably also its tolerability. Therefore, we here set out to compare the pharmacokinetics of emedastine difumarate in patients suffering from different degrees of renal failure with a control group of healthy volunteers.

METHODS AND RESULTS

For this purpose we conducted an open, single-centre, comparative parallel group study in patients and healthy volunteers. Emedastine difumarate 2 mg was administered orally to the study population in single and seven repetitive doses twice daily (b.i.d.). Pharmacokinetics differed markedly between volunteers (n = 6) and patients (n = 17). The maximum serum concentration of emedastine (Cmax), area under the serum concentration-time curve, mean residence time and terminal disposition half-life were significantly higher in patients (P < 0.05), while time to reach Cmax and apparent volume of disposition were not statistically different after single and repeated (steady-state) oral administrations. Blood pressure and heart rate were also not affected by the study medication.

CONCLUSION

The present study shows that impaired renal function alters the pharmacokinetics of emedastine in plasma. Thus, dose adjustment of emedastine difumarate is advisable in patients with impaired renal function.

Effects of anticoagulation on thrombopoietin release during endotoxemia

Several lines of evidence suggest that coagulation may induce the release of thrombopoietin (TPO) into plasma and that TPO levels are higher in disseminated intravascular coagulation. Therefore we set out to illuminate the mechanism of TPO release in the setting of experimental endotoxemia, which induces activation of coagulation and platelets. Endotoxin (lipopolysachharide [LPS], 2 ng/kg) was infused into a total of 54 healthy men in two subsequent studies. Volunteers received infusions of unfractionated heparin, low-molecular-weight heparin, lepirudin, or placebo in a randomized, placebo-controlled fashion after bolus injection of LPS. TPO levels increased on average by 27% to 38% in all groups at 6 hours (P <.05 vs baseline), although all active drugs effectively blocked coagulation. Platelet counts dropped by about 15% at 1 hour after LPS infusion, recovered after 2 days, and exceeded baseline values by 8% to 18% after 7 days (P <.001 vs baseline for all groups). Yet lepirudin blunted the LPS-induced increase in circulating P-selectin by one half (P <.005 vs placebo), whereas both heparins did not diminish the increase in this platelet or endothelial activation marker as compared with placebo. Endotoxemia enhances TPO plasma levels independent of the degree of coagulation induction, which eventually results in increased platelet numbers. Of potential clinical interest is the observation that the direct thrombin inhibitor lepirudin, in contrast to heparins, mitigated LPS-induced platelet activation.

Systemic inflammation increases shear stress-induced platelet plug formation measured by the PFA-100

The PFA-100 measures platelet plug formation under shear stress and is strongly dependent on von Willebrand Factor (VWF) levels in plasma. We therefore hypothesized that elevated VWF levels, possibly as a result of acute inflammation, adversely influence PFA-100 results. Healthy volunteers received either 2 ng/kg endotoxin or placebo in a randomized controlled trial. Four hours after endotoxin (but not placebo) infusion VWF levels increased by 85%, collagen epinephrine-induced closure time (CT) decreased by 47% and collagen ADP-CT decreased by 38% (P < 0.0001) respectively. In conclusion, systemic inflammation has a major impact on the results obtained by PFA-100 and may confound interpretation of platelet function.

Surgery and intensive care procedures affect the target site distribution of piperacillin

OBJECTIVE

Therapeutic failure of antibiotic therapy has been ascribed to pharmacokinetic alterations in compromised patient populations. The present study, therefore, aimed at examining the influences of cardiac surgery and intensive care procedures on the postoperative target site distribution of piperacillin. For this purpose, the penetration of piperacillin to the interstitial space fluid, the relevant target site for most bacterial infections, was compared between patients after aortic valve replacement and healthy volunteers.

DESIGN

Comparative study in two study populations.

SETTING

The intensive care unit and research ward of a university hospital.

PATIENTS

The study population included six otherwise healthy patients scheduled to undergo aortic valve replacement and a control group of six healthy male volunteers.

INTERVENTIONS

After the administration of a single i.v. infusion of 4.0 g piperacillin, free piperacillin concentrations were measured in the interstitium of skeletal muscle and subcutaneous tissue by in vivo microdialysis and in venous serum. Piperacillin concentrations were assayed with reversed phase high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

Interstitial piperacillin concentrations in muscle and subcutaneous adipose tissue were significantly lower in patients compared with volunteers with the area under the curve for the interstitium/area under the curve for serum concentration ratios ranging from 0.25 to 0.27 and from 0.43 to 1.22 in patients and volunteers, respectively (p < .05 between groups). The terminal elimination half-life was markedly prolonged in patients, leading to a concomitant increase in t > minimal inhibitory concentration (MIC) values, the relevant surrogate for therapeutic success of therapy with beta-lactam antibiotics, for strains with MIC50 <4 microg/mL. For strains with MIC50 >20 microl/mL, however, inadequate target site concentrations were attained in the patient population.

CONCLUSIONS

During the postoperative and intensive care periods, target site concentrations of piperacillin are markedly altered and decreased. This may also be true for other antibiotic agents and may have clinical implications in that current dosing guidelines may result in inadequate target site concentrations for high-MIC strains. Conceivably, this could lead to therapeutic failure in some patients.

Inhaled nitric oxide reduces pulmonary vascular resistance more than prostaglandin E(1) during heart transplantation

Heart transplantation in patients with increased pulmonary vascular resistance is often associated with postbypass right heart failure. We therefore compared the abilities of prostaglandin E(1) (PGE(1)) and inhaled nitric oxide to reduce pulmonary vascular resistance during heart transplantation. Patients undergoing orthotopic heart transplantation for congestive heart failure were randomly assigned to either a PGE(1) infusion at a rate of 8 ng. kg. (-1)min(-1) starting 10 min before weaning from cardiopulmonary bypass (CPB) (n = 34) or inhalation of 4 ppm nitric oxide starting just before weaning from CPB (n = 34). Both treatments were increased stepwise, if necessary, and were stopped 6 h postoperatively. Hemodynamic values were recorded after the induction of anesthesia, 10 and 30 min after weaning from CPB, and 1 h and 6 h postoperatively. Immediately after weaning from CPB, pulmonary vascular resistance was nearly halved in the nitric oxide group but reduced by only 10% in the PGE(1) group. Pulmonary artery pressure was decreased approximately 30% during nitric oxide inhalation, but only approximately 16% during the PGE(1) infusion. Six hours after surgery, pulmonary vascular resistance and pulmonary artery pressure were similar in the two groups. The ratio between pulmonary vascular resistance and systemic vascular resistance was significantly less in the nitric oxide patients at all postbypass times. In contrast, the pulmonary-to-systemic vascular resistance ratio increased approximately 30% in the patients given PGE(1). Cardiac output, heart rate, mean arterial pressure, right atrial pressure, and pulmonary wedge pressure did not differ between the groups. Weaning from CPB was successful in all patients assigned to nitric oxide inhalation; in contrast, weaning failed in six patients assigned to PGE(1) (P = 0.03).

IMPLICATIONS

Nitric oxide inhalation selectively reduces pulmonary vascular resistance and pulmonary artery pressure immediately after heart transplantation which facilitates weaning from cardiopulmonary bypass.

Lepirudin blunts endotoxin-induced coagulation activation

During sepsis, lipopolysaccharide (LPS) triggers the development of disseminated intravascular coagulation (DIC) via the tissue factor-dependent pathway of coagulation resulting in massive thrombin generation and fibrin polymerization. Recently, animal studies demonstrated that hirudin reduced fibrin deposition in liver and kidney and decreased mortality in LPS-induced DIC. Accordingly, the effects of recombinant hirudin (lepirudin) was compared with those caused by placebo on LPS-induced coagulation in humans. Twenty-four healthy male subjects participated in this randomized, double-blind, placebo-controlled, parallel group study. Volunteers received 2 ng/kg LPS intravenously, followed by a bolus-primed continuous infusion of placebo or lepirudin (Refludan, bolus: 0.1 mg/kg, infusion: 0.1 mg/kg/h for 5 hours) to achieve a 2-fold prolongation of the activated partial thromboplastin time (aPTT). LPS infusion enhanced thrombin activity as evidenced by a 20-fold increase of thrombin-antithrombin complexes (TAT), a 6-fold increase of polymerized soluble fibrin, termed thrombus precursor protein (TpP), and a 4-fold increase in D-dimer. In the lepirudin group, TAT increased only 5-fold, TpP increased by only 50%, and D-dimer only slightly exceeded baseline values (P <.01 versus placebo). Concomitantly, lepirudin also blunted thrombin generation evidenced by an attenuated rise in prothrombin fragment levels (F(1 + 2), P <. 01 versus placebo) and blunted the expression of tissue factor on circulating monocytes. This experimental model proved the anticoagulatory potency of lepirudin in LPS-induced coagulation activation. Results from this trial provide a rationale for a randomized clinical trial on the efficacy of lepirudin in DIC. (Blood. 2000;95:1729-1734)

Partial inhibition of nitric oxide synthase primes the stimulated pathway of vWF-secretion in man

Increased release of von Willebrand factor (vWF) has been linked to the pathogenesis of atherosclerosis. For this complex disease, impairment of endothelium-derived, nitric oxide production and impaired vascular relaxation has also been reported. Since endothelially produced nitric oxide (NO) is known to inhibit secretion of the Weibel-Palade bodies in animals, we hypothesized that NO could mitigate vWF secretion. In a randomized, placebo controlled cross-over trial, eight male volunteers received N-monomethyl-L-arginine (LNMMA) to block endothelial NO production or placebo, and vWF release was stimulated by infusing desmopressin in three cumulative doses (0.05, 0.15, 0.4 microg/kg) in both periods. At a threshold dose of 0.l5 microg/kg desmopressin, concomitant partial blockade of NO production resulted in 20% higher levels of vWF (P<0.04). However, maximal vWF release after 0.4 microg/kg desmopressin was unaffected by L-NMMA (Delta7% between periods, P=0.88). These data show the dampening effect of NO production on vWF release in response to threshold concentrations of secretagogues. This may in part explain the higher vWF levels in cardiovascular diseases associated with impaired endothelial NO generation.

Heparin blunts endotoxin-induced coagulation activation

BACKGROUND

Lipopolysaccharide (LPS) is a major trigger of sepsis-induced disseminated intravascular coagulation (DIC) via the tissue factor (TF)/factor VIIa-dependent pathway of coagulation. Experimental endotoxemia has been used repeatedly to explore this complex pathophysiology, but little is known about the effects of clinically used anticoagulants in this setting. Therefore, we compared with placebo the effects of unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) on LPS-induced coagulation.

METHODS AND RESULTS

In a randomized, double-blind, placebo-controlled trial, 30 healthy male volunteers received LPS 2 ng/kg IV followed by a bolus-primed continuous infusion of UFH, LMWH, or placebo. In the placebo group, activation of coagulation caused marked increases in plasma levels of prothrombin fragment F(1+2) (P<0.01) and polymerized soluble fibrin, termed thrombus precursor protein (TpP; P<0.01); TF-positive monocytes doubled in response to LPS, whereas levels of activated factor VII slightly decreased and levels of TF pathway inhibitor remained unchanged. UFH and LMWH markedly decreased activation of coagulation caused by LPS, as F(1+2) and TpP levels only slightly increased; TF expression on monocytes was also markedly reduced by UFH. TF pathway inhibitor values increased after either heparin infusion (P<0.01). Concomitantly, factor VIIa levels dropped by >50% at 50 minutes after initiation of either heparin infusion (P<0.01).

CONCLUSIONS

This experimental model proved the anticoagulatory potency of UFH and LMWH in the initial phase of experimental LPS-induced coagulation. Successful inhibition of thrombin generation also translates into blunted activation of coagulation factors upstream and downstream of thrombin.

Systemic blood pressure and cerebral blood flow velocity during carotid surgery

BACKGROUND

To evaluate the effect of mean arterial blood pressure (MAP) on cerebral perfusion during carotid surgery, we investigated blood flow velocity in the middle cerebral (Vs,mca) using transcranial Doppler ultrasonography (TCD).

METHODS

During carotid crossclamping, treatment included either phenylephrine-induced hypertension without shunting (Group XC; n = 11) or insertion of a shunt (Group S; n = 12).

RESULTS

Increasing MAP in Group XC before crossclamping (81 + /-13 mmHg to 107 +/- 12 mmHg) caused an increase of Vs,mca (59 +/- 17 cm/s to 75 +/- 20 cm/s; p < 0.001). During crossclamping without a shunt, Vs,mca was not dependent on MAP, and was reduced (mean 47 +/- 24 cm/s) in relation to preclamp values. In Group S, Vs,mca was always dependent on MAP and the preclamp velocity was maintained (before shunt: 75 +/- 26 cm/sec; during shunt: 79 +/- 30 cm/sec).

CONCLUSIONS

Although we found an impaired cerebral autoregulation, Vs,mca was independent of MAP during carotid crossclamping. Thus, TCD measurements have to be interpreted with caution during crossclamping, and the effect of induced hypertension has to be confirmed with more invasive measures of cerebral blood flow.

Endotoxin-induced activation of the coagulation cascade in humans: effect of acetylsalicylic acid and acetaminophen

During Gram-negative septic shock, lipopolysaccharide (LPS, endotoxin) induces tissue factor (TF) expression. TF expression is mediated by nuclear factor kappaB and amplified by activated platelets. TF forms a highly procoagulant complex with activated coagulation factor VII (FVIIa). Hence, we hypothesized that aspirin, which inhibits LPS-induced, nuclear factor kappaB-dependent TF expression in vitro and platelet activation in vivo, may suppress LPS-induced coagulation in humans. Therefore, we studied the effects of aspirin on systemic coagulation activation in the established and controlled setting of the human LPS model. Thirty healthy volunteers were challenged with LPS (4 ng/kg IV) after intake of either placebo or aspirin (1000 mg). Acetaminophen (1000 mg) was given to a third group to control for potential effects of antipyresis. Neither aspirin nor acetaminophen inhibited LPS-induced coagulation. However, LPS increased the percentage of circulating TF(+) monocytes by 2-fold. This increase was associated with a decrease in FVIIa levels, which reached a minimum of 50% 24 hours after LPS infusion. Furthermore, LPS-induced thrombin generation increased plasma levels of circulating polymerized, but not cross-linked, fibrin (ie, thrombus precursor protein), whereas levels of soluble fibrin were unaffected. In summary, a single 1000-mg dose of aspirin did not decrease LPS-induced coagulation. However, our study showed, for the first time, that LPS increases TF(+) monocytes, substantially decreases FVIIa levels, and enhances plasma levels of thrombus precursor protein, which may be a useful marker of fibrin formation in humans.

[Difference between gastric mucosal pCO2 and arterio-intramucosal pCO2 during orthotopic liver transplantation]

Tonometry is a clinically accepted method to monitor blood flow of the splanchnic region, which is of particular interest in orthotopic liver transplantation (OLT). We investigated the hemodynamic changes and the tonometrically registered perioperative course of the difference between gastric mucosal pCO2 (prCO2) and arterial mucosal CO2 (CO2 gap) in 23 patients undergoing OLT without veno-venous bypass. Gastric mucosal pH (pHi) was additionally calculated. Despite significant changes in systemic hemodynamics during the anhepatic stage and after reperfusion and a significant drop in pHi during anhepacy, the difference between prCO2 and CO2 was constant. These contrasting findings of tonometry, i.e. solely a drop in pHi is, in our opinion, a consequence of the poor metabolic capacity of the liver in the perioperative OLT period, which influenced the calculation of the pHi with the Henderson-Hasselbalch equation. We conclude that, due to methodical problems, calculated pHi is not a reliable indicator of splanchnic blood flow and oxygenation during OLT. We therefore suggest that the prCO2 and the CO2 gap be used to monitor the splanchnic region. These parameters, obtained perioperatively, do not indicate a further reduction in splanchnic oxygenation despite profound changes in systemic hemodynamics during OLT without veno-venous bypass.

Acetaminophen has greater antipyretic efficacy than aspirin in endotoxemia: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To compare the antipyretic efficacy of aspirin and acetaminophen (INN, paracetamol) in 30 male volunteers with the use of endotoxin (lipopolysaccharide) to elicit a standardized febrile response.

METHODS

A randomized, double-blind, placebo-controlled trial was conducted in parallel groups. Subjects received an intravenous endotoxin bolus of 4 ng/kg after premedication with either placebo, 1000 mg aspirin, or 1000 mg acetaminophen by mouth.

RESULTS

Peak body temperatures were 38.5 degrees C +/- 0.2 degrees C in the placebo group, 37.6 degrees C +/- 0.2 degrees C in the acetaminophen group (P = .001 versus placebo), and 38.6 degrees C +/- 0.2 degrees C in the subjects treated with aspirin (P = .001 versus acetaminophen; P = .570 versus placebo) at 4 hours after lipopolysaccharide infusion. Subjective symptom scores for chills and perception of fever were higher in the placebo group than in the acetaminophen group (chills, 2.5 +/- 0.3 versus 1.0 +/- 0.2, P = .009 and fever, 2.5 +/- 0.2 versus 2.0 +/- 0.2, P = .021). Tumor necrosis factor-alpha, interleukin-6, and interleukin-8 levels rose by several orders of magnitude (P < .001 versus baseline in all groups), without significant intergroup differences.

CONCLUSIONS

Acetaminophen was the superior antipyretic drug in endotoxemia compared with aspirin. Treatment with acetaminophen ameliorates subjective symptoms induced by endotoxemia without compromising the humoral response of a subject to endotoxin. This observation has clinical interest and may also help to improve the lipopolysaccharide model, which can be used to test anti-inflammatory and anticoagulatory drugs.

Heparin lowers plasma levels of activated factor VII

Based on heparin's antithrombin and anti-FXa activity and its in vitro inhibition of activated factor VII (FVIIa) activity, we hypothesized that unfractionated heparin (UFH) may decrease plasma levels of FVIIa in humans. Therefore, 10 healthy young male volunteers received an intravenous UFH infusion over 24 h. Heparin decreased FVIIa levels by 30% (95% CI 14-47%) at 12 h, which was sustained until 24 h. In contrast, neither the substrate pool (i.e. total factor VII) as measured by FVII antigen nor FVII activity were affected by UFH. These results may improve our understanding of the regulation of FVIIa levels and heparin's mode of action.

Local anaesthesia versus general anaesthesia for cardioverter-defibrillator implantation

AIMS

Cardioverter-defibrillators are conventionally implanted under general anaesthesia. However, implantation under conscious sedation is being increasingly used. It has been shown that cardioverter-defibrillators can be implanted in a more pacemaker-like approach: under local anaesthesia for the surgical procedure, and with mild sedation for defibrillation threshold testing only. The aim of the present study was to compare local and general anaesthesia in defibrillation threshold testing and implantation of cardioverter-defibrillators.

METHODS AND RESULTS

Forty patients were assigned to two groups: in the first 20 consecutive patients the cardioverter-defibrillator was implanted under general anaesthesia (GA), and in the subsequent 20 patients under local anaesthesia (LA). There was no significant difference between the two groups in regard of age, body weight, underlying disease, left ventricular ejection fraction, and NYHA classification. The defibrillation threshold was 13.7 +/- 5.5 J under local anaesthesia versus 10.7 +/- 4.7 J under general anaesthesia (n.s.). For defibrillation threshold testing 7.9 +/- 3.6 shocks had to be applied in patients under general anaesthesia versus 6.2 +/- 1.3 shocks under local anaesthesia (n.s.). Mean heart rate, arterial oxygen saturation and mean arterial blood pressure remained stable throughout defibrillation threshold testing, irrespective of the type of anaesthesia used. The duration of the surgical procedure was 62 +/- 16 min under GA and 60 +/- 14 min under LA (n.s.), however, the entire implantation procedure was significantly longer in patients under general anaesthesia than in those under local anaesthesia (124 +/- 24 min and 97 +/- 22 min, respectively, p < 0.005). There were no complications in either group and the procedure was well tolerated. With the use of local anaesthesia the cost of anaesthesia were reduced by 72%.

CONCLUSION

Local anaesthesia in combination with mild sedation is as safe and well tolerated as general anaesthesia in cardioverter-defibrillator implantation. Lidocaine used for local anaesthesia does not adversely affect the defibrillation threshold. Device implantation in a pacemaker-like approach results in a significant reduction in total procedure time and costs, and facilitates scheduling of the procedure.

Effects of nitric oxide on platelet activation during plateletpheresis and in vivo tracking of biotinylated platelets in humans

BACKGROUND

The use of platelet transfusions has risen considerably over the last few years, which leads to the collection and transfusion of a greater number of donor plateletpheresis units. Plateletpheresis activates platelets in platelet concentrates, which determines the degree of the storage lesion subsequently observed.

STUDY DESIGN AND METHODS

As nitric oxide (NO) is a potent inhibitor of platelet aggregation and activation, a placebo-controlled crossover trial was performed in healthy young male volunteers to determine whether the NO-donating compound, sodium nitroprusside (SNP), decreases platelet activation during apheresis and whether activated (p-selectin+) platelets circulate in vivo after transfusion. The study also investigated whether nonradioactive biotin labeling of apheresis platelets is feasible for the study of platelet recovery after transfusion in humans.

RESULTS

Platelet activation increased after plateletpheresis in the platelet components, but SNP did not inhibit platelet activation during apheresis, as measured by the percentage of p-selectin expression and the secretion of soluble p-selectin and RANTES. Only a minor increase in p-selectin+ platelets was seen in peripheral blood at 60 minutes after transfusion of the platelets, a rise that was considerably less than that calculated in p-selectin+ platelets if they all were recovered as activated platelets after transfusion. Biotin-labeled platelets averaged 1.5 percent at 10 minutes after transfusion and increased slowly to 2.6 and 3.4 percent after 60 minutes and 24 hours, respectively (p<0.05).

CONCLUSION

SNP does not decrease platelet activation during apheresis and subsequent storage, and only a minor proportion of activated (p-selectin+) platelets circulate after transfusion in men. Moreover, biotin labeling of PCs can safely be used in humans for the study of platelet recovery after transfusion, and measuring recovery at 1 hour may lead to an underestimation of the true recovery when activated platelets are transfused.

Splanchnic circulation is maintained during passive hyperventilation in orthotopic liver recipients

BACKGROUND

Mechanical hyperventilation is an established treatment to reduce brain edema and intracranial pressure in patients with encephalopathia caused by acute liver failure. Hyperventilation and ensuing hypocarbia may also affect central and systemic circulation and thereby influence graft performance in patients following orthotopic liver transplantation (OLT).

METHODS

We measured the effects of normocapnia and hypocapnia on systemic hemodynamics, gastric tonometry, as a marker of splanchnic oxygenation, and the indocyanine green kinetic, as a global marker of graft function, in humans post OLT.

RESULTS

Hyperventilation was performed to a PaCO2 of 4.2 +/- 0.4 kPa (31 +/- 3.4 mm Hg) for about 1 h in 14 liver transplant recipients. Systemic hemodynamics as well as indices of splanchnic oxygenation and indocyanine green kinetics remained statistically unchanged.

CONCLUSION

We did not observe any statistically significant circulatory effects or changes in indocyanine green kinetics in liver transplant recipients in the immediate OLT postoperative period caused by short-term mechanical hyperventilation.

Effects of endotoxemia on thrombopoiesis in men

BACKGROUND

Febrile conditions are often associated with increased platelet turnover and refractoriness to platelet transfusions, although several pyrogenic cytokines enhance thrombopoiesis. This study aimed to characterize the effects of experimental human endotoxemia on platelet turnover and thrombopoiesis.

METHODS

Endotoxin (4 ng/kg) was infused into 30 healthy men to study the regulation of thrombopoiesis in systemic human inflammation. Platelet counts, plasma thrombopoietin (TPO) and glycocalicin levels, and reticulated platelets (RP) were measured to evaluate the effect of acute endotoxemia on thrombopoiesis. Ten subjects received pretreatment with 1000 mg aspirin po. to evaluate possible effects of aspirin on platelet turnover, and ten subjects received paracetamol to control for effects of antipyresis.

RESULTS

Platelet counts dropped by about 15% (p <0.001) one hour after LPS infusion, began to recover at 24 h, and exceeded baseline values by 81% (CI: 5-12; p <0.001 ) at 7 days after LPS iv. Reticulated platelet counts increased from 1.62% (CI: 1.24-2.0) to a maximum of 2.39% (CI: 1.81-2.98; p = 0.003) at 6 h. TPO levels increased from baseline values of 10 A.U/ml (CI: 8.8-11.2) to 15.5 A.U/ml (CI: 13.6-17.3) at 24 h (p <0.001), whereas plasma glycocalicin was not changed (p >0.05). The number of circulating platelet-neutrophil aggregates increased more than 100% at 6 h (p <0.001). Neither aspirin nor paracetamol affected changes in any of the parameters measured.

CONCLUSION

Low grade endotoxemia induces a rapid fall of platelet counts, which is followed by an early increase in reticulated platelets and TPO levels but not of glycocalicin levels. Finally peripheral platelet counts increase several days after LPS infusion.

Regulation of adhesion molecules during human endotoxemia. No acute effects of aspirin

Gram-negative septic shock is mediated in part by endotoxin (lipopolysaccharide; LPS), and animal models have shown that blockade of even single adhesion molecules considerably improves survival. Thus interference with the adhesion cascade may provide a useful therapeutic approach in human sepsis. Young healthy men (n = 30) each received a bolus of 4 ng/kg LPS intravenously to study the effects of endotoxemia on adhesion processes in humans and to identify potential targets for pharmacologic intervention. One third of subjects received pretreatment with 1,000 mg aspirin and 1,000 mg paracetamol to study potential antiinflammatory effects of aspirin or effects of antipyresis. Circulating neutrophils dropped by -80% at 67 min after LPS, monocytes by -96% at 90 min, and lymphocytes by -85% at 240 min. L-selectin expression decreased, particularly on monocytes. Circulating (c)E-selectin levels increased by 820%, von Willebrand factor-Ag (vWF), soluble thrombomodulin, circulating (c)P-selectin, circulating intercellular adhesion molecule-1 (cICAM-1), and circulating vascular cell adhesion molecule-1 (cVCAM-1) by a mean of 65 to 98% (p < 0.001 for all), but cL-selectin by only 15%. Urinary excretion of soluble adhesion molecules was negligible. Aspirin had no influence on the LPS-induced changes of adhesion parameters, but paracetamol blunted the relative increase in vWF while having no effects on the other parameters measured. The consistent, profound, and early upregulation of cE-selectin during endotoxemia indicates that cE-selectin may be a better surrogate marker to monitor the activation status of endothelial cells in systemic inflammation than the other markers measured. Although aspirin did not have any antiinflammatory effects in this model, paracetamol lowered the relative increase in vWF.

Inhalation of nitric oxide as a life-saving therapy in a patient after pulmonary embolectomy

We describe a 54-yr-old man with cardiogenic shock caused by acute right heart failure after pulmonary embolectomy. Inhalation of nitric oxide led to immediate improvement in respiratory and haemodynamic variables. Inhaled nitric oxide can be used to reduce acute right heart failure until conventional therapy can provide successful haemodynamic stability.

Plasma levels of activated factor VII decrease during the menstrual cycle

Men have an increased cardiovascular risk as compared to women, which is largely ascribed to the cardioprotective effects of female sex steroids. We hypothesised that this may be reflected by differences in the activation status of the coagulation system. Hence the aim of this study was to compare plasma levels of activated factor VII (FVIIa) in men and women, and to study the influence of the menstrual cycle on FVIIa levels. In a prospective study we investigated 20 healthy young women and 20 men. Men had significantly higher levels of activated factor VII (60 mU/ml, CI: 52 to 67) than women during all phases of the menstrual cycle. In women FVIIa was higher during the follicular phase (41 mU/ml, CI: 33 to 50) than during midcycle (34 mU/ml, CI: 24 to 45; p = 0.022 vs. follicular phase) and during the luteal phase (33 mU/ml, CI: 24 to 42; p = 0.006 vs. follicular phase). Prothrombin fragment (F1 + 2) levels decreased from 0.86 nmol/l (CI: 0.51-1.21) by -23% (-39% to -8%; p = 0.011) during midcycle and by -25% (CI: -51% to 1%; p = 0.023) during the luteal phase. These data support the contention that plasma levels of FVIIa, a key enzyme of the coagulation cascade, may be down-regulated by endogenously produced female sex hormones during the menstrual cycle. This may at least partially explain the marked gender differences found in FVIIa.

Low-dose aspirin does not lower in vivo platelet activation in healthy smokers

Smoking causes atherosclerosis, and smokers have increased thromboxane (TXA2) formation. As aspirin inhibits TXA2 production we speculated that smokers would preferentially profit from inhibition of the TXA2 pathway by aspirin. Increased expression of P-selectin, a constituent of the alpha-granules of platelets, and increased levels of circulating (c)P-selectin in plasma are markers for platelet activation. The aim of this study was to compare P-selectin expression on platelets between smokers and nonsmokers, and to compare with placebo the effect of 2 weeks administration of 100 mg/d aspirin on platelet activation in smokers. Smokers exhibited higher P-selectin expression on platelets than non-smokers (2.7+/-1.8% v 1.6+/-0.6%, P=0.018), thus confirming increased platelet activation. Aspirin did not reduce platelet activation as demonstrated by unchanged P-selectin expression on platelets and cP-selectin plasma levels.

Effects of nitroglycerin and sodium nitroprusside on endexpiratory concentrations of nitric oxide in healthy humans

The cellular origin of nitric oxide (NO) in exhaled air of healthy humans is unknown. It is currently not known, whether changes in NO concentrations that originate from pulmonary vessels, can be detected as changes in exhaled NO. Thus, we have studied the effects of increased intravascular NO generation on endexpiratory NO-levels. Twenty-four young healthy volunteers received nitroglycerin (GTN), sodium nitroprusside (SNP) or placebo i.v. in a randomized, double blind cross-over trial. Diastolic blood pressure decreased from 59 mmHg (95% confidence interval: 56-62) during placebo to 48 mmHg (CI: 45-51) and to 48 mmHg (CI: 45-50) after infusions of GTN and SNP, respectively. Heart rate increased from 69 (CI: 65-73) during placebo to 78 (CI: 72-84) and to 84 (CI: 77-92) after infusions of GTN and SNP, respectively (p<0.01 for all comparisons). However, no increase in exhaled NO was detected: endexpiratory NO-concentrations averaged 6.1 ppb (CI: 4.9-7.4), 5.7 ppb (CI: 4.4-7.0) and 6.4 ppb (CI: 5.3-7.6) under placebo, GTN and SNP infusions, respectively (Friedman ANOVA p=0.328). NO release from within the pulmonary vasculature does not significantly contribute to endexpiratory NO concentrations in non-intubated healthy humans suggesting that such NO measurements quantify NO production mainly from non-vascular pulmonary cells.

Glucocorticoids dose-dependently increase plasma levels of granulocyte colony stimulating factor in man

Glucocorticoids increase neutrophil counts by decreasing the margination of neutrophils and mobilizing neutrophils from the bone marrow pool. The mechanisms for these effects however are not fully elucidated, but it has been demonstrated that dexamethasone enhances release of colony stimulating factor (G-CSF) in-vitro. We therefore hypothesized, that dexamethasone may increase plasma levels of G-CSF. A double blind, randomized, placebo-controlled, three-way cross-over trial was conducted in nine healthy men. Every subject received four identical infusions of saline, 0.04 mg/kg or 1.0 mg/kg dexamethasone during three observation periods of 48 hours each. The low dose of dexamethasone increased G-CSF levels from a baseline of 15.5 ng/L (CI: 10.6-20.4) by 240% (CI: 115-366%) at 24 hours. The high dexamethasone dose increased G-CSF levels from a baseline of 12.3 ng/L (CI: 9.7-14.9) by 871% (CI: 592-1149%) at 24 hours (p=0.008 for all comparisons). No further increase was observed at 48 hours but the effect was less pronounced (p<0.008 and p=0.08 for the high and the low dose of dexamethasone, respectively). Granulocyte-macrophage-CSF (GM-CSF) levels were below the assay's detection limit of 0.36 ng/L in all subjects. In conclusion, dexamethasone dose dependently increases G-CSF levels in healthy men, an effect which may account for some of its effects on neutrophils.

Jugular venous bulb oxygen saturation depends on blood pressure during cardiopulmonary bypass

BACKGROUND

Central nervous system dysfunction after cardiopulmonary bypass is frequent and can be caused by inadequate cerebral perfusion and oxygenation.

METHODS

To test the effectiveness of cerebral autoregulation during cardiopulmonary bypass, we induced changes in the cerebral perfusion pressure by administering phenylephrine during moderate (29 degrees C) hypothermia. Using the Fick principle, we calculated relative changes in cerebral blood flow from changes in the jugular venous bulb oxygen saturation.

RESULTS

Increasing the cerebral perfusion pressure (from 47 +/- 8.2 to 93 +/- 16 mm Hg) induced increases in the jugular venous bulb oxygen saturation by 4.9% and a calculated increase in the cerebral blood flow by 19.9%, strongly suggesting impaired cerebral autoregulation.

CONCLUSIONS

Because cerebral autoregulation is impaired during cardiopulmonary bypass, phenylephrine is effective in increasing the cerebral blood flow and may contribute to the prevention of postoperative neurologic dysfunction, especially in patients who have a low jugular venous bulb oxygen saturation.

Effects of histamine and nitric oxide synthase inhibition on plasma levels of von Willebrand factor antigen

Endothelial cells release von Willebrand factor (vWf) either constitutively or by a regulated pathway. Based on various studies in vitro, we hypothesized that the stimulatory action of histamine on vWf release could also be induced in vivo and that it may be inhibited by endogenous production of nitric oxide (NO). Nine healthy subjects received placebo or one of two dosages of a primed constant infusion of the NO-synthase inhibitor N-monomethyl-L-arginine (L-NMMA) in a randomized, double-blind, three-way crossover trial. Histamine was coinfused for 15 minutes at 0.16 microg/kg/min after 30 minutes of pretreatment with either placebo or L-NMMA. Thirty minutes after either the low or the high L-NMMA dose was started, which caused, respectively, a 40% decrease and a 60% decrease in exhaled end expiratory NO level (p = 0.008), there was no increase in von Willebrand factor antigen (vWf-Ag) level (p > 0.05). Histamine caused an 11% (95% confidence interval (CI): 0.4% to 22%; p = 0.011) increase in vWf-Ag level at 125 minutes. After pretreatment with the low and the high L-NMMA doses, vWf-Ag level increased by 18% (Cl: 5% to 31%; p = 0.011) and by 29% (CI: 15% to 42%; p = 0.008), respectively. At 125 minutes, vWf-Ag level was significantly higher after either L-NMMA pretreatment when compared with the results after histamine alone (p < 0.05). In conclusion, the infusion of histamine increased vWf-Ag level, and the inhibition of NO-synthase enhanced this effect, whereas it did not by itself elevate vWf-Ag level. Thus endogenously produced NO may dampen the regulated pathway of vWf secretion; it will be interesting to investigate whether endogenous NO production also inhibits vWf release caused by other stimulators.

Does phosphodiesterase III inhibition reverse the cardiodepressive effects of propofol?

Propofol decreases arterial blood pressure as a result of reduced cardiac output and peripheral vasodilation, raising concerns about its safety in patients with impaired cardiovascular function. Phosphodiesterase III inhibitors (PDE-III-Inh) have gained attention as inotropic drugs. We therefore studied whether the cardiac effects of propofol could be abrogated by enoximone. Twenty-one patients with moderately reduced cardiac function scheduled for major surgery were allocated to this randomized, double-blind, placebo-controlled study. Measurement of cardiovascular data was performed before induction, 15 min after initiation of total intravenous anesthesia, 15 min after a first bolus of 0.25 mg/kg enoximone or placebo, and 15 min after a second bolus of 0.25 mg/kg enoximone or placebo. Propofol led to the expected reduction of cardiac output and bradycardia. Both doses of enoximone increased the cardiac index, reaching nearly preinduction values at a cumulative dose of 0.5 mg/kg enoximone. This change was primarily the result of significantly increased heart rate rather than increased ejection fraction or stroke volume index. Mean arterial pressure remained constant, which indicates uncompromised coronary perfusion pressure. Based on our results, we cannot recommend enoximone for the treatment of propofol-induced cardiac impairment.

IMPLICATIONS

Total intravenous anesthesia with propofol is used increasingly in patients with impaired cardiac function. Enoximone, a drug suggested for congestive heart failure, had no effect on stroke volume or mean arterial pressure, but it increased heart rate. Enoximone is not recommended to treat impairment of cardiac function in patients anesthetized with propofol.

Prospective randomized comparison of cefodizime versus cefuroxime for perioperative prophylaxis in patients undergoing coronary artery bypass grafting

The effects of cefodizime and cefuroxime on neutrophil phagocytosis and reactive oxygen production in 54 patients undergoing elective coronary artery bypass grafting were studied. Both drugs were administered twice at a dosage of 40 mg/kg of body weight (pre- and intraoperative). Phagocytic capacity was assessed by measuring the uptake of fluorescein isothiocyanate-labeled Escherichia coli and Staphylococcus aureus by flow cytometry. Reactive oxygen generation after phagocytosis was estimated by determining the amount of dihydrorhodamine 123 converted to rhodamine 123 intracellularly. In both groups the mean phagocytic ability for E. coli and S. aureus decreased during surgery (-21 and -8%, respectively, for the cefodizime group and -39 and -38%, respectively, for the cefuroxime group; P < 0.05 for all). In the cefodizime group a normalization of mean E. coli and S. aureus neutrophil phagocytosis was seen on day 5 (+9 and -4% compared to preoperative values; P > 0.35 for both), whereas in cefuroxime-treated patients phagocytic ability remained depressed (-37 and -31%; P < 0.04 for both). In both groups mean neutrophil reactive oxygen intermediate (ROI) production after E. coli and S. aureus phagocytosis increased during cardiopulmonary bypass (+44 and +83%, respectively, in the cefodizime group and +58 and +73%, respectively, in the cefuroxime group; P < 0.05 for all). One day after surgery E. coli- and S. aureus-driven neutrophil ROI production was not different from the preoperative values (-2 and +12%, respectively, for the cefodizime group and +7 and +15%, respectively, for the cefuroxime group; P > 0.15 for all). Postoperative serum levels of the C-reactive protein on days 2 and 7 were lower in cefodizime-treated patients (19 +/- 6 and 4 +/- 2 mg/liter versus 23 +/- 6 and 11 +/- 5 mg/liter; P < 0.05 for both). In addition to cefodizime's antimicrobial activity during perioperative prophylaxis, its use in coronary artery bypass grafting can prevent procedure-related prolonged postoperative neutrophil phagocytosis impairment.

Malposition of central venous catheters. Incidence, management and preventive practices

INTRODUCTION

Proper placement is an essential prerequisite for the use of central venous catheters. Our study was undertaken to determine the incidence of aberrant locations dependent on different anatomic approaches for various types of central venous catheters and to elucidate failures and pitfalls of preventive practices.

METHODS

2580 percutaneously inserted lines (including 538 tunneled devices and 112 implantable Port-A-Caths) introduced by Seldinger's technique were reviewed for inadvertent malpositioning.

RESULTS

Primary misplacement was evident on 47 occasions (1.82%), 38 times into large venous tributaries of the superior vena cava. 3 aberrant locations involved a persistent left superior vena cava, two catheters were placed into minor intrathoracic veins and in 3 patients inadvertent arterial cannulation occurred. The frequency of malpositioning was related to the anatomic approach and the catheter type used, but not to the physician's experience. Respective incidences were 4.12% for the left internal jugular access, but were lower for the right internal jugular (1.1%) and the right (1.01%) and left (0.89%) supraclavicular approach. Misplacement was more frequent with soft silicone catheters (2.53%) than with semi-rigid catheters (0.79%). All malpositions but one were detected on chest X-ray.

DISCUSSION

Our data suggest that the incidence of catheter malposition depends on the site of insertion, the type of material used, but not on the experience of the physician who inserted the catheter. Scrupulous use of preventive practices reduces the frequency of malpositioned catheters, but physicians must keep in mind potential pitfalls. Injection of radioopaque contrast medium into the catheter during control chest X-ray should be done even with opaque catheters.

Clinical trial of a new device for fiberoptic orotracheal intubation (Augustine Scope)

Blind oral intubation using the Augustine Guide is helpful for intubating the trachea of patients presenting with difficult airways. This device has been modified by adding a fiberoptic scope with a built-in battery-powered light. We studied this Augustine Scope in 104 patients (Group AS) and compared the results with 96 patients managed by direct laryngoscopy (Group DL). No significant differences in Mallampati class, thyromental distance, laryngoscopic view, and patients height or weight were observed between the two groups. The Augustine Scope provided conditions for successful intubation in 102 of 104 patients (98%), compared with a 97% success rate in the group where DL was used. The three patients who failed DL were successfully intubated with AS. The mean +/- SD time needed to perform intubation was 19 +/- 10 s in Group AS and 21 +/- 13 s in Group DL (P = not significant). No traumatizing effects were observed. We conclude that the Augustine Scope is an effective and safe device for orotracheal intubation in routine and difficult airways.

The acute respiratory distress syndrome: definitions, severity and clinical outcome. An analysis of 101 clinical investigations

OBJECTIVE

To determine possible changes in outcome from acute respiratory distress syndrome (ARDS) and to compare severity of lung injury and methods of treatment from 1967 to 1994.

DATA SOURCES

Computerized (Medline, Current Contents) and manual (Cumulated Index Medicus) literature search using the key word and/or title ARDS.

STUDY SELECTION

Only clinical studies published as full papers reporting data on both patient mortality (survival) and oxygenation index (PaO2/FIO2) were included. Single case reports, abstracts, reviews and editorials were excluded from evaluation.

DATA EXTRACTION

Relevant data were extracted in duplicate, followed by quality checks on approximately 80% of data extracted.

DATA SYNTHESIS

101 papers reporting on 3264 patients were included: 48 studies (2207 patients) were performed in the USA, 43 studies (742 patients) in Europe and 10 studies (315 patients) elsewhere. Mortality reported in these studies was 53 +/- 22% (mean +/- SD), with no apparent trend towards a higher survival (1994: 22 studies, mortality 51 +/- 19%). The mean PaO2/FIO2 ratio remained unchanged throughout the observation period (118 +/- 47 mmHg). No correlation could be established between outcome and PaO2/FIO2 or lung injury score. Patients who underwent pressure-limited ventilation had a significantly lower mortality (35 +/- 20%) than patients on volume-cycled ventilation (54 +/- 22%) or patients for whom there was no precise information on ventilatory support (59 +/- 19%). Significantly lower PaO2/FIO2 ratios (61 +/- 17 mmHg) were observed in patients prior to extracorporeal lung assist, together with mortality rates in the range of those for conventionally treated patients (55 +/- 22%).

CONCLUSIONS

The mortality of ARDS patients remained constant throughout the period studied. Therefore, the standard for outcome in ARDS should be a mortality in the 50% range. Neither PaO2/FIO2 ratio nor lung injury score was a reliable predictor for outcome in ARDS. Patients might benefit from pressure-limited ventilatory support, as well as extracorporeal lung assist. Since crucial data were missing in most clinical studies, thus preventing direct comparison, we emphasize the importance of using standardized definitions and study entry criteria.

Endocrine stress reaction to surgery in brain-dead organ donors

We studied the course of plasma levels of the stress markers adrenocorticotropic hormone (ACTH), cortisol, human growth hormone (h-GH), beta-endorphin, and prolactin during retrieval surgery in eleven brain-dead organ donors scheduled for multiple organ explantation. Donors were divided into two groups according to hemodynamic stability. Hormones demonstrated a great variability in plasma levels and in the pattern of reaction, revealing a different degree of remaining pituitary function. Beta-Endorphin was the only stress hormone that showed a response to surgical stimuli in six patients. Only three of them developed a concomitant rise in ACTH. Cortisol, prolactin, and h-GH plasma levels did not change during the observation period. In the three cases with a slight elevation in ACTH, no subsequent change in cortisol was detectable. Beta-Endorphin showed greater variability and a tendency to higher levels in the group presenting with a higher arterial pressure, which resulted in a significant difference (P < 0.005) when distributions were compared using the Mann-Whitney U-test. No correlation was found between hypotensive episodes and deficiencies of other stress hormones. We conclude that pituitary function varies considerably in brain-dead organ donors without demonstrating a correlation to the onset of hypotension. Thus, we feel no need for a substitution treatment with any of the hormones investigated prior to organ explanation.

Optimal values for oxygen transport during hypothermia in sepsis and ARDS

Mild hypothermia (33 degrees C to 35.5 degrees C) is reported to improve oxygenation and survival in patients with lung failure (1). Although hypermetabolism may account for about 50% of the ventilatory demand in ARDS patients, the concept of reducing oxygen consumption (VO2) by lowering metabolic rate, has only recently gained attention (2). Our study was aimed to test whether mild hypothermia established by continuous veno-venous haemofiltration (CVVHF), could optimize values for oxygen kinetics in ARDS patients. Overall, we recruited 27 patients with ARDS and sepsis. Prior initiation of CVVHF patients had to meet the following criteria: a) Murray score > 2.5, and hypoxaemia with PaO2/FIO2 < 200, b) hyperthermia of > 38 degrees C, c) cardiovascular instability requiring inotropic support. Evaluation of cardio-respiratory data was performed within four different phases (I = before, II + III during and IV = after CVVHF) every 6 hours. Core temperature as derived from the thermistor of pulmonary artery catheter was aimed to be between 35.0 degrees C and 36.5 degrees C. Optimal values for oxygen delivery (DO2) (> 550 mL/min/m2) and VO2 (> 160 mL/min/m2) were defined according to Shoemaker and achieved by fluid loading, transfusion and inotropic support (3). Septic shock occurred in 10 of 14 nonsurvivors (nons) and 2 of 13 survivors (surv). Mean values for DO2 and VO2 were calculated at different body temperature ranges. While at 37 degrees C DO2 was identical between surv and nons, (663 +/- 128 versus 666 +/- 127 means +/- SD) moderate hypothermia led to a small decrease of DO2 in surv and a significant decrease in nons (632 +/- 134 versus 605 +/- 128 mL/min/m2) at 35 degrees C. Concerning VO2 during hypothermia, there was a significant drop in nonsurvivors while in survivors the decrease was less pronounced. We could demonstrate a decrease in DO2 and VO2 during mild hypothermia during CVVHF. However, decreases in nonsurvivors were more pronounced than in survivors. These results suggest that the inability to achieve optimal values for DO2 and VO2 during mild hypothermia induced by CVVHF could serve as a prognostic sign for fatal outcome. Although oxygen consumption is decreased during hypothermia, hypoxaemia may result due to alterations of the oxygen transport on a cellular basis. The relationship between oxygen transport and temperature during CVVHF therefore deserves further studies.

Stress response to tracheal intubation: direct laryngoscopy compared with blind oral intubation

Haemodynamic and hormonal responses to tracheal intubation can be profound and associated with serious cardiovascular and cerebral side effects. The Augustine Guide, a device enabling blind oral intubation, has been introduced recently. The aim of our study was to compare the haemodynamic and hormonal stress response of this method with direct laryngoscopy. Thirty five patients (ASA 1 and 2) were randomly assigned to undergo either direct laryngoscopy (n = 17), or blind oral intubation (n = 18). Haemodynamic responses and concentrations of adrenaline, noradrenaline and prolactin were determined prior to induction, before intubation and 5 min after intubation. The median duration of intubation was 22s for direct laryngoscopy vs 46s for blind oral intubation (p < 0.05). Between the groups, no significant differences were observed for heart rate, systolic or mean arterial blood pressure. Serum levels of adrenaline decreased slightly after induction and remained unaltered after intubation in both groups. Noradrenaline (1.01 vs 0.66 nmol.l-1) and prolactin (5.2 vs 2.9 nmol.l-1) levels were significantly higher after direct laryngoscopy compared to blind oral intubation. Although blind oral intubation took significantly longer to perform than direct laryngoscopy, hormonal stress response was less pronounced. Blind oral intubation should therefore not be withheld from patients with impaired cardiovascular reserve.

Prehospital emergency medicine services in Europe: structure and equipment

In order to get an update on prehospital emergency medicine practice all over Europe we submitted questionnaires with a total of 61 questions concerning prehospital emergency medicine in Europe, to 123 European members of the World Association of Emergency and Disaster Medicine (WAEDM). Sixty (49%) questionnaires were returned. One up to seven questionnaires from 22 European countries were analysed: 37 (62%) from urban and 23 (38%) suburban or rural areas; 12 being from former Eastern European countries. Sixteen of the questions--those concerning rescue systems and equipment--are analysed and presented in this paper. A fleet of ambulance cars staffed with paramedics/nurses based at the emergency organization is the most frequently used system in 59% (10/17) of the countries. The same percentage claims to have a ground-based coverage of its area of 80-100%. Airborne coverage between 80-100% and below 60% of the areas is given in the same percentage of 35% (6/17). Physicians are frequently involved in prehospital emergency care in the Eastern European Countries, France, Germany, Italy, Belgium and Turkey, rarely in Switzerland, Denmark, the United Kingdom, Greece, Ireland and Finland, never in the Netherlands and Sweden. In more than 50%, a combination of national, regional and local organizations provide emergency care, which results in large differences of standards. We discovered remarkable differences which could be overcome by enhanced co-ordination and information exchange provided by the European Society for Emergency Medicine, WAEDM, the European Red Cross or the European Academy of Anaesthesiologists.

A new device for blind oral intubation in routine and difficult airway management

41 patients (ASA I-II) were intubated using a new device for blind oral intubation (Augustine Guide). A group of 33 consecutive patients (Mallampati I and II), was studied for routine intubation. Another group of eight patients (Mallampati III and IV) was selected to study the guide in difficult airway management. Intubation was successful in 31 of the 33 normal patients (two patients required a second attempt), and in seven of the eight patients in the difficult intubation group (three patients with two attempts). In the remaining three patients intubation had to be performed by direct laryngoscopy. One patient (Mallampati IV), was intubated by the Augustine guide after three unsuccessful attempts by direct laryngoscopy. The Augustine Guide proved to be helpful to intubating patients with an anterior larynx and receding mandible. However, blind oral intubation attempts required a median duration of 65 s (range 35-90 s). Patients with a low Mallampati score did not benefit from the new device.

Excursions of the cervical spine during tracheal intubation: blind oral intubation compared with direct laryngoscopy

The most appropriate technique for performing tracheal intubation in patients with cervical spine injury is debatable. Recently, a new device enabling blind oral intubation (Augustine Guide) with the patient's head and neck in the neutral position has been introduced. The aim of this study was to compare the extent of upper cervical spine movement during intubation with this device compared to direct laryngoscopy. Twelve patients (Mallampati I and II), without a cervical spine injury, were intubated using the Augustine Guide and afterwards by direct laryngoscopy. Both procedures were viewed radiographically. Extension in the upper cervical spine was determined at the point of the maximum excursion. By evaluating the joints occiput-C3 together as a functional unit, blind oral intubation caused 17 degrees (median) less extension compared to direct laryngoscopy (p < 0.01). The median differences observed for the individual joints were: 7 degrees in occiput-C1 (p < 0.05), 5 degrees in C1-2 (p < 0.01) and 6 degrees in C2-3 (p < 0.01) respectively. Since we assume that intubation-induced excursions of the injured spine are even higher, blind oral intubation might be a safe alternative for airway management in this special group of trauma victims.

Influence of cell cycle on glutathione-S-transferase, selenium-dependent glutathione peroxidase, superoxide dismutase and glutathione levels in human myeloid leukaemia cell lines

An important biological function of glutathione (GSH) resides in the detoxication reactions mediated by enzymes such as glutathione-S-transferase (GSTs) and glutathione peroxidase (GPX). An increasing body of evidence implies that GSH and these enzymes play important roles in determining the sensitivity of tumours against cytotoxic drugs like quinone antibiotics, in particular adriamycin (Adr). In the present study, we have analysed the effects of cell-cycle on GSH and GSH-dependent enzymes in an attempt to explain cell-cycle specificity of these antileukaemic drugs which were shown to be involved in free-radical-type reactions. Determination of GSH, GST, GPX and superoxide dismutase in cell-cycle-enriched fractions of five different human myeloid leukaemia cell lines (KG1, K562, U937, ML-1 and ML-2) yielded results identical to those obtained in random cultures, which implies that neither GSH nor GSH-related enzymes are cell-cycle regulated. These findings argue against the presumption that cell-cycle specificity of cytotoxic drugs like Adr could be due to the glutathione-dependent metabolism in myeloid leukaemia cell lines.

Expression of a binding structure for sialic acid-containing glycoconjugates on rat bone marrow-derived macrophages and its modulation by IFN, TNF-alpha, and dexamethasone

Rat macrophages express a binding structure for sialic acid-containing glycoconjugates (sialic acid-binding receptor, SAR) which can be detected by a rosette assay utilizing SRBC coated with bovine brain gangliosides (E-G). Freshly isolated rat bone marrow cells (BMC) contain about 5% SAR-positive cells. Rat BMC cultured for 1 wk with tissue culture media containing CSF-1 differentiate into a virtually pure population of bone marrow-derived macrophages (BMDM phi). All BMDM phi bound E-G coated with an optimal concentration of gangliosides (100 micrograms/ml). When BMC were cultured for 1 wk with murine recombinant granulocyte-macrophage CSF, irrespective of the dose of GM-CSF, approximately 90% of the cells were identified as rat macrophages, and practically all expressed SAR. Only about 50% of BMDM phi bound SRBC coated with a suboptimal concentration of gangliosides (20 micrograms/ml). However, this percentage increased markedly after 8 to 72 h incubation with 1 to 10,000 U/ml purified murine IFN-alpha or IFN-beta, whereas murine or rat rIFN-gamma at doses above 10 U/ml led to a decrease of E-G binding. Human and murine rTNF-alpha enhanced rosette formation in a dose-dependent manner. These effects could be blocked by the respective anti-cytokine antibodies. Treatment of BMDM phi with dexamethasone also augmented E-G rosetting. The enhancement of E-G binding was abolished by pretreatment of BMDM phi with cycloheximide and actinomycin D but not with mitomycin C, suggesting that de novo synthesis of protein and RNA, but not DNA, is required. Our results demonstrate that all rat BMDM phi constitutively bear SAR, and that murine IFN-alpha, IFN-beta, and TNF-alpha, as well as dexamethasone, may augment SAR expression.

Expression of a binding structure for sialic acid-containing glycoconjugates on rat bone marrow-derived macrophages and its modulation by IFN, TNF-alpha, and dexamethasone

Rat macrophages express a binding structure for sialic acid-containing glycoconjugates (sialic acid-binding receptor, SAR) which can be detected by a rosette assay utilizing SRBC coated with bovine brain gangliosides (E-G). Freshly isolated rat bone marrow cells (BMC) contain about 5% SAR-positive cells. Rat BMC cultured for 1 wk with tissue culture media containing CSF-1 differentiate into a virtually pure population of bone marrow-derived macrophages (BMDM phi). All BMDM phi bound E-G coated with an optimal concentration of gangliosides (100 micrograms/ml). When BMC were cultured for 1 wk with murine recombinant granulocyte-macrophage CSF, irrespective of the dose of GM-CSF, approximately 90% of the cells were identified as rat macrophages, and practically all expressed SAR. Only about 50% of BMDM phi bound SRBC coated with a suboptimal concentration of gangliosides (20 micrograms/ml). However, this percentage increased markedly after 8 to 72 h incubation with 1 to 10,000 U/ml purified murine IFN-alpha or IFN-beta, whereas murine or rat rIFN-gamma at doses above 10 U/ml led to a decrease of E-G binding. Human and murine rTNF-alpha enhanced rosette formation in a dose-dependent manner. These effects could be blocked by the respective anti-cytokine antibodies. Treatment of BMDM phi with dexamethasone also augmented E-G rosetting. The enhancement of E-G binding was abolished by pretreatment of BMDM phi with cycloheximide and actinomycin D but not with mitomycin C, suggesting that de novo synthesis of protein and RNA, but not DNA, is required. Our results demonstrate that all rat BMDM phi constitutively bear SAR, and that murine IFN-alpha, IFN-beta, and TNF-alpha, as well as dexamethasone, may augment SAR expression.

Murine recombinant GM-CSF-driven rat bone marrow cell differentiation and factors suppressing cell proliferation

Rat or mouse bone marrow cells (BMC) cultured for one week with a crude mouse L929 cell supernatant or with purified colony stimulating factor type 1 (CSF-1) differentiate into an essentially pure population of macrophages (M phi). Surprisingly, 90 to 95% of the cells obtained by culturing rat BMC for seven days with recombinant murine granulocyte-macrophage CSF (rmGM-CSF), regardless of concentrations, were classified as M phi. The majority of the remaining cells were granulocytes. This effect is in contrast to that on mouse BMC cultures, where the percentage of granulocytes increased with higher concentrations of rmGM-CSF. The proliferative capacity of rat BMC was demonstrated by colony formation in soft-agar, enumerating total cell number in liquid cultures or measuring 3H-thymidine uptake. A crude L929 cell supernatant and rmGM-CSF induced cell proliferation in a dose-dependent manner. Maximal DNA-synthesis was observed on the fifth day of incubation when BMC were cultured at a density of greater than or equal to 1 x 10(5) cells/well. In cultures initiated with lower cell density, prolonged DNA synthesis was observed. Thereafter, the rate of proliferation declined rapidly. Simultaneous incubation of BMC with GM-CSF and indomethacin led to increased levels of DNA synthesis, suggesting that prostaglandins may suppress cell proliferation. Furthermore, the CSF-induced BMC proliferation was dose dependently inhibited by dexamethasone and 1,25-dihydroxy-vitamin D3 as well as by interferon-gamma and tumor necrosis factor-alpha. The suppressive effect of both cytokines could be abrogated by the addition of the respective anticytokine antibodies.