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Biomedical subjects

M Zimpfer

Publications and source records attributed to M Zimpfer.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of hypothermia on thrombelastography in patients undergoing cardiopulmonary bypass.

Thrombelastography (TEG) correlates with postoperative chest drain output in patients undergoing cardiopulmonary bypass (CPB). In vitro incubation with heparinase allows TEG monitoring during CPB, despite heparin anticoagulation. Hypothermia impairs coagulation, but these effects cannot be assessed by standard coagulation tests performed at 37 degrees C. The aim of this study was to assess the effects of hypothermia on TEG. Therefore, we have compared normothermic and temperature-adapted TEG in 30 patients undergoing CPB. Our data showed significantly impaired reaction time (r), kinetic time (k), and angle alpha (alpha) in temperature-adapted compared with normothermic TEG. Maximum amplitude (MA), reflecting absolute clot strength, was not affected at temperatures of 33-37 degrees C. These findings indicate a decrease in the speed of clot formation, but not absolute deterioration in clot quality. Furthermore, heparinase-modified TEG indicated that there were nine cases in which heparin effects persisted after heparin reversal with protamine, providing a rational guide to protamine therapy.

Adult↗
PubMed1998

Endogenous heparin-like substances significantly impair coagulation in patients undergoing orthotopic liver transplantation.

UNLABELLED: Orthotopic liver transplantation (OLT) is associated with severe bleeding, especially after reperfusion of the grafted liver. Heparin released from the liver graft contributes to postreperfusion coagulopathy. Although patients with liver cirrhosis have increased levels of endogenous heparinoids, the role of these substances during liver transplantation is unclear. Therefore, we performed native and heparinase-modified thrombelastography (TEG) in 72 patients undergoing OLT. TEG was performed at skin incision, 10 min before and 10 min after clamping of the vena cava, 10 min before and 10 min after graft perfusion, and at the end of surgery. Heparinase-modified TEG compared with native TEG demonstrated heparin activity. In contrast to other investigations, we found significant heparin effects before reperfusion, although patients received no exogenous heparin. These heparin effects were greater in patients with cirrhosis compared with patients with cancer as the underlying disease leading to OLT. Administration of coagulation factors is the usual treatment of coagulopathies during OLT. The comparison of native versus heparinase-modified TEG can distinguish between heparin activity or coagulation factor deficiency as a cause of bleeding complications and provides a rational approach to the treatment of bleeding during OLT. IMPLICATIONS: Impaired coagulation function, contributed to by heparin or heparin-like substances, is frequently observed after reperfusion of a transplanted liver. This study demonstrates that a heparinase-modified thrombelastography can identify significant heparin effects in the absence of exogenous heparin administration in patients undergoing liver transplantation.

Anticoagulants↗
PubMed1998

The effect of hydroxyethyl starch on platelet aggregation in vitro.

UNLABELLED: The effect of hydroxyethyl starch (HES) on hemostasis seems to be minimal when it is used in recommended amounts. A number of studies have investigated the effect of HES on platelet function when administered in vivo, but there has been no study investigating the effect on the isolated platelet function when administered in vitro. A photometrical method to assess platelet function in platelet-rich plasma (approximately 250 x 10(9) platelets/L) was used with platelet aggregation induced using either collagen, epinephrine, adenosine diphosphate, or ristocetin. We found a dose-dependent decrease of platelet aggregation in vitro with either collagen or epinephrine, but not with adenosine diphosphate or ristocetin. However, the changes of HES on platelet aggregation were detected only in doses larger than those routinely used in the clinical setting. Therefore, we conclude that the influence of HES at the recommended doses on initial platelet aggregation may not be clinically relevant. IMPLICATIONS: The effect of hydroxyethyl starch on platelet function and coagulation is discussed. This study showed no influence on platelets in clinically relevant doses in an in vitro model.

Adenosine Diphosphate↗
PubMed1998

Anticoagulation with prostaglandin E1 and unfractionated heparin during continuous venovenous hemofiltration.

OBJECTIVE: To determine the effect of two doses of prostaglandin E1 (PGE1, alprostadil) combined with unfractionated heparin on the hemofilter life-span and the coagulation profile during continuous venovenous hemofiltration. DESIGN: Prospective, randomized, controlled trial. SETTING: Intensive care unit at a university-affiliated hospital. PATIENTS: Twenty-four critically ill, mechanically ventilated patients with postoperative acute renal failure who require continuous venovenous hemofiltration. INTERVENTIONS: The patients were anticoagulated with 5 ng/kg/min PGE1 and 6 IU/kg/hr heparin or 20 ng/kg/min PGE1 and 6 IU/kg/hr heparin, injected into the extracorporeal circuit before the hemofilter. MEASUREMENTS AND MAIN RESULTS: The life-span of 43 hemofilters was evaluated. They were used until extracorporeal line pressure exceeded 250 mm Hg, ultrafiltration rate decreased to 16 mL/min, or grossly visible extracorporeal clotting occurred. Blood was sampled from the afferent (prefilter) and efferent (postfilter) lines of the extracorporeal circuit. Platelet counts, in vitro platelet function, plasma concentrations of platelet factor 4, prothrombin fragment F1+2, thrombin-antithrombin complex, routine plasma coagulation tests, and hemodynamic profile were determined before and during hemofiltration. Hemofilter usage was significantly longer in patients anticoagulated with 20 ng/kg/min PGE1 (32 +/- 3 [SEM] hrs) than with 5 ng/kg/min PGE1 (22 +/- 3 hrs). In vitro bleeding parameters were significantly prolonged in postfilter blood in patients receiving 20 ng/kg/min PGE1. Prefilter, there was no antiplatelet activity in either group and platelet counts remained stable. No intra- or intergroup differences in plasma coagulation profile or hemodynamic parameters were detected. CONCLUSION: Extracorporeal administration of PGE1, combined with low-dose heparinization, inhibits platelet reactivity and preserves hemofilter life dose-dependently.

APACHE↗
PubMed1998

High-dose recombinant human erythropoietin stimulates reticulocyte production in patients with multiple organ dysfunction syndrome.

OBJECTIVE: To investigate erythropoietin (EPO) production and the erythropoietic potency of recombinant human EPO in the multiple organ dysfunction syndrome. DESIGN: Randomized, prospective, controlled clinical trial. MATERIALS AND METHODS: Patients received either 600 IU/kg intravenous EPO three times weekly (n = 9) or saline (control, n = 10). MEASUREMENTS: EPO levels, circulating soluble receptors for tumor necrosis factor and interleukin-2, levels of interleukin-6 and intercellular adhesion molecule, and early peripheral blood cell progenitors. RESULTS: EPO production in the control group remained low. Pharmacologic EPO blood levels were associated with increased reticulocyte counts compared with both controls (p < 0.04) and baseline (p < 0.006). Increased levels of soluble receptors for tumor necrosis factor in the treatment group compared with the controls did not prevent this effect. Interleukin 6 inhibited reticulocyte production. CONCLUSION: Despite increased cytokine levels, pharmacologic EPO blood levels were associated with increased reticulocyte counts in patients with multiple organ dysfunction syndrome.

Cytokines↗
PubMed1998

Addition of nitric oxide to oxygen improves cardiopulmonary function in patients with severe COPD.

STUDY OBJECTIVE: To assess the effect of nitric oxide inhalation on pulmonary hemodynamics and oxygenation in patients with COPD receiving long-term oxygen therapy (LTOT). DESIGN: Prospective study. SETTING: ICU of a university medical center. PATIENTS: A total of 18 (6 female, 12 male) patients with COPD, spontaneously breathing with LTOT. INTERVENTIONS: Oxygenation and hemodynamic variables were measured and calculated at an inspired oxygen fraction (FIO2) adjusted to mimic LTOT conditions (control), and then 1 h after each sequential addition of 5, 10, and 20 ppm nitric oxide to the gas mixture. A newly developed device (Pulmonox) provided both the delivery and continuous analysis of nitric oxide and oxidative nitric oxide products. MEASUREMENTS AND RESULTS: There was a significant improvement in oxygenation at 5 ppm nitric oxide (PaO2/FIO2 ratio improved from 244+/-37 to 303+/-59, p<0.05), but no further improvement at higher doses (ceiling effect). There was a dose-dependent improvement in hemodynamic variables that was maximal at 20 ppm nitric oxide (mean pulmonary artery pressure decreased from 29+/-7 to 24+/-5 mm Hg, pulmonary vascular resistance index decreased from 565+/-321 to 392+/-215 dyne x s x cm(-5) x m(-2), and right ventricular ejection fraction improved from 34+/-6 to 39+/-7%, all p<0.05). CONCLUSION: Prior studies have demonstrated that inhaled nitric oxide may improve or worsen oxygenation in patients with COPD. Our data show an unequivocal improvement in oxygenation (albeit with a ceiling effect at 5 ppm) and pulmonary hemodynamics (dose dependent) in COPD patients receiving LTOT. Further studies are warranted to examine the usefulness of inhaled nitric oxide during acute exacerbations of COPD, or even the possibility of long-term application in patients receiving LTOT.

Administration, Inhalation↗
PubMed1997

A rare presentation of thoracic aortic dissection as detected by transoesophageal echocardiography.

A case of atypical movement of the intimal flap (tear) during aortic aneurysm dissection is reported. Aortic dissection is caused by the sudden development of a tear in the aortic intima, opening the way for a column of blood driven by the force of the arterial pressure to enter the aortic wall, destroying the media and stripping the intima from the adventitia for variable distance along the length of the aorta. Echocardiographically, aortic dissection is characterized by separation of the normal single dominant echo from the aortic wall in the region of the dissection into two discrete echoes. The inner echo arises from the tunica intima, whereas the outer echo arises from the medial and adventitial structures external to the tear and it is possible to identify two lumens separated by an intimal flap within the aorta. The two echoes generally move in unison with one another, i.e. movement of the flap away from the true lumen during systole and recoil during diastole as the blood flows from true to false lumen. The dissection flap can also move inward during systole owing to the suction caused by high-velocity flow (Venturi effect), as shown in this case report. In any instances, motion of the intimal flap during the cardiac cycle is strong evidence of dissecting aneurysm.

Aged↗
PubMed1997

Biplane transoesophageal echocardiographic detection of myocardial ischaemia in patients with coronary artery disease undergoing non-cardiac surgery: segmental wall motion vs. electrocardiography and haemodynamic performance.

Intra-operative segmental wall motion abnormalities (SWMA) detected by transoesophageal echocardiography (TOE) have been shown to be a sensitive indicator of myocardial ischaemia. To determine the incidence and characteristics of segmental wall motion abnormalities and to relate these changes to perioperative myocardial ischaemia, biplane TEE, electrocardiogram (ECG) (II+V5) and pulmonary capillary wedge pressure (PCWP) were continuously monitored in 62 consecutive patients with ischaemic heart disease undergoing non-cardiac surgery. Short-axis view at mid-papillary level in transverse scan (T-scan) and long-axis in longitudinal (L-scan) two-chamber view were used for wall motion analysis. New segmental wall motion abnormalities were detected in 16 of 64 patients (25%) using biplane transoesophageal echocardiography. Monoplane transoesophageal echocardiography showed a sensitivity of 75% and a specificity of 100%, electrocardiogram two lead showed a sensitivity of 56% and a specificity of 98%, whereas pulmonary capillary wedge pressure had a sensitivity of 25%, and a specificity of 93% and pressure rate quotient (PRQ) < 1 demonstrated sensitivity of 19% and a specificity of 92% in the detection of myocardial ischaemia. It is concluded that the long-axis view of the left ventricle provides additional information for the detection of segmental wall motion abnormalities. Neither changes in haemodynamic performance nor in electrocardiography leads II and V5 match those of transoesophageal echocardiography for the identification of myocardial ischaemia.

Adult↗
PubMed1997

Validity of acoustic quantification colour kinesis for detection of left ventricular regional wall motion abnormalities: a transoesophageal echocardiographic study.

Transoesophageal echocardiography is a sensitive monitor for intraoperative myocardial ischaemia. Colour kinesis is a new technology for echocardiographic assessment of regional wall motion based on acoustic quantification. We have examined the feasibility and accuracy of quantitative segmental analysis of colour kinesis images to provide objective evaluation of systolic regional wall motion during the perioperative period using transoesophageal echocardiography (TOE). Two-dimensional echocardiograms were obtained in the transgastric short-axis and long-axis views in 60 patients with coronary artery disease undergoing noncardiac surgery. End-systolic colour overlays superimposed on the grey scale images were obtained with colour kinesis to colour encode left ventricular endocardial motion throughout systole. These colour-encoded images were divided into segments and compared with corresponding conventional two-dimensional images. Six hundred of a potential 720 left ventricular wall segments were of sufficient resolution for grading by experts; they diagnosed wall motion abnormalities in 61 of these segments by a conventional method. In comparing the conventional TOE method with colour kinesis, there were 60 true positives, 482 true negatives, 57 false positives and 1 false negative result. This yielded a sensitivity of 98%, specificity of 89%, positive predictive value of 51% and negative predictive value of 100%. Translational and rotational movement of the heart and papillary muscle interference were common problems accounting for false positive diagnoses. We conclude that colour kinesis provides a basis for objective and on-line evaluation of left ventricular regional wall motion which is a sensitive but non-specific method. It may be a useful aid for the less experienced because it can potentially direct the anaesthetist's attention towards specific segments.

Adult↗
PubMed1997

Effects of inhaled nitric oxide and extracorporeal membrane oxygenation on pulmonary hemodynamics and lymph flow in oleic acid lung injury in sheep.

OBJECTIVE: To compare the effects of inhaled nitric oxide (NO) and extracorporeal membrane oxygenation (ECMO) on oxygenation, hemodynamics, and lymphatic drainage in an oleic acid lung injury model in sheep. DESIGN: Prospective, randomized study. SETTING: Animal research laboratory. ANIMALS: Thirty female sheep, weighing 35 to 40 kg. INTERVENTIONS: Acute lung injury was induced by central venous injection of oleic acid (0.5 mL/kg body weight). A chronic lymph fistula had been prepared through a right thoracotomy 3 days before the experiment. Animals were assigned randomly to the NO group (n = 14) or the ECMO group (n = 16). When a lung injury score of > 2.5 was achieved, the animals were given NO in dosage increments of 2, 5, 10, 20, and 40 parts per million (ppm), or placed on ECMO with an FIO2 of 0.21 (ECMO-21) and then 1.0 (ECMO-100) at the oxygenator. Mechanical ventilator parameters were kept constant to isolate the effects of NO and ECMO on systemic and pulmonary hemodynamics, cardiac output, oxygenation parameters, lymph/plasma protein ratio, and lymph flow. Measurements and calculations were performed after 1 hr at each individual step of NO concentration or FIO2. MEASUREMENTS AND MAIN RESULTS: In the ECMO group, PVRI and MPAP did not change and were significantly different from the NO group. In the NO group, there was a dose-dependent decrease in venous admixture, maximal at 10 ppm NO and decreasing from 40 +/- 6% to 23 +/- 10% (p < .05). This decrease was significantly different from the ECMO group, where there was no change. There was a significant increase in PaO2/FIO2 in the NO group, maximal at 10 ppm NO (84 +/- 11 to 210 +/- 90, p < .05), but a greater increase in PaO2/FIO2 on ECMO-21 (81 +/- 14 to 265 +/- 63) and a further increase on ECMO-100 (398 +/- 100) (p < .05). The lymph/plasma protein ratio remained unchanged in both groups after induction of lung injury by oleic acid. However, lymph flow decreased by 11 +/- 6% in the NO group, whereas it increased by 14 +/- 17% in the ECMO group (p < .05). CONCLUSIONS: In an oleic acid-induced sheep model of acute lung injury, there were significant differences between the effects of NO and ECMO on acute pulmonary hypertension, hypoxemia, hypercarbia, and lymph flow. NO significantly decreases pulmonary hypertension, whereas pulmonary hemodynamics were not substantially affected by ECMO. Both interventions reversed hypoxemia, but ECMO did so to a greater degree, and only ECMO improved hypercarbia. Only NO decreased lymph flow, possibly as an effect of decreased microvascular filtration pressure. This study did not attempt to evaluate the impact of these interventions on ventilatory requirements, barotrauma, or outcome. However, this model suggests that NO therapy may moderate pulmonary hypertension and improve lymph flow in acute lung injury. Clinical studies are needed to assess whether NO therapy might be beneficial in treatment of severe acute lung injury in older children and adults.

Administration, Inhalation↗