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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
PubMed1999

Occupational exposure to sevoflurane during sedation of adult patients.

OBJECTIVES: In a field study we evaluated the workplace pollution occurring during conscious sedation with sevoflurane in adults. METHODS: Sevoflurane was given in 100% oxygen at a fresh gas flow rate of 3 l/min via a nasal mask. This was conducted in 25 patients scheduled for surgical procedures performed under regional anesthesia. Trace concentrations of sevoflurane were directly measured every minute in the breathing zone by means of a photoacoustic infrared spectrometer in an operating room with an air turnover of 20 changes/h. RESULTS: The mean sedation time was 49.6+/-20.4 min. The average vaporizer setting of the anesthesia machine was 1.63+/-0.6 vol%, resulting in a patient's mean end-tidal sevoflurane concentration of 0.78+/-0.2 vol%. The 8-h time-weighted average was calculated to be 0.58 ppm sevoflurane. CONCLUSIONS: The trace gas concentrations were low and comparable with values obtained under inhalation induction in adults and children. Although no occupational standard for sevoflurane is currently defined, the measured values are clearly under the standards recommended for enflurane (20 ppm) and isoflurane (10 ppm) by the European health authorities. We conclude that the new anesthesiologic method of conscious sedation with sevoflurane in adults using a nasal mask would not result in a violation of occupational standards, provided that the future value set for sevoflurane would be similar to those recommended for isoflurane or enflurane.

Adult↗
PubMed1999

The axillary vein central venous catheter in severely burned patients.

In severely burned patients the approach to the central vein is often difficult due to concomitant edema, but also due to the fact that the skin area, where commonly used approaches are performed, is burned as well, whereas the axillary region is often not involved. In order to perform an axillary approach to the central vein as an alternative to the commonly used approaches in patients, an anatomical dissection in fresh human cadavers was carried out. Considering the anatomical landmarks which were found during dissection of the axillary region, the axillary approach to the central vein was used in 35 patients in our intensive burn care unit with unaffected axillary skin. In three cases the only complication observed was an occasional puncture of the axillary artery without major hematoma. The infection rate of the catheters was similar to the commonly used puncture sites. This approach to the central venous line in severely burned patients can be recommended.

Adult↗
PubMed1999

Onset time, recovery duration, and drug cost with four different methods of inducing general anesthesia.

UNLABELLED: We compared two conventional induction techniques (thiopental and propofol), an inhaled induction with sevoflurane using a circle system, and a rebreathing method. Fentanyl 1 microg/kg was given to women undergoing 10- to 20-min procedures. Anesthesia was induced (n = 20 each) with one of the following: 1) sevoflurane and N2O from a rebreathing bag (Sevo/Bag). A 5-L bag was prefilled with a mixture of sevoflurane 7% and N2O 60% in oxygen. The bag was connected between the normal circle system, separated by a spring-loaded valve; 2) sevoflurane 8% and N2O 60% from a circle system on a conventional anesthesia machine with a total fresh gas flow of 6 L/min (Sevo/Circle); 3) propofol 3 mg/kg as an i.v. bolus; 4) thiopental sodium 5 mg/kg as an i.v. bolus. Postoperative nausea and vomiting was treated with ondansetron. Induction times were comparable with each method. Recovery duration was shortest with sevoflurane, intermediate with propofol, and longest with thiopental. Induction drug costs were lowest with Sevo/Bag and thiopental, intermediate with Sevo/Circle, and highest with propofol. However, sevoflurane (by either method) caused considerable nausea and vomiting that required treatment. Consequently, total drug cost was least with thiopental, intermediate with Sevo/Bag and propofol, and greatest with Sevo/Circle. Thus, no single technique was clearly superior. IMPLICATIONS: Anesthetic induction techniques influence awakening time, recovery duration, and drug costs. We tested two i.v. methods and two inhaled techniques. However, none of the four tested methods was clearly superior to the others.

Adult↗
PubMed1999

Use of abciximab-modified thrombelastography in patients undergoing cardiac surgery.

UNLABELLED: Thrombelastography (TEG) is a reliable coagulation monitoring system that can guide blood product transfusion in cardiac surgery. The maximum amplitude (MA) of TEG measures clot strength, which is dependent on both fibrinogen level and platelet function. Inhibition of platelet function with abciximab-fab is suggested to permit quantitative assessment of the contribution of fibrinogen to clot strength. We hypothesized that abciximab-modified TEG permits prediction of plasma fibrinogen levels and that the difference of standard MA and abciximab-modified MA (deltaMA) is a correlate for platelet function. We correlated abciximab-modified MA with plasma fibrinogen levels and deltaMA with platelet count in patients undergoing coronary revascularization. Correlation between plasma fibrinogen levels and abciximab-modified MA was significant (adjusted r2: 0.8; P < 0.0001). Correlation of deltaMA with platelet count was not significant when calculated in millimeters (adjusted r2: 0.04; P = 0.73). However, when deltaMA was calculated in dynes per square centimeter (deltaGMA), it correlated significantly with platelet count (adjusted r2: 0.51; P < 0.0001). We conclude that abciximab-modified TEG may therefore help to discriminate between hypofibrinogenemia and platelet dysfunction as a cause of decreased MA. IMPLICATIONS: We examined the use of abciximab-modified thrombelastography in patients undergoing cardiac surgery. Modification of thrombelastography with abciximab-fab allows prediction of fibrinogen levels, despite coagulation altered by cardiac surgery. The difference of standard maximum amplitude and abciximab-modified maximum amplitude correlates with platelet function when expressed in dynes per square centimeter.

Abciximab↗
PubMed1999

Postanaesthetic considerations and complications after ambulatory anaesthesia.

Ambulatory or day-case surgery is being employed to an ever-increasing extent. Although it has many advantages, it is not suited to the needs of every patient. For example, patients who live alone, particularly the elderly, might well not be able to care for themselves adequately after such surgery and are probably at a higher risk of developing complications, including infections. Furthermore, pain treatment may be insufficient, as a consequence of which recovery can be prolonged and the resumption of normal daily activities might be delayed. Nausea, dizziness and vomiting can also prolong recovery and need to be adequately treated after ambulatory surgery. Therefore, the often cited cost effectiveness of ambulatory surgery is questionable if complications cannot be prevented or treated effectively.

Journal Article↗
PubMed1998

[SHFJV. Jet-adapter for application of superimposed high-frequency jet ventilation (SHFJV) via a tube in intensive care: a new technique].

UNLABELLED: Despite advances and technical developments in the area of intensive care medicine it has not been possible to lower the mortality of patients with pulmonary insufficiency. Therefore, alternative ventilation strategies have been developed and applied. One of these ventilation techniques is superimposed high-frequency jet ventilation (SHFJV). For optimal application of SHFJV we designed a special jet-adapter. METHODS: This jet-adapter made of plastic consists of a T-piece and four central, small-bore cannulas and can be connected to any commercially available endotracheal tube. Therefore, it does not require reintubation with an endotracheal jet tube when beginning SHFJV. The simultaneous high-frequency and low-frequency jet ventilation is performed over two jet-nozzles that have been designed according to optimal flow dynamic measurements. Two further cannulas are used for continuous airway pressure monitoring and humidification of the applied gases. A pre-warmed and humidified bias flow with exactly defined oxygen concentration is led through the cross-part of the T-piece for gas entrainment. Additionally, the cross-part contains a port that can be opened for endotracheal suctioning or bronchoscopy and makes disconnection of the jet adapter from the endotracheal tube for either purpose unnecessary. CONCLUSION: The jet adapter can be used: (1) to apply SHFJV; (2) to measure airway pressures continuously; (3) to humidify and warm inspired gases; (4) to administer medications or add nitrous oxide by the inspiratory route, enabling combination with new therapeutic possibilities in the management of patients with severe ARDS.

Anesthesia, Inhalation↗
PubMed1998

Quantification of mitral regurgitant flow using proximal isovelocity surface area method: a transesophageal echocardiography perioperative study.

OBJECTIVE: To investigate the usefulness of the color Doppler proximal isovelocity surface area (PISA) method, compared with the jet area method, in determining the severity of mitral regurgitation in the perioperative period using angiographic grading as a reference method. DESIGN: Randomized, controlled prospective study. SETTING: Single university hospital. METHODS: Thirty-three patients with native mitral valve insufficiency of different grade were studied. The color jet area in the left atrium, as well as PISA regurgitant stroke volume (RSV), were established. PISA RSV was calculated using a formula derived from previous in vitro and human studies: RSV = 2 pi r2 x v x RTVI/RPFV x (inlet angle/180 degrees), in which r is the radial distance between the first aliasing contour (red/blue interface); v is the aliasing velocity that is read from the color bar; RTVI is the time-velocity integral of the regurgitant jet from the continuous wave Doppler recordings; and RPFV is the corresponding peak flow velocity of the continuous wave regurgitant jet. RESULTS: The rank correlation coefficient between the angiographic grade of mitral regurgitation and the PISA method was rsp = 0.89 (p < 0.0001), and for the jet area was rsp = 0.44 (p < 0.01). There was close concordance between angiographic and PISA measurements of RSV (r = 0.92, p < 0.0001). Further, scatterplot of difference between the two measurements plotted against the mean of measurements showed good agreement. CONCLUSIONS: It was concluded that in patients with mitral regurgitation during the perioperative period, the PISA method is more suitable than the jet area method to determine the severity of mitral regurgitation, and only it provides a reliable technique to differentiate between grade I-II mitral regurgitation in patients with eccentric regurgitant jet and grade III-IV mitral regurgitation in patients with jet size that is bigger than transesophageal echocardiography left atrial size.

Adult↗
PubMed1998

The influence of transoesophageal echocardiography on intra-operative decision making. A European multicentre study. European Perioperative TOE Research Group.

The role of transoesophageal echocardiography (TOE) in anaesthesia remains controversial because it is a rapidly evolving technique with few proven benefits and considerable cost. Recently, the Society of Cardiovascular Anaesthesiologists has published practice guidelines for the use of peri-operative TOE. To determine the current role of transoesophageal echocardiography and the relative impact of category-based transoesophageal echocardiographic indications the present study investigated its use in seven Western European countries. The study sample was taken from a prospective cohort of 224 patients with acute or chronic haemodynamic disturbances or at risk of myocardial ischaemia. All patients were monitored with two-lead electrocardiography and radial and pulmonary artery catheters, as well as biplane or multiplane transoesophageal echocardiography. A total of 2232 clinical interventions were made in these patients. The most frequently observed intervention was the administration of a fluid bolus (45% of all interventions). Overall, transoesophageal echocardiography was the most important guiding factor in 560 (25%) interventions. It was the most important monitor in guiding the following therapeutic interventions: anti-ischaemic therapy--207 of 372 interventions (56%); fluid administration--275 of 996 (28%) interventions; vasopressor or inotrope administration--56 of 316 (16%) interventions; vasodilator therapy--six of 142 (4%) interventions and depth of anaesthesia--four of 211 (2%) interventions. We found that transoesophageal echocardiography is frequently influential in guiding clinical decision making and is used most frequently for category II indications but category I indications were associated with more frequent change in management.

Adult↗
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↗