D. Kietzmann

Heat and moisture exchangers for humidifying the inspired air of intubated patients in intensive care medicine. An investigation of humidification properties of heat and moisture exchangers under clinical conditions

Zusammenfassung. Die Befeuchtungsleistung unterschiedlicher Wärme- und Feuchtigkeitstauscher (DAR Hygrobac, Gibeck HumidVent 2P, Pall BB 22-15 T und BB 100) zur Klimatisierung der Atemgase wurde im beatmeten Lungenmodell unter standardisierten Bedingungen sowie bei 25 intubierten Patienten untersucht. Mit Hilfe eines neuartigen, hochauflösenden Feuchtesensors konnte nachgewiesen werden, daß die Klimatisierungsleistung von Wärme- und Feuchtigkeitstauschern (HME, Heat and Moisture Exchanger) unter Nichtrückatmungsbedingungen nicht nur durch Messung der inspiratorischen Feuchte direkt am Tubus bestimmt werden kann, sondern einfacher und genauer durch Messung des exspiratorischen Wassergehalts in der Abluft des Respirators. Diese Meßmethodik ist nicht-invasiv und erlaubt jederzeit die Bestimmung der Befeuchtungsleistung des verwendeten HME in der spezifischen Beatmungssituation. Anders als bei der schwierigen Interpretation der tubusnah ermittelten Feuchteparameter ist durch die Bestimmung des Wassergehalts der Exspirationsluft am Respiratorauslaß eine eindeutige Beurteilung der Befeuchtungsleistung des HME durch Vergleich mit den physiologischen Wärme- und Feuchtigkeitsverhältnissen in den Atemwegen möglich. Durch Beschichtung des Innenmaterials mit hygroskopischen Substanzen kann die Wasserbindungskapazität von HME soweit erhöht werden, daß– gemessen an physiologischen Gegebenheiten – adäquate Befeuchtungsleistungen erreicht werden können. HME stellen damit prinzipiell eine gute Alternative zu aktiven Befeuchtungssystemen dar.

Efficiency of warming devices in extubated postoperative patients

Zusammenfassung. Die vorliegende Untersuchung vergleicht die Effektivität radiativer und konvektiver Wärmezufuhr an wachen, extubierten Patienten. 35 Patienten, die nach laparoskopischen Operationen eine Harnblasentemperatur <36 °C erreicht hatten, wurden randomisiert entweder unter einem deckenmontierten Strahler (Gr. R, n=11), unter einem Warmluftgebläse (Gr. L, n=12) oder einer Baumwollsteppdecke (Gr. K, n=12) behandelt. Die zentralen Erwärmungsgeschwindigkeiten zeigten im Median (Min↔Max) geringe, aber nicht signifikante Unterschiede von 0,81 (0,41↔1,32) °C/h gegenueber 0,76/0,40↔1,07) und 0,70 (0,37↔1,13) °C/h in den Gruppen R, L und K. Ein signifikanter Unterschied ergab sich für die Medianwerte der maximalen, während der Untersuchungsperiode gemessenen VO2 für beide Therapiegruppen gegenüber der Kontrollgruppe. Diese ergaben 4,39 (3,74↔6,19) ml/kg/min, 4,30 (3,46↔6,67) ml/kg/min und 5,92 (3,79↔10,64) ml/kg/min für die Gr. R, L und K. Eine Effektivität der Wärmetherapien wird erst in dem Quotienten von Zunahme an Körperwärmemenge/körpereigene Wärmeproduktion deutlich, der eine über 20% größere Konservierung der körpereigenen Wärmeproduktion der Therapiegruppen im Vergleich zur Kontrollgruppe zeigt. Bei wachen postoperativen Patienten scheint mit keinem der beiden Therapieverfahren eine wesentlich schnellere Aufwärmung als mit einer Baumwollsteppdecke möglich. Zur Verkürzung der Aufwärmzeit erscheint bei geplanter Extubation unter diesen Umständen eine Optimierung intraoperativer Wärmeprotektion sinnvoller.Abstract. Hypothermia (Tcore<36 °C) can be observed in 60% – 80% of all admissions to the post-anaesthetic recovery unit. Effective warming devices may accelerate rewarming, improve patient comfort, and suppress shivering thermogenesis. This study was designed to compare the efficiency of warming devices in extubated postoperative patients and their effect on postoperative oxygen uptake (V˙O2). Methods. Thirty-five ASA I and II patients after laparoscopic hernioplastic repair with core temperatures <36 °C were randomly assigned to either postoperative nursing under a radiant heater (group R, n=11, Aragona Thermal Ceilings CTC X, Aragona Medical AB, Täby, Sweden), a forced air system (group L, n=12, Bair Hugger, Augustine Medical Inc., Eden Prairie, Minnesota, USA), or a normal cotton hospital blanket (group K, n=12). Anaesthesia was conducted totally intravenously with propofol, alfentanil, and vecuronium. Mean body temperature and total body heat were calculated from urinary bladder temperature and four subcutaneous temperature measurements. The rate of thermogenesis was calculated from continuous measurement of V˙O2 (Datex Deltatrac Metabolic Monitor, Datex Instrumentarium Corp., Helsinki, Finland). Heat balance was derived from the increase in total body heat minus body heat production. Heart rate and noninvasive blood pressure were measured by the Cardiocap (Datex Instrumentarium Corp., Helsinki, Finland). All data were transferred to an IBM-compatible computer at 60-s intervals. Measurements were stopped when core temperature reached 37 °C. The rate of change was calculated for each variable for the period 15 min after the beginning of rewarming to attainment of 37 °C. Data are presented as median, minima, and maxima (min↔max); the Mann-Whitney U test was used to test for significance of group differences. Results. All groups were comparable for body weight, height, age, and amount of postoperative infusions. Temperatures at admission were 35.2 (33.4↔35.9), 34.7 (34.3↔35.8), and 35.4 (34.3↔35.9) °C for groups R, B, and K, respectively. No significant differences in the rate of central rewarming could be found for these groups with 0.81 (0.41↔1.32), 0.76 (0.40↔1.07), and 0.70 (0.37↔1.13) °C/h (Fig. 1). The mean V˙O2 of 3.41 (3.07↔3.73), 3.55 (2.78↔4.06), and 3.79 (2.51↔7.00) ml/kg/min also did not differ significantly (Fig. 3). Significant differences between groups R and B [4.39 (3.74↔6.19) and 4.30 (3.46↔6.67) ml/kg/min] and K [5.92 (3.79↔10.64) ml/kg/min] were found for V˙O2 maxima during the course of investigation (Fig. 4). The heat balance revealed significant differences among treatment and control groups with −88 (−266↔+30), −41 (−212↔+12), and −191 (−265↔−86) kJ/h for groups R, B, and K. We additionally calculated the heat balance as a quotient, which showed 0.70 (0.22↔1.07), 0.86 (0.44↔1.04), and 0.49 (0.31↔0.79) for groups R, B, and K (Fig. 4). The mean rate-pressure product of all groups did not differ significantly during the period of investigation. Conclusions. Neither external heat supply by radiant heat nor by a forced warm air system significantly reduced rewarming time in extubated, awake patients. As measured by heat balance, both active treatments saved about 20% more body heat production than in the control group. Continuing peripheral vasoconstriction may be the reason for the low efficiency of heat transfer. Thermal treatment did reduce the peak load (max. V˙O2) on the oxygen transport systems, though shivering was treated by pethidine if it occurred. External rewarming did not reduce the average load (mean V˙O2). Thus, concerning the goal of accelerating rewarming, it appears more rational to prevent intraoperative heat loss. For a comparison of efficiency of different warming devices, postoperative extubated patients do not appear to be an ideal model for study.

Vergleich einer sufentanil-Propofol-Anästhesie mit Fentanyl-Propofol bei grossen abdominalchirurgischen Eingriffen

ZusammenfassungDie totale intravenöse Anästhesie (TIVA) mit Sufentanil-Propofol wurde in einer kontrollierten, randomisierten Doppelblindstudie erstmals im Vergleich zu Fentanyl-Propofol bei ASA I-II-Patienten untersucht, die sich großen, elektiven, abdominalchirurgischen Eingriffen unterziehen mußten. Zielparameter waren Hämodynamik (Herzfrequenz, arterielle, zentralvenöse und pulmonalarterielle Drücke, Herzindex), arterielle Katecholaminkonzentrationen sowie der Median der Amplitudenfrequenzspektren des EEG. Zwischen den beiden TIVA-Verfahren wurden keine signifikanten Unterschiede beobachtet. Nach Narkoseeinleitung fielen Herzfrequenz, arterieller Druck und Herzindex ab; erst nach Eröffnung des Peritoneums wurden die Ausgangswerte wieder erreicht, aber nicht überschritten. Die Plasmakonzentrationen von Adrenalin und Noradrenalin fielen bis zur analytischen Nachweisgrenze ab und stiegen im Mittel nie auf Werte oberhalb des physiologischen Konzentrationsbereichs. Die Hauptaktivität im EEG zeigte sich während der gesamten Narkose im Delta- und Thetabereich. Die TIVA mit Sufentanil-Propofol oder Fentanyl-Propofol zeichnete sich durch eine nahezu vollständige Unterdrückung der sympathoadrenalen Streßantwort und der daraus folgenden Hypertensionen und Tachykardien aus.AbstractMajor abdominal surgery often leads to a marked sympathoadrenal stress response with high concentrations of plasma catecholamines, hypertension, and tachycardia. We compared the effects of sufentanil-propofol with fentanyl-propofol anaesthesia in a controlled, randomised, double-blind study of 18 ASA I–II patients aged 23–64 years undergoing major abdominal surgery. Study parameters were haemodynamics (heart rate [HR], arterial [ABP], central venous, and pulmonary arterial pressures, cardiac index [CI]), arterial catecholamine concentrations, and the median frequency of the electroencephalogram (EEG) power spectrum. Methods. After premedication with flunitrazepam 1–2 mg, promethazine 25–50 mg, and piritramide 7.5–15 mg, a five-lead electrocardiograph and a Lifescan brain activity monitor were attached and indwelling cannulae were inserted into the radial artery and two forearm veins. A thermodilution catheter was placed in the pulmonary artery via the right internal jugular vein. Anaesthesia was induced with either fentanyl 7 μg/kg followed by 5 μg/kg·h or sufentanil 1 μg/kg followed by 0.7 μg/kg·h up to the end of surgery. Additional boli of the opioids were given according to set criteria, resulting in an average consumption of 9.03 μg/kg·h fentanyl or 1.22 μg/kg·h sufentanil. Propofol 2 mg/kg was given followed by 6 μg/kg·h up to the end of surgery. Relaxation was obtained with pancuronium 0.025–0.05 mg/kg before intubation and every 60–120 min. Measurements were performed before and after induction, after tracheal intubation, before and after skin incision, after opening of the peritoneum, and at the end of surgery. Results. No significant differences were observed between the two groups with regard to the study parameters. The duration of surgery and blood loss were similar in both groups, as were patient characteristics. After induction 2 patients in each group developed thoracic rigidity, which was reversible after muscle relaxation. HR, ABP, and CI decreased significantly before skin incision; after surgical stimulation the baseline values were again reached, but not exceeded. No patient developed tachycardia (>100/min) or hypertension (>15% higher than baseline pressure) for longer than 10 min during the study period until the end of surgery. The plasma concentrations of epinephrine and norepinephrine decreased significantly during anaesthesia, and under maximum surgical stimulation did not increase higher than the physiological baseline concentrations. The EEG median frequencies decreased after induction, and during the entire anaesthetic period the main activity was in the delta and theta frequency bands. Conclusions. With both regimens, the sympathoadrenal stress response to major abdominal surgery was nearly completely suppressed, resulting in stable haemodynamics during the operations. Sufentanil and fentanyl were equally well suited as analgesic components of total IV anaesthesia with propofol.

Sensitive Determination of Piritramide in Human Plasma by High-Performance Liquid Chromatography

Abstract A selective and sensitive method for the determination of piritramide in human plasma is described. After addition of 50 μl of 2 M ammonia and 20 μl of aqueous promethazine solution (100 ng/10 μ1) as an internal standard, 1 ml of plasma was extracted with 5 ml of toluene (extraction efficiency: 93.9 × 2.6%; mean × S. D.; n = 5). HPLC was performed with a phenyl hypersil NC-04 column, particle size 5 μm, 250 × 4 mm I. D.; mobile phase: 8 parts of acetonitrile and 2 parts of 10 mM potassium phosphate buffer (pH 3. 3). The flow rate was set to 2 ml/min and the column temperature was 22°C. The assay was linear in a concentration range of 3.75 − 3000 ng/ml (r = 0.999), with a lower limit of detection of 3 ng/ml. The precision was determined using spiked plasma samples (15 ng/ml; 300 ng/ml), with coefficients of variation of 6.1 and 5.9% (intraday; n = 5) and 6.5 and 0.2% (interday; n = 3). In the range of 5.6 − 1500 ng/ml, the accuracy of the assay was 2.82%. The method was used for the determination ...