Preoperative acute hypervolemic hemodilution with hydroxyethylstarch: an alternative to acute normovolemic hemodilution?

Acute normovolemic hemodilution (ANH) may help to reduce demand for homologous blood but requires extra time and apparatus. A more simple procedure is acute hypervolemic hemodilution (HHD), where hydroxyethylstarch is administered preoperatively without removal of blood. In a prospectively randomized study we compared ANH (preoperatively 15 mL/kg autologous blood removal and replacement with 15 mL/kg of hydroxyethylstarch with HHD (15 mL/kg of hydroxyethylstarch administered preoperatively) in 49 patients undergoing hip arthroplasty. To avoid excessive intravascular volume, we used the vasodilating effect of isoflurane. No significant differences were found between groups (ANH, n = 23; HHD, n = 26) for intraoperative blood loss (ANH versus HHD, median [minimum-maximum]); 545 [295-785] mL versus 520 [315-825] mL) and postoperative blood loss (730 [525-945] mL versus 780 [495-895] mL), postoperative hemoglobin, hemotocrit, platelet count or coagulation variables, and transfusion requirements (ANH 43% versus HHD 35% of patients received homologous blood) (P > 0.05). Heart rate did not change significantly in either group. In the ANH group mean arterial blood pressure (MAP) decreased after hemodilution (P < 0.05) while in the HHD group MAP did not change over time. Mean time required to perform ANH was 58 (46-62) min versus HHD 16 (12-19) min (P < 0.05). Costs for ANH were $63.60 USD and for HHD $32.75 USD (labor costs not included). In orthopedic patients undergoing hip replacement with a predicted blood loss of about 1000 mL, HHD seems to be a simple as well as time- and cost-saving alternative for ANH.

[Comparison of the effect of desflurane and isoflurane on neuromuscular blockage with vecuronium on geriatric patients]. / Vergleich der Wirkung von Desfluran und Isofluran auf die neuromuskuläre Blockade mit Vecuronium bei geriatrischen Patienten.

Volatile anaesthetics have long been known to intensify the effect of muscle relaxants. In this study we investigated the effects of desflurane and isoflurane on the neuromuscular blockade of vecuronium in geriatric patients. Fifty-two patients requiring elective surgery, aged > or = 65 years, with ASA status II - III were randomly assigned to receive general anaesthesia using desflurane (Des, n = 26) or isoflurane (Iso, n = 26). The effects of both inhalation anaesthetics on the neuromuscular blockade of vecuronium were compared by means of the duration of the depression of the first twitch (T1) of a train-of-four stimulation pattern. Succinylcholine 1.5 mg/kg was used to facilitate intubation, vecuronium 0.05 mg/kg was given as the succinylcholine wore off; additional doses of 0.01 mg/kg were given when T1 exceeded 25% of baseline amplitude. There were no significant differences in the patients' biometric data or the duration of anaesthesia. The median duration of action of the first vecuronium dose (0.05 mg/kg) was: Des: 18.3 (9.4-42.9) min and Iso: 15.9 (3.1-46.0) min. The number of repetitive dosages (0.01 mg/kg) was: Des: 5; 0-13 and Iso: 5; 0-14 and their median duration was: Des: 10.2 (3.6-37.6) min and Iso: 8.9 (2.1-43.9) min. There were no differences between the two groups (p > 0.05). These results suggest that augmentation of neuromuscular blockade by older fluorinated anesthetics is also exhibited by desflurane. The magnitude of this effect in geriatric patients is similar to that of isoflurane.

A lower solubility recommends the use of desflurane more than isoflurane, halothane, and enflurane under low-flow conditions.

STUDY OBJECTIVE: To determine whether the lower solubility of desflurane, over that of isoflurane, enflurane, and halothane, favors its use in low-flow anesthesia. DESIGN: Prospective clinical study. SETTING: Technical University of Munich. PATIENTS: 40 elderly (> or = 65 yrs), ASA physical status II and III surgical patients. INTERVENTIONS: All patients were anesthetized and received delivered concentrations (FD) of 4% desflurane, 1.5% isoflurane, 1.8% enflurane, or 0.9% halothane (n = 10 patients for each anesthetic) in a fresh gas inflow of 3 L/min (high-flow), until end-tidal target concentrations (FA) of 2% desflurane, 0.5% isoflurane, 0.6% enflurane, and 0.3% halothane were obtained. After 30 minutes, the inflow was decreased to 1 L/min (low-flow), and the FD and the inspired concentration (FI) were adjusted to maintain the target concentration. MEASUREMENTS AND MAIN RESULTS: The concentrations of the halogenated anesthetics, as well as nitrous oxide, oxygen (O2), and carbon dioxide, were measured in delivered gas at the common gas outlet and at the endotracheal tube connector. Transcutaneous O2 saturation, noninvasive blood pressure, and heart rate were also measured. During the first 30 minutes of high-flow administration, the target concentration was attained sooner with desflurane than with isoflurane, enflurane, or halothane (median levels: 4 min vs. 6 min, 8 min, or 10 min; p < 0.01). After the reduction of inflow to 1 L/min, FD had to be materially increased to maintain F1 and FA for the more soluble anesthetics, but not for desflurane. CONCLUSIONS: At low flows, FD provides a reasonable surrogate of F1 and FA for desflurane, but not for isoflurane, enflurane, or halothane. The rapid and predictable titrability of desflurane favors its safe use in low-flow technique.

[Comparison of the effectiveness of orally administered clorazepate dipotassium and nordiazepam on preoperative anxiety]. / Vergleich der Wirkung von oral appliziertem Dikaliumclorazepat und Nordiazepam auf die präoperative Angst.

Clorazepate dipotassium (Tranxilium) is one of the benzodiazepines which is widely used for oral premedication. After oral administration it is decarboxylated to its active metabolite nordiazepam (desmethyldiazepam). Nordiazepam is also commercially available in the form of drops (Tranxilium N). The aim of the present study was to compare the effect of these drugs on preoperative anxiety. One hundred and eight patients scheduled for orthopaedic surgery (ASA I-II) were studied. Medication was administered at 10 p.m. the evening before surgery (E) and at 7 a.m. on the morning of surgery (M). There were four groups: 1) E no medication; M clorazepate dipotassium; 2) E no medication; M nordiazepam; 3) E clorazepate dipotassium; M clorazepate dipotassium, 4) E clorazepate dipotassium; M nordiazepam. Dosages were: clorazepate dipotassium: body weight < 55 kg: 10 mg; body weight > 55 kg: 20 mg; nordiazepam: 1 gtt/kg; 5 mg = 24 gtt). Anxiety was measured by using the self-evaluating Erlangen anxiety scales, which measure both background and situational anxiety. Background anxiety (EAS-H) was evaluated during the evening before surgery; situational anxiety (EAS-S) was evaluated at the same time and also on the day of surgery before premedication and immediately before surgery. Pulse rate was measured each time the test was administered. There were no differences between the groups in sex, age, weight or the intervals between premedication and anaesthesia induction (p > 0.05). There were no statistically significant differences between the groups with respect to background anxiety. Situational anxiety did not significantly increase or decrease at any of the testing times, nor were there any differences between the groups (p > 0.05). Heart rate did not vary between the groups or with time (p > 0.05). In this group of patients undergoing elective orthopaedic procedures, clorazepate prevented a rise in anxiety in the immediate preoperative period. Since clorazepate is rapidly metabolized to nordiazepam when administered orally it might be predicted that the two drugs have similar properties. This hypothesis is confirmed by the results of the present study. We conclude that orally administered clorazepate dipotassium and nordiazepam have a similar effect on preoperative anxiety.

Experiences with the new inhalational agents in low-flow anesthesia and closed-circuit technique. Monitoring and technical equipment.

During recent years interest has focused on two completely fluorinated ethers, desflurane and sevoflurane, which promise a shorter induction of and emergence from anesthesia. Their physicochemical properties differ from isoflurane, enflurane and halothane, thus requiring new technical equipment and leading to a change in anesthesiological procedures. Low-flow anesthesia with desflurane can be performed, the technical equipment is available, especially vaporizers and gas analyzers. In contrast to anesthesia with isoflurane, enflurane and halothane, the initial high-flow wash-in period with desflurane can be shorter and the vaporizer setting can remain unchanged after fresh gas flow reduction. In order to administer desflurane and sevoflurane in closed circuit technique, new technical equipment is needed. Therefore, a computer controlled anesthesia machine was modified and the feedback mechanism to maintain the end-tidal anesthetic concentration was simulated. Isoflurane, desflurane or sevoflurane needed the same time for wash-in. Wash-out was slower with isoflurane; however, the technical equipment should be adapted to increase the elimination of the new agents. The consumption of desflurane and sevoflurane is effectively reduced by low-flow and closed circuit anesthesia.

[Anesthesia with the closed PhysioFlex system in comparison with conventional anesthesia procedures]. / Anästhesie mit dem geschlossenen System PhysioFlex im Vergleich zu konventionellen Anästhesieverfahren.

So far the anaesthetic technique of the closed circuit system in clinical routine could not be used adequately, because suitable mixtures of respiration gas components were not available and the maintenance of a sufficient gas volume in the anaesthetic circle system was not possible with the standard anaesthesia machines. The anaesthesia machine PhysioFlex was especially constructed to deliver anaesthetics in a closed circuit system. In this anaesthesia machine the concentrations of the respiratory gases and the gas volume in the circle system are automatically controlled by a feedback mechanism. We compared the closed circuit system (CC group), with a high-flow system (HF group) and a low-flow system (LF group)--each system on 10 patients. It was noted that the respiratory gas concentrations were adjustable and held constant to a greater degree precise in the circuit system. After the induction the desired inspiratory oxygen-concentration was reached within 5 minutes, the expiratory isoflurane-concentration within 10 minutes in the CC group and was maintained reliable. The consumption of liquid isoflurane was 12.9 ml/h in the HF group, 7.5 ml/h in the LF group and 5.3 ml/h in the CC group. The anaesthetic management was possible without any problems in all three groups.

[The determination of end-expiratory CO2 during resuscitation. Experience and results with the Normocap 200 (Fa. Datex) in preclinical resuscitation conditions]. / Wertigkeit der endexspiratorischen CO2-Messung bei der Reanimation. Erfahrungen und Ergebnisse mit dem Normocap 200 (Fa. Datex) unter präklinischen Reanimationsbedingungen.

Capnometers measure carbon dioxide (CO2) in inspired and expired air. Under physiological conditions end-tidal CO2 (peCO2) measurements closely reflect arterial pCO2 (paCO2). End-tidal CO2 concentration has been found to correlate with cardiac output in animal models and in clinical studies with cardiac arrest during cardiopulmonary resuscitation (CPR). In the present study in 23 cases of CPR end-tidal CO2 concentrations were registered during precordial compression with a transportable, battery-carried capnometer. In 7 cases of successful CPR mean concentrations of end-tidal CO2 were higher than in unsuccessful CPR (13 +/- 7 mmHg versus 8 +/- 6 mmHg). No statistical significance was found. In case of successful CPR there was a sudden rise in end-tidal CO2 up to 54 +/- 6 mmHg, indicating satisfactory spontaneous circulation. With capnometry it is possible to assess the efficacy of precordial compression during resuscitation and the return of spontaneous circulation in cardiopulmonary arrest.