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Description / Table of Contents: Abstract. In a controlled prospective randomized study, defibrillation by emergency medical technicians (EMTs) was compared with the current standard of care in Germany (basic life support by EMTs and defibrillation by emergency physicians only) in order to answer the following questions: 1. Does EMT defibrillation improve the survival rate and long-term prognosis of patients in ventricular fibrillation as compared to the current German standards in resuscitation (basic life support by EMTs and defibrillation by emergency physicians)? 2. Are the prerequisites for the use of semiautomatic defibrillators fulfilled in the emergency medical systems (EMS) of the participating centers? Methods. The study phase includes randomization of 121 adult patients with witnessed cardiac arrest and ventricular fibrillation (VF) as first ECG rhythm. Prior to the onset of the study, all EMTs of the participating EMS systems were retrained in basic life support (BLS) measures. In each center, randomly assessed EMT-Ds (EMTs trained in Defibrillation) were trained to use semiautomatic defibrillators. With the help of one-line tape recording, the time intervals during resuscitation and treatment steps were evaluated. Successfully resuscitated patients were followed up with the help of the Glascow Coma Scale and the Pittsburgh Cerebral and Overall Performance Categories. Results. From 1 February 1991 until 28 June 1992, 159 patients with VF were randomized. In 121 cases, collapse was witnessed. 25% (14/57) of the patients receiving defibrillation by EMT-Ds (study group=S) were discharged from the hospital alive. In the control group, 52 patients were defibrillated by emergency physicians, following BLS by EMTs [control group 1=C1; discharged: 29% (15/52)]. Fifty patients received BLS and advanced cardiac life support (ACLS) by the emergency physicians crews [control group 2=C2; discharged 18% (9/50)]. In the study group, the median time interval from collapse of the patient until initiation of BLS measures was 7.7 min, 7 min in C1 and 8 min in C2. ACLS measures were initiated significantly earlier (P〈0.05) in the control groups, as compared to the study group [S: 13 min, C1: 11 min; C2: 10.3 min]. Sixty-seven percent (30/45) of the study patients and 46% (36/76) of the control patients were defibrillated within 12 min. Study patients were defibrillated earlier (P〈0.05) (S: 9.9 min; C1: 12.2 min; C2: 12.75 min); return of spontaneous circulation (ROSC) was achieved earlier (P〈0.05) in the study group [S: 14 min; C1: 19 min; C2: 18.2 min] and the number of patients in the study group requiring no epinephrine during resuscitation was higher (P〈0.01) than in the control groups [S: 35.3% (12/34); C1: 10% (4/40); C2: 10.5% (4/38)]. Furthermore, the total amount of epinephrine [mean (±standard error)] administered in the study group [S: 2.35 (±0.49) mg; C1: 6.71 (±0.98) mg; C2: 7.71 (±1.31) mg] was significantly lower (P〈0.05). No significant differences in neurological long-term prognosis were found for the groups investigated. Conclusion. Neither the initial survival rate the number of patients discharged alive, nor the neurological long-term prognosis was significantly different for any of the groups investigated. Because of apparent differences in indirect prognostic parameters (time interval until ROSC, number of patients requiring no epinephrine) and because of the fact that the time interval to the first defibrillation was reduced by EMT defibrillation, EMT-Ds may perform defibrillation if: (a) they reach the patient before the emergency physician and (b) if they are trained intensively and supervised continuously. In order to increase the efficiency of defibrillation by EMT-Ds, far-reaching changes in our EMS are mandatory: (a) a reduction in the time interval from collapse until initiation of BCLS measures by intensifying layperson CPR training; (b) an increase in the number of emergency units equipped with semiautomatic defibrillators; (c) the consistent implementation of a tiered EMS.

Description / Table of Contents: Abstract. Automated measurements of respiratory gas exchange recently became available for the determination of oxygen uptake (V˙O2) in critically ill patients. Whereas these metabolic gas monitoring systems (MBM) are assumed to measure total body V˙O2, the reversed Fick method in principle excludes intrapulmonary V˙O2. Previous clinical reports comparing V˙O2 measured by the reversed Fick principle (V˙O2  Fick) with V˙O2 measured by MBM (V˙O2  MBM) found that V˙O2  MBM was significantly greater than V˙O2  Fick. It was suggested that these differences between methods represent V˙O2 of pulmonary and bronchial tissue, as intrapulmonary V˙O2 had been estimated to account for 15% of total body V˙O2 in dogs with experimental pneumonia. The objective of this study was to compare V˙O2  Fick with V˙O2  MBM in patients with and without pneumonia and to assess the reproducibility of both methods in critically ill patients. Method. With institutional approval nine critically ill patients with acute pneumonia were studied under controlled mechanical ventilation. The diagnosis of pneumonia was based on respective changes of chest X-rays, body temperature 〉38 °C, and WBC counts 〉12,000/mm3. Inspiratory oxygen fractions (FIO2) ranged from 0.3 to 0.6; all patients routinely received opioids and hypnotics. Complete muscle relaxation was achieved during the periods of measurement to avoid sudden changes in V˙O2 due to shivering or involuntary movements. Arterial and pulmonary-arterial blood samples were drawn simultaneously after aspiration of the sevenfold catheter dead space. Measurements of haemoglobin concentration (Hb), fractional oxygen saturation (SO2), and O2 partial pressure (PO2) were performed by use of a calibrated haemoximeter and blood gas analyser, respectively; 2×5 thermodilution measurements of cardiac output (CO) were spread randomly over the respiratory cycle for each determination of V˙O2  Fick. To minimise systematic errors of CO measurements, the CO computer was calibrated in an extracorporeal model using an electromagnetic flowmeter. Calculations of V˙O2  Fick were based on an oxygen binding capacity of 1.39 ml/g Hb. Simultaneous measurements of V˙O2  MBM were obtained by use of a Datex Deltatrac MBM that had been validated in vitro with a gas dilution model of respiratory gas exchange. Calibration of the MBM was performed prior to each measurement. Gas supply of the respirator was provided by an external high-precision mixing device to reduce errors in V˙O2 measurements that may arise from short-term oscillations in FIO2. All patients with pneumonia were studied on three consecutive days; thus, measurements from 27 days could be analysed. On each day two sets of measurements were performed at an interval of 60 min to assess the reproducibility of differences between methods. During each set of measurements duplicate blood samples were drawn twice, before and after thermodilution measurements of CO, to evaluate the short-term repeatability of V˙O2  Fick. The beginning and the end of each set of measurements were marked in the computer record of the MBM to assess the respective repeatability of V˙O2  MBM. Fifty control measurements were performed in ten patients undergoing major neurosurgical procedures. None of these patients exhibited signs of pulmonary infection. Except for the number of repeated measures, all V˙O2 measurements were obtained in the same way as in the study group. Descriptive statistical analysis was performed according to Bland and Altman; comparisons between methods were done by multivariate analysis of variance for repeated measures. Results. Neither in the study group nor in the control group could a significant difference between methods be demonstrated. In patients with pneumonia the mean difference between methods (V˙O2  Fick−V˙O2  MBM) was 15.2 ml/min (4.2%); the double standard deviation of differences (2 SD) was 59.2 ml/min (19.2%). Control patients exhibited a mean difference of 7.2 ml/min (3.1%); 2 SD was 41.1 ml/min (20.4%). Duplicate determinations of V˙O2  Fick and V˙O2  MBM within one set of measurements showed a repeatability coefficient (2 SD of differences between repeated measures) of 43.8 ml/min (13.2%) and 15.3 ml/min (5.1%), respectively. The large variation of duplicate measurements of V˙O2  Fick was caused rather by the variability of arteriovenous O2 content determinations than by the variability of CO measurements. Discussion. These results are in contrast to previous method comparison studies, which suggested that in infected lungs V˙O2 of pulmonary and bronchial tissue represents up to 15% of total body V˙O2. Since the mean differences between V˙O2  Fick and V˙O2  MBM did not differ between the two groups of patients, pulmonary infection did not seem to cause a considerable increase in intrapulmonary V˙O2. A minor effect of intrapulmonary V˙O2 on differences between methods cannot be excluded because of the variability of data. The poor repeatability of V˙O2  Fick measurements, however, seems to limit the use of method comparison studies for estimation of intrapulmonary V˙O2.

Description / Table of Contents: Abstract. Thermodilution measurements of cardiac output (CO) by means of Swan-Ganz catheters, in a strict sense, represent pulmonary arterial blood flow (PBF). In principle, this is also true in the presence of intracardiac left-to-right shunts due to atrial or ventricular septal defects. However, early recirculation of indicator may give rise to serious methodological problems in these cases. We sought to determine the influence of intracardiac left-to-right shunts on different devices for thermodilution measurements of CO using an extracorporeal flow model. Methods. Blood flow was regulated by means of a centrifugal pump that at the same time enabled complete mixing of the indicator after injection (Fig. 1). Pulmonary and systemic parts of the circulation were simulated using two membrane oxygenators and a systemic-venous reservoir to delay systemic recirculation of indicator. Control measurements of PBF (Qp) and systemic (Qs) blood flow were performed by calibrated electromagnetic flow-meters (EMF). Blood temperature was kept constant using a heat exchanger without altering the indicator mass balance in the pulmonary circulation. Left-to-right shunt was varied at different systemic flow levels applying a Qp:Qs ratio ranging from 1:1 to 2.5:1. Thermodilution measurements of PBF were performed using two different thermodilution catheters that were connected to commercially available CO computers. Additionally, thermodilution curves were recorded on a microcomputer and analysed with custom-made software that enabled iterative regression analyses of the initial decay to determine that part of the downslope that best fits a monoexponentially declining function. Extrapolation of the thermodilution curve was then based on the respective curve segment in order to eliminate indicator recirculation due to shunt flow. Results. At moderate left-to-right shunts (Qp:Qs〈2:1) all thermodilution measurements showed close agreement with control measurements. At higher shunt flows (Qp:Qs≥2:1), however, conventional extrapolation procedures of CO computers considerably underestimated PBF (Fig. 2). This was particularly true when a slow-response thermistor catheter was used (Fig. 3). The reason for this underestimation of Qp was an overestimation of the area under curve because of inadequate mathematical elimination of indicator recirculation by standard truncation methods (Fig. 4). However, curve-alert messages of the commercially implemented software did not occur. A high level of agreement could be consistently obtained using a fast-response thermistor together with individual definition of extrapolation limits according to logarithmic regression analyses. Discussion and conclusion. Under varying levels of left-to-right shunt, both the reponse time of thermodilution catheters and the algorithms for calculation of flow considerably influenced the validity of thermodilution measurements of PBF in an extracorporeal flow model. The use of computer-based regression analyses to define the optimal segment for monoexponential extrapolation could effectively eliminate indicator recirculation from the initial portion of the declining thermodilution curve and showed the closest agreement with EMF measurements of Qp. The quality of thermodilution curves with respect to recirculation peaks in the flow model was slightly better than in clinical routine. Nevertheless, the clinical applicability of the modified extrapolation algorithm could be illustrated during pulmonary thermodilution measurements in an exemplary patient with a ventricular septal defect (Fig. 5). PBF at extremely high shunt ratios, however, cannot be assessed by monoexponential extrapolation in principle (Fig. 6). Insufficient elimination of indicator recirculation resulted in flow values that closely resembled systemic rather than PBF. This finding is in accordance with a mathematical analysis of the underlying Steward-Hamilton equation if an infinite number of recirculations would be included in the area under curve.

Description / Table of Contents: Abstract Heated humidifiers (HH) as well as heat and moisture exchangers (HME) are commonly used in intubated patients as air-conditioning devices to raise the moisture content of the air, thus preventing mucosal damage and heat loss resulting from ventilation with dry inspired gases. In contrary to HME, HH are able to add heat and moisture to the inspired air in surplus, which is often stressed as an advantage in warming hypothermic patients or reducing major heat losses, e.g., during long operations. The impact of air conditioning on the energy balance of man was calculated comparing HME and HH. Methods. The efficiency of a HME (Medisize Hygrovent) and a HH (Fisher & Paykel MR 730) was evaluated in a mechanically ventilated lung model simulating the physiological heat and humidity conditions of the upper airways. The gas flow from the central supply was dry; the model temperature varied between 32 and 40 °C. By using a HH in the inspiratory limb, a circle system was simulated with water-saturated inspired air at room temperature. The water content of the ventilated air was determined at the tracheal tube connection using a fast, high-resolution humidity meter and was compared with the moisture return of the HME. The energy balance was calculated according to thermodynamic laws. Results. Both HME and HH were able to create physiological heat and humidity conditions in the airways. With the normothermic patient model, the moisture return of the HME was equal to that of the HH set at 34 °C. Increasing the heating temperature resulted only in reduced water loss from the lung; heat and water input in the normothermic model was not possible. This was only effective with almost negligible amounts under hypothermic patient model conditions. Discussion. The water content in the inspired and expired air is the most important parameter for estimating pulmonary heat loss in mechanically ventilated patients. In adults (minute volume ∼7 1/min) the main fraction of pulmonary heat loss results from water evaporation from the airways (∼6 kcal/h), whereas the heat loss due to convection is negligible (∼1.2 kcal/h). In intubated patients ventilated with dry air, the heat loss increases to ∼8 kcal/h due to greater water evaporation from the airways. Both HME and HH are able to reduce the pulmonary heat loss to 1–2 kcal/h. In normothermic as well as hypothermic patients, HH do not offer significant advantages in heat balance compared to effective HME. In conclusion, air conditioning in intubated patients is neither a powerful too for maintaining body temperature during long-lasting anaesthesia nor a sufficient method of warming hypothermic patients in intensive care units.

Description / Table of Contents: Abstract. Total intravenous anaesthesia (TIVA) using a combination of a hypnotic and an analgesic agent is gaining increasing popularity as an alternative to balanced anaesthesia with volatile anaesthetics for abdominal surgery. Among the required characteristics of the drugs used in this technique are a good correlation between dose, plasma concentrations, and effect as well as rapid elimination from the circulation, allowing close control of anaesthetic depth. Two hypnotic drugs with similar pharmacokinetic and pharmacodynamic profiles are propofol and methohexitone, both of which can be employed as a component of a TIVA technique. Two TIVA combinations utilising either of these drugs with alfentanil were tested against isoflurane-nitrous oxide in a balanced regimen. Methods. Twenty-seven healthy women undergoing hysterectomy for non-malignant diseases participated in the study after having given written consent. They were randomly allocated to receive either isoflurane (Iso), methohexital-alfentanil (M-A), or propofol-alfentanil (P-A). Blood samples for determination of cortisol, prolactin, catecholamines, glucose, lactate, non-esterified fatty acids, and pharmacon concentrations were drawn repeatedly from before induction until 360 min after surgery. Anaesthesia was induced in group Iso with fentanyl 0.1 mg and M 1.5 mg⋅kg−1 and maintained with Iso-N2O. In the TIVA groups M or P was given in a two-step infusion to load peripheral compartments and then maintain plasma concentrations within the hypnotic range. A was given as a continuous infusion in an identical dose (0.1 mg⋅kg−1 initial, 0.125 mg⋅kg−1⋅h−1 maintenance) in both groups. If signs of insufficient depth of anaesthesia occurred (heart rate or systolic blood pressure 〉25% above baseline), then first A (0.5 – 1 mg), and if that was ineffective, then 50 mg hypnotic was administered. The A infusion was stopped 30 min before the end of surgery, and Iso or the hypnotic was stopped at skin closure. Recovery time was the time until the patients were able to give their birth date after stopping the Iso or hypnotic. Results. The three groups were comparable with regard to age, weight, and duration of surgery. The total doses of M and P were 1,357±125 mg (mean±SEM) and 1,315±121 mg, respectively, and the total A doses were 20.7±2.5 mg (M-A) and 23.4±3.5 (P-A). The peak plasma concentrations were P 10.6±1.5 µg⋅ml−1 and M 12.4±2.6 µg⋅ml−1. At the end of surgery the P concentrations were in the projected range while those of M were somewhat lower than expected (P3.7±0.4 µg⋅ml−1; M 3.5±0.6 µg⋅ml−1). Three patients each in the P-A and M-A groups required supplementary A injections. Five patients in the P-A group required additional bolus injections of the hypnotic as compared to 2 in the M-A group. The median recovery times were Iso 15 min, M-A 50 min, and P-A 25 min (P〈0.05). The incidence of shivering was Iso 3/9, M-A 5/9, and P-A 0/9 (P〈0.05); vomiting occurred with equal frequency in all groups (Iso 33%, M-A 33%, P-A 22%). The patients were somewhat more restless in group M-A. Systolic blood pressure dropped in a similar manner in all groups after induction of anaesthesia (Iso −31%, M-A −37%, P-A −36%) but recovered during surgery. The intraoperative response of cortisol (Iso +216%, M-A +92%, P-A +43%) and catecholamines (noradrenaline Iso +56%, M-A +30%, P-A −21%) was lower in the TIVA groups, whereas prolactin increased after induction in all groups. Plasma concentrations of glucose, lactate, and fatty acids were lower in the TIVA groups than in the Iso group intraoperatively, but increased to comparable postoperative levels. Conclusions. Both TIVA regimens are acceptable alternatives to balanced anaesthesia with Iso N2O. Both are similar with regard to haemodynamic, endocrine, and metabolic changes and are able to reduce the stress response more effectively than Iso N2O. Of the two, P seems to offer the advantage of a somewhat shorter recovery time, less shivering, and calmer patients in the immediate postoperative period, although M might be preferred if economic considerations are important.

Description / Table of Contents: Abstract. Etomidate is a hypnotic with only minor effects on haemodynamics. Although its rapid elimination kinetics would suggest its use in total intravenous anaesthesia (TIVA) and sedation, its administration in higher doses or for a prolonged period has been discouraged due to its inhibitory effects on corticosteroid synthesis. Newer evidence that the suppression of cortisol synthesis might not be total requires a re-evaluation of this drug as a component of a TIVA technique. The effects of high-dose etomidate with fentanyl on spontaneous and stimulated corticosteroid levels as a measure of the magnitude and duration of adrenocortical suppression, as well as on plasma concentrations of adrenocorticotropic hormone (ACTH) β-endorphin, and catecholamines during cardiac surgery were investigated in a prospective, randomised study and compared to those following the administration of midazolam-fentanyl. Patients and methods. Nineteen patients undergoing myocardial revascularisation were assigned to two groups: group 1: etomidate-fentanyl (n=9) and group 2: midazolam-fentanyl (n=10). Anaesthesia was induced with fentanyl 0.5 mg and either etomidate 0.3 mg/kg or midazolam 0.2 mg/kg. Relaxation was achieved with pancuronium 0.1 mg/kg. Anaesthesia was maintained during extracorporeal circulation (ECC) with an infusion of etomidate (0.36 mg⋅kg−1⋅h−1) or midazolam (0.16 mg⋅kg−1⋅h−1) and fentanyl (10 µg⋅kg−1⋅h−1. Blood samples were drawn before induction, before ECC, and 1, 6, and 20 h after surgery. Cortisol secretion was stimulated with 0.25 mg ACTH1 – 24 IV at 6 and 20 h postoperatively. Results. The total drug doses were etomidate 87±3 mg and midazolam 46±2 mg. Plasma cortisol concentrations decreased in the etomidate group from 20 (10 – 31) to 10 (6 – 31) µg⋅dl−1 (median and range) before ECC, but had returned to baseline at 1 h and were significantly increased at 6 h [29 (15 – 47) µg⋅dl−1] and 20 h [46 (29 – 62) µg⋅dl−1]. There was no difference between the groups except at 20 h, when cortisol levels were higher in the etomidate group. The stimulated cortisol increase was markedly impaired in this group at both measuring points. ACTH and β-endorphin were markedly increased in the etomidate group and ACTH concentrations were eight times greater than the corresponding values in the midazolam group after surgery (ACTH 141 vs. 18 pmol⋅l−1). Plasma catecholamine concentrations increased significantly in both groups. Noradrenaline concentrations were greater in the etomidate group at 6 h after surgery. Two patients in the midazolam group and none in the etomidate group required circulatory support with exogenous catecholamines. Discussion. It is concluded that the stress of cardiac surgery can overcome the block in cortisol synthesis caused by the administration of high-dose etomidate by substantially increasing ACTH secretion. The administration of high-dose etomidate was not associated with cardiovascular instability. The use of etomidate as a component of TIVA can therefore not be ruled out on the grounds of insufficient cortisol secretion.

Description / Table of Contents: Abstract Background. Propanidid was widely used as a short-acting i.v. anaesthetic until it was withdrawn due to severe haemodynamic side effects. It was presumed that anaphylactoid reactions with massive histamine release were caused by the solvent cremophor rather than by propanidid itself. A new liposomal preparation of propanidid was examined in this animal study and compared with propanidid in cremophor solution and with propofol. Methods. Eighteen pigs were randomly assigned to one of the following groups: Group 1 (n=6): Propanidid in liposomal preparation (PropaLip; Braun Melsungen, Germany). Anaesthesia was induced with 60 mg/kg, followed by continuous infusion of 400 mg/kg·h. Group 2 (n=6): Propanidid in cremophor solution (PropaCrem; Sombrevin, Gedeon Richter, Budapest) 15 mg/kg, 100 mg/kg·h. Group 3 (n=6): Propofol (Disoprivan, Zeneca, Plankstadt, Germany) 5 mg/kg, 20 mg/kg·h. After induction and tracheal intubation, the animals were ventilated with 50% oxygen in air. Basic monitoring included noninvasive blood pressure measurements, electrocardiographic monitoring, and capnography. In a short surgical procedure, arterial and pulmonary artery catheters were placed via the right carotid artery and right internal jugular vein, respectively. As soon as the animals responded to a pain stimulus a second anaesthetic induction was performed, followed by a 60-min continuous infusion of the agent studied with invasive haemodynamic monitoring including arterial and pulmonary arterial pressures and cardiac output. Blood samples were taken for the measurement of serum levels of adrenaline, noradrenaline, cortisol, aldosterone, adrenocorticotropic hormone, and histamine. Results. Intubation conditions and quality of anaesthesia were best in propofol animals, followed by PropaCrem animals. In spite of the large dose of 410 mg/kg·h, resulting in a volume load of as much as 16.4 ml/kg·h, the PropaLip animals showed evidence of poor anaesthetic quality. In group 1 we recorded the highest increases in heart rate (91 vs. 115/min), cardiac output (5.4 vs. 7.7 l/min), plasma catecholamine levels, and histamine concentrations (124–268 ng/ml). Conclusions. In our animal study, propanidid in liposomal preparation failed to show promise as a new anaesthetic agent. Our results are discussed in view of a drug targeting the cells of the reticuloendothelial system, especially the liver, where liposomes are eliminated from the blood. This may result in the transport of propanidid to one of its major places of inactivation.

Description / Table of Contents: Abstract Objective: Thirty years ago, cardiopulmonary resuscitation (CPR) was primarily developed for otherwise healthy individuals who experienced sudden cardiac arrest. Today, CPR is widely viewed as an emergency procedure that can be attempted on any person who undergoes a cessation of cardiorespiratory function. Therefore, the appropriateness of CPR has been questioned as a matter of the outcome, the patient’s preferences, and the cost. The objective of this article is to analyse ethical issues in prehospital resuscitation. Arguments: CPR is bound by moral considerations that surround the use of any medical treatment. According to Beauchamp and Childress, the hierarchy of justification in biomedical ethics consists of ethical theories, principles, rules, and particular judgements and actions. The decision to start CPR is based on the medical judgement that a person is suffering from circulatory arrest. The decision is justified by the moral rule that the victim of a cardiac arrest has the right to survive and to receive CPR. Moral rules are more specific to contexts and are based on ethical principles. The principle of beneficence means the provision of benefits for the promotion of welfare. Talking about beneficence in resuscitation means once again reporting stories of success, as many victims of pre- and in-hospital sudden death have been saved in the past. Nevertheless, resuscitative efforts still remain unsuccessful in the majority of cases, involving the principle of nonmaleficence. There is potential harm in CPR. Survivors may recover cardiac function, but sustain severe hypoxic brain damage, at worst surviving without awakening for months or years. In particular, post-traumatic CPR is associated with an extremely poor outcome, leading to the issue of futility. However, futility should be defined in a strict fashion, as there might be an individual chance of survival. The principle of respect for autonomy means the right of a patient to accept or reject medical treatment, which continues in emergency conditions and after the patient has lost consciousness. The time frame in CPR requires medical decision-making within seconds, and CPR is usually initiated without the patient’s involvement. If the patient’s wish’s can be ascertained later on, life-sustaining therapies might be withdrawn at that time. Terminally ill but still competent patients should be encouraged to write a no-CPR document, which does not deny patients relief from severe symptoms, but might facilitate withholding resuscitative efforts at the scene. The principle of justice affects priorities in the allocation of health care resources. The decision made for a particular patient might delay or prevent emergency treatment in other patients who could receive greater benefit. Conclusions: The standard of care remains the prompt initiation of CPR. However, ethical principles such as beneficene, nonmaleficence, autonomy, and justice have to be applied in the unique setting of emergency medicine. Physicians have to consider the therapeutic efficacy of CPR, the potential risks, and the patient’s preferences.

Description / Table of Contents: Abstract Syringe drivers are used in anaesthetics, intensive care and emergency medicine to deliver small volumes of highly potent drugs with continuous, constant and reproducible flow. For early recognition of interruptions of the drug delivery caused by occlusion of the infusion system, an alarm is triggered as soon as the system pressure exceeds a certain limit. The sensitivity of this alarm depends on the flow rate, type-specific cut-off pressure and the elastic parameters of the infusion system. The sudden release of pressure built up in the system after occlusion occurred can cause delivery of an uncontrolled drug bolus and hence an additional hazard. Methods: Six syringe drivers that are widely used in clinical practice were tested for alarm delay and bolus delivery in the event of an occlusion in the system. First, the alarm pressures at flow rates of 10, 50 and 100 ml/h were measured. Then the alarm delay time and bolus volumes post-occlusion were assessed, using a basic infusion system (syringe+single infusion set). Finally, several alterations to the system like extension, tap battery with germ filters or branching were made and their impact on alarm delay and bolus volume measured. Results: Because of the great differences in alarm pressures between the devices tested, there were marked differences in the alarm delay at same flow rates. Predictably, there was an indirect proportional link between alarm delay and flow rate. Using the basic infusion system, alarm delays between 23 s and 143 min were measured. In two of the tested syringe drivers, a pressure-release mechanism is activated with the pressure alarm, which prevented bolus application. In the other devices, release of the pressure in the occluded system caused boli of 0.5–7 ml. Variations in the actual syringe volume and insertion of a second connection tube had no impact on alarm delay and bolus volume. Tap batteries, parallel running syringe drivers or trapped air in the system, however, caused marked increase in both alarm delay (107%) and bolus volume (+147%). Discussion: Unidentified occlusions of the system cause grave malfunctioning of syringe drivers. While applying highly potent drugs, the discontinuation of drug delivery with subsequent bolus application can cause vital danger to the patient. As a result of the significant time delays in the pressure alarms, the devices tested do not provide sufficient protection against unrecognized system occlusion. Syringe drivers with adjustable alarm pressure can be set close to the actual infusion pressure. A further important point is that one should aim at a reduction in the elastic properties of the infusion set because of the great impact on alarm delay and bolus volume.