Biomedical subjects

Volker Wenzel

Publications and source records attributed to Volker Wenzel.

83 records · Page 5Linked to original sources

PubMed2002

The effect of midazolam on stress levels during simulated emergency medical service transport: a placebo-controlled, dose-response study.

UNLABELLED: Patients in the emergency medical service (EMS) may have increased endogenous catecholamines because of pain or fear and may benefit from sedation similar to premedication in the hospital. During a simulated EMS scene call, 72 healthy male volunteers were either transported by paramedics from a third-floor apartment through a staircase with subsequent EMS transport with sirens (three stress groups of n = 12; total, n = 36) or asked to sit on a chair for 5 min and lie down on a stretcher for 15 min (three control groups of n = 12; total, n = 36). Catecholamine plasma samples were measured in the respective stress and control groups at baseline and after placebo IV (n = 12) or 25 (n = 12) or 50 (n = 12) microg/kg of midazolam IV throughout the experiment, respectively. Statistical analysis was performed with analysis of variance; P < 0.05 was considered significant. The Placebo Stress versus Control group, but not the 50 microg/kg Stress Midazolam group, had both significantly increased epinephrine (73 +/- 5 pg/mL versus 45 +/- 5 pg/mL; P < 0.001) and norepinephrine (398 +/- 34 pg/mL versus 278 +/- 23 pg/mL; P < 0.01) plasma levels after staircase transport. After EMS transport, the Placebo Stress versus Control group had significantly increased epinephrine (51 +/- 4 pg/mL versus 37 +/- 4 pg/mL; P < 0.05) but not norepinephrine (216 +/- 24 pg/mL versus 237 +/- 18 pg/mL) plasma levels, whereas no significant differences in catecholamine plasma levels occurred between groups after either 25 or 50 microg/kg of midazolam. In conclusion, simulated EMS patients may be subject to more stress during staircase transport than during transport in an EMS vehicle. Titrating sedation with 25 microg/kg of midazolam significantly reduced endogenous catecholamines but not heart rate. IMPLICATIONS: Simulated emergency medical service patients were more likely to be stressed when being transported by paramedics through a staircase than in an ambulance. Accordingly, it may be beneficial to inject sedative drugs before initiating transport to ensure patient comfort and safety.

Adolescent↗

PubMed2002

The prediction of defibrillation outcome using a new combination of mean frequency and amplitude in porcine models of cardiac arrest.

UNLABELLED: We estimated the predictive power with respect to defibrillation outcome of ventricular fibrillation (VF) mean frequency (FREQ), mean peak-to-trough amplitude (AMPL), and their combination. We examined VF electrocardiogram signals of 64 pigs from 4 different cardiac arrest models with different durations of untreated VF, different durations of cardiopulmonary resuscitation, and use of different drugs (epinephrine, vasopressin, N-nitro-L-arginine methyl ester, or saline placebo). The frequency domain was restricted to the range from 4.33 to 30 Hz. In the 10-s epoch between 20 and 10 s before the first defibrillation shock, FREQ and AMPL were estimated. We introduced the survival index (SI; 0.68 Hz(-1). FREQ + 12.69 mV(-1). AMPL) by use of multiple logistic regression. Kruskal-Wallis nonparametric one-way analysis was used to analyze the different porcine models for significant difference. The variables FREQ, AMPL, and SI were compared with defibrillation outcome by means of univariate logistic regression and receiver operating characteristic curves. SI increased predictive power compared with AMPL or FREQ alone, resulting in 89% sensitivity and 86% specificity. The probabilities of predicting defibrillation outcome for FREQ, AMPL, and SI were 0.85, 0.89 and 0.90, respectively. FREQ, AMPL, and SI values were not sensitive in regard to the four different cardiac arrest models but were significantly different for vasopressin and epinephrine animals. IMPLICATIONS: We present a retrospective data analysis to evaluate the predictive power of different ventricular fibrillation electrocardiogram variables in pigs with respect to defibrillation outcome. We showed that our combination of variables leads to an improved forecast, which may help to reduce harmful unsuccessful defibrillation attempts.

Algorithms↗

PubMed2002

A comparison of the laryngeal tube with the laryngeal mask airway during routine surgical procedures.

UNLABELLED: The laryngeal mask airway (LMA; Laryngeal Mask Company, Henley-on-Thames, UK) is an established airway device, whereas the laryngeal tube (LT) is relatively new and therefore not as well investigated. Therefore, the purpose of the present prospective, randomized, controlled trial was to compare the LT with the LMA in routine clinical practice. In 50 patients undergoing general anesthesia for minor routine surgery, standardized anesthesia was induced and maintained with alfentanil and propofol. Patients were randomized to controlled ventilation (fraction of inspired oxygen = 0.4; fraction of inspired nitrous oxide = 0.6; tidal volume = 7 mL/kg; respiratory rate = 10 breaths/min) with the LT (n = 25) or the LMA (n = 25). Oxygen saturation was recorded before the induction of anesthesia and after the administration of oxygen. After 2 and 10 min of ventilation with the LT or LMA, oxygen saturation, end-expiratory carbon dioxide, expiratory tidal volume, and peak airway pressure were recorded. Capillary blood gas samples were taken before the induction of anesthesia and after 10 min of ventilation. Time of insertion and airway leak pressure of each device were measured. The time of insertion was comparable with both devices (LT versus LMA, median 21 s versus 19 s; P = not significant). Blood gas samples and ventilation variables revealed sufficient ventilation and oxygenation with either device (P = not significant). Peak airway pressure (LT, 17 +/- 3 cm H(2)O; LMA, 15 +/- 3 cm H(2)O) and airway leak pressure (LT, 36 +/- 3 cm H(2)O; LMA, 22 +/- 3 cm H(2)O) were significantly (P < 0.05) higher when using the LT compared with the LMA. In conclusion, using the LT and LMA resulted in comparable ventilation and oxygenation variables in this model of ASA physical status I and II patients undergoing routine surgical procedures. The newly developed LT may be a simple alternative device to secure the airway. IMPLICATIONS: The laryngeal tube, a newly developed airway device, and the laryngeal mask airway were used to ventilate patients in the operating room. Both airway devices proved to be effective and safe; however, the laryngeal tube allowed greater airway pressure during ventilation.

Adolescent↗

PubMed2002

Vasopressor response in a porcine model of hypothermic cardiac arrest is improved with active compression-decompression cardiopulmonary resuscitation using the inspiratory impedance threshold valve.

UNLABELLED: During normothermic cardiac arrest, a combination of active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) with the inspiratory threshold valve (ITV) significantly improves vital organ blood flow, but this technique has not been studied during hypothermic cardiac arrest. Accordingly, we evaluated the hemodynamic effects of ACD + ITV CPR before, and after, the administration of vasopressin in a porcine model of hypothermic cardiac arrest. Pigs were surface-cooled until their body core temperature was 26 degrees C. After 10 min of untreated ventricular fibrillation, 14 animals were randomly assigned to either ACD CPR with the ITV (n = 7) or to standard (STD) CPR (n = 7). After 8 min of CPR, all animals received 0.4 U/kg vasopressin IV, and CPR was maintained for an additional 10 min in each group; defibrillation was attempted after 28 min of cardiac arrest, including 18 min of CPR. Before the administration of vasopressin, mean +/- SEM common carotid blood flow was significantly higher in the ACD + ITV group compared with STD CPR (67 +/- 13 versus 26 +/- 5 mL/min, respectively; P < 0.025). After vasopressin was given at minute 8 during CPR, mean +/- SEM coronary perfusion pressure was significantly higher in the ACD + ITV group, but did not increase in the STD group (29 +/- 3 versus 15 +/- 2 mm Hg, and 25 +/- 1 versus 14 +/- 1 mm Hg at minute 12 and 18, respectively; P < 0.001); mean +/- SEM common carotid blood flow remained higher at respective time points (33 +/- 8 versus 10 +/- 3 mL/min, and 31 +/- 7 versus 7 +/- 3 mL/min, respectively; P < 0.01). Without active rewarming, spontaneous circulation was restored and maintained for 1 h in three of seven animals in the ACD + ITV group versus none of seven animals in the STD CPR group (not significant). During hypothermic cardiac arrest, ACD CPR with the ITV improved common carotid blood flow compared with STD CPR alone. Moreover, after the administration of vasopressin, coronary perfusion pressure was significantly higher during ACD + ITV CPR, but not during STD CPR. IMPLICATIONS: New strategies are needed to improve the efficiency of cardiopulmonary resuscitation (CPR) in hypothermic cardiac arrest. Active compression-decompression CPR with the inspiratory threshold valve improved carotid blood flow (and coronary perfusion pressure with vasopressin) compared with standard CPR.

Animals↗

PubMed2002

Arginine vasopressin during cardiopulmonary resuscitation: laboratory evidence, clinical experience and recommendations, and a view to the future.

When stimulating adult pigs with ventricular fibrillation or postcountershock pulseless electrical activity for cardiopulmonary resuscitation, vasopressin improved vital organ blood flow, cerebral oxygen delivery, ability to be resuscitated, and neurologic recovery better than epinephrine. In pediatric preparations with asphyxia, epinephrine was superior to vasopressin, whereas in both pediatric pigs with ventricular fibrillation and adult porcine models with asphyxia, combinations of vasopressin and epinephrine proved to be highly effective. This may suggest that a different efficiency of vasopressors in pediatric vs. adult preparations and different effects of dysrhythmic vs. asphyxial cardiac arrest on vasopressor efficiency may be of significant importance. Whether these theories can be extrapolated to humans is unknown at this time. In patients who experienced out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hrs compared with patients treated with epinephrine; during in-hospital cardiopulmonary resuscitation, comparable short-term survival was found in groups treated with either vasopressin or epinephrine. Currently, a large trial comprising patients who experience out-of-hospital cardiac arrest and who are treated with vasopressin vs. epinephrine is ongoing in Germany, Austria, and Switzerland. The new cardiopulmonary resuscitation guidelines of both the American Heart Association and the European Resuscitation Council consider 40 units of vasopressin intravenously and 1 mg of epinephrine intravenously equally effective for the treatment of adult patients with ventricular fibrillation; however, because of a lack of clinical data, no recommendation for vasopressin has been made for adult patients with asystole and pulseless electrical activity or for pediatric patients.

Adult↗

PubMed2002

Effects of epinephrine and vasopressin in a piglet model of prolonged ventricular fibrillation and cardiopulmonary resuscitation.

OBJECTIVE: We recently demonstrated that vasopressin alone resulted in a poorer outcome in a pediatric porcine model of asphyxial cardiac arrest when compared with epinephrine alone or with epinephrine plus vasopressin in combination. Accordingly, this study was designed to differentiate whether the inferior effects of vasopressin in pediatrics were caused by the type of cardiac arrest. DESIGN: Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow. SETTING: University hospital laboratory. SUBJECTS: Eighteen piglets weighing 8-11 kg. INTERVENTIONS: After 8 mins of ventricular fibrillation and 8 mins of cardiopulmonary resuscitation, either 0.4 units/kg vasopressin (n = 6), 45 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered. Six minutes after drug administration, a second respective bolus dose of 0.8 units/kg vasopressin, 200 microg/kg epinephrine, or a combination of 200 microg/kg epinephrine with 0.8 units/kg vasopressin was given. Defibrillation was attempted 20 mins after initiating cardiopulmonary resuscitation. MEASUREMENTS AND MAIN RESULTS: Mean +/- sem left ventricular myocardial blood flow 2 mins after each respective drug administration was 65 +/- 4 and 70 +/- 13 mL x min(-1) x 100 g(-1) in the vasopressin group; 83 +/- 42 and 85 +/- 41 mL x min(-1) x 100 g(-1) in the epinephrine group; and 176 +/- 32 and 187 +/- 29 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p <.006 after both doses of epinephrine-vasopressin vs. vasopressin and after the first dose of epinephrine-vasopressin vs. epinephrine, respectively). At the same times, mean +/- sem total cerebral blood flow was 73 +/- 3 and 47 +/- 5 mL x min(-1) x 100 g(-1) after vasopressin; 18 +/- 2 and 12 +/- 2 mL x min(-1) x 100 g(-1) after epinephrine; and 79 +/- 21 and 41 +/- 8 mL x min(-1) x 100 g(-1) after epinephrine-vasopressin (p <.025 after both doses of vasopressin and epinephrine-vasopressin vs. epinephrine). Five of six vasopressin-treated, two of six epinephrine-treated, and six of six epinephrine-vasopressin treated animals had return of spontaneous circulation (nonsignificant). CONCLUSIONS: In this pediatric porcine model of ventricular fibrillation, the combination of epinephrine with vasopressin during cardiopulmonary resuscitation resulted in significantly higher levels of left ventricular myocardial blood flow than either vasopressin alone or epinephrine alone. Both vasopressin alone and the combination of epinephrine with vasopressin, but not epinephrine alone, improved total cerebral blood flow during cardiopulmonary resuscitation. In stark contrast to asphyxial cardiac arrest, vasopressin alone or in combination with epinephrine appears to be of benefit after ventricular fibrillation in the pediatric porcine model.

Animals↗

PubMed2002

Vasopressin improves survival in a pig model of hypothermic cardiopulmonary resuscitation.

OBJECTIVE: During hypothermic cardiopulmonary resuscitation with a body core temperature <30 degrees C administration of a vasopressor to support coronary perfusion pressure is controversial. The purpose of the current study was to assess the effects of a single 0.4-unit/kg dose of vasopressin on coronary perfusion pressure, defibrillation success, and 1-hr survival in a pig model of hypothermic closed-chest cardiopulmonary resuscitation combined with rewarming. DESIGN: Prospective, randomized study in an established pig model. SETTING: University hospital research laboratory. SUBJECTS: Fifteen 12- to 16-wk-old domestic pigs. INTERVENTIONS: Pigs were surface cooled to a body core temperature of 26 degrees C and ventricular fibrillation was induced. After 15 mins of untreated cardiac arrest, manual closed-chest cardiopulmonary resuscitation and thoracic lavage with 40 degrees C warmed tap water were started. After 3 mins of external chest compression, animals were assigned randomly to receive vasopressin (0.4 units/kg, n = 8; or saline placebo, n = 7). Defibrillation was attempted 10 mins after drug administration. MEASUREMENTS AND MAIN RESULTS: Compared with saline placebo treated-animals, coronary perfusion pressure in vasopressin-treated pigs was significantly higher 90 secs (36 +/- 5 mm Hg vs. 7 +/- 4 mm Hg, p =.000) to 10 mins (24 +/- 4 mm Hg vs. 8 +/- 4 mm Hg, p =.000) after drug administration. Restoration of spontaneous circulation and 1 hr survival were significantly higher in vasopressin animals compared with saline placebo (8 of 8 vasopressin pigs vs. 0 of 7 placebo pigs, p <.001). CONCLUSIONS: A single 0.4-unit/kg dose of vasopressin administered at a body core temperature <30 degrees C significantly improved defibrillation success and 1-hr survival in a pig model of hypothermic cardiopulmonary resuscitation.

Animals↗

PubMed2002

Pulmonary gas exchange after cardiopulmonary resuscitation with either vasopressin or epinephrine.

OBJECTIVE: It is well established that epinephrine administered during cardiopulmonary resuscitation results in pulmonary gas exchange disturbances. It is uncertain how vasopressin affects gas exchange after cardiopulmonary resuscitation. DESIGN: Prospective, randomized experimental study. SETTING: Animal research laboratory. SUBJECTS: Twenty domestic pigs. INTERVENTIONS: Animals were subjected to ventricular fibrillation and cardiopulmonary resuscitation by using either vasopressin or epinephrine. Hemodynamic and pulmonary gas exchange (multiple inert gas elimination technique) variables were recorded before cardiopulmonary resuscitation and 10, 30, 60, and 120 mins after return of spontaneous circulation when either epinephrine (control) or vasopressin was used. MEASUREMENTS AND MAIN RESULTS: At 10 mins after return of spontaneous circulation, blood flow to low V /Q lung units was increased in animals treated with epinephrine (17.8 +/- 6 vs. 2.6 +/- 3%, mean +/- sd, p<.01). Resulting carbon dioxide elimination was impaired in animals treated with epinephrine but not in animals treated with vasopressin (PaCO2, 55 +/- 2 vs. 46 +/- 4 torr, p<.05). Thirty minutes after return of spontaneous circulation, blood flow to lung units with a normal VA /Q ratio was reduced in animals treated with epinephrine (79 +/- 1 vs. 84 +/- 12%, p<.05), resulting in a depressed PaO2 (147 +/- 4 vs. 127 +/- 10 torr, p<.05). CONCLUSION: Vasopressin compared with epinephrine for cardiopulmonary resuscitation resulted in better gas exchange variables in the early postresuscitation phase.

Animals↗

PubMed2002

Alternative ventilation strategies in cardiopulmonary resuscitation.

The introduction of the 2000 Guidelines for Cardiopulmonary Resuscitation emphasizes a new, evidence-based approach to the science of ventilation during cardiopulmonary resuscitation (CPR). New laboratory and clinical science underemphasizes the role of ventilation immediately after a dysrhythmic cardiac arrest (arrest primarily resulting from a cardiovascular event, such as ventricular defibrillation or asystole). However, the classic airway patency, breathing, and circulation (ABC) CPR sequence remains a fundamental factor for the immediate survival and neurologic outcome of patients after asphyxial cardiac arrest (cardiac arrest primarily resulting from respiratory arrest). The hidden danger of ventilation of the unprotected airway during cardiac arrest either by mouth-to-mouth or by mask can be minimized by applying ventilation techniques that decrease stomach gas insufflation. This goal can be achieved by decreasing peak inspiratory flow rate, increasing inspiratory time, and decreasing tidal volume to approximately 5 to 7 mL/kg, if oxygen is available. Laboratory and clinical evidence recently supported the important role of alternative airway devices to mask ventilation and endotracheal intubation in the chain of survival. In particular, the laryngeal mask airway and esophageal Combitube proved to be effective alternatives in providing oxygenation and ventilation to the patient in cardiac arrest in the prehospital arena in North America. Prompt recognition of supraglottic obstruction of the airway is fundamental for the management of patients in cardiac arrest when ventilation and oxygenation cannot be provided by conventional methods. "Minimally invasive" cricothyroidotomy devices are now available for the professional health care provider who is not proficient or comfortable with performing an emergency surgical tracheotomy or cricothyroidotomy. Finally, a recent device that affects the relative influence of positive pressure ventilation on the hemodynamics during cardiac arrest has been introduced, the inspiratory impedance threshold valve, with the goal of maximizing coronary and cerebral perfusion while performing CPR. Although the role of this alternative ventilatory methodology in CPR is rapidly being established, we cannot overemphasize the need for proper training to minimize complications and maximize the efficacy of these new devices.

Cardiopulmonary Resuscitation↗

PubMed2002

Early intensive care unit intervention for trauma care: what alters the outcome?

This review focuses on early management of multiple trauma patients with traumatic brain injury. Early usage of multislice computed tomography can substantially shorten the time spent on diagnostic workup in the emergency room and, therefore, speeds the initiation of lifesaving interventions for the control of hemorrhage. The important role of hemostatic angiographic embolization and its timing, in addition to surgical control of bleeding in patients suffering from pelvic fracture or organ lesions, is emphasized. The ongoing controversy regarding the strategy of fluid resuscitation is discussed. The concept of permissive hypotension seems to be promising but is absolutely contraindicated in patients with traumatic brain injury. Coagulation management should be guided by coagulation monitoring, including thromboelastography. A novel approach to reduce major bleeding is the application of recombinant factor VIIa. Strong effort should be directed toward the management of traumatic brain injury and the maintenance of cerebral perfusion pressure. The optimization of treatment of patients with multiple trauma, including brain injury, is a multidisciplinary task.

Algorithms↗

PubMed2002

Effects of active compression-decompression cardiopulmonary resuscitation with the inspiratory threshold valve in a young porcine model of cardiac arrest.

Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) with the inspiratory threshold valve (ITV) has been recently recommended by the American Heart Association for treatment of adults in cardiac arrest (class IIb: alternative, useful intervention), but this new technique has never been used in a pediatric population. Thus, this study was designed to evaluate ACD + ITV CPR in a young porcine model of cardiac arrest. After 10 min of ventricular fibrillation, and 8 min of standard CPR, ACD + ITV CPR was performed in seven 4- to 6-wk-old pigs (8-12 kg); defibrillation was attempted 8 min later. Within 2 min after initiation of ACD + ITV CPR, mean (+/- SEM) coronary perfusion pressure increased from 18 +/- 2 to 24 +/- 3 mm Hg (p = 0.018). During standard versus ACD + ITV CPR, mean left ventricular myocardial and total cerebral blood flow was 59 +/- 21 versus 126 +/- 32 mL.min(-1).100 g(-1), and 36 +/- 7 versus 60 +/- 15 mL.min(-1).100 g(-1), respectively (p = 0.028). Six of seven animals were successfully defibrillated, and survived >15 min. In conclusion, the combination of ACD + ITV CPR significantly increased both coronary perfusion pressure and vital organ blood flow after prolonged standard CPR in this young porcine model of ventricular fibrillation.

Adult↗