A Frotzler

A clinical study on the effect in horses during medetomidine–isoflurane anaesthesia, of butorphanol constant rate infusion on isoflurane requirements, on cardiopulmonary function and on recovery characteristics

OBJECTIVE To test if the addition of butorphanol by constant rate infusion (CRI) to medetomidine-isoflurane anaesthesia reduced isoflurane requirements, and influenced cardiopulmonary function and/or recovery characteristics. STUDY DESIGN Prospective blinded randomised clinical trial. ANIMALS 61 horses undergoing elective surgery. METHODS Horses were sedated with intravenous (i.v.) medetomidine (7 μg kg(-1)); anaesthesia was induced with i.v. ketamine (2.2 mg kg(-1)) and diazepam (0.02 mg kg(-1)) and maintained with isoflurane and a CRI of medetomidine (3.5 μg kg(-1) hour(-1)). Group MB (n = 31) received butorphanol CRI (25 μg kg(-1) i.v. bolus then 25 μg kg(-1) hour(-1)); Group M (n = 30) an equal volume of saline. Artificial ventilation maintained end-tidal CO2 in the normal range. Horses received lactated Ringers solution 5 mL kg(-1) hour(-1), dobutamine <1.25 μg kg(-1) minute(-1) and colloids if required. Inspired and exhaled gases, heart rate and mean arterial blood pressure (MAP) were monitored continuously; pH and arterial blood gases were measured every 30 minutes. Recovery was timed and scored. Data were analyzed using two way repeated measures anova, independent t-tests or Mann-Whitney Rank Sum test (p < 0.05). RESULTS There was no difference between groups with respect to anaesthesia duration, end-tidal isoflurane (MB: mean 1.06 ± SD 0.11, M: 1.05 ± 0.1%), MAP (MB: 88 ± 9, M: 87 ± 7 mmHg), heart rate (MB: 33 ± 6, M: 35 ± 8 beats minute(-1)), pH, PaO2 (MB: 19.2 ± 6.6, M: 18.2 ± 6.6 kPa) or PaCO2. Recovery times and quality did not differ between groups, but the time to extubation was significantly longer in group MB (26.9 ± 10.9 minutes) than in group M (20.4 ± 9.4 minutes). CONCLUSION AND CLINICAL RELEVANCE Butorphanol CRI at the dose used does not decrease isoflurane requirements in horses anaesthetised with medetomidine-isoflurane and has no influence on cardiopulmonary function or recovery.

Electrocardiographic alterations during intravascular application of three different test doses of bupivacaine and epinephrine: experimental study in neonatal pigs

BACKGROUND Origin of electrocardiographic (ECG) alterations during intravascular injection of local anaesthetic solutions is controversial. The aim of this study was to elucidate whether epinephrine, bupivacaine or their combination is responsible for ECG alteration. METHODS Forty-five piglets were randomized into three groups. After induction of general anaesthesia using sevoflurane and peripheral venous cannulation, the trachea was intubated, the lungs were artificially ventilated, and anaesthesia was maintained by sevoflurane. Under steady state 0.2 ml kg(-1) and after 10 min 0.4 ml kg(-1) of one of the following three test solutions was administered i.v.: bupivacaine 0.125% (Group 1), bupivacaine 0.125%+epinephrine 1:200 000 (Group 2), and plain epinephrine 1:200,000 (Group 3). The ECG was analysed for alterations in heart rate and T-elevation. RESULTS After injection of 0.2 or 0.4 ml kg(-1) test solution, an increase in heart rate of at least 10% was found in none of Group 1 and in all of Groups 2 and 3. After application of 0.2 ml kg(-1) test solution, T-elevation was found in 7% of Group 1 and in 93% of Groups 2 and 3. The injection of 0.4 ml kg(-1) revealed a T-elevation in 27%, 100%, and 100%, respectively, in Groups 1, 2, and 3. CONCLUSIONS This animal model demonstrated that increases in heart rate and T-elevation in the ECG during i.v. application of a common test dose (0.2 ml kg(-1)) of bupivacaine are caused by epinephrine addition. Whether higher doses of bupivacaine alone can cause similar ECG changes or not requires further studies.

Electrocardiographic changes during continuous intravenous application of bupivacaine in neonatal pigs

BACKGROUND It is controversial as to whether T-wave elevation is caused by local anaesthetics, epinephrine, or their combination. It has been shown that T-elevation after intravascular injection of a small bupivacaine test dose is caused by epinephrine and not by bupivacaine. The aim of this study was to investigate ECG changes with higher doses of i.v. bupivacaine. METHODS Thirty neonatal pigs were anaesthetized with sevoflurane and their tracheas intubated and artificially ventilated. Under steady-state conditions, bupivacaine was continuously infused (flow rate 3.2 ml kg(-1) min(-1)) by a syringe infusion pump through a central venous catheter. Group 1 received bupivacaine 0.125%, Group 2 bupivacaine 0.5%. The ECG was continuously printed and subsequently analysed for alterations in heart rate, ventricular de- and repolarization, and arrhythmias at 1.25, 2.5, and 5 mg kg(-1) bupivacaine infused. RESULTS Sinus rhythm persisted in all pigs. Heart rate decreased progressively in both groups, but this was significantly more pronounced in Group 1. T-wave elevation occurred in 40% and 0% (Groups 1 and 2) at 1.25 mg kg(-1), in 80% and 0% at 2.5 mg kg(-1), and in 93% and 80% at 5 mg kg(-1) bupivacaine infused. There were significant differences between the two groups at 1.25 and 2.5 mg kg(-1) infused. CONCLUSIONS Higher doses of i.v. infused bupivacaine can cause T-elevation. With slower injection technique, T-elevation can already be detected at lower bupivacaine doses administered.

Massive aspiration past the tracheal tube cuff caused by closed tracheal suction system.

Background: Aspiration past the tracheal tube cuff has been recognized to be a risk factor for the development of ventilator-associated pneumonia (VAP). This study investigated the effect of closed tracheal suctioning on aspiration of fluid past the tracheal tube cuff in an in vitro benchtop model. Methods: High-volume low pressure tube cuffs of 7.5 mm internal diameter (ID) were placed in a 22 mm ID artificial trachea connected to a test lung. Positive pressure ventilation (PPV) with 15 cm H2O peak inspiratory pressure and 5 cm H2O positive end-expiratory pressure (PEEP) was used. A closed tracheal suction system (CTSS) catheter (size 14Fr) was attached to the tracheal tube and suction was performed for 5, 10, 15, or 20 seconds under 200 or 300 cm H2O suction pressures. Amount of fluid (mL) aspirated along the tube cuff and the airway pressure changes were recorded for each suction procedure. Fluid aspiration during different suction conditions was compared using Kruskal-Wallis and Mann-Whitney test (Bonferroni correction [α = .01]). Results: During 10, 15, and 20 seconds suction, airway pressure consistently dropped down to −8 to −13 cm H2O (P < .001) from the preset level. Fluid aspiration was never observed under PPV + PEEP but occurred always during suctioning. Aspiration along the tube cuff was higher with −300 cm H2O than with −200 cm H2O suction pressure (P < .001) and was much more during 15 and 20 seconds suction time as compared to 5seconds (P < .001). Conclusion: Massive aspiration of fluid occurs along the tracheal tube cuff during suction with the closed tracheal suction system.

Vergleich von Antibeschlagmethoden in der Endoskopie

BACKGROUND The use of a flexible or rigid fiberoptic bronchoscope belongs to the standard repertoire in anesthesiology. Besides a lack of training these procedures may be considerably compromised by endoscopic lens fogging. Several antifogging approaches are commercially available but to date no controlled studies regarding the efficacy of these devices in bronchoscopes exists. The aim of the present study was to compare the efficacy of different commercially available anti-fogging techniques for rigid and flexible bronchoscopes. MATERIALS AND METHODS The study was performed at the department of anesthesia in a university childrens hospital. An artificial airway model was created to simulate in vivo conditions with respect to airflow, temperature and atmospheric moisture. A test picture was inserted into the artificial airway for assuring a standardized view through the bronchoscopes. Antifogging efficacy of two liquid antifog solutions (Ultrastop and Anti-Fog), two antifog wipes (Lina Clear and Reso Clear) and an induction endoscope preheater system (used after one and two induction preheating phases) was assessed by video taping of the bronchoscope view of the test picture. In addition the administration of continuous oxygen airflow of 2 l min⁻¹ through the suction channel of the flexible bronchoscope was tested as an alternative method to prevent lens fogging. All final pictures were rated by 10 staff anesthesiologists who were blinded to the antifog devices used. To assess the clinical relevance of the results, ratings were classified into a 5 grade rating scale (ranging from no visualization of any structure to excellent endoscopic view allowing safe endotracheal intubation). In addition, the failure rate of each anti-fog technique was calculated. RESULTS A total of 300 endoscopic test pictures were taken and assessed. Using the flexible bronchoscope, the use of anti-fog solution (failure rate 3 %) and Lina Clear wipes (failure rate 4%) showed the best results. In the rigid bronchoscope group Ultrastop solution (failure rate 5 %) and Lina Clear wipes (failure rate 3.5 %) showed superior results. The two-time use of the endoscope preheater system was effective using flexible (failure rate 6 %) and rigid bronchoscopes (failure rate 10 %). The application of a continuous oxygen flow of 2 l/min failed to provide a clear endoscopic view (failure rate 93.5 %). CONCLUSIONS All commercially available antifog liquids and wipes showed slightly different reduction of lens fogging. However, other factors such as frequency of usage, the type of endoscope, hygiene properties as well as cost-effectiveness might have a substantial impact on the comparison of all tested anti-fog devices. The use of an endoscope preheater system might be a conceivable alternative method to reduce lens fogging despite the higher initial cost. However, the multiple use of the preheater system cannot be recommended at present as additional handling procedures to ensure an appropriate but safe temperature of the endoscopic tip should be provided by the manufacturer. Application of a continuous oxygen flow was shown not to be effective in preventing lens fogging using a flexible fiberoptic bronchoscope.

Comparison of antifog methods in endoscopy. What really helps

BACKGROUND The use of a flexible or rigid fiberoptic bronchoscope belongs to the standard repertoire in anesthesiology. Besides a lack of training these procedures may be considerably compromised by endoscopic lens fogging. Several antifogging approaches are commercially available but to date no controlled studies regarding the efficacy of these devices in bronchoscopes exists. The aim of the present study was to compare the efficacy of different commercially available anti-fogging techniques for rigid and flexible bronchoscopes. MATERIALS AND METHODS The study was performed at the department of anesthesia in a university childrens hospital. An artificial airway model was created to simulate in vivo conditions with respect to airflow, temperature and atmospheric moisture. A test picture was inserted into the artificial airway for assuring a standardized view through the bronchoscopes. Antifogging efficacy of two liquid antifog solutions (Ultrastop and Anti-Fog), two antifog wipes (Lina Clear and Reso Clear) and an induction endoscope preheater system (used after one and two induction preheating phases) was assessed by video taping of the bronchoscope view of the test picture. In addition the administration of continuous oxygen airflow of 2 l min⁻¹ through the suction channel of the flexible bronchoscope was tested as an alternative method to prevent lens fogging. All final pictures were rated by 10 staff anesthesiologists who were blinded to the antifog devices used. To assess the clinical relevance of the results, ratings were classified into a 5 grade rating scale (ranging from no visualization of any structure to excellent endoscopic view allowing safe endotracheal intubation). In addition, the failure rate of each anti-fog technique was calculated. RESULTS A total of 300 endoscopic test pictures were taken and assessed. Using the flexible bronchoscope, the use of anti-fog solution (failure rate 3 %) and Lina Clear wipes (failure rate 4%) showed the best results. In the rigid bronchoscope group Ultrastop solution (failure rate 5 %) and Lina Clear wipes (failure rate 3.5 %) showed superior results. The two-time use of the endoscope preheater system was effective using flexible (failure rate 6 %) and rigid bronchoscopes (failure rate 10 %). The application of a continuous oxygen flow of 2 l/min failed to provide a clear endoscopic view (failure rate 93.5 %). CONCLUSIONS All commercially available antifog liquids and wipes showed slightly different reduction of lens fogging. However, other factors such as frequency of usage, the type of endoscope, hygiene properties as well as cost-effectiveness might have a substantial impact on the comparison of all tested anti-fog devices. The use of an endoscope preheater system might be a conceivable alternative method to reduce lens fogging despite the higher initial cost. However, the multiple use of the preheater system cannot be recommended at present as additional handling procedures to ensure an appropriate but safe temperature of the endoscopic tip should be provided by the manufacturer. Application of a continuous oxygen flow was shown not to be effective in preventing lens fogging using a flexible fiberoptic bronchoscope.

Impact of propofol on electrocardiographic alterations during intravascular application of bupivacaine--a study in piglets.

Background:  Intravascular application of a small dose of local anesthetics (LA) with epinephrine as well as larger doses of LA under sevoflurane anesthesia results in increase in T‐wave amplitude in the electrocardiogram (ECG). The aim of this study was to elucidate whether propofol anesthesia affects these ECG alterations or not.

Vergleich von Antibeschlagmethoden in der Endoskopie@@@Comparison of antifog methods in endoscopy: Was wirklich hilft@@@What really helps

BACKGROUND The use of a flexible or rigid fiberoptic bronchoscope belongs to the standard repertoire in anesthesiology. Besides a lack of training these procedures may be considerably compromised by endoscopic lens fogging. Several antifogging approaches are commercially available but to date no controlled studies regarding the efficacy of these devices in bronchoscopes exists. The aim of the present study was to compare the efficacy of different commercially available anti-fogging techniques for rigid and flexible bronchoscopes. MATERIALS AND METHODS The study was performed at the department of anesthesia in a university childrens hospital. An artificial airway model was created to simulate in vivo conditions with respect to airflow, temperature and atmospheric moisture. A test picture was inserted into the artificial airway for assuring a standardized view through the bronchoscopes. Antifogging efficacy of two liquid antifog solutions (Ultrastop and Anti-Fog), two antifog wipes (Lina Clear and Reso Clear) and an induction endoscope preheater system (used after one and two induction preheating phases) was assessed by video taping of the bronchoscope view of the test picture. In addition the administration of continuous oxygen airflow of 2 l min⁻¹ through the suction channel of the flexible bronchoscope was tested as an alternative method to prevent lens fogging. All final pictures were rated by 10 staff anesthesiologists who were blinded to the antifog devices used. To assess the clinical relevance of the results, ratings were classified into a 5 grade rating scale (ranging from no visualization of any structure to excellent endoscopic view allowing safe endotracheal intubation). In addition, the failure rate of each anti-fog technique was calculated. RESULTS A total of 300 endoscopic test pictures were taken and assessed. Using the flexible bronchoscope, the use of anti-fog solution (failure rate 3 %) and Lina Clear wipes (failure rate 4%) showed the best results. In the rigid bronchoscope group Ultrastop solution (failure rate 5 %) and Lina Clear wipes (failure rate 3.5 %) showed superior results. The two-time use of the endoscope preheater system was effective using flexible (failure rate 6 %) and rigid bronchoscopes (failure rate 10 %). The application of a continuous oxygen flow of 2 l/min failed to provide a clear endoscopic view (failure rate 93.5 %). CONCLUSIONS All commercially available antifog liquids and wipes showed slightly different reduction of lens fogging. However, other factors such as frequency of usage, the type of endoscope, hygiene properties as well as cost-effectiveness might have a substantial impact on the comparison of all tested anti-fog devices. The use of an endoscope preheater system might be a conceivable alternative method to reduce lens fogging despite the higher initial cost. However, the multiple use of the preheater system cannot be recommended at present as additional handling procedures to ensure an appropriate but safe temperature of the endoscopic tip should be provided by the manufacturer. Application of a continuous oxygen flow was shown not to be effective in preventing lens fogging using a flexible fiberoptic bronchoscope.