Verzicht auf Einleitung oder Abbruch einer Reanimation in der Präklinik

Nicht selten wird der Notarzt mit Patienten mit einem Herz-Kreislauf-Stillstand konfrontiert, wobei sich im Einzelfall die Frage stellt, ob eine kardiopulmonale Reanimation nicht begonnen oder eine bereits begonnene Reanimation beendet werden soll. Hierzu gibt es Leitlinien und Stellungnahmen des ERC und der Bundesärztekammer sowie Hinweise in der Literatur. Nachdem es für diese Frage aber keine verbindlichen und allgemeingültigen Kriterien gibt, ist in diese individuelle Entscheidung neben der Anamnese die jeweilige aktuelle Situation einzubeziehen, und diese kann nicht aufgrund starrer Zeitvorgaben getroffen werden. Neben generellen Prognosefaktoren wird auf die Besonderheiten der Reanimation bei Polytrauma, Hypothermie, Lungenarterienembolie und Suizid eingegangen. Eine besondere Patientengruppe stellen ältere Patienten dar, bei denen manchmal eine sogenannte „Schein“-Reanimation durchgeführt wird. In die Entscheidung zur Durchführung oder zum Abbruch einer Reanimation ist auch der Patientenwille miteinzubeziehen, sofern dieser vor Ort zweifelsfrei erkennbar ist. Gründe für das Unterlassen einer Reanimation im präklinischen Bereich werden zusammenfassend dargestellt.

[Mass maritime casualty incidents in German waters: structures and resources]

The Central Command for Maritime Emergencies was founded in Germany in 2003 triggered by the fire on board of the cargo ship "Pallas" in 1998. Its mission is to coordinate and direct measures at or above state level in maritime emergency situations in the North Sea and the Baltic Sea. A special task in this case is to provide firefighting and medical care. To face these challenges at sea emergency doctors and firemen have been specially trained. This form of organization provides a concept to counter mass casualty incidents and peril situations at sea. Since the foundation of the Central Command for Maritime Emergencies there have been 5 operations for firefighting units and 4 for medical response teams. Assignments and structure of the Central Command for Maritime Emergencies are unique in Europe.

Indirect videolaryngoscopy with C-MAC D-Blade and GlideScope: a randomized, controlled comparison in patients with suspected difficult airways

BACKGROUND

Recently, indirect videolaryngoscopes have become increasingly important devices in difficult airway management. The aim of the present study was to investigate laryngoscopic view and intubation success using the new C-MAC® D-Blade in comparison to the established GlideScope® videolaryngoscope and conventional direct laryngoscopy in a randomized controlled trial.

METHODS

Ninety-six adult patients with expected difficult airways undergoing elective ear, nose and throat surgery (ENT) requiring general anesthesia were investigated. Repeated laryngoscopy was performed using a conventional direct Macintosh laryngoscope (DL), C-MAC D-Blade (DB) and GlideScope (GS) in a randomized sequence before patients were intubated with the last device used.

RESULTS

Both videolaryngoscopes showed significantly better C/L (Cormack-Lehane) classes than DL. Insufficient laryngoscopic view, defined as C/L ≥ III, was experienced in 18 patients (19.2%) with DL, in two patients with GS (2.1%) and in none with DB (0%). Time to best achievable laryngoscopic view did not differ between devices. Intubation time was significantly longer with both videolaryngoscopes (Median [Range] DB: 18 [8-33] s, and GS: 19 [9-34] s) than with DL (11 [5-26] s). However, intubation success was 100% for both DB and GS, whereas four patients could not be intubated using conventional direct laryngoscopy.

CONCLUSION

Compared to direct Macintosh laryngoscopy, both C-MAC® D-Blade and GlideScope® comparably resulted in an improved view of the glottic opening with successful tracheal intubation in all patients.

Evaluation of the pediatric Bonfils fiberscope for elective endotracheal intubation

BACKGROUND

Difficult airway management in children is a particular challenge for anesthesiologists and pediatricians. This study was designed to evaluate the performance of the recently developed pediatric versions of the Bonfils fiberscope for elective endotracheal intubation during routine surgical procedures.

METHODS

After approval by the institutional review board and written informed consent, 55 children (age 6 +/- 4 years) scheduled for elective minor surgical procedures were enrolled. Nineteen children received atropine before the intubation attempt, while in the remaining 36 children, no antisialogogue was used. For endotracheal tubes up to 3.5 mm internal diameter, a fiberscope with outer diameter (OD) 2 mm, and for larger endotracheal tubes, a fiberscope OD 3.5 mm was used. Time to intubation and failure rate were obtained.

RESULTS

In the 36 children without and the 19 children with atropine pretreatment, the success rate for tracheal intubation on the first attempt was 69%/78% (25/15 patients). 4/3 patients and 2/0 patients were intubated after two and three attempts, respectively, and in 5/1 patients (14%/5%) intubation failed even after three attempts. Time to intubation was median 58/60 s, 25th-75th percentile 35-100/32-110 s, and range 14-377/18-360 s. In both groups, failed intubations were because of the secretions contaminating the optic aperture.

CONCLUSIONS

High failure rate and increased intubation times suggest that the pediatric Bonfils fiberscope has significant drawbacks when used for intubation of normal pediatric airways.

[The DGAI CPR registry - the datasets "hospital care" and "long-term process"]

After several years of preparation the German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin--DGAI) has, during its annual conference 2007, officially launched the DGAI CPR registry. After implementation of the dataset "primary care" in 2004, the datasets "definite care" and "long-term process" have now been released. The completed, internet based database is open for any interested person or institution as a tool for quality management. Data may be recorded online, and basic analyses be performed immediately. Beyond that benchmarks with other institutions are possible, by including the well accepted Utstein style on international level too.

[Inter-hospital transfer of patients in intensive care treatment. A systematic review]

An obvious trend of concentrating treatment options on specialized centres may take effect later in an increased need for inter-hospital transfer. Patients initially referred to secondary or tertiary hospitals require a safe and systematically organised transport in order to ensure a continuation of initiated actions in intensive care. This review will focus of appropriate preparations, equipment and transport modalities, possible sources of shortcomings as well as solutions of conflicts during inter-hospital transfers.

Revised resuscitation guidelines: Adrenaline versus adrenaline/vasopressin in a pig model of cardiopulmonary resuscitation—A randomised, controlled trial

BACKGROUND

Synergistic effects of adrenaline (epinephrine) and vasopressin may be beneficial during cardiopulmonary resuscitation. However, it is unknown whether either adrenaline alone or an alternating administration of adrenaline and vasopressin is better for restoring vital organ perfusion following basic life support (BLS) according to the revised algorithm with a compression-to-ventilation (c/v) ratio of 30:2.

MATERIAL AND METHODS

After 4min of ventricular fibrillation, and 6min of BLS with a c/v ratio of 30:2, 16 pigs were randomised to receive either 45microg/kg adrenaline, or alternating 45microg/kg adrenaline and 0.4U/kg vasopressin, respectively.

RESULTS

Coronary perfusion pressure (mean+/-S.D.) 20 and 25min after cardiac arrest was 7+/-4 and 5+/-3mm Hg after adrenaline, and 25+/-2 and 14+/-3mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), respectively. Cerebral perfusion pressure was 23+/-7 and 19+/-9mm Hg after adrenaline, and 40+/-10 and 33+/-7mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), and cerebral blood flow was 30+/-10 and 27+/-11% of baseline after adrenaline, and 65+/-40 and 50+/-31% of baseline after adrenaline/vasopressin (p<0.05 versus adrenaline), respectively. Return of spontaneous circulation (ROSC) did not differ significantly between the adrenaline group (0/8) and the adrenaline/vasopressin group (3/8).

CONCLUSION

Adrenaline/vasopressin resulted in higher coronary and cerebral perfusion pressures, and cerebral blood flow, while ROSC was comparable.

[Vasopressin for therapy of persistent traumatic hemorrhagic shock: The VITRIS.at study]

While fluid management is established in controlled hemorrhagic shock, its use in uncontrolled hemorrhagic shock is being controversially discussed, because it may worsen bleeding. In the irreversible phase of hemorrhagic shock that was unresponsive to volume replacement, airway management and catecholamines, vasopressin was beneficial due to an increase in arterial blood pressure, shift of blood away from a subdiaphragmatic bleeding site towards the heart and brain and decrease of fluid resuscitation requirements. The purpose of this multicenter, randomized, controlled, international trial is to assess the effects of vasopressin (10 IU IV) vs. saline placebo IV (up to 3 injections at least 5 min apart) in patients with prehospital traumatic hemorrhagic shock that persists despite standard shock treatment. The study will be carried out by helicopter emergency medical service teams in Austria, Germany, Czech Republic, Portugal, the Netherlands and Switzerland. Inclusion criteria are adult trauma patients with presumed traumatic hemorrhagic shock (systolic arterial blood pressure <90 mmHg) that does not respond to the first 10 min of standard shock treatment (endotracheal intubation, fluid resuscitation and use of vasopressors) after arrival of the first emergency physician at the scene. The time window for randomization will close after 30 min of shock treatment. Exclusion criteria are terminal illness, no intravenous access, age <18 years, injury >60 min before randomization, cardiac arrest before randomization, presence of a do-not-resuscitate order, untreated tension pneumothorax, untreated cardiac tamponade, or known pregnancy. Primary study end-point is the hospital admission rate, secondary end-points are hemodynamic variables, fluid resuscitation requirements and hospital discharge rate.

[Hypothermia after cardiac arrest--daily trained clinical practice? A survey at northern Germany hospitals]

Hypothermia after out of hospital cardiac arrest should be clinical practice for years. But is it really meanwhile daily trained practice? A survey at northern German hospitals gives an answer to this question.

Small Volume Resuscitation: A Randomized Controlled Trial With Either Norepinephrine or Vasopressin During Severe Hemorrhage

BACKGROUND

The present study was designed to evaluate the effects of hypertonic-hyperoncotic hydroxyethyl starch solution (HHS) combined with either norepinephrine (NE) or arginine vasopressin (AVP) on cerebral perfusion pressure (CPP) and brain metabolism after hemorrhagic shock.

METHODS

Fourteen pigs were subjected to uncontrolled liver bleeding until hemodynamic decompensation followed by resuscitation using HHS (4 mL/kg) combined with either NE (bolus of 1000 microg; 60 microg/kg/hr; n = 7) or AVP (bolus of 10 U; 2 U/kg/hr; n = 7), respectively. Extracellular cerebral concentrations of glucose, glycerol, lactate, and the lactate/pyruvate ratio were assessed by microdialysis. After 30 minutes of therapy, bleeding was controlled by manual compression and all surviving animals were observed for 1 hour.

RESULTS

After hemodynamic decompensation, AVP resulted in a significantly higher increase of CPP (mean +/- SD; 47 +/- 19 versus 28 +/- 9 mm Hg; p < 0.01) and cerebral venous partial pressure of oxygen (66 +/- 8 versus 49 +/- 9 mm Hg; p < 0.05) compared with NE after 10 minutes of therapy. Hemodynamic data and blood gas variables were not different between groups during the remaining study period. Brain metabolism was found comparable in both groups at any time.

CONCLUSIONS

AVP was comparable to NE with respect to hemodynamics and blood gases, as well as brain metabolism in surviving animals throughout the study period. Our findings emphasize the importance of early resuscitation, as neuronal cell damage potentially starts immediately after onset of severe hemorrhage.

[The new 2005 resuscitation guidelines of the European Resuscitation Council: comments and supplements]

The new CPR guidelines are based on a scientific consensus which was reached by 281 international experts. Chest compressions (100/min, 4-5 cm deep) should be performed in a ratio of 30:2 with ventilation (tidal volume 500 ml, Ti 1 s, FIO2 if possible 1.0). After a single defibrillation attempt (initially biphasic 150-200 J, monophasic 360 J, subsequently with the respective highest energy), chest compressions are initiated again immediately for 2 min. Endotracheal intubation is the gold standard; other airway devices may be employed as well depending on individual skills. Drug administration routes for adults and children: first choice IV, second choice intraosseous, third choice endobronchial [epinephrine dose 2-3x (adults) or 10x (pediatric patients) higher than IV]. Vasopressors: 1 mg epinephrine every 3-5 min IV. After the third unsuccessful defibrillation attempt amiodarone IV (300 mg); repetition (150 mg) possible. Sodium bicarbonate (1 ml/kg 8.4%) only in excessive hyperkalemia, metabolic acidosis, or intoxication with tricyclic antidepressants. Consider atropine (3 mg) and aminophylline (5 mg/kg). Thrombolysis during spontaneous circulation only in myocardial infarction or massive pulmonary embolism; during CPR only during massive pulmonary embolism. Cardiopulmonary bypass only after cardiac surgery, hypothermia or intoxication. Pediatrics: best improvement in outcome by preventing cardiocirculatory collapse. Alternate chest thumps and chest compression (infants), or abdominal compressions (>1-year-old) in foreign body airway obstruction. Initially five breaths, followed by chest compressions (100/min; approximately 1/3 of chest diameter): ventilation ratio 15:2. Treatment of potentially reversible causes (4 "Hs", "HITS": hypoxia, hypovolemia, hypo- and hyperkaliemia, hypothermia, cardiac tamponade, intoxication, thrombo-embolism, tension pneumothorax). Epinephrine 10 microg/kg IV or intraosseously, or 100 microg (endobronchially) every 3-5 min. Defibrillation (4 J/kg; monophasic oder biphasic) followed by 2 min CPR, then ECG and pulse check. Newborns: inflate the lungs with bag-valve mask ventilation. If heart rate<60/min chest compressions:ventilation ratio 3:1 (120 chest compressions/min). Postresuscitation phase: initiate mild hypothermia [32-34 degrees C for 12-24 h; slow rewarming (<0.5 degrees C/h)]. Prediction of CPR outcome is not possible at the scene; determining neurological outcome within 72 h after cardiac arrest with evoked potentials, biochemical tests and physical examination. Even during low suspicion for an acute coronary syndrome, record a prehospital 12-lead ECG. In parallel to pain therapy, aspirin (160-325 mg PO or IV) and in addition clopidogrel (300 mg PO). As antithrombin, heparin (60 IU/kg, max. 4000 IU) or enoxaparine. In ST-segment elevation myocardial infarction, define reperfusion strategy depending on duration of symptoms until PCI (prevent delay>90 min until PCI). Stroke is an emergency and needs to be treated in a stroke unit. A CT scan is the most important evaluation, MRT may replace a CT scan. After hemorrhage exclusion, thrombolysis within 3 h of symptom onset (0.9 mg/kg rt-PA IV; max 90 mg within 60 min, 10% of the entire dosage as initial bolus, no aspirin, no heparin within the first 24 h). In severe hemorrhagic shock, definite control of bleeding is the most important goal. For successful CPR of trauma patients, a minimal intravascular volume status and management of hypoxia are essential. Aggressive fluid resuscitation, hyperventilation, and excessive ventilation pressure may impair outcome in severe hemorrhagic shock. Despite bad prognosis, CPR in trauma patients may be successful in select cases. Any CPR training is better than nothing; simplification of contents and processes remains important.

Cerebral metabolism assessed with microdialysis in uncontrolled hemorrhagic shock after penetrating liver trauma

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of fluid resuscitation versus arginine vasopressin (AVP) combined with hypertonic-hyperoncotic hydroxyethyl starch solution (HHS) on cerebral perfusion pressure (CPP) and on cerebral metabolism using intracerebral microdialysis. Sixteen anesthetized pigs were subjected to uncontrolled liver bleeding until hemodynamic decompensation, followed by resuscitation using either fluid (n = 8) or AVP/HHS (n = 8). Thirty minutes after drug administration, bleeding was controlled by manual compression, and colloid and crystalloid solutions were administered in both groups. All surviving animals were observed for one hour. After hemodynamic decompensation, fluid resuscitation resulted in a smaller increase of CPP than did AVP/HHS (mean +/- sem; 24 +/- 5 vs 45 +/- 7 mm Hg; P < 0.01). Mean (+/- sem) cerebral venous partial pressure of oxygen was significantly decreased (P < 0.01) 5 min after fluid compared with 5 min after AVP/HHS administration (36 +/- 3 vs 64 +/- 4 torr). Cerebral metabolism was comparable in both groups. In conclusion, AVP/HHS proved to be superior to fluid in the initial phase of therapy with respect to CPP and cerebral oxygenation, but was comparable to fluid regarding cerebral metabolism and secondary cell damage in surviving animals.

Klinisches Management des schwierigen Atemwegs

Difficult airway management is among the key requirements in routine anaesthesia. Failures to secure the airways resulting in a "Cannot intubate, Cannot ventilate" situation can drastically increase morbidity and mortality of patients within a very short time. Therefore, an algorithm for management of the expected and unexpected difficult airway describing the sequence of various procedures, adapted to internal standards and to techniques that are available, has to be provided by each anaesthesia department. This not only facilitates the preparation of equipment and the training of personnel, but also ensures efficient decision making under time pressure.

Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE

Direct measurement of brain tissue oxygenation (PbtO2) is established during spontaneous circulation, but values of PbtO2 during and after cardiopulmonary resuscitation (CPR) are unknown. The purpose of this study was to investigate: (1) the time-course of PbtO2 in an established model of CPR, and (2) the changes of cerebral venous lactate and S-100B.

METHODS

In 12 pigs (12-16 weeks, 35-45 kg), ventricular fibrillation (VF) was induced electrically during general anaesthesia. After 4 min of untreated VF, all animals were subjected to CPR (chest compression rate 100/min, FiO2 1.0) with vasopressor therapy after 7, 12, and 17 min (vasopressin 0.4, 0.4, and 0.8 U/kg, respectively). Defibrillation was performed after 22 min of cardiac arrest. After return of spontaneous circulation (ROSC), the pigs were observed for 1h.

RESULTS

After initiation of VF, PbtO2 decreased compared to baseline (mean +/- SEM; 22 +/- 6 versus 2 +/- 1 mmHg after 4 min of VF; P < 0.05). During CPR, PbtO2 increased, and reached maximum values 8 min after start of CPR (25 +/- 7 mmHg; P < 0.05 versus no-flow). No further changes were seen until ROSC. Lactate, and S-100B increased during CPR compared to baseline (16 +/- 2 versus 85 +/- 8 mg/dl, and 0.46 +/- 0.05 versus 2.12 +/- 0.40 microg/l after 13 min of CPR, respectively; P < 0.001); lactate remained elevated, while S-100B returned to baseline after ROSC.

CONCLUSIONS

Though PbtO2 returned to pre-arrest values during CPR, PbtO2 and cerebral lactate were lower than during post-arrest reperfusion with 100% oxygen, which reflected the cerebral low-flow state during CPR. The transient increase of S-100B may indicate a disturbance of the blood-brain-barrier.

Monitoring of cerebral oxygenation with near infrared spectroscopy and tissue oxygen partial pressure during cardiopulmonary resuscitation in pigs

BACKGROUND AND OBJECTIVE

The present study was designed to compare cerebral oxygenation measured with near infrared spectroscopy and local brain tissue oxygen partial pressure, respectively, in pigs during cardiopulmonary resuscitation. Since tissue overlying the brain may have an impact on near infrared spectroscopy readings, we tested whether optode placement on intact skin or on the skull yielded comparable results.

METHODS

Twelve healthy pigs were anaesthetized and subjected to continuous haemodynamic, near infrared spectroscopy and brain tissue oxygen partial pressure monitoring. After 4 min of untreated ventricular fibrillation, cardiopulmonary resuscitation was started and arginine vasopressin was administered repeatedly three times. Near infrared spectroscopy values recorded were both the tissue oxygenation index and the tissue haemoglobin index as well as relative changes of chromophores (haemoglobin and cytochrome oxidase). Four animals served as control and were measured with both near infrared spectroscopy optodes mounted on the intact skin of the forehead, while in the remaining eight animals, one near infrared spectroscopy optode was implanted directly on the skull.

RESULTS

Near infrared spectroscopy readings at the skin or at the skull differed consistently throughout the study period. After arginine vasopressin administration, near infrared spectroscopy values at the different locations showed a transient dissociation. In contrast to near infrared spectroscopy measured on intact skin, near infrared spectroscopy readings obtained from skull showed a significant correlation to brain tissue oxygen partial pressure values (r = 0.67, P < 0.001).

CONCLUSION

Near infrared spectroscopy readings obtained from skin and skull differed largely after vasopressor administration. Near infrared spectroscopy optode placement therefore may have an important influence on the tissue region investigated.

Airway management in emergency situations

Securing and monitoring the airway are among the key requirements of appropriate therapy in emergency patients. Failures to secure the airways can drastically increase morbidity and mortality of patients within a very short time. Therefore, the entire range of measures needed to secure the airway in an emergency, without intermediate ventilation and oxygenation, is limited to 30-40 seconds. Endotracheal intubation is often called the 'gold standard' for airway management in an emergency, but multiple failed intubation attempts do not result in maintaining oxygenation; instead, they endanger the patient by prolonging hypoxia and causing additional trauma to the upper airways. Thus, knowledge and availability of alternative procedures are also essential in every emergency setting. Given the great variety of techniques available, it is important to establish a well-planned, methodical protocol within the framework of an algorithm. This not only facilitates the preparation of equipment and the training of personnel, it also ensures efficient decision-making under time pressure. Most anaesthesia-related deaths are due to hypoxaemia when difficulty in securing the airway is encountered, especially in obstetrics during induction of anaesthesia for caesarean delivery. The most commonly occurring adverse respiratory events are failure to intubate, failure to recognize oesophageal intubation, and failure to ventilate. Thus, it is essential that every anaesthesiologist working on the labour and delivery ward is comfortable with the algorithm for the management of failed intubation. The algorithm for emergency airway management describing the sequence of various procedures has to be adapted to internal standards and to techniques that are available.

A comparison of the proseal laryngeal mask airway, the laryngeal tube S and the oesophageal-tracheal combitube during routine surgical procedures

BACKGROUND AND OBJECTIVE

This study was performed to compare three supraglottic airway devices: the ProSeal laryngeal mask airway (PLMA), the laryngeal tube S (LTS) and the oesophageal-tracheal combitube (OTC) during routine surgical procedures.

METHODS

Ninety American Society of Anesthesiologists (ASA) I-III patients scheduled for routine minor obstetric surgery were randomly allocated to the PLMA (n = 30), the LTS (n = 30) or the OTC (n = 30) group, respectively. The overall success rate, insertion time, cuff pressures and resulting airway leak pressures were determined as well as a subjective assessment of handling and the incidence of sore throat, dysphagia and hoarseness were performed.

RESULTS

Insertion time until the first adequate ventilation was significantly (P < 0.0001) shorter in the PLMA (median 29 s; 25-75th percentile 25-48 s; range 10-161 s; success rate 100%) and in the LTS group (38 s; 30-44 s; 13-180 s; 100%) compared to the OTC group (75 s; 48-98 s; 35-180 s; 90%). In vivo cuff pressures and airway leak pressures increased with the inflating cuff volume in all devices and were highest in the OTC group. Postoperatively, patients in the PLMA and the LTS group complained significantly less about sore throat (P < 0.001 and 0.05) and dysphagia (P < 0.001 and 0.02) compared to the OTC group, while there was no difference regarding the incidence of hoarseness. Subjective assessment of handling was comparable with the PLMA and the LTS, but inferior with the OTC.

CONCLUSIONS

In conclusion, both PLMA and LTS proved to be suitable for routine surgical procedures and proved to be superior to the OTC which cannot be recommended for routine use.

Arginine vasopressin reduces cerebral oxygenation and cerebral blood volume during intact circulation in swine---a near infrared spectroscopy study

BACKGROUND AND OBJECTIVE

The aim of the present study was to investigate the impact of arginine vasopressin (AVP), a drug currently under investigation for use during cardiopulmonary resuscitation, on cerebral oxygenation and cerebral blood volume (CBV) in pigs with intact systemic circulation using near infrared spectroscopy.

METHODS

Nine healthy pigs were anaesthetized and subjected to invasive haemodynamic monitoring as well as to non-invasive determination (with near infrared spectroscopy) of changes in the Tissue Oxygenation Index (TOI is the ratio of oxygenated to total tissue haemoglobin), Tissue Haemoglobin Index (THI, representing CBV) and cytochrome oxidase (deltaCytOx, representing the balance of intracellular oxygen supply).

RESULTS

At both 3 and 5 min after AVP administration, TOI, THI and deltaCytOx were significantly (P < 0.001) reduced compared to baseline, while cerebral perfusion pressure increased significantly (P < 0.001). The effects of AVP on TOI and THI lasted longer than on deltaCytOx. There were no significant changes with respect to the intracranial pressure throughout the study period.

CONCLUSIONS

No improvement of cerebral oxygenation was detected after AVP administration in swine with an intact systemic circulation. In contrast to recently published investigations, AVP provoked a sustained drop in indices of cerebral oxygenation and CBV.

Changes of local brain tissue oxygen pressure after vasopressin during spontaneous circulation

BACKGROUND

Brain tissue oxygen pressure (PbtO2) correlates to cerebral blood flow (CBF) during spontaneous circulation, with one important regulator being nitric oxide (NO). Although it is established that arginine vasopressin (AVP) improves CBF and global cerebral oxygenation during cardiopulmonary resuscitation, it is unknown whether similar beneficial effects are present during spontaneous circulation. The purpose of this study was to investigate the effects of AVP with and without pre-treatment with the NO synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME) on local brain tissue oxygenation in a beating heart model.

METHODS

Following approval of the Animal Investigational Committee, nine healthy piglets underwent general anaesthesia, and were instrumented with a probe in the cerebral cortex to measure PbtO2. Each animal was assigned to receive AVP (0.4 U . kg(-1)), and after a wash-out period, L-NAME (25 mg x kg(-1) over 20 min) followed by AVP (0.4 U x kg(-1)). After each AVP administration, nitroglycerine (25 microg x kg(-1) over 1 min) as a NO donor was infused to test the vascular reactivity independently from NOS inhibition.

FINDINGS

Three minutes after administration of AVP, PbtO2 increased significantly (P < .05; mean +/- SEM, 31 +/- 11 versus 43 +/- 14 mm Hg, +39%), compared with baseline. After pre-treatment with L-NAME, the changes of PbtO2 after AVP were not significant (32 +/- 11 versus 28 +/- 10, -13%) when compared with the baseline.

CONCLUSION

In this beating heart porcine model, local brain tissue oxygenation was improved after AVP alone, but not after inhibition of NO synthesis with L-NAME.

Tracheal intubation using the Bonfils intubation fibrescope after failed direct laryngoscopy*

Failed tracheal intubation due to a difficult airway is an important cause of anaesthetic morbidity and mortality. This study was undertaken to evaluate the effectiveness of the Bonfils intubation fibrescope for tracheal intubation after failed direct laryngoscopy. Twenty-five patients undergoing coronary artery bypass grafting were enrolled in the study after two attempts at conventional laryngoscopy by a board certified anaesthetist had failed. Intubation with the Bonfils fibrescope was successful on the first attempt in 22 patients (88%) and on the first or second attempt in 24 patients (96%); in one patient intubation was impossible. Median (IQR [range]) time to intubation using the Bonfils intubation fibrescope was 47.5 (30-80 [20-200]) s. Tracheal intubation using the Bonfils intubation fibrescope appears to be a simple and effective technique for the management of a difficult intubation.

A comparison of the intubating laryngeal mask airway and the Bonfils intubation fibrescope in patients with predicted difficult airways*

Tracheal intubation with the intubating laryngeal mask airway or the Bonfils intubation fibrescope was performed in 80 patients with predicted difficult airways. Mallampati score, thyromental distance, mouth opening and mobility of the atlanto-occipital joint were used to predict difficult airways. The overall success rate, time to the first adequate lung ventilation and time taken for the successful placement of the tracheal tube were recorded, as well as a subjective assessment of the handling of the device and the incidence of postoperative sore throat and hoarseness. The median [range] time to the first adequate ventilation was significantly shorter with the intubating laryngeal mask airway than with the Bonfils intubation fibrescope (28 [6-85] s vs. 40 [23-77] s, p < 0.005). Tracheal intubation was significantly slower with the intubating laryngeal mask airway than with the Bonfils intubation fibrescope (76 [45-155] s vs. 40 [23-77] s, p < 0.0001. Patients in the Bonfils group suffered less sore throat and hoarseness than those in the other group.

Mechanical versus manual ventilation via a face mask during the induction of anesthesia: a prospective, randomized, crossover study

One approach to make ventilation safer in an unprotected airway has been to limit tidal volumes; another one might be to limit peak airway pressure, although it is unknown whether adequate tidal volumes can be delivered. Accordingly, the purpose of this study was to evaluate the quality of automatic pressure-controlled ventilation versus manual circle system face-mask ventilation regarding ventilatory variables in an unprotected airway. We studied 41 adults (ASA status I-II) in a prospective, randomized, crossover design with both devices during the induction of anesthesia. Respiratory variables were measured with a pulmonary monitor (CP-100). Pressure-controlled mask ventilation versus circle system ventilation resulted in lower (mean +/- SD) peak airway pressures (10.6 +/- 1.5 cm H(2)O versus 14.4 +/- 2.4 cm H(2)O; P < 0.001), delta airway pressures (8.5 +/- 1.5 cm H(2)O versus 11.9 +/- 2.3 cm H(2)O; P < 0.001), expiratory tidal volume (650 +/- 100 mL versus 680 +/- 100 mL; P = 0.001), minute ventilation (10.4 +/- 1.8 L/min versus 11.6 +/- 1.8 L/min; P < 0.001), and peak inspiratory flow rates (0.81 +/- 0.06 L/s versus 1.06 +/- 0.26 L/s; P < 0.001) but higher inspiratory time fraction (48% +/- 0.8% versus 33% +/- 7.7%; P < 0.001) and end-tidal carbon dioxide (34 +/- 3 mm Hg versus 33 +/- 4 mm Hg; not significant). We conclude that in this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during mask ventilation.

IMPLICATIONS

In this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and lower peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during face-mask ventilation.

Decreasing peak flow rate with a new bag-valve-mask device: effects on respiratory mechanics, and gas distribution in a bench model of an unprotected airway

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. The purpose of this study was to assess the effects of a newly developed bag-valve-mask device (SMART BAG), O-Two Systems International, Ont., Canada) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/cm H(2)O, airway resistance 4 cm H(2)O/l/s, lower oesophageal sphincter pressure 20 cm H(2)O and simulated stomach). Twenty nurses were randomised to each ventilate the manikin using a standard single person technique for 1 min (respiratory rate, 12/min) with either a standard adult self-inflating bag, or the SMART BAG. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG vs. standard self-inflating bag resulted in significantly (P<0.05) lower mean+/-S.D. peak inspiratory flow rates (32+/-2 vs. 61+/-13 l/min), peak inspiratory pressure (12+/-2 vs. 17+/-2 cm H(2)O), lung tidal volumes (525+/-111 vs. 680+/-154 ml) and stomach tidal volumes (0+/-0 vs. 17+/-36 ml), longer inspiratory times (1.9+/-0.3 vs. 1.5+/-0.3 s), but significantly higher mask leakage (26+/-13 vs. 14+/-8%); mask tidal volumes (700+/-104 vs. 785+/-172 ml) were comparable. The mask leakage observed is not an uncommon factor in bag-valve-mask ventilation with leakage fractions of 25-40% having been previously reported. The differences observed between the standard BVM and the SMART BAG are due more to the anatomical design of the mask and the non-anatomical shape of the manikin face than the function of the device. Future studies should remove the mask to manikin interface and should introduce a standardized mask leakage fraction. The use of a two-person technique may have removed the problem of mask leakage. In conclusion, using the SMART BAG during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate, peak inspiratory pressure, stomach tidal volume, and resulted in a significantly longer inspiratory time when compared to a standard self-inflating bag.

A new universal laryngoscope blade: a preliminary comparison with Macintosh laryngoscope blades

The Dörges universal laryngoscope blade has several features designed to facilitate tracheal intubation. The number of laryngoscope blades may be reduced from four to two, or even one, which indicate less space requirement and costs. This new universal laryngoscope blade, has a lower profile (height 15 vs. 22 mm) than a Macintosh laryngoscope blade size 3 and 4, which may facilitate manoeuvring of the laryngoscope in the mouth. In random order, 40 non-anaesthesia senior house officers used a Macintosh laryngoscope blade size 3 or 4 in an adult airway management trainer, a Macintosh laryngoscope blade size 2 in a paediatric airway management trainer, and the Dörges universal laryngoscope blade for both airway management trainers to perform orotracheal intubation. The number of intubation attempts and failures was counted. Participants reported the laryngoscopic view according to Cormack and Lehane. The time from touching the laryngoscope to the first adequate lung insufflation was measured, and subjective assessment regarding handling of both blades was recorded. Number of intubation failures, the laryngoscopic view according to Cormack and Lehane, and subjective assessment was comparable between groups. Orotracheal intubation of the adult airway management trainer with the Dörges universal laryngoscope blade took significantly less time compared to the Macintosh laryngoscope blades (14 (7-57) vs. 20 (8-43) s; P<0.001); all other intubating times were comparable. In conclusion, in this model, the Dörges universal laryngoscope blade was comparable to the Macintosh laryngoscope blades size 2-4, and may save time, cost and space.

Comparison of different airway management strategies to ventilate apneic, nonpreoxygenated patients

OBJECTIVE

Endotracheal intubation is the gold standard for providing emergency ventilation, but acquiring and maintaining intubation skills may be difficult. Recent reports indicate that even in urban emergency medical services with a high call volume, esophageal intubations were observed, requiring either perfect intubation skills or development of alternatives for emergency ventilation.

DESIGN

Simulated emergency ventilation in apneic patients employing four different airway devices that used small tidal volumes.

SETTING

University hospital operating room.

SUBJECTS

Forty-eight ASA I/II patients who signed written informed consent before being enrolled into the study.

INTERVENTIONS

In healthy adult patients without underlying respiratory or cardiac disease who were breathing room air before undergoing routine induction of surgery, 12 experienced professional paramedics inserted either a laryngeal mask airway (n = 12), Combitube (n = 12), or cuffed oropharyngeal airway (n = 12) or placed a face mask (n = 12) before providing ventilation with a pediatric (maximum volume, 700 mL) self-inflating bag with 100% oxygen for 3 mins.

MEASUREMENTS AND MAIN RESULTS

In three of 12 cuffed oropharyngeal airway patients, two of 12 laryngeal mask airway patients, and one of 12 Combitube patients, oxygen saturation fell below 90% during airway device insertion, and the experiment was terminated; no oxygenation failures occurred with the bag-valve-mask. Oxygen saturation decreased significantly (p <.05) during insertion of the Combitube and laryngeal mask but not with the bag-valve-mask and cuffed oropharyngeal airway; however, oxygen saturation increased after 1 min of ventilation with 100% oxygen. No differences in tidal lung volumes were observed between airway devices.

CONCLUSIONS

Paramedics were able to employ the laryngeal mask airway, Combitube, and cuffed oropharyngeal airway in apneic patients with normal lung compliance and airways. In this population, bag-valve-mask ventilation was the most simple and successful strategy. Small tidal volumes applied with a pediatric self-inflating bag and 100% oxygen resulted in adequate oxygenation and ventilation.