Table of content
1.1 Rationale, frequency and indication 5
1.2 Special features of out-of-hospital Emergency Anaesthesia 7
1.3 Preparations, Performance and Monitoring of Emergency Anaesthesia 9
1.4 Anaesthesia Procedures for Common Emergency Situations 14
1.5 Drugs for Emergency Anaesthesia 18
ARDS Acute Respiratory Distress Syndrome
AWMF Working Group of Scientific Medical Associations
BMI Body Mass Index
EAST Eastern Association for the Surgery of Trauma
EMS Emergency Medical Service
DGAI German Society of Anaesthesiology and Intensive Care Medicine
DIVI German Interdisciplinary Association for Intensive Care and Emergency Medicine
etCO2 End-tidal carbon dioxide
GCS Glasgow Coma Score
ICP Intracranial pressure
ICU Intensive Care Unit
LIKS AirRescue Information and Communication Systems
MIND German minimal emergency data record
NIBP Noninvasive Blood Pressure
NIV Noninvasive Ventilation
BP Blood Pressure (according to Riva Rocci)
SOP Standard operating procedure
SpO2 Oxygen saturation
TBI Traumatic Brain Injury
Emergency anaesthesia is an important therapeutic measure in out-of-hospital emergency medicine. The associated risks are considerably higher than those of in-hospital anaesthesia. The primary objectives of emergency anaesthesia are hypnosis, analgesia, oxygenation and ventilation through airway management. The secondary objectives of emergency anaesthesia are amnesia, anxiolysis, the reduction of oxygen consumption and respiratory work, the protection of vital organs and the avoidance of secondary myocardial and cerebral damage. A critical evaluation of the indications for out-of-hospital emergency anaesthesia must take into consideration patient, case and provider-related factors. Rapid sequence induction of emergency anaesthesia includes standard monitoring, preoxygenation, standardised preparation of emergency anaesthesia, drug administration, manual in-line stabilisation during intubation (if necessary), airway management and checking of correct tube placement. Spontaneously breathing casualties should receive preoxygenation for at least 3 to 4 min with a tight-fitting facemask with reservoir using 12 to 15 l min_1 of oxygen or with a demand valve providing 100% oxygen. As an alternative, preoxygenation may be performed as noninvasive ventilation with 100% oxygen. Standardised anaesthesia preparation comprises filling drugs into syringes and labelling them, checking ventilation equipment, preparing endotracheal tube and syringe for inflating the cuff and the introducer, stethoscope and fixation material, preparing alternative instruments for airway management as well as checking suction, ventilation and standard monitoring devices, including capnography. Standard monitoring for out-of-hospital emergency anaesthesia comprises ECG, blood pressure measurement and pulse oximetry. Continuous capnography is always and exclusively performed to check the placement of airway devices, as well as to indirectly monitor haemodynamics.
1.1 Rationale, frequency and indication
Emergency anaesthesia, airway management and ventilation are important therapeutic measures in emergency medicine.1,2 In physician-based emergency medical service (EMS) systems, every EMS-physician – irrespective of his or her specialty – should be able to safely induce emergency anaesthesia in patients with various injury patterns, clinical pictures and risks despite adverse conditions outside the hospital.3 This leads to the question of what procedure should be recommended for out-of-hospital anaesthesia under complex conditions and what anaesthetic drugs should be used, especially with regard to different groups of patients. It must also be taken into consideration that the induction and performance of out-of-hospital anaesthesia is in many respects more difficult than routine anaesthesia in operating theatres or ICUs in hospitals.4,5
The following recommendations of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI) have been prepared for EMS-physicians and paramedics in two-tier physician-staffed EMS systems. Table 1 shows a list of the central points of these recommendations.
The recommendations contain measures based on the latest scientific findings, which ensure the appropriate provision of out-of-hospital emergency anaesthesia for critically ill or injured patients under various circumstances (e.g. infrastructure, specific situation, patient condition, individual capabilities, knowledge and experience of the physician).
To achieve consensus on scientific findings and current practice of out-of-hospital emergency anaesthesia the Emergency Medicine Research Group of the DGAI invited 14 anaesthesiologists experienced in out-of-hospital emergency medicine from German and Austrian medical centres to participate in an Out-of-Hospital Emergency Anaesthesia Working Group. After constructing a frame of contents, single topics were distributed to teams of authors to review relevant literature and provide a first version of the text.
In a second step, these results were assembled and a three-round digital Delphi study was conducted to reach consensus.
The Delphi technique is a structured approach of debating by experts to converge a discussion towards group consensus, which was initially developed in the 1950s for complex problems exceeding the analytical capabilities of a single person.6
Working group opinion was fed back after each Delphi round to allow the participants to revise their previous opinions and so converge towards group consensus. Recommendations were approved with consensus when agreement of 12 out of 14 participants (> 85%) could be reached.
According to the German minimal emergency data record data base (82 000 ground deployments of emergency physicians) of Baden-Württemberg, Germany, and the AirRescue Information and Communication Systems data base (47 000 air rescue missions, Germany), every emergency physician induces out-of-hospital anaesthesia every 2 weeks in air rescue missions and every 1.4 months in ground deployments.7 Out-of-hospital anaesthesia is induced in approximate 3 to 5% of all EMS missions and in 4 to 7% of EMS missions to children (age <18 years).8–12
1.1.4 Indications for emergency anaesthesia
Emergency anaesthesia must often be induced in unconscious (Glasgow coma scale, GSC <9), uncooperative, severely injured or critically ill patients with a full stomach and unstable cardiopulmonary conditions.13 Emergency anaesthesia is, in most cases, necessary for airway management. An exception to this rule are patients undergoing cardiopulmonary resuscitation who require airway management first and, if necessary, emergency anaesthesia later once spontaneous circulation has returned.14 Indications for emergency anaesthesia can be found in critically ill or injured patients with cardiopulmonary or neurological diseases, trauma patients, and patients who are intoxicated or have markedly impaired conscious level with a reduction in protective reflexes (GCS < 9) and a high risk of pulmonary aspiration.15,16 This does not include rapidly reversible causes of impaired consciousness (e.g. hypoglycaemia) or conditions in which the GCS does not correlate with the extent of the loss of protective reflexes (e.g. stroke with aphasia or dementia). Patients with markedly impaired consciousness (GCS < 9) require emergency anaesthesia to tolerate airway management.17Tables 2 and 3 provide an overview of the indications for and objectives of out-of-hospital emergency anaesthesia.
If emergency anaesthesia is required, personnel must take into account the guideline on out-of-hospital airway management18 by the DGAI as well as the information on emergency anaesthesia, airway management and ventilation in the German S3 guideline on treatment of major trauma (S3-Guideline on Treatment of patients with severe and multiple injuries. German Trauma Society. 2011 www.awmf.org Nr. 012-019 Assessed 29 September 2015). Indications for, planning of and performance of emergency anaesthesia are influenced by the following factors:
- Training, experience and routines of the emergency physician and paramedics
- Out-of-hospital environment (e.g. illumination, space, weather)
- Time and type of transport (ground, air ambulance)
- Circumstances surrounding airway management and (foreseeable) intubation problems (e.g., expected difficult airways of emergency patients with sufficient spontaneous breathing).
The EMS-physician must not only consider the situation of the patient but must also critically assess his own skills when deciding to perform out-of-hospital emergency anaesthesia. Emergency anaesthesia is an invasive measure, poses a lethal risk, places special requirements on performance, monitoring and complication management. Before inducing emergency anaesthesia, the EMS-physician must consider disadvantages and possible complications (e.g. vomiting, pulmonary aspiration, airway displacement, cardiovascular depression, allergic reaction) and analyse the risks and benefits. In addition, the skills of the EMS-physician and the paramedics as well as relevant team factors must also be considered. Unlike junior hospital doctors, EMS-physicians usually cannot request direct support from a medical specialist or a senior physician. Several incidents have been reported in which severe complications were caused by a lack of experience in out-of-hospital emergency anaesthesia.19 Mistakes are easily made by inexperienced personnel. Guidelines and standard operating procedures must define clear procedures to provide less experienced emergency teams with a standardised approach to out-of-hospital anaesthesia. Given the life-threatening risks for the patient, it is crucial that all EMS-physicians know the procedures for inducing and performing out-of-hospital anaesthesia. The Association of Anaesthetists of Great Britain and Ireland requests that physicians inducing out-of-hospital anaesthesia ‘... should have the same level of training and competence that would allow them to perform unsupervised ...’ emergency intubation ‘... in the emergency department’.7,20,21
1.2 Special features of out-of-hospital emergency anaesthesia
Emergency anaesthesia induced in the ICU, in the emergency department, and especially outside the hospital is associated with a high level of difficulty.1,4,22 According to Timmermann et al.18, these multifactorial risk-increasing conditions can be categorised as physician, patient and case-related factors.
1.2.1 Patient-related factors
Patient-related factors complicating the induction and performance of emergency anaesthesia include a full stomach, injury of the airway, restricted mobility of the cervical spine (preexisting, on account of trauma or immobilisation), cardiopulmonary or other disorders because of preexisting diseases and/or injuries, a poor venous state and long-term medication.
Full stomach: Out-of-hospital emergency patients must be assumed to have a full stomach. To reduce the risk of aspiration in adults, rapid sequence induction is the technique of choice. This involves rapid anaesthetic induction and airway management without intermittent ventilation. This has a considerable influence on the choice of anaesthetic. The DGAI Paediatric Anaesthesia Scientific Working Group recommends intermittent ventilation in paediatric patients to avoid hypoxia during rapid sequence induction.23
Difficult vascular access: If possible, early insertion of two peripheral venous catheters is recommended during out-of-hospital anaesthesia in critically ill or severely injured patients to always have a second access available during induction (e.g. in case of extravasation).24 If peripheral venous cannulation is difficult, anaesthetics may also be administered through intraosseous access.25,26 All drugs mentioned below may be administered through intraosseous access using the same dose.
Haemorrhagic shock: Blood loss is underestimated in many patients (e.g. major trauma, internal haemorrhaging). Medical personnel must take into account that in such cases the number of red blood cells is critically reduced and patients must be carefully preoxygenated. Tests have shown that animals with severe haemorrhagic shock had oxygen saturation (SpO2) of less than 70% after only 1 to 2 min of apnoea despite preoxygenation.27 If emergency anaesthesia is induced in patients with severe haemorrhagic shock at the scene of the accident, sudden hypotension may occur, which is extremely difficult to correct.
1.2.2 Case-related factors
Position of the patient: Trapped patients or patients in a confined area should be treated first by inducing appropriate analgesia and sedation and by maintaining spontaneous breathing. Rescued patients should then be appropriately positioned for anaesthesia induction and airway management. The best conditions outside hospital can be provided in an ambulance car.28,29
Equipment constraints: Clinical physicians have a wide range of equipment, devices and drugs at their disposal. In an out-of-hospital environment, however, the selection of equipment and drugs is considerably limited.
Urgency: Depending on the condition of the patient, out-of-hospital anaesthesia must often be induced as quickly as possible. Medical personnel in an out-of-hospital environment must, therefore, have a high level of experience to ensure patient safety.
1.3 Preparation, performance and monitoring of emergency anaesthesia
On account of the risks and hazards of out-of-hospital emergency anaesthesia, standardised procedures are necessary to avoid complications. Personnel performing out-of-hospital emergency anaesthesia must, therefore, take the following points into consideration:
- Thorough evaluation and examination of the patient
- Critical verification of the indications for out-of-hospital emergency anaesthesia
- Optimisation of patient condition through preoxygenation, haemorrhage control and infusion (if necessary)
- Standardised procedures for the preparation and performance of out-of-hospital emergency anaesthesia
- Management of complications
1.3.1 Critical verification of the indications for out-of-hospital emergency anaesthesia
Information provided in sections 1.1.3 and 1.2 must be taken into account in this context. The decision to induce out-of-hospital anaesthesia must be communicated to the entire emergency team. The team must discuss the best location to induce anaesthesia, the tasks of each team member, the drugs selected and other important issues. A common approach must be agreed upon, which ideally is based on a standardised procedure.
1.3.2 Preparation of out-of-hospital anaesthesia
Rapid sequence induction is performed to induce emergency anaesthesia. The goal is to rapidly and effectively bring about a state of unconsciousness in which airway management and ventilation are tolerated. This procedure involves the administration of a sedative followed by muscle relaxant.13 Analgesic drugs may be administered prior to or immediately after these two substances or after the airway is secured. Ventilation must be ensured after anaesthesia induction. Drugs must be filled into syringes and labelled beforehand.30 Airway management equipment must be prepared and checked for functionality (Table 4).
1.3.3 Performance and procedure of out-of-hospital emergency anaesthesia
Table 5 and Figs. 1 and 2 provide an overview of the phases of out-of-hospital emergency anaesthesia.
After paramedics prepare the drugs and the equipment for airway management and ventilation as instructed by the EMS-physician, preoxygenation is initiated as soon as the EMS-physician decides to induce emergency anaesthesia (Fig. 1). To prevent desaturation during anaesthesia induction and airway management or to prolong the time until the oxygen saturation level decreases (apnoeic tolerance), spontaneously breathing emergency patients are given oxygen for 3 to 4 min, whenever possible.31,32 Preoxygenation must be performed only with 100% oxygen through a face mask or the tightly fitting bag valve mask, each with an oxygen reservoir (at least 12 to 15 l/min of oxygen). A demand valve or noninvasive ventilation (NIV) may be used, which are even more effective and require less oxygen.32 A face mask without reservoir is not sufficient for preoxygenation even at the highest possible flow rates.
During preoxygenation, optimal monitoring is ensured, and syringes are filled with anaesthetic and emergency agents according to the instructions of the emergency physician. Standard monitoring includes ECG (3-lead ECG: heart rate and rhythm), capnography, continuous automatic blood pressure (BP) monitoring (at least every 3 min), and pulse oximetry (heart rate and SpO2). The German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI) recommends the use of standardised self-adhesive syringe labels to avoid confusion in critical situations. (DIVI-recommendation for labelling syringes in intensive care and emergency medicine 2012
http://www.divi.de/images/Dokumente/Empfehlungen/Spritzenetiketten/DIVI-Etiketten-Empfehlung_2012_07_02.pdf, Assessed 16 May 2016)
To prevent regurgitation, the upper body should be elevated (but kept in line) if there is no contraindication (e.g. spinal immobilisation in trauma patients or a haemodynamically unstable patient).
After the venous accesses are checked, anaesthesia is induced according to agreed team approaches and procedures.
The paramedics confirm the names and doses of the drugs (in ml or mg) requested by the physician. The drugs are then administered. At this point, the cervical collar of patients with neck immobilisation is opened while ensuring manual in-line stabilisation provided by an assistant. After the patient has lost consciousness and the muscle relaxant has an effect, the airway is then secured. In adult patients, airway management is usually performed without intermittent ventilation. In some cases, intermittent ventilation may be necessary to maintain oxygenation despite the increased risk of aspiration (e.g. severe respiratory insufficiency).32,33 The application of cricoid pressure (Sellick's manoeuvre) is no longer recommended on account of a lack of evidence about its positive effects and because of potential problems at the tube site.33–35 The cuff of the endotracheal tube or the supraglottic airway (SGA) device (e.g. laryngeal mask, laryngeal tube) is inflated immediately after insertion, placement is confirmed and the device is fixed.
In out-of-hospital environments, two procedures are used to verify endotracheal tube placement for intubation36: visually via direct laryngoscopy or video laryngoscopy, and via capnometry/capnography. German standard DIN EN 1789 stipulates that all ambulances must have equipment for monitoring end-tidal carbon dioxide. This equipment must be used. Capnography provides vital information about ventilation and thus about the placement of the tube or SGA device. In addition, end-tidal carbon dioxide monitoring indicates acute changes in cardiac output earlier than other out-of-hospital methods. Continuous capnography also can detect the displacement, disconnection or kinking of the endotracheal tube. As unrecognised oesophageal intubation can have devastating consequences, correct tube placement must be confirmed using capnography (100% sensitivity). This does not, however, rule out over-insertion of the tube (endobronchial intubation). Bilateral breath sounds and chest movement can confirm the correct depth (measured from the teeth: women: approximately 20 to 21 cm, men: approximately 22 to 23 cm).37
Continuous standard monitoring must be ensured during the entire duration of anaesthesia to adequately monitor vital signs and respond to any changes.
1.3.4 Management of complications and problems
Out-of-hospital anaesthesia involves many risks. Complications must, therefore, be quickly identified and knowledgeably managed and eliminated.
Insufficient depth of anaesthesia: If laryngospasms or bronchospasms occur during induction or if the patient resists airway management, attempts to intubate must be interrupted. Anaesthesia must be deepened or muscle relaxants must be administered. Resistance, laryngospasms and bronchospasms usually cease once anaesthesia is deepened. Intermittent ventilation during rapid sequence induction in adults is possible as hypoxia is more dangerous than aspiration.
Hypotension: Temporary hypotension occurs in 7 to 18% of all cases of out-of-hospital anaesthesia.38,39Continuous automated oscillometric BP measurement is, therefore, vital. Patients with acute hypovolaemia have an increased risk of hypotension. Treat hypotension with fluids, cafedrine–theodrenaline, noradrenaline or, if necessary, adrenaline. The relevant drugs must be prepared before anaesthesia is induced. Fluid imbalances must be corrected through appropriate intravenous infusions. Heart failure should also be considered as a differential diagnosis, particularly in patients who have preexisting conditions.
Allergic reactions: In rare cases, some drugs may release histamine and/or cause allergic reactions. In the event of allergic reactions, the usual treatment is to avoid or stop using the allergy-triggering agent and, depending on the reaction, administer glucocorticoids, H1/H2 antagonists, fluids and adrenaline (intravenously).
Bleeding in oral, nasal and pharyngeal cavities and aspiration: Out-of-hospital anaesthesia involves a 14 to 20% 12 higher risk of bleeding/secretions in oral, nasal and pharyngeal cavities as well as gastric-content aspiration than anaesthesia induced in hospital. When performing modified rapid sequence induction, personnel should have an operational suction device available at all times.
Hypoxia: In out-of-hospital anaesthesia, hypoxia occurs in 5 to 18% of all cases.38–40 Even short-term hypoxia increases mortality by a factor of 2.6 in patients with traumatic brain injury (TBI).41 In many cases, hypoxia persists over a longer period and incidence increases especially during rapid sequence induction.32 To ensure ideal conditions, the patient should be properly preoxygenated.40 Hypoxia may occur especially on account of failed or prolonged airway management.40
Limited mouth opening: Before anaesthesia is induced, it should be verified that the mouth can open sufficiently (width of two fingers, if possible). If the mouth does not open sufficiently, the indications for anaesthesia induction must be critically evaluated. If a mechanical problem is the cause of limited mouth opening, personnel may try to insert a SGA device. If this cannot be done quickly, the patient should be carefully ventilated through a mask as an interim measure. As a last resort, emergency cricothyrotomy must be performed (part of the ‘forward strategy’ below).18,42
Difficult airway management: Please refer to the DGAI recommendations for out-of-hospital airway management and other literature.18,42 In the operating theatre, the incidence of a life-threatening ‘cannot ventilate, cannot intubate’ situation is approximately 0.4%.43 This figure is much higher in out-of-hospital situations.5 These rare complications may lead to the death of a patient in a very short time.36 In clinical anaesthesia and during elective surgery, a return to spontaneous breathing is an option in such cases. This is rarely successful, however, even if succinylcholine has been used, which has a short duration of action.44 If muscle relaxation has been induced by rocuronium, sugammadex can be used for reversal (within 3 to 4 min), which is faster than spontaneous recovery from the effects of succinylcholine.45 This option remains theoretical only, however, and is not considered in the algorithms for out-of-hospital airway management and anaesthesia (‘forward strategy’).
The management of unexpected difficult airways in the out-of-hospital phase also follows the recommendation for out-of-hospital airway management of the DGAI.18 Apart from a proper assessment of tube placement, the stages of airway management escalate from mask ventilation to the use of SGAs, and, if required, surgical procedures to ensure sufficient oxygenation.
The best way to minimise the risk of an unexpected difficult airway is the early identification of patients who have difficult airways. For this reason, indicators of a difficult airway play a crucial role prior to induction of anaesthesia (Table 6). If several of these indicators are present, the induction of anaesthesia should be critically assessed. In some cases, a risk–benefit analysis will lead to the conclusion that anaesthesia must be avoided. Wherever possible, assistance should be requested or, if spontaneous breathing can be maintained, the patient should be transferred to a hospital notified in advance.36 A subjective inspection of patient physical characteristics helps experienced anaesthesiologists to assess a difficult airway.46 To obtain optimal intubation conditions in such cases, the authors recommend using a muscle relaxant when inducing anaesthesia, especially because a return to spontaneous breathing is only a theoretical option if the indication is correct (‘forward strategy’).
Alternative airway management options: The percentage of cases in which primary endotracheal intubation is not possible is significantly higher in out-of-hospital emergency medicine than in a hospital setting.39 As it can be assumed that out-of-hospital emergency patients have full stomachs, alternative airway management methods must be swiftly performed if primary intubation is not possible. It is essential to create optimal initial conditions (sufficient preoxygenation) and to use an introducer.36 The BURP (backward–upward–rightward pressure) manoeuvre and placing the patient in the improved Jackson's position with the patient's head elevated on a pillow causing an anterior movement of the skull (so called ‘sniffing position’), are two simple drug-free options for optimising the visualisation of the glottis.47 Although correct placement of the endotracheal tube can usually be achieved by making several intubation attempts, the risk of complications increases with each additional intubation attempt.48 If the glottic view is poor (according to Cormack/Lehane classification), personnel must check whether muscle relaxation has been induced. If not, this should be performed.
If endotracheal intubation is not possible, a quick and priority-oriented approach is necessary to prevent hypoxia and thus long-term damage to the patient18,36:
- Ensure oxygenation (target: SpO2 ≥ 90%); the first measure is careful mask ventilation, with two assistants if required, also for patients with potentially full stomachs
- If the laryngeal inlet is difficult to access, intubation catheters, if available, can be helpful in tracheal intubation.
- SGA devices (e.g. laryngeal mask, laryngeal tube) should be used if the vocal cord level is not visible; their early use reduces the complication rate in airway management.49
- Video laryngoscopes can be used to facilitate laryngoscopy. The success rate of video laryngoscopic intubation is described as high for the induction of anaesthesia in the operating room and in out-of-hospital settings,28,42 but the time needed to ensure airway management is sometimes longer, and lower success rates in nonstandard situations have been reported in some publications.50,51
- If the measures stated above should fail, emergency cricothyrotomy must be performed as a last resort to ensure sufficient oxygenation; the success rate and incidence of this procedure remain unclear, however.1
- All personnel performing these procedures must have sufficient practice, training and experience in the use of (airway) devices and their application.52
1.4 Anaesthesia procedures for common emergency situations
1.4.1 Severe trauma/major trauma
With respect to the induction and management of emergency anaesthesia, several important factors are encountered in major trauma patients:
- Adverse situations (e.g. patient trapped in vehicle, construction site)
- Difficult vascular access caused by hypovolaemia, hypothermia and vasoconstriction
- Latent/acute/peracute hypovolaemia caused by haemorrhaging with circulatory instability
- Lack of oxygen carriers with risk of hypoxia
- Injuries complicating airway management
Hypovolaemia/circulatory instability: Major trauma patients often have latent hypovolaemia caused by haemorrhaging. This hypovolaemia can initially be compensated for or concealed by compensatory mechanisms (primarily in healthy young patients) or long-term medication (e.g. β-blockers in elderly patients).53 As many anaesthetics have the side-effect of cardiovascular depression, significant hypotension may occur after the induction of anaesthesia. If latent hypovolaemia is likely, it is recommended that fluids be given prior to the induction of anaesthesia. As it has only a minor depressive effect on the circulatory system, ketamine is particularly suited for inducing emergency anaesthesia in obviously hypovolemic patients. Simultaneous use of catecholamines (e.g. 10 μg i.v. bolus dose of noradrenaline) may be necessary. Permissive hypotension (the tolerance of low normal BP levels) only applies to patients without TBI who have bleeding from noncompressible penetrating injuries. Recent studies have shown that mortality rates increase not only among patients with TBI but also among patients suffering from blunt trauma without TBI when SBP is below 110 mmHg.54
Reduced oxygenation: Trauma patients often exhibit haemorrhaging and reduced haemoglobin levels. In such situations, prehospital monitoring of oxygenation is suitable only to a limited degree, as pulse oximetry only measures levels of oxygenated haemoglobin. In order that physically dissolved oxygen can be used for the effective arterial oxygen content, major trauma patients should be ventilated with 100% oxygen until admission to the resuscitation room and subsequent arterial blood gas analysis in accordance with relevant guidelines. Respiration settings should comply with intensive medical requirements [maximum tidal volume: 6 ml kg−1 ideal body weight, initial respiratory frequency: 12 to 16/min, PEEP: 5 to 10 cmH2O (NB, Nota Bene: a tendency towards hypotension is associated with hypovolaemia as a result of reduced venous return), I : E ratio of 1 : 1 to 1 : 1.5].
Patient with cardiovascular failure: In general, there are two possible approaches for dealing with major trauma and haemodynamic instability:
- Approach 1: Titrated dosage of hypnotics in the lower range of the recommended dose to avoid further adverse effects on the cardiocirculatory stability of the major trauma patient but induction of anaesthesia under full relaxation.
- Approach 2: Ketamine-based anaesthetic, which does not depress circulation.
Both approaches require complete muscle relaxation, particularly in cases with concomitant TBI, to ensure optimum intubation conditions and to avoid intracranial pressure (ICP) peaks because of coughing or pressing. Both approaches have advantages and disadvantages. Although light anaesthesia always involves the risk of awareness, the use of ketamine increases the heart rate, BP and cardiac output (and thus the myocardial oxygen demand) of the patient.13 These considerations suggest that a mixed anaesthetic is the best choice. Table 7 shows a proposed standard procedure for inducing out-of-hospital emergency anaesthesia in cases of severe trauma (major trauma) and includes a selection of suitable anaesthetics.
1.4.2 Isolated neurotrauma, stroke, intracranial bleeding
Emergency anaesthesia is necessary for airway management in patients with isolated neurotrauma, a stroke or intracranial bleeding, particularly against the backdrop of impaired states of consciousness associated with an increased risk of hypoxia and aspiration. Table 8 shows a proposed standard procedure for inducing out-of-hospital emergency anaesthesia in cases of isolated neurotrauma, stroke or intracranial bleeding and includes a selection of suitable anaesthetics. General procedures include elevating the upper body and immobilising the head in a neutral position. Appropriate BP management, normoventilation as well as the prevention of hypoxia, hypotension, coughing and pressing are important criteria for inducing anaesthesia in patients with isolated neurotrauma, a stroke or intracranial bleeding. Noradrenaline should be available for fractionated intravenous administration in 10 μg bolus doses during the induction phase and, if required, should subsequently be applied by a syringe pump.
Neurotrauma: As a surrogate parameter of cerebral perfusion pressure, BP is accepted as a decisive prognostic factor in cases of neurotrauma. Automatic BP monitoring at close intervals is required for this purpose. Although we are currently unable to specify exact BP target ranges, a SBP of 90 mmHg is considered to be the absolute lower limit.55 Even short phases below this critical limit can increase mortality in cases of neurotrauma. Significantly higher levels are more desirable, for example, an arterial mean pressure of 90 mmHg or a SBP above 120 mmHg.55,56
Stroke/intracranial bleeding: In an out-of-hospital environment, it is impossible to differentiate between cerebral ischaemia and bleeding. In the penumbra surrounding the infarction core, cerebral blood flow is reduced and autoregulation is ineffective. The survival of nerve cells thus directly depends on systemic BP, and drops in BP should be prevented by all means in the acute phase.57,58 A systolic target of 180 mmHg and a diastolic target of 100 to 105 mmHg are recommended for patients with preexisting hypertension. For patients without a history of hypertension, lower target values are recommended (SBP/DBP: 140 to 180/90 to 100 mmHg). Systolic values above 220 mmHg and diastolic values above 120 mmHg should be lowered carefully. 57,58 If signs of an ICP crisis (e.g. unequal pupils, Cushing reflex) persist after anaesthesia induction, an enhancement of anaesthesia (e.g. by thiopental or propofol bolus), administration of mannitol or short-term hyperventilation can be performed in accordance with the recommended guidelines.
1.4.3 The high-risk cardiac patient
Emergency anaesthesia may be necessary for a high-risk cardiac patient on account of acute cardiac failure (e.g. pulmonary oedema) or if a patient with a preexisting heart condition is involved in another emergency (e.g. trauma). If deterioration of oxygenation occurs (e.g. left ventricular failure with consecutive pulmonary oedema), the possibility of NIV under careful sedation must be considered for preoxygenation before anaesthesia is induced.32 Particularly in the event of deterioration of oxygenation, a spontaneously breathing high-risk cardiac patient should be extensively preoxygenated. Preference should be given to anaesthetics such as midazolam, etomidate, fentanyl and sufentanil that have little effect on the cardiovascular system (changes in inotropic state, preload and afterload; Table 9).59 High-risk cardiac patients often require catecholamines for circulatory support during anaesthesia induction and subsequently during the maintenance of anaesthesia when sympatho-adrenergic stimulation has ceased. Noradrenaline or adrenaline should be available for fractionated intravenous administration in 10 μg bolus doses during the induction phase and, if required, should be subsequently administered by a syringe pump.
1.4.4 Patients with respiratory insufficiency
There are many different reasons why patients with respiratory insufficiency may require out-of-hospital emergency anaesthesia. The underlying disorders comprise acute obstructions (e.g. asthma, COPD), acute oxygenation impairments (e.g. pulmonary oedema) and/or ventilation disorders (e.g. hypercapnia). Common risk factors in this group of patients are preexisting pulmonary and cardiovascular diseases, old age, nicotine abuse, a worsening general condition associated with a chronic course of disease and acute infections. If ventilation disorders are present, assisted ventilation (and possibly NIV) after appropriate analgesia and sedation (e.g. morphine) may be required during the preoxygenation and induction phases.32,60 Substances with a short onset time should be used for inducing anaesthesia (Table 10).31,61 Ideally, muscle relaxants should be used when inducing anaesthesia.62 It is advisable to induce deep anaesthesia using bronchodilatory/antiobstructive drugs (e.g. propofol, ketamine) that do not cause respiratory irritation, relax the smooth respiratory muscles, and do not lead to a release of histamines.63,64 Thiopental, atracurium, mivacurium and pancuronium should not be used on account of their side-effects.
1.5 Drugs for emergency anaesthesia
Depending on the location, a great variety of hypnotics, analgesics and muscle relaxants are stocked in rescue assets.65–67 When drugs are selected for inducing and maintaining anaesthesia, the physician's knowledge of handling these substances, their availability and pharmacological properties as well as patient characteristics should be considered. Drugs with optimum pharmacokinetic and pharmacodynamic properties for emergency anaesthesia are characterised by a fast onset, a short duration of action, minor/no haemodynamic effects, minor/no adverse effects and rapid reversibility.13 This article provides an overview of the drugs most commonly used to induce and maintain emergency anaesthesia. Particularly in cases of critically ill or severely injured patients as well as those with unstable cardiopulmonary status, any drugs used for anaesthesia should be administered carefully or titrated to effect to avoid undesired hypotension or cardiac decompensation up to cardiovascular arrest.
Propofol: Propofol (2.6-diisopropylphenol) has a purely hypnotic effect and has become the most commonly used hypnotic induction agent in hospitals.68 Apart from respiratory depression, propofol can also lead to a drop in BP owing to its negative inotropic effect and reduced peripheral vascular resistance (NB: reduction of cerebral perfusion pressure in case of TBI).69–71 These undesired effects are increased in hypovolaemic patients. Particular care should thus be taken when treating patients with cardiovascular insufficiency and/or hypovolaemia.68,72 Propofol is suitable for rapid sequence induction. This has, however, only been demonstrated in patients with stable circulation.72 Propofol is described as an alternative to barbiturate anaesthesia in controlling status epilepticus.73 Like barbiturates, propofol reduces cerebral blood flow and thus leads to a reduction in ICP, including in cases of isolated TBI. Owing to the narrow therapeutic range of propofol, its dosage depends on comorbidity and the opioid dose used. It should, therefore, only be applied by experienced physicians.68 Owing to the short half-life of propofol, repeated administration or alternative medication is required to maintain anaesthesia. Propofol infusion syndrome is not relevant to emergency medicine. Table 11 provides an overview of the most important characteristics of propofol.
Etomidate: Etomidate has a purely hypnotic effect. Haemodynamic stability and good intubation conditions are some of most convincing arguments in favour of using etomidate to induce anaesthesia.57 There are, however, numerous studies in which ketamine is rated as equivalent to etomidate in terms of intubation success and cardiovascular stability.74,75 Etomidate may cause both myoclonus and dyskinesia (NB: mask ventilation may be complicated; Table 12). Prior application of a benzodiazepine prevents myoclonus.
The significance of cortisol synthesis inhibition in the adrenal cortex and the associated increase in possible complications (e.g. acute respiratory distress syndrome, multiple organ failure, longer hospital stay, increase in ventilation days, longer ICU stays, higher mortality) is the subject of controversial discussion.76 The S3 guideline on treatment of major trauma/severe injuries and the revision of the S2k guideline on sepsis recommend that the use of etomidate should be carefully considered.77 In contrast, according to the American Eastern Association for the Surgery of Trauma guidelines, there is no evidence against the use of etomidate as an hypnotic induction agent.78 In light of unclear evidence and the principle of ‘primum non nocere’, one review does not recommend the use of etomidate, especially in septic patients.79
Given the side-effects described and their relevant impact on morbidity and mortality, which has not yet been conclusively determined, the authors believe that the use of etomidate can be completely abandoned in favour of other anaesthetic agents.
Midazolam: As a fast-acting benzodiazepine with a short duration of effect, midazolam possesses a wide therapeutic range in the treatment of anxiety, arousal and stress. Several studies showed no significant differences between midazolam and etomidate regarding intubation conditions and drops in BP during rapid sequence induction.80,81 Midazolam can thus be considered an equivalent alternative to etomidate as a hypnotic used to induce and maintain anaesthesia in trauma patients. In addition, midazolam has a significantly longer half-life than etomidate. Midazolam should, however, always be combined with opioids or ketamine.13Table 13 gives an overview of the most important characteristics of midazolam.
Thiopental: Thiopental is a barbiturate that has been used to induce anaesthesia in emergency medicine for many years (Table 14). This hypnotic agent is characterised by a quick onset and good reflex depression and depth of anaesthesia. Thiopental helps to reduce ICP (e.g. use in trauma patients with or without TBI). However, because of its vasodilator and negatively inotropic properties, thiopental may cause hypotension, particularly in patients with preexisting hypovolaemia. Volume management adjusted to the individual patient's condition is recommended as a preventive measure; vasopressors can be used to provide compensation. Another relevant side-effect that must be mentioned is thiopental-induced histamine release, which, in extreme cases, may lead to bronchial obstruction.
Fentanyl and Sufentanil are the opioids of choice in emergency anaesthesia. Different opioids have different degrees of analgesic, sedative and antitussive effects. The side-effects of opioids include respiratory depression, sedation, bradycardia, hypotensive cardiovascular disorders, emesis, pruritus, bronchospasm, sweating, spasms of the bile and pancreatic ducts, constipation and miosis. Once it has been decided to perform out-of-hospital emergency anaesthesia, there are no absolute contraindications. This also applies to the strict indication during pregnancy and nursing. Morphine or piritramide are not recommended for inducing anaesthesia.
Fentanyl: Fentanyl can be used for analgesia as well as anaesthesia induction and control. In small titrated doses, it can also be used for analgesia alone while the patient continues to breathe spontaneously (NB: close respiratory monitoring; Table 15).
Sufentanil: This opioid has the highest affinity for μ-receptors. Sufentanil can be administered both as a bolus dose and with a syringe pump (Table 16). However, it has not been approved for use as a pure analgesic without intubation anaesthesia. Its range of out-of-hospital applications is, therefore, limited.
Ketamine: Ketamine plays a special role in emergency medicine, as, depending on the dose, this substance can be used both for analgesia and for complete induction and maintenance of anaesthesia. Ketamine causes dissociative anaesthesia, which is associated with catalepsy, amnesia and analgesia. Depending on the dose, the patient's protective reflexes and spontaneous breathing are not affected. Adverse effects include arousal and nightmares, which makes concomitant medication with a benzodiazepine obligatory. Sensitivity to sound and hypersalivation may also occur. Particularly patients who are trapped or difficult to reach may benefit from analgesia and sedation based on ketamine and a benzodiazepine, because spontaneous breathing and circulatory stability are maintained in most cases. It should be noted that, apart from racemic ketamine, the S-enantiomer esketamine is available with considerably different dosage recommendations. The most important characteristics of esketamine are summarised in Table 17, those of ketamine in Table 18.
1.5.3 Muscle relaxants
Muscle relaxation is an integral part of rapid sequence induction and emergency anaesthesia management. Table 19 gives an overview of the advantages and disadvantages of muscle relaxation.
A short onset time is an important criterion when selecting a relaxant to induce anaesthesia. Rocuronium and succinylcholine are the only suitable drugs available.33 Succinylcholine is the most commonly used drug for this application (Table 20). However, hyperkalaemia (e.g. in patients who have been immobilised for more than 24 h and in patients with serious (burn) injuries) and malignant hyperthermia (e.g. predisposition) are relevant contraindications to the use of succinylcholine. The advantage of succinylcholine over rocuronium consists in its significantly shorter duration of effect and its lower price. As sugammadex has become available as an effective substance for blockade reversal, the prehospital use of rocuronium has been discussed in recent studies.29,61,82,83 So far, however, the data available is not sufficient to decide whether sugammadex must always be available when rocuronium is used in a prehospital setting. As rocuronium has a longer half-life, repeated prehospital administration is rarely required. The specific features of the other, nondepolarising muscle relaxants are summarised in Tables 21 and 22.
1.5.4 Storage instructions for emergency drugs
The need to refrigerate various drugs used for emergency anaesthesia is a particularly important aspect of storage precautions. Such drugs are labelled ‘Store in refrigerator’. This means storage at +2 to +8°C (refrigerator temperature). Drugs requiring cool storage can also be temporarily stored and transported at normal room temperature but their quality will deteriorate. Many manufacturers have conducted stability tests and provide recommendations on shelf life if continuous cool storage cannot be ensured. The following recommendations (Table 23) assume a normal room temperature of 25°C.
Acknowledgements related to this article
Assistance with the guidelines: these guidelines was approved by the presidium of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI) and acknowledged by the German Interdisciplinary Society of Intensive Care and Emergency Medicine (DIVI).
Financial support and sponsorship: none.
Conflicts of interest: BB is a member of the MSD Advisory Board. Travel allowance were granted by Weinmann EMT (to JTG, BH, CK), Storz (to BH), Verathon (to CK), O-Two Medical Technologies (to VW) and Ambu (to EP).
Presentation: these guidelines were previously published in German in the Journal Anästh Intensivmed 2015; 56: 2–19.
Note/Disclaimer: the authors have taken the utmost care to present the drugs and provide dosage recommendations. Manufacturers’ recommendations (technical information) on dosages, adverse effects and contraindications are nevertheless decisive.
Comment from the Editor: the editors of the European Journal of Anaesthesiology were informed by the authors that the guidelines had been published previously in German. The guidelines were checked and accepted by the editors of the European Journal of Anaesthesiology but did not undergo external peer review. The European Society of Anaesthesiology (ESA) was not involved in the development of these guidelines and did not endorse them. BWB is an associate editor of the European Journal of Anaesthesiology.
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