Issues of critical airway management (Which anesthesia; which surgical airway?).

Which anesthesia for patients with critical airway? Safe and effective analgesia and anesthesia in critical airway is a skilled task especially after severe maxillofacial injury combined with head injury and hemorrhagic shock. If on one side sedation is wanted, on the other hand it may worsen the airway and hemodynamic situation to a point where hypoventilation and decrease of blood pressure, common side-effect of many opioids, may prejudice the patient's level of consciousness and hemodynamic compensation, compounding an already critical situation. What to do when endotracheal intubation fails and blood is trickling down the airways in an unconscious patient or when a conscious patient has to sit up to breathe? Which surgical airway in critical airway? Comparative studies among the various methods of emergency surgical airway would be unethical; furthermore, operator's training and experience is relevant for indications and performance.

INTRODUCTION

Anesthesia/analgesia for critical airway and choice of the most appropriate technique of emergency surgical airway are issues left to individual experience or institutional protocols. Following anecdotal experience with cases needing analgesia/anesthesia before an emergency surgical airway and a discrete personal experience with different aspects of critical airway management, suggestions as to safe and effective methods of analgesia/anesthesia and surgical airway are given.

Which anesthesia for critical airway?

Critical airway is a life-threatening scenario of hypoxemia about to become hypoxia, following failed or inadequate ventilation, where emergency surgical access must be obtained to avoid catastrophic consequences or death. The key indication is a scenario of impossible or inadequate ventilation. In the last two decades a new philosophy of airway control has been established that has shifted emphasis from mask ventilation to supraglottic ventilation with the introduction of supra-glottic ventilatory devices (SGVD). Protection from stomach contents aspiration is not guaranteed but the risk has been reduced with the introduction of extra channels for nasogastric tube (NGT) and endotracheal tube (ETT). Other drawbacks are oropharyngeal decubitus effects, decrease of lung compliance with increased airway resistance, and the need to be inserted in unconscious patient. SGVD obviate to cervical manipulations and can be used as a bridge during ETI attempts or by untrained or inexperienced personnel outdoor. SVGD are optimally placed for airway control outdoors in the instances where maxillofacial injuries cannot be intubated, with the added advantage of tamponading intraoral bleeding, and cervical spine injury (CSI) is certain or likely.[12] Combined with the right technique of continuous intravenous anesthesia, SGVD are invaluable presidiums in some scenarios of critical airway secondary to trauma. It is imperative therefore that any anesthetic or analgesic be titrated to response and for the required duration only. The agents used should have immediate effect on injection, be suitable for continuous intravenous infusion, nonetheless effective and safe with no effect on blood pressure and ventilation at physiological doses. These targets can only be met with a short duration rapid acting opioids in continuous intravenous anesthesia like alfentanyl and remifentanyl or drugs not depressing the cardiovascular and respiratory systems like ketamine.[3-5]

Two scenarios, personally encountered by the author, of maxillofacial trauma compounded by head injury, hemorrhagic shock and critical airway, epitomize with its potential pitfalls and caveat the challenge some patients with post-traumatic critical airway represent.[67]

The approach proposed as ideal management was retrospectively worked out by combining a SVGD with a method of total intravenous anesthesia extrapolated by a consolidated technique [Table 1].[8]

Table 1

Anaesthesia for critical airway

Scenario 1

It is the one of a patient being shot to the face, presenting with severe maxillofacial injury bleeding into the airways and outside, a neck collar for possible cervical spine injury (CSI), associated head injury with some deterioration of consciousness but still conscious, some degrees of hemorrhagic shock from oropharyngeal hemorrhage, and staying in obligatory sitting position in the attempt to relieve the dyspnea by avoiding the effect of deformity and blood on the breathing.[6] This type of scenario would require, in the author's view, in order: i) no face-mask ventilation but free high-oxygen concentration via high flow mask and reservoir bag kept near but at some distance over the face; ii) rapid iodine painting on anterior neck skin in preparation of a surgical airway - local anesthesia (LA) with lignocaine infiltration would risk confuse the landmarks! -; iii) the collar removed with the head kept carefully in manual-in-line-stabilization (MILS) on sitting/semi-sitting position by an assistant; iv) ketamine IV as bolus is then administered; v) once anesthesia is reached (fixed gaze plus a possible or spontaneous eye closure and miosis), the patient is rapidly positioned supine with MILS maintained and continuous intravenous anesthesia (CIVA) with infusion of ketamine or remifentanyl started up; vi) a diagnostic laryngoscopy (DL) is done to see the feasibility of a rapid endotracheal intubation (ETI) (visible laryngeal inlet and vocal cords (VC) or not, plus aspiration of blood debris and foreign bodies in the laryngeal inlet); vii) ETI is done; viii) if ETI not feasible due to deformity and view-obstructing debris and blood, a supraglottic ventilatory device like an intubating laryngeal mask airway (ILMA) Fast-Trach or C-Trach, or a laryngeal tube (LT) like a King LS II, should rapidly be inserted; ix) ETT is inserted through the SGVD; ix) a tracheostomy is then done if ETT cannot be inserted through the SVGD or done at some stage with the SVGD in situ before maxillofacial reconstruction. Insufficient ventilation or rapid deterioration during the above steps calls at any time for an emergency cricothyroidotomy (CTY), or tracheostomy if landmarks for CTY are obscured by swelling). Pulse oximeter and an arterial blood gas analyzer in perfect order should be at hand. No formal sedative or paralytic agent should be given to this type of patient until the airway is secured.

The preliminary steps ending with the sedation with ketamine should be explained to the patient in a reassuring/relaxed and cool confident voice and demeanor despite he or she may not be in enough concentration but in severe distress for the dyspnea, gurgling sounds and all the hectic and frantic preparations around that should be absolutely carried out in silence - "you will go to sleep now so I can put a tube in your windpipe for you to breathe better." To watch the patient breathing and taking a chance before intervening is a big error as deterioration and hypoxic damages are about to happen, likewise it is a big error to ventilate without looking first to retrieve and remove material in the upper airways that can be pushed inside the airways.

Scenario 2

Another extreme scenario is the one of an unconscious patient following blunt trauma to face and neck after car accident, who comes ventilated manually due to hypoventilation, manifesting indirect signs of impending upper airways obstruction, impalpable anterior neck landmarks, hypoxemia and severely bleeding massive facial injury, already supine and with a neck collar on for possible or suspected CSI.[7] Similar decision-making as above: do not face-mask ventilate; give oxygen by mask at distance from face; do DL; insert an ETT or a SVGD; if SVGD, try passing ETT through it; if ETI cannot be passed then obtain an emergency surgical airway (ESA) with SVGD in situ; ESA at anytime if rapid deterioration of SaO2 or patient incapable to be ventilated satisfactorily with SVGD.

Comments

In a cardiac or respiratory/cardiac arrest by upper airways obstruction there is no need for any analgesia or anesthesia.

Sedation or myoparalysis are also contraindicated in patients requiring a surgical airway who are still awake, breathing spontaneously and sitting to prevent or relief their hypoxemia in severe face and neck injury with respiratory compromise - a posture often observed also in patients with cardiac tamponade or post-traumatic diaphragmatic hernia.th

When analgesia is required in a conscious patient candidate for an ESA other than transtracheal or percutaneous transtracheal jet ventilation (TTJV/PTJV) or stab cricothyroidotomy, both feasible with simple LA infiltration, rapid onset induction agents and rapidly reversible anesthetic agents not interfering with spontaneous ventilation or blood pressure must be used for CIVA. Ketamine, remifentanyl or alfentanyl stat followed by continuous infusions are effective and safe drugs. The choice and dosages for the different anaesthetic drugs should be institutionalized in protocols ready to use. Combinations ketamine-opioid work well too.

In tachycardic patients with heart rate (HR) <120 bpm, alfentanyl, or ketamine, are the induction drugs of choice; in patients with coronary heart disease or HR ≥120 bpm ketamine is contraindicated. Alfentanyl would be then the most optimal induction agent as for its fastest onset of action, with remifentanyl the more optimal for CIVA due to its shortest half-life and rapid metabolism such as its effects terminate synchronously with termination of the infusion. Ketamine is a unique anaesthetic in that it does not depress myocardium, vasomotor and airways tone. For these reasons it has been successfully used in war-outdoors scenarios for CIVA[8] or as induction agent.[9] Despite being an excellent for induction and maintenance, nonetheless as analgesic and sedative, ketamine has the important side effect of increasing oxygen consumption (VO2) and heart rate (HR) in an organ, the heart, which is dependent on flow to increase oxygen delivery and at basic regimen extracts 75% (O2ER) of the oxygen delivered (DO2). Other side-effects of the classical racemic mixture are the occasional extrapyramidal signs, increased salivation and secretions in general, and the frequent hallucinations on emergence, which are all dose dependent and bufferable with a benzodiazepine like midazolam or diazepam and an antisialogue as anticholinergic that does not cross the blood-brain barrier and with the lowest psychotropic and chronotropic effects, namely glycopyrrolate.

Ketamine left isomer, (S+)-Ketamine, is to become the drug par excellence for anesthesia or sedation in critical illness due to the much superior analgesic power and much lesser chronotropic and neurotropic effects when compared to the racemic mixture.[10-12]

Midazolam should not be administered before airway control and normalized BP as for its cardiovascular and ventilatory depression effect, and only with a view to decrease extrapyramidal and neurotropic effects (hallucinations) of the racemic mixture. Any BP drop attributable to opioids can be managed by titrated Ephedrine. Laryngospasm attributable to ketamine or remifentanyl administration is counteracted by a short acting myorelaxant like suxamethonium. Glycopyrrolate should not be administered before airway control despite its potential benefits, due to the possibility of distracting the team of three from their respective tasks, not being an essential drug. Each second counts!

Fighting patients (agitated, confused and restless) with critical airway must be induced with ketamine, and so patients in obligatory sitting position and in severe shock.

As far as the techniques with ketamine, all PCT and some OST can be done under one ketamine induction dose whereas most OST require both induction and maintenance dosages of any combination proposed in Table 1.

Which surgical airway?

Despite the wave of enthusiasm accompanying percutaneous tracheostomy (PCT) in the last two decades,[13-17] there is no evidence that the closed technique is superior or more convenient than the open standard tracheostomy (OST) in election,[18-23] even less in emergency. Although it is acceptable for operators to use the techniques where they are more prone and acquainted in order to save lives, the corollary of all reliable comparative studies among the techniques in election done by teams of ear-nose-throat, maxillofacial or cardio-thoracic surgeons experienced in both procedures, is that OST is to be considered safer and preferable than PCT in emergencies.

Further considerations make OST the procedure of choice in critical airway.

The time factor is crucial for patients’ outcome during a ventilatory crisis and during a conversion from failed or complicated CTY or PCT to open tracheostomy in desperate situations. Although in trained hands PCT takes an average of 4-5 min, while the open technique is reported with a wider performance time between 5 and 15 min,[181924-27] in extreme emergency such a cardiac arrest (CA) or respiratory-cardiac (R-CA) arrest a PCT is not as fast as the open technique.[2829]

Only unquestionable advantage of PCT over the open technique is the aesthetic one, in view of the small incision (1-1.5 cm vs 4-4.5 cm). If the sequential method has a characteristic peril in the high risk of posterior tracheal wall penetration, the single dilator method has a high risk of anterior wall damage, risk diminished when the Griggs technique is used. Both Griggs and single dilator methods are now standard, being faster and simpler and with lesser complications rates than the original multi-dilators technique, due to the continuum control of pressure and stability in manouvering, a very important and crucial factor for success and safety.

The risk of complications is much lessened in the open technique, which allows positioning the tracheostomy centrally and in the most optimal space between second and third ring without unduly damage to the adjacent cartilaginous rings, and to be fashioned for a perfectly matching cannula.

The site and the centrality of the initial needle puncture/tracheotomy are crucial in avoiding complications. A0 plane of dissection not strictly on the midline inevitably provokes or accentuates peri-tracheal bleeding; a high/very high tracheotomy for its proximity to the larynx is a good recipe for laryngeal stenosis; a low tracheotomy causes decubitus of the cannula on the trachea during neck flexion/extension movements predisposing to fistulae; a not central ostomy with lateral decubitus of the cannula can damage the wall; an erroneous estimation of the depth of the trachea during maneuvering risks posterior wall damage; a lack of open vision risks to unduly damage the anterior tracheal rings; are the six mechanisms accounting for the complications of tracheostomies.[1330-35]

Other considerations make PCT unsuitable or contraindicated in emergency: it is impossible before procedure to predict the need of a long cannula in cases of deep trachea, problem easily solvable in the open situation; intraoperative and perioperative complications such as peritracheal and intratracheal bleeding, cannula malposition, cannula dislodgement, tracheal damage, airway loss with sudden fall of airways pressures and hypoxia[36] cannot be dealt with during the procedure without rapid conversion to OST. It follows that the technique cannot be recommended in CA or R-CA despite successful anecdotal cases.[28] The open procedure as a matter of fact represents the only possible treatment for CTY and PCT intraoperative complications. The vertical skin incision is preferred in emergency as well as in urgencies because makes the procedure safer, easier and faster.[29]

A semiopen tracheostomy (SOT) with 2-3-cm skin incision down to visualize the pretracheal fascia followed by a percutaneous method, is a valid alternative to OST.[37] SOT offers the best option in cases of cervical spine injury (CSI) with impalpable trachea. SOT requires less dissection, though at risk of not being able to control the occurrence of intraoperative complications,[8] and often the help of hookers and traction stitches, but it obviates to hazardous head/neck manipulations.

While PTJV and CTY, likewise ETT and SGVD, can be managed by a not medic, tracheostomies and improvised airway device (IAD) should be inserted only by medics. The trachea is a marvelous and unique piece of engineering, result of the necessity to combine semi-rigid flexibility and not collapsible property during neck movements. It is a relatively fragile and essential structure, witness of a unique metaphysical ideation for the vital function to equilibrate atmospheric pressure with the alveolar one. It must be handled with absolute care. Nevertheless it may occur in exceptional circumstances that it must be violated mercilessly in order to get life saving oxygen.[38] Virtually any IAD like any not collapsible cylindrical device e.g., a pen cover broken on the side of the conical tip end to avoid stenosis and inserted religiously centrally through a hole done with a simple pointed- edge knife rotated for 180-360 degrees suffices the purpose.

Advantages, scenario-indications, contraindications and disadvantages of the different methods are outlined in Table 2.[39-45]

Table 2

Pros and cons of surgical airways

The author's personal recommendations for ESA in critical airway are outlined in Table 3.[46-53]

Table 3

Recommendations on which ESA to use in critical airway

CONCLUSIONS

Analgesia/anesthesia for critical airway or during a situation of critical airway is a highly skilled task to be accomplished with sheer accuracy and a reasonable safety margin, due to the side-effects of anesthetic or analgesic drugs on airway and ventilation. Because of intrinsic difficulties in doing studies, perils of its implementation and rarity of requirement, protocols must be established before-hand and possibly studied in situations where an anesthetic is required with the patient kept breathing spontaneously. Safety and efficacy in those circumstances proves reliability of the method.

Following analog ethical and realistic considerations, specific indications, timing and type of emergency surgical airway can therefore only be given as result of axioms and corollaries, personal experience and reliable comparative studies among the techniques in election by specialist teams experienced in both techniques.