临床麻醉学 英文版2.docx

1、临床麻醉学 英文版2CHAPTER 3Managing the AirwayBasic techniques, 37 The laryngeal mask airway, 42 Emergency airway Simple adjuncts, 39 Tracheal intubation, 43 techniques, 50 Maintenance of a patent airway is an essential prerequisite for the safe and successful conduct of anesthesia. In addition, during resu

2、scitation patients often have an obstructed airway either as the cause or result of their loss of consciousness. The skill of airway maintenance should be acquired by all doctors, and not simply regarded as the responsibility of the anesthetist. The descriptions of airway management techniques, whic

3、h follow, are intended to supplement practice either on a manikin or preferably on and anesthetized patient under the direction of a skilled anesthetist.Basic techniques Anesthesia frequently results in loss of the airway and it is most easily restored by a combination of the head tilt along with a

4、jaw thrust (see Chapter 2). The latter is provided by the anesthetists fourth and fifth fingers (of one or both hands) lifting the angle of the mandible. The overall effect desired is that the patients mandible is lifted into the mask rather than the mask being pushed into the face (Fig. 3.1).FACEMA

5、SKS The most commonly used type in adults is the BOC anatomical facemask (Fig. 3.2) which is designed to fit the contours of the face with the minimum of pressure. Leakage of anesthetic gases is minimized by an air-filled cuff around the edge. Masks ate made in a variety of sizes and the smallest on

6、e, which provides a good seal, should be used (to minimize the increase in dead space, which occurs). The Ambu mask (Fig. 3.2) has a transparent bodyallowing identification of vomit making it poplar for resuscitation. All masks must be disinfected between each patient.Simple adjuncts The most common

7、ly and used are the oropharyngeal (Guedel ) and nasopharyngeal airways, inserted after the induction of anesthesia to help maintain the airway in conjunction with the techniques described above.OROPHARYNGEAL AIRWAY These are curved plastic tubes, flattened in cross-section and flanged at the oral en

8、d, which lie over the tongue, preventing it from falling back into the pharynx. They are available in a variety of sizes from neonates to large adults. The commonest sizes are 2-4, for small to large adults, respectively. A guide to the correct size is determined by comparing the airway length to th

9、e vertical distance from the corner of the patients mouth to the angle of the mandible. It is initially inserted upside down as far as the back of the hard palate (Fig. 3.3a), rotated 180 (Fig.3.3b) and fully inserted util the flange lies in front of the teeth or gums in an edentulous patient (Fig.

10、3.3 c).NASOPHARYNGEAL AIRWAY These are round, malleable plastic tubes, beveled at the pharyngeal end and flanged at the nasal end. They are sized on their internal diameter in millimeters, with length increasing with diameter. The common sizes in adults are 6-8 mm, for small to large adults, respect

11、ively. A guide to the correct size is made by comparing the diameter to the external naris. Prior to insertion, the patency of the nostril (usually the right ) should be checked and the airway lubricated. The airway is inserted along the floor of the nose, with the bevel facing medially to avoid cat

12、ching the turbinates (Fig.3.4). A safety pin may be inserted through the flange to prevent inhalation of the airway. If obstruction is encountered, force should not be used as severe bleeding may be provoked. Instead, the other nostril can be tried.PROBLEMS WITH AIRWAYS The presence of snoring, indr

13、awing of the supraclavicular, suprasternal and intercastal spaces, use of the accessory muscles or paradoxical respiratory movement (see-saw respiration) suggest that the above methods ate failing to maintain a patent airway. Common problems arising using these techniques along with a facemask durin

14、g anesthesia are:1 inability to maintain a good seal between the patients face and the mask, particularly in those without teeth;2 fatigue, when holding the mask for prolonged periods;3 the risk of aspiration, due to the loss of upper airway reflexes;4 the anesthetist is not free to deal with any ot

15、her problems, which may arise.The laryngeal mask airway (LMA) or tracheal intubation may be used to overcome these problems.The laryngeal mask airway This device was designed for use in spontaneously breathing patients. It consists of a mask, which sits over the laryngeal opening, attached to which

16、is a tube, which protrudes from the mouth and connects directly to the anesthetic breathing system. On the perimeter of the mask is an inflatable cuff, which creates a seal and helps to stabilize it. The LMA is produced in a variety of sizes suitable for all patients, from neonates to adults, with s

17、izes 3 and 4 being the most commonly used in female and male adults, respectively. Positive pressure ventilation can be performed via the LMA provided that high inflation pressure is avoided, otherwise leakage occurs past the cuff, reducing ventilation and causing gastric inflation. Aversion with a

18、reinforced tube is also available. The LMA is reusable, provided that it is sterilized between each patient. The use of the laryngeal mask overcomes some of the problems of the previous techniques: it is not affected by the shape of the patients face or the absence of teeth; the anesthetist is not r

19、equired to hold it in position, avoiding fatigue and allowing any other problems to be dealt with; it reduces the risk of aspiration of regurgitated gastric contents, but does not eliminate it.Its use is relatively contraindicated where there is an increased risk of regurgitation, for example in eme

20、rgency cases, pregnancy and patients with a hiatus hernia. Recently, the laryngeal mask has been shown to be useful in two other areas:1 In difficult tracheal intubation where it will often allow maintenance of the airway. Alternatively, a small diameter tracheal tube or introduce can be passed into

21、 the larynx via the LMA.2 During cardiopulmonary resuscitation, it has been shown that non-anesthetists are able to insert an LMA more rapidly and successfully than a tracheal tube and achieve more effective ventilation than using a self-inflating bag and facemask. It is likely that in the future th

22、e LMA will find a role in airway management during resuscitation.TECHNIQUE FOR INSERTIONThe patients reflexes must be suppressed to a level similar to the required for the insertion of an oropharyngeal airway to prevent coughing or laryngospasm. The cuff is deflated and the mask lightly lubricated (

23、Fig.3.5a). A head tilt is performed, the patients mouth opened fully and the tip of the mask inserted along the lard palate with the open side facing but not touching the tongue (Fig.3.5b). The mask is then further inserted, using the index finger to provide support for the tube (Fig.3.5c). Eventual

24、ly, resistance will be felt at the point where the tip of the mask lies at the upper oesophageal sphincter (Fig.3.5d). The cuff is now fully inflated using an air-filled syringe attached to the valve at the end of the pilot tube (Fig.3.5e). The laryngeal mask is secured either by a length of bandage

25、 or adhesive strapping attached to the protruding tube.Tracheal intubationThis is the best method of providing and securing a clear airway in-patients during anesthesia and resuscitation, but success requires abolition of the laryngeal reflexes. During anesthesia, this is usually achieved by the adm

26、inistration of a muscle relaxant (see Chapter 4). Deep inhalational anesthesia or local anesthesia of the larynx can also be used, but these are usually reserved for use in those patients where difficulty with intubation is anticipated, for example in the presence of airway tumors or immobility of t

27、he cervical spine.COMMON INDICATIONS FOR TRACHEAL INTUBATION Where muscle relaxants ate used to facilitate surgery (e.g. abdominal and thoracic surgery ) thereby necessitating the use of mechanical ventilation. In-patients with a full stomach, to protect against aspiration of regurgitated gastric co

28、ntents. Where the position of the patient would otherwise make maintenance of the airway difficult, for example the lateral or prone position. Where there is competition between surgeon and anesthetist for the airway (e.g. operations on the head and neck). In those patients in whom the airway cannot

29、 be satisfactorily maintained by any other technique. During cardiopulmonary resuscitation when intubation allows:(a) ventilation with 100% oxygen without leaks;(b) suction clearance of inhaled debris;(c) a route for the administration of drugs.EQUIPMENT FOR TRACHEAL INTUBATIONA variety of equipment

30、 exists and that chosen will be determined by the circumstances and by the preferences of the individual anesthetist. The following is a list of the basic needs for adult oral intubation. Laryngoscope with a curved (Macintosh) blade and functioning light. Tracheal tubes in a variety of sizes and in

31、which the cuffs work. The internal diameter is expressed in millimeters and the length in centimeters. They may be lightly lubricated.(a) For males: 8.0 9.0 mm internal diameter, 22 24 cm lengths.(b) For females: 7.5 8.5 mm internal diameter, 20 22 cm lengths. syringe to inflate the cuff once the tu

32、be is in place. Catheter mounts or elbow to connect the tube to the anesthetic system or ventilator tubing. Suction, switched on and immediately to hand in case the patient vomits or regurgitates. Extras: a semi-rigid introducer to help mould the tube to a particular shape; Magills forceps, designed to reach into the pharynx to remove debris or direct the tip of a tube; bandage or tape to secure the tube.Tracheal tubes These were traditionally manufactured from red rubber and we