Plus-Hex CLINICAL inspired concentrations of 70 – 80 %. However , this may not be tolerated in the patients who often need it the most , such as stressed cats and brachycephalic dogs .
As the feline larynx is prone to laryngospasm when touched , it should be desensitised with lidocaine before intubation .
A veterinary-specific spray ( Intubeaze ; Dechra ) is formulated with 20 mg / ml lidocaine and delivers 2 – 4 mg per spray ( 0.1 – 0.2 ml ), which should be applied uniformly over the larynx . This dose is typically safe for most adult cats but care should be taken not to exceed 4 mg / kg in small cats and kittens [ 28 ] , which is 1 – 2 sprays per kilogram of body weight .
Xylocaine spray should be avoided as it can cause laryngeal oedema due to its carrier agent , and up to 10 mg can be delivered with each spray [ 29 ] . Benzocaine should not be used as it causes methaemoglobinaemia [ 30 ] .
If a veterinary-specific spray is not available , then injectable 2 % lidocaine ( without adrenaline or preservatives ) can be drawn up into a 1 ml syringe and 1 – 2 drops ( 0.1 ml , or 2 mg ) applied to the vocal cords .
Adequate time should be allowed for the full desensitising effect of lidocaine – typically 30 – 60 seconds [ 2 ] but sometimes up to 90 seconds [ 31 ] – with flow-by oxygen provided during this time . This delay in securing the patient ' s airway is tolerated in healthy patients , but less so in patients that are respiratory compromised .
Gentle intubation should be attempted during inspiration when the vocal cords open , but repeated attempts or trying to push through a closed larynx should be avoided .
Although not routinely used in veterinary medicine , a neuromuscular blocking agent may facilitate intubation without laryngospasm [ 32 ] .
Ketamine preserves the laryngeal and pharyngeal tone and reflexes ( e . g . swallowing ) and may cause a laryngospasm during the intubation process , but the likelihood of this occurring is decreased when it is combined with a benzodiazepine [ 33 ] .
Patients with BOAS typically have an elongated soft palate , everted saccules and tonsils , and laryngeal collapse , which can make it challenging to see the larynx . The use of a second laryngoscope during intubation can move some of this soft tissue from view , as shown in Figure 15 .
Intubation is a contributing risk factor to anaesthesiarelated morbidity and mortality , which doubles in feline anaesthesia , emphasising that greater care is needed with airway management during anaesthesia recovery [ 34 ] .
Figure 15 . A second laryngoscope blade being used to lift the soft palate to aid in viewing the larynx .
Extubation considerations
In recovery , the patient should be positioned in sternal recumbency with the head supported and the ETT cuff still inflated . In dogs , when they have started to swallow and demonstrate airway control or no longer tolerate the ETT , the cuff can be deflated and the ETT removed .
In cats , extubation should be performed before swallowing . The topical lidocaine applied to the larynx for intubation has a duration of action of 15 minutes [ 31 ] , so the larynx is likely to have become resensitised by the end of the procedure . A strong palpebral blink or ear flick when stimulated is a sufficient indicator that extubation can be performed .
Although it is desirable for the ETT to remain in place as long as possible to maximise oxygenation and airway patency ( especially in brachycephalic patients ), delayed extubation can cause GOR [ 35 ] . If this occurs , either before recovery or at the time of recovery , the head should be lowered to allow the contents to drain from the mouth , suctioned if possible , and cleared of GOR material [ 36 ] . Lavage with saline or tap water will clear the oesophagus of the acidic gastric contents , which can cause inflammation and may lead to oesophageal structure formation . Even extubation with a fully inflated cuff does not remove all the fluid in the proximal trachea , so the potential for aspiration and pulmonary damage remains [ 37 ] .
In brachycephalic breeds , the ETT should be left in place until it is no longer tolerated by the patient . After extubation , the head should remain supported and the tongue pulled forward to open the airway . A roll of tape or bandage wedged between the canines or incisors can be used as a gag to keep the mouth open .
Volume 38 ( 3 ) • June 2023
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