Flashcards in Chpt. 6 - Key Points Deck (23):
Define local anesthesia
The use of a chemical agent on sensory and motor neurons to produce a temporary loss of pain sensation and movement.
Why may local anesthesia be preferred to general anesthesia?
It may preferred in some patients because of:
- low patient toxicity
- low cost
- minimal recovery time
Local anesthesia disadvantages
- Lack of patient restraint
- Risk of overdose in smaller patients
- Technical difficulties
Define sympathetic blockade and what it does to the body
Sympathetic blockade may occur, if sufficient quantity of local anesthetic reaches the sympathetic ganglia.
This causes flushing, increased skin temperature, and, occasionally, hypotension and bradycardia.
Name some of the topical uses of local anesthetics
- Application to the conjunctiva
- Application to the epithelium of the respiratory or urogenital tracts
Local anesthetics injected in proximity to a peripheral nerve do what?
Blocking sensation from the tissues served by the nerve. (surgical preparation of the area is necessary before injection of a local anesthetic)
Epinephrine added to lidocaine
- delays absorption of the local anesthetic agent from the site
- do not use epinephrine at peripheral locations where blood supply may be compromised
Define epidural anesthesia
- injecting local anesthetic in the epidural space, between the dura and the vertebrae (in dogs and cats, between the last lumbar vertebrae and sacrum)
- useful for surgical procedures in debilitated PTs
- useful in PTs requiring profound analgesia of the caudal abdomen, limbs, or pelvis
What is useful for distal limb Sx (incl. amputation)?
Intravenous injection of local anesthetics
What happens if local anesthetics are injected into a nerve?
- may be harmful
- may cause temporary paresthesia, resulting in self-mutilation
Adverse systemic effects of local anesthesia
- respiratory depression
- sympathetic blockade
How to avoid local anesthetic toxicity
- limit the amount of lidocaine administered to PT (a maximum of 10 mg/kg in dogs given SQ)
- avoid IV injection of bupivacaine
Why use controlled or assisted ventilation?
- deliver oxygen and anesthetic to PT
- delivered by mechanical ventilator or manual bagging
- particularly useful in PTs with poor respiratory function
What does controlled or assisted ventilation help prevent?
- respiratory acidosis
- pulmonary atelectasis
How to perform intermittent mandatory manual ventilation?
- gently squeeze reservoir bag at a rate of 8-12 breaths/min and a pressure of 15-20 cm H2O
- inspiration time 1-1.5 seconds
- expiratory time at least 2-3 seconds
When is manual ventilation challenging and potentially dangerous to the PT?
If a nonprecision vaporizer is used
- may be incorporated into either a rebreathing or a non-rebreathing system
Depending on ventilator type, the anesthetist may control:
- the pressure or volume of gas to be delivered
- the respiratory rate
- the length of inspiration and expiration
If controlled ventilation is used, the anesthetist must use caution to avoid what?
- excessive expansion of the alveoli
- continuous positive pressure
- excessive ventilation rates
When to use and when NOT to use neuromuscular blocking agents
- may be useful in some anesthetic procedures to allow relaxation of voluntary muscles
- should NEVER be used as the sole anesthetic agent
Which neuromuscular blocking agents may be reversed, depolarizing or nondepolarizing?
Nondepolarizing neuromuscular agents may be reversed by the administration of NEOSTIGMINE or EDROPHONIUM.
Neuromuscular blocking agents may cause what systemic effects?
- Respiratory failure
~ Mechanical or manual ventilation must be available when these agents are used ~