General Anesthesia II, Introduction to General Anesthesia Flashcards
- General Anesthesia is:
Reversible process of depression of the central nervous system with drugs that produce unconsciousness
ideal anesthetic technique has these 3 components?
-loss of consciousness
-stability of systems
-analgesia
what is analgesia? are all anesthetics analgesics?
– Reduced or absent perception of pain
* Some anesthetics are analgesics; however not all anesthetics are analgesics
ADVANTAGES OF PRE-MEDICATION
- Sedation to facilitate handling of patient
- Lowers the dose of induction anesthetic drugs
- Lowers the dose of inhalational anesthetics
– Decreases MAC - Smooth induction
– Calm, non-anxious patient - Smooth recoveries
– If pre-medication drug(s) is still present in sufficient amounts in blood/tissues during recovery phase - ± Analgesia
common drug combos for induction?
– Diazepam or Midazolam + Ketamine
– Diazepam or Midazolam + Propofol or Alfaxalone
– Opioid + Benzodiazepine
* Need to be sick for this to work
– Propofol and Ketamine
– Inhalational anesthetic
ADVANTAGES OF INJECTABLE
INTRAVENOUS
Rapid induction
Rapid control of airway (intubation)
Rapid adjustments in depth of anesthesia
Smooth loss of consciousness
All Injectable routes:
No environmental pollution
Sophisticated equipment not required
DISADVANTAGES OF INJECTABLE
- Restraint required for IV administration
- Dependence on patient hepatic and renal function for metabolism and excretion
- Cardiopulmonary depression if administered inappropriately
– Requires knowledge and monitoring - Association of a prolonged recovery when used for the maintenance of anesthesia
– Exception- propofol & alfaxalone
INDUCTION WITH INHALANTS how does it work? what are the methods? what problems may arise?
- Deliver a high concentration from the start with a relative high O2 flow
- Deliver desired concentration in gradual increments with relative high O2 flow
– Odour of inhalant may cause aversion and struggling (excitement) - Isoflurane has strong odour
INDUCTION WITH INHALANTS how does it work? what are the methods? what problems may arise?
- Deliver a high concentration from the start with a relative high O2 flow
- Deliver desired concentration in gradual increments with relative high O2 flow
– Odour of inhalant may cause aversion and struggling (excitement) - Isoflurane has strong odour
ADVANTAGES WITH INHALANTS
- Lack of requirement of an intravenous access
– But there is a risk if problems arise - Rapid recovery with newer agents
– There is no requirement of metabolism or excretion of these drugs to terminate their effect
DISADVANTAGES OF INHALANTS
- Requirement of sophisticated equipment
- Significant cardiopulmonary depression when used at high doses
– Dilution of inhalant in the anesthetic system and uptake by the patient counteracts the delivered concentration - Excitement/discomfort
- Pollution
INTUBATION purpose and advantages
- Secures the airway
- Spontaneous or mechanical breathing
- Seals the airway with cuffed endotracheal tube
- Minimizes risk of aspiration
- LESS environmental contamination if using inhalant anesthetics
- Minimizes airway resistance
- Large diameter tubes IDEAL
- Maximize the inspired oxygen fraction
- Allows delivery of inhalant anesthetics
- Allows ventilation
DISADVANTAGES OF INTUBATION
- Damage to larynx
- Laryngospasm
– More likely in cat, sheep, pigs - Over-inflated cuff
– Compresses the tracheal mucosa and may cause ischemia - Long tubes
– May result in endobronchial intubation (one-lung ventilation)
GENERAL ANESTHESIA OPTIONS
Maintenance
1. Inhalational Anesthesia only
2. PIVA- partial intravenous anesthesia
3. TIVA- total intravenous anesthesia
what is PIVA- partial intravenous anesthesia
Combined use of inhalation and intravenous anesthetics to produce the desired degree of general anesthesia
what is TIVA- total intravenous anesthesia
Combined use of more than one intravenous anesthetic to produce the desired degree of general anesthesia
MONITORING DEPTH OF ANESTHESIA
Criteria used to describe and categorize the stages include:
- Ocular signs (palpebral, eye position)
- Degree of muscle relaxation, muscle reflexes, pain
- Respiratory depth and pattern
- Heart rate and blood pressure
- Pharyngeal and upper airway reflexes
