LO 13 - Part 1 GA Flashcards
Anesthetics & Nitrous Oxide
Describe general anesthesia
Reversible loss of consciousness AND insensitivity to painful stimulation
What are the 3 goals of balanced general anesthesia?
- Good patient control
- Adequate muscle relaxation
- Pain relief
Contemporary techniques use balanced anesthesia using a combination of drugs to minimize ___________
adverse reactions
Under general anesthesia, the patient must be monitored constantly for_____________ and ______________ associated with general anesthesia
- respiratory depression
- loss of protective reflexes
List and describe the 4 stages of GA
- Stage I: analgesia - The patient is still conscious and can respond; The end of stage I is marked by loss of consciousness
- Stage II: delirium or excitement - Stage begins with loss of consciousness and is associated with involuntary movement and excitement; Emesis (vomiting) and incontinence (defecation) can occur; This stage is very uncomfortable for the patient
- Stage III: surgical anesthesia - This is the stage in which most major surgery is performed - can be as long as needed based on predicted length of surgery
- Stage IV: respiratory or medullary paralysis - Characterized by complete cessation of respiration and circulatory failure; Pupils are maximally dilated, and blood pressure falls rapidly; If this stage is not reversed immediately, the patient will die; Respiration must be artificially maintained
When balanced anesthesia is used, the patient will go through but skip the symptoms of this stage
Stage 2
Provide the modern description of GA stages
- Induction: all preparation and medication up until the operation begins, including preoperative medications, adjunctive drugs to anesthesia, and anesthetics required for induction
- Maintenance: begins with depth of anesthesia sufficient for surgery and continues until the completion of the procedure
- Recovery: termination of the procedure until the patient is fully responsive
What 3 components of GA drugs address the 3 goals of balanced GA?
- Opioids: Fentanyl - alleviates pain
- Benzodiazepine: Valium - puts patient to sleep
- Succinylcholine - relaxes muscles
What is the mechanism of action for GA drugs?
Potent CNS depressants - can lead to adverse reactions
List the adverse reactions of GA drugs
- CNS depression
- CVS: cardiac arrest, ↓ BP, arrhythmias
- Respiratory: decreased resp rate, Respiratory arrest
- Hepatotoxicity
- Teratogenicity
- Infertility and abuse (Even operators who are breathing in things like nitrous, and their spouses, regularly can have infertility issues)
- Other: headache, fatigue, irritability
Describe GA drugs that are inhaled
- Nitrous oxide (N2O)
- Min. Alveolar Concentration (MAC) - ↑MAC/ ↓ potency
- Volatile Liquid: halothane, enflurane (Ethrane - common)
Describe minimal alveolar concentration (MAC)
- It is the equivalent of ED50 but for gasses
- The term minimal alveolar concentration (MAC) is used to compare potency of general anesthetic inhalation agents
- MAC is the defined as the minimum alveolar concentration of anesthetic at 1 atmosphere required to prevent 50% of patients from responding to a supramaximal surgical stimulus
- MAC of nitrous oxide > 100; MAC of isoflurane is 1.15
- Lower MAC values indicate a more potent anesthetic
- Volatile anesthetics are given in combination with nitrous oxide to reduce the concentration of each while improving MAC values
What are the physical properties of N2O (Inhaled drug)?
- Colourless/odourless (makes it difficult to detect leaks)
- Fast onset
- High MAC/low potency (MAC > 100)
- Unsatisfactory as a GA when used alone
Describe the pharm effects of N2O (Inhaled drug)?
CNS
1. sedation
2. analgesia
3. amnesia
4. decreased sensory input except auditory
CVS
1. Peripheral vasodilation (common of all nitrogen drugs)
GI
1. nausea, vomiting
2. empty stomach is preferred before treatment
3. large meal at least 3hrs after
What is N2O used for?
- light sedation
- anxiety relief with some analgesia
- in combination with other meds in G.A. to produce balanced anesthesia
What are the advantages of using N2O
- rapid onset
- easy administration
- fast recovery
- easily accepted
- relaxed dental team
What is important to remember when using N2O
- need to monitor pt closely @ all times
- doesn’t substitute for behavior management for kids
- good scavenger system is required - air evacuation system
- Fail-safe system: automatic shut down if O2 runs out - need to give 100% oxygen to pt. At end of appt.
Describe the mechanism of deliver for N2O
- Note: O2 tank has the colour green while N2O tank has the colour blue
- Start with 100% O2 2-3mins
- slowly introduce N2O @ 5% increments (avg. 35% adults) range 10%-50%
- onset ~ 3-5mins
- Look for client responses
Describe client responses to N2O
- slow, slurred speech
- slow but responsive motor movements
- relaxed – cooperative client
- euphoria is reported - don’t want to provide enough to get this response
- can maintain open mouth in desired plane
- eyes can be closed but open easily
- vitals: within normal limits at all times
Describe client recovery from N2O
- End with 100% O2 for 5mins per each 15min of treatment => 45min treatment requires 15mins O2
- If inadequate O2 results in → Diffusion Hypoxia “severe headaches” How to prevent it?
List N2O contraindications
- Respiratory obstruction - a cold, COPD, asthma
- Emotional Instability - Sexual abuse?? - people sometimes believe abuse happens during nitrous, but security video says differently
- Pregnancy - The incidence of spontaneous abortion or miscarriages is higher in female operating personnel chronically exposed to anesthetic agents or in wives of male operators
- Teratogenicity - why it should not be used on pregnant people
List the adverse reactions of N2O
- Dizziness, headache, tachycardia, syncope, and hypotension
- Nitrous oxide impairs the ability to drive or operate heavy machinery
- With chronic use(Abuse) psychologic (not physical) dependence develops.
Describe the sensations that cause N2O abuse
- Inhalation of 50% to 75% produces a “high” for 30 seconds followed by a sense of euphoria and detachment for 2 to 3 minutes
- Tingling or warmth around the face, auditory illusions, slurred speech, and a stumbling gait can occur
Describe the long-term effects of N2O abuse
- Chronic mental dysfunction
- Infertility
- Neuropathy and Myeloneuropathy (impact on smooth muscles) - Initial symptoms include loss of finger dexterity and numbness or paresthesia of the extremities
- Decrease in B12
- Decrease in kidney/ liver function
