CNS Anaesthesia Flashcards
What is anaesthesia ? Types ?
Loss of sensation with out without loss of consciousness.
TYPES :
1)GENERAL ANAESTHESIA
2) LOCAL ANAESTHESIA
Spinal anaesthesia
Surface anaesthesia
Regiona anaesthesia
Nerve block anaesthesia
Infiltration anaesthesia
Principles of general anaesthesia
Reversible consciousness
Analgesia
Amnesia
Loss of external stimuli / loss of all reflexes
Adequate muscle relaxation
S/N pre anaesthetic medication
Pre- anaesthetic medication means using of drugs within last 24 hours of induction of anaesthesia for proper and safe anaesthesia.
Obj/ Purpose/ Role/ Pain
1) For analgesia = Morphine , fentanyl , Pethidine
2) To control vomitting = Inj . Ondansetrone , Inj Prochlorperazine
3)To reduce anxiety = Diazepam , Clonazepam , Midazolam
4) To reduce bronchial and salivary secretion = Inj. Atropine
5) To reduce gastric acid secretion = Inj PPI ( omeprazole , Pantoprazole)
6) To prevent infection = Inj cephalosporin ( Cefuroxime , Ceftriaxone)
7) For gut sterilization = glycerine sipp , enema , oral uria
8)To reduce allergic reaction = Inj antihistamine ( Dexamethasone , Chlorpheniramine )
Balanced anaesthesia
It is defined as the achievement of surgical anaesthetic state including unconsciousness with adequate analgesia and muscle relaxation with the help of various drugs and techniques .
Drugs = propofol , Pethidine , atracurium
Classify GA
I/V OR PARENTERAL GA
Barbiturate = Thiopental sodium
Ketamine
Propofol
Benzodiazepam = diazepam , Midazolam
Etomidate
Opoidal analgesic = morphine , Pethidine , fentanyl
INHALER GA
NO
Ether
Haloethane
Isoflurane
Enflurane
Desflurane
Sevoflurane
Methoxyflurane
Drugs used for induction of anaesthesia
Thiopental Na
Diazepam
Midazolam
Morphine
Pethidine
Fentanyl
Ketamine
Propofol
Drugs for maintainence of anaesthesia
NO
Haloethane
Isoflurane
Enflurane
Desflurane
Suxxamethonium
Pethidine/ morphine
Atropine
Properties of ideal anaesthesia
FOR THE PATIENTS
Should be pleasant , non irritating , induction and recovery should be fast , less emetic
FOR THE SURGEON
Adequate analgesia, immobility , muscle relaxant
Non inflammable
Non explosive
FOR THE ANAESTHESIST
Safe and effective
Easily available
Cost effective
Controllable and versatile
Less adverse effects
S/N thiopental Na
It is ultra short acting barbiturate
An injectable general anaesthetic drug
It is an ANAESTHETIC INDUCER
Highly lipid soluble
Produce unconsiousness within minutes ( less than 30secs)
Rapid recovery (5-10mins)
Quick muscle relaxant
Large and repeated dose needed
Necrosis and gangrene may occur due to extravastion.
A/E= laryngospasm , Hypotension , Apnoea , Shivering , Bronchospasm , Cough
S/N ketamine
I/V anaesthetic drug
Dissociative anaesthetic
ANASTHETIC INDUCER
It has analgesic action
Highly lipid soluble
May cause hallucination , illusion , increased CBF ,OP, HR,CO, BP
M/A of ketamine
Ketamine==> block membrane effect of glutamate ==> generalized CNS depression==> Anaesthetic action
A/E of ketamine
CVS = raised BP , HR, CO
CNS= 1)emergence delirium characterised by hallucination, vivid dreams, illusion
2) Markedly increases cerebral blood flow, oxygen consumption and ICP
3) Raised intraocular pressure
Indication of ketamine
GA in high risk patient
Children with cyanotic heart disease, minor surgery (circumcision)
Patient with shock , asthma
Cardiac catherization, opthalmic examination , radiotherapy
During large wound dressing
Sedation of asthmatic patient in ICU
Used as truth serum
Defn : local anaesthesia
Loss of pain sensation , loss of muscle reflexes and muscle relaxation in a localized area without amnesia and loss of consciousness.
What are the local anaesthetic drugs
Acc to chemical structure
ESTERS= procaine , Tetracaine , Cocaine , benzocaine //contains 1 i
AMIDES = Mepivacaine, Lidocaine , Bupivicaine, Ropivacaine
ACC TO duration of action
SHORT ACTING = Procaine , chloroprocaine
INTERMEDIATE ACTING = Lidocaine, Mepivacaine , prilocaine
LONG ACTING = Bupivacaine, Ropivacine , Tetracaine
M/A of lidocaine
Lidocaine ==> Blocks voltage gated Na channel ==> Blocks depolarization ==>No action potential ==>No transmission of pain sensation ==>Local anaesthesia action
Clinical uses of LA/ Lidocaine
N-G Tube intubation
Catheterisation
Boil and abscess drainage
Stitching of local cut injury
Circumcision
Dressing of burn and wound
Tooth extraction and Root Canal Treatment
Caesarean section (spinal)
A/E of lidocaine
CVS = BLOCK CARDIAC NA+ CHANNEL WHICH CAUSES :
Decrease cardiac pacemaker activity
Decrease excitability
Decrease rate of conduction
CNS = sleepiness
Restlessness
Tongue numbness
Nystagmus
Muscular twitching
NEUROTOXICITY
HEMATOLOGICAL = patient become cyantoic and blood becomes chocolate colored
Allergic reaction
A/E of lidocaine
CVS = BLOCK CARDIAC NA+ CHANNEL WHICH CAUSES :
Decrease cardiac pacemaker activity
Decrease excitability
Decrease rate of conduction
CNS = sleepiness
Restlessness
Tongue numbness
Nystagmus
Muscular twitching
NEUROTOXICITY
HEMATOLOGICAL = patient become cyantoic and blood becomes chocolate colored
Allergic reaction
Why adrenaline is used with lidocaine
Adrenaline ===> causes local vasoconstriction===> decrease blood flow ===> delayed absorption of lidocaine / xylocaine ===> prolongation of xylocaine /lidocaine / local anaesthetic action
Mention rationale use of combination of Haloethane and nitrous oxide
Mixture of Haloethane and nitrous oxide are more effective for most anasthesia
Quick onset and rapid recovery action
Combination reduces the drug conc up to 1/3
Respiration and circulations are better maintained by these combinations
Combination has good analgesic and muscle relaxation action
