Module 3D: specific inhalation anaesthetics Flashcards
Give the characteristics of Nitrous oxide
MAC: 105% + reduces MAC of other agents
Potent analgesic, poor anaesthetic
Induction is pleasant and raoid
What are the adverse effects of Nitrous oxide?
negatively inotropic
Augments respiratory depression of other drugs
diffuses into air-filled cavities
PONV
Bone marrow suppression
When does diffusion hypoxia occur?
finish an anaesthetic using N2O in high concentration
How does diffusion hypoxia occur?
N2O enters alveoli from the blood faster than N2 enters blood from alveoli. Reduces partial pressure of O2 in alveoli
what are volatile anaesthetics?
halogenated hydrocarbons including:
Halothane, isoflurane, sevoflurane, and desflurane
Give characteristics of halothane?
MAC: 0.75%
halogenated hydrocarbon
non-irritant
pleasant smell
suitable for gas induction
Pharmacodynamics of halothane?
CNS: potent hypnotic, increased CBF and ICP
CVS: myocardial depression + vasodilation, decreased BP, arrythmias
Resp: dose dependent resp depression, bronchodilator
Skeletal muscle: muscle relaxation, triggers MH
Uterus: decreases tone
Liver: increased liver enzymes post op, halothane hepatitis
Characteristics of isoflurane?
MAC: 1.14%
Halogenated ether
Pharmacodynamics of isoflurane
CNS: least effect on ICP(decreased CMRO2 and CSF production)-> ideal for neurosurgery
CVS: vasodilator, drops BP, tachycardia
Resp: irritant to airways, NOT SUITABLE FOR GAS INDUCTION
Skeletal muscle: triggers MH, potentiates NDMR
Uterus: relaxes
Liver: low potential for toxicity
Characteristics of sevoflurane?
MAC 2%
Very pleasant smell
best gas for induction
expensive
rapid onset and offset
Pharmacodynamics of sevoflurane?
CNS: Increased CBF and ICP, decreased CMRO2-> good for neurosurgery
CVS: mild depression of cardiac contractility, slight drop in BP
Respiratory: dose-dependent depression
Skeletal muscle: adequate muscle relaxation for intubation
Liver no increased enzymes
renal: nephrotoxic endproducts like fluoride and compound A
Characteristics of desflurane?
MAC 6%
Very expensive
most rapid induction and emergence of all volatiles
very irritant and pungent
Emergence delirium common
What is malignant hyperthermia?
triggered by all volatiles and suxamethonium which leads to ABNORMAL calcium receptors in muscle-> hypermetabolic state
Signs of malignant hyperthermia?
Tachycardia (and other CVS signs)
Hypercapnia (increased end-tidal CO2 x3 ↑ )
Tachypnoea (if not paralysed)
High temperature (late sign)
Skeletal muscle rigidity
ABG: mixed metabolic & respiratory acidosis
Treatment of malignant hyperthermia
DANTROLENE iv and supportive care in ICU
