1.18 Hypotensive Anaesthesia Flashcards
Hypotensive Tecnhiques
Pre induction
Induction
Pre Induction
- Avoid anticholinergics that may precipitate tachycardia
- Premed
BZD/ Opiate
Analgesia / Anxiolysis / sedation
Induction -Smooth in calm environment - Procedures in a deep plan - dont use ketamine (or etomidate) - Avoid Panc for muscle relax (tachycardia) - Spray of cords at induction my prevent coughing on emergence - If approp use LMA avoids pressor response to laryngoscopy
Hypotensive Tecnhniques
Maintenance
Maintenance
- Volatile may produce hypotension
- Consider TCI prop remi (titration BP)
IPPV optimal PaCo2 level
- reduce sympathetic tone
PEEP can reduce preload
may cause venous HTN
Position ion
Elevation of operating field reduces venous bleeding
Reverse Trendelenburg position
-reduce RA Pressure + CO
Avoid central + peripheral venous obstruction
keeping head and limbs unobstructed + without tension
Drugs
Classified to affect
MAP = CO x SVR
CO
CO
Short acting beta bloq
negative inotropy + prevent compensatory tachycardia
SVR
Direct alpha
SVR
Reduce VSM = Drop BP
w/out reducing CO
Direct block of a2 adrenoreceptor
- Phentolamine short acting non selective alpha blocker
- Prazosin a1 blocker / slow onset
Clonidine
Centrally acting
selective a2 agonist (x200(
Initially increase bp follow peripheral a2 stim
then decrease via norad inhibition
Anxiolysis and analgesia aid effects
Labetalol
a and b adrenoreceptor block (1:7)
SVR indirect
Nitric oxide donor
direct VSM dilate
SNP - arterial
GTN - Increase venous capacity
increase venous compliance
reduce RA pressure
Hydralazine Direct acting vasodilator onset 15m cleared 1 hour fast acetylators precip SLE like crisis in slow
CCB - Nifedipine Vasodilator Ca antagonist Dilates vessels Prevents Tachycardia
Sympathetic chain blockade IV Trimetaphan 20-50mcg/kg/min Weak alpha block actions Direct vasodilator activity difficulty in titration
Contraindications
CVS disease
Resp Disease
Other
CVS disease
Any disease decrease perfusion may compromise organ function eg CVD / IHD / PVD
Severe Anaemia couple w/ Reduce CO
Tissue hypoperfusion
URx HTN
Labile BP w/ unpredictable response
+ Poor control
Difficult predict where
lower lim autoreg zones for core viscera
Resp disease
Vasodilators
abolish HPV
May increase physiological dead space
FRC
V/Q mm
Other
Diabetes
Sympathetic block = increase chance hypogly
Pregnancy
placenta flow perfusion dependent
Renal
May precip further deterioration in function
