one lung vent, MH Flashcards
one lung ventilation is indicated for
thoracic surgery, VATS, trauma to chest, any approach passing through the chest (mediastinm, esophagus), or need to isolate a single lung (bleeding, infection, bronchopleural fistula)
one lung vent is most often accompanied by
pneumo
most used position for thoracic surgery
lateral ducubitus
dependent lung =
lower lung
non-dependent lung =
upper lung
axillary roll is placed on
upper chest wall (not in the axilla)
in the awake and lateral position the ____ lung is better perfused and ventilated
dependent
with induction of anesthesia, with a decrease in FRC, the ____ lung ventilates more
upper
why does positive pressure vent favor upper lung
it is more compliant
muscle paralysis favors vent of the ___ lung. why?
upper. due to abd contents pushing up more on the dependent hemidiaphragm
rigid bean bag hinders movement of dependent hemidiaphragm and favors ventilation of ___ lung
upper
open ptx of upper lung increases ___,favoring vent of ____
compliance, upper lung
the lower lung is ___ compliant in lateral decubitus
less
zone 1 upright
A a V
zone 2 upright
a A V
zone 3 upright
a V A
open pneumo causes a ____ shunt
large R to L intrapulmonary shunt (20-30%)
blood flow to the non ventilated = nondependent = upper lung is ___ by hypoxic pulm vasoconstriction
decreased
HPV ___ the r to l shunt
improves
surgical compression of the upper lung can __ blood flow, ____ the shunt
decrease, improves
3 main factors that inhibit HPV
hypocapnia, vasodilators, inhalation agents
factors that decrease blood flow to dependent lung
high mean airway pressures in ventilated lung from PEEP, hyperventilation or increased PIP, low FIO2, vasoconstrictors, intrinstic peep
CO2 elimination is usually not affected by one lung ventilation provided: (2 points)
minute ventilation is unchanged and preexisting CO2 retention was not present pre-op (COPD)
tidal volumes are kept roughly the same as two lung vent, around ___
10cc/kg. (may adjust due to changes in PIP, RR, altered to maintain normocapnia
ventilation can be stopped for short periods as long as
O2 is supplied more than consumption (250-300ml/min)
**during apnea PCO2 increases ___ mm for the first minute and then __ mm for each additional minute
5, 3
progressive resp acidosis limits apnea oxygenation technique for ___ min
10-20
hypoxia during 1 lung vent - want FIO2 of
.8-1
hypoxia during 1 lung vent - tidal volume
want 10cc/kg
hypoxia during 1 lung vent-adjust RR to keep PaCO2 at
40
hypoxia during 1 lung vent - add ___ CPAP to ___ lung
5, nondependent
which double lumen tube is most commonly used
left
complications of double lumen tubes
traumatic laryngitis, hypoxemia due to malpositioned tube, bronchial trauma from over inflation of cuff, inadvertent suturing of tube
what is MH triggered by
inhaled agents (not N20) and succs
which receptor is MH
ryanodine
first & most sensitive sign of MH
unexplained tachycardia
most specific sign
increasing ETCO2, hypercapnia, 2-3x
other signs of MH
decreased sat, muscle rigidity, dysrhythmias, tachypnea, cyanosis, sweating, unstable BP, mottling, trismus after succs, darkening of blood in surgical field, decreased mixed venous sat, cola colored urine, heating and exhaustion CO2 absorber, hyperthermia
labs of MH
increased K, ca, phos, CK. myogloinuria, hypoxemia
MH acid/base
initial metabolic acidosis then a combined metabolic and resp acidosis
genetic link of MH
familial autosomal dominant transmission with variable penetrance, on chromosome 19
treatment of MH o2
100% at high flows
drug/ dosing MH
dantrolene 2.5mg/kg asap then q5min until symptoms controlled or up to 10mg/kg total. must be mixed in sterile water.
what do you give for acid/base imbalance in MH
1-2meq/kg then check ABG
cooling measures for MH
iced IV NS 15cc/kg every 10min x3. cold body cavity lavage, cooling blanket, ice bags
treat hyperkalemia with
bicarb or dextrose 25-50g and regular insulin 10-20 units IV
treat persistent ventricular arrhythmias with
procainaminde 200mg IV
want urine output to be
> 2cc/kg/hr
lasix dose
.5-1mg/kb
mannitol dose
1g/kg
how long should you continue dantrolene
1mg/kg for 6-72h to prevent a recurrence
what drug should you not give with dantrolene
calcium channel blockers d/t life threatening hyperkalemia and myocardial depression
how does dantrolene work
inhibits ca release from the sarcoplasmic reticulum
how does dantrolene work intracellular
dissociation of excitation-contraction coupling
late complications of MH
renal failure, coagulopathies, pulm edema, cerebral edema, hepatic failure, left heart failure, DIC, skeletal muscle swelling,rhabdo,death
use ketamine and pancuronium with caution because
the tachycardia may mask early MH
is propofol benzos barbs narcs LA’s n2o, etomidate, ketamine, non-depolarizing agents safe during MH?
yes
*gold standard pre-op test ofMH
muscle biopsy with halothane-caffeine contracture test -78% specific and 97% sensitive
what syndrome is prom to MH
king-denborough syndrome
does a prior uneventful anesthetic rule out MH
no
Boys < 9 yrs old who experience sudden cardiac arrest after
succinylcholine in the absence of hypoxia should be treated
for
acute hyperkalemia
symptoms of MH usually occur after how long from exposure
one hour
