GA: Maintenance - Exam 2 Flashcards
Monitors to use during GA all the time:
-EKG, BP, SpO2
-temp (unless GA timing is <30min OR case <1hr)
Monitors used soemtimes for GA:
-O2/Agent conc
-NM block PNS checker
-BIS
-EtCO2
Get baseline VS in
PREOP
Which VS to get prior to induction:
EKG, BP, SpO2, precordial stethoscope?
Which VS ok to get after induction
-ArtBP, temp, SOUND ON FOR PLETH
Using senses in OR:
Sound: pleth, SUCTION, surgeon, pt
Vision: monitors, pt, skeletal muscle, surg field
Touch: temp, claminess, pulse, twitches
Precordial stethoscope benefits:
-immediate detection of circuit disconnect
-changes in lung sounds
-early detection of decreased Vt/RR in TIVA and MAC cases
-cheap, high reliability
Pulse Ox measure what
oxygenation
Capnography measures what
ventilation
Factors when using invasive monitoring:
-pt hx
-surg procedure
-EBL
Pros of permissive low EtCO2 (30-35)
-keeps HR + BP low
-no increase in cardiac O2 demand
-dec need muscle relaxants
-decreased hypnotic requirement
Cons of permissive high EtCO2 (45-50)
-HTN
-Tachycardia
-increased myocardial demand = ischemia
What is hypoxic pulmonary vasoconstriction?
natural response that causes vasoconstriction in alveoli that are hypoxic to avoiding having blood uselessly perfuse unoxygenated alveoli
Cons of permissive low EtCO2 (30-35)
-INHIBITS hypoxic pulmonary vasoconstriction which then leads to SHUNTING causing a LEFT shift in O2Hgb curve (O2 hangs onto Hgb more) in already compromised pt
-prolonged QTi, arrhythmia, decreased CO, decreased CBF, increased CMRO2
-DECREASED lung compliance (BC bronchoconstriction)
THIS IS WORSE THAN PERMISSIVE hypercapnia
Pros of permissive high EtCO2 (45-50)
-improved tissue oxygenation/perfusion
-quicker healing and less infection rate from more O2 delivered to surg site
-increased CO and vasodilation
-increased CBF
-mild resp acidosis improves lung function and prevents organ injury
BETTER THAN PERMISSIVE HYPOCAPNIA
When to avoid permissive hypercapnia (EtCO2 45-50)
-increased ICP -will increase CBF and raise ICP
-if CO2 gets too high can cause acidosis and make reversing muscle relaxants diffucult***
Temp impact on infection rate
2 degree difference in core temp can cause 3x higher rate of infection
Methods we control temp:
-bair hugger
-fluid warmer
-cover head
-raise OR temp
-headed humidification of gas
GA causes atelectasis by:
-paralyzing pt (reducing lung compliance)
-giving higher FiO2
-eliminating sign reflex
-absorption atelectasis (when O2 goes into capillaries faster than waste like nitrogen leaves into alveoli)
ARMs
-sustained inflation
-take pt off vent
-close APL a bit
-squeeze bag until peak pressure is 40cmH2O
-hold for 30-90sec
-some AGM can do this
ARMs
-incremental PEEP
-start of w/ PEEP you have
-incrementally increase PEEP to 20cmH2O then go back down but don’t turn off PEEP
O2 Hgb curve
-a pO2 of 60 would normally be
90%SaO2
O2 Hgb curve
-normal P50 value
26-27mmHg PO2
-PO2 in which 50% Hgb saturated (SpO2 =50%)
-loading onto Hgb isn’t affected by R or L shift in P50
-R or L shift DRASTICALLY affects O2 release from Hgb
O2 Hgb curve
-R shift meaning + causes
R shift =Higher P50 value so Hgb releases O2 to tissues more readily
Causes:
-acidosis (CO2 or H)
-HYPERcarbia
-HYPERthermia
-HIGH 2,3 DPG (from chronic hypoxemic or anemia)
-HIGH P50
-Hgb S(sickle cell)
O2 Hgb curve
-L shift meaning + causes
L shift=Lower P50 value so Hgb hangs on to O2 more
Causes:
-alkalosis
-HYPOthermia
-HYPOcarbia
-LOW 2,3 DPG (can be from older blood sitting in bank)
-Fetal Hgb
-methemoglobin
-CO
Why does pH affect O2 Hgb curve?
Bohr Effect
T/F Pt with CO poisoning will have SaO2 reflecting this
FALSE
-will appear falsely high
Methemoglobin
-ferric vs ferrous
Fe3+ is FERRIC
Fe2+ is FERROUS<- normal
-Hgb in ferrIC state will not bind with O2
Methemoglobin
-affect on OxyHgb curve
-will shift L, O2 not delivered to tissues
-SpO2 will look NORMAL
Methemoglobin
-causes
Nitrate poisoning (prolonged nipride gtt)
LA toxicity:
-procaine
-lidocaine
-benzocaine
-phenytoin
-sulfonamides
-METOCLOPRAMIDE
Methemoglobin
-s/s
clinical cyanosis and NORMAL SpO2
-falsely high Spo2
Methemoglobin
-tx
If MetHb is >20%:
-Methylene blue 1-2mg/kg over 5 min
-Ascorbic acid 2mg/kg
-Blood tx PRN
-Hyperbaric O2
NADPH METHEMOGLOBIN REDUCTASE causes enzymatic reduction of LEUCOMETHYLENE which reduces methemoglobin
Methemoglobin
-Methylene Blue MOA, CI
MOA: NADPH METHEMOGLOBIN REDUCTASE causes enzymatic reduction of the DRUG into LEUCOMETHYLENE which reduces methemoglobin
CI: in pts with G6PD deficiency (type of anemia that reacts to many meds causing hemolysis)
Methemoglobin
-Methylene Blue dosing
1-2mg/kg over 5 min
-if level still high after 1hr can repeat dose (MAX 7-8mg/kg /day)
-works quick and can cause rebound
1-2 or methylene blue
up to 7-8 if not looking great
What must be done after each position change?
Assess BS
When moving OR bed, always _ _
disconnect circuit
4-2-1 rule for fluid mgmt
- 4mL/kg for 1st 10kg
- 2mL/kg for 2nd 10kg
- 1mL/kg for every kg after first 20kg
Ex) 70kg pt= 40mL(4mL/kg) + 20mL(2mL/kg) + 50mL(1mL/kg)= 110mL/hr maintenance
Estimated NPO fluid deficit =
Maintenance fluid requirement * hours NPO
-give over 3 hr (1/2, 1/4, 1/4)
Ex) 70kg pt who fasted 6hr
70kg =110mL/hr (4-2-1) * 6 = 660mL deficit for 70kg pt after 6hr fast
So, Hr 1) 110 + 330mL=440mL Hr 2) 110+220mL= 330mL Hr3) 330mL <- JUST maintenance and deficit ONLY so far
Replacing surgical fluid losses
-superficial trauma (orofacial) = 1-2mL/kg/hr
-minimal trauma (herniorrhaphy) = 2-4mL/kg/hr
-moderate trauma (major nonabdominal or lap abdominal surg) = 4-6mL/kg/hr
-severe trauma (major open abdominal surg) = 6-8mL/kg/hr
Ex) pt having lap abdominal case 70kg taking 3 hr:
280-420mL/hr * 3 = 840-1260mL/hr (NOT INCLUDING MAINT + DEFICIT !)
Replace Crystalloid in _ ratio for blood loss
3:1 (3mL for every 1mL EBL)
(LR, 0.9, D5W)
Ex) Pt EBL was 1 lap sponge (150mL)
so give 450mL or ~500mL crystalloid(not including maint, NPO deficit, and surg losses**)
Replace Colloid or blood in _ ratio for blood loss
1:1
(albumin)
Release of ADH during stress/procedures so expect UO to _
decrease
Monitor + chart foley UO volume + characteristic Q
1hr
Measuring blood loss:
-ask whats in suction cannister (not all will be blood)
Sponges:
-4x4=10mL
-Raytech = 10-20mL
-Lap sponge 18x18 = 150mL
weighing sponge = 1gm = 1mL
Normal blood volume
-Premie
90-105mL/kg
Normal blood volume
-full term
80-90mL/kg
Normal blood volume
-infant
70-75mL/kg
Normal blood volume
-women
65mL/kg
Normal blood volume
-men
70mL/kg
Maximum allowable blood loss =
[Estimated blood volume * (Starting Hct -target Hct)] / starting Hct
Ex. 85kg woman w/ preop Hct 35%
EBV= 5525mL , starting Hct = 35, target Hct = 30
[5525*(35-30)]= 27625 then /35 = ~789mL allowable blood loss
-can use Hct or Hgb?
OR Linda method
-find EBV
-EBV x current Hct
-EBV x lowest Hct
-subtract those 2 numbers then x 3
What can measure how awake pt is?
BIS or entropy monitor
-not as reliable with opioids and certain induction drugs (ketamine, precedex)
BIS level indicating pt awake
95-100
BIS level indicating pt in anesthetic depth
40-60
-<60 likelihood of awareness/responsiveness to surgery is low
What is difference between deep sleep and anesthetic state?
differential in stimulus that rouses brain to conscious perception
Distinguishing stimuli that could rouse pt:
-intubation
-laryngoscopy
-rib retraction
-abdominal exploration
-incision
-closure
-electrical stim(TOF,etc)
-shouting/shaking
Suppression of response to different stimulus (easier->harder)
-verbal
-forming implicit/explicit memories
-purposeful movement
-ventilation
-pseudomotor responses (tearing, sweating)
-CV responses
comeback in reverse
Amnestic period after anesthetic dose (0.1-0.2mg/kg) is - hrs
1-2
Awareness most often happens during the _ phase and least on _
maintenance
emergence
T/F Amnesia is always necessary for GA
false, pt could ask for no amnesia, med hx could CI it, type of case, etc
IA and IV agents produce amnesia at doses significantly _ than those required for unconsciousness and immobility
LESS
-so if unconscious and unable to move SHOULD be ok..?
Ways to make sure your pt will not get up off the table and streak down the hall:
PNS for NMRD
-want ~2twitches
-cont infusion of NMBD?
-DON’T place DIRECTLY on muscle, want to monitor inhibition of NM receptor
-orbicularis recovers before adductor pollicis so use face 1st and elbow to recover
-check Q 15 min
Things you want ready when waking pt up:
-mask/syringe
-reversal agent
-post op pain med
-anti emetic
-OPA + tongue blade
T/F It is not ok to prep for next case while you are caring for another pt
false, just DON’T TURN BACK ON THEM
Scan:
-Pt
-Surg area
-VS
-Vent (Vt, pressure ,FiO2, settings)
When to NOT take a break:
-key moments (intubation/emergence)-leads to error
Things to mention in a brief report:
-what surg is being done
-PMH
-airway info
-fluids/blood loss
-any complications (airway/ diff mask, etc)
-plan for emergence (if close to end)
-ASK IF THEY NEED MORE INFO
Most adverse events are _ related
respiratory
-also human error related
Common intraop complications:
-PVCs on incision
-pt moving
-bronchospasm
-CV changes
-bleeding
-allergy
-POWER OUTAGE
Common human error complications
-unnoticed circuit disconnect
-drug errors
-airway mismanagement
-anesthesia machine misuse
-fluid mgmt
-IV line disconnect
