case 57 - anesthesia for nonobstetric surgery during pregnancy Flashcards
what are the physiologic changes in pregnancy and anesthesia implications for respiratory and cardiac?
1) respiratory
- inc MV (inc TV and RR), inc O2 consumption
- dec FRC (dec ERV and RV) -> uterus pushing diaphragm
- anes -
- inc MV + dec FRC
- rapid uptake and excretion of volatile anes
- dec FRC + inc o2 consumption
- quicker develop of arterial hypoxemia during apnea
- edema + weight gain -> difficult intubation
- inc MV + dec FRC
2) Cards
- inc CO (inc SV and HR), dec SVR (progesterone)
-
inc plasma volume > inc red blod cell volume
- (relative anemia of pregnancy)
- aortocaval compression 2/2 uterus -> hypotension
- Anes
- left uterine displacement
- inc CO = inc speed of IV induction of anes
what are the physiologic changes in pregnancy and anesthesia implications for GI, hepatic, heme?
3) GI
- inc gastric presure (2/2 gravid uterus pushing up on stomach)
- dec lower esopha sphincter tone
- ?? delayed gastric emptying
- Anes
- inc risk of aspiration
- pre-tx with metoclopramide, sodium bicit, H2 blocker
- RSI&I + cricoid
- inc risk of aspiration
4) hepatic
- dec psuedocholinesterase activity (hemodilution)
- anes
- prolong affect of sux (rarely an issue)
5) Heme
- inc clotting factor and fibrinogen concentration
- anes
- hypercoaguable state -> risk of thrombsis (DVT, PE)
- VTE prophylaxis
what are the physiologic changes in pregnancy and anesthesia implications for Renal & CNS?
6) Renal
* inc RBF, inc GFR, Dec BUN/Scr
7) CNS
- progesterone - > decrease MAC + inc sens to LA
-
gravid uterus -> compreses IVC -> engorgement of epidural veins
- decreases size of epidural and intrathecal spaces due to epidural venous engorgement
- Anes
- Progesterone
- decrease MAC to avoid anesthetic overdose
- epidural veins + LA sensitivity
- dec volume + dose of LA during neuraxial anesthesia
- Progesterone
what is a teratogen, are there any anes meds that are teratogenic?
teratogen
- substance that produces congenital defects
- weeks 3-8 of fetal development
anes meds
-
Most anes meds are NOT tertagoenic
- almost all are category B or C classification (category ratings of drugs during pregnancy)
- Class B = no evidence of risk in humans
- Class C = risk cannot be ruled out
NO and BZD = controversial
-
BZD - class D - potential evidence of risk
- best to avoid during pregnancy
- cleft palate
- NO
- oxidizes Vit B12 -> needed for methionine synthetase (develop thymidine molecule for DNA)
- not been found to be assoc with congential abnormalities in humans
OR nurse comes to you and asks if she is at risk for complicated pregnancy due to volatile anes gases, what do you say?
OR personnel exposed to volatile anes
- higher risk of spont abortion and congential abnormalities
- scavanging system in place -> removes gases
what precautions should be taken to avoid intrauterine fetal asphyxia during nonobstetric surgery?
goals
- maintain normal maternal PaO2
- maintain normal PaCo2
- maintaine uterine blood flow
1) PaO2
- increase Fio2 to maintain adeqauate SaO2
- maternal hypoxemia -> fetal hypoxemia
- avoid high spinal/epidural
- general anes -> apnea assoc with quick desat
2) PaCo2
- severe hypocapnia (dec PacO2) assoc with vasoconstriction of uterine blood vessels
- dec blood flow to fetus
- alkalosis shift oxyhemoblogin dissoc curve to left
- monitor TV, RR
3) uterine blood flow
-
UBF = perfusion pressure / vasc resistance
- prefusion pressure = MAP - CVP
-
PP
- aortocaval compression -> Left uterine displacement
- maternal hypotension (anes overdose, hypovolemia, blood loss)
- vasc resistance
- alpha adrenergic drugs, dec PaCo2, inc catechoalmines (light anes, pain) -> all inc vasc resistance -> decrease UBF
is pre-term a possiblity during nonobstetric surgery in a pregnant patient?
pre-term labor
- high risk of preterm assoc with procedures manipulating the uterus (abd procedures)
- anes does not affect pre-term labor risk
-
lowest risk of preterm labor -> 2nd trimester
- if urgent surgery necessary, push for 2nd trimester
is there any additional monitoring needed for anesthetizing a pregnant patient undergoin nonobstetric surgery?
YES
prior to surgery, consultant OB/GYN:
- FHR pre-procedure
- FHR intra-op if feasible
- FHR post-procedure
- create a plan for emergent c/s and fetal distress
any speical considerations for pregnant pts underoging laproscopic surgery?
- maintain normocarbia
- pneumoperitoneum can increase PaCO2 levels
- cautious placement of surgical trocars
- main low pneumoperitoneum pressure (<15 mmHg) to allow uterine perfusion
Pregnant patient comes for non-obstetric surgery, how would you handle this patient from seeing her pre-op till induction of surgery?
1) avoid surgery during 1st trimester if possible
2) consult Ob/GYN
- document FHR pre-op, intra-op (if possible), and post-op
- create plan for fetal distress and emergent c/s
- **inform pt no known risk of fetal congenital defects, but inc risk of miscarriage or premature labor
3) monitor FHR intra-op if possible
4) avoid pre-medication (risk of aspiration)
5) admin aspiration prophylaxis after 1st trimester
* sodium bicitrate, H2 blocker, metoclopramide
6) LUD if > 16 weeks
* avoid aortocaval compression
7) regional vs general
-
provide regional if possible -> avoid irsk of aspiration, difficult intubation, decrease fetal exposure of anes meds
- tx hypotension 2/2 sympathetcomy immeditely with fluids and pressors
-
if general:
- RSI&I
- various emergency meds and airway equip on standby, suction readily avialable
Pregnant patient comes for non-obstetric surgery, what are your anes concerns for regional and general anes? Do you have post-op concerns?
regional
- provide unless contraindicated
- avoids intubation, risk of aspiratoin, dec fetal exposure to meds
-
sympathetcomy -> hypotension -> dec fetal perfusoin
- tx immedietly with fluids and pressors (phenyl, ephedrine)
- avoid oversedation, monitor EtCo2
general
- aspiration prophylaxis
- difficult intubation -> variety of airway equipment
- RSI&I
- EtCo2 - pregnant levles - 30-35 mmHg
- SaO2 > 95% -> inc FIO2 as necessary
- maintain uterine blood flow
Post-OP
- FHR monitoring
- maintain uterine blood flow (ie avoid hypotension)
- avoid hypotension, hypoxemia, hypercarbia, hypothermia