case 57 - anesthesia for nonobstetric surgery during pregnancy Flashcards

1
Q

what are the physiologic changes in pregnancy and anesthesia implications for respiratory and cardiac?

A

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

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
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2
Q

what are the physiologic changes in pregnancy and anesthesia implications for GI, hepatic, heme?

A

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

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
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3
Q

what are the physiologic changes in pregnancy and anesthesia implications for Renal & CNS?

A

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
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4
Q

what is a teratogen, are there any anes meds that are teratogenic?

A

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
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5
Q

OR nurse comes to you and asks if she is at risk for complicated pregnancy due to volatile anes gases, what do you say?

A

OR personnel exposed to volatile anes

  • higher risk of spont abortion and congential abnormalities
  • scavanging system in place -> removes gases
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6
Q

what precautions should be taken to avoid intrauterine fetal asphyxia during nonobstetric surgery?

A

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
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7
Q

is pre-term a possiblity during nonobstetric surgery in a pregnant patient?

A

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
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8
Q

is there any additional monitoring needed for anesthetizing a pregnant patient undergoin nonobstetric surgery?

A

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
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9
Q

any speical considerations for pregnant pts underoging laproscopic surgery?

A
  • maintain normocarbia
    • pneumoperitoneum can increase PaCO2 levels
  • cautious placement of surgical trocars
  • main low pneumoperitoneum pressure (<15 mmHg) to allow uterine perfusion
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10
Q

Pregnant patient comes for non-obstetric surgery, how would you handle this patient from seeing her pre-op till induction of surgery?

A

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
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11
Q

Pregnant patient comes for non-obstetric surgery, what are your anes concerns for regional and general anes? Do you have post-op concerns?

A

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
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