OB Flashcards
Most physiologic changes occur in the ___ trimester, and most anatomic changes occur in ____
Physiologic = 1st trimester
Anatomic = 2nd and 3rd trimesters
Are the physiologic and anatomic changes in pregnancy good or bad?
Mostly good.
Respiratory changes in pregnancy
1) Increase in ventilation - D/t increased metabolic demand - Increase 40% TV and 15% RR - Increase 50% MV overall - High ventilation will decrease CO2 levels (goes into resp alkalosis pH = 7.44) 2) Decrease in airway resistance - d/t increased progesterone - Lung compliance unchanged 3) Increase in O2 Consumption - Increase by 20% - Curve shifts to the right (P50 increases from 26-28mmHg)
Anatomic respiratory changes in pregnancy
1) Cephalad diaphragm displacement 2) Weight gain and breast enlargement (pressure on the chest and boobs might get in the way of airway) 3) Vascular engorgement of the respiratory tract mucosa - Mucus membranes fragile 4) Edema of nasopharynx, oropharynx, and the cords
When is edema of the nasopharynx, oropharynx, and the cords most common?
During pre-eclampsia Remember there is HTN and loss of plasma proteins.
Effect of pregnancy on the FRC
Decrease by 20% Less safe apnea time!!
Why can pregnant ladies desat quickly?
Low FRC and high O2 consumption rate (20% higher than normal).
We can expect induction during pregnancy to be (faster/slower) than the non-pregnant patient. MAC should be (increased/decreased) by ____.
Faster induction Decreased MAC by 25-40%
Effects of maternal hyperventilation
Alkalosis - Shift to the left (will decreased O2 release to the fetus) - Constriction of the umbilical and uterine blood vessels This is only a problem with prolonged hyperventilation
Effects of elevating the diaphragm
Decreased FRC and displacement of the heart (look at EKG, listen for murmur, possible dysrhythmia)
Pregnancy and coagulation
Overall, it is a hypercoagulable state Increased clotting factors (fibrinogen and factors 5-8) Platelets remain unchanged or may decrease slightly
CO will be (increased/decreased) during pregnancy
Increased
What happens to BP and SVR in pregnancy
SVR will decreased by 20% - vessels lose their SNS tone BP will decrease slightly - ADH is cleared more rapidly - BP maintenance depends on RAAS b/c vessels have lost their SNS tone
Your pregnant patient is lying supine and starts to drop their BP. What is this and how is it treated?
Supine Hypotensive Syndrome - It’s possible compression of vena cava or aorta. Treatment: - Left or right uterine displacement (depending on which vessel is compressed) - Hydrate before induction - Treat hypotension with ephedrine or phenylephrine
Supine hypotension syndrome is a risk > ____ weeks and can decrease CO by up to ___%
20 weeks 30%
Plasma volume increases by ___% but RBC volume only increases by ___%.
Plasma 50% RBC 20% Causes a dilutional anemia
Normal blood loss during vaginal birth
500cc
Normal blood loss during a c-section
500-1,000cc
GI changes in pregnancy
As a result of physiologic and hormonal changes: - Delayed gastric emptying - Everything in the GI tract slowed overall - Secretions are more acidic - Stomach is displaced upward and at 45 degree angle to the right. This displaces the intra-abdominal portion of the esophagus into the thorax, decreasing tone to the lower esophageal sphincter, causing reflux
All parturients greater than ___ weeks are considered full stomachs
12 weeks Aspiration risk continues into the post-partum period, until the body has time to normalize hormonally, physiologically, and anatomically.
Aspiration prophylaxis in pregnancy
Give non-particulate antacids, H2 blockers, and/or reglan. Consider doing regional instead. If doing GA, do RSI.
Renal Changes in Pregnancy
High CO and large blood volume cause an increase in GFR by 60%. Creatinine clearance increases, decreaseing serum CR
Increased glucose excretion
increased bicarb excretion (compensation for respiratory alkalosis)
Hepatic Changes in Pregnancy
Slight increases in AST and ALT Bigger changes will be seen in HELLP syndrome (part of pre-eclampsia)
Biliary stasis and increased secretion of bile leads to increased gallbladder disease
Neuromuscular Changes in Pregnancy
1) Increase in endorphins! - Allows us to decrease MAC by 40% 2) Increased sensitivity to opioids, LAs, and catecholamines
Why is MAC decreased in pregnancy?
1) Faster induction 2) Higher endorphins potentiates the effects of the VA
Formula for uterine blood flow and normal values for UBF
(uterine arterial pressure - uterine venous pressure) / Uterine vascular resistance UBF during pregnancy: 500-700mL/min UBF when not pregnant: 50-100mL/min
There is a direct correlation between uterine blood flow and
fetal umbilical venous O2
When will uterine blood flow decrease?
1) Decrease in perfusion pressure (maternal hypotension SBP
Is the uterine vascular bed able to autoregulate?
NO! This is why BP management in parturients is critical
We are most worried about fetal ion trapping with these drugs
LAs
Generally all of our anesthetics will cross the placenta except
NMBs
What is a protective mechanism that the fetus has against drug OD?
Blood from the umbilical vein first goes to the liver
What is the baseline fetal HR?
120-160 May vary by 5-10bpm and variations are a good and normal thing.
Causes of fetal tachycardia
Maternal fever or infection Atropine administration Late sign of fetal hypoxia
LATE decelerations may be from
Compromised blood flow to the fetus (maternal hypotension, cord compression, etc)
SEVERE decelerations will go below __bpm and last longer than ___
70 1 minute Fetus is in distress! We need to deliver!
Treatment for shitty fetal heart rate patterns
1) LUD (left uterine displacement) - Compression could be decreasing CO by 30% 2) O2 3) Correct any contributing factors (treat hypotension, stop oxytocin, check for prolapsed cord in her vajay, assess for vaginal bleeding that could be from the placenta)
Stages of Labor
1st Stage - From beginning of regular painful contractions to full cervical dilation - Longest stage of labor and divided into two phases - This is mostly visceral pain (Block T10-L1) –> Latent Phase: 1st and longest part. Contractions start and are getting stronger and cervix is thinning –> Ative Phase: Second and shorter phase. The cervix is actively dilating to 10cm 2nd Stage - From full cervical dilation to delivery - This is the most painful stage*** - This is somatic, stretching pain (Block S2-4) 3rd Stage - From delivery of neonate to delivery of the placenta
Staging and neuraxial block requirements
1st Stage (T10-L1) 2nd Stage (T10-S4) 3rd Stage (T10 b/c it involves the vag and uterus)
Risks for intense pain during pregnancy
Young maternal age (ya so tight) Increased maternal weight (excess tissue in the way) Occiput posterior presentation Increased fetal weight (fat baby) Use of tocolytics
Opioids popular in pregnancy
Fentanyl and meperidine (Demerol) Sufentanil not as popular because it can cause fetal bradycardia
Common analgesic interventions in parturients
Opioids Ketamine Agonist/Antagonists (Nubain & Stadol) Intrathecal Opioids Epidurals CSE
Can epidurals prolong labor?
Yes, it can prolong Stage 1
Relative contraindications for regional anesthesia
Primary herpes Obstructive cardiac lesions R or L intracardiac shunts Active CNS disease PIH (pregnancy induced HTN) MG (possible respiratory compromise)
Epidurals should be placed below this level
Below L2
Does the level of epidural block depend on baracity of the LA?
NO. It would matter in spinals. NOT epidurals!
Most common LAs in pregnancy
Amides: Lidocaine, bupivacaine, and ropivacaine Esters: Chlorprocaine, tetracaine, and mepivacaine
Epidural concentrations used for bupivacaine
.125% - .25% Used with or without an opioid
Epidural concentrations used for ropivacaine
.125% - .2%
Benefits of having a continuous laboring epidural (CLE)
More constant level of analgesia More even block More stable VS Greater safety Able to use if need to give surgical block for emergent c-section
Procedure for continuous epidural infusion
1) Give test dose with epi. Wait 3-5 min before initiation of bolus (may be difficult to detect b/c mother is probs already tachy from pain) 2) Give bolus injection 3) Start continuous infusion once adequate block obtained (at LEAST T10 level)
Block above this level will start to affect cardiac accelerators
T4
Sometimes the first sign of a sympathectomy may be
N/V If your patient starts having N/V after epidural placement - check BP for hypotension. We don’t want SBP
Effects of epidural on labor
Slows Stage 1 Can halt labor if cervix dilated
Caudal Block
Type of epidural not common in OB. Needs high volumes. May be ok in Stage II
Paracervical block
Usually done by OBGYN - LA injected submucosally in the vagina on either side of the cervix. May be used for Stage I (while cervix is dilating), but there is high risk of fetal bradycardia from LA injection.
Pudendal block
Good block for Stage II (delivery) Inject LA on both sides of vagina into the sacrospinous ligament. Good perineal anesthesia.
Parturients are most likely easy or difficult airway?
Difficult Edema of oropharynx and cords
If doing a spinal block for c-section, you should block at this level
T4-6
