Where is the pain in the 1st stage of labor?
Lower Uterine - T10 - L1
Where is the pain during the 2nd stage of labor?
Perineal structures via Pudendal Nerves - S2 - S4
What are some Non-Pharmacological Analgesics for Labor?
- Psychoprophylaxis (Lamaze) - behavior & breathing techniques
- Accupunture - Energy flow patterns
What is the problem w/ using Opioids on Parturients?
Crosses Placenta & Depresses Fetus
What is the advantage of using PCA's for pain for parturients?
Less Fetus Depression
Less Respiratory Risk for mom
Why is morphine not normally given to the mom for pain?
Baby's immature blood brain barrier increases risk for respiratory depression
Which pain med given for labor is contraindicated in patients with seizures or renal failure?
Can cause frequent N/V
Fetal Resp. Depression unlikely if given < 1 hr before delivery
What are some considerations when giving Fentanyl to a parturient?
100x more potent than morphine
Rapid transfer across Placenta
Respiratory depression lasts longer than pain control
What is Nalbuphine (Nubain)?
Opioid Antagonist, Kappa Agonist
Treats Opioid Pruritis
Resp. Depression Ceiling
Why is Butorphanol (Stadol) sometimes used instead of Fentanyl?
Better pain control & less itching
Resp. Depression Ceiling
Why are gases rarely used to control paturient pain?
Decreases Uterine Tone
When is a Paracervical Block placed?
1st stage of Labor
Inject 5cc of LA submucosally @ 3 & 9oclock beside cervix
What are the risks involved w/ ParaCervical Blocks?
Injection into Uterine Artery
Fetal LA Toxicity
When are Pudendal Blocks used?
2nd Labor Stage
When Neuraxial Blocks are Contraindicated
Transvaginal Approach under Ischial Spines w/ Bilateral Needle Placement
What are the risks associated with Pudendal Blocks?
Fetal Injury, Infection, and Hematoma
Which Local Anesthetics are derivatives of Para-Aminobenzoic Acid (PABA)?
PABA = Allergen
Metabolized by Cholinesterase
Which class of Local Anesthetics are more often used in OB?
No PABA = No Allergic Reactions
What is the Local Anesthetic relationship b/t its Lipid Solubility & Potency?
More Lipid Soluble = More Potent & Enchances Placental Diffusion
How does Protein Binding affect Local Anesthetics?
More Protein Binding = Longer Duration & Decreases Placental Transfer
Protein binding Local Anesthetics have a ____ affinity & ____ capacity to A1-acid Glycoprotein
Protein binding Local Anesthetics have a High Affinity & Low Capacity to A1-acid Glycoprotein
Protein binding Local Anesthetics have a ____ affinity & ____ capacity to Albumin
Protein binding Local Anesthetics have a Low Affinity & High Capacity to Albumin
Which property of Local Anesthetics determines Speed of Onset?
The closer the pKa is to physiological pH, the faster onset
Bicarb is used to artifically raise physiological pH
What would be the results of increasing Local Anesthetic Volume & Dose?
Faster Onset & Longer Duration
What can be given to prevent Systemic Absorption of Local Anesthetic?
Vasoconstrictors - Epi, Norepi, Neo
How does Temperature affect Local Anesthetics?
Warmed LA = faster onset
How does Pregnancy affect Local Anesthetics?
Preggos need less LA & has faster onset
Which type of nerves are more susceptible to blocks?
C- Fibers - small & unmyelinated
Larger fibers need more LA
What are the most commonly used Epidural Analgesics for Labor?
What Local Anesthetics are used for Operative Epidural Analgesia?
Lidocaine & 2-Chloroprocaine
Which Local Anesthetics are used for Spinal Anesthesia?
Tetracaine & Bupivacaine
Which Local Anesthetic can be used to test and activate the Epidural Catheter, has a short duration, and causes a lot of Motor Block?
Which Ester LA is the only one used in the Epidural Space?
Rapid Onset, Short Duration
Lots of Motor Bock
Low Toxicity Risk
When in particular would you NOT use 2-Chloroprocaine?
In patients w/ Atypical Pseudocholinesterase
What happens when you give Epidural Fentanyl after the patient had 2-Chloroprocaine?
Fentanyl would be less effective
What makes Bupivacaine a good Local to use during labor?
Long Duration & Less Motor Block
BIG dose = V-Tach/V-Fib
Which of the following LA's is the most Cardiotoxic: Levobupivacaine, Ropivacaine, Bupivacaine?
Bupivicane > Levobupivacaine > Ropivacaine (25% less potent)
Only Bupivacaine is approved for Spinals
How should Epidural Drugs be given in OB?
Small Doses incrementally as test doses
What is the next course of action if the patient experiences paresthesia while a spinal is being dosed?
Where should Spinals be placed in Obstetrics?
As low as possible, Below L3
Where is Tuffier's Line?
Transverse line passing thru lumbar spine b/t posterior iliac crests - L4
Which dermatomes should be covered for Obstetrics
Lumbar Level - T10 - S4
What are contraindications to Neuraxial Blocks?
Existing Spinal/Neuro Disease
What are the steps in placing an Epidural?
- Position Patient
- Prep Skin
- Numb Skin
- Identify Space w/ Midline or Paramedian Approach
- Use Tuohy Needle & LOR Technique
How far should the Catheter tip be advanced once the Epidural Space is identified?
Until 5 cm of the tip lie in the space
How should the Epidural Catheter be handled?
Dont pull catheter back thru needle - may shear
Aspirate to R/O CSF or Blood
Give Test Dose
What are the difference b/t Epidurals & Spinals?
Drugs thru Spinals are 10x more potent & smaller needle used (22-27ga)
Epidural uses 17-18ga needles
When are Subarachnoid Blocks used for Labor?
When delivery is soon & no time for Epidural
Opioid only or LA Combo
What are the Pros and Cons of Combined Spinal Epidural?
Instant Relief, but difficult to test epidural catheter
What are signs of LA Toxicity?
Loss of Consciousness
How does Acidosis & High PaCO2 affect Local Anesthetics?
Lowers Seizure Threshold
Decreases Protein Binding = More Free LA
How does Local Anesthetic Toxicity affect the CV System?
Inhibits Sodium Channels
↓Rate of Depolarization
↓Action Potential Duration
↓Effective Refractory Period
What should be done for a patient with LA Toxicity that started convulsing?
- Clear Airway
- Position Patient - Avoid Aortocaval Compression
- Bag Mask Ventilation
- Manage arrythmias
- Immediate Delivery if Possible
What can be given for Refractory Local Anesthetic Toxicity
What are symptoms of Subdural Block?
(Catheter is b/t Dura & Arachnoid Mater)
Loss of Consciousness
What should be done if a Subdural Block is detected?
Dont dose & Replace catheter into Epidural Space
What is Term Labor?
37 - 42 Completed Weeks
What is considered Preterm Labor?
Regular contractions every 10 minutes causing cervical change before 37 weeks
What infant weight is considered low?
Low Birth Weight < 2500g
Very Low Birth Weight < 1500g
(usual wt. @ 29 wks)
Mortality is 90% if infants born _____ and Survival rate is > 90% if they're born ______
Mortality is90% if infants born < 24wks and Survival rate is > 90% if they're born > 30 wks
@ 34 wks = 98% survival
What are the Prematurity Comorbidities?
- Respiratory Distress Syndrome
- Necrotizing Enterocolitis
- Intracranial Hemorrhage
- Ischemic Cerebral Damage
- Immature Matabolism
What bacteria is associated with Preterm Labor?
Group B Strep, Neisseria Gonorrhoeae, and Bacterial Vaginosis in Genital Tract
When is a C-Section safer than delivery in regards to Preterm Labor?
How does Ethanol work as Tocolytic Therapy?
Inhibits ADH & Oxytocin Release
Risk for Intoxication, Loss of Consciousness, and Aspiration
How does Aminophylline work as Tocolytic Therapy?
Phosphodiesterase that relaxes Uterus by increasing cAMP
Narrow Therapeutic Margin & Toxic
How does Nifedipine work for Tocolytic Therapy?
Decreases free calcium to decrease Myometrium Contractility
What are the side effects of using Nifedipine as a Tocolytic?
Decreased UBF & Fetal Hypoxemia/Acidosis
Which type of Tocolytic Therapy makes the patient more prone to Cardiac Depression from Volatile Agents?
Calcium Channel Blockers
What are some Prostaglandin Inhibitors that are used for Tocolytic Therapy?
Indomethacin & Sulindac
Decreases CycloOxygenase to decrease Prostaglandin
What are the Maternal side effects of Prostaglandin Inhibitors?
Decreased platelets & bleeding
What are the Fetal side effects of Prostaglandin Inhibitors?
Premature closure of ductus
Which medication is the most commonly used for Tocolytic Therapy?
Prevents Calcium Increase
How does Magnesium affect MAC & NMBs?
Patient more sensitive to all NMBs
What would you see with a Magnesium level of 8 - 10?
Loss of Deep Tendon Reflexes
What would you see with a Magnesium level of 10 - 15?
Resp. Depression & Wide QRS & P-R Interval
How should Magnesium toxicity be treated?
Calcium Gluconate or Calcium Chloride
What are the Beta Adrenergic Agonists used for Tocolytic Therapy?
Terbutaline & Ritodrine
Directly increases cAMP to Relax Uterus
What are the side effects of using Terbutaline or Ritodrine?
How much does the risk of Fetal Death increase w/ having twins vs singleton?
5-6x d/t increased risk of prematurity
Second twin has greater risk d/t placental abruption, cord prolapse, & malpresentation
What are the Maternal complications of having Mutliple Gestations?
Increased CO earlier
↓TLC & FRC
Bigger Uterus = Aortocaval Compression & Aspiration
What can be expected with Multiple Gestations?
Preterm Labor - 50%
Pregnancy Induced HTN
C-Section for triplets or more
What are the Anesthetic considerations for Multiple Gestations?
Early Epidural Placement
Treat as C-Section
2-Chloroprocaine for Rapid Onset
Nitroglycerine to Relax Uteus for Rotating Baby
What are the signs and symptoms of a Uterine Rupture?
Sudden & Severe Abdominal Pain
Fetal Distress - Most Reliable Sign
What is the best presentation for delivery?
Faced down, Flexed C-Spine w/ chin to chest
What is a Breech Presentation?
Both feet down
Frank: Both Legs Up Near Head
Incomplete: One leg up one leg down
90% of Breech = C-Section
Why is there an Increased Risk for Fetal Death associated w/ Breech Presentation?
Maternal infection d/t Manipulation
Which presentation is an Absolute Indication for C-Section?
Transverse Lie Presentation
What are problems with Postmaturity (Gestation > 42 wks)?
Meconium Staining of Amniotic Fluid
Big Baby w/ Big Shoulders
What are the causes of Intrauterine Fetal Demise (IUFD)?
- Abnormal Chromosomes
- Congenital Malformations
- Cord Accidents
- Multiple Gestations
- Placental Factors
- Maternal Trauma
- Maternal Immune/Thyroid Disease
What can happen to the cord that results in Intrauteral Fetal Demise?
< 30 cm Length = compression, constriction, rupture
> 72 cm Length = Entanglement