OB regional anesthesia: spinal, epidural, caudal – Flashcards
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What are the stages of labor?
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-1st stage (cervical stage) -2nd stage (pelvic stage) -3rd stage (placental stage)
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What does the 1st stage (cervical stage) of labor begin and end with?
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Begins with contractions and ends with complete cervical dilation
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What does the 2nd stage (pelvic stage) of labor begin and end with?
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Begins with complete cervical dilation and ends with birth of infant
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What does the 3rd stage (placental stage) of labor begin and end with?
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Begins with birth of infant and ends with placental delivery
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Unlike somatic pain, visceral pain may feel?
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Dull and vague and may be harder to pinpoint
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How is somatic pain generally described?
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As musculoskeletal pain
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Why is somatic pain usually easier to locate than visceral pain?
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Because many nerves supply the muscles, bones and other soft tissues -somatic pain also tends to be more intense
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What is 1st stage labor pain from?
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-uterine contractions and distention -cervical dilation and distention
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How is 1st stage labor pain transmitted?
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-visceral afferent (sympathetic) nerve fibers -somatic nerve fibers
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In 1st stage labor pain, Visceral nerve fibers accompany:
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-sympathetic nerves -para-cervical nerves -lumbar sympathetic chain -enter the dorsal horns of the spinal cord at the T10-L1 level
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Somatic nerve fibers include?
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-pelvic floor -vaginal surface of the cervix -upper vaginal pain -perineum -enter the spinal cord at the S2-S4 sc
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With visceral pain, early labor pain is located where?
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T11 and T12 dermatomes
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The intensification of contractions with visceral pain is located where?
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T10 and L1
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1st stage labor pain can be alleviated with?
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-para-cervical block -lumbar sympathetic block -para-vertebral block -epidural block
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This is a late stage 1 and stage 2 event
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Somatic pain
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Somatic pain results from distention of the?
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-pelvic floor -vagina -perineum
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Somatic pain is transmitted primarily through?
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-sacral and pudendal plexus -lumbar plexus
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Where in the pelvis are the sacral and pudendal plexus located?
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S2-S4 (pudendal nerve)
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Where in the pelvis is the lumbar plexus located?
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-L1 (Ilioinguinal nerves) -L1-L2 (genito-femoral nerves) -L2-L3 (lateral femoral cutaneous nerves)
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Para-cervical block entails the particular risks of:
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-intravenous injection -intra-arterial injection -intra-fetal injection *note particularly the proximity of the presenting part
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Name the types of regional nerve blocks effective for analgesia during labor and delivery
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-uterine and cervical (visceral pain) -perineal and vaginal (somatic pain) -all pain of parturition
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What are types of uterine and cervical (visceral pain) regional nerve blocks effective for analgesia during labor and delivery?
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-bilateral para-cervical blocks (obstetrician placed) -bilateral lumbar sympathetic blocks at L2 -bilateral para-vertebral somatic blocks at T10-L1 -segmental lumbar epidural block T10-L1
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What are types of perineal and vaginal (somatic pain) regional nerve blocks effective for analgesia during labor and delivery?
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-bilateral pudendal nerve blocks (obstetrician placed) -bilateral sacral root blocks S2-S4 -"true saddle block" (subarachnoid block) S1-S5 -low caudal epidural block S2-S4
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What are types of all pain of parturition regional nerve blocks effective for analgesia during labor and delivery?
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-any combo from visceral and somatic categories *"modified saddle block" with upper level T10 or higher *lumbar epidural from T10-S4 -caudal epidural from T10-S4
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Labor effects what in Maternal physiology?
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-respiratory system -cardiovascular system -endorphins -Adrenergic response -acid-base balance
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With labor, minute ventilation increases up to?
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300%
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When in labor, increased minute ventilation does what?
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-results in marked hypocarbia -leads to hypoventilation between contractions -maternal and fetal hypoxemia -utero-placental and feto-placental vasoconstriction
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What effects of labor on maternal physiology happens in the respiratory system?
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-Intermittent increases and decreases of minute ventilation -left shifted oxyhemoglobin dissociation curve -O2 consumption increases up to 75%
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What effects of labor on maternal physiology happens in the cardiovascular system?
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-labor leads to an increase in maternal cardiac output (CO) by 10-25% -primarily increased stroke volume (SV) -BP increase 5-20% -delivery leads to auto-transfusion to mother -analgesia may decrease uterine vascular resistance
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What effects of labor on maternal physiology happens with endorphins?
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-maternal concentrations of beta-endorphins increase in pregnancy with further increases with labor -epidural analgesia attenuates this further increase -may contribute to the pregnant patients decreased anesthetic needs
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What effect do catecholamines (Adrenergic response) have?
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-increase cardiac stress -decrease UBF
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What increases catecholamine levels?
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Pain, stress and anxiety *epidural analgesia attenuates these rises
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How do catecholamines facilitate early extrauterine life?
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-surfactant production -blood flow to vital organs -thermo-regulation
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What effects of labor on maternal physiology happens with acid-base balance?
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-pain, anxiety and muscle activity lead to metabolic acidosis -increased levels of lactic acid in 2nd stage labor -effective analgesia attenuates lactic acidosis
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Name the anatomic changes of pregnancy affecting regional techniques
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-engorgement of epidural veins leads to more unintentional venous cannulation and unintentional injection of local anesthetics -specific gravity of CSF in pregnant patients decreases
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It is more difficult for pregnant patient's to achieve ____ ____
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Lumbar flexion
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Progressive accentuation of the ____ ____ alters "surface-to-vertebral-anatomy
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Lumbar lordosis
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Spinal cord terminates as the?
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"Conus medullaris" at L1
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This attaches the conus medullaris to the coccyx?
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Filum terminale
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This is made of the nerves of the lower lumbar and sacral roots
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"Cauda equina"
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This is the nonvascular membrane closely attached to the dura
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Arachnoid mater
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This is a "potential space" that exists between the dura and the arachnoid mater
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Subdural space
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(Unintentional) sub dural injection may explain:
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-some failed spinal anesthetics -some slow to develop high spinal blocks with epidurals
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The dura mater extends from?
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The foramen magnum to S2
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This extends from the foramen magnum to the sacral hiatus
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Epidural space
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This forms the posterior boundary of the epidural space
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Ligamentum flavum
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Contents of the epidural space include:
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-nerve roots -fat -lymphatics -blood vessels
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Contraindications to SPA/EPI
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-patient refusal -communication barrier -increased intracranial pressure (2*mass lesion) -skin or soft tissue infection at insertion site -uncorrected maternal hypovolemia -coagulopathy
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Contraindications to SPA/EPI due to coagulopathy?
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-platelets <100,000 -low molecular weight heparin (Lovenox) is a clinical risk factor for neuraxial anesthesia -anticoagulants
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Postural factors effect anesthetic spread with?
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Spinal anesthesia
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Position less influential on ___ ___ ___ than with SPA
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Epidural anesthesia spread
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This is type of anesthesia is infrequently used but may be useful in selected patients when epidural contraindicated
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Caudal anesthesia
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In spinal anesthesia, what technique is most often used?
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"Single shot"
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What type of needle has lower incidence of post-dural puncture headache (PDPH)?
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Non-cutting needles
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Needle off midline will result in?
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No CSF -and possibly pain to the right or left
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With SPA: para-median approach, insertion is?
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-1 cm lateral -1 cm caudal -10-15 degrees off midline to the cephalad spinous process
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What is most commonly used regional technique in OBA?
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Epidural analgesia/anesthesia
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What technique is utilized most often for labor pain control?
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Continuous midline technique
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Steps (1-9) of epidural technique
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-position patient first -place monitors: FHM, maternal SO2 + NIBP -mask and hat/hair cover -open kit, then properly glove sterilely -prep x 3 in sterile fashion -allow betadine to dry -drape sterilely -set up your tray -wet seal glass syringe
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Steps (10-18) of epidural technique
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-infiltrate the area with 1% Lido -place 17G Tuohy cannula into interspinous ligament -loss of resistance -inject 3-5 ml NS -place catheter -remove cannula -connect adapter -inject "test dose" (2.5-3 ml lido 1.5% with epi) -tape securely
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How should you infiltrate the area with 1% Lido when using epidural technique?
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-use smallest cannula (25, 27G) -inject slowly -do not "fan" or repeat "in and out" -inject SQ Interspinous ligaments
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What do engorged spinal veins do to CSF space?
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-decrease the space and displace CSF into the thoracic region
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Is fat increased or decreased in the epidural space?
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Neither. It is unchanged.
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What do hormonal changes do to the ligamentum flavum?
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-Softens it -increased risk of wet tap
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Where does the dura mater terminate?
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S2
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What meningeal layer is CSF found in?
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SUB arachnoid space
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What is the key factor in obtaining the level of block desired?
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VOLUME -guideline is 1-2 mL per segment -adjust (6 ft 2 in)
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Test dose for lidocaine + epinephrine
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(2.5-) 3 cc 1.5% Lidocaine + Epinephrine
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Caudal anesthesia
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-requires correct identification of the sacral hiatus -angle of insertion 45 degrees, contact bone, redirect to 15 degrees, insert approx. 1-2 cm -use test dose
