Epidural/Spinal Analgesia/anestesia for LABOR – Flashcards

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question
Painful uterine contractions can lead to ___________, which leads to maternal _________ ____________ and eventually reduced oxygen delivery to the fetus.
answer
Hyperventilation, respiratory alkalosis
question
What are the 6 contraindications to Epidural and Spinal anesthesia
answer
1. Pt refusal or inability to cooperate 2. Increased ICP due to a mass lesion 3. Skin or soft tissue infection at the site of needle placement 4. Frank coagulopathy 5. Uncorrected maternal hypovolemia (hemorrhage) 6. Inadequate training/experience with technique
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What are the steps involved in properly preparing someone for Neuraxial Analgesia?
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1. Communicate with OB and review parturient's history 2. Perform focused preanesthetic evaluation (history and exam) 3. Review relevant labs and imaging 4. Consider need for type/screen 5. Formulate analgesia plan 6. Obtain Informed Consent 7. Perform equipment check 8. Obtain IV access 9. Apply maternal monitors 10. Monitor FHR 11. Perform TIME OUT
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What are the advantages to a continuous epidural?
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- continuous analgesia - no dural puncture required - ability to extend analgesia to anesthesia if need for csection
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What are the disadvantages of a continuous epidural?
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- slow onset of anesthesia - Larger drug doses required - risk of systemic toxicity, or greater fetal exposure
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List the advantages of a combined spinal/epidural (CSE)
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- continuous analgesia - low doses of LA and opioids - Rapid onset of analgesia - Rapid onset of sacral analgesia - ability to convert to csection - complete analgesia with opioid alone - decreased incidence of failed epidural analgesia
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What are the disadvantages of CSE?
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- delayed verification of functioning epidural catheter - higher incidence of pruritis - possible higher risk of fetal bradycardia
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Name the advantages of a continuous spinal.
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- continuous analgesia - Low doses of LA and opioids - Rapid onset - Ability to convert to csection
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What are the disadvantages of a continuous spinal?
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- Large dural puncture, increased risk of PDPH - Possibility of overdose and total spinal if mistaken for epidural catheter
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What are the advantages of a continuous caudal?
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- continuous analgesia - avoids need to access spinal canal through lumbar interspace in pts with previous lumbar surgery
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What are the disadvantages of a continuous caudal?
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- requires large volumes/doses of drugs - may be technically more difficult - possible higher risk of infection - risk of inadvertent fetal injection
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What are the advantages of a single-shot spinal
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- technically simple - rapid onset - immediate sacral analgesia - low drug doses
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What is the one disadvantage of single shot spinal?
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- limited duration of analgesia
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What type of fluid bolus administration should you AVOID in laboring women?
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Dextrose containing solutions
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What are the advantages of the lateral over the sitting position of administration of an epidural?
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1. orthostatic hypotension less likely 2. facilitates FHR monitoring better 3. some patients find it more comfortable
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T/F: A negative test dose guarantees the correct placement of the epidural catheter in the epidural space.
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FALSE: it does NOT guarantee correct placement, but it DECREASES the likelihood that the catheter tip is in a blood vessel or subarachnoid space
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If the test dose is intravascular, what type of increase in BP and HR should you see?
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HR= 20 bpm increase BP = 15-20mmHg increase
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How much epi does a test dose usually contain?
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15 micrograms
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When assessing a motor block, what differentiates complete, almost complete, partial and no block?
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1. Complete - patient unable to move feet or knees 2. Almost complete - patient able to move feet only 3. Partial - patient just able to move knees 4. None - patient capable of full flexion of knees and feet
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T/F: The epidural injection of LA for a test dose should not be calculated in the initial dose of local anesthetic.
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FALSE, it should be part of the calculation for the initial dose
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What properties would an ideal analgesic for labor?
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- rapid onset - minimal motor blockade - minimal risk of maternal toxicity - negligible effect on uterine activity and uteroplacental perfusion - limited transplacental transfer - long duration of action
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How is the potency of LA assessed?
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by the Minimum Local Anesthetic Concentration (MLAC)
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What is the MLAC?
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- median effective concentration of a LA solution when administered as a 20mL bolus
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When is the MLAC the lowest?
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for women in early labor and when the LA is combined with a lipid soluble opioid
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What are the advantages of a lower total dose of LA?
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1. decreased risk of systemic local anesthetic toxicity 2. decreased risk of high or total spinal 3. decreased plasma concentrations in fetus and neonate 4. decreased intensity of motor blockade
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Why does Sufenta have a somewhat better analgesia compared to fentanyl in epidurals?
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- greater potency - greater affinity for opioid receptors - greater lipid solubility - better penetration into spinal cord
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Why is fentanyl used more commonly in epidurals than sufenta?
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because the available concentration of sufenta may make drug errors more likely.
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What is the potency ratio of sufentanil to fennel when administered into the epidural space?
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6:1
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What are the advantages of the addition of an opioid to epidural solution?
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1. lower total dose of anesthetic 2. decreased motor blockade 3. reduced shivering 4. greater patient satisfaction
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What is the most common anesthetic used for spinal anesthesia?
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bupivacaine combined with fentanyl or sufenta
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What is the baricity of an intrathecal solution compared to?
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CSF
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How do you make a solution more hyperbaric?
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Adding dextrose, but it also results in less extensive sensory blockade
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What are the different administration techniques used?
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1. intermittent bolus - can asses pain relative to stage of labor 2. Continuous infusion 3. PCEA 4. Timed intermittent bolus injection
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How many mL of LA solution us usually used for an intermittent bolus to reestablish analgesia?
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8-12 mL
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T/F: the sensory and motor blockade should be assessed only before each bolus injection of LA.
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FALSE, it should be checked BEFORE and AFTER
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What is the main disadvantage of intermittent bolus?
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- interruption of pain relief
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What are the potential benefits of continuous infusion?
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- maintenance of stable level of analgesia - less frequent need for boluses - may reduce risk of systemic toxicity - decreased workload for anesthesia provider
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When should you suspect intravenous migration of an epidural catheter?
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- when a patient unexpectedly complains of pain during maintenance of analgesia with continuous epidural
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With migration of the catheter into the subdural or subarachnoid space during infusion should result in what?
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- slow ascent of the level of anesthesia - greater density of motor blockade
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What is the criteria a laboring mother must meet for a 'walking epidural"?
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- reassuring fetal status - engagement of fetal presenting part - stable orthostatic vital signs - ability to perform bilateral straight-leg raises in bed against resistance - ability to step on to a stool with either leg without assistance - satisfactory trial of walking accompanied by nurse - must be accompanied by companion at all times - Intermittent FHR monitoring (15 minutes)
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What are the side effects of neuraxial analgesia?
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1. Hypotension 2. Pruritus 3. Nausea/vomiting 4. Fever 5. Shivering 6. Urinary Retention 7. Recrudescence of Herpes Simplex Virus 8. Delayed Gastric Emptying
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What is the process by which hypotension occurs after neuraxial analgesia?
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- induced sympathetic blockade - peripheral vasodilation - increased venous capacitance - reduced VR to heart - reduced maternal blood pressure and CO
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What is the best way to prevent hypotension in the mother with neuraxial analgesia?
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avoidance of aortocaval compression
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How is this hypotension usually treated?
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- IV crystalloid - Left lateral/trandelenburg position - 5-10mg Ephederine
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What is the most common SE of neuraxial analgesia?
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Pruritus - higher incidence with opioid administration
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T/F: The cause of pruritus is related to histamine release.
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FALSE. It is actually not that well understood, but appears unrelated to histamine. May be caused by a perturbation of sensory input that results from rostral spread of the opioid within the CSF to the level of the trigeminal nucleus in the medullary dorsal horn
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What is the most effective treatment of pruritus?
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centrally acting mu opioid agonist or a partial agonist/antagonist - Antihistamines are ineffective!
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What are some other causes of N/V during labor other than neuraxial analgesia.
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1. neuraxial analgesia induced hypotension 2. pregnancy itself 3. pain 4. opioid-induced delay of gastric emptying 5. systemic opioids
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What is the etiology of neuraxial opioid associated nausea?
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unclear, but may be caused by the modulation of afferent input at the chemoreceptor trigger zone
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What are some drugs that can be used in the treatment of neuraxial induced N/V?
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- Ondansetron - Droperidol - Metocloprmide (give slow to minimize extrapryamidal SE)
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what is the usual increase core temperature in laboring women receiving neuraxial analgesia?
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- usually 1.0 degree C - max temp of 38 C
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What are some reasons temps may be higher in women receiving epidural analgesia?
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- may have longer labor and may be at higher risk for infection - epidurals may alter maternal temperature regulation - epidurals rais the threshold for thermoregulatory sweating and by sympathectomy can prevent sweating and evaporative heat loss in the part of the body affected by the block
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What are 2 situations in which epidural analgesia is employed, but also associated with maternal fever?
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1. nulliparity 2. dysfunctional labor
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the bladder and urethral sphincters receive sympathetic innervation from _____________ and parasympathetic innervation from_____________.
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low thoracic/high lumbar sacral fibers
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T/F: The onset of urinary retention appears to parallel the onset of analgesia.
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TRUE
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Where are Herpes Simplex Virus 1 and 2 typically found?
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1- trigeminal ganglia and causes orofacial lesions 2 - lumbosacral ganglia * either virus can infect any region of the body
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What are some complications of neuraxial analgesia? (10)
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1. Inadequate analgesia 2. Unintentional Dural puncture 3. Respiratory depression 4. Intravascular Injection 5. High neuroblockade/total spinal 6. Extensive motor blockade 7. Prolonged neuroblockade 8. Sensory changes 9. Back Pain 10. Pelvic floor injury
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Factors that are associated with the rate of failure of neuraxial analgesia include:
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- age - weight - specific technique - type of epidural catheter - skill of anesthesia provider
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Assessment and management of inadequate neuraxial analgesia should include:
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- assess the progress of labor (rule out other causes of pain) - perform honest evaluation of anesthetic
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What is the MOST important factor affecting the onset of respiratory depression?
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lipid solubility
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How long does it take for respiratory depression to present with administration of fentanyl? Morphine?
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Within 2 hours Morphine is prolonged, 6-12 hours
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A cesarean is considered for delivery of the infant within ____ minutes if the mother has not been successfully resuscitated from intravascular injection of LA.
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4 minutes
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What is included in the immediate management of a high spinal block?
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- avoidance of aortocaval compression - ventilation with 100% Oxygen - Intubation - IV fluids/vasopressors to maintain pressure - continuous FHR monitoring
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T/F: extensive motor blockade can increase the likelihood of instrumental vaginal delivery.
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TRUE, because it may impair maternal expulsive efforts during the second stage of labor.
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Neuraxial analgesia can have direct and indirect effects on the fetus. What are they?
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DIRECT - Fetal Heart Rate - Neonatal depression (usually after opioid administration) INDIRECT - fetal bradycardia
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Treatment of fetal bradycardia includes: (5)
answer
1. Relief of aortocaval compression 2. Discontinuation of IV oxytocin 3. Administration of supplemental oxygen 4. Treatment of maternal hypotension if present 5. Fetal scalp stimulation
question
Persistent uterine tachysystole should prompt administration of a tocolytic drug which includes;
answer
- Terbutaline - Nitroglycerin
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