Epidural/Spinal Analgesia/anestesia for LABOR – Flashcards
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Painful uterine contractions can lead to ___________, which leads to maternal _________ ____________ and eventually reduced oxygen delivery to the fetus.
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Hyperventilation, respiratory alkalosis
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What are the 6 contraindications to Epidural and Spinal anesthesia
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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)
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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
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Persistent uterine tachysystole should prompt administration of a tocolytic drug which includes;
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- Terbutaline - Nitroglycerin
