chapter 15 analgesica and anesthesia 2004-11-29 r3 길민경
TRANSCRIPT
Chapter 15 Chapter 15 ANALGESICA AND ANALGESICA AND
ANESTHESIAANESTHESIA
2004-11-29R3 길민경
Pain relief in labor : unique problems
Host of disorders unique to pregnancy (preeclampsia, pl abruption, chorioamnionitis, unique physiological adaptations of pregnancy) : directly affected by the choice of analgesia and anesthesia selected
3.8% of total 4097 preg-related deaths
Most important single factor associated with anesthesia-related maternal mortality : experience of the anesthetist
GENERAL PRINCIPLESGENERAL PRINCIPLES
OBSTETRICAL ANESTHESIA OBSTETRICAL ANESTHESIA SERVICESSERVICES
• Certain risk factors should be communicated to the anesthesia-care provider in advance of delivery
1. Marked obesity2. severe edema or anatomical anomalies of the face and neck3. protuberant teeth, small mandible, or difficulty in opening the mouth4. short stature, short neck, or arthritis of the neck5. large thyroid6. asthma, chronic pul dis, or cardiac dis7. bleeding disorders8. severe preeclampsia-ecalmpsia9. prev history of anesthetic Cx10.other significant medical or obstetrical Cx
PRINCIPLES OF PAIN PRINCIPLES OF PAIN RELIEFRELIEF
Simplicity Safety Preservation of fetal homeostasis
ANALGESIA AND SEDATION ANALGESIA AND SEDATION DURING LABORDURING LABOR
MEPERIDINE AND MEPERIDINE AND PROMETHAZINEPROMETHAZINE
Meperidine(50~100mg) + promethazine(25mg) : IM/2-4hrs
More rapid effect – meperidine(25~50mg) IV/1-2hrs
Depressant effect in the fetus : closely behind the peak analgesic effect in the mother
Meperidine : readily crosses the pl, half-life- 2 1/2hrs in mother, 13hrs in newborn
OTHER DRUGSOTHER DRUGS
Butorphanol (synthetic narcotics) : 1~2mg – compares favorably with 40~60mg meperidine Neonatal respiratory depression ↓ Not given with meperidine (antagonizes the narcoti
c effects of meperidine) Nalbuphine Fentanyl
short acting, very potent synthetic opoid 50~100ug IV/hr, if needed
NARCOTIC ANTAGONISTSNARCOTIC ANTAGONISTS
May cause newborn respiratory depression, 2~3hrs after meperidine administration
Naloxone(narcotic antagonist) : 0.1mg/kg injected into the umbilical vein Acts within 2min with an effective duration of at lea
st 30min Repeated in 3~5min exhibits no adverse effects in the newborn
GENERAL ANESTHESIAGENERAL ANESTHESIA
Without exception, all anesthetic agents that depress the maternal CNS cross the pl and depress the fetal CNS
Aspiration of gastric contents and particulate matter
INHALATION ANESTHESIAINHALATION ANESTHESIA
GAS ANESTHETICS Nitrous oxide(N2O) : provide pain relief during labor
as well as at delivery Produces analgesia and altered consciousness Does not provide true anesthesia Does not prolong labor or interfere with Ut contractions N20 50% mixture with 50% oxygen (Nitronox) : excellent p
ain relief during the 2nd stage of labor Used as part of a balanced GA for c/sec and some force
ps deliveries
INHALATION ANESTHESIAINHALATION ANESTHESIA
VOLATILE ANESTHETICS Cause unconsciousness, potential for aspiration w
ith an unprotected airway Cross pl : producing narcosis in the fetus Isoflurane, Halothane
Potent, nonexplosive agents that produce remarkable Ut relaxation when given in high inhaled concentrations
Used for Int podalic version of 2nd twin, breech decomposition, replacement of acutely inverted Ut
Maneuver has been completed, anesthetic administration should be stopped and immediate efforts made to promote myometrial contraction to minimize hemorrhage
INHALATION ANESTHESIAINHALATION ANESTHESIA
BALANCED GENERAL ANESTESIA Nitronox given for balanced general nesthes
ia : some degree of maternal awareness Able to increase the inspired concentration
of oxygen 50% N20 + 100% oxygen + halogenated ag
ents(1%↓)
INHALATION ANESTHESIAINHALATION ANESTHESIA
ANESTHETIC GAS EXPOSURE AND PREGNANCY OUTCOME Although exact fetal risk of chronic maternal
exposure to waste anesthetic gas is unknown, available data suggest that there is not a substantial risk for either preg loss or congenital anomalies
INTRAVENOUS DRUGS INTRAVENOUS DRUGS DURING ANESTHESIADURING ANESTHESIA
THIOPENTAL Thiobarbituate, IV : widely used in conjuncti
on with other agents for GA Advantages : ease and extreme rapidity of i
nduction, ready controllability, prompt recovery with minimal risk of vomiting
Poor analgesic agents : not used as the sole anesthetic agent
INTRAVENOUS DRUGS INTRAVENOUS DRUGS DURING ANESTHESIADURING ANESTHESIA
KETAMINE IV in low doses of 0.2~0.3mg/kg : analges
ia and sedation just prior to delivery 1mg/kg : induce GA useful in women with acute hemorrhage ←
not associated with hypotension avoided in women already hypertensive unpleasant delirium and hallucinations
ASPIRATION DURING ASPIRATION DURING GENERAL ANESTHESIAGENERAL ANESTHESIA
pneumonitis from inhalation of gastric contents : m/c cause of anesthetic deaths in obstetrics
ASPIRATION DURING ASPIRATION DURING GENERAL ANESTHESIAGENERAL ANESTHESIA
PROPHYLAXIS1. Fasting from solids for at least 8 hrs and preferably long
er before anesthesia 2. Use of agents to reduce gastric acidity during the inducti
on and maintenace of GA3. Skillful tracheal intubation 4. After intubation, and during the surgery, passage of a N-
G tube to empty the stomach of all contents 5. Awake extubation with protective airway reflexes 6. Use of regional analgesia techniques when appropriate
ASPIRATION DURING ASPIRATION DURING GENERAL ANESTHESIAGENERAL ANESTHESIA
PATHOPHYSIOLOGY Rt mainstem bronchus usually offers simple
st pathway for aspirated material to reach the lung paraenchyma
Highly acidic liquid is inspired : O2 sat↓ c tachypnea, bornchospasm, rhonchi, rales, atelectasis, cyanosis, tachycardia, hypotension
ASPIRATION DURING ASPIRATION DURING GENERAL ANESTHESIAGENERAL ANESTHESIA
TREAMENT Close monitoring : attention to RR, O2 sat – most sensitive a
nd earliest indicators of injury As much as possible of the inhalated fluid should be immedi
ately wiped out of the mouth and removed from the pharynx and trachea by suction
Saline lavage : not recommended (disseminated the acid throughout the lung)
No convincing clinical or experimental evidence that corticosteroid therapy or prophylatic antimicrobial administration is beneficial
FAILED INTUBATIONFAILED INTUBATION
Uncommon, often associated with aspiration – major cause of anesthetic-related maternal mortality
REGIONAL ANALGESIAREGIONAL ANALGESIA
SENSORY INNERVATION OF SENSORY INNERVATION OF THE GENITAL TRACTTHE GENITAL TRACT
UTERINE INNERVATION Pain in the 1st stage of labor is generated largely from the Ut Visceral sensory fibers from the Ut, Cx, upper vagina → frank
enhauser ganglion(lies just lat to Cx) → pelvic plexus → mid & sup int iliac plexuses → 10th, 11th, 12th thoracic & 1st lumbar nerves
LOWER GENITAL TRACT INNERVATION Pain with vag del : arises from stimuli from the lower genital t
ract Pudendal nerve(peripheral braches of which provide sensory i
nnervation to the perineum, anus, more medial and inf parts of the vulva & clitoris) → 2nd, 3rd & 4th sacral nerves
ANESTHETIC AGENTSANESTHETIC AGENTS
Most often, serious toxicity follows injection of an anesthetic into a blood vessel, but it may also be induced by administration of excessive amounts
Two manifestations of systemic toxicity : CNS & cardiovascular system(CVS)
ANESTHETIC AGENTSANESTHETIC AGENTS
CENTRAL NERVOUS SYSTEM TOXICITY Sx : light-headedness, dizziness, tinnitus, bizarre behavior, sl
urred speech, metallic taste, numbness of the tongue and mouth, muscle fasciculation and excitation, generalized convulsions, loss of consciousness
Convulsions should be controlled, an airway established, oxygen delivered
Abnormal FHR pattern (late decelerations, persistent bradycardia) : may develop from maternal hypoxia and lactic acidosis induced by convulsions
Fetus likely will recover more quickly in utero than following immediate c/sec
ANESTHETIC AGENTSANESTHETIC AGENTS
CARDIOVASCULAR TOXICITY Do not always follow CNS involvement Develop later than those from cerebral toxicity ← induced by hi
gher blood levels of drug Characterized first by stimulation and then depression
Hypertension & tachycardia → hypotension & cardiac arrhythmias
Impaired U-P perfusion & fetal distress Turning the woman onto either side to avoid aortocaval compre
ssion Crystalloid solution : infused rapidly, IV ephedrine Emergency c/sec : maternal vital signs have not been restored
within 5 min of cardiac arrest
LOCAL INFLITRATIONLOCAL INFLITRATION
Before episiotomy and delivery After delivery into the site of lacerations
to be repaired
PUDENDAL BLOCKPUDENDAL BLOCK
PUDENDAL BLOCKPUDENDAL BLOCK
Lower vagina & post vulva Works well and is an extremely
safe and relatively simple method of providing analgesia for spontaneous delivery
PUDENDAL BLOCKPUDENDAL BLOCK
COMPLICATIONS IV injection of a local anesthetic agent : seri
ous systemic toxicity (stimulation of cerebral cortex leading to convulsions)
Hematoma Severe infection at the injection site (rare)
PARACERVICAL BLOCKPARACERVICAL BLOCK
Excellent pain relief during the 1st stage of labor
Additional analgesia is required for delivery
PARACERVICAL BLOCKPARACERVICAL BLOCK
COMPLICAITONS Fetal bradycarida : 10~70%
Within 10 min, last up to 30min Not a sign of fetal asphyxia ← usually transient and newb
orns are in most instances vigorous at birth Result form decreased pl perfusion (drug-induced Ut a. va
soconstriction & myometrial hypertonus) Should not be used in situations of potential fetal
compromise
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
VAGINAL DELIVERY Low spinal block : popular form a analgesia
for forceps or vacuum delivery Level of analgesia : 10th thoracic – correspo
nds to level of umbilicus Excellent relief from the pain of Ut contracti
on
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
CESAREAN DELIVERY Level of analgesia : extend at least 8th thor
acic – just below xiphoid process COMPLICATIONS
HYPOTENSION Develop very soon after injection of local anesth
etic agent Definition : 20% decrease from baseline
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
Vasodilatation from sympathetic blockade + obstructed venous return from Ut compression of the vena cava & adjacent large veins
Supine position : absence of maternal hypotension measured in brachial a. → pl blood flow may still be significantly reduced
Prevention : 1000ml Ringer lactate infused over 20min before spinal injection and 5mg bolus of ephedrine as needed to maintain blood pressure
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
TOTAL SPINAL BOLCKADE Excessive dose of analgesic agent Hypotension & apnea → immediately treated to
prevent cardiac arrest SPINAL (POSTPUNCUTRE) HEADACHE
22 or 24 gauage needles : 1.5% develop postdural puncture headaches
reduced by using a small-gauge spinal needle and avoiding multiple punctures
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
no good evidence that placing the woman absolutely flat on her back for several hours is very effective in preventing headache
vigorous hydration may be of value, also without compelling evidence to support its use
remarkably improved by the 3rd day and absent by the 5th
severe cases, a blood patch is effective
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
CONVULSIONS BLADDER DYSFUNCTION OXYTOCICS AND HYPERTENSION ARACHNOIDITIS AND MENINGITIS
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
CONTRAINDICATIONS TO SPINAL ANALGESIA m/c serious Cx from spinal block : hypotension Obstetrical Cx that are associated with maternal hy
povolemia and hypotension Severe preeclampsia ? Disorders of coagulation and defective hemostasis Skin or underlying tissue at the site of needle entry
is infected Neurological disorders
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
CONTINUOUS LUMBAR EPIDURAL BLOCK Complete analgesia for the pain of
labor and vaginal delivery ← block from 10th thoracic to 5th sacral dermatomes
Abdominal delivery : block 8th thoracic level ~ 1st sacral dermatome
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
COMPLICATIONS TOTAL SPINAL BLOCKADE
Dural puncture with inadvertent subarachnoid injection
HYPOTENSION Normal preg women hypotension can be prevent
ed by rapid infusion of 500-1000ml of crystalloid solution
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
CENTRAL NERVOUS STIMULATION MATERNAL PYREXIA
Mean temperature ↑ Significantly associated with neonatal sepsis evaluation a
nd antibiotic therapy Presence of pl inflammation ⇒ due to infection rather than the analgesia itself Pyrexia : associated with a higher incidence of IU infectio
n from longer 1st stage labor BACK PAIN
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
EFFECT ON LABOR Epidural analgesia usually pr
olongs the 1st stage of labor, increases the need for labor stimulation with oxytocin
EPIDURAL ANALGESIAEPIDURAL ANALGESIA Did not significantly increase cesarean deliveries in ei
ther nulliparous or parous women in any individual trial or in their aggregate
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
TIMING OF EPIDURAL PALCEMENT No increase in either operative vaginal deliv
ery or cesarean delivery with early (≤3cm dilatation) administration of epidural analgesia compared with later administration
Parkland Hospital : not begun prior to 3-5cm Cx dilatation
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
SAFETY 1968-1985, 26000 women : no maternal d
eaths CONTRAINDICATIONS
actual or anticipated serious maternal hemorrhage, infection at or near the sites for puncture, suspicion of neurological disease
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
SEVERE PREECLAMPSIA-ECLAMPSIA Ideal labor analgesia for women with severe pre
eclampsia : controversial Past two to three decades, most obstetrical ane
sthesiologists : favor epidural blockade for labor and delivery in women with severe preecalmpsia
1995, Wallace and colleagues : GA and RA are equally acceptable for cesarean delivery in women with severe preecalmpsia
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
INTRAVENOUS FLUID PRELOADING Most authorities recommend prehydration, usually
with 500~1000ml of crystalloid solution Aggressive volume replacement in severe preeclam
psia women increases their risk for pul edema, especially in the first 72 hrs postpartum
No instances of pul edema in 738 women in whom crystalloid preload was limited to 500ml
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
EPIDURAL OPIATE ANALGESIA Injection of opiates into the epidural space
to relieve pain from labor become popular → rapid onset of pain relief, decrease in shevering, less dense motor blockade
Side effect : pruritus(80%), urinary retention(55%), N/V(45%), headaches(10%)
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
COMBINED SPINAL-EPIDURAL TECHNIQUES No consensus regarding maternal Cx when
comparing spinal or epidural analgesia with combined techniques
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
Parkland Hospital : 1223 women with uncomplicated term preg(combine Vs IV meperidine) Emergency c/sec for profound fetal tachycardia Fetal bardycardia occurred within 30min None of the cases responded to conservative m
easures ⇒ avoid the combined spinal-epidural technique