analgesia and anaesthyesia
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
narcotic 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 least 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 pain relief during the 2nd stage of labor Used as part of a balanced GA for c/sec and some
forceps deliveries
INHALATION ANESTHESIAINHALATION ANESTHESIA
VOLATILE ANESTHETICS Cause unconsciousness, potential for aspiration
with 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
nesthesia : some degree of maternal awareness
Able to increase the inspired concentration of oxygen
50% N20 + 100% oxygen + halogenated agents(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
conjunction with other agents for GA Advantages : ease and extreme
rapidity of induction, 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 :
analgesia 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 longer before anesthesia 2. Use of agents to reduce gastric acidity during the
induction 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
simplest 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 and earliest indicators of injury As much as possible of the inhalated fluid should be
immediately 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 →
frankenhauser 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 tract Pudendal nerve(peripheral braches of which provide
sensory innervation 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, slurred 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 higher 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
compression 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
: serious 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 newborns are in most instances vigorous at birth
Result form decreased pl perfusion (drug-induced Ut a. vasoconstriction & 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 – corresponds to level of umbilicus
Excellent relief from the pain of Ut contraction
SPINAL (SUBARACHNOID) SPINAL (SUBARACHNOID) BLOCKBLOCK
CESAREAN DELIVERY Level of analgesia : extend at least 8th
thoracic – just below xiphoid process COMPLICATIONS
HYPOTENSION Develop very soon after injection of local
anesthetic 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 hypovolemia 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
prevented 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 and antibiotic therapy Presence of pl inflammation ⇒ due to infection rather than the analgesia itself Pyrexia : associated with a higher incidence of IU
infection from longer 1st stage labor
BACK PAIN
EPIDURAL ANALGESIAEPIDURAL ANALGESIA
EFFECT ON LABOR Epidural analgesia
usually prolongs the 1st stage of labor, increases the need for labor stimulation with oxytocin
EPIDURAL ANALGESIAEPIDURAL ANALGESIA Did not significantly increase cesarean
deliveries in either 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 delivery 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 deaths 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 preeclampsia : controversial Past two to three decades, most obstetrical
anesthesiologists : 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 preeclampsia 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 measures ⇒ avoid the combined spinal-epidural
technique