Analgesia and anaesthyesia

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


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


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%↓)


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


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


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


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)


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


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


Lower vagina & post vulva Works well and is an extremely

safe and relatively simple method of providing analgesia for spontaneous delivery


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


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


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


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


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


CONVULSIONS BLADDER DYSFUNCTION OXYTOCICS AND HYPERTENSION ARACHNOIDITIS AND MENINGITIS


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


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


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


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


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


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


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


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 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%)


COMBINED SPINAL-EPIDURAL TECHNIQUES No consensus regarding maternal Cx

when comparing spinal or epidural analgesia with combined techniques


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

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Analgesia and anaesthyesia