Whereas analgesia is maximal 30 to 45 minutes after an intramuscular injection, it develops almost immediately following intravenous administration.
Some preparations are premixed in a single cylinder (Entonox), and in others, a blender mixes the two gases from separate tanks (Nitronox). The gases are connected to a breathing circuit through a valve that opens only when the patient inspires.
a tubular introducer that allows 1.0 to 1.5 cm of a 15-cm 22-gauge needle to protrude beyond its tip is used to guide the needle into position over the pudendal nerve. . To guard against intravascular infusion, aspiration is attempted before this and all subsequent injections. .
Thiopental and similar compounds are poor analgesic agents, and administration of sufficient drug given alone to maintain anesthesia may cause appreciable newborn depression
DR. ANKITA GUPTA
DEBATE When the anesthetic effects of ether andchloroform were discovered in the mid 1800s,many members of the British clergy argued thatthis human intervention in the miracle of birth wassin against the will of God. If God had wished labor to be painless, he wouldhave created it so. According to Scripture, childbirth pain originatedwhen God punished Eve and her descendants forEves disobedience in the Garden of Eden. They believed that it was wrong to avoid the painof divine punishment.
DEBATE James Young Simpson used diethyl ether toanesthetize a woman with a deformed pelvis forchildbirth. Queen Victoria undaunted by the clergy chose oneday to use an anesthetic during labor and theclergys position crumpled like the great wall ofBerlin. The first woman anesthetized for childbirth in theUnited States was Fanny Longfellow, wife of theAmerican poet Henry Wadsworth Longfellow.
DEBATELabor results in severe pain for many women.There is no other circumstance where it isconsidered acceptable for a person toexperience untreated severe pain, amenable tosafe intervention, while under a physician’scare… Maternal request is a sufficient medicalindication for pain relief during labor.”ACOG & ASA
SIR JAMES YOUNG SIMPSON (1847) FIRST USEDANAESTHESIA IN OBSTETRICS
JOHN SNOW (1853) USED ANAESTHESIA ON QUEENVICTORIA FOR THE BIRTH OF PRINCE LEOPOLD.The inhalation lasted for 53 minutes. The chloroformwas given on handkerchief in 15 minim doses : TheQueen expressed herself as greatly relived .
NATURE OF LABOUR PAINS1st stageVisceral pain Diffuse abdominal cramping Uterine contractions T10-L12nd stageSomatic pain Perineum- sharper and more continuous Pressure or nerve entrapment-caused byfetal head, may cause severe leg or back painS2-S4
WHAT DETERMINES MATERNAL SATISFACTION Pain relief Quality of relationship with caregiver Participation in decision making Home-like birth environment Caregivers with whom they are acquaintedpersonally
The goals of labor analgesia"The delivery of the infant into the arms of a conscious and pain-free mother isone of the most exciting and rewarding moments in medicine.“
THE IDEAL LABOUR ANALGESIC Good pain relief No autonomic block (hypotension) No adverse maternal or fetal side effects No motor block No effect on labour or deliveryno increase in caessarean orinstrumental deliveries Patient can ambulate Economical
Sensory innervation of upper genital tract Pain during the first stage of labor is generatedlargely from the uterus cervix & upper vagina. Visceral sensory fibers traverse through theFrankenhäuser ganglion, and enter into the pelvicplexus and then into the middle and superiorinternal iliac plexuses. From there, the fibers travel in the lumbar andlower thoracic sympathetic chains to enter thespinal cord through the white rami communicantesassociated with the T10 through T12 and L1 nerves. Early in labor, the pain of uterine contractions istransmitted predominantly through the T11 andT12 nerves.
Sensory innervation of lower genital tract Pain in second stage of vaginal delivery arises fromstimuli from the lower genital tract. These are transmitted primarily through thePudendal nerve, the peripheral branches of whichprovide sensory innervation to the perineum, anus,and the more medial and inferior parts of the vulvaand clitoris. sensory nerve fibers of the pudendal Nerve arederived from ventral branches of the S2 through S4nerves.Note:The motor pathways to the uterus leave the spinal cord at the level ofT7 and T8 vertebrae. Theoretically, any method of sensory block that doesnot also block motor pathways to the uterus can be used for analgesiaduring labor.
METHODS OF LABOUR PAIN RELIEFPHARMACOLOGICAL NON PHARMACOLOGICAL1)SYSTEMIC PSYCHOPROPHYLAXIS+ BREETHING EXERCISESPARENTRAL HYPNOSISNARCOTICS TENSTRANQUILISERS ACCUPUNCTUREINHALATIONAL HYDROTHERPYN2O ELECTRO ANALGESIAMETHOXYFLURANE AUDIO ANALGESIAENFLURANEISOFLURANE2)REGIONALEPIDURALSPINALPUDENDAL BLOCKPARACERVICAL BLOCK3) GA4) LA or PERINEAL INFILTERATION
NON PHARMACOLOGICALMETHODS:Psych prophylaxis & breathing exercise: Lamaze technique. Principal concept is to have natural child birth. Antenatal education of patient about physiology ofchild birth. Relaxation exercises to overcome fear and anxiety-reduces oxygen demand and reduces CO2production.
Breathing exercises during different stages oflabourin early labour – deep breathingtowards the end of 1st stage – morerapid breathingDuring bearing down – breath holding Constant human support during labour. Delivery in semi darkness.
Hypnotherapy Mongan method also known as Hypno Birthing, Hypnobabies, Natal Hypnotherapy and the GentleBirthprogram can significantly shorten labor, reduce pain and reducethe need for intervention, produced higher apgarscores, reduce the incidence of postpartum depressionand increase the incidence of spontaneous deliveries. No studies abort its efficacy.
TENS TENS (transcutaneous electrical nerve stimulation). A maternity TENS machine consists of a hand-held controllerconnected by two sets of fine leads to four sticky pads. These areplaced on your back. The machine gives out little pulses of electrical energy that reachyour skin via the leads and pads. The pulses may give you a tingling or buzzing sensation, dependingon the setting stimulates the release of endorphins. Controls pain via Gate control. Most useful in labour before the pain becomes too intense. drug dose requirements may be less.
WATER BIRTHING Soviet researcher Igor Charkovsky and Frenchobstetrician Frederick Leboyer developed in1960s Practices in United States, Canada, Australia,and New Zealand, as well as many Europeancountries, including the United Kingdom andGermany By 2005, over 9000 hospitals in the US and morethan three-quarters of all NHS hospitals (UK)provided this option.
Provides pain relief and a less traumatic birthexperience for the baby Redistribution of blood volume, which stimulatesthe release of oxytocin and vasopressin (Katz 1990) Aid stretching of the perineum, slows crowning ofthe infants head, reduces the use of episiotomy a decrease in perinatal mortality (1.2 per 1,000for waterbirth vs. 4 per 1,000 for conventionalbirth) during 1994-1996 in the UK. The buoyance of water provides supports andrelaxes the ligaments and tissues of motherwhich helps mother in taking comfortableposition during labour.
Risks to the infant such as infection and waterinhalation? "there are no valid reports of infants deaths due towater aspiration or inhalation" (Harper 2000) Slowed labor? A decrease in the intensity ofcontractions. Maternal blood loss? - Difficult to assess. The amount of blood loss reduced due to lowering BPand heart rate.
MUSIC: Ancient Greeks played soothing instrumental musicto women in labor. Alters mood, reduces stress and promotes positivethoughts. A trigger for a breathing response or as a cue forrelaxation. used as a distraction.
MASSAGE Touch has been associated with the power ofhealing since the beginning of civilization a source of counter-stimulation Examples; Therapeutic massage (eg:shiatsu), perineal massage
METHOD OF TOUCH AND MASSGAE lightly stroking the abdomen. vigorously firm stroking where it hurts most. firm circular massage using the palm of the hand overthe center of the back or sacrum. rhythmical squeezing and letting go of the shouldermuscles . a long stroke down the length of the back, buttocks anddown the back of the legs. stroking across the forehead, down the neck and downthe arms . simply holding hands!!!
SHIATSUJapanese form of therapeutic massage. Shiatsu means‘finger pressure’.Similar to acupuncture.Pain-relieving pressure points (‘tsubo’) are stimulatedwithout the use of needles
ACCUPUNCTURE: Traditional form of Chinese medicine. Involves insertion of needles at selected points toget desired results. Mechanism is via endorphin release and Gatecontrol theory. Produces hypo analgesia but complete relief isnever achieved . Pain relief without the support of narcotics is verypoor. Advantages –no harmful effectno effect on uterine contractions Disadvantages- time consuminglimits patients movementsterile aseptic techniques
PHARMACOLOGIC METHODS:PARENTRAL AGENTS When uterine contractions and cervical dilatationcause discomfort, pain relief with a narcotic suchas meperidine, plus one of the tranquilizer drugssuch as promethazine, is usually appropriate. the mother should rest quietly betweencontractions. discomfort usually is felt at the acme of aneffective uterine contraction, but the pain isgenerally not unbearable.
Meperidine and Promethazine Meperidine, 50 to 100 mg, with promethazine, 25mg, may be administered intramuscularly atintervals of 2 to 4 hours. Rapid effect is achieved by giving meperidineintravenously in doses of 25 to 50 mg every 1 to 2hours. * Meperidine readily crosses the placenta, and itshalf-life in the newborn is approximately 13 hoursor longer (American College of Obstetricians andGynecologists, 2002). Its depressant effect in the fetus follows closelybehind the peak maternal analgesic effect.
According to Bricker and Lavender (2002),meperidine is the most common opioid usedworldwide for pain relief from labor. Women randomized to self-administered analgesiawere given 50-mg meperidine with 25-mgpromethazine intravenously as an initial bolus.Thereafter, an infusion pump was set to deliver 15mg of meperidine every 10 minutes as needed untildelivery. Neonatal sedation, as measured by needfor naloxone treatment in the delivery room, wasidentified in 3 percent of newborns.
Butorphanol (Stadol) This synthetic narcotic, given in 1- to 2-mg doses The major side effects are somnolence, dizziness,and dysphoria. Neonatal respiratory depression is reported to beless than with meperidine, but care must be takenthat the two drugs are not given contiguouslybecause butorphanol antagonizes the narcoticeffects of meperidine. Angel and colleagues (1984) and Hatjis and Meis(1986) described a sinusoidal fetal heart ratepattern following butorphanol administration.
Fentanyl This short-acting and potent synthetic opioid maybe given in doses of 50 to 100 g intravenously everyhour. Its main disadvantage is a short duration of action,which requires frequent dosing or the use of apatient-controlled intravenous pump. Atkinson and associates (1994) reported thatbutorphanol provided better initial analgesia thanfentanyl and was associated with fewer requestsfor more medication or for epidural analgesia.
NOTE :Parenteral sedation is not without risks. Hawkins and colleagues(1997b) reported that 4 of 129 maternal anesthetic-related deaths werefrom such sedation—one from aspiration, two from inadequateventilation, and one from overdosage.Narcotics used during labor may cause newborn respiratory depression
INHALATIONAL AGENTS:N20:A self-administered mixture of 50-percent nitrous oxide (N2O)and oxygen provides satisfactory analgesia during labor.*The use of intermittent nitrous oxide for labor pain has beenreviewed by Rosen (2002a) and the following techniquesuggested: Instruct the woman to take slow deep breaths and to begininhaling 30 seconds before the next anticipated contractionand to cease when the contraction starts to recede Remove the mask between contractions and encourage herto breathe normally. No one but the patient orknowledgeable personnel should hold the mask Instruct a caregiver to remain in verbal contact with thepatient Provide the expectation that the pain will likely not beeliminated, but that the gas should provide some relief Ensure intravenous access, pulse oximetry, and adequatescavenging of exhaled gases
REGIONAL BLOCK Various nerve blocks have been developed over the years to provide pain reliefduring labor and delivery. They are correctly referred to as regional blocks.
Pudendal Block This block is a relatively safe and simple method ofproviding analgesia for spontaneous delivery. The end of the introducer is placed against the vaginalmucosa just beneath the tip of the ischial spine. Theneedle is pushed beyond the tip of the director into themucosa and a mucosal wheal is made with 1 mL of 1-percent lidocaine solution or an equivalent dose ofanother local anesthetic. The needle is then advanced until it touches thesacrospinous ligament, which is infiltrated with 3 mL oflidocaine. The needle is advanced farther through the ligament*Another 3 mL of solution is injected into this region. Next, the needle is withdrawn into the introducer,which is moved to just above the ischial spine. Theneedle is inserted through the mucosa and 3 more mL isdeposited. The procedure is then repeated on the other side.
Paracervical Block This block usually provides satisfactory pain reliefduring the first stage of labor. Not use it routinely because the pudendal nervesare not blocked, Additional analgesia is required for delivery. For paracervical blockade, usually lidocaine orchloroprocaine, 5 to 10 mL of a 1-percentsolution, is injected into the cervix laterally at 3and 9 oclock. Bupivacaine is contraindicated because of anincreased risk of cardiotoxicity (American Academyof Pediatrics and American College of Obstetriciansand Gynecologists, 2007; Rosen, 2002b). Relatively short acting, paracervical block mayhave to be repeated during labor.
Spinal (Subarachnoid) Block Introduction of a local anesthetic into thesubarachnoid space to effect analgesia . Advantages include a short procedure time, rapidonset of blockade, and high success rate. Smaller subarachnoid space during pregnancy,(engorgement of the internal vertebral venousplexus) the same amount of anesthetic agent in thesame volume of solution produces a much higherblockade in parturients than in nonpregnantwomen. Low spinal block can be used for forceps or vacuumdelivery. The level of analgesia should extend to the T10dermatome(umbilicus).
Several local anesthetic agents have been used forspinal analgesia. Addition of glucose to any ofthese agents creates a hyperbaric solution, which isheavier and denser than cerebrospinal fluid. A sitting position causes a hyperbaric solution tosettle caudally, whereas a lateral position will havea greater effect on the dependent side. Lidocaine given in a hyperbaric solution producesexcellent analgesia and has the advantage of arapid onset and relatively short duration.Bupivacaine in an 8.25-percent dextrose solutionprovides satisfactory anesthesia to the lowervagina and the perineum for more than 1 hour..
COMPLICATIONS: Hypotension Postdural puncture headache Failed regional blockade High spinal blockade Chemical meningitis or epidural abscess orhematoma
CONTRAINDICATIONS Refractory maternal hypotension Maternal coagulopathy Maternal use of once-daily dose of low-molecular-weight heparin within 12 hours Untreated maternal bacteremia Skin infection over site of needle placement Increased intracranial pressure caused by a masslesion
LOCAL INFILTRATION Local infiltration refers to the injection of ananesthetic medicine (such as Lidocaine/Xylocaine)into a specific area of the body. For use during labor, the anesthetic is injected justunder the skin surrounding the opening of thevagina. This method is used mainly during normal vaginaldelivery, episiotomy (cutting of the perineum), andrepair of episiotomy or tears. While simple to administer, local infiltration withanesthetic is not risk-free and rarely may beassociated with poisoning and inadvertentadministration of the drug to the baby. It works only at the site of injection and does notalleviate pain caused by contractions or pelvicfloor stretching.
General Anesthesia The increased safety of regional analgesia hasincreased the relative risk of general anesthesia. The case-fatality rate of general anesthesia forcesarean delivery is estimated to be approximately32 per million live births compared with 1.9 permillion for regional analgesia (Hawkins andassociates, 1997b).
Patient PreparationPrior to anesthesia induction, several steps should be taken tohelp minimize the risk of complications for the mother andfetus. These include the use of Antacids Uterine Displacement- The uterus may compress the inferiorvena cava and aorta when the mother is supine. With lateraluterine displacement, the duration of general anesthesia hasless effect on neonatal condition than when the womanremains supine (Crawford and colleagues, 1972). Preoxygenation- Because functional reserve lung capacity isreduced, pregnant women become hypoxemic more rapidlyduring periods of apnea than do non pregnant patients. To minimize hypoxia between the time of muscle relaxantinjection and intubation, it is important first to replacenitrogen in the lungs with oxygen. This is accomplished by administering 100-percent oxygenvia face mask for 2 to 3 minutes prior to anesthesiainduction.
Induction of Anesthesia Thiopental- This thiobarbiturate givenintravenously is widely used and offers easy andrapid induction, prompt recovery, and minimal riskof vomiting.. Ketamine- This agent also may be used to render apatient unconscious. Doses of 1 mg/kg inducegeneral anesthesia. Or, intravenously in low doses of 0.2 to 0.3 mg/kg,ketamine may be used to produce analgesia andsedation just prior to vaginal delivery. It usually causes a rise in blood pressure, and thusit generally should be avoided in women who arealready hypertensive. Unpleasant delirium and hallucinations arecommonly induced by this agent.
Intubation Immediately after a patient is renderedunconscious, a muscle relaxant is given to aidintubation. Succinylcholine, a rapid-onset and short-actingagent, commonly is used. Cricoid pressure—the Sellick maneuver—is used bya trained assistant to occlude the esophagus fromthe onset of induction until intubation iscompleted. Before the operation begins, proper placement ofthe endotracheal tube must be confirmed.
Gas Anesthetics- Once the endotracheal tube issecured, a 50:50 mixture of nitrous oxide andoxygen is administered to provide analgesia. A volatile halogenated agent is added to provideamnesia and additional analgesia. Volatile Anesthetics- The most commonly usedvolatile anesthetics in the United States includeisoflurane and two of its derivatives, desfluraneand sevoflurane. They are usually added in low concentrations tothe nitrous oxide-oxygen mixture to provideamnesia. They are potent, nonexplosive agents that produceremarkable uterine relaxation when given in highconcentrations.