分娩镇痛.ppt

LABOR ANALGESIALABOR PAIN PATHWAYS First stage:-pain is due primarily to uterine contractions that cause stretching and thinning of the uterine cervix.-pain impulses travel via visceral afferent fibers and enter the spinal cord at the T10,T11 and L1spinal segments.-pain is generally poorly localized and is dull or cramping.LABOR PAIN PATHWAYS Second stage:-Stretching of the perineum produces additional pain,more somatic in nature,is well localized and sharp -these impulses travel via the pudendal nerves from the S2,S3andS4spinal segmentsLABOR PAIN The amount of pain experienced by a woman during labor and delivery can be influenced by many factors,including participation in childbirth preparation classes,parity,and use of oxytocinANALGESIA FOR LABOUR PAIN Psychologic techniques -hypnosis -psychoprophylaxis -positive conditioning -patient education -acupuncture -trenscutaeous electrical nerve stimulationSystemic medication Benzodiazepines -diazepan crosses the placenta rapidly,and maternal and fetal blood levels are equal within minutes of an IV dose if total maternal dosage exceeds 30mg,the drug and its active metabolite persist in pharmacological active concentrations for at least a week in the neonateSystemic Medication Diazepam -the adverse effects in neonate:.in large dose:hypotonia,lethargy,decreased feeding,and hypothermia .in small dose:reduced beat-to-beat variability.Midazolam -if it is used for induction,problem with genral body tone and body temperature of neonate seen.Systemic Medication Meperidine -peak analgesia effect occurs 40 to 50 minutes after Imand 5 to 10 minutes after IV -the duration is 3-4hours -can cause dose-dependent neonateal depression,as evidenced by prolonged time to sustained respiration,decreased Apgar scores,and abnomal results from neurobehavioral examinationSystemic Medication Fentanyl -50ug to 100ug Imand 25ugIV -peak effect(IV)3-5min and duration 30-60min -A dose of 1ug/kg Ivto the mother within 15 min of cesarean delivery did not produce adverse effects -newborn drug levels were always less than maternal levelsSystemic Medication Morphine -peak analgesic effect occurs 1-2hoursIM and 20minutesIV -duration is 4-6hours -in equianalgesia doses,morphine produces more respiratory depression of the newborn than doses meperidine -morphine is reserved for early laborSystemic medication Butorphanol and nabuphine -synthetic agonist-antagonistnarcotic analgesics -do not cause respiratory depression in labor pt -cause maternal dizziness and somnolence and adverse neonatal neurobehavioral effects -rapidly cross placenta and increase FHR(cause high out put cardiac failure)-no advantage over other opioidesSystemic Medication Ketamine -low dose Ivketamine(10-25mg,or 0.25mg/kg increments)can be used with inhaled agents to produce analgesia(which can be useful during operateive vaginal delivery or cesarean delivery)Systemic medication Inhaled analgesia -proper administion of inhaled analgesia by mask in low concentrations to prevent loss of consciousness and protective aieway reflexes.-vomiting or silent regurgitation are possible aspiration risk -nitrous oxide in 50%with oxygen,reliable analgesia has not been demonstratedRegional anesthesia Most effective -provide pain relief,keep patient awake and allow patient to participate in the labour and delivery process Unlikely to produce drug-induced depression in the fetus or mother Reduce levels of catecholamines in the mother,which may beneficial to fetusRegional anesthesia Early placement of epidural catheter helps control blood pressure with good analgesia for labor pain in pre-eclampsia patient(after well hydration and before coagulopathy occurs)It may be the means to reduce cesarean section rate in ChinaRegional anesthesia Patient preparation -IV -equipment for resuscitation and complication-O2,airways,laryngoscope,endotracheal tubes,suctioning apparatus,thiopenal or diazepam,ephedrine and naloxone-preanesthetic evaluation,OB plan and understand fetal status-BP,ECG and FHR and 500ml IV fluidRegional anesthesia Contraindications -absolute .patient refusal,infectin at the site of needle placement,overt maternal coagulopathy,and maternal hemodynamic instability -relative .preexisting neurologic disease,prior back surgery,isolated coagulation abnomalities,some cardiac diseaseRegional anesthesia Timing of administration -chestnut et.al.performed a study wherein patients were randomized to early(ie,1st request0epidural or late(waiting until at least 5cm cervical dilation).No difference in cesarean rates was found between the two groups for either spontaneous or induced labors,and the cesarean rate was low(approximately 8%)in bothRegional anesthesia Encourage early administration of epidural anesthesia in laboring women with preeclampsia Epidural anesthesia did not increase the incidence of cesarean delivery or pulmonary edema among laboring women with severe hypertensive disease Regional anesthesia One shot spinal analgesia using a lipid solu