LABOUR ANALGESIA

STAGES OF LABOUR

• The first stage begins with the onset of uterine contractions and ends with the complete dilation of the cervix.(cervical stage)

• The second stage of labour begins with the complete dilation of the cervix and ends with the birth of the baby. (pelvic stage )

• The third stage begins with the birth of the baby and ends with the delivery of the placenta.(placental stage)

MECHANISM OF LABOUR PAIN : THE FIRST STAGE

PATHWAY OF THE FIRST STAGE OF LABOUR

SUPRASPINAL PROJECTIONS

ANAESTHETIC IMPLICATIONS

• pain during the first stage of labour is amenable to blockade of peripheral afferents (by para cervical block, paravertebral sympathetic nerve block, or epidural block of the T10-L1 dermatomes)

• or to blockade of spinal cord transmission of pain by intrathecal injection of local anaesthetics or opioids.

PAIN IN THE SECOND STAGE OF LABOUR

• Pain during the second stage of labour reflects the activation of the same afferents activated during the first stage of labour plus afferents that innervate the vaginal surface of the cervix, the vagina, and the perineum.

• course through the pudendal nerve with DRG at S2-S4, a

• the pain specific to the second stage of labour is precisely localized to the vagina and perineum, and it is somatic in nature

ANAESTHETIC IMPLICATION

• Implications of the anatomic basis for the pain of the second stage of labour are that analgesia can be obtained by

• a combination of methods used to treat the pain of the first stage plus

• pudendal nerve block

• or extension of epidural blockade from T10 to S4.

EFFECT OF LABOUR PAIN ON THE MOTHER

Effects on the labour process

• .Provision of analgesia decreases plasma concentrations of epinephrine and its beta-adrenergic tocolytic effect on the myometrium.

• Ferguson's reflex involves neural input from ascending spinal tracts (especially from sacral sensory input) to the mid- brain, thereby resulting in enhanced oxytocin release. Some advocate that regional analgesia can inhibit this reflex and prolong labour, especially the second stage.

CARDIAC EFFECTS

• Effective analgesia results in large (50%) decreases in catecholamine concentrations in maternal blood.

• By contrast, regional anaesthetic techniques do not alter neonatal concentrations of catecholamines, which are thought to be important to adaptation to extrauterine life.

RESPIRATORY EFFECTS

EFFECT ON THE FETUS

labour pain can affect multiple systems that determine uteroplacental perfusion:

• uterine contraction frequency and intensity, by the effect of pain on the release of

oxytocin and epinephrine;

• uterine artery vasoconstriction, by the effect of pain on the release of

norepinephrine and epinephrine; and

• maternal oxy haemoglobin desaturation, which may result from intermittent hyperventilation followed by hypoventilation .

METHODS OF LABOUR ANALGESIA

NON PHARMACOLOGICAL TECHNIQUES

SYSTEMIC PHARMACOLOGICAL TECHNIQUES : OPIOIDS

NON OPIOIDS AND OTHER SEDATIVES

INHALATIONAL ANALGESIA

Nitrous oxide-administered in the form of Entonox

The pros

• Analgesic action

• No effect on uterine contraction

The cons

• Inadequate analgesia

• Possibility of diffusion hypoxia after its administration

• Possibility of neonatal respiratory depression

HALOGENATED INHALATIONAL AGENTS

• Dose dependant uterine muscle relaxation

• concern regarding pollution of the labour and delivery environment with waste anaesthetic gases;

• incomplete analgesia

• the potential for maternal amnesia

• the potential for the loss of protective airway reflexes and pulmonary aspiration of gastric contents.

INDICATION

• the ACOG and the ASA have stated that “in the absence of a medical contraindication, maternal request is a sufficient medical indication for pain relief during labour”

• Early epidural anaesthesia…………benefits versus risks.

CONTRAINDCATIONS

• Patient refusal or inability to cooperate

• Increased intracranial pressure secondary to a mass lesion

• Skin or soft tissue infection at the site of needle placement

• Frank coagulopathy

• Uncorrected maternal hypovolemia (e.g., haemorrhage)

BENEFITS OF EPIDURAL ANALGESIA

• Epidural analgesia may facilitate an atraumatic vaginal breech delivery, the vaginal delivery of twin infants, and vaginal delivery of a preterm infant

• By providing effective pain relief, epidural analgesia facilitates the control of blood pressure in pre-ecclamptic women

• Epidural analgesia also blunts the hemodynamic effects of uterine contractions (e.g., sudden increase in preload) and the associated pain response.

• Prevents hypoventilation hyperventilation syndrome

ADMINISTRATION OF EPIDURAL ANALGESIA FOR LABOR: TECHNIQUE

• 1. Informed consent is obtained, and the obstetrician is consulted.

• 2. Monitoring includes the following:

• Blood pressure every 1 to 2 minutes for 15 minutes after giving a bolus of local anaesthetic

• Continuous maternal heart rate monitoring during and after administration of the block.

• Continuous fetal heart rate monitoring during and after the procedure and

• Continual verbal communication.

• 3. The patient is hydrated with 500 mL of Ringer's lactate solution.

• 4. The patient assumes a lateral decubitus or sitting position.

• 5. The epidural space is identified with a loss-of-resistance technique.

• 6. The epidural catheter is threaded 3 to 5 cm into the epidural space.

• 7. A test dose of 3 mL of 1.5% lidocaine with 1:200,000 epinephrine is injected after careful aspiration and after a uterine contraction (to minimize the chance of confusing tachycardia that results from pain with tachycardia as a result of intravenous injection of the test dose).

• 8. If the test dose is negative, one or two 5-mL doses of 0.25% bupivacaine are injected to achieve a cephalad sensory level of approximately T10.

9. After 15 to 20 minutes, the block is assessed by means of loss of sensation to cold or pinprick

• 10. The patient is cared for in the lateral or semi lateral position to avoid aortocaval compression

• .

• 11. Subsequently, maternal blood pressure is measured every 5 to 15 minutes. The fetal heart rate is monitored continuously.

• 12. The level of analgesia and the intensity of motor block are assessed every 1 to 2 hours.

CHOICE OF LOCAL ANAESTHETIC: BUPIVACAINE

• dilute solutions of bupivacaine produces excellent sensory analgesia with minimal motor blockade. A 0.125% solution is often adequate during early labour, and a 0.25% solution is effective during active labour in most patients

• Bupivacaine is highly protein bound, which limits trans placental transfer.

• The umbilical vein :maternal vein concentration ratio is approximately 0.3.

• the reports of FHR decelerations after bupivacaine did not demonstrate adverse neonatal outcome

ROPIVACAINE

• It is difficult to justify the increased cost of ropivacaine without clear patient benefit.

• There is no definitive evidence of increased patient safety or decreased motor block when ropivacaine is used to provide epidural analgesia in labouring women,

• and there is no significant difference between ropivacaine and bupivacaine in obstetric or neonatal outcome

LEVOBUPIVACAINE

• preclinical and clinical studies have suggested that levo bupivacaine has less potential for cardio toxicity.

• However this is still to be proved by conclusive studies

LIGNOCAINE

• Lower quality of analgesia

• epidural administration of lidocaine during labour was associated with abnormal neonatal neurobehavioral

• At delivery, the umbilical vein : maternal vein lidocaine concentration ratio is approximately twice that of bupivacaine.

OPIOIDS

• epidural administration of a local anaesthetic alone can provide adequate analgesia throughout labour, but the concentration of local anaesthetic needed to maintain analgesia often results in significant motor block.

• Epidural administration of an opioid alone provides moderate analgesia during early labour, but the dose needed to maintain analgesia is accompanied by significant side effects (e.g., pruritus, nausea, perhaps neonatal depression).

CHOICE OF OPIOIDS

• lipid-soluble opioids are superior to morphine when used in combination with a local anaesthetic for epidural analgesia in labouring women. three lipid-soluble opioids—fentanyl, sufentanil, and alfentanil—may be combined with a local anaesthetics.

• sufentanil may provide slightly better analgesia with slightly less neonatal neurobehavioral depression.

MAINTENANCE OF EPIDURAL ANALGESIA

• Intermittent top up doses

• Continuous epidural infusion

• Patient controlled epidural analgesia

SPINAL ANALGESIA FOR LABOUR :SINGLE SHOT TECHNIQUE

• a single-shot subarachnoid injection of local anaesthetic is not suitable for the first stage of labour.

• A single-shot injection has a finite duration,

• and multiple injections result in an increased risk of post dural puncture headache (PDPH).

CONTINUOUS SPINAL ANALGESIA

• placed through an 18- or 19-gauge needle. Very small (e.g., 28- to 32-gauge) catheters

• were developed for insertion through small (e.g., 22- to 26-gauge) spinal needles.

• Unfortunately , several cases of cauda equina syndrome (associated with the use of spinal micro catheters during surgery in non pregnant patients) prompted the Food and Drug Administration to remove these micro catheters from the market.

SADDLE BLOCK

• advantageous in the patient with a preterm fetus or a vaginal breech presentation. In these cases, dense perineal relaxation may facilitate an atraumatic vaginal delivery.

• A saddle block also provides excellent anaesthesia for an outlet/low forceps delivery..

• The block is administered with the patient in the sitting position to promote caudal spread of the hyperbaric local anaesthetic,

• we administer the local anaesthetic immediately after a uterine contraction to decrease the likelihood of an unexpected high block

COMPLICATIONS OF NEURAXIAL OPIOIDS

• Neurotoxicity

• Sensory changes

• Nausea and vomiting

• Pruritus

• Respiratory depression

• Urinary retention

• Delayed gastric emptying

• Recrudescence of herpes simplex virus infection

FETAL OUTCOME OF NEURAXIAL OPIOIDS

• The indirect fetal effects of epidural and intrathecal opioids may be more significant.

• the mother has severe respiratory depression and hypoxemia, fetal hypoxemia and hypoxia will

• follow.

• More common is the occurrence of fetal bradycardia after intrathecal administration of a lipid-soluble opioid.

• Direct fetal effects may include intrapartum effects on the FHR as well as possible respiratory depression after delivery.

TREATMENT

• fetal bradycardia

• fetal resuscitation in utero.

(1) relief of aortocaval compression;

(2) discontinuation of intravenous oxytocin;

(3) administration of supplemental oxygen;

(4) treatment of maternal hypotension, if present; and

COMPLICATIONS OF NEURAXIAL ANALGESIA

• Hypotension

• Inadequate analgesia

• Intravenous injection of local anaesthetic

• Unintentional dural puncture

• Unexpected high block

• Extensive motor block

• Urinary retention

• backache

THE CAUSES OF A HIGH BLOCK

NEONATAL OUTCOME OF NEURAXIAL ANALGESIA

• Expectant mothers can be reassured that, although epidural analgesia may be associated with some short term maternal side effects, it does not exacerbate fetal acidosis, and if anything, may partially protect the fetus from fetal hypoxia.

INFUSION REGIMENS

COMBINED SPINAL EPIDURAL BLOCK

• Combined spinal-epidural anaesthesia: Intrathecal injection of 2.5 to 5 mg bupivacaine followed by placement of an epidural catheter for use if the spinal anaesthesia is insufficient

OTHER TECHNIQUES FOR LABOUR ANALGESIA:PARACERVICAL BLOCK

MATERNAL COMPLICATIONS

• Vasovagal syncope

• Laceration of the vaginal mucosa

• Systemic local anaesthetic toxicity

• Parametrial hematoma

• Postpartum neuropathy

• Paracervical, retropsoal, and subgluteal abscess

FETAL COMPLICATIONS

• Fetal bradycardia

Possible causes

• Reflex Bradycardia

• Direct Fetal Central Nervous System and Myocardial Depression

• Increased Uterine Activity

• Uterine and/or Umbilical Artery Vasoconstriction

• Injection of local anaesthetic into fetal scalp leading to systemic toxicity

• 1. Perform paracervical block only in healthy parturients at term

• 2. Continuously monitor the FHR and uterine activity before, during, and after performance of paracervical block.

• 3. Do not perform paracervical block when the cervix is dilated 8 cm or more.

• 4. Establish intravenous access before performing paracervical block.

• 5. Maintain left uterine displacement while performing the block.

• 6. Limit the depth of injection to approximately 3 mm.

LUMBAR SYMPATHETIC BLOCK

• Adequate analgesia for first stage of labour

• interrupts the transmission of pain impulses from the cervix and lower uterine segment to the spinal cord

• Modest hypotension occurs in 5% to 15% of patients

• systemic local anaesthetic toxicity, total spinal anaesthesia, retroperitoneal hematoma, Horner's syndrome, and postdural puncture headache (PDPH).

OTHER TECHNIQUES

• Pudendal nerve block

• Perineal infiltration