labour pain & relief

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Co-ordinator: Dr Veena Asthana Presented by: Dr Aslam Aziz Rizvi02/12/08

DEFINITION OF LABOURLABOUR can be defined as spontaneous painful uterine contractions associated with the effacement and dilatation of the cervix and the descent of the presenting part


IASP defined PAIN as: An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.

Copyright 2003 American Society of Anesthesiologists. All rights reserved.

STAGES OF LABOURI. From onset of regular uterine contractions to full dilatation of cervix. From full cervical dilatation to delivery of the fetus.


III. From delivery of the fetus to delivery of the placenta.

Nerve supply of uterusSympathetic: Motor ( T5-T6) T5Sensory (T10-T11) (T10Parasympathetic Pelvic n. (S 2,3,4) end in ganglion of frankenhauser

1. 2.

WHY PAIN OCCURS DURING LABOUR?FIRST STAGE PAIN Visceral pain resulting from: a) Uterine contractions b) Dilatation of the cervix. Initially confined to T11-T12 during latent phase. T11Eventually involves T10-L1 in active phase. T10-

Perception begins with the nociceptive stimuli arising in the mechanical & chemo receptors in uterus & cervix High threshold mechanoreceptors d/t intense pr. generated during contraction of uterus. As the labour progresses intensity of labour pain d/t lowering of stimulation threshold with repeated stimuli. Myocellular injury d/t repeated contractions releases bradykinin, histamine, serotonin, Ach, K+ bradykinin, ions chemical nociceptors activated.

Sensations are then carried by the A & C fibres that pass through the inferior, middle & superior hypogastric plexus, the lumbar & lower sympathetic chain and end in rami communicants T10assoc. with T10-L1 spinal nerves. Dominantly carried by C fibres. fibres. Pain is transmitted slowly, poorly localized and primarily in the lower abdomen. Referred to the lumbosacral area, gluteal region & thighs as labour progresses.

Pain intensity increases with progressive cervical dilatation & increasing intensity & frequency of uterine contractions. Nulliparous & those with h/o dysmenorrhoea experience greater pain during 1st stage.


Onset of perineal pain at the end of 1st stage signals beginning of fetal descent and the 2nd stage of labour. Caused by distension of pelvic structures and perineum following descent of the presenting part. This is somatic pain. Sensory innervation of the perineum is provided by the pudendal nerve (S2-S4), so pain during this stage (S2T10involves T10-S4 dermatomes.

It is sharp, well localized and not referred. sharp, referred. More rapid descent in multiparous women is associated with more intense pain. Dominantly carried by A fibres. fibres. Pressure on intrapelvic structures usually involves fibres as high as L2 nerves & as low as S3. This is the reason parturients feel the urge to push and come to know that the baby is coming. Pain of 1st stage does not end with the start of 2nd stage but is superseded by the pain of the 2nd stage.

Copyright 2003 American Society of Anesthesiologists. All rights reserved.


Pain during labour provides a noxious and unpleasant stimulus which may prove deleterious to the mother and fetus. Various physiological effects on different organ systems may vary. They are:

A. EFFECTS ON VENTILATION:Labour pain serves as a powerful respiratory stimulant. This results in :


in TV(40%), MV(50%), RR(15%), PaCO2 by 161620mmHg with rise in pH to 7.5-7.6. 7.5Cerebral and Thus respiratory alkalosis occurs Uterine BF & shifts the maternal ODC to the left. Thus in fetal PaCO2 by 23%.

2. With the onset of relaxation phase, pain no longer stimulates respiration. So, the hypocapnia causes a transient period of hypoventilation that maternal PaCO2 by 10-50% . 10Thus inc the gradient favouring transfer of CO2. Opioids may further enhance this depression. 3. Extreme hypocapnia PaCO2 200% in levels of Adr/ Nor Ad/ Cortisol Adr/ Dopamine, cAMP, ACTH, Lactate & cAMP, Pyruvate also


2. 3. 4.


1. CO

d/t - extrusion of 250-300ml of blood from the uterus 250- ed VR from the pelvis & LL. 2. Also in sympathetic activity provoked by pain, apprehension, anxiety and the physical effort of labour. Early 1st stage: 15% in CO Late 1st stage: 30% 2nd stage : 45% Immediately after delivery: 65-80% 65During contractions: further 15-20% 15-

1. 2. 3. 4.

D. METABOLIC EFFECTS:BMR 20% FFA & Lactate (d/t CA & lipolytic metabolism) O2 consumption Progressive maternal metabolic acidosis occurs (d/t loss of HCO3 from the kidney to compensate pain induced respiratory alkalosis)

E. EFFECTS ON GASTROINTESTINAL & URINARY SYS:ed gastric acid secretion Stimulation of release of gastrin Delay in gastric & urinary bladder emptying (d/t reflex inhibition of gastrointestinal & urinary motility following anxiety)

1. 2. 3.


CA levels (d/t pain & emotional stress) Nor Ad: causes in Uterine activity Adr & Cortisol: / in-coordinate uterine contractions.

G. PSYCHOLOGICAL EFFECTS:Fear, apprehension, anxiety can further enhance pain perception. Severe pain may also produce significant post partum emotional reactions.


Safe Satisfactory pain relief for the mother No depressant effects on the maternal RS / CVS No depressant effects on the baby No unpleasant maternal side effects No depressant effects on the progress of labour High technical success rate



NON REGIONAL 1. 2. 3. 4. 5. 6.

NON- PHARMACOLOGICAL NONPsychoprophylaxis Hypnosis Massage Transcutaneous electrical nerve stimulation (TENS) Relaxation/ Breathing techniques Temperature modulation: hot/cold packs, water immersion Acupuncture Aroma therapy 9. Biofeedback

7. 8.

Psychoprophylaxis/Prepared Psychoprophylaxis/Prepared childbirth:

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Grantley Dick-Read method DickLamazes psychoprophylaxis focuses on teaching the parturient conditioned reflexes to overcome the pain & fear of childbirth. It also uses an education program, human support during labour, breathing techniques, relaxation techniques of voluntary muscles, a strong focus on attention and specific activities to concentrate on, during contractions.

Disadvantage: Since it relies on heavy breathing exercise may lead to hyperventilation & subsequent alkalosis impairment of uterine BF & CBF.

Hypnosis:Claimed to a) Reduce pain & requirement for pharmacological analgesia. b) Shorten labour. Patient is in a trance, in a state of deep concentration & very receptive to suggestion. Disadvantage: 1. May lead to post partum psychosis 2. May deprive the patient of the sense of active participation during labour


Reduces pain by nociceptive inhibition along unmyelinated small c fibres by blocking impulses to target cells at a presynaptic level in the substantia gelatinosa of the dorsal horn. Thus limiting central horn. transmission. Enhances release of endorphins & dynorphins centrally. Electrodes are placed about 2cm over the T10-L1 T10dermatomes in 1st stage & S2-S4 in the 2nd stage. S2-

Conventional TENS has high stimulation frequency (40(40150 Hz) and low intensity. Current set b/w 10-30 mA. 10- mA. The pulse duration is short (up to 50 s). s). The onset of analgesia is immediate. Pain relief lasts while the stimulus is turned on, but abates when the stimulation stops. Women can alter the amount of current supplied to the electrodes, thus providing some degree of control. However, no evidence that TENS provides more analgesia than placebo.

AcupunctureMediated through release of endorphins or serotonin Significantly reduces length of birth Reduced requirement of epidural analgesia Incomplete, unpredictable & inconsistent

1. 2. 3. 4.


INHALATIONAL ANALGESIA Adm of subanesthetic conc. of inhaled anesthetics to relieve pain ENTONOX (50% Nitrous Oxide in Oxygen) Used as a sole analgesic & adjuvant to systemic & regional tech Provides analgesia within 20-30sec of inhalation, max 20effect: 45sec

1. 2.



3. 4. 5.

Thus important that it is used at the early onset of contractions & discontinued after peak of contractions. No effect on hepatic, renal, cardiac or pulmonary functions. Safe Safe & economic but does not provide complete & predictable analgesia Lack of co-operation of patient coAtmospheric pollution S/E: Dizziness, Nausea, Dysphoria. Dysphoria.

OTHER VOLATILE ANESTHETICS Trichloroethylene, Methoxyflurane, Isoflurane(0.2%), Methoxyflurane, Enflurane(1%), Sevoflurane(2Enflurane(1%), Sevoflurane(2-3%), Desflurane(0.2%) Desflurane(0.2%) Isonox(0.2% Isonox(0.2% isoflurane + Entonox) Entonox) Advantage of subanesthetic conc: conc: a) Lack of irritation to respiratory tract b) Pleasant odour Disadvantages: a) Technical diff in safe administration & scavenging b) Requirement of specific vapourisers (c) drowsiness d) unpleasant smell (e) high cost (f) accidental overdose


OPIOID ANALGESICS: a) For parturients who request analgesia other than epidural b) Those who cannot receive neuraxial analgesia Nearly all parenteral opioid analgesics & sedatives readily cross the placenta and can affect the fetus. Other S/E: 1. CNS depression 2. Loss