Enumerate various methods for pain relief in labour and elaborate Technique, advantages and disadvantages of any one of them

                          Various methods of pain relief during labour are
                              |                                                                  |
Nonpharmacological                                                       Pharmacological

1. Childbirth Education                                               Systemic medication
2. Hydrotherapy                                                           Opiods like meperidine,fentanyl
3. Aromatherapy                                                         Sedative-Tranquiliser like barbiturate
4. Audiotherapy and massage                                     Phenothiazines and benzodiazepine
5. Psychoprophylasix                                                  Inhalational Analgesia like
6. Trancutaneous electrical nerve stimulation             Entonox 50 : 50 N₂O/O₂ mixture
7.                                                                                  Desflurane (0.2%), enflurane, and                                                                                                      isoflurane (0.2% to 0.25%)

In addition to the above pharmacological and nonpharmacogical methods there are certain regional techniques like

1. Epidural Analgesia
2. Spinal Analgesia
3. Combined Spinal-Epidural Analgesia
4. Continuous Epidural Infusion
5. Patient-Controlled Epidural Analgesia
6. Paracervical and Pudendal Blocks
7. Lumbar Sympathetic Blocks

EPIDURAL ANALGESIA

Advantages: 

• Effective pain relief and attenuation of adverse physiological response to pain 
• Reduction in maternal catecholamine levels
• Increased maternal intervillous blood flow
• Improved uteroplacental blood flow
• Can be converted into continuous epidural and patient controlled epidural analgesia
• The epidural catheter can be used to provide anesthesia in inadvertent ceaserian section and post operative analgesia of the same

DISADVANTAGES

• Hypotension
• Unintentional intravascular injection
• Unintentional intrathecal injection
• Post puncture dural headache
• Maternal fever

TECHNIQUE

Assess all patients before placement of a regional block with history, clinical examination, and evaluating the airway.Informed consent is obtained, and the patient explained the procedure and the potential complications of the technique. 

A full check of emergency equipment ,immediate availability of resuscitative drugs and an intravenous infusion  started, and appropriate maternal and fetal monitoring should be in place before starting the procedure.
Epidural technique requires placement of the needle tip into the ligamentum flavum for the loss-of-resistance and hanging-drop methods.

With a lumbar approach  Touhy 18G needle is used and  the depth from skin to the ligamentum flavum commonly approaches 4 cm, the midline, which requires needle control if unintentional dural puncture is to be prevented.The loss-of-resistance technique involves inserting the needle to the ligamentum flavum and then attaching a 3- to 5-mL glass syringe filled with 2 mL of saline and a small (0.25-mL) air bubble.  When the epidural space is entered, the pressure applied to the syringe plunger allows the solution to flow without resistance into the epidural space.
epidural catheters should be inserted only 2 to 3 cm into the epidural space for surgical or obstetric patients needing rapid onset of analgesia. Threading more catheter may increase the likelihood of catheter malposition but in obstetric patients the catheter can be inserted between 4 and 6 cm to optimize efficacy and prevent unintentional movement of the catheter during prolonged labor analgesia. Multiport (three lateral ports) or single–end-hole (uniport or distal port) catheters are available.  Despite an adequately positioned catheter during first use of a local anesthetic, each subsequent injection should be preceded by aspiration and an epidural test dose because catheter migration into vessels and the subarachnoid or subdural space does occur.

Long-acting amides such as bupivacaine or ropivacaine are most frequently used because they produce excellent sensory analgesia while sparing motor function, particularly at low concentrations (<0.1%). Analgesia for the first stage of labor may be achieved with 5 to 10 mL of bupivacaine or ropivacaine (0.125%) combined with fentanyl (50 to 100 µg) or sufentanil (5 to 10 µg).