Labour  analgesia in 2020 ; predicting the future
                          Dr. Parvin Banu  D.N.B, D.A
                                          Asst  Professor
                                              CNMC  Kolkata
Labour may be the most painful experience many women ever encounter though it is also related with the most pleasant moment in a woman’s life . The experience is different for each woman but the cry  for relief  of pain is always there since time immemorial. The different  methods chosen to relieve pain depend upon  the techniques available locally and the personal choice of the patient.
As  a day can  be predicted by looking  at the morning, the  future practice of labour analgesia can be foreseen by looking at the past and present  trends.
Most popular forms of labour analgesia have been

• Inhalational  and parenteral agents
• Lumbar epidural analgesia
• Combined spinal epidural analgesia (CSE)

Past  Status Of  Inhalational And Intravenous  Agents In UK
According to a report in 2007 intravenous opioids and inhalational agents were more popular than epidural  analgesia  because –

• They  were readily  available
• They  were simple to administer
• Could be used earlier in labour

At  that point  60%  of parturients  were still using  entonox  for labour analgesia in UK [1]

Advantages  Of  Inhalational over  Intravenous  Opioids  Were

• Self administration was possible
• Reversibility of analgesia & sedation between  contractions 
• Minimal products of  metabolism  which  could  affect the fetus

The main requirements during inhalational and parenteral  opioids were-

• Quick onset  with effective labour analgesia
• To  avoid  maternal sedation
• To avoid foetal depression

Salient features of Inhalational agents

Agent	Blood gas partition coefficient	Onset	Analgesia	Maternal side effects	Effect on fetus
Entonox	0.47	Quick	Effective analgesia though not potent	Maternal drowsiness & vomiting but no hypotension	Safe
Isoflurane	1.4 (0.2% along with entonox)	Rapid	Better than entonox	Drowsiness
Desflurane	0.42	Rapid	Good	Amnesia in 23%
Sevoflurane Device used	0.69(0.8%with oxygen)	Rapid	Better than entonox	More maternal sedation than entonox

 

Salient Features Of Intravenous agents

Agents	Dose	Effect on mother	Effect on fetus
Pethidine	1mg/Kg  IM	Helpful only in 16% Increased gastric emptying time Early desaturation if used with entonox	Increased detrimental effects on fetus                After 2-3hrs decreasedHeart rate variability Respiratory depression Metabolite norpethidine also have prolonged effect
Tramadol	1-2 mg/ kg	Quick onset (10min) Action lasts 2-3hrs
Ketamine		High dose may cause respiratory compromise delirium	Diazepam lead to neonatal depression
Fentanyl		Good for labor analgesia Quick onset & offset Better administered by PCA Satisfactory analgesia but chances of vomiting	Respiratory depression
Remifentanyl	0.025-0.15 mcg/kg/min when used by PCA	Better analgesia Dose dependant sedation & respiratory depression	No effect as broken down by nonspecific esterases to nonactive metabolites

 

Past Status  Of Epidural Analgesia In UK
According to another report in 2007 [2], in spite of higher use of inhalational agents ,there was a concomitant rise in popularity of neuraxial labour analgesia in UK
Changes of practice in UK provision of regional analgesia for  labour

	1990[3]	1995[4]
Epidural rate	19.7	24
Low dose infusion (<0.1%)	28	70
Opioid with infusion	13	88
Top ups	75	40.9
Patient controlled epidural analgesia	0	6
Combined spinal epidural	0	21
Conventional test dose	100	91

Fetal & Neonatal Benefits Of Epidural Labour Analgesia

• Reduced risk of respiratory depression compared to repeat doses of systemic opioids
• Increased  utero placental blood flow in  compromised foetus eg. Preeclampsia, IUGR

Maternal Benefits Of epidural labour analgesia

• In severe preeclampsia as an adjuvant to antihypertensive therapy to stabilize blood pressure as it blunts the  haemodynamic effects of uterine contraction
• Effective pain control often benefits mother with some cardiac, respiratory, neurovascular and neurological disease
• Avoids risk of general anaesthesia with significant risk factors eg. Difficult airway, morbid obesity etc.
• Superior pain relief during 1st & 2nd stage of labour may facilitate
• Atraumatic vaginal delivery of twins and  breech presentation
• Provides anaesthesia for episiotomy & instrumental delivery
• Allows extension of anaesthesia for caesarean section

Precaution/ Safeguards  for lumbar epidural analgesia

• To avoid maternal hypotension
• To avoid motor block
• To avoid foetal depression

A segmental analgesia is produced from T10 – L1 level with low dose of dilute local anaesthetic solution eg. 0.1% bupivacaine with fentanyl 2mcg/ml in a total volume  of 10- 15 ml
Different modes of lumber epidural

• Intermittent bolus –of  above LA solution
• Continuous epidural infusion(CEI) – 0.0625 – 0.1% bupivacaine with 2 mcg/ml fentanyl  5 - 12ml/hr
• Patient controlled epidural analgesia(PCEA) – 0.0625 – 0.1% bupivacaine with 2 mcg /ml fentanyl – 5ml boluses.

Alternative agents – Levobupivacaine  0.0625 -0.1%
Ropivacaine – 0.1%
Sufentanyl – 0.25 mcg/ml (in place of fentanyl)

Combined spinal epidural analgesia (CSE)

• Subarachnoid injection  of  0.5 – 1ml of 0.25%  bupivacaine with 5- 25 mcg fentanyl
• When first top up is requested the epidural top up dose is given ie. 10 -15ml of 0.1%  bupivacaine with 2mcg/ml fentanyl [5]

       Present  trend
Epidural labour analgesia has become most popular in USA  over last few decades. The percentage of parturient receiving neuroaxial analgesia rose from 21% in 1981 to 77% in 2001[6]More over women recruited for perinatal classes with most education, income and  low parity indicated greatest preference for epidural analgesia in USA[7]
According to the observation of Rachel E Collis in 2007 continuous epidural infusion was being gradually replaced by PCEA with or without continuous background infusion in UK[2]
According to Chestnut et al[8]

• Intermittent epidural bolus leads to interruption in labour pain relief and additional workload of anaesthetists.
• Continuous epidural infusion(CEI) may lead to overdose and motor block
• Patient controlled epidural analgesia (PCEA) without continuous background infusion has fewer interruptions and lower incidence of motor blockade compared to CEI
• A background infusion along with PCEA further improves analgesia and results in fewer unscheduled interventions. There is no evidence that higher bupivacaine dose associated with  a background infusion increases motor blockade and had deleterious effect on obstetrics outcome. A typical background infusion provides 1/3  to 1/2 of total hourly dose.

 

PCEA  settings
   

Technique	Basal infusion rate(ml/hr)	Bolus dose (ml)	Lockout interval(min)
Without background infusion	0	8-12	10- 20
With background infusion	4-8	5-8	10-15

According to Chestnut et al[9] various local anaesthetic concentrations have been studied without any difference in analgesic efficacy. Higher concentration leads to higher consumption of local anaesthetics producing greater motor block. Thus a dilute local anaesthetic solution combined with opioid results in less local anaesthetic consumption and motor blockade without reduction of analgesic efficacy.
On the other hand entonox had still not lost its ground. Equipment for self administration of oxygen and nitrous oxide was introduced in England in 1934.Though entonox was proposed to be phased out  in England in 2005 due to OT pollution , it is still being used in countries like UK itself, Canada, Sweden, Australia and many other developed countries including few centres even in USA[10]

The future of labour analgesia
It is difficult to foretell the future but a few items can be identified in this regard  by looking at the evolution of labour analgesia and present trend of labour analgesia.

• Neuraxial labour analgesia

There cannot be any doubt that epidural labour analgesia will gain even more global acceptance in future with higher preference for PCEA.
In this regard modified background infusion may play a major role in future practice of PCEA.

• Computer integrated PCEA

                              It is a new delivery system of continuous background infusion where the background infusion rate changes with number Of PCEA demands in the previous hour.
As the PCEA demand per hour increases with labour pain there is a rise in background infusion rate in the next hour & vice versa. This helps in bringing down the frequent top ups.

• Programmed intermittent epidural bolus

                              It is an electronic epidural device, where the total drug administered per hour by continuous infusion is divided into intermittent boluses with fixed interval eg. 2 boluses of 5ml, 30min apart, in place of 10ml/hr.
Injection of large volume of local anaesthetic solution leads to more uniform spread resulting in less amount of anaesthetic needed. So number of rescue boluses are reduced and there is increased patient satisfaction [11]

• Use of ultrasound to localize epidural space

                              Pregnancy causes tissue oedema leading to difficulty in visualisation and palpation of anatomical landmarks. Ultrasonography is a procedural tool to aid the operator in assessment of needle insertion site, needle angle and estimated depth of the epidural space.
The depth of the space can be assessed by visualizing longitudinal plane. The point of insertion and the angle of needle can be determined by visualizing the transverse plane.
Along with rising popularity of neuraxial block there is chance of more frequent use of USG in future to aid localization of epidural space.[12]

• Inhalational agents
• Sevoflurane 0.8% in oxygen – This may hold a promising place in future for patients where epidural analgesia has either failed or  contraindicated eg. Thrombocytopenia.
• Entonox – It is difficult to predict how long entonox will last in the market. Though this is not an ideal agent , there is a strong chance that it will survive till 2020 because
• Entonox  is safe
• It is time tested
• Can be self-administered
• Can  supplement a partial or failed neuraxial block
• Can be used in mothers  who want it in the later stage of labour till the arrival of analgesia provider.
• The future of labour analgesia looks uncertain in India

At present neuraxial/ regional anaesthesia remains the gold standard method of labour analgesia. More than five decades have passed since its inception but even today it is not available to most labouring women in India, and the concept of labour analgesia is like a fairy tale to them.
High patient load in hospitals, high cost of equipment , poor doctor patient ratio are the important obstacles.Thus providing labour analgesia which is a right for every woman remains an unmet need.An awareness campaign could improve the situation with a primary role to be played by obstetricians.[13]
Before concluding  the author finds a fixed  mental make up many women in India who find ultimate fulfilment of femaleness on giving birth to a baby by coping up labour pain itself.  Last but not the least a strong belief goes that pain makes the mother child bondage even  tighter.
Looking at present  scenario the future of labour analgesia in India appears truly uncertain  in 2020. & dose not look as bright.

References
[1] Michael Wee, analgesia in labour :Inhalational & perenteral Anaesthesia & intensive care medicine UK ; July 2007 : Vol – 8 ; p 268-270
[2] Rachel E Collis, Anaesthesia in labour induction & maintainance Anaesthesia &  intensive care medicine ; UK July 2007 Vol -8 ; P265 -267
[3] Davies MW, Harrison jc, Ryan TD. Current practice of epidural analgesia during normal labour . A survey of maternity units in the United Kingdom. Anaesthesia 1993; 48:63-5
[4] Burnstein R,Buckland R, Pickett JA. A survey of epidural analgesia for labour in the United Kingdom. Anaesthesia 1999; 54: 630- 40
[5] Oxford hand book of anaesthesia, 3rd edition, p 740- 743
[6] C.R. Cambric & C.A, Wong : labour analgesia & obstetrics outcomes, Br.J. Anaesthesia (2010) 105; 150-60
[7] Mary Ann Starn et al ,exploring women’s preference for labour epidural analgesia; 2003 spring ;12(2): 16 -21
[8]Chestnut’s Obstetrics Anaesthesia: 4th edition p 450 -53
[9] Chestnut’s Obstetrics Anaesthesia: 4th edition p440 – 49
[10] US department of health & human services,Agency for health care research & quality, Effective health care programm, nitrous oxide for management of labour pain , executive summary – ang 23, 2012
[11] Wong CA , Rath JT, Sullivan JT, Scavone BM, Toledo P, McCarthy RJ- A randomised comparison of programmed intermittent epidural bolus with continuous epidural infusion for labour analgesia, Anaesth- anal 2006; 102: 904-09
[12] Dr Sarala Hooda, Recent advances in labour analgesia, ISACON CME book, 2012 p 164-71
[13] Sudha Sharma, Vinay Menia, Jyoti Beeti,Sonica Dogta – Labour analgesia;An Unmet right of labouring woman in India. J South Asian feder Obst gynae 2013; 5(1) :26 – 32