obstetric analgesia and anesthesia journal

7/28/2019 Obstetric Analgesia and Anesthesia Journal

1/7

Obstetric Analgesia and Anesthesia

Gilbert J. Grant

The first modern recorded use of pain relief for childbirth was in 1847, when Dr. James Young

Simpson administered ether to facilitate vaginal delivery for a woman with a deformed pelvis.

Since that time, obstetric anesthesia practice has evolved from the use of systemic routes for

analgesic administration (inhalation, intravenous, intramuscular) to regional administration of

analgesics by the epidural and spinal routes. Currently, in the USA, more than 60% of parturients

receive regional analgesia to manage their pain of childbirth. An advantage of the regional

approach is that relatively low doses of analgesics reliably provide pain relief. Thus, the fetus is

spared exposure to the relatively large doses of medication required when the systemic approach

is used. Although the systemic route remains an option, it is currently used for a minority of

parturients. This review describes current practices in obstetric anesthesia.

Labor and Vaginal Delivery

Consequences of unrelieved pain

The pain of childbirth, which is likely to be the most severe pain that a woman experiences [1],

results in untoward physiologic effects [2]. The hyperventilation that accompanies labor pain

causes profound hypocarbia, which may suppress the ventilator drive between contractions and

produce maternal hypoxemia and loss of consciousness [3]. The accompanying respiratory

alkalosis interferes with fetal oxygenation by shifting the oxyhemoglobin dissociation curve in

favor of the mother and by producing uteroplacental vasoconstriction [4]. The neurohormonal

responses to stress and pain also conspire to adversely affect placental perfusion and fetal

oxygenation. These changes are mediated by increases in circulating catecholamines, which

decrease uterine blood flow [5]. Epidural analgesia lowers circulating maternal epinephrine, and

effectively inhibits the respiratory [6] and neurohormonal [7] responses to pain, with a resultant

increase in oxygen tension in the parturient and fetus[8]. There is also evidence that unrelieved

pain during childbirth may contribute to the development of postpartum psychologic problems

including postpartum depression [9] and post traumatic stress disorder (PTSD) [10].


2/7

Multimodal Regional Analgesia

Current methods for providing pain relief for labor and vaginal delivery are considerably

different from techniques that were used as recently as 15 years ago. Regional analgesia for

childbirth has been transformed from a one-drug approach using a local anesthetic, to an

approach in which different classes of analgesics are administered concurrently; most commonly,

a local anesthetic and an opioid. Although local anesthetics produce profound analgesia, they

indiscriminately block conduction in all nerves with which they come in contact, and therefore

also produce unwanted effects: hypotension and motor block. Hypotension may decrease fetal

oxygen delivery by reducing placental perfusions. Motor block may cause profound lower

extremity weakness, which can be very distressing for the parturient. Moreover, profound motor

and sensory block may interfere with effective pushing during the second stage, particularly if

the parturient is unable to perceive rectal or vaginal pressure, as the presence of this pressure

facilitates expulsive efforts.

The traditional approach to regional analgesia, in which a local anesthetic was used as the sole

agent, changed when clinicians recognized the analgesic efficacy of opioids administered into

the neuraxis. Unlike local anesthetics, which act by blocking nerve conduction, opioids injected

into the neuraxis inhibit pain by binding to specific spinal opioid receptors. Opioids and local

anesthetics act synergistically, so relatively low doses of each agent are required. This synergism

is the rationale for the concurrent use of a combination of different types of analgesics, and is

known as multimodal analgesia [11]. Some clinicians combine other classes of analgesics such

as those that stimulate adrenergic (e.g, epinephrine, clonidine) and cholinergic (e.g neostigmine)

receptors to further potentiate analgesia.

A distinct advantage of multimodal analgesia is that it produces fewers side effects than typically

occur when a local anasthetic is used alone. The difference causes of analgesics act through

different mechanism, and they also have distinct side effect profiles. Furthermore, the likelihoodof side effect is reduced because with the multimodal approach a relatively low dose of each

component is used. The profound motor block that was a frequent accompaniment of high

concentrations ofnlocal anesthetic does not occur with the low concentrations of local anasthetics

that are part of the multimodal approach. Hypotension, which commonly occured with epidural


3/7

administration of high concentration of local anasthetic, is also less likely to occur when low

concentrations are administered.

Prutoyus and nausea are the most common untoward effects that occur with neuraxial

multimodal analgesics regimens, and are caused by the opioid component. These side - effects

may be dose-related, and are more likely to occur with the relatively water-soluble opioid

morphine, and less likely to occur with the relatively lipopphilic opioid such as fentanyl and

sufentanil. Opioid side effect may be treated by intravenous administration of specific opioid

receptor antagonist such as naloxone,naltrexone, nalmefene, or nalbuphine. Fortunately low

doses of opioid antagonist selectively reverse the unwanted effects without appreciably affecting

the analgesia. Another side effects that may occur after intratechal injection of opioid alone is

fetal bradycardia or late decelerations of the fetal heart rate, as the result of uterine hyperactivity.

This effect is twice as likely To occur after intratechal administration of opioid alone than after

epidural administration of local anasthetic and opioid (24% vs 11%) [12]. The fetal bradycardia

may be reversed by administration of tocolytic, such as terbutaline or nitroglycerine.

For patients, the improved lower extremity mobility is perhaps the most noticable effects of

multimodal analgesia. Although commonly described as a "walking epidural", this term is a

poor descriptor, as few parturients walk much during labor after their pain is relieved.

Furthermore, the lack of motor block is not a result of the epidural approach per se, but may also

be achieved with a spinal approach, or a combined spinal and epidural (combined spinal-

epidural, CSE) approach. The primary determinant of motor block intensity is the concentration

of local anasthetic, not its site of administration.

Epidural, spinal, and combined spinal - Epidural analgesia

Safe and effective multimodal regional analgesia may be achieved by using the epidural or spinalroutes, or a combination of both. An advantage of the epidural approach is that a catheter may be

inserted into the epidural space to facilitate continuous and/or intermitten analgesic dosing to

prolong the duration of pain relief. With spinal techniques, the durationof analgesia is limited

into the duration of action of a single dose, as catheterization of the intrathecal space is rarely

performed. The onset of analgesia is more rapid with the spinal approach (3-5 minutes) than it is


4/7

with the epidural approach (approximately 10 minutes). The CSE approach offers the advantages

of both spinal and epidural techniques; rapid onset of analgesia and prolonged duration if

needed.

The type of regional analgesia chosen for a particular patient depends on many factors. One of

the most important determinants is the anticipated duration of labor. In early labor, when

delivery is not expected for many hours, catheterization of the epidural space is indicated

(epidural or CSE techniques) to establish a conduit for administering multiple doses of

analgesics. For an epidural technique, the analgesic medication is typically administered using a

continuous infusion pump, perhaps with patient- controlled epidural analgesia (PCEA; see

below) for a CsE technique, a dose of analgesics is administered intrathecalky and then a catheter

is inserted into the epidural space. The epidural analgesics may be administered either

immediately after the intrathecal injection,mor when the pain relief from the initial intrathecal

dose begins to wane.

Epidural catheterization is a sensible approach at any time during labor for parturients who have

a high likelihood of an instrumental or operatove delivery, as it permits administrationof

additional anesthetics, should they be needed.if delivery is imminent, a single-shot spinal is a

reasonable choice, because analgesia onset is rapid. However, these patients may benefit more

from a CSE technique, as it requis little additional time compared to an epidural tchnique, and an

indwelling epidural cathetermay be quite helpful. The epidural catheter may be used to

administer additional analgesics if delivery does not occur as quickly as anticipated, if the

intrathecal medication does not produce adequate analgesia, or if an instrumental or operative

delivery is required.

Patient-conolled epidural analgesia

Programmable, microprocessor-controlled infusion pumps facilitate pcise administration of

analgesics into the epidural space. Continuous infusn of analgesics is advantegeous, as it avoids

the peaks and valleys of pain and relief that occur with intermitten bolus dosing. PCEA is a


5/7

further refinement of this tchnology. Originally introduced for intravenous use, PCEA enables

the parturient to "fine-tune" her pain relief. PCEA may be administered using intermitten boluses

exclusevely, or intermitt en boluses superimposed on a backgroundinfusion, which appears to be

a superior strategy[13]. PCEA has many advantages over non PCEA techniques including better

analgesia and decreased anesthetic requirement, as well as improved patient satisfaction [14],

because the patient feels empowered by having some control over her pain relief.

Ideally, PCEA is used to provide analgesia for the duration of labor and delivery. For some

patients, the low dose delivered from the infusion pump may not be adequate for the late first

stage and second stage of labor, when a somatic pain component is superimposed on the visceral

pain input.

Analgetik dan Anastesi Obstetri

Gilbert J. Grant

Penggunaan penghilang rasa sakit untuk persalinan secara modern tercatat pertama kali padatahun 1847, saat dr. James Young Simpson memasukkan ether untuk memfasilitasi persalinan

per vaginam pada wanita dengan deformitas pelvis. Sejak saat itu, penggunaan anastesi obstetric

telah berkembang dari penggunaan jalur sistemik untuk memasukkan analgetik (inhalasi,

intravena, intramuscular) ke analgetik regional melalui jalur epidural dan spinal. Saat ini, di AS,

lebih dari 60% pasien parturient menerima analgetik regional untuk manajemen sakit saat

persalinan. Suatu keuntungan dari pendekatan regional adalah dosis rendah analgetik dapat

digunakan untuk penghilang rasa sakit. Jadi fetus tidak begitu terekspos dengan dosis

pengobatan yang relative besar seperti yang ditemui pada jalur sistemik. Walaupun jalur sistemik

tetap menjadi pilihan, biasanya digunakan hanya pada sedikit pasien, Review berikut ini

menggambarkan penggunaan penggunaan anastesi obstetrik.

Proses persalinan dan Persalinan per vaginam

Konsekuensi dari nyeri menetap

Rasa sakit pada saat persalinan, yang mungkin merupakan nyeri paling berat yang dialami oleh

perempuan, adalah efek fisiologis. Hiperventilasi yang mengikuti nyeri saat persalinan


6/7

menghasilkan hipokarbia, yang dapat menekan ventilasi antara kontraksi dan menyebabkan

hipoksemia maternal dan kehilangan kesadaran. Alkalosis respiratori penyerta berpengaruh paDa

oksigenasi fetus dengan menggeser kurva disosiasi oksihemoglobin untuk ibu dan menghasilkan

vasokontriksi uteroplasenta. Respon neurohumoral untuk stress dan nyeri juga bergabung dan

mempengaruhi perfusi plasenta dan oksigenasi fetus. Perubahan - perubahan ini dimediasi oleh

peningkatan sirkulasi katekolamin, yang menurunkan aliran darah uterin. Analgetik epidural

menurunkan sirkulasi epinefrin maternal dan secara efektif menghambat respirasi dan respon

neurohumoral terhadapmnyeri, dengan total peningkatan di tekanan oksigen pada ibu parturien

dan fetus. Bukti lain juga menunjukkkan bahwa nyeri kenetapmselama proses kelahiran dapat

berkontribusi ke perkembangan masalah psikologi post partum termasuk depresi post partum dan

post traumatic stress disorder (PTSD).

Analgetik regional multimodal

Metoda terbaru untuk penghilang rasa sakit saat melahirkan dan partus pervaginam sudah

berbeda dengan teknik yang digunakan 15 tahun yang lalu. Analgetik regional untuk persalinan

telah berubah daru penggunaan 1 jenis obat dengan anastrsi lokal ke pendekatan dengan berbagai

tipe analgetik yang berbeda yang dimasukkan secara bersamaan, yang paling umum adalah

penggunaan anestesi lokal dan golongan opioid. Walaupun anestesi lokal mempunyai efek

analgetik yang nyata, namun kerjanya adalah menghambat konduksi pada semua nervus yang

berkontak dengannya tanpa ada perbedaan sehingga juga menimbulkan efek samping seperti

hipotensi dan blok motorik. Hipotensi dapat menurukan penghantaran oksigen fetus dengan

mengurangi perfusi plasenta. Blok motorik dapat menyebaBkan kelemahan ekstremitas bawah

yang nyata dan dapat menjadi penyulit untuk ibu yang akan melahirkan. Selanjutnya blok pada

motorik dan sensorik juga terlibat pada pendorongan yang efektif saat kala II, khususnya jika ibu

inpartu tidak bisa merasakan tekanan rectal atau vaginal. Adanya tekanan - tekanan tersebut

dapat menyebabkan usaha - usaha ekspulsif.

Pendekatan lama terhadap analgetik regional dimana anastesi lokal digunakan sebagai agen

tunggal, berubah saat dokter - dokter menemulan kegunaan analgetik dari opioid yang

dimasukkan ke neuraxis. Berbeda dari anastesi lokal yang bekerja memblok konduksi nervus,

opioid disuntikkan ke neuraxis, menghambat nyeri dengan berikatan ke resptor spesifik spinal

opioid. Opioid dan anastesi lokal bekerja secara sinergis sehingga dibutuhkan dalam dosis


7/7

rendah dari masing - masing agen. Kesinergisan ini rasional untuk penggunaan bersamaan dari

kombinasi beberapa tipe analgetik yang berbeda dan dikenal dengan multimodal analgetik.

Beberapa dokter mengkombinasikan jenis - jenis analgetik lain seperti yang dapat menstimulasi

adrenergik dan reseptor kolinergik untuk analgetik potensial selanjutnya.

obstetric analgesia and anesthesia journal

Documents