Non Obstetric Surgery in

Pregnant Patients

Dr. Sudip Kumar Saha

DA student

Department of

Anaesthesiology

SSMCMH, Dhaka

Introduction

Anaesthesiologist who care for pregnant patient undergoing non-obstetric surgery must provide safe anesthesia for both mother & fetus.

To maintain maternal safety the physiological & anatomical changes of pregnancy must be considered, anesthetic technique & drug administration modified accordingly.

Fetal wellbeing is related to avoidance of fetal asphyxia & teratogenic drugs & preterm labour.

Goals of an

Anaesthesiologist Optimization & maintainance of

normal maternal physiological function.

Optimization & maintainance of uteroplacental blood flow & O2 delivery.

Avoidance of unwanted drug effects on the fetus.

Avoidance of stimulating myometrium.

Avoidance of awareness during GA.

Using regional anesthesia , if possible.

Incidence

0.75% to 2% of pregnant women undergo

surgeries

75,000 – 80,000 procedures annually in USA

Centralized data unavailable in Bangladesh

Conditions common to this age group: Ovarian

cysts, appendicitis, cholelithiasis, cervical

incompetence, breast or other

malignancies, traumatic injuries.

Commonest surgery- Appendicectomy.

Incidence

23%

35%

42%

Distribution of surgery according to trimesters

1st Trimester

2nd Trimester

Trimester breakdown of nonobstetric surgery undertaken during pregnancy.

Modified from Mazze RI, Kallen B. Am J Obstet Gynecol 1989;161:1178–85.

Most common surgical procedures

performed in pregnant women

Type of

surgery

1st trimester 2nd trimester 3rd trimester

C.N.S. 6.7% 5.4% 5.6%

E.N.T. 7.6% 6.4% 9.5%

Abdominal 19.9% 30.1% 22.6%

Genitourinary/

Gynaecological

10.6% 23.3% 24.3%

Laproscopic 34.1% 1.5% 5.6%

Orthopaedics 8.9% 9.3% 13.7%

Endoscopy 3.6% 11% 8.6%

Skin 3.8% 3.2% 4.1%

Adapted from Mazze RL, Kallen B: Reproductive outcome after anaesthesia

and surgery during pregnancy: A registry study of 5,405 cases, Am J Obstet

Gynecol 161:1178-1185, 1989

Surgeries in pregnancy

Directly related to pregnancy -

◦ Eg: Cervical encirclage

Indirectly related to pregnancy -

◦ Eg: Ovarian Cystectomy

Not related to pregnancy -

◦ Eg: Appendicectomy, Intestinal

obstruction

4 areas of unique concern

Maternal Safety

Avoidance of

intrauterine asphyxia

Avoidance of

teratogenicdrugs

Prevention of preterm

labour

PHYSIOLOGICAL &

ANATOMICAL CHANGES

DURING PREGNANCY.

Maternal safety

Cardiovascular changes

CO increase in pregnancy by 50% due to combined increase in HR(25%) & SV(30%).

SVR decreased due to oestrogen & progesterone.

ECG changes occur in pregnancy are entirely normal include left axis deviation & ST/T changes. Heart murmur are also common due to turbulence associated with increased blood flow.

RCV increase 35-50%.

Pregnancy is a hypercoagulable state with an increase in most clotting factor. Platelet count fall but an increase in platelet consumption occur.

Pregnancy is a significant risk factor for thromboembolism.

Respiratory & GIT changes:

Oxygen consumption increases upto60% at term.

MV increases early due to an increase in RR & tidal volume &is up by 45%. Increased MV is mediated by progesterone which acts as a respiratory stimulant. Increased MV causes resp. alkalosis.

FRC is decreased in pregnancy. Circulating progesterone reduces the

LOS tone, increasing the incidence of esophageal reflux..

Drugs: altered pharmacokinetics/

pharmacodynamics The MAC of volatile agents is reduced

by 30% under the influence of progesterone.

There is a decrease in plasma cholinesterase level by 25%.

The increased blood volume causes physiological hypoalbuminemia.

The volume of epidural & subarachnoid space is reduced due to the gravid uterus compressing the IVC causing distension of epidural venous plexus.

Remember the following

manoeuverRemembering left lateral tilt to

prevent aortocavalcompression.

Remembering meticulous pre-oxygenation to prevent hypoxia.

Remembering antacid prophylaxis & RSI to reduce

risk of aspiration.

Anaesthesia Considerations

First “Rule of Thumb”

Administer drug to the patient only if benefits

clearly outweigh the risk, both to the mother and

the fetus

Planning the Anaesthesia Regimen

depends on-

1. Patient‟s present surgical status

2. Present gestational age of the fetus

3. Pregnancy induced physiological changes

4. Other coexisting co-morbidities

Emergencies will always outweigh the concern for the fetus

„The parturient is the primary patient‟

The regimen that has been chosen should cater to..

Needs of the Patient„Physical and emotional status of the patient dictates the regimen‟

Needs of the Operating Surgeon„Often the anaesthetic regimen that will optimize the positioning and surgical exposure‟

Needs of the Obstetrician„May need a regimen that causes uterine relaxation‟

Anaesthesia Considerations

Choice of Anaesthesia

Both General and Regional anaesthesiahave been used successfully in pregnant patients.

No technique has been proven to have superiority over the other in fetal outcomes.

Each technique has its own advantages and disadvantages and the selection of technique is based on maternal condition, site and nature of surgery and available resources.

Subarachnoid Block

Advantages Minimal amount of Local Anaesthetics

Rapid onset of anaesthesia

Definitive end point

Easy to administer

Dense Blockade

Disadvantages Hypotension, sometimes profound

Non rectifiable dermatomal level

PDPH

Limited post op analgesia as compared to epidural

More incidence of nausea/vomiting

Epidural Block

Advantages Minimal risk of severe hypotension

Rectifiable dermatomal level

Excellent post op analgesia

Risk of meningitis and PDPH eliminated

High level of haemodynamic stability

Disadvantages Procedure is more complex/skilled

Onset of action is slower

Amount of local anaesthetic required is more

Higher incidence of failure/partial action/sparing

Less profound block

General Anaesthesia

Advantages Definitive

Easy to titrate the depth

Best uterine relaxation

Risk of meningitis and PDPH eliminated

High level of haemodynamic stability

Disadvantages Possible teratogenic effect

Maternal risk of aspiration

High incidence of post op pain, nausea and vomiting

• Most serious risk during non-obstetric surgery is intrauterine asphyxia

• Causes of hypoxia: Difficult intubation, esophageal intubation, pulmonary aspiration, high levels of regional block, systemic local anesthetic toxicity or airway compromise from trauma

• Causes of decreased uteroplacentalperfusion: Aortocaval compression, high level of spinal or epidural blockade, hemorrhage, hypovolemia, hyperventilation, high dose of ά adrenergic agents or increased circulating catecholamines, uterine hypertonus from ketamine >2mg/kg in early pregnancy or toxic doses of local anesthetics.

Effects of anaesthesia on Foetus

Intrauterine foetal asphyxia

Avoided by maintaining the

following variables of foetal respiration-

• Maternal oxygenation

• Maternal CO2 tension

• Uterine blood flow

Consensus Statement

Approved by American Society of Anaesthesiologists (ASA) and American College of Obstetricians and Gynecologists (ACOG) on Oct 21, 2009

The following generalizations have been made: -

1. No currently used anaesthetic agents have been shown to have any teratogenic effects in humans when using standard concentrations at any gestational age.

2. Fetal heart rate monitoring may assist in maternal positioning and cardio-respiratory management, and may influence a decision to deliver the fetus.

Recommendations include..

It is mandatory to obtain an obstetric consultation before performing any non obstetric surgery or any invasive procedures

A pregnant woman should never be denied indicated surgery, regardless of trimester.

Elective surgery should be postponed until after delivery.

If possible, non-urgent surgery should be performed in the second trimester when preterm contractions and spontaneous abortion are least likely.

Recommendations for foetal

monitoring include.. Surgery should be done at an institution with neonatal

and pediatric services.

An obstetric provider with cesarean delivery privileges should be readily available.

A qualified individual should be readily available to interpret the fetal heart rate.

General guidelines for fetal monitoring include –

In a previable foetus - ascertain the fetal heart rate by Doppler before and after the procedure.

In a viable foetus - simultaneous electronic fetal heart rate and contraction monitoring, before and after the procedure to assess fetal well-being and the absence of contractions.

The fetus is viable, it is advisable to obtain informed consent to emergency cesarean delivery.

When to do the surgery??

It depends on balance between maternal and foetal risk urgency of the surgery

1st trimester – Organogenesis◦ Increased foetal risk for teratogenesis

3rd trimester – Peak of physiological changes of pregnancy◦ Increased maternal risk

Thus 2nd trimester is considered to be a ideal time for non emergency, mandatory surgeries

When to do the surgery??

Carvalho B, Anesth Analg Suppl IARS

2006

Teratogenecity: general

Fetal risk: 0-15 days- usually

embryotoxic(EGA 2-4 wks)

15-60 days(organogenesis)- great risk

to fetus.

Then functional defecit.

Nearly all drugs have been

demonstrated to be teratogenic in

some species at some dose.

Teratogenecity:

BZD/Opioids BZD/Minor tranquilizer: Associated

with increased anomalies. BZD

initially associated with increased cleft

palate.

FDA: Minor tranquilizer should almost

always be avoided in 1st trimester.

Single dose: no effect.

Synthetic opioids : Animal studies not

teratogenic.

Teratogenecity:

Muscle relaxant & LA Muscle relaxant: minimal placental

transfer.

LA(local anesthetics): no evidence of

problem in human.

Cocaine: is a known teratogen.

IUGR, preterm delivery, & increased

risk of abruptio placenta.

Teratogenecity:

induction agent Ketamine: not teratogenic but

>1mg/kg- increased risk of preterm

labour.

Thiopental Na: not teratogenic in

conventional doses.

Propofol: no adverse fetal effects

compared to thiopental.

Propofol+Succinylcholine may cause

severe maternal bradycardia.

Teratogenecity: N2O

Theoretical risk is decreased but

reversible DNA synthesis.

Pretreatment with folinic acid is not

proven effective in preventing

neurogenic teratogenecity in animal.

Conclusion: teratogenic only under

extreme condition. However slightly

increased abortion risk.

Teratogenecity:

inhalational agent Volatile anaesthetic: shows

teratogenecity in some species.

Volatile anaesthetic & N2O in rats

showed no anomaly at any gestational

age.

Like N2O , slightly increased risk of

abortion.

F.D.A classification of risk of

teratatogenicity of drugs (1979)Category Clinical Implications

Category A Adequate and well controlled studies have failed to demonstrate a

risk to the foetus in the first trimester of pregnancy (and there is no

evidence of risk in later pregnancies)

Category B Animal reproduction studies have failed to demonstrate a foetal risk

but there are no controlled studies in pregnant women, OR animal

reproduction studies have shown an adverse effect, but adequate

well controlled studies in pregnant women have failed to demonstrate

a risk to the foetus in any trimester.

Category C Animal reproduction studies have shown an adverse effect on the

foetus and there are no adequate well controlled studies in humans,

or studies in animals and humans are not available. Potential benefits

of drugs may warrant use of drug in pregnant women despite

potential risks.

Category D There is positive evidence of human foetal risk, but the benefits from

use in pregnant women may be acceptable despite the risk (e.g. life

threatening situation or serious disease for which safer drugs are not

available).

Category X Studies in animals or humans have demonstrated foetal

abnormalities, or evidence based on human experience, and the risk

of use of the drug in pregnant women clearly outweighs any possible

benefit. The drug is contraindicated in women who are or may

become pregnant.

Documented teratogens(Adapted: ACOG Educational Bulletin #236, 1997)

ACE inhibitors Lithium

Alcohol Mercury

Androgens Phenytoin

Antithyroid drugs Radiation (>0.5 Gy)

Carbamazepine Streptomycin/kanamycin

Chemotherapy agents Tetracycline

Cocaine Thalidomide

Coumadin Trimethadione

Diethylstilbestrol Valproic acid

Lead Vitamin A derivatives

Intra-operative monitoring

BP,HR,RR

ECG

SpO2ETCO2

FHR

Special situations - Trauma

Among the leading causes of maternal mortality/morbidity

Maternal life takes precedence over foetallife.

Primary management goals (Fluid resuscitation/Airway management) is similar to non pregnant females.

Mother should receive all diagnostic tests deemed necessary for her optimal management, shielding the foetus when possible.

More prone to pulmonary oedema due to relative hypoproteinemia & hypervolemia

Conservative, CVP guided fluid therapy is recommended

Early USG – Foetal viability, monitoring to continue

Avoid – Hypoxia, Hypotension, Hypothermia and Acidosis

Causes of foetal loss –◦ Maternal mortality

◦ Abruption

Indications for emergency Caesarean section in pregnant trauma patient: -1. Traumatic uterine rupture

2. Haemodynamically stable mother with foetal distess

3. Gravid uterus that is interfering with intraoperativesurgical repair

Special situations - Trauma

It is no longer considered to be a contraindication to laparoscopic surgery

Concerns in Laparoscopic surgeriesPneumoperitoneum with trendelenberg position

Reduced lung compliance and FRC.

Increased airway pressures

Hypoxia in advanced gestation.

Pneumoperitoneum with reverse trendelenberg position

Significant aorto venacaval compression

Reduced venous return & hypotension.

Pregnancy is a prothrombotic state.

Lower extremity venous stasis due to pneumoperitoneum- higher risk of thromboembolism

Special situations –

Laparoscopy

Recommendations for Laproscopy1. Use an open technique to enter the abdomen to

avoid potential uterine or fetal trauma.

2. Monitor maternal end-tidal CO2 (30–35 mmHg range) arterial blood gas (if the procedure is prolonged) to avoid fetal hypercarbia and acidosis

3. Maintain low pneumoperitoneum pressures (8–12 mm Hg, not 15 mm Hg)

4. Minimize insufflation time or use a gasless technique to avoid decreases in uteroplacentalperfusion

5. Protect the uterus with lead shielding during intraopradiological procedures (Cholangiography)

6. Limit the extent of Trendelenburg and reverse Trendelenburg positions. Initiate any position changes slowly. Left lateral tilt is to be maintained.

7. Pneumatic stockings to be used

8. Monitor fetal heart rate and uterine tone when feasible

Special situations –

Laparoscopy

Laparoscopic Vs Open

Appendicectomy A study was designed in USA (2007)

have shown that laparoscopic appendicectomy in pregnancy is associated with a low rate of intra-operative complication & less requirement of postoperative analgesia in all trimester. However, laparoscopic appendicectomy is associated with a significantly higher rate of fetal loss compared to open appendicectomy.

Open appendicectomy would appear to be the safer option for pregnant women for whom surgical intervention is indicated.

Aneurysm clipping may be needed during pregnancy.

Meningiomas have steroidal receptors, it increases in size during pregnancy due to vascular proliferation and increased intravascular volume.

Fetal monitoring is necessary when blood loss, large volume shifts and hypotension is expected

Placental circulation has poor autoregulation. It depends on systemic pressure.

Reduction in systolic pressures > 20-30% or MAP<70 mmHg, reduces placental blood flow.

Special situations - Neurosurgery

SNP in doses > 0.5mg/kg/hr can cause

cyanide toxicity in the foetus. NTG is a safer

option.

Maternal hyperventilation and resultant

hypocarbia (pCO2 < 25mmHg) shifts the

oxyhaemoglobin curve to the right and

hampers fetal oxygenation.

Osmotic diuresis can lead to fetal

dehydration.

Endovascular procedures abolish the need

for craniotomy. Fetal shielding during the

procedure is necessary

Special situations - Neurosurgery

Postoperative care:

Pregnancy is a hyper-coagulable state

& the risk of thromboembolic is further

increased by postoperative venous

stasis.

Early mobilization

Maintaining adequate hydration

Pneumatic stocking gloves

Pharmacological prophylaxis

Post op analgesia:

Adequate analgesia is important as pain will cause increased circulating catecholamines which impair uteroplacental perfusion.

Analgesia may mask the signs of early preterm labour.

Paracetamol & Diclofenac is pregnancy risk category B.

Ibuprofen, Morphine, Tramadol is pregnancy risk category C.

NSAIDS can cause early closure of ductus arteriosus in 3rd trimester.

OutcomeCohen, Kerem et all, American Journal of Surgery in 2005

conducted a literature review of 54 studies in England over

last 10 years

Statistics

Total patients reviewed – 12,452

Maternal deaths – 0.006%

Miscarriage – 5.8%

Elective termination of pregnancy – 1.3%

Preterm labor induced by surgery – 3.5%

Foetal loss – 2.5%

Prematurity – 8.2%

Major birth defects (1st trimester surgeries) – 3.9%

R. Cohen-Kerem et al. / The American Journal of Surgery 190

(2005) 467–473

OutcomeConclusions: - Using modern surgical and anesthetic techniques, the risk of

maternal death appears to be very low.

Surgery and general anesthesia do not appear to be major risk factors for spontaneous abortion.

The rate of elective termination appears to be in the rangeof the general population.

Non-obstetric surgical procedures do not increase the risk for major birth defects. Hence, urgent surgical procedures should be performed when needed.

Acute appendicitis, especially when accompanied by peritonitis, appears to be genuine risk for surgery induced labor or fetal loss.

R. Cohen-Kerem et al. / The American Journal of Surgery 190

(2005) 467–473

Conclusion:

Remembering the physiological & anatomical changes of

pregnancy.

Prevention of foetal asphyxia by maintaining maternal oxygenation, ventilation& haemodynamic stability.

Remembering postoperative thromboprophylaxis.

“ A baby is something you carry inside you for nine months, in your

arms for three years and in your heart till the day you die…”

-- Mary Mason