Normal changes in pregnancy

Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip.

Software statistics PhD (physio)Mahatma Gandhi Medical college and research

institute , puducherry India

Big B confirms that Aish is pregnant

• When the whole world turns an eye on changes of pregnancy why not anesthesiologists ??

Maternal physiology – what to know and why?

• The baby comes in utero

• It has to get accommodated • It has to get nutrients • It has to grow • Hence many changes have to take place

Systems involved

• Cardiovascular • Respiratory • CNS • Head, eyes, ent • GIT • Renal • Haemotolgic • Endocrine • Musculoskeletal

• weight increase 12 kg

Cardiovascular

Cardiovascular

• TBW increases from 6.5L to 8.5L

– starts 5- 6 weeks

• Pregnancy is a condition of chronic volume overload

• Water retention exceeds Na retention-• decreased plasma osmolality

CVS

• Cardiac output starts to increase from 8 weeks • Both HR and SV increase • Labour CO upto 7 – 10 litres • First, it facilitates maternal and fetal

exchanges of respiratory gases, nutrients and metabolites. Second, it reduces the impact of maternal blood loss at delivery.

Haemodynamic changes

• Systolic BP – no change • Diastolic BP – decrease • Heart rate – 20 % increase • Cardiac output – 30 - 40 % increase • Cvp & PCWP -- no change • SVR - 1200 dyne / cm / sec 20 % decrease • PVR – 80 dyne / cm / sec 30 % decrease

CO , SVR and BP

CO X SVR = BP Increase decrease no change

SV ↑ vaso dilation

HR ↑ placenta

Diastolic BP

• In fact due to vasodilation

• Diastolic BP may fall

Haemodynamic changes – ctd.

• Blood volume increased

• More blood

• Vasodilation and more space for it to hold

• So CVP and PCWP --- no change

Distribution of CO

– First trimester and non-pregnant state• Uterus receives 2-3%

– By term• Uterus receives 17%• Breasts 2%

– Reduction of the fraction of CO going to the splanchnic bed and skeletal muscle

– CO to the kidneys, skin, brain and coronary arteries does not change

In patients with heart disease

• For the gravida with heart disease and low cardiac reserve, the increase in the work of the heart may cause ventricular failure and pulmonary oedema

• Effective pain relief in such patient (epidural)

CO increase __ ??

• Epidural analgesia – • Cardiac output ?? – Lower when supine • IVC compression by the uterus reduces venous return

to the heart

• Postpartum ?? • Hemodynamic changes return after 2 – 4

weeks after delivery.

Wedge and supine hypotension

• Auscultation

– increased splitting of the first and second heart sound

– S3 gallop– SEM along the left sternal border – Continuous murmurs

Investigations

• CXR– straightening of left heart border– heart position more horizontal – may appear as

cardiomegaly– increased vascular markings in lungs

• ECG – left axis deviation– non-specific ST-T wave changes

Echo

• left ventricular hypertrophy

• 94% of term pregnant women exhibit tricuspid and pulmonic regurgitation, and 27% exhibit mitral regurgitation

Respiratory system• UPPER RESPIRATORY TRACT

–Hyperemic mucosa of nasopharynx • Estrogen-mediated• nasal stuffiness and epistaxis

–Polyposis of nose and sinuses may occur and regress after delivery– “chronic cold”

Airway

• Airway edema and difficult intubation • Weight gain and large breasts may hamper mask ventilation • Size of ET tube ?? • Bleeding

• Mallampatti classification in pregnancy • Class 4 42 % ---- 56 % • Class 3 36 % ----- 29 % • Class 2 14 % ----- 10 % • Class 1 8% ----- 5 %

Thoracic cage becomes rounder and more AP diameter

Changes of rib cage and expanding uterus

• TLC ↓ 5 % • FRC ↓ 20 • VC – no change • TV - ↑• Decrease FRC – less oxygen reserve • oxygen consumption increases by 30% to 40%

during pregnancy • Desaturate at 150 mm Hg / min

PFT

Respiratory muscles

• No change in strength • By 8 weeks progesterone increase – • central drive increase • TV increase • MV increase • RR same

ABG

• Increased MV • wash out CO2 • Increase PO2

• PaO2 – 105 and PCO2 to 30 mmHg• But pH is normal • Kidneys excrete bicarb ---25 – 20 mEq/l

• The increased minute ventilation combined with decreased functional residual capacity hastens inhalation induction or changes in depth of anaesthesia when breathing spontaneously

Central nervous system

• Neuro changes are subtle • Elevated pain threshold • Tolerate pain better How ?• Increased spinal dynorphin • Upregulation of descending inhibition• Why ? • Withstand labour pain better

Local anaesthetics

• Local anaesthetics • Decreased dose • There is a 30% reduction in volume of local

anaesthetic solution required at term when compared to the non-pregnant woman, to achieve the same block.

• CSF protein ↓• CSF pH ↑

MAC and pregnancy

• There is a reduction in anaesthetic requirements, with a fall in the minimum alveolar concentrations (MAC) of halogenated vapors.

• MAC 25-40% lower in gravid as compared with nonpregnant.

GI tract - Appetite

• Increased apetite

• Pica

• Sense of taste may be blunted

Gastrointestinal - Gallbladder Slower rate of emptying increased risk gallstone formation

• NAUSEA AND VOMITING– Morning sickness complicates 70% of pregnancies– Onset 4-8 weeks up to 14-16 weeks– Cause? • Relaxation of smooth muscle of stomach,

elevated levels of steroids and hCG

Scoline

• Serum cholinesterase levels fall by 24-28% during the first trimester

• However, even lower levels (about 33% reduction) develop during the first 7 postpartum days.

• Usually suxa ok in normal pregnant persons

NONDEPOLARIZING MUSCLE RELAXANTS

• Increased sensitivity to vecuronium and rocuronium

• Elimination half-life of vecuronium and

pancuronium shortened

• Atracurium pharmacodynamics and pharmacokinetics unaltered

No alcohol item but still hangover

GIT

• GE sphincter tone down • Gastric emptying time ? Altered

• Volume and acidity – no change • Consider as full stomach !! • Liver blood flow unchanged • Portal compression – varices and • Perianal haemorhoids – more common

Renal ANATOMY

– Kidney enlargement

• increased renal vascular and interstitial volume, R>L

– Ureteral and renal pelvis dilatation by 8 weeks

–mechanical compression by uterus and ovarian

venous plexus

– smooth muscle relaxation by progesterone

• Increased incidence of pyelonephritis

• Possible glycosuria

Effective renal plasma flow (ERPF) and GFR increase

»Pregnant nonpregnant• Urea - 2 – 2.5 mmol/l 6-7 • Creatinine 50 mic.mol/l (0.6) 100• Uric acid 0.2 0.35

• So in intrepretation of lab. Values – beware

Renal

• Greater ADH production • Increased vasopressinase enzyme • Increased renal tubular resorption and sodium

retention • Sodium excretion normal

Haematological

• Anemia of pregnancy blood volume increases by up to 45%

Red cell volume increases by only 30%.

This differential increase leads to the “physiologic anemia” of pregnancy

• Hematopoiesis outstrips iron supply • Iron supplements necessary

–physiologic anemia of pregnancy • may function to decrease blood viscosity• may improve intervillous perfusion?

Blood cells

• Dilution of plasma causes reduction of antibody titres

• Reduction of leucocyte chemotaxis • Autoimmune diseases better in pregnancy !!• WBC count is normal but may raise in labour

Coagulation

• Platelets immature • Chronic low grade DIC ---consumptive

coagulopathy – immature platelets • All coagulation factors are increased - ↑

estrogen and progestogen • Thrombo embolic complications 5 times more

common but BT and CT are normal • ESR and CRP elevated

Endocrine

• Pregnancy is a diabetogenic state • Insulin resistance and higher ABG levels • Pregnant – more prone for ketosis in fasting

state • The normal pregnant woman is euthyroid • Free T 4 is the best test

Endocrine • Plasma corticosteroid-binding globulin (CBG) rises– due to enhanced liver synthesis

• Free plasma cortisol rises – increased production and delayed clearance

• DHEAS (dehydroepiandrosterone) decreases

• Testosterone is slightly elevated – Increased SHBG and androstenedione

SKIN

• Spider angiomata (face, upper chest, and arm) and palmar erythema–elevated estrogen levels –both regress after delivery

• Striae gravidarum• Hyperpigmentation • Melasma: “mask of pregnancy”• Increased eccrine sweating and sebum

excretion

• Increased thickness of cornea due to fluid retention (contact lens intolerance)

• Decreased intraocular pressure

• Eye changes are not like this!!

Skeleton

• Lordosis – keep center of gravity over the legs– back pain…

• Relaxin – relaxation of the pubic symphysis and sacroiliac

joints• facilitates vaginal delivery but may lead to discomfort

• Implications– unsteadiness of gait and trauma from falls

Placenta

• keeping maternal blood levels of drugs low • Less drug reaches the fetus.• since 75% of the blood in the umbilical vein

travels to the liver, a large portion of drug can be metabolized before reaching vital fetal organs

• What happens in fetal distress ??

2 factors against this safety

• (1) fetal acidosis during times of distress causes increased perfusion of the heart and brain

• (2) Fetal pH is lower than maternal pH and results in basic drugs (such as local anesthestics) becoming more ionized when they reach fetal circulation. This effectively traps them on the fetal side of the circulation

Lordosis

Difficult regionalAltered back OedemaDifficult positioning No premedication.Labour painEpi presssures :-1 cm but in labour it may go to +5 cm-Loss of res.?

To summarize

• Prone for hypoxemia.• Inh, induction faster• CVS ,clotting , renal changes • Difficult airway.• MAC decreased. pain decrease • Full stomach• Epidural difficult.• Wedge • Dose of LA decreased

When what changes ??

• Physical changes – 24- 28 weeks

• Physiological changes 6-8 weeks

Carry home message

don’t worry be happy

Thank you all