2. CONTENT
• Introduction
• Definition
• Classification of anaemia in pregnancy
• Haemoglobin structure
• ODC
• Pathophysiology of anaemia
• Adaptive mechanisms that ensure oxygen delivery to tissues
• Anaesthesia management
3. CONTENT…
• Choice of Anaesthesia
Regional Anaesthesia
General anaesthesia
• Post operative management
• Sickle cell anaemia
• Thalassemia
• Conclusion
4. INTRODUCTION
• Anaemia is an independent modifiable perioperative risk factor
• Pregnant women are particularly considered to be the most vulnerable group
• Approximately 38% of all pregnant women worldwide are found to be anaemic,
• Global prevalence of iron deficiency anaemia (IDA) in pregnancy ranges from 15%
to 18%.
5. INTRODUCTION
• WHO- 65-75% prevalence of anemia in pregnant women in india
• Nearly half of the maternal death is due to anemia in southasian countries
• 80% of these is contributed by india
6. DEFINITION
• Anaemia is defined as a qualitative or quantitative deficiency of haemoglobin or
red blood cells in circulation, resulting in reduced oxygen (O2 )-carrying capacity
of the blood to tissues and organs.
7. DEFINITION OF ANAEMIA IN PREGNANCY
• Hb less than 11 mg/dl Or hct <0.33 inT1&3
• second trimester fall of 0.5mg/dl (dilutional)<10.5
• Qualitative/quantitative deficiency of the Hb or RBC
• Leading to Decrease in O2 carrying capacity
• Developing countries lower limit 10gm/dl
11. HAEMOGLOBIN STRUCTURE…
Early embriogenesis
• Theta and zeta chain instead of alpha
chain
• Ebsilon instead of beta chain
After early embriogenesis
• 2alpha+ 2beta -HgbA1
• 2apha +2 gama -HgbF
• 2 alpha +2 delta HgbA2
By term
• HbA1:HbF =1:1
• At 1 yr HbF < 1 %
12. HAEMOGLOBIN STRUCTURE…
• Primary structure: sequence of amino acid 141 AA , alpha,146 AA beta
• Secondary structure 3 dimensinal shape of the amino acid side chain defined as
secondary structure
• Tertiary structure-four chain and heme prosthetic group relation defined as teritiary
structure
• Quarternary structure -binding of ligand 2,3DPG ,O2 with tertiary structure
14. Double bohr effect
• At materno fetal interface maternal blood taken up co2 and become more acidic-
decrease o2 affinity to HB Leads to o2 delivery( 1st effect)
• Fetal blood releases co2,more alkalotic - cause o2 affinity , fetal o2 uptake –second
effect
Double Haldane effect
• HbF Oxygenated –release co2
• HbA deoxygenated –binds more co2
Help in adequate feto maternal gas exchange
ODC…
16. CARDIOVASCULAR CHANGE IN PREGNANCY
SVR Decreases Vascular compliance
Plasma volume Increases 50% Peak by 36wk
Blood cell volume Increases 20% Fall in haemetocrit
Relative physiological anaemia
Decreased vascular tone allow adequate blood flow
17. Natriuresis
Placental
progesteron
HORMONAL CHANGES IN PREGNANCY
RAAS Stimulation
Increase aldosterone
Na,h2o reabsorption
Increase blood volume
30-40%
Plasma osmolarity
decrease by 10%
Na low normal level
and potassium
constant
oestrogen
Stimulate
angiotensinoge
n
Fluid retention
18. HAEMATOLOGICAL CHANGES IN PREGNANCY
• RBC increase but not as much as blood volume
Relative anemia
15% decrease in Hb pre pregnancy level(Average Hb 11.6,hct 35.5%)
• Decreased blood viscosity – compensatory mechanism
• Become pathological when Hb fall further(<10)
19. PATHOPHYSIOLOGY OF ANAEMIA
Anaemia due to acute blood loss-
• sympathetic activation
• Vaso constriction
• Increase venous return
• Increase stroke volume
• Increase cardiac output
• Increase velocity of blood flow
• Constriction of capillary in skin and splanchnic circulatiom-redistribution of blood
20. PATHOPHYSIOLOGY OF ANAEMIA…
Chronic anaemia
• Increase in cardiac output-maintain adequate oxygen delivery
• Maintain a constant arterial-venous O2 content difference and increase in O2
extraction ratio.
• Increased 2,3-diphosphoglycerate (2,3-DPG)-rightward shift in ODC
• The relative reduction in oxygen content is detected by tissue chemoreceptors,
leading to further compensation and an increase in minute ventilation
21. PATHOPHYSIOLOGY OF ANAEMIA…
Normal
• Oxygen carried in blood =oxygen binded with
Hb+dissolved O2
• Cao2=Hb x 1.37 x SaO2+0.0034xPao2
• Cao2 (on air) =15 x 1.37x 100+0.0034 x 100=21.1
ml/dl
• Delivery of o2= CO X CaO2=5l/mnt x 21.1=1055
ml/mnt
• Oxygen consumption=CO x(Cao2-Cv02)=250-270
ml/min
• O2 extraction= 250/1000 = 25%
• Anaemia
• Hb drops,Cao2 decrease
• Hence increases CO to increase
o2 delivery
• Oxygen consumption increases
• excessive strain on
myocardium-acute cardiac
failure-increase in CO should
be less than 10
22.
23. • Mild anemia -asymptomatic
• Moderate to severe anemia-Dyspnoea, palpitations, angina and signs of high
CO, such as tachycardia, wide pulse pressure and systolic ejection murmur
• Severe anemia-Long-standing hyperdynamic circulation increases the cardiac
load, causing hypoxia, ventricular dysfunction,heart failure
24. ADAPTIVE MECHANISMS THAT ENSURE OXYGEN
DELIVERY TO TISSUES
Oxygen sensors
• kidneys,aortic and carotid body chemoreceptors and cells [hypoxia-inducible factor (HIF)].
• Adaptive physiological responses occur to compensate for anaemia-induced tissue hypoxia,
which supports cellular survival during anaemia.
The Respiratory adaptations during anaemia
• Increase in minute ventilation due to stimulation of respiration.
NO-mediated mechanisms
• The partial pressure of O2 in arterial blood (PaO2 ) and Hb O2 saturation (SaO2 ) are increased
• Help in ventilation-perfusion matching. This help for maintaining SaO2 in the presence of
reduced Hb
25. ADAPTIVE MECHANISMS THAT ENSURE OXYGEN
DELIVERY TO TISSUES…
Cardiovascular adaptations
• Increase in CO
• Reduction in systemic vascular resistance (SVR) hypoxia-sensing cells activate the
sympathetic nervous system
• Reduction in blood viscosity,
• Systemic vasodilation
• Increased venous return
26. ADAPTIVE MECHANISMS THAT ENSURE OXYGEN
DELIVERY TO TISSUES…
An increase in systemic O2 extraction
• Three mechanisms helping for oxygen diffusion from microcirculation to tissues and thus sustain
mitochondrial oxidative phosphorylation (aerobic respiration):
a) Right shift of the oxygen dissociation curve
b) Increased tissue blood flow -helping to increase oxygen diffusion from microcirculation
to the tissues
(c) increased capillary recruitment and density -Decrease the diffusion distance to the cells
during anaemia.
• These adaptation help in ATP generation under aerobic conditions and function as a primary oxygen
sensor
27. ADAPTIVE MECHANISMS THAT ENSURE OXYGEN
DELIVERY TO TISSUES…
HIF(hypoxia inducible factor) mediated metabolic cellular adaptations
• Help in balance between systemic oxygen delivery and consumption,survival
during acute anaemia.
• HIF has been described as a master regulator of hypoxia sensing and hypoxic cell
signalling
28. FETOPLACENTAL UNIT AND OXYGEN DELIVERY
• Pregnancy Require Increase in oxygenation-towards the end of 1st trimester
• Foetal haemoglobin (α2, γ2)- lower affinity for 2,3-diphosphoglycerate ->ODC shift to left
• For any given arterial oxygen pressure (PaO2 ) greater arterial oxygen saturation (SaO2 ) in foetal
blood
• placenta acts as a pathway for oxygen transport to foetal circulation and provides oxygen to
support its own metabolism
• chronic hypoxia following anaemia in pregnancy can lead to intrauterine growth restriction
• To compensate- there is a dramatic increase in placental vascularity along with increase in
placental villous surface
Increasing the maternal cardiac output-Uterine vessels receive an enhanced blood supply
31. DIAGNOSIS
• All pregnant women should screened for anaemia -@ 1st antenatal visit,28 week
• CBC-Hb,MCV,MCHC
• Peripheral smear-microcytic ,hypochromic
• Serum ferritin <30ng/mL
32.
33. PREVENTION
• WHO –daily dose of 30-60 mg iron supplementation(time of detection to
throughout the pregnancy)
• 400 mic/day folic acid prophylactic dose
34. TREATMENT
• Mild to moderate anemia-oral ferrus iron 80-100 mg/day
• Intravenous iron –those with intolerance to oral iron,lack of response to oral
iron,severe anaemia,advanced GA
• Blood transfusion
Based on clinical and investigations
Rare if hb>8 predelivery/may need peripartum
If critical anemia Hb<6g/dl,mind risk of cardiac failure-Leucodepleted RBC given
carefully
35. ANESTHETIC CONSIDERATION
• minimize factors interfering with o2 delivery
• Prevent any increase in o2 consumption,
• optimize partial pressure of o2 in arterial blood
• maintenance of stable hemodynamics
• avoidance of hypothermia and hyperventilation.
Anaemic patients with a Hb concentration<7.5 gm/dlhave a 50% decrease in O2 carrying capacity, -->further
decrease due to surgical stress and pain-causes tachycardia and increases the oxygen demand.
Hypotension, hypoxia, hypercarbia, respiratory depression and hypoglycaemia further increase the O2 demand.
36. ANAESTHESIA MANAGEMENT
• Minimizing the factors that further decrease O2 delivery or increase O2
consumption
• Avoid hypoxia,hyperventilation,tachycardia,,hypotension,shivering
• Balanced physiology to aid coagulation, prevent
acidosis,hypocalcemia,hypothermia
• Supplimental O2 while giving spinal
• Minimize intra op bleeding-meticulous surgical
technique,uterotonics,antyfibrinolytics
• Major blood loss-blood transfusion,blood product guided by point of care
coagulation tests
37. PRE-ANAESTHETIC EVALUATION
History and examination
• History chronic poor tissue perfusion –
tiredness,fatigue,breathlessness,palpitation,chest pain( planning the technique of anaesthesia)
• H/O increased or acute blood loss from GIT, female genital tract
• history of chronic diseases
• History of prior transfusion, drug/alcohol intake
• nutritional habits and history of anaemia
• worm infestation
• signs of high CO-tachycardia,wide pulse pressure,ESM
38. INVESTIGATIONS
• CBC,reticulocyte countsmear,blood grouping
• Stool,urine analysis,ESR,blood urea nitrogen level,s.creatine,bilirubin
levels,s.proteins
• Serum iron,TIBC,B12 &Folate level
• Hb electrophoresis and ecg for any evidence of myocardial ischemia
• ECHO
39. MINIMAL ACCEPTABLE LEVEL OF HB AND NEED OF PRE-
OPERATIVE TRANSFUSION
• Does not exist-based on patients need,risk of developing complications of
inadequate oxygenation
• Rarely indicated if hb>10
• Almost always indicated when hb<6
• Hb -7-8 in labour or post partum-according to symptom and associated co
existing medical condition,blood loss,threat of bleeding
40. OBSTETRIC MANAGEMENT
• Normal vaginal delivery should be considered if there is no history of previous caesarean
section/obstetric indication for caesarean delivery.
• Labour epidural analgesia is beneficial in the first stage of labour along with supplemental
oxygen.
• Steroids, antibiotics and digitalization should be considered if signs of pulmonary oedema exist.
• The second stage of labour should be curtailed by assisted vaginal delivery, and active
management of third stage with uterotonics and tranexamic acid should be considered to
prevent PPH.
• Caesarean section performed for obstetric indications
• Anaemia per se is also associated with increased risk of caesarean section
41. MONITORING
• To assess the adequacy of perfusion and oxygenation-
ECG, NIBP, EtCO2, temperature monitoring, pulse oximetry and
urineoutput.
• If major blood losses are anticipated- as in placenta previa or acccreta
1-Serial Hb, haematocrit -monitor ongoing blood losses
2- Invasive monitoring (e.g. CVP)
3-Invasive arterial blood pressure monitoring
4-ABG analysis and measurement of mixed venous PvO2
42. CHOICE OF ANAESTHESIA
• The main concern while choosing anaesthetic technique is to avoid hypoxia,
maintain cardiac output and prevent a left shift of ODC.
• Both regional and general anaesthesia can be administered for caesarean
sections as both the techniques have their relative advantages and disadvantages;
• selection depends upon the patient’s physical status and the circumstances at
the time of surgery.
43. CHOICE OF ANAESTHESIA
GA/REGIONAL
Depends on
• severity and types of anemia
• Extent of physiological compensation
• Concomitant medical condition
• Type and nature of procedure
• Anticipated blood loss
44. REGIONAL ANAESTHESIA
• Regional anaesthesia or central neuraxial block
1- low-dose spinal anaesthesia along with adjuvants
2-Epidural anaesthesia with intermittent/continuous catheter dosing
3- combined spinal-epidural anaesthesia (CSE)-Dense blockade and allows
titratability of drug with stable hemodynamic along with post-operative
analgesia.
• Supplemental oxygen by face mask or nasal cannula to avoid hypoxia
• left uterine displacement to prevent supine hypotension,
• Restricted fluid infusions to maintain euvolemia and avoid fluid overload should be
ensured.
• Mild anxiolytics may be desirable but over-sedation should be avoided
45. REGIONAL ANAESTHESIA …
Advantages of regional anaesthesia
• provides good analgesia
• Ability to provide supplemental O2 ,
• Decreased blood loss with stable hemodynamics,
• Psychological benefit for the mother as she is aware of her childbirth.
Disadvantage of central neuraxial blockade
• Sudden hypotension due to sympathetic blockade extending above T4- impairment of tissue oxygenation
• RA avoid in parturients with overt Vitamin B12 deficiencies with neurological symptoms- worsening of
symptoms of subacute degeneration of spinal cord
46. REGIONAL ANAESTHESIA …
• Extra precautions should be taken to avoid hypotension, hemodilution and
subsequent heart failure or pulmonary oedema
• which may occur on the return of vascular tone once the effect of spinal
anaesthesia wears off
47. GENERAL ANAESTHESIA
• In severely anaemic or moderately anaemic patients with cardiac decompensation.
Advantages of general anaesthesia
• rapid induction,
• better cardiovascular stability
• control of airway and ventilation,
• and less hemodynamic changes,
• allaying anxiety and preventing associated cardiovascular changes.
Disadvantages of general anaesthesia
• chances of aspiration,
• hypoxemia during induction,
• failed intubation
• awareness to the mother and adverse neonatal effects.
48. GENERAL ANAESTHESIA….
• Intra- and post-operative optimization of cardiac output and oxygenation helps
to improve the patient’s tolerance for anaemia
• Can be achieved by reducing the oxygen demand, supplementing oxygen and
early use of vasopressors to maintain adequate perfusion and tissue oxygen
delivery.
• Prevent pain and infection to reduce oxygen requirement.
49. GENERAL ANAESTHESIA….
• Measures taken to prevent hypoxia
• pre-oxygenation with 100% O2 and supplementing oxygen in the peri-operative period.
• Measures and expertise to secure a definitive airway should be available
• Adequate FiO2 , monitoring of ABG and ventilatory parameters, will prevent any undesirable
decrease in O2 flux.
• Intravenous anaesthetic agents should be slowly titrated to prevent any precipitous fall in CO,
• Carefully positioned to minimize position associated volume shifts.
• High concentration of volatile agents depresses both the myocardium as well as ventilation
and may lead to hemodynamic instability.
• Uterotonics and antifibrinolytics such as tranexamic acid should be administered to manage
blood loss
• Transfusion practices for blood and blood products should be guided by laboratory testing and
point-of-care viscoelastic assays,
•
50. GENERAL ANAESTHESIA….
• Anticipate and treat any adverse events,
• fever, shivering and acute massive blood loss,
• Mild tachycardia and wide pulse pressure may be physiological and should not be
confused with light anaesthesia.
• Temperature monitoring and measures to prevent hypothermia to maintain
normal core body temperatures
• Fluid warmers
51. AVOIDANCE OF HYPOXIA
• preoxygenation
• O2 supplement peri and post operative period
• Maintanance of airway-to prevent fall in fio2 due to airway obstruction/difficult
intubation
• Measures and expertise to secure definitive airway shouldbe available
immediately
• Spontaneous ventilation-only for short procedure/high fio2 40-50%/high conc
volatile agent depress myocardium,ventilation
53. MINIMIZE DRUG INDUCED DECREASE IN CO
• IV agents slowly titrated –prevent precipitous fall in CO
• Careful positioning-minimize position associated volume shift
• Mild tachycardia,wide pulse pressure may be physiological –not be confused with
light anaesthesia
54. FACTORS LEADING TO LEFT SHIFT OF ODC SHOULD
BE AVOIDED
• Avoid hyperventilation/respiratory alkalosis-Hypocapnia decreases CO-Maintain
normocapnia.
• Hypothermia should be avoided –
i. Take all measures to ensure normal core body temperatures
ii. IV fluids and blood products if any should be warmed
55. POST-OPERATIVE MANAGEMENT
Anaemia may be further aggravated
• peri-operative blood loss
• poor nutritional intake post-operatively
• frequent blood sampling for laboratory investigations
• Rise in hepcidin levels due to inflammatory response to surgeryinhibition of
intestinal Fe absorption and reduce the Fe release from stores
56. POST-OPERATIVE MANAGEMENT…
• Supplementation of oxygen to keep the available haemoglobin saturated.
• Repeat assessment of Hb and correction should be done with blood transfusion if
necessary.
• Transfused RBC contains heme Fe (200–250 mg per unit) with a small amount of
labile iron that is immediately available for erythropoiesis depending on the storage
time of RBC.
• Close monitoring of vital parameters -detect decompensation and early intervention.
• Good postoperative analgesia for preventing tachycardia and further load on the CVS.
• Ensure euvolemia, normothermia and normalizing the acid-base status.
57. POST-OPERATIVE MANAGEMENT…
• Fe deficiency anemia- mild to moderate postpartum anaemia (PPA),
asymptomatic or mildly symptomatic should be managed with oral Fe for 3
months.
• parenteral Fe -if response with oral therapy is not adequate
• Early ambulation and physical therapy to prevent venous thromboembolism
should be ensured in the postpartum period
58. SICKLE CELL ANEMIA
• sickle cell disease-trait/disease
• Hbs -valine instead of glutamic acid in 6th position of beta chain
• when deoxygenated hb aggregate -crisis
• hypoxia pao2<50mmhg,acidosis,dehydration,stress,infection,hypothermia
• chronic changes in cardiovascular system/dysfunction risk of preterm labour
• transfusion only if severe anemia,hypoxemia,preeclampsia,septicemia,renal
failure,acute chest pain syndrome,anticipated surgery,aplastic crisis
• AIM for Hb >8g/dl,HbA>40%
59. SICKLE CELL ANEMIA
• Anaesthetic management- avoidance of hypoxemia, hypovolemia, hypothermia and acidosis along
with provision of good analgesia.
• Both neuraxial and general anaesthesia are acceptable
• effective pain management -opioid based neuraxial
• avoid pain crisis
• avoid dehydration
• avoid hypoxemia and acidosis
• avoid hypothermia
• avoid NSAIDS
• avoid transfusion due to antibodies
• avoid risk of infection-antibiotics
• cell salvage is contraindicated
60. THALASSAEMIA
• microcytic, haemolytic anaemias-reduced synthesis of one or more of the
polypeptide globin chains
• Advances in the management of β-thalassaemia major by extensive blood
transfusions and chelation therapy have prolonged life expectancy
• Higher transfusion requirements in pregnancy worsen haemosiderosis and
cardiac failure.
61. THALASSEMIA-ANESTHETIC CONSIDERATIONS
• Due to chronic anaemia with resultant tissue hypoxia
• multiple transfusions leading to increased iron load especially in the myocardial
cells
• concomitant difficult airway.
Cesarean delivery
• General anaesthesia/central neuraxial anaesthesia
• platelet count ,excluding history of spontaneous haemorrhage
62. COVID-19 INFECTION AND IDA DURING
PREGNANCY
• Pregnancy exacerbates the acute inflammation typical to COVID-19, increasing
the risk of developing a cytokine storm.
• There exists a pathophysiological link between anaemia and severe COVID-19
during pregnancy, which can lead to a poor maternal and neonatal outcome.
63. COVID-19 INFECTION AND IDA DURING
PREGNANCY…
• Serum levels of ferritin elevated in acute inflammatory conditions
• critical role in the development of the cytokine storm.
• Iron metabolism plays an important role in supporting the immune system to
fight against invading microorganisms.
• viral replication requires adequate iron levels within the host cells
• The immune system reacts by decreasing the bioavailability of iron during the
acute phase.
64. COVID-19 INFECTION AND IDA DURING
PREGNANCY…
• fall in serum iron concentrations and an increase in serum ferritin.
• This leads to decrease in availability of iron for erythropoiesis and thus aggravates
iron deficiency anaemia.
• The low Hb levels further disrupt the transport of O2 , causing hypoxia and eventually
resulting in multiorgan dysfunction syndrome in pregnant COVID-19 patients
• SARS-CoV-2 can interact with haemoglobin molecules on the erythrocyte cause the
virus to attack the heme on the beta chain of haemoglobin and cause haemolysis
• Patients with anaemia should hence be advised to take extra precautions to minimize
the risk of exposure to the virus
65. CONCLUSIONS
• The anaesthetic implications of anaemia in pregnancy are based on the understanding of the
normal and compensatory mechanisms that optimize tissue oxygenation and iron homeostasis.
• The main aim is to maintain a fine balance between the compensatory mechanisms and
adequate tissue oxygenation in these parturients.
• Both regional and general anaesthesia can be used judiciously.
• Monitoring should aim at assessing the adequacy of perfusion and oxygenation and the
magnitude of ongoing losses
• Deleterious effects of chronic tissue hypoxemia along with threat of major blood losses in the
perioperative period need to be anticipated and treated adequately.
66. REFERENCE
• Roberta H Hines et al.Stolting’s anaesthesia and co-existing disease 3rd
edition.copyright 2018,Elsevier
• David H Chestnut,MD et al.Chestnut’s obstetrics anesthesia principles and practice
6th edition.copyright 2020,Elsevier
• Grewal A. Anemia and pregnancy: Anesthetic implications. Indian J Anaesth
2010;54:380-6
• Sunanda Gupta et al.Pathophysiologic and Anaesthetic Considerations in Iron
Deficiency Anaemia and Pregnancy; An Update Journal of Obstetric Anaesthesia
and Critical Care | Volume 11 | Issue 2 | July-December 2021;59-69
