ANEMIA IN PREGNANCY AND ITS ANAESTHETIC IMPLICATIONS www.anaesthesia.co.in email: email@example.com
Anemia Definition:Quantitative or qualitative reduction of Hb or circulating RBC’s or both. As per WHO, Hb conc. Of <11 gm/dl or Hct < 0.33 in 1st & 3rd trimester. In developing countries, limit brought down to 10 gm/dl. Incidence = 40 to 60 %
AGE Newborn 1 month 3 month 12 months Adult male Adult female Hb/Hct 16/55 12/38 10/30 12/38 14/45 12/36 Normal Level Of Hb/Hct Levels vary with age and gender
WHO definition for Chronic Anemia AGEHb gm% 6/12 - 6 yrs <10 6 - 14 yrs <12 Adult male <13 Non pregnant female <12 Pregnant female <11/ Hct <33 1st trimester <11 2nd trimester <10.5
Severity of Anemia ICMR CATEGORIES Category Severity Hb levels gm % 1 Mild 10 – 10.9 2 Moderate 7 – 10.0 3 Severe <7.0 4 Very severe <4.0
Physiological anemia of pregnancy Blood volume ↑45% Plasma vol ↑55% RBC vol ↑30% HCt ↓30% Hb ↓10.5-11
Physiological anemia of pregnancy ↑ in RBC mass ↑ demand for iron ↓in total body iron stores ↓in serum ferritin levels (28-32 weeks of pregnancy)
Criteria for Physiological anemia • Hb =10 gm% • RBC = 3.2 million/mm3 • PCV = 30% • Peripheral smear showing normal morphology of RBC with central pallor.
Regulation of Iron Transfer to fetus Maternal circulation ↓ Serum transferrin carries Fe Transferrin receptors located on apical surface of placental synctiotrophoblast ↓ Holotransferrin is endocytosed ↓ Fe is released & apotransferrin ↓ Free Fe binds to ferritin in placental cells ↓ Transferred to apotransferrin which enters from foetal side of placenta & exits into fetal circulation.
Pathophysiology Oxygen Hemoglobin dissociation curve: O2 released to the tissues is affected by the shape & position of ODC which can move either to right or left. Shift is described in terms of P50 – O2 tension (Po2) at which Hb is 50% saturated with O2, corresponds to 27 mm Hg. .
Normal values of oxygen in arterial and Venous blood Oxygen content:Volume of oxygen carried in 100ml of blood. Arterial O2 content – CaO2 = (1.34 x Hb x SaO2) + (0.003 x PaO2) Venous O2 content – CvO2 = (1.34 x Hb x SvO2) + (0.003 x PvO2) .
Oxygen flux: Amount of oxygen leaving the left ventricle per minute in the arterial blood. CO x arterial O2 sat x Hb conc. X 1.31 Oxygen delivery:Amount of oxygen that reaches the systemic capillaries each min. Do2 = Q x CaO2 x 10 (Q = Cardiac output) Oxygen uptake: Volume of oxygen that leaves the capillary blood and moves into the tissues each min. Measure of oxygen consumption of tissues. Vo2 = Q X (CaO2 – CvO2) X 10
Oxygen extraction ratio: Fraction of oxygen delivered to the capillaries that is taken up into the tissues. Index of efficiency of oxygen. O2ER = VO2 / DO2 Normal range for oxygen transport parameters
Acute Anemia Blood loss > 20% of blood volume Hypovolemia & hemodynamic instability. Signs & symptoms of acute Blood loss
Compensatory mechanism: • Stimulation of adrenergic nervous system & release of vasoactive hormones. • Sympathetic stimulation leading to ↑ CO & HR. • Systemic vasoconstriction, ↑ VR and ↑ SV. • Redistribution of blood volume to vital organs. • Anerobic metabolism, acidosis, hyperventilation. • Renal conservation of water & electrolytes. Factors affecting Compensation: • Cardiopulmonary disease • Left ventricular dysfunction. • Magnitude of loss, oxygen consumption • Anaesthesia
Anaesthetic considerations: Management of patient is judged by magnitude of hemorrhage and adequacy of volume replacement. • Thiopentone - suitable induction agent for normovolemic patients who sustained acute blood loss. • Ketamine or Etomidate - hypovolemic patients. • Decrease conc. of volatile anaesthetic or infusion rate of agents administered i/v. • Regional anaesthesia – not a good option. • Small doses of midazolam can be given.
Anaesthetic management: • Secure2 large bore cannulas. • Monitor SpO2,ETCO2,NIBP,temp,UO,CVP,ECG. • GA with RSI. • Fluid resuscitation, oxygen by mask, aspiration prophylaxis. • Send blood for CBC, cross matching, coagulation profile • Arrange adequate blood. • Ensure left uterine placement. • Transfuse blood if Hb < 7gm % with ongoing blood loss. • If coagulation disorder present, give FFP@ 15-20 ml/kg. • Prepare for intraop cell salvage if indicated. • Regional not indicated.
Guidelines for Blood Transfusion (By National Institutes of Health Consensus Conference): • Hb > 10gm/dl – transfusion rarely indicated. • Hb < 6gm/dl – transfusion almost always indicated. • Hb 6 to10gm/dl – decision to transfuse is determined by patient’s risk for complications of decreased tissue oxygenation ( pt. with IHD ). • Preoperative autologous donation in selected patients. • Intraoperative blood salvage when appropriate. • Acute normovolemic hemodilution when appropriate.
Chronic Anemia Includes Iron Deficiency Anemia, Thalassemia, sickle cell anemia. Symptoms: No symptom (unless RBC count is very low). • Fatigue, dyspnoea on exertion, palpitation. • Nausea, loss of appetite, constipation, indigestion. • Postural hypotension, vertigo, light headedness. • Angina, heart failure, confusion. • H/O bleeding (DUB, malena, hematuria). Signs: • Vitals - ↑ HR,RR • GPE - Pallor of skin & mucous membranes, JVP ↑, pedal edema, generalised anasarca, glossitis, stomatitis, Koilonychia, mouth soreness. • Resp. system - Tachypnoea - Basal crepts, if LVF.
CVS - Tachycardia, strong peripheral pulses with wide pulse pressure. - Functional cardiac murmur (Ejection murmur). - Evidence of cardiomegaly, CHF. • Abd. - Jaundice, hepatosplenomegaly. • CNS - altered sensorium. - Mental disturbances (B12 def). • Edema (Renal failure). • Lower leg ulcers (Sickle cell Anemia). Compensatory Mechanisms: • ↑ 2,3 DPG shift of O2Hb dissociation curve to right. • ↑ OxygenExtractionratio. • Circulatory adjustments - ↑ CO by increasing SV. - myocardial hypertrophy. • Release of erythropoietin which stimulates erythroid precursors in bone marrowto produce RBC’s.
Respiratory adjustments - ↓ physiological shunting in lungs. - ↓ respiratory reserve. - tachypnoea, hyperventilation. • GIT - reduced splanchnic blood flow. Lab Investigations: • Complete blood count a) RBC count – Hb, Hct. b) RBC indices – MCV,MCH,MCHC, RDW. c) WBC count - Cell differential - Nuclear segmentation of neutrophils.
d) Platelet count e) Cell morphology - Cell size - Hb content - Anisocytosis, Poikilocytosis, Polychromasia • Reticulocyte count • Iron supply studies – S.Iron, TIBC, S.Ferritin, Marrow 4. Marrow examination – aspirate & biopsy
Iron Deficiency Anemia • Most common cause of anemia in pregnancy. • Stored as S.ferritin & Hemosiderin. Adult male Adult female Stores 1000mg 300 – 500mg Losses 1mg/day 2mg/day 3mg/day(Pregnancy) • Daily iron requirement 2.5mg – early pregnancy. 5.5mg – from 20 to 22 wks 6 to 8mg – 32 wks onwards
Basal Iron 280mg Transfer to fetus 200-350mg For placenta 50-150mg Blood loss at delievery 100-250mg Expansion of red cell mass 570mg Iron conserved by Amenorrhea 240-480mg TOTAL REQUIREMENT 800-900mg(4-6mg/d) Causes: • Increased iron demand • Diminished intake of iron • Disturbed metabolism • Pre-pregnancy health status • Excess demand
Haematological parameters: IDANormal values Plasma iron <30 50-150ug/dl S.Ferritin <12 14-150ug/l TIBC >400 300-350ug/dl Transferrin saturation <15% 30-50% MCV <75 75-93fl MCH <25 25-36 pg MCHC <30 30-36g/dl RBC Protoporphyhrin >200 30-50ug/dl
Complications: During Pregnancy - Pre eclampsia (due to malnutrition or hypoproteinemia) - Intercurrent infection (infection impairs erythropoiesis by BM depression) - heart failure (at 30-32wks or preg) - Preterm labour During labour - Uterine inertia - PPH - Cardiac failure - shock
Puerperium - Puerperal sepsis - Subinvolution - Failing lactation - Puerperal venous thrombosis - Pulmonary embolism Effects on baby - Amount of Fe transferred to fetus is uneffected even if mother suffers from IDA. - increased incidence of low birth. - IUD due to severe maternal anoxemia.
Folic acid Deficiency • FA is cofactor in nucleic acid synthesis and has imp. role in cell division. • Stores are limited (6-10mg). • Daily requirement is 300-500mg. • Def. causes Megaloblastic anemia. • High incidence in multigravida, twin pregnancy, hyperemesis gravidarum, alcohol consumption, smoking, malabsorption, antiepileptic drugs. Effects on mother:Incidence of abortion high. Effects on Fetus: Premature birth, Neural tube defects, cleft palate.
Management Prevention: • Avoidance of frequent child birth. • Supplementary Fe therapy (60mg elemental Iron three times a day). • Dietary prescription. • Adequate treatment for any infection. • Early detection of falling Hb level, levels should be estimated at 1st A/N visit, 30th & finally 36th week.
Pregnancy <30wks Pregnancy 30-36wks Pregnancy >36wks IDA FA def. Parenteral Oral FA I/M iron I/V iron IDA FA def. Oral iron Oral FA Intolerance or Non-compliance I/M iron I/V iron Blood transfusion PROTOCOL OF SEVERE ANEMIA IN PREGNANCY
Curative: • ORAL THERAPY - 200mg (60mg elemental iron) X 3 times a day. WHO – 60mg elemental iron + 250ug FA OD/BD. Govt. of India Regimen – 100mg Fe + 500ug FA during 2nd half of pregnancy X 100 days. Drawbacks: - Intolerance - Unpredictable absorption rate. - Non Compliant patient. - Long time for improvement @ 0.3-1gm/100ml/wk.
Response to therapy: - Sense of well being. - Increased appetite. - Increase in Hb. - Reticulocytosis with in 5-10 days. • PARENTERAL THERAPY- Indications: - Failure to iron therapy. - Non compliant patient. - Case seen for the 1st time during last 8-10 wks with severe anemia.
Advantages: - Certainity of admission. - Hb rises @1gm/100ml/wk. I/V Route: Iron Dextran (1ml contains 50mg elemental iron & one ampoule contains 2ml). Total dose infusion – Deficit of iron calculated & total amount required to correct deficit is administered in single setting I/V infusion. Elemental Iron Needed (mg) = (Normal Hb - Patients Hb) X Wt(kg) X 2.21 + 1000
Given @10 drops/min X 30 mins (diluted in normal saline or 5% dextrose). If no reaction, ↑ to 40 drops/min. Side effects: - Anaphylactoid reaction. - Chest pain, rigors, chills, fall in BP, dyspnoea, hemolysis. Treatment: Stop infusion. Give antihistaminics, corticosteroids & epinephrine. I/M Route: Iron Sorbitol Citrate (Jactofer) Iron Dextran (imferon) Oral iron should be suspended at least 24 hrs prior to therapy to avoid reaction.
Drawbacks: - Painful injection (less with jactofer). - Chances of abcess formation & discolouration of skin over injection site.
BLOOD TRANSFUSION - Transfusion triggers: • Task force 1996, 2006 – No uniform transfusion trigger Patient factors Type of surgery Preg Preg Elective Emergency <36wks > 36wks C/S C/S -Hb ≤ 5gm% - Hb ≤ 6gm% - with H/O -Always Without CHF without CHF APH,PPH, arrange -Hb 5-7gm%,if -Hb 6-8gm%,if previous blood. CHF,hypoxia, CHF,hypoxia, LSCS. Infections. Infections. Hb <8gm%,2 units blood should be arranged.
Guidelines for transfusion: • Prefer fresh Packed cells. • Do not repeat tranfusion within 24 hrs. Effects of Transfusion: • ↑ O2 carrying capacity of blood. • Viscosity increases by 33%. • Hb increases by 1gm/unit. • Heart rate decreases by 7%. • Supplies natural constituents of blood. • Improvement with in 3 days. Drawbacks: • Premature labour (blood reaction). • CHF • Transfusion rexn. • Infections: HIV, Hep B etc.
Anaesthetic Considerations: • Etiology & Chronicity of anemia • Pt. overall condition • Pt. ability to compensate for ↓ O2 delievery. • Operative procedure. • Anticipated blood loss. • Minimize factors interfering with O2 delivery - low myocardial contractility, CO (careful with volatile anesthetic agents - left shift of ODC (hyperventilation, hypothermia, alkalosis) • Prevent increase in O2 consumption (reduce postop pain, fever, shivering).
Anaesthetic technique: Regional anaesthesia – Spinal or epidural can be given Preloading fall in hct by 20% (2lt). Exacerbate anemia Heart failure. General anaesthesia – Principle: • Avoid hypoxia. • Maintain cardiovascular stability. • Minimize factors which produce unwanted shift of O2 dissociation curve.
Secure2 large bore cannulas. • Monitor SpO2,ETCO2,NIBP,temp,UO,CVP,ECG. Induction: • Adequate preoxygenation. • I/V agents administered slowly. Maintenance: • Ventilation should be maintained to provide normocapnia. • Possibility of awareness is to be kept in mind as O2 conc. is increased. • Mild tachycardia & wide pulse pressure may be physiological obtunded by anaesthetic agents. • Tissue perfusion judged by blanching ear lobes, nose. • Change posture cautiously ↓ BP & CO.
Postoperative: • Extubate relaxant effect worn off. • Monitor vitals, fluid intake/output & respiratory parameters for 12 – 24 hrs. • Oxygen enriched air given by mask. • Prevent shivering. • Hb should be checked postoperatively & transfusion accordingly.
Management during labour • Adequate oxygenation. • Avoid sympathetic stimulation and hyperventilation; prevent rightward shift of ODC. • Decreased blood loss. • Avoid maternal stress, patient can go into CHF. • Improved uterine blood flow. • PPH should be emergently treated.
Sickle cell Anemia • Valine substituted for glutamic acid at 6th position on ß chain of Hb molecule. • Common variants - SS ( sickle cell anemia). - SA ( sickle cell trait). - SC ( sickle cell disease).
Signs & symtoms of sickle cell disease: • Vaso-occlusive complications a) Painful episodes b) Acute chest syndrome c) Strokes d) Renal insufficieny e) Splenic sequestration f) Proliferative retinopathy g) Priapism h) Spontaneous abortion i) Bone pains, leg ulcers, Osteonecrosis • Complications related to hemolysis a) Anemia (Hct 15 – 30%) b) Cholelithiasis c) Acute aplastic episodes
Infectious complications a) Streptococcus pneumonia sepsis b) E.coli sepsis c) Osteomyelitis Factors favouring Sickling: • Hypoxia • Acidosis • Decrease in body temperature • Dehydration • Circulatory stasis Investigations: • Hb, Hct, Reticulocyte count • Blood film • Hb electrophoresis • Sickle cell test (Na metabisulphite)
Treatment • Acute pain: a)Fluid replacement b)Administer opoids & NSAIDS. • Chronic pain: a)Acetaminophen with codiene b)Fentanyl patches c)NSAIDS
Anaesthetic Management: Goals - • Avoidance of acidosis due to hypoventilation of lungs. • Maintenance of optimal oxygenation. • Prevention of circulatory stasis (improper body positioning, use of tourniquets). • Maintenance of normal body temperature. Preoperative period - a) Admit to hospital 12 – 24 hrs before surgery to permit optimal hydration with I/V fluids. b) Correction of any coexisting infection. c) Transfuse RBC’s if needed ( keep Hb b/w 9-12 gm% & Hct of about 35%, with 60-70% HbA). Intraoperative period - a) Monitor SpO2,ETCO2,NIBP,temp,UO,CVP,ECG
b) Maintain arterial oxygenation c) Hydration. d) Body temperature. e) Replace blood loss when necessary. General anaesthesia: Preoxygenate for 5 mins before induction to make HbS as possible is in oxy form. After airway is established, give 30 – 50% inspired oxygen. Regional anaesthesia: Maintain oxygenation, ventilation, hypotension. Prevent stasis of blood flow.