blood conservation methods in anaesthesia and surgery
DESCRIPTION
Pre-operative, intra-operative and post-operative methods of conserving blood to reduce risk of allogeneic blood transfusionTRANSCRIPT
BLOOD CONSERVATION IN ANAESTHESIA AND
SURGERY
AGYA BOAKYE ATONSAH PREMPEH
OUTLINE
INTRODUCTION
BRIEF HISTORY OF BLOODLESS MEDICINE AND SURGERY
BLOOD CONSERVATION METHODS
FUTURE OF BLOODLESS MEDICINE AND SURGERY
INTRODUCTION
Bloodless Medicine and Surgery(BMS) is relatively new
Medicine has searched for alternatives to allogeneic blood
The term (BMS) is defined as the avoidance of allogeneic blood
The practice of BMS entails more
Balance - Benefits and risks Homologous blood transfusion
Knowledge of broad spectrum of techniques and methods Employment of those techniques and methods(condition&harm)
BRIEF HISTORY OF BLOODLESS MEDICINE AND SURGERY
During the second world war in the 1940s – Wounded soldiers
This subsequently led to an increased demand for blood donors
The practice of blood transfusion was regarded as an accepted therapeutic method by most
Not accepted by members of the religious organisation The Watch Tower Bible and Tract Society (Jehovah’s Witness) and same view
Founded in 1884 in Western Pennsylvania as a Bible Study Group
Grown into a worldwide organisation comprising over 7 million adherents in over 200 countries
The Witnesses’ belief is that God views blood as sacred and holy.
They cite some biblical passages to support their claims.
Leviticus 17:10-12, God says to Moses:
As for any man of the house of Israel or some alien resident who is
residing as an alien in their midst who eats any sort of blood, I shall
certainly set my face against the soul that is eating the blood, and I
shall cut him off from among his people.
Genesis 9:1-4, God says to Noah after the flood: Every moving animal that is alive may serve as food for you. As in the case of green vegetation, I do give it all to you. Only the flesh with its soul, its blood, you must not eat.
Bible does not speak of blood transfusion
The decree that Christians must abstain from taking blood covers the taking of blood into the body, whether through the mouth or directly into the bloodstream.
Initially, J.W. adamant refusal of blood and blood products was met with much controversy and frustration.
At the time the accepted ‘rule’ was to transfuse a patient if their haemoglobin was below 10g/dl or haematocrit was below 30%.
Doctors viewed J.W. position as one that prevented them from rendering adequate care under certain circumstances
A few physicians viewed their stance as just one more complication challenging their skill and was a unique opportunity.
In 1957 Dr Denton Cooley of the Texas Heart Institute pioneered open heart surgery without blood support
He led a team of cardiovascular surgeons who performed some 1250 ‘bloodless’ open-heart surgery on patients who requested it
In those days, most open-heart surgeries required 20-30 units of blood
It was the genesis of the bloodless medicine and surgery
However the programme BMS was officially launched in 1997 at USC University Hospital and USC Norris Cancer Hospital California in consultation with the local hospital liaison committee for J.W.
Large population of J.W. residing in California at the time
UNIVERSITY OF SOUTHERN CALIFORNIA HOSPITAL COMPLEX
Highlights of the USC Programme include:
The 1st adult-to-adult living-related live-donor liver transplant in a Jehovah’s Witness patient without blood products in June,1999.
Followed up with paediatric liver-donor liver transplant
Others include “bloodless”
o Radical nephrectomy
o Cystectomy
o Hip/Knee surgery
o Ortho-spine surgery
o Heart transplants
o Cardiac bypass and valve replacement surgery
Currently there about 100 BMS centres in the United States
The medical community is learning that bloodless medicine and surgery has some benefits:
1.Helps Patients avoid problems such as Risks of contracting blood-borne diseases → HIV, Hep A,B,C Blood transfusion reactions Shortage of blood
2. Patients also recover more quickly from surgical procedures (immunomodulation - down regulation of cellular immunity by allogeneic blood). Extensive data showing that it enhances renal allograft tolerance
3. Significantly reduce medical costs A study conducted by members of Cleveland Clinics Anaesthesiology Department concluded that using a bloodless surgery protocol 50% of the time, could save the health care industry in the US up to $3.7 billion a year.
BLOOD CONSERVATION METHODS
PRE-OPERATIVE MANAGEMENT
INTRAOPERATIVE STRATEGIES
POST OPERATIVE MANAGEMENT
PRE-OPERATIVE MANAGEMENT
This involves appropriately Assessing, Investigating and Preparing patients prior to surgery to aid in reducing or avoiding allogeneic blood transfusion
This is a multidisciplinary approach: Blood bank technician(PABD) Physician (hypertension) Haematologist (haematological disorders) Surgeon (surgical approach or composition of team) Anaesthetist (intraoperative technique that can be used)
ASSESS and if possible manage (prior to elective surgery)
Anaemia
Bleeding/Coagulation disorders
Cardio-respiratory disorders
SIGNIFICANCE OF ANAEMIA
Definition: Haemoglobin concentration in blood that is below the expected
value with respect to certain factors such as age, gender, pregnancy and altitude
The unit of measure is “g/dl” → value dependent on ratio between Total amount of circulating Hb in RBC (numerator) Plasma volume (denominator)
Hence variation in either of the two factors will affect Hb concentration
RISKS OF ANAEMIA IN SURGERY
Existence of underlying pathology Anaemia is not a diagnosis but an indication that an underlying
pathology exists Hence treating pathology and/or associated anaemia will improve the
patient’s pre-operative condition
Decreased oxygen reserve in the body Surgical blood loss or cardio-respiratory depression due to anaesthetic
agents leads to decreased oxygen carrying capacity of the blood Hence the body tries to maintain tissue oxygenation by falling on
oxygen reserves in the body. However in anaemic patients their oxygen reserves are diminished and hence are at a higher risk of decompensation
PHYSIOLOGICAL RESPONSE OF THE BODY TO ANAEMIA
Adequate tissue oxygenation is required to meet tissues’ metabolic demands in order to sustain life
This depends on the balance between oxygen delivery to the tissue and oxygen demand (consumption requirement) by the tissue
Amount of O2 consumed by tissue
Amount of O2
in arterial blood delivered to tissue
Amount of O2
in venous blood leaving tissue
n = (CaO2).(CO)
Bound to Hb (normally >98% of total O2)
Dissolved in plasma (<2% of total O2) (negligible in normal situation)
+
+1.34 x [Hb] x % saturation of Hb
0.003mlO2 / mmHg PaO2 / 100ml plasma
CaO2 = arterial oxygen content
CO = cardiac output
* (n = CV)
Major determinants of O2 delivery to tissue - [Hb], % saturation, CO , PaO2(diseased states)
The Maximum extraction of O2 by any tissue is about 15 vol %
i.e.15ml O2 per 100ml of blood delivered - ( kinetics of oxygen dissociation from
Hb)
Since our Cardiac output = 5000ml/min (on the average for an adult)maximum amount of O2/min that can be extracted body under basal conditions
5000ml x 15100ml
= = 750ml O2/min
BIPHASIC RELATION BETWEEN OXYGEN CONSUMPTION AND OXYGEN DELIVERY
A = oxygen delivery independent portion (irrespective of amount of O2 delivered, basal O2 consumption is maintained)
B = oxygen delivery dependent portion (amount of O2 delivered linearly determines O2 consumption) At this phase tissue hypoxia sets in with anaerobic metabolism → ↑ lactate levels)
DO2 critical
It is the minimum amount of O2 required to maintain tissue oxygenation
Below this threshold, tissue hypoxia sets in
The most rigorous clinical study found a threshold value of 4ml O2 /min/ kg (3-4g/dl Hb)
The(4ml O2/ min/kg) value isn't accurate because: The DO2 critical measures is based on the average anaerobic threshold for the whole body at rest Different organs in the body have different anaerobic thresholds which may vary significantly from the body’s average
Also metabolic demands are increased in various diseased states
Right Heart
Left Heart
Arterial side
Normovolaemia
Hypovolaemia(sympathetic response )
Venous side
NormovolaemiaHypovolaemia
Microcirculation
TISSUE
Post capillary venule
*NormovolaemiaHypovolaemia
Pre-capillary arteriole
*Normovolaemia *Hypovolaemia-
shunting
capillary flow*Normovolaemia -↑ flow leads to ↑ recruitment of previously closed capillaries*Hypovolaemia – decreased flow due to ↑viscosity↑ O2 extraction
Due to shift of oxyhaemoglobin curve2,3 diphosphoglycerate levels increases after 12-36hrs with declining Hb level
Lungs
ASSESSMENT AND MANAGEMENT(ANAEMIA/BLEEDING DISORDERS/CARDIORESPIRATORY DISORDERS)
HISTORY - Look out for common causes of Anaemia, Bleeding disorders and Cardiorespiratory disorders
1. Anaemia
↓ Production Erythrogenesis – renal disease leading to ↓ EPO Factory – BM failure (haematological failure) Raw materials
Iron – bleeding from orifices (menorrhagia, haematuria, bleeding PR) Folate - ↓ utilisation of folate (metformin, phenytoin, methotrexate) Vitamin B12 – lack of IF (post gastrectomy (uncommon))
↑ Breakdown → Haemolysis Haemoglobinopathies (SCD – seasonal joint pains, jaundice) Malaria(Enemic region)
2. Bleeding disorders
Congenital Family history of bleeding disorders e.g. haemophilia A or B, Von
Willebrand disease
Acquired Liver disease Drug history
a) Platelet aggregation inhibitors NSAIDs (stop 10 days prior to surgery)
b) Anticoagulants Warfarin (stop 3 days prior to surgery and check INR) Heparin (stop at least 6 hours prior to surgery)
3. Cardiorespiratory disorders
Some diseases are contraindicated in certain blood conservation methods: IHD Hypertension
NB: Severe hypertension predisposes to severe bleeding during surgery. Hence BP needs to be controlled before surgery
Peripheral vascular disease Renal impairment Thrombotic strokes
PHYSICAL EXAMINATION
1. General Examination
Pallor (and degree) Conjunctivae Tip of tongue Nail beds Sole of feet Palm
Jaundice Haemolytic anaemia or liver disease
Skin manifestations of bleeding disorders Petechial haemorrhage – minute haemorrhage on body surface Ecchymosis – extravasation of blood from ruptured blood vessels into subcutaneous tissue Haematomas – especially in joint spaces
2. Cardiorespiratory System - For any abnormality which will affect oxygen delivery
3. Abdomen
Hepatomegaly
Splenomegaly Haemoglobinopathies Haematological malignancy (Haematologist consult)
INVESTIGATION
* Blood tests should not be routine to ↓ blood loss
1. Baseline FBC, Sickling test, BUE & Cr, CRP, ferritin
Platelet count ≥ 100 x 109/L Hb: 7-8g/dl is acceptable in well compensated and otherwise healthy
individual presenting for minor surgery However higher preoperative Hb is indicated before elective surgery in
the following Anaemia – Signs of decompensation (eg. angina, dyspnoea) Blood loss – major surgery/ significant blood loss expected(>10ml/kg)
(due to ↓ oxygen carrying capacity of blood)
Co-existing significant cardio-respiratory disease It may limit ability to further compensate for reduction in oxygen supply due to operative blood loss, cardio-respiratory depressant effects of anaesthetic agents
2. Specific Blood film comment, LFTs, folic acid and B12 level Clotting profile for coagulation disorders
TREATMENT OR CORRECTION
1. Anaemia ↓ EPO (renal disease) → recombinant human EPO ↓ folate → folic acid ↓Iron → Iron supplements ± EPO Malarial → antimalarials Helminthic infestation e.g. hookworm→ deworming (Albendazole)
2. Bleeding Disorders Need haematologist consult
3. Cardio-respiratory Disorders Need physician consult
Human Recombinant Erythropoietin
EPO is a glycoprotein produced by the kidney in response to tissue hypoxia
Renal tubular cells Renal peritubular cells Mesangial cells
Originally used in the management of chronic anaemia due to renal failure or cancer chemotherapy
Currently plays a key role in blood conservation.Used to augment preoperative Hct ± intention of PABD or ANH
Route: IM/ SC/ IV (gives higher plasma levels)
Dose varies but iron supplementation required
Mechanism of action Causes committed stem cells to be converted to RBC lines Dose dependent increase in reticulocyte count, Hct and Hb
Adverse Effects More common in patients with renal insufficiency Hence unclear if adverse effects are due to renal disease/ EPO
therapy/ Both CNS – seizures, CVA, hypertensive encephalopathy CVS: MI, hypertension Others: hyperkalaemia, thrombosis
INTRAOPERATIVE STRATEGIES
PATIENT POSITIONING(POSTURE)
ANAESTHESIA TECHNIQUE
AUTOLOGOUS BLOOD DONATION
PHARMACOLOGIC AGENT
SURGICAL TECHNIQUE
PATIENT POSITIONING (POSTURE)
Before surgery starts the patient is usually positioned to meet the needs of the surgery in question
Good patient posturing helps with Comfortable Access to surgical site
Reduction in Blood loss Good/ Clear view of the body part to be operated on Minimizes Damage to the nerves through traction/ compression
MECHANISM/ EFFECT OF POSTURE ON BLOOD PRESSURE AND BLOOD FLOW
BP effect
↑ going below heart
↓ going above heart
± 0.77mmHg per centimetre of vertical distance at the density of normal blood
Blood volume
↑ with ↑ BP (arterial/ venous)
↓ with ↓ BP (arterial/ venous)
NB: because the veins are more compliant than arteries (i.e. cα δV/δP); a small change in pressure in venous system leads to significant accumulation of blood)
1mmHg pressure increase in circulatory system can lead to accumulation of blood in the venous system up to 8 times the volume in the arterial system
Both (net effect)
Gravity
↑ increases blood flow (due to↑ BP)
↓ venous drainage (due to congestion)
Combination of the two leads to ↑ blood loss
Level of the operative site should be a little above the level of the heart → This will lead to ↓ blood flow to the operative site and reduces venous congestion
Trendenlenburg position (head down)
most appropriate for abdominal, pelvic, lower limb procedures
Reverse Trendenlenburg position (head up)most appropriate for head and neck surgery
NB: in the head up position
Pressures in the veins above the level of the heart are subatmosphereic
Hence if a large vein above the level of the heart is opened to the atmosphere during surgery, there is potential of air to enter the circulation causing an air embolus
This complication is rare and can be avoided with careful surgery
ANAESTHESIA TECHNIQUE
SPINAL ANAESTHESIA – Systemic vasodilatation
GENERAL ANAESTHESIA
CONTROLLED HYPOTENSIVE ANAESTHESIA
GENERAL ANAESTHESIA Volume of blood at operative site depends on two main factors
Blood flow to surgical site (Q) Determinants
MAP – prevents episodes of hypertension and tachycardia due to sympathetic overactivity by causing adequate levels of anaesthesia and analgesia
Peripheral resistance – prevent widespread vasodilatation due to hypercarbia (CO2 retention) by controlling ventilation
(need for capnograph monitoring)
Venous drainage from site Impaired by
Cough (impair venous drainage) Straining Patient movement
Adequate muscle relaxation to prevent unnecessary manoeuvre
CONTROLLED HYPOTENSIVE ANAESTHESIA This is the deliberate reduction in the blood pressure to facilitate surgery
and it improves the surgical field and may reduce blood loss between 30-50%
Contraindications include HPT, IHD or Valvular Heart DX, RF, previous CVA.
Posture
Regional epidural / spinal
Volatile anaesthetics
Hypotensive agents
B-blockers: Labetolol 2-10mg bolus. Infusion –2.5-30ug/kg/min
Esmolol, 50-250ug/kg/min
Vasodilators
Hydrallazine, 2-5mg boluses
Na nitroprusside, 0.3 – 0.5ug/kg/min
GTN, 0.25 - 5ug/kg/min
Phentolamine 1-4mg boluses
AUTOLOGOUS BLOOD TRANSFUSION (ABT)
Definition Transfusion: reinfusion Blood: of Blood Autologous: which belongs to same patient (after initial collection)
Classification Acute Hypervolaemic Haemodilution Acute Normovolaemic Haemodilution Periopertaive Blood Salvage) PABD (Preoperative Autologous Blood Donation)
This is done in the preoperative period Not accepted by Jehovah’s Witness’
ACUTE NORMOVOLAEMIC HAEMODILUTION
Definition Acute (process is conducted relatively rapidly over minutes) Normovolaemic: blood volume of patient is maintained normal/ same Haemodilution: blood of patient is diluted with asanguinous fluid
infusion
Synonyms Acute isovolaemic haemodilution Acute normovolaemic anaemia Controlled normovolaemic exsanguination
Indication General
Anticipated blood loss >20% of circulating blood volume
(1000ml for 5L volume)
Specific Accident centre: Orthopaedic surgery: joint replacement
procedure Cardio: cardiac surgery/ vascular surgery (major reconstructive vascular surgery) Ground floor: Neurosurgery (major back procedures) 1st floor
GU: urologic surgery – nephrectomy; cystectomy; prostatectomy
General surgery – major bowel resection; cancer resection Eye: ↔ ENT: ↔ MFU: ↔
Contraindication
Anaemic Level
Initial Hct ≥ 36% (Hb ≥ 12g/dl)
(* values as low as 24% may be acceptable – Hb ≥8g/dl)
Blood coagulation disorders Because dilution of blood with asanguinous fluid also dilutes
coagulation factors eg. platelets Hence this will worsen underlying coagulation disorders
Coexisting disorder CNS – significant cerebrovascular disease : cannot tolerate lower Hct
value CVS – severe hypertension/ underlying cardiac disorder (severe aortic
stenosis/ unstable angina) : cannot tolerate lower Hct value, impaired ability to compensate for anaemia
Resp – severe pulmonary disease : impaired ability to compensate for anaemia
Infants < 6/12 Persistence/ presence of foetal Hb leads to leftward shift of oxyhaemoglobin dissociation curve which impairs oxygen release at tissue level to compensate for iatrogenic dilutional anaemia
ACUTE NORMOVOLAEMIC HAEMODILUTION
Can be performed in awake or anaesthetised patients Awake – prior to induction of anaemia
Adv: Abundance of time to perform procedure Ability to assess heamodynamic consequences in absence of any anaesthetic agent
Blood collection bags that contain anticoagulant are neededCitrate is used typically premixed with phosphate and dextrose (CPD)
Can be performed in awake or anaesthetised patients Awake – prior to induction of anaemia
Adv: Abundance of time to perform procedure Ability to assess heamodynamic consequences in absence of any anaesthetic agent
Blood collection bags that contain anticoagulant are needed
Citrate is used typically premixed with phosphate and dextrose (CPD)
Calculation of volume of blood to be collected
[Baseline (Hb/ Hct)] - [Average (Hb/ Hct)]
[Target (Hb/ Hct)]EBV x
EBV – Neonates → 85-95ml/kg body weight Children → 80ml//kg body weight Adults →70ml/kg body weight
Baseline Hb/ Hct – ideally ≥12g/dl or 36% Target Hb/Hct – 7-8gdl or 20-25% (below this level may precipitate dilutional coagulopathy of tissue hypoxia)
Average Hb/ Hct = baseline (Hb/ Hct) + target (Hb/Hct) 2
Eg. Adult male (weight 90kg baseline Hb 14g/dl)
Elect Target Hb = 10g/dlEBV = 90 x 75 = 6750mlAverage Hb = (14+10)/2 = 12Volume of blood to be collected = (14-10)/ (12 x 6750) = 2250mlNB: max no. of units of blood removed is 3
INTRAVENOUS ACCESSa) Arterial line
Adv: arterial pressure serves as a pressure head that pumps the blood into collection bag
Disadv: inability to do invasive blood pressure monitoring; to monitor beat to beat BP
b) Venous access Adv: invasive BP monitoring possible Disadv: blood sequestration is a passive process and its speed is
influenced by gravity
Types:
a) Central ( + large bore peripheral IV) – most reliable and effective because lack of venous valves to slow down flow and cause sludging; most popular sites are internal jugular and subclavian (but can be placed anywhere)
b) 2 large bore peripheral – most popular but has sludging risks; needs at least 18G cannula; 2 large cannulae are inserted in opposite arms to aid flow)
Emptying
Patient 3 way tap attached to cannula opened for blood to flow into tubin Blood should be seen flowing through tubing of collection bag Must ensure that blood doesn’t lump and coagulate in the tube
leading to flow obstruction Tubing shouldn’t be too long to minimize tubing dead space Flushing of tubing periodically with N/ Saline
Collection bag Add mixture of blood and CPD ‘anticoagulant’ as blood flows into
collection bag to prevent sludging/ clumping off RBCs or platelets.(automatic or manual)
Blood quantity – typically 450ml of whole blood is collected into each bag.
Subjective: experienced eye to adjudge whether collection bag is overfilled or underfllled
Objective: weighing (1ml of blood weighs 1g)
Advantage: to accurately calculate amount of asanguinous fluid is required to maintain normal blood volume for adequate volume resuscitation
Labelling
Patient info: Name; Age; Sex; Hospital number
Collectors info: Name; date and time of collection
Marked: UNTESTED BLOOD FOR AUTOLOGOUS USE
Storage
Room temperature (20°C) Must be re-infused (after haemostasis controlled) within 6hrs as haemolysis takes place after 6 hours at room temperature 1st unit salvaged is given last
Refrigerant (0°C) To be used if not going to be re-infused within 6hrs Must be re-infused within 24hrs Disadv: decease or inactivate platelet function
Fluid resuscitation
Occurs concurrently with blood sequestration
Types – Crystalloids and colloids
1)Crystalloid (isotonic fluids) – N/S and R/L
Advantages Easily diuresed (prevent fluid overload) Inexpensive (cost)
Disadvantages Entire fluid does not stay in intravascular space. [3:1
replacement ratio (3ml crystalloid: 1 ml blood loss)] → ↓ colloid osmotic pressure → Tissue oedema → May compromise oxygen delivery due to increased diffusion
distance from vascular space to cells
2)Colloids Advantages
Stay in intravascular space [1:1 replacement ratio] Less risk of tissue oedema
Disadvantages Expensive Not easily diuresed Most colloids have a half life longer than 4hrs and may not be rapidly diuresed
from body Therefore there is at least the theoretical risk of hypervolaemina and fluid
overload if the sequestered blood is re-infused rapidly after haemostasis has been achieved
Types Short acting [t1/2 < 4 hours] – Pentastarch; Dextran 40
Intermediate acting [t1/2 4-24hrs] – Dextran 70
Long acting [t1/2 >24 hrs] - albumin, high molecular weight HES e.g. Hetastarch (can have adverse effects on haemostsis when infused in volumes >20-25ml/kg)
MONITORING
Basic
ECG – continuous HR (gives idea of volume replacement + urine output), ST segment info (ischaemic changes)
Pulse oximeter – oxygen saturation
BP – invasive BP preferred as it gives beat to beat blood pressure
Capnography – adequacy of circulation
Additional
CVP (central venous pressure) – assess volume status and oxygen delivery
PAP (pulmonary arterial pressure)
Transoesophageal echocardiography – real time assessment of ventricular and valvular performance
Haemodynamic consideration Physiological response to anaemia
In future Combination of ANH and artificial oxygen carrier Technique known as ‘Augmented ANH’
Jehovah Witness consideration ‘closed circuit ANH’ Whole blood collection circuit and fluid resuscitation system have to
remain continuous with patient’s intravascular compartments Once blood collection in patient has been achieved it should be
allowed to trickle slowly back into patient to resemble venous flow
NB: If all the whole blood cannot be administered in the operating room, reinfusion can continue in the recovery room. However when patients emerge from anaesthesia they and their families need to be prepared that the whole blood is autologous and it is the end phase of the ANH technique
CLOSED CIRCUIT ANH
– Advantages
1. RBC (Hb) Fewer loss of RBC & Hb per given volume of blood loss E.g. A - Starting at Hb=14g/dl
blood loss volume = 1000ml
amount of Hb loss = 140g (1000ml → 14g)
B - Starting Hb 10g/dl (after ANH)
blood volume loss = 1000ml
amount of Hb loss = 100g (1000ml → 10g)
Difference between A & B = 40g of Hb
2. Platelets and coagulation factros Provision of fresh supply durng re-infusion
Problems/ Pitfalls/ Disadvantages
A. Anaemia/ haemodynamic change during blood collection period leads to ↓ BP and ↑ HR
B. Blood clumping in tubing and collection bag – slows collection process
C. Collection bag overfilled/ underfilled
D. Distraction – conduct of anaesthetist OR blood collection process OR both
E. Entering allogenic blood pool in blood bank
ACUTE HYPERVOLAEMIC HAEMODILUTION
Definition Acute (process is conducted relatively rapidly over minutes) Hypervolaemic: blood volume of patient is increased Haemodilution: blood of patient is diluted with asanguinous fluid
infusion
Pitfalls This technique is not as widespread as ANH and is relatively new There is not enough data about its use and safety
Indications and contraindications Similar to ANH
Calculation of amount of volume expansion required to achieve Hct of 20-25%
Subjective – 20-40ml/kg IV fluids fast
Objective (Kumar et al proposed equation)
Volume of fluid to be infused=EBV x Hi – HT x EF
EBV – estimated blood volumeHi – initial haematocritHT – target haematocrit (20-25%)
EF – expansion factor
• Definition: depends on ability of fluid used for haemodilution to expand plasma volume of
patient
• e.g. Fluid with volume effect of 80% (i.e. 80% of fluid stays in intravascular space) will have EF = 100/80 = 1.25
• Hence its is important to choose fluid that has an intravascular residence time similar to the
time of surgery. This is in order to maintain hypervolaemia during surgery.
Colloids are preferable – HES, dextran 40, gelatin
HT
PERIOPERATIVE BLOOD SALVAGE
Definition Process of
Collection + anticoagulation Filtration ± centrifugation and washing Reinfusion of shed blood into the same patient
Classification Timing of collection of blood
Intraoperative period Post operative period
Unprocessed blood (not washed)/ Processed blood (washed)
Benefits of washing blood – discussed later
Indication General
Anticipated blood loss >20% of circulating blood volume Current blood loss is significant to require blood transfusion Blood type transfusion rare and adequate amounts of allogenic
blood cannot be found
Specific Elective cardiothoracic procedures Emergencies
Ruptured ectopic gestation Ruptured spleen
Contraindication
A. Amniotic fluid contamination - (seen in pregnant women). It initiates intravascular coagulation
B. Bacteria contamination – due to bowel contents/ infected wounds/ urine
C. Cancer surgery (controversial) Theoretical risk of dissemination of tumour cells because
standard filtration and washing does not remove malignant cells Risk is decreased by
Using specific filters (leucocyte depletion filter) Irradiation of salvaged blood to inactivate cancer cells
NB: There as been no established difference in prognosis in oncology cases between patients who had blood salvaged and those that did not.
D. Debris contamination (cells/ haemostatic agents protamine and thrombin]) – may initiate intravascular coagulation
E. Erythrocyte destruction (Haemolysis) – shed blood of more than 6hrs should NOT be re-infused since haemolysis of RBCs s likely to be complete
F. Fat contamination
This is often seen in orthopaedic surgery due to the marrow fat in wound blood
This is associated with fat embolism and related pulmonary endothelial damage
NB: even after filtration and washing or salvaged RBCs a s significant amount of fat remains in blood
*SCD is not contraindication for blood salvage
Sickle cells occur when Hb is deoxygenated. However in cell salvage blood id in contact with air and therefore Hb is oxygenated
Anticoagulants(why) blood collected from operation site comes into contact with tissue
factors leading to activation of clotting cascade with FDPs formed; leading to reduced levels of fibrinogen in salvaged blood
(≈ 1g/L) Hence Salvaged blood is unlikely to clot and block tubing of
conservation device. However if bleeding is brisk e.g. great vessels bleeding, there wont be enough time for blood to be exposed to tissue factors
Need to use anticoagulant regardless of rate of blood loss to be on a safer side
Anticoagulants(Types)
Heparin – avoid in patents with platelet dysfunction or heparin induced thrombocytopaenia (HIT)
CPD (citrate-phosphate-dextrose) Citrate – chelates calcium
Adv: improves platelet function Disadv: hypocalcaemia in hepatic insufficiency
Dextrose – used as a substrate for RBC glycolysis by-product of glycolysis is 2,3-diphosphoglycerate (DPG) 2,3-DPG regulates oxyhaemoglobin affinity by interposing itself between β-globin
chains of Hb molecule When β-globin chains are farther apart Hb oxygen affinity decreases leading to
increased oxygen release When β-globin chains are closer together Hb affinity increases leading to
decreases oxygen release NB: it takes about 18-36 hours for [2,3-DPG] in banked blood to return to normal
levels. During this period oxygen release to tissues is NOT effective
3 devices (based on method of blood collection)
Manual collection devices
Simple suction collection devices
Automated suction collection systems
Manual collection devices Collection: surgeon uses sterile ladle or small bowl to collect blood
from body cavity and transfer it into a larger bowl or kidney dish
Anticoagulation: anticoagulant solution from sterile bottle is added
Filtration: (Blood and anticoagulant) are filtered through4-6 layers of sterile gauze placed in a funnel into receiver
Reinfusion: the ‘receiver’ (sterile bottle containing the blood) is sealed with a stopper and re-infused into the patient using a blood transfusion set
MANUAL COLLECTION DEVICES
Simple suction collection devices Collection – simple suction machine creates a negative pressure
vacuum in canister to produce a pressure gradient between the canister and body cavity (source of blood). This causes blood to flow towards canister.
NB: maximum suction pressure should be 100mmHg (negative pressure) because higher suction pressure cause excessive haemolysis of RBC
Anticoagulant – It is added manually via port on canister (reservoir)
Filtration – blood and anticoagulant filtered through a micro filter (20-150µm) to remove large particles and cellular debris from blood, into a rigid reservoir with a disposable liner or collection bag
± washing: blood washing device
Reinfusion: processed or unprocessed using standard blood transfusion set
SIMPLE SUCTION COLLECTION DEVICES
Simple suction collection devices
BLOOD WASHING DEVICE
Automated suction collection systems Collection: automated suction is a blood aspirator with a double
lumen
Anticoagulant One lumen: aspirates blood from surgical site or operative field Second lumen: it is an anticoagulation line so that anticoagulant
can be combined with aspirated blood at a controlled rate.
Filtration: anticoagulated blood is filtered into a disposable reservoir
Washing: filtered blood is then centrifuged – this separates denser RBCs from plasma and
dissolves solutes (WBC, platelets, anticoagulants, cellular debris, RBC free Hb and other contaminants)
washed with saline- This dilutes plasma and dissolves solute and discarded.
Reinfusion: the salvaged RBCs are then re-suspended in normal saline and transfused immediately or within 6 hours
AUTOMATED SUCTION COLLECTION SYSTEMS
complications
More likely to occur when using large volumes of unwashed blood
Advisable NOT to salvage more than 1500ml of unwashed blood
A. Air embolism
B. Breathlessness (pulmonary insufficiency)
C. Coagulopathy and calcium derangement
D. Disease (sepsis)
E. Electrolyte imbalance and acid-base disturbance
F. Fat embolism
G. GU – renal dysfunction
H. haemolysis
A. Air embolisma) Aetiology – reinfusion of blood done under pressure (rare
complication)
b) Effect – mortality
B. Pulmonary dysfunctiona) Aetilogy - debris/ fatty acid (toxic) – damage pulmonary vasculature
b) Effect – pulmonary oedema etc.
C. Coagulopathya) Aetiology
anticoagulant usage – heparin/citrate may be re-infused in large amounts if washing of salvaged RBCs is not done properly
washing technique – washing of large volumes of salvaged blood (>2L) can lead to loss of platelets and clotting factors into waste bag. Monitoring of clotting profile is indicated when large volumes of RBCs are salvaged
DIC (intracellular components of blood activate coagulation cascade)
b) Effect - bleeding
C. Calcium homeostasis altered
a) Aetiology Citrate overload (anticoagulan)
↑ entry – large volumes of blood salvaged (↑ amounts of CPD)
↓ exit – hepatic insufficiency – slow citrate metaboliism
b) Effect – chelates serum calcium lading to hypocalcaemia
D. Sepsis – occurs when there is contamination of disposable circuit
E. Electrolyte imbalance
a) Aetiology – dilutional due to re-suspension of salvaged RBCs in saline for transfusion
b) Effect – depends on electrolyte
E. Acid-base disturbance
a) Aetiology – re-suspension of salvaged RBCs in saline
b) Effect – hyperchloraemic acidoses
F. Fat embolism
Explained under contraindication
G. Renal dysfunction and Haemolysis
a) Aetiology – haemolysis due to:
High suction level
Aspiration causing excessive mixing of air with blood
b) Effect
Turbulence of air → shear stress n RBC membrane → destruction of RBCs → free Hb → excess free Hb (Hb ≥ 150mg/dl exceeds binding capacity of haptoglobin) → haemoglobinuria → ARF
NB: if adequate diuresis is maintained (until urine free of Hb) Hb can be excreted without renal duysfunction
Monitoring – bedside dipstick (positive for RBCs); microscopy (no RBC)
Damage/ Malfunction of auto-transfusion devices
If tubing from the reservoir bag to the cell saver analyser is inadvertently clamped, pressure builds up in the tubing and this will cause tubing to disconnect from analyser and spray blood throughout operating room
Such problems mandate the need for personnel involved in the use of cell saver devices to be educated and familiar with the equipment prior to operating the device
PREOPERATIVE AUTOLOGOUS BLOOD DONATION
Definition
D – donation
B – of blood
A – by a patient
P – in the elective preoperative period
and subsequently re-infused into the same patient if operative blood loss necessitates blood transfusion
Indication
Surgical blood loss likely to result in transfusion (≥ 20% circulating blood volume)
Contraindication
A. Anaemia – patient unsuitable if Hb ≤ 10g/dl or Hct ≤ 30%
B. Bacteraemia
C. Cardio-resp disorders – angina, aortic stenosis, respiratory failure
D. Disorders – SCD/ anticoagulant therapy/ uncontrolled hypertension/ IDDM
NB: Age and weight are no longer a restriction
Paediatric age group – do not donate more than 10% of blood volume
Weight < 50kg – do not donate more than 9ml/kg
Process
A. Awareness of patient : Benefits of procedure Risk of procedure (including possibility of homologous transfusion Consent form signed Minimum criteria for autologous BP at the time of each donation
B. Collection Onset: about 5 weeks prior to surgery Duration: in adults about 1 unit of blood (450ml) is collected weekly (7
days) but last unit is collected at least 5 days prior to surgery Reason – allows time for the Hct to increase and time for plasma
proteins to normalise intravascular volume prior to surgery Effect – 4-5 units of blood may be available for use by the date of
surgery
Drug (oral haematinics)
Iron ± EPO helps boost Hb
Problems
Postponed or cancelled surgery
2 options
Crossover technique – into homologous pool
Leapfrog technique – serial re-transfusion of stored blood starting with the oldest donated blood. Then fresh unit of blood donated later.
Fridge storage
Blood should be stored in a refrigerator at 4°C (up to 35 days) in a section of the refrigerator separate from the homologous blood pool
Blood should be clearly labelled with name, age, sex, hospital number, blood group, AUTOLOGOUS BLOOD INSCRIPTION.
GXM
ABO grouping is required for patient identification
Other tests on blood donated are mandatory if cross over s going to occur e.g. transfusion transmitted disease
48hrs prior to surgery, fresh blood sample of patients is taken to ensure ABO compatibility because of increased risk of procedural errors leading to incorrect identification
Haemotransfusion indication
This should be based on same criteria used for the transfusion of homologous blood and should not be merely given because it is available
This is because of the risks of incorrect identification and possible bacterial contamination with banked blood.
Advantages Decreases need for homologous blood and its problems Crossover effect - provided donor has met all the criteria for
homologous blood donation (↑ donor blood pool)
Disadvantages Administrative setup required – considerable planning and
organisation required Bacterial contamination of blood id possible Cost is higher than allogeneic blood transfusion Disability may lead to ineligibility to donate e.g. severe cardiac
disease Errors such as clerical/ procedural which may cause
incompatibility of blood
PHARMACOLOGIC AGENTS FOR BLOOD CONSERVATION
Definition: drugs used to help reduce operative blood loss
Classification Procoagulants – encourage clot formation
rVIIaDDVP
Antifibrinolytics – slows down clot dissolutionTranexamic acidAprotinin
COAGULATION CASCADE
TPA + fibrinogen
I. Recombinant Factor VIIa Definition: obtained via recombinant DNA technology Kinetics:
(route) → intravenously (IV) dose varies (20-40µg/kg over 3 minutes)
Dynamics:
Factor VII plays a key role in extrinsic pathway (requiring tissue
damage) by activating Factor X which then enters common
pathway of coagulation cascade
Effect:
Non-specific symptoms such as headaches, nausea, vomiting
II. Deamino-8-D-arginine vasopressin (DDAVP)/ Desmopressin Definition: synthetic analogue of arginine vasopressin (ADH)
D – deamino – demination of hemicysteine at position 1 (one) of ADH (AVP)
Adv: protects DAVP from peptidase degradation hence prolongs t1/2 to 55-60 minutes
D – arginine – this substitutes L arginine at position 8 (eight) of AVP
Adv: limits activity of DDAVP on V1 receptors found on smooth muscle
CVS – hypertension Resp – broncho-constriction GIT – cramps Uterus - cramps
Route: intravenously (IV), subcutaneously, intranasally (both equally effective as IV but plasma concentration peaks after 1 hour)
Bioavailability (dose): 0.15-0.3µg/kg intravenously over 15-30 minutes n morning of surgery
Rapid administration causes endothelial cells to release prostaglandin which causes systemic vasodilatation and hypotension
III. Epsilon Aminocaproic Acid (EACA) & Tranexamic Acid (TXA)
Definition They are γ-amino carboxylic acid analogue of lysine (γ-ACL)
Route: oral/ IV (preferred in perioperative period) Bioavailability (dose)
EACA – loading: 100-150mg/kg; maintenance dose 10-15mg/kg/hr
TXA – loading: 10mg/kg; maintenance 1mg/kg/hr
lower doses than EACA becaue 7-10x more potent
Excretion EACA: 90% is excreted in urine within 4-6hrs of administration TXA: 90% is excreted in urine within 24hrs of administration
Epsilon Aminocaproic Acid (EACA) & Tranexamic Acid (TXA)
Definition
They are γ-amino carboxylic acid analogue of lysine (γ-ACL)
Route: oral/ IV (preferred in perioperative period)
Bioavailability (dose)
EACA – loading: 100-150mg/kg; maintenance dose 10-15mg/kg/hr
TXA – loading: 10mg/kg; maintenance 1mg/kg/hr
lower doses than EACA becaue 7-10x more potent
Excretion
EACA: 90% is excreted in urine within 4-6hrs of administration
TXA: 90% is excreted in urine within 24hrs of administration
MECHANISM OF ACTION
Competitive inhibition – binds to fibrinogen (at lysine potion) and this prevents TPA from binding to fibrinogen. Hence TPA is degraded rapidly. This reduces rate of conversion of plasminogen to plasmin (fibrinolysis) to lyse clots
Non-competitive inhibition – directly inhibits plasmin at higher concentrations
Adverse effects
Increases perioperative thrombotic events
Nausea, vomiting, diarrhoea, hypotension (when administered rapidly IV)
Aprotinin
Naturally occurring Serine Protease Inhibitor (SPI) which was first isolated from bovine lung in 1930
Route: Intravenous
High dose ≈ 6 million KIU
Intermediate dose ≈ 2-6 million KIU
Low dose < 2 million KIU
NB: KIU – kallikrein inhibitory units
Distribution Rapidly redistributed into extracellular fluid → Rapid accumulation in renal tubular epithelium → Rapid lysosomal degradation → Hence need for continuous infusion to maintain adequate
plasma concentration
Mechanism of Action Decreased coagulation: inhibits plasma kallikrein →
inhbition of formation of Factor XIIa in intrinsic pathway Decreased fibrin formation: inhibits plasmin
Adverse effects Increased peri-operative thrombotic events Renal toxicity (due to rapid accumulation in renal tubule)s Allergic reaction
SURGICAL TECHNIQUE The training, experience and care of the surgeon performing the
procedure is the most crucial factor in reducing operative blood loss
It involves preoperative planning and appropriate intraoperative techniques
Preoperative planning Surgical team composition: an enlarged team helps reduce operating
time hence reduce operative blood loss Strategy of complex procedures e.g. urethroplasty: This helps patients
to recover haemodynamically between procedures to reduce need for transfusion
Appropriate surgical technique
Non-invasive procedures No blood loss e.g lithotripsy (sound waves to break up kidney
stones into smaller bits allowing it to pass out of the urinary tract without creating an incision or cut
Minimally invasive procedures Little blood loss e.g. laparoscopy (key hole surgery), endoscopy
Invasive procedures
Risk of major blood loss. Hence:
Use vasoconstrictors: reduce blood flow to surgical site → ↓ blood loss
Use of Tourniquet
Meticulous heamostasis: Sutures Devices: electrocautery, argon beam coagulator Microwave coagulating scalpel
POSTOPERATIVE MANAGEMENT Blood loss and hypovolaemia can still occur in postoperative period
Hence it is important to try and prevent it. But if it still occurs, detect it early and treat
Preventative measures Postoperative oxygen
Inadequate oxygenation is a common problem in the early postoperative period particularly following GA
This will be confounded by the effects of reduced HB level and hypovolaemia which occurs →
Leading to tissue hypoxia Hence it is important to give supplementary oxygen to all patients
recovering from GA and monitoring O2 saturations sing pulse oximeter
Vitals monitoring ECG – ST segment changes to indicate ischaemia Pulse & BP
Tachycardia could be due to hypovolaemia Need to regularly check wound and drains for bleeding/
haematoma Postoperative blood salvage can be done if wound drain is insitu
Hypertension could be due to pain This may aggravate bleeding and increase blood loss Hence need to provide sufficient analgesia throughout
perioperative period
Fluid balance Fluid input-output chart should be monitored to ensure
normovolaemia
Intervention
Secure haemostasis (early surgical re-exploration) This is indicated where significant blood loss continues to occur in
the postoperative period and there is no treatable disturbance of the coagulation status of the patient
Top-up Haematinics: this will optimise the erythropoietin response and
restore the Hb level to normal more rapidly
Blood transfusion Indication based on
Anaemia – postoperative Hb Baseline – general condition of patient (whether surgery of
inadequate tissue oxygenation) Coexisting cardio/resp disease Continued blood loss
FUTURE OF BLOODLESS MEDICINE AND SURGERY (BLOOD SUBSTITUTES/ OXYGEN THERAPEUTIC AGENTS )
Blood substitutes/ oxygen therapeutic agents
Definition: A blood substitute is a pharmacological agent that performs the typical functions of natural blood
Types of red cell substitutes:
• HBOC - Hemoglobin-based oxygen carriers
• PBOC - Perfluorocarbon-based oxygen carriers.
A. Haemoglobin based oxygen carriers
These are being developed to allow oxygen transport by free Hb.
Older oxygen therapeutic agents have existed since 1930s using lysed RBC; however although they demonstrated oxygen carrying properties they were nephrotoxic in nature. Other side effects were attributed to dissociation of the Hb tetramer into dimers and polymers
Currently 3 different substitues exist and are undergoing clinical trials
PolyHeme, which is a glutaraldehyde cross-linked human Hb;
Used in patients with severe injuries – led to reduction in overall 30-day mortality and reduction in allogenic blood use overall as well as a reported reduction in incidence of multi-organ failure
Hemolink (o-raffinose polymerized Hb);
Prepared from is prepared from outdated human RBCs. The cells are washed to remove plasma proteins and lysed (gently) filtered and pasteurised and finally purified using chromatography
Added to ringers lactate to produce product with Hb concentration 10g/dl
Has been trialled in patients undergoing coronary artery bypass graft in conjunction with ANH.
Overall patients had increased transfusion avoidance and reduction in units of allogenic blood transfused
Hemopure, which is a glutaraldehyde cross-linked bovine Hb
Lower oxygen affinity compared to Human Hb so facilitates easier oxygen unloading in tissue
Does not require refrigeration and is stable at room temperature for 2 years
Clinical trials have demonstratd reduction in transfusion requirements
Recent development of newer tetrameric rHb that do not cause vasoconstriction when infused and have fewer side effects eg. Hemozye, MP4 ( a tetramer combined with polyethylene glycol to create larger molecule to stay in intravascular space)
Perfluorocarbon-based oxygen carriers e.g. Fluosol 20
Definition carbon fluorine compounds characterized by a
high gas dissolving capacity (oxygen and carbon dioxide) low viscosity and chemical and biological inertness.
Unlike haemoglobin with sigmoid shaped dissociation curve, there is a liner relationship between oxygen partial pressure and oxygen content
Must be given with supplemental oxygen to maintain relatively high arterial oxygen partial pressures, which are necessary to maximize the oxygen transport capacity of fluorocarbon emulsions.
Intravascular perfluorocarbon solutions loaded with oxygen at a PaO2 of 200 mmHg can deliver 5 vol% of oxygen per decilitre of perfluorocarbon
Perfluorocarbons release 80% of their carried oxygen so can deliver approximately four times the oxygen that would be delivered by the same volume of Hb.
Giving 120 ml of Oxygent to a 70-kg patient is equivalent to 500 ml transfusion of whole blood
CHARACTERISTICS OF MAJOR OXYGEN THERAPEUTICS
CONCLUSION Patients should be given the option of choosing autologous blood
transfusion
They have the choice of PABD, ANH or soon Blood salvage
ANH provides warm, platelets and Factor VIII rich blood
Combination of PABD and ANH is possible
It is relatively easy to perform and reasonably safe
Erythropoietin is an accepted therapy for the increase in the Hb for autologous blood transfusion
EPO is worth its price when one thinks about HIV and this is accepted among Jehovah's witnesses
Properly planned rare blood groups can be easily done
Other blood conservation methods must be employed before thinking about allogenic blood
A patient who needs just a unit of blood probably does not need it
REFERENCES
1. Cardiovascular Physiology Concepts – Myocardial oxygen extraction: www.cvphysiology.com/CAD/CAD008.htm (Richard E Klabunde PhD)
2. Review of physiologic mechanism I response to anaemia: Paul C Herbert (MD, FRCPC, mHSc), Ling Qun Hu, George Bird
3. Acute normovolaemic anaemia: Physiological and practical concerns: P. Van der Linden (Dept. of Anaesthesiology, CHU Brugmann, Brussels, Belgium)
4. Anaemia and red blood cell transfusion in the critically ill patient: S.A. McLellan, D.B.L. McClelland, T.S. Walsh
5. Network for advancement of Transfusion alternative (NATA)
6. Oxygen delivery and consumption: Ilene M. Roben MD, Scott Manaker MD
7. Critical care medicine tutorials (oxygen)
8. Oxygen delivery: Nathan W Peterson, Lisa Moses
9. Acute Normovolaemic Haemodilution: Larry Eitel
10. Role of the red blood cell in Nitric oxide homeostasis and hypoxic vasodilatation: Mark T Gladwin
11. Peri-operative anaemia management: consensus statement on the role of intravenous iron
12. www.nba.gov.au/guideline/module2
13. medicine for residents- Iron and iron deficiency anaemia- quick recap
14. A Physician’s Guide to oral iron supplements (www.anemia.org)
15. Perooperative blood conservation www.schulich.vwo.ca/anaesthesia/perioperative-blood-conservation
16. WHO – clinical use of blood pdf
17. Iron metabolism – wikipedia
18. Oxygen content of blood: Anaesthesia UK (www.frca.co.uk/article)
28. Techniques of reducing perioperative blood loss by G. Inghitter
29. Cell salvage as part of a blood conservation strategy in anaesthesia (bja.oxfordjournals.org)
30. ANH policy in surgical patients
31. Global Blood safety Initiative (autologous transfusion in developing countries)
32. Transfusion alternatives for Jehovah’s Witnesses (St George’s Healthcare)
33. Cardiovascular pharmacology concepts – vasopressin analogues
ACKNOWLEDGEMENT
THANK YOU