		Male	Female
PT	· kept at 1.5X when on oral anticoagulants · 2.5X is associated with abnormal bleeding · prolonged: deficiencies in extrinsic &/or common pathway factors [I, II, V, VII, X] 2° liver dx; coumarins;vit K def	9.5-12 sec
APPT	· prolonged: deficiencies in any of the factors within the intrinsic &/or common pathways eg 2° heparin; fibrin split products	25-36 sec
INR
Hct		42-54%	38-46%
Hb		14-18 g/dl	12-16 g/dl
RBC		4.5-6.2x10⁶/ul	4.2-5.4x10⁶/ul
Platelet count	· reduced during DIC, heparin tx	130,000-370,000 per mm³
Fibrinogen	· depressed during DIC, liver dx, trauma · deficiency associated with prolonged PT & APTT	200-360 mg/dl
Sickle cell test [HbS]		Nil

Significance of antibodies

1) Cold Haemagglutinin dx

· Autoantibodies against RBCs in patients with haemagglutinin disease are activated by even transient cold exposure

· Usually IgM

· At temperatures below the critical temperature for an individual patient, haemoagglutination will occur

· Resulting in vascular occlusion leading to organ ischaemia or infarction

· Haemoagglutination may also fix complement leading to haemolysis

· Heart is most susceptible as is exposed to coldest temperatures

HEPATIC DYSFUNCTION

1. Key clinical findings

a) History of hepatitis

b) Ascites

c) Serum bilirubin > 3 mg/dl

d) Serum albumin < 3 g/dl

e) Elevated PT

2. Acute hepatitis

a) Viral, alcoholic, toxic

b) High perioperative mortality & morbidity

i) Approx 1 month after dx onset

ii) Until AST (aspartate transferease) returns to normal

iii) No elective surgery during this time

3. Chronic hepatitis

a) High perioperative mortality & morbidity if:

i) Serum albumin < 3

ii) Serum bilirubin > 3

4. Clotting Abnormalities

a) Elevated PT

i) deficits II, X, VII, IX (manufactured in liver)

b) Treat with vitamin K, FFP

c) Note: if liver dx is severe enough to elevate PT, expect reduced drug metabolism & prolonged drug action (esp lignocaine)

5. Abnormal electrolytes

a) Hyperaldosteronism & diuretics:

i) hyponatraemia, hypokalaemia, metabolic acidosis

6. Liver function tests (hepatic enzymes)

a) crude marker of liver destruction rather than function

RENAL DYSFUNCTION

1. Key clinical findings

a) Daily urine output

b) Serum creatinine

c) Body weight

d) Serum electrolytes

e) Haematocrit

2. Renal failure & CPB

a) Reduced ability to handle :

i) large volume loads (ie prime)

ii) High potassium loads (cardioplegia)

3. Metabolic acidosis

i) Acidosis during CPB in addition to preexisting metabolic acidosis may reduce myocardial contractility

4. Anaemia

a) Anaemia with chronic renal failure will be exacerbated with crystalloid prime

5. Pericarditis

a) Pericarditis is associated with CRF with may to pericardial adhesions

6. Serum creatinine

a) Range 0.6—0.9 mg/dl [fem]; 0.8—1.2 mg/dl [male]

b) More sensitive than BUN in determining renal damage

c) An end product of protein metabolism

d) Directly related to GFR

e) Appears in serum proportional to muscle mass

f) Becomes elevated when > 50% of nephrons are damaged

7. Blood Urea Nitrogen (BUN)

a) Range 8 — 20 mg/dl

b) Chief end product of nitrogen metabolism

c) Reflects protein intake and renal excretory capacity

d) Elevated:

i) Renal disease

ii) Reduced renal blood flow (eg dehydration)

iii) Increased catabolism (burns)

e) Decreased:

i) Liver damage (as is produced in liver)

ii) Malnutrition

iii) Overhydration

Pathological lesions that may affect CPB: carotid disease; dissections; left superior cavae

1. Carotid disease

2. History of TIA’s or visual disturbances or nonsymptomatic carotid bruit should warrant a noninvasive Doppler carotid flow study

a) Patients with symptoms & > 70% stenosis would benefit from carotid endarterectomy

3. Asymptomatic carotid stenosis does not increase the risk of perioperative stroke

4. Even in absence of symptoms, assume > 70 years age with coronary artery disease also has some cerebrovascular disease

5. Fixed lumen diameter; minimal autoregulation (adequate flow at normal BP may be inadequate at lower BP)

a) CPB management:

i) Maintain mean CPP within patients autoregulatory range (eg preexisting hypertension) [> 60 mmHg]

ii) Maintain Hct > 20%

iii) pCO₂ management?

a) moderate hypercapnia to promote cerebral vasodilation (but increased exposure to emboli!)

iv) Hypothermia?

_a)reduced brain requirement for O₂

b) maintain adequate CPP during rewarming as brain warms rapidly

c) whilst cold, lower pressures are well tolerated as autoregulation is preserved at lower BP

v) Euglycaemia [diabetes]

a) hyperglycaemia increases extent and magnitude of cerebral injury during ischaemia

6. Renovascular disease

a) Increased care with hypotension on CPB

b) Mannitol & other diuretics may help preserve renal function intraoperatively

c) Urine output (<1ml/kg/hr)

7. Peripheral vascular disease

a) History of claudication

b) Peripheral pulses palpated

c) To determine sites for:

i) arterial pressure monitoring

ii) insertion site for IABP

iii) Arterial CPB cannula (eg femoral)

8. Aortic Dissection

a) Dissection may extend into iliac & femoral arteries; usually along left side

i) Cannulation is safer via right side

b) Femoral cannulation concerns

i) Inadvertent occlusion of aortic true lumen by retrograde flow via false lumen

ii) Watershed effect

iii) Increased afterload on heart

iv) Flushing of debris retrogradely into brachiocehalic arteries

v) Lower extremity ischaemia

9. Left superior cava

a) Failure to cannulate a left superior cava may impair cerebral venous drainage

b) A left SVC with left atrial connection may be associated with drainage into LV with subsequent distension

10. Dextra-rotation

a) Issues of cannulation positioning

Required physical characteristics to calculate flows. Advantages and disadvantages of weight versus BSA

By weight:

Adults: 40 — 60 ml/kg/min

Paediatrics: 60 — 80 ml/kg/min

Neonate: 80 — 100 ml/kg/min

By BSA:

Adults: 2.4 l/min/m²

Paediatrics: 2.6 l/min/m²

Temp °C	Cardiac index [l/min/m²]
34-37	2.4
30-34	2.0
25-30	1.8
20-25	1.5
< 20	1.0

· BSA is currently preferred as the flow rate can be normalised so that it can be made applicable to patients of varying body sizes

· Issue of fat versus muscle