Transcript CARMICHAEL TORRANCE DIAGNOSTIC SERVICES

Beyond Pre-Anaesthetic
Testing
Nick Carmichael
BVM&S, BSc VetSci(Hons), Diploma VCS(Syd),
Diploma RCPath, Diplomate ECVCP, MRCVS
Aims of pre-anaesthetic testing
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Screen for the presence of intercurrent
disease
Allow adjustments in anaesthetics/ drugs
used to be made
Provide baseline data if problem develops
later
Benefits of pre-anaesthetic testing
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Safer anaesthesia
Appropriate perioperative management
Early identification of clinically silent
problems
Drawbacks of pre-anaesthetic testing
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Cost benefit analysis
“False positive” screening test results
Inappropriate labelling of cases
“False negative” screening test results
Decision time pressure
Cost Benefit Analysis
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Detection rate of abnormalities ~ 1-11%
veterinary
Detection rate of abnormalities~ 2% man
Evidence of reduced anaesthetic morbidity
and mortality~ ??
What are the major anaesthetic risks?
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Excessive anaesthetic administered
Hypotension
Cardiac rhythm abnormalities/ arrest
Ventilation/perfusion imbalances
Would pre- anaesthetic bloods predict /
ameliorate these?
Pre-anaesthetic testing requirements
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Sensitive
Specific
Relate to organ function
Low cost
SCREENS VS PROFILES
Diagnostic Profiles
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Screens
Contains grouped tests
 Contains a single test
related to organ function
per organ
Tests provide complimentary  Single most sensitive
test included
information
 Test array is fixed
Tests included relate to a
 Provides yes/no
presenting sign
information regarding
normality
Assists in localisation/
narrowing of the DDx
Pre-anaesthetic screen components
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FBC
Total protein
Urea
ALT
ALP
Glucose
(Electrolytes)
Full Blood Count abnormalities in
Pre-anaesthetic screens
Tiny, boxer male 3yr
Total protein
Urea
Creatinine
Alk Phos
ALT
Total bilirubin
Glucose
68
3.3
91
* 707
* 233
6
5.3
g/L
mmol/L
umol/L
U/L
U/L
High
umol/L
mmol/L
(54.0 -77.0 )
(2.0 -9.0 )
(40.0 -106.0)
High (0.0 -150.0 )
(0.0 -25.0 )
(0.0 -20.0 )
(3.5-6.5)
Tiny, boxer male 3yr
RBC
Hb
HCT
MCV
MCH
MCHC
Platelets
WBC
Neutrophils
Lymphocytes
Monocytes
Eosinophils
* 2.83
* 6.9
*21.9
77.0
24.3
31.5
* 66
* 1.89
* 39%
57%
3%
1%
x10^12/L
g/dl
%
fl
pg
g/dl
x10^9/L
x10^9/L
0.74 x10^9/L
1.08 x10^9/L
0.06 x10^9/L
0.02 x10^9/L
Low
Low
Low
Low
Low
Low
(5.0 -8.5 )
(12.0 -18.0 )
(37.0 -55.0 )
(60.0 -80.0 )
(19.0 -26.0 )
(31.5 -37.0 )
(160 -500 )
(6.0 -15.0 )
(3.0 -11.5 )
(1.0 -4.8 )
(0.0 -1.3 )
(0.0 -1.25 )
FBC abnormalities
White Cells : Atypical Lymphocytes
FBC abnormalities
Red Cells: Schistocytes
FBC abnormalities
Platelets: Thrombocytopenia & Platelet Clumps
Daisy, CKCS FN 2yrs
Total protein
Albumin
Globulin
Total calcium
Phosphate
Urea
Creatinine
Alk Phos
GLDH
Gamma GT
Total bilirubin
Bile acids
Glucose
↑86
32
↑54
2.86
↑3.51
↑14.9
101
↑578
↑87
25
↑30
↑26.7
68
32
36
2.70
2.10
↑13.3
↑152
↑455
12
25
6
9.7
g/L
g/L
g/L
mmol/L
mmol/L
mmol/L
umol/L
U/L
U/L
U/L
umol/L
umol/L
6.4
5.6
mmol/L
Interpretation of Biochemical results
Total Protein
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Normal TP 50:50 alb:glob
Normal TP, 10:90 AG
Hypoalbuminaemia
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Significance
Anaesthesia
Wound healing
effusion formation
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Causes
Increased loss
Reduced production
Effusion formation
Hypoalbuminaemia
Investigation
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Evidence of effusion /exudation
Evidence of increased renal/ GI loss?
Evidence of inflammation?
Evidence of impaired hepatic function?
Hyperglobulinaemia
Associated with
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Inflammation
Viral infection
Neoplasia
Severe Hyperglobulinaemia
Effects
 Impaired primary haemostasis
 Blood hyperviscosity
Differentials
 Feline viral infections
FIV, FIP, Felv
 B-cell derived neoplasia
Lymphoma, myeloma, (plasmacytoma)
 Non indigenous infections
Leishmania, Ehrlichia, Borrelia
Hyperglobulinaemia
Diagnostic evaluation
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Clinical examination
FBC – smear evaluation
Viral screening
Serum protein electrophoresis
Non indigenous infection serology/ PCR
testing
Tess 11y, FN Cross breed dog
Epistaxis for 1 year, NAD on skull Xray
RBC
Hb
HCT
MCV
MCH
MCHC
Platelets
WBC
Neutrophils
Lymphocytes
Monocytes
Eosinophils
↓ 3.67
↓ 9.0
↓ 27.8
76.0
24.5
32.4
357
8.46
77%
20%
0.%
3%
x10^12/L
g/dl
%
fl
pg
g/dl
x10^9/L
x10^9/L
6.5x10^9/L
1.6x10^9/L
0.0x10^9/L
0.2x10^9/L
5 - 8.5
12 - 18
37 - 55
60 - 80
19 - 26
31.5 - 37
160 - 500
6 - 15
3 - 11.5
1 - 4.8
0 - 1.3
0 - 1.25
Rouleaux
Tess 11y, FN Cross breed dog
Epistaxis for 1 year, NAD on skull Xray
Total protein ↑ 138
Albumin
Globulin
A:G ratio
Total calcium
Corrected Calcium
Urea
Creatinine
Alk Phos
ALT
Total bilirubin
Glucose
g/L
↓ 22
↑ 116
↓ 0.2
2.60
2.96
↑ 9.4
97
4
↑ 45
7
5.7
54.0 - 77.0
g/L
25.0 - 37.0
g/L
25.0 - 52.0
0.6 - 1.5
mmol/L 2.0 - 3.0
mmol/l 2.0 - 3.0
mmol/L 2.0 - 9
umol/L 40 - 106
U/L
0 - 150
U/L
0 - 25
umol/L 0 - 20
mmol/L 3.5 - 6.5
Diagnostic evaluation of liver disease
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Useful information
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Is there liver disease present likely to be
exacerbated by anaesthetic agents?
Is liver function significantly impaired?
Metabolising/clearing anaesthetic agents
Production of coagulation proteins
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Diagnostic evaluation of liver disease
Is liver disease present?
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Hepatocellular damage
ALT
Cholestasis
ALP
Hepatocyte Enzyme Distribution
Hepatic Lobule Anatomy
Cholestatic Enzyme Markers
Liver Enzymes in
Dogs and Cats
Hepatocellular ALT:
High
Low
ALP 1/2 life:
66 hours
6 hours
Steroid induced ALP:
Yes
No
Bilirubinuria:
Normal
Abnormal
Cholangiohepatitis:
Rare
Common
Transaminases & Dehydrogenases
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ALT
AST
GLDH
Measure integrity of cell membranes
Degree of increase correlates with number of
hepatocytes involved
AST increases correlate with more severe hepatocelullar
injury
Interpreting liver Enzymes
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Increased ALT
Primary hepatic disease?
Reactive hepatopathy?
Induced change?
Derived from muscle?
Interpreting liver Enzymes
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Increased ALP
Primary cholestatic problem?
Reactive hepatopathy?
Induced change?
Hepatic lipidosis?
Canine benign hepatic nodular hyperplasia?
Physiological increase?
Interpreting liver Enzymes
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Differentiating primary and secondary
hepatopathies
Clinical criteria
History, physical exam
Presence of hyperbilirubinaemia
Extent of increase in ALT
Changes in endogenous liver function
indicators
OFTEN FURTHER TESTING WILL BE
REQUIRED
Liver Function Tests
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Endogenous
Albumin, urea,
Glucose,
Cholesterol,
Coagulation
Factors, NH3
“Alarm” blood screen abnormalities in
liver disease
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Marked increases in ALT
Increased bilirubin
Reductions in urea, albumin, A:G ratio,
cholesterol
Microcytosis +/- anaemia
Further investigation of liver
abnormalities
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Review history and physical findings
Run a liver profile with FBC
Include post prandial bile acids
Consider abdominal imaging
Liver Function Tests
Darby
Total protein
Albumin
Globulin
AG ratio
Urea
Creatinine
Alk Phos
ALT
AST
GLDH
Gamma GT
Total bilirubin
Glucose
Cholesterol
Bile acids
Post bile acids
67
33
34
1.0
2.5
76
↑ 302
↑ 81
27
↑ 12
1
9
5.6
6.5
↑ 162.2
↑ 270.8
Pandy
64
33
31
1.1
4.3
87
865
46
26
7
11
5
5.8
5.7
0.9
20.8
g/L
g/L
g/L
mmol/L
umol/L
U/L
U/L
U/L
U/L
U/L
umol/L
mmol/L
mmol/L
umol/L
umol/L
Tinker, 11y, DSH, Cat
EHBDO
Total protein
Albumin
Globulin
AG ratio
Sodium
Potassium
Na:K ratio
Urea
Creatinine
Alk Phos
ALT
Total bilirubin
Bile acids
Oct
55
↓20
35
0.6
157
↓3.5
↑ 45
4.7
114
↑ 324
↑ 1798
↑ 78
↑ 388.0
June
67
154
4.3
36
11.1
138
89
64
-
g/L
g/L
g/L
mmol/L
mmol/L
mmol/L
umol/L
U/L
U/L
umol/L
umol/L
Evaluating renal function
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Urea used as a sentinel molecule for
nitrogenous waste in blood
Urea concentration is affected by
Rate of NH4 formation (protein breakdown)
Rate of hepatic conversion to urea
Rate of renal clearance
Rate of intestinal excretion
Serum urea represents a composite of these
factors
Evaluating renal function
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Urea is more sensitive but less specific for
renal function than creatinine
Hypovolaemia allows increased renal
reabsorption of urea
Protein load from GI tract is variable
GI bleeding may result in dogs in urea
increase unrelated to GFR
Causes of azotaemia
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Prerenal causes
hypovolaemia, shock, reduced cardiac
output, hypoadrenocorticism
Renal causes
congenital, inflammatory, toxic, renal
ischaemia, neoplasia
Post renal causes
urinary tract obstruction or leakage
Investigation of renal disease
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Document persistence of the azotaemia
Urinalysis
SG , dipstick, sediment (culture)
Complete the profile
Urine Refactometer
Urinary Tract Infection In Cats
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Increasingly common with age
Need not be associated with
leuconuria
Leucocyte dipstick gives false
positive
Reduced serum urea
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Reduced protein intake
Reduced protein absorbtion
Reduced hepatic synthesis of urea
Increased renal clearance of urea
Serum Electrolytes
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Sodium
Potassium
Chloride
Hypokalaemia
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Predominantly K+ is intracellular
Serum K+ is insensitive for depletion of total
body potassium
Most common in polyuric cats associated
with increased GFR
Muscle weakness, anorexia, vomiting,
cardiac arrythmias
Tabatha, 16y, DSH,FN
Weight loss, needs dental preOp check
Total protein
Albumin
Globulin
Sodium
Potassium
Na:K ratio
Total calcium
Urea
Creatinine
Alk Phos
ALT
Total bilirubin
Glucose
Total T4
66
26
40
147
3.3
45
2.28
8.7
111
↑ 291
↑ 136
5
15.5
↑ 167.0
g/L
g/L
g/L
mmol/L
mmol/L
mmol/L
mmol/L
umol/L
U/L
U/L
umol/L
mmol/L
nmol/L
54.0 - 80.0
21 - 39
15 - 57
125 - 160
3.6 - 6.0
32 - 41
2.0 - 3.0
4.0 - 12.0
80 - 180
0 - 50
0 - 40
0 - 10
3.5 - 6.6
5.0 - 50.0
Hyperkalaemia
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May accompany hypoaldosteronism in
Addison’s disease
Affected by blood pH
Increased in renal insufficiency and urinary
obstruction
Occasionally seen with severe muscle
damage
Cardiac conduction disturbances, depression,
weakness
Investigation of Electrolyte Abnormalities
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Exclude artefacts
preanalytical, analytical
Check for underlying disease
Correct pre-operatively
Hypercalcaemia
 Closely controlled element involved in
neuromuscular transmission
 Minor deviations may be significant
 Present as free, protein bound and chelated
forms in blood
 Malignant neoplasia, parathyroid neoplasia,
Addisons, CRF
Preanaesthetic blood testing
Elective blood Testing
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Sampling at consultation or vaccination
Removes time pressure for medical decision
making
Allows further testing if required ahead of
anaesthesia
Increases flexibility of test procedures
Improves client communication and
understanding
Elective blood Testing
Aims
 Screen for clinically occult disease where
early intervention is beneficial
 Provides baseline data
 Retained for future use
 To guide additional testing
 Facilitate improved perioperative
management
Elective blood testing
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Test selection is based on
History, signalment, physical findings
Screen or profile may be appropriate
incorporate appropriate additional tests
Ensure pre-analytical & analytical error is
minimised
Retain and compare data for an individual
over time