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Beyond Pre-Anaesthetic Testing. Nick Carmichael BVM&S, BSc VetSci(Hons), Diploma VCS(Syd), Diploma RCPath, Diplomate ECVCP, MRCVS. Aims of pre-anaesthetic testing. Screen for the presence of intercurrent disease Allow adjustments in anaesthetics/ drugs used to be made

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beyond pre anaesthetic testing

Beyond Pre-Anaesthetic Testing

Nick Carmichael

BVM&S, BSc VetSci(Hons), Diploma VCS(Syd),

Diploma RCPath, Diplomate ECVCP, MRCVS

aims of pre anaesthetic testing
Aims of pre-anaesthetic testing
  • 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
Benefits of pre-anaesthetic testing
  • Safer anaesthesia
  • Appropriate perioperative management
  • Early identification of clinically silent problems
drawbacks of pre anaesthetic testing
Drawbacks of pre-anaesthetic testing
  • Cost benefit analysis
  • “False positive” screening test results
  • Inappropriate labelling of cases
  • “False negative” screening test results
  • Decision time pressure
cost benefit analysis
Cost Benefit Analysis
  • 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
What are the major anaesthetic risks?
  • Excessive anaesthetic administered
  • Hypotension
  • Cardiac rhythm abnormalities/ arrest
  • Ventilation/perfusion imbalances

Would pre- anaesthetic bloods predict / ameliorate these?

pre anaesthetic testing requirements
Pre-anaesthetic testing requirements
  • Sensitive
  • Specific
  • Relate to organ function
  • Low cost
screens vs profiles
Diagnostic Profiles

Contains grouped tests related to organ function

Tests provide complimentary information

Tests included relate to a presenting sign

Assists in localisation/ narrowing of the DDx

Screens

Contains a single test per organ

Single most sensitive test included

Test array is fixed

Provides yes/no information regarding normality

SCREENS VS PROFILES
pre anaesthetic screen components
Pre-anaesthetic screen components
  • FBC
  • Total protein
  • Urea
  • ALT
  • ALP
  • Glucose
  • (Electrolytes)
tiny boxer male 3yr
Tiny, boxer male 3yr

Total protein 68 g/L (54.0 -77.0 )

Urea 3.3 mmol/L (2.0 -9.0 )

Creatinine 91 umol/L (40.0 -106.0)

Alk Phos * 707 U/L High (0.0 -150.0 )

ALT * 233 U/L High (0.0 -25.0 )

Total bilirubin 6 umol/L (0.0 -20.0 )

Glucose 5.3 mmol/L (3.5-6.5)

tiny boxer male 3yr1
Tiny, boxer male 3yr

RBC * 2.83 x10^12/L Low (5.0 -8.5 )

Hb * 6.9 g/dl Low (12.0 -18.0 )

HCT *21.9 % Low (37.0 -55.0 )

MCV 77.0 fl (60.0 -80.0 )

MCH 24.3 pg (19.0 -26.0 )

MCHC 31.5 g/dl (31.5 -37.0 )

Platelets * 66 x10^9/L Low (160 -500 )

WBC * 1.89 x10^9/L Low (6.0 -15.0 )

Neutrophils * 39% 0.74 x10^9/L Low (3.0 -11.5 )

Lymphocytes 57% 1.08 x10^9/L (1.0 -4.8 )

Monocytes 3% 0.06 x10^9/L (0.0 -1.3 )

Eosinophils 1% 0.02 x10^9/L (0.0 -1.25 )

fbc abnormalities
FBC abnormalities

White Cells : Atypical Lymphocytes

fbc abnormalities1
FBC abnormalities

Red Cells: Schistocytes

fbc abnormalities2
FBC abnormalities

Platelets: Thrombocytopenia & Platelet Clumps

daisy ckcs fn 2yrs
Daisy, CKCS FN 2yrs

Total protein ↑86 68 g/L

Albumin 32 32 g/L

Globulin ↑54 36 g/L

Total calcium 2.86 2.70 mmol/L

Phosphate ↑3.51 2.10 mmol/L

Urea ↑14.9 ↑13.3 mmol/L

Creatinine 101 ↑152 umol/L

Alk Phos ↑578 ↑455 U/L

GLDH ↑87 12 U/L

Gamma GT 25 25 U/L

Total bilirubin ↑30 6 umol/L

Bile acids ↑26.7 9.7 umol/L

Glucose 6.4 5.6 mmol/L

total protein
Total Protein
  • Normal TP 50:50 alb:glob Normal TP, 10:90 AG
hypoalbuminaemia
Hypoalbuminaemia
  • SignificanceAnaesthesiaWound healingeffusion formation
  • CausesIncreased lossReduced productionEffusion formation
hypoalbuminaemia1
Hypoalbuminaemia

Investigation

  • Evidence of effusion /exudation
  • Evidence of increased renal/ GI loss?
  • Evidence of inflammation?
  • Evidence of impaired hepatic function?
hyperglobulinaemia
Hyperglobulinaemia

Associated with

  • Inflammation
  • Viral infection
  • Neoplasia
severe hyperglobulinaemia
Severe Hyperglobulinaemia

Effects

  • Impaired primary haemostasis
  • Blood hyperviscosity

Differentials

  • Feline viral infectionsFIV, FIP, Felv
  • B-cell derived neoplasiaLymphoma, myeloma, (plasmacytoma)
  • Non indigenous infectionsLeishmania, Ehrlichia, Borrelia
hyperglobulinaemia1
Hyperglobulinaemia

Diagnostic evaluation

  • 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
Tess 11y, FN Cross breed dogEpistaxis for 1 year, NAD on skull Xray

RBC ↓ 3.67 x10^12/L 5 - 8.5

Hb ↓ 9.0 g/dl 12 - 18

HCT ↓ 27.8 % 37 - 55

MCV 76.0 fl 60 - 80

MCH 24.5 pg 19 - 26

MCHC 32.4 g/dl 31.5 - 37

Platelets 357 x10^9/L 160 - 500

WBC 8.46 x10^9/L 6 - 15

Neutrophils 77% 6.5x10^9/L 3 - 11.5

Lymphocytes 20% 1.6x10^9/L 1 - 4.8

Monocytes 0.% 0.0x10^9/L 0 - 1.3

Eosinophils 3% 0.2x10^9/L 0 - 1.25

tess 11y fn cross breed dog epistaxis for 1 year nad on skull xray1
Tess 11y, FN Cross breed dogEpistaxis for 1 year, NAD on skull Xray

Total protein ↑ 138 g/L 54.0 - 77.0

Albumin ↓ 22 g/L 25.0 - 37.0

Globulin ↑ 116 g/L 25.0 - 52.0

A:G ratio ↓ 0.2 0.6 - 1.5

Total calcium 2.60 mmol/L 2.0 - 3.0

Corrected Calcium 2.96 mmol/l 2.0 - 3.0

Urea ↑ 9.4 mmol/L 2.0 - 9

Creatinine 97 umol/L 40 - 106

Alk Phos 4 U/L 0 - 150

ALT ↑ 45 U/L 0 - 25

Total bilirubin 7 umol/L 0 - 20

Glucose 5.7 mmol/L 3.5 - 6.5

diagnostic evaluation of liver disease
Diagnostic evaluation of liver disease
  • Useful information
  • Is there liver disease present likely to be exacerbated by anaesthetic agents?
  • Is liver function significantly impaired?Metabolising/clearing anaesthetic agentsProduction of coagulation proteins
diagnostic evaluation of liver disease1
Diagnostic evaluation of liver disease

Is liver disease present?

  • Hepatocellular damageALT
  • CholestasisALP
slide32

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
Transaminases & Dehydrogenases
  • 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
Interpreting liver Enzymes
  • Increased ALT
  • Primary hepatic disease?
  • Reactive hepatopathy?
  • Induced change?Derived from muscle?
interpreting liver enzymes1
Interpreting liver Enzymes
  • Increased ALP
  • Primary cholestatic problem?
  • Reactive hepatopathy?
  • Induced change?
  • Hepatic lipidosis?
  • Canine benign hepatic nodular hyperplasia?
  • Physiological increase?
interpreting liver enzymes2
Interpreting liver Enzymes
  • Differentiating primary and secondary hepatopathies
  • Clinical criteriaHistory, 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
Liver Function Tests
  • Endogenous
  • Albumin, urea, Glucose, Cholesterol, Coagulation Factors, NH3
alarm blood screen abnormalities in liver disease
“Alarm” blood screen abnormalities in liver disease
  • Marked increases in ALT
  • Increased bilirubin
  • Reductions in urea, albumin, A:G ratio, cholesterol
  • Microcytosis +/- anaemia
further investigation of liver abnormalities
Further investigation of liver abnormalities
  • Review history and physical findings
  • Run a liver profile with FBC
  • Include post prandial bile acids
  • Consider abdominal imaging
darby pandy
Darby Pandy

Total protein 67 64 g/L

Albumin 33 33 g/L

Globulin 34 31 g/L

AG ratio 1.0 1.1

Urea 2.5 4.3 mmol/L

Creatinine 76 87 umol/L

Alk Phos ↑ 302 865 U/L

ALT ↑ 81 46 U/L

AST 27 26 U/L

GLDH ↑ 12 7 U/L

Gamma GT 1 11 U/L

Total bilirubin 9 5 umol/L

Glucose 5.6 5.8 mmol/L

Cholesterol 6.5 5.7 mmol/L

Bile acids ↑ 162.2 0.9 umol/L

Post bile acids ↑ 270.8 20.8 umol/L

tinker 11y dsh cat ehbdo
Tinker, 11y, DSH, CatEHBDO

Oct June

Total protein 55 67 g/L

Albumin ↓20 - g/L

Globulin 35 - g/L

AG ratio 0.6 -

Sodium 157 154 mmol/L

Potassium ↓3.5 4.3 mmol/L

Na:K ratio ↑ 45 36

Urea 4.7 11.1 mmol/L

Creatinine 114 138 umol/L

Alk Phos ↑ 324 89 U/L

ALT ↑ 1798 64 U/L

Total bilirubin ↑ 78 - umol/L

Bile acids ↑ 388.0 - umol/L

evaluating renal function
Evaluating renal function
  • Urea used as a sentinel molecule for nitrogenous waste in blood
  • Urea concentration is affected byRate of NH4 formation (protein breakdown)Rate of hepatic conversion to ureaRate of renal clearance Rate of intestinal excretion
  • Serum urea represents a composite of these factors
evaluating renal function1
Evaluating renal function
  • 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
Causes of azotaemia
  • Prerenal causeshypovolaemia, shock, reduced cardiac output, hypoadrenocorticism
  • Renal causescongenital, inflammatory, toxic, renal ischaemia, neoplasia
  • Post renal causesurinary tract obstruction or leakage
investigation of renal disease
Investigation of renal disease
  • Document persistence of the azotaemia
  • Urinalysis SG , dipstick, sediment (culture)
  • Complete the profile
urinary tract infection in cats
Increasingly common with age

Need not be associated with leuconuria

Leucocyte dipstick gives false positive

Urinary Tract Infection In Cats
reduced serum urea
Reduced serum urea
  • Reduced protein intake
  • Reduced protein absorbtion
  • Reduced hepatic synthesis of urea
  • Increased renal clearance of urea
serum electrolytes
Serum Electrolytes
  • Sodium
  • Potassium
  • Chloride
hypokalaemia
Hypokalaemia
  • 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
Tabatha, 16y, DSH,FNWeight loss, needs dental preOp check

Total protein 66 g/L 54.0 - 80.0

Albumin 26 g/L 21 - 39

Globulin 40 g/L 15 - 57

Sodium 147 mmol/L 125 - 160

Potassium 3.3 mmol/L 3.6 - 6.0

Na:K ratio 45 32 - 41

Total calcium 2.28 mmol/L 2.0 - 3.0

Urea 8.7 mmol/L 4.0 - 12.0

Creatinine 111 umol/L 80 - 180

Alk Phos ↑ 291 U/L 0 - 50

ALT ↑ 136 U/L 0 - 40

Total bilirubin 5 umol/L 0 - 10

Glucose 15.5 mmol/L 3.5 - 6.6

Total T4 ↑ 167.0 nmol/L 5.0 - 50.0

hyperkalaemia
Hyperkalaemia
  • 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
Investigation of Electrolyte Abnormalities
  • Exclude artefactspreanalytical, analytical
  • Check for underlying disease
  • Correct pre-operatively
hypercalcaemia
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
elective blood testing
Elective blood Testing
  • 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 testing1
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 testing2
Elective blood testing
  • Test selection is based onHistory, signalment, physical findings
  • Screen or profile may be appropriateincorporate appropriate additional tests
  • Ensure pre-analytical & analytical error is minimised
  • Retain and compare data for an individual over time