Electrolytes by case examples. Graham Bilbrough, European Medical Affairs Manager

Transcription

1 Electrolytes by case examples Graham Bilbrough, European Medical Affairs Manager 1

2 Acid-bases disturbances Generally result from one of the following: 1. damage to an organ such as the kidneys or lungs that are normally responsible for acid-base balance 2. disease which causes abnormally increased production of metabolic acids such that the buffer system is overwhelmed 3. medical intervention such as mechanical ventilation and some drugs 2

3 Acid-bases disturbances Primarily affects the partial pressure of carbon dioxide respiratory disturbance Primarily affects the concentration of bicarbonate metabolic disturbance 3

4 Abnormal ph Normal ph for dog blood is 7.35 to

5 Abnormal ph Normal ph for dog blood is 7.35 to 7.45 Acidaemia if blood ph <7.3 acidosis is the condition causing ph 5

6 Abnormal ph Normal ph for dog blood is 7.35 to 7.45 Alkalaemia if blood ph > 7.5 Alkalosis is the condition causing ph 6

7 -osis versus -aemia ph PvCO2 HCO mmHg 12mmol/L Acidosis is not the same thing as acidaemia 7

8 Metabolic acidosis The primary disturbance is associated with decreased bicarbonate This usually occurs either as a result of increased consumption or increased loss 8

9 Metabolic acidosis mmol/l Na + Cl - K + Ca 2+ HCO 3- precursor Hartmann s Yes 0.9% Saline No 9

10 Metabolic alkalosis Primary disturbance is raised bicarbonate Usually a result of abnormal loss of hydrogen ions from the body 10

11 Our first example Vomiting and diarrhoea Requires IVFT 11

12 v indicates a venous sample ph PvO2 PvCO2 HCO3- Na+ Cl- K mmHg 48mmHg 36mmol/L 149mmol/L 89mmol/L 3.21mmol/L high high normal low low Vomiting and diarrhoea Requires IVFT 12

13 How did the BGA help? ph PvO2 PvCO2 HCO3- Na+ Cl- K mmHg 48mmHg 36mmol/L 159mmol/L 89mmol/L 3.21mmol/L high high normal low low Vomit: loss of acid, chloride and potassium Diarrhoea: loss of bicarbonate Use IVFT to correct electrolytes including bicarbonate 13

14 mmol/l Na + Cl - K + Ca 2+ HCO 3- precursor Hartmann s Yes 0.9% Saline No ph PvO2 PvCO2 HCO3- Na+ Cl- K mmHg 48mmHg 36mmol/L 159mmol/L 89mmol/L 3.21mmol/L high high normal low low In this case the loss of acid, chloride and potassium was significant 0.9% saline (with extra K + ) would be a better choice than Hartmann s 14

15 11 year-old male JRT Referring vet had performed a cystotomy to remove a bladder stone Dog now lethargic, vomiting Straining to urinate, passing small amounts Dehydrated, painful abdomen Paracentesis yielded free peritoneal fluid 15

16 Likely to have a respiratory alkalosis as normal blood ph Venous Hct TP ph ( ) Sodium ( ) Potassium ( ) Chloride ( ) HCO 3 - (22 24) Glucose Day 1 52% 8.6g/dL mmol/L 6.0mmol/L 90mmol/L 16 mmol/l high high 14.2mmol/L low high low low Dehydration and haemoconcentration Uroabdomen: urine normally contains much lower sodium and chloride and higher potassium than ECF Metabolic acidosis with high anion gap: accumulation of acids normally lost via urine Probably due to stress 16

17 Hct TP ph (venous) Sodium Potassium Chloride HCO3- Glucose Day 1 52% 8.6g/dL mmol/L 6.0mmol/L 90mmol/L 16 mmol/l 14.2mmol/L +8 hours changed a bit too quickly getting a bit low could be better 17

18 Day 1 +8 hours +24 hours Hct 52% TP 8.6g/dL ph (venous) 7.34 Sodium 145mmol/L Potassium 6.0mmol/L Chloride 90mmol/L HCO3-16 mmol/l Glucose 14.2mmol/L 18

19 H05: Snickers 10 yr old Female neutered Mixed Breed Dog Presented with primary complaint of vomiting 19

20 H05: Snickers urea 332 mg/dl ( ) creat 10.3 mg/dl ( ) phos 28.9 mg/dl ( ) urine SG Na+ 151 mmol/l ( ) K+ 5.3 mmol/l ( ) Cl- 101 mmol/l ( ) bicarb 19 mmol/l ( ) An Gap 37 mmol/l ( 9-18 ) High High Low Normal High AG

21 H05: Snickers Renal azotaemia Decreased GFR (urea, creatinine and phosphorus) Non-concentrated urine bicarbinate normal initial interpretation suggests no metabolic disturbance The Anion Gap is increased increased unmeasured anions (organic acids) indicating a metabolic acidosis most likely associated with uraemic acids not being filtered Na + minus Cl - Cl - low relative to Na + suggesting metabolic alkalosis due to HCl loss with vomiting Mixed Metabolic Acidosis and Alkalosis

22 Case 4 9-year old male, mixed breed dog Previously, PU/PD and weight loss Now presents collapsed 22

23 Case 4 ph (venous) PvCO 2 (32 49) Sodium ( ) Potassium ( ) HCO - 3 (22 24) Glucose ( ) mmhg mmol/l 4.3 mmol/l 14.3 mmol/l 32mmol/L 9-year old male, mixed breed dog Previously, PU/PD and weight loss Now presents collapsed 23

24 Case 4 ph (venous) PvCO 2 (32 49) Sodium ( ) Potassium ( ) HCO - 3 (22 24) Glucose ( ) mmhg mmol/l 4.3 mmol/l 14.3 mmol/l 32mmol/L 9-year old male, mixed breed dog Previously, PU/PD and weight loss Now presents collapsed Urine analysis Dipstick: 4+ ketones, 4+ glucose, no other abnormalities 24

25 Case 4 ph (venous) PvCO 2 (32 49) Sodium ( ) Potassium ( ) HCO 3 - (22 24) Glucose ( ) mmhg mmol/l hyponatraemia 4.3 mmol/l 14.3 mmol/l 32mmol/L acidaemia metabolic acidosis 9-year old male, mixed breed dog Previously, PU/PD and weight loss Now presents collapsed hyperglycaemia Urine analysis Dipstick: 4+ ketones, 4+ glucose, no other abnormalities ketonuria glucosuria 25

26 Any more tests? Urea and creatinine, phosphate assess renal function Bile acid stimulation test Spec cpl Look for focus of infection or inflammation that may have precipitated this crisis FBC, urine culture, blood culture, radiography 26

27 After insulin and IVFT ph (venous) PvCO 2 (32 49) Sodium ( ) Potassium ( ) HCO 3 - (22 24) Glucose ( ) mmol/L 7.22 Improved resp. compensation 27.1 mmhg mmol/l Hypokalaemia 4.3 mmol/l 14.3 mmol/l Dropped markedly 21.6 Redistribution of the K+ has unmasked hypokalaemia; but what about phosphorus? 27

28 6 mo M mix breed dog Buddy Found by owner recumbent and vomiting O/E: 5% dehydrated injected mucous membranes temp = 37.1 o C semi-comatose 28

29 6 mo M mix breed dog Buddy VetStat results (venous, room air): ph ( ) HCO 3 3 meq/l (20 29) pco 2 32 mmhg (32 49) Na 154 meq/l ( ) K 6.5 meq/l ( ) Cl 111 meq/l ( ) AG 47 (12 24) ica mmol/l ( ) 29

30 6 mo M mix breed dog Buddy VetStat results: ph ( ) HCO 3 3 meq/l (20 29) pco 2 32 mmhg (32 49) Step 1: acidaemia Step 2: met. acidosis Step 3: normal Na 154 meq/l ( ) K 6.5 meq/l ( ) Step 4: high anion gap Cl 111 meq/l ( ) AG 47 (12 24) ica mmol/l ( ) Interpretation: high anion gap metabolic acidosis 30

31 6 mo M mix breed dog Buddy Other test results: urea 42 mg/dl (9 31) creat 2.1 mg/dl ( ) glu 136 mg/dl (80 120) Urine S.G Urine glu trace Urine ket negative Calcium oxalate monohydrate crystals Very occasionally present in normal dogs 31

32 6 mo M mix breed dog Buddy Very high anion gap metabolic acidosis + hypocalcaemia = think??? Calcium binding to oxalic acid in the renal tubules leads to calcium oxalate crystalluria and increased renal loss of calcium 32

33 3 yr F Labrador retriever Xena 2 weeks of vomiting food and water, gradually decreasing appetite and lethargy O/E: 7% dehydrated lethargic 33

34 3 yr F Labrador retriever Xena VetStat results (venous, room air): ph ( ) HCO meq/l (20 29) pco mmhg (32 49) Na 119 meq/l ( ) K 2.7 meq/l ( ) Cl 69 meq/l ( ) Step 1: alkalaemia Step 2: metabolic alkalosis Step 3: normal Step 4: normal anion gap, increased Na-Cl difference AG 22 (12 24) Interpretation: Hypochloraemic metabolic alkalosis 34

35 3 yr F Labrador retriever Xena Other test results: All other bloodwork and urine WNL What should your next test be? 35

36 3 yr F Labrador retriever Xena Abdominal radiographs: Gaseous distention of the small intestine in the cranial abdomen, suspicious of a foreign body. 36

37 3 yr F Labrador retriever Xena Treatment: First stabilize patient before taking to surgery IV 0.9% NaCl fluids with KCl supplementation MUST give chloride in excess of sodium for alkalosis to be corrected Corn cob fragment found in proximal small intestine 37

38 1 yr M mix breed dog Duke RTA 45 minutes prior to presentation to clinic O/E: weak femoral pulses temp = 39.6 o C HR = 180 bpm RR = panting with shallow breaths bleeding from nostrils 38

39 1 yr M mix breed dog Duke VetStat results (arterial, room air): ph ( ) HCO 3 20 meq/l (20 29) pco 2 65 mmhg (36 44) po 2 87 mmhg (90 100) Na 152 meq/l ( ) K 3.6 meq/l ( ) Cl 109 meq/l ( ) AG 26.6 (12 24) 39

40 1 yr M mix breed dog Duke VetStat results (arterial, room air): ph ( ) HCO 3 20 meq/l (20 29) pco 2 65 mmhg (36 44) Step 1: acidaemia Step 2: normal Step 3: respiratory acidosis po 2 87 mmhg (90 100) Na 152 meq/l ( ) K 3.6 meq/l ( ) Cl 109 meq/l ( ) Interpretation: primary respiratory acidosis AG 26.6 (12 24) 40

41 Oxygen-haemoglobin dissociation curve Percentage of haemoglobin molecules carrying oxygen Partial pressure of oxygen dissolved in the arterial blood 41

42 Understanding oxygen content PaO 2 determines what percentage of the haemoglobin molecules carry oxygen Think of oxygen as being in two states : 1) dissolved in the plasma 2) in association with haemoglobin Anaemia does not affect PaO 2 42

43 1 yr M mix breed dog Duke Treatment: Thoracocentesis pneumothorax IV Hartmann s Tapping this dog s chest results in PaO 2 and PaCO 2 within normal limits 43

44 10 yr MN German Shepherd Thor Acute onset of non-productive retching and distended abdomen O/E: pale mucous membranes prolonged capillary refill time distended and tympanic abdomen poor femoral pulses tachycardia panting 44

45 10 yr MN German Shepherd VetStat results: Thor ph ( ) HCO 3 8 meq/l (20 29) pco 2 55 mmhg (32 49) Na 152 meq/l ( ) K 4.5 meq/l ( ) Cl 113 meq/l ( ) AG 36 (12 24) 45

46 10 yr MN German Shepherd VetStat results: Thor ph ( ) Step 1: acidaemia HCO 3 8 meq/l (20 29) Step 2: metabolic acidosis pco 2 55 mmhg (32 49) Step 3: respiratory acidosis Na 152 meq/l ( ) K 4.5 meq/l ( ) Step 4: high anion gap Cl 113 meq/l ( ) AG 36 (12 24) Interpretation: high anion gap acidosis & respiratory acidosis 46

47 10 yr MN German Shepherd Thor 47

48 10 yr MN German Shepherd Treatment: Thor Bolus IV replacement fluid (e.g. Hartmann s) NO NaHCO 3 because of high PaCO 2 THEN pass stomach tube 48

49 8 yr FS Great Dane Thelma Acute onset of nonproductive retching and distended abdomen PE: pale mucous membranes prolonged capillary refill time distended and tympanic abdomen poor femoral pulses tachycardia panting 49

50 8 yr FS Great Dane Thelma VetStat results: ph ( ) HCO 3 34 meq/l (20 29) pco 2 29 mmhg (32 49) Na 136 meq/l ( ) K 4.5 meq/l ( ) Cl 84 meq/l ( ) AG 23 (12 24) 50

51 8 yr FS Great Dane Thelma VetStat results: ph ( ) HCO 3 34 meq/l (20 29) pco 2 29 mmhg (32 49) Step 1: alkalaemia Step 2: metabolic alkalosis Step 3: respiratory alkalosis Na 136 meq/l ( ) K 4.5 meq/l ( ) Cl 84 meq/l ( ) AG 23 (12 24) Step 4: normal anion gap, but increased Na-Cl difference Interpretation: hypochloraemic metabolic alkalosis and respiratory alkalosis 51

52 8 yr FS Great Dane Thelma 52

53 8 yr FS Great Dane Thelma Treatment Bolus IV 0.9% NaCl fluids (with KCl added later) THEN pass stomach tube 53

54 Any questions? 54