Lit Fluids, Electrolytes, Acid-Base

Question 1

How did the use of adjusted Ca (aCa) compare to tCa for detecting ionized hypoCa in hypoalbuminemic dogs w/o hyperphosphatemia?
Discuss in terms of Sn, Sp, PPV & accuracy.

Answer 1

De Witte JVIM 2021

ACa had similar-slightly lower Sn (92.3%) vs tCa (Sn 100%) but much higher Sp (94.8%) vs tCa (Sp only 57.8%).
NPV similar (100% tCa; 99.6% ACa), overall poor PPV but aCa higher (48.2% vs 11% for tCa).

—> Normal aCa indicates that moderate ionized hypocalcemia was unlikely (will miss 8% cases, in this scenario a normal tCa is more useful to r/o ionized hypoCa).
But low aCa is useful as indicates ionized hypoCa is very likely in hypoalb non-hyperphos dogs (whereas low tCa is only associated with true ionized hypoCa in ~57.8% cases).

Question 2

Which form of lactate is specific to bacterial origin?

Answer 2

Venn JVIM 2020
D-lactate
Stereoisomer of L-lactate
Byproduct of bacterial metabolism; produced during anaerobic fermentation of CHO in the GIT.
Can’t be measured by current POC tests.

Increased blood D-lactate (humans, reported in cats) - ataxia, mental depression, metabolic acidosis

Question 3

a) Hyperosmolar agents: name 2 main ones used in vet medicine.

b) Which agent is gold standard for tratment of intracranial hypertension in TBI patients?

Differences in effects on electrolytes & acid-base between use of these 2 agents in dogs with ICH?

Answer 3

Hoehne JVIM 2020
a) Mannitol & hypertonic saline (HTS)
b) Mannitol

c) Mannitol - more pronounced & sustained diuresis –> increased risk of dehydration & hypovolemia. Caused transient decreases in plasma Na+ & Cl- [ ] (at 5min post-admin, resolved by 60min).

HTS - caused sustained increases in plasma Na+ & Cl- [ ] (120min post-admin).

No sig diff in acid-base variables between HTS & MAN.

Question 4

1. What were the optimal tCa concentration thresholds identified in non-hyperphos vs hyperphos dogs for the detection of ionized hyperCa?
   What were the respective predictive values and/or sensitivities & specificities for the stated thresholds?
2. Prevalence of ionized hyperCa & hypoCa in non-hyperphos vs hyperphos dogs?

Answer 4

Groth JVIM 2020

1. Non-hyperphos dogs: optimal tCa threshold of 12.0mg/dL. High tCa had PPV (93%) for detecting high iCa, but poor sensitivity (52%). So high tCa is strongly predictive of ionized hyperCa, but normal tCa doesn’t rule out high iCa (should still test if clinical suspicion).
   Hyperphos dogs - optimal tCa threshold not established. Renal disease causes discordance of tCa & iCa due to PO4 complexes.
2. Non-hyperphos dogs had higher prevalence of ionized hyperCa (7% vs 3%) & lower prevalence of ionized hypoCa (23 vs 62%) vs hyperphos dogs.

Question 5

a) Most common acid-base disorder in dogs with canine parvoviral enteritis (CPVE)?

b) What were the major contributors to AB disorders in CPVE dogs?

Answer 5

Burchell JVIM 2020
a) Mixed AB disorder: metabolic acidosis + concurrent respiratory alkalosis

b)
Hyponatremia
Hypochloremia
Atot acidosis (= total concentration of nonvolatile weak acids i.e. proteins, phosphate) due to elevated globulins & increased unmeasured anions (UA).

Question 6

What electrolyte changes may be expected with prolonged (20-28hrs) refrigerated storage & clotting of plasma/serum samples in cats?

Answer 6

Domenegato JAVMA 2021
Artifactual increase in K+ (beware pseudohyperk) - especially if stored in no-additive tube (serum).

Question 7

What were the effects of a mannitol bolus on UOP, GFR & Fe of Na/Urea compared to D5W? Did a CRI improve its efficacy?

Answer 7

Segev JVIM 2019
Mannitol bolus had minimal effect on UOP & GFR (similar degree cf control fluid D5W), and resulted in transient increase in FE of Na & urea in healthy dogs.
Mannitol CRI did not sustain effects on FE of Na & urea excretion in dogs with normal renal function, as serum concentrations were not maintained.

Question 8

What was the sensitivity & specificity of predicted ionized Ca (based on serum biochemistry & TT4) to predict HYPER & HYPOcalcemia in cats?
How did this compare to tCa?

Answer 8

Hodgson JVIM 2019
(Note similar dog paper - Danner JVIM 2017)

piCa:
- For HYPERCa: high Sp (99.8%) but poor Sn (30.4%) - lots of false negatives
- For HYPOCa: similar - high Sp (81.6%) but poor Sn (57.6%).

Overall piCa is useful to confirm suspected hyperCa in cats + screen for hyper/hypoCa in cats.
Diagnostic performance comparable to tCa.

Question 9

What was the Sn & Sp of predicted iCa (piCa) based on serum biochemistry data, for detection of HYPER & HYPOcalcemia in dogs?
How did this compare to measured iCa (miCa), tCa & corrected tCa?

Answer 9

Danner JVIM 2017
(Note similar cat paper - Hodgson JVIM 2019)

piCa:
- For HYPERCa: 64% Sn, but higher Sp (99.6%) vs tCa & corrected tCa. High PPV (90%) & NPV (98%) for piCa.
- For HYPOCa: higher Sn (21.8%), similar Sp(98.4%) as tCa. Moderate PPV (70.8%) & moderate-high NPV (87.7%) for piCa.

—> piCa correlated better with miCa, overall had higher diagnostic accuracy than tCa & corrected tCa to assess calcium disorders in dogs when miCa is unavailable (though less sig for hyperCa).

Question 10

Are predictive calcium calculations to estimate ionised hyper or hypoCa sensitive or specific?

Answer 10

Hodgson JVIM 2019
Danner JVIM 2017

Both papers showed high Sp but <80% sensitivity for diagnosing hypo or hyperCa.

Question 11

What % of BW is total body water?

What % of daily water turnover can occur with exercise?

Answer 11

Stephens-Brown JVIM 2018

60% in minimally conditioned Labs, 74% in highly conditioned Labs.

Up to 45%

Question 12

Is blood lactate concentration useful as a prognostic indicator for survival in hypotensive cats in the ICU?

Answer 12

Shea JAMA 2017
Yes, hypolactatemia (lactate <2.5) associated with decreased survival to discharge (69% of non-survivors vs 31% that were normolactatemic). Also decreased 5-day survival rates (17% vs 57% for normal lactate).