Page 180 - Basic Monitoring in Canine and Feline Emergency Patients

Table 8.6. Serial sodium, blood urea nitrogen, and creatinine values and the fluid interventions taken in response to
blood values in an elderly cat with renal failure. Footnotes to the table provide further rationale for the various fluid rates
VetBooks.ir Time BUN (mg/dL) Creatinine (mg/dL) Normal: 148–157 change (mEq/L/h) Fluid type and rate
selected.
Rate of Na
Na (mEq/L)
(hours) Normal: 15–35
Normal: 0.9–2.3
0 294 12.6 207 – 0.9% NaCl at 215 mL/kg/day
12 198 −0.7 0.9% NaCl at 165 mL/kg/day a
19 236 9.7 196 −0.28 0.9% NaCl at 165 mL/kg/day
22 193 −1 0.9% NaCl at 165 mL/kg/day
26 186 −1.75 0.9% NaCl at 165 mL/kg/day
37 125 5.5 188 +0.18 0.9% NaCl at 120 mL/kg/day b
43 186 −0.33 0.9% NaCl at 120 mL/kg/day
49 183 −0.5 0.9% NaCl at 120 mL/kg/day
61 83 4.1 180 −0.25 0.9% NaCl at 100 mL/kg/day b
72 173 −0.63 0.9% NaCl at 100 mL/kg/day
84 67 2.6 165 −0.66 0.9% NaCl at 100 mL/kg/day
92 66 2.6 163 −0.25 0.9% NaCl at 60 mL/kg/day c
101 63 2.6 161 −0.22 0.9% NaCl at 60 mL/kg/day
108 59 2.4 160 −0.14 0.9% NaCl at 40 mL/kg/day
113 60 2.4 156 −0.8 0.9% NaCl at 40 mL/kg/day
Discharged later that day to
owner

BUN, blood urea nitrogen; 0.9% NaCl (also known as ‘normal saline’) is an isotonic crystalloid fluid with a sodium content of 154 mEq/L.
a At approximately 12 hours of hospitalization, Norah’s dehydration was improved based on her physical examination findings (weight
was 1.9 kg). Her water deficit was calculated as shown in Table 8.5. In Norah’s case, we did not multiply by the 0.6 factor.
Water deficit = Weight (kg) × ([Na] current /[Na] normal – 1)
= 1.9 kg × (198/145 –1) = 694mL
Since it was likely a chronic hypernatremia (and Norah had a heart murmur), we wanted to replace this sodium deficit over 72 at the
fastest. This would equate to ~10 mL/h in addition to her maintenance fluid rate (40 mL/kg/day= 3 mL/h) or 13 mL/h (165 mL/kg/day)
total.
b At approximately 36 hours of hospitalization, Norah’s Na, BUN, and creatinine values were dropping consistently and her dehydration
seemed to be completely resolved. Her heart murmur was persistent but unchanged. She was eating and drinking water readily. Due to
concerns about fluid overload with continued high IV fluid rates and the fact that she was definitely taking in large amounts of water per
day in her canned food intake and water intake in addition to her fluids, her IV fluid rate was decreased. Reducing her fluid rate to first
120 mL/kg/day and then to 100 mL/kg/day at 61 hours of hospitalization were somewhat arbitrary decisions to reduce her fluid therapy
~20–25% each day but were supported by the fact that her sodium continued to decrease. She was also kept on 0.9% NaCl since her
sodium was continuing to decrease on that fluid type at a reasonable rate (overall 0.5-1 mEq/h). If her sodium values had not continued
to decrease, her fluid type would have been changed to lactated Ringer’s solution or plasmalyte, both of which contain less sodium per
mL than 0.9% NaCl or potentially even a hypotonic fluid such as 0.45% NaCl or 5% dextrose in water. In addition, if she had displayed
any hyperchloremia from the 0.9% NaCl, her fluid type would have been changed to a fluid with less chloride content.
c Between 84 and 92 hours of hospitalization, Norah’s Na, BUN, and creatinine had reached a plateau. Therefore, fluid weaning was
continued by first reducing the fluid rate by approximately one-third and then, when Na, BUN, and creatinine remained at a plateau,
reducing her to maintenance fluids (40 mL/kg/day) at 108 hours of hospitalization prior to discharge.

172 E.J. Thomovsky