Surgery and Anesthesia Math Practice –with answers
Practice problem #1: Dog = 18 kg 6% dehydrated 15 gtt/ml set a.
What breathing system? Adult rebreathing b.
What size reservoir bag?
18 kg x 60 ml/kg = 1080ml / 1000 ml/L = 1.08 L  2 L bag c.
What will the oxygen flow rate be?
18 kg x 40 ml/kg/min = 720 ml/min / 1000 = 0.7 L/min  0.8 L/min d.
How much time left if E tank is at 1500 psi?
1500 x 0.3 = 450 L of O2 / 0.8 L/min = 562 min / 60 min/hr = 9.4 hours e.
How much acepromazine needed at 0.04 mg/kg, 10 mg/ml?
(18 kg x 0.04 mg/kg) / 10 mg/ml = 0.07 ml f.
Amount of fluid to replace before surgery?
18 kg x 0.06 x 1000 = 1, 080 ml g.
Surgical maintenance rate in ml/hr?
18 kg x 5 ml/kg/hr = 90 ml/hr
In gtt/sec?(90 ml/hr x 15 gtt/ml)/3600 sec/hr = 0.375 gt/sec x 3 = 1 gtt/3 sec
(there might be some variation here) h.
Total initial bolus amount of hetastarch if in hypovolemic shock?
18 kg x 15 ml/kg = 270 ml / 4 = 67.5 ml bolus (Range = 45-90 ml) i.
Vet wants 100 mg/ml morphine at 2 mg/kg/hr and a 40 ml/hour flow rate.
You have a
1L bag of LRS. How many mls of morphine need to be added to the fluid bag?
1000 ml / 40 ml/hr = 25 hours 18 kg x 2 mg/kg/hr = 36 mg/hr x 25 hours =
900 mg
/100 mg/ml = 9 ml morphine added to 1 L LRS

Practice problem #2: Cat = 8.5 lb 5% dehydrated 60 gtt/ml set a.
What breathing system do you need? Non-rebreathing (Jackson-Reese at
VTI) b.
What size reservoir bag?
3.86 kg x 60 ml/kg = 232 ml / 1000 ml/ L = 0.232 L  ¼ L or 0.5 L bag c.
What will the oxygen flow rate be?
3.86 kg x 250 ml/kg/min = 965 ml/min / 1000 = 0.965 L/min (1 L/min) d.
How much time left if E tank is at 700 psi?
700 psi x 0.3 = 210 L of O2 / 1 L/min = 210 minutes of O2 left (/ 60min/hr =
3.5 hours ) e.
How much ketamine needed at 4 mg/kg, 10 mg/ml?
(3.86 kg x 4 mg/kg) / 10 mg/ml = 1.54 ml f.
Amount of fluid to replace before surgery?
3.86 kg x 0.05 x 1000 = 193 ml g.
Surgical maintenance rate in ml/hr?
3.86 kg x 3 ml/kg/hr = 11.6 ml/hr
In gtt/sec? (11.6 ml/hr x 60 gtt/ml)/3600 sec/hr = 0.2 gt/sec x5 = 1 gt/q5 sec h.
Total initial bolus amount of hetastarch if in hypovolemic shock?
3.86 kg x 7.5 ml/kg = 29 ml / 4 = 7.2 ml bolus (Range = 4.8-9.65 ml) i.
Vet wants 2% lidocaine at 20 micrograms/kg/min and a 10 ml/hour flow rate. You have a 500 ml bag of Normasol. How many mls of lidocaine need to be added to the fluid bag?
500 ml / 10 ml/hr = 50 hrs 3.86 kg x 20 µg/kg/min= 77.2 µg/min /
1000 µg /mg = 0.0772 mg/min x 60 min/hr =
4.63 mg/hr x 50 hours =
231.6 mg / 20 mg/ml = 11.58 ml of lidocaine added to fluid bag

Practice problem #3: Dog = 30 lbs 7% dehydrated 15 gtt/ml set a.
What breathing system do you need? Pediatric rebreathing b.
What size reservoir bag?
13.64 kg x 60 ml/kg = 818.4 ml / 1000 ml/L = 0.82 L  1 L bag c.
What will the oxygen flow rate be?
13.64 kgx40 ml/kg/min =545.6 ml/min/1000 ml/L =0.546 L/min  0.8 L/min d.
How much time left if E tank is at 250 psi?
250 psi x 0.3 = 75 L of O2 / 0.8 L/min = 93.75 mins / 60 min/hr = 1 1/2 hours e.
How much propofol needed at 1 mg/lb, 100mg /10 ml?
(30 lb x 1 mg/lb) / 10mg/ml = 3 ml f.
Amount of fluid to replace before surgery?
13.64 kg x 0.07 x 1000 = 954.8 ml g.
Surgical maintenance rate in ml/hr?
13.64 kg x 5 ml/kg/hr = 68 ml/hr
In gtt/sec? (68 ml/hr x 15 gtt/ml) / 3600 sec = 0.28 gt/sec x 4 = 1 gt/ q4 sec h.
Total initial bolus amount of hetastarch if in hypovolemic shock?
13.64 kg x 15 ml/kg = 204.6 ml /4 = 51 ml bolus (Range = 34-68.2 ml) i.
Vet wants 40 mg/ml dopamine at 0.3 mg/kg/hr and a 50 ml/hour flow rate.
You have a 1L bag of Plasmalyte. How many mls of dopamine need to be added to the fluid bag?
1000 ml / 50 ml/hr = 20 hours 13.64 kg x 0.3 mg/kg/hr = 4.1 mg/hr x 20 hrs
= 82 mg / 40 mg/ml = 2.05 ml dopamine added to 1 L bag