Normal Blood Pressure Values

1.  Systolic 100–160 mm Hg

2.  Diastolic 60–100 mm Hg

3.  MAP: 80–120 mm Hg

Hypotension Occurs When MAP Is Less Than 60 mm Hg

MAP = CO × SVR = (HR × SV) × SVR

CO = cardiac output consisting of HR (heart rate) multiplied by SV (stroke volume)
SVR = systemic vascular resistance

MAP Consistently Below 60 mm Hg Can Lead To

1.  Worsening of hypoxaemia

2.  Decreased hepatic metabolism of drugs

3.  Delayed recovery of anaesthesia

4.  Neuromuscular complications

5.  CNS abnormalities

6.  Renal failure, which can have long lasting effects if more than 65–75% of the nephrons are damaged

Methods of Blood Pressure Monitoring

1.  CRT

2.  Pulse palpation

3.  Indirect blood pressure monitoring: Doppler, oscillometric, and HDO

4.  Direct blood pressure monitoring

Treatment of Hypotension Under GA: Find The Cause First!

Treatment of Hypotension Under GA

1.  Blood pressure cuff:

a.  If cuff is too large (should be 1/3 of the total circumference of the paw/tail)

b.  If cuff is above the heart level

2.  Drugs related: reduce the amount administered

3.  Fluid therapy: 10 ml/kg/h to counteract the vasodilation

4.  Fluid therapy in suspected hypovolaemia: a fluid bolus of ‘1 hour worth’ given over 10–15 minutes (e.g. 5 kg dog will have a 50 ml bolus)

5.  Blood loss: 1 ml of blood loss should be replaced with 2–3 ml of crystalloids

6.  If the above treatments do not work, administering of vasopressors and inotropes

Treatment of Hypertension Under GA

1.  Uncontrolled disease factors e.g. pulmonic stenosis

2.  Inadequate depth of anaesthesia

3.  Lack of analgesia

4.  Blood pressure cuff:

a.  If cuff is too small

b.  If cuff is below the heart level