51. Hypotension Flashcards
Hypotension
a) Define
b) Usual numerical value
c) Or a drop of…?
d) More appropriate value in hypertensive patients
e) Equation governing blood pressure
f) Other equation for MAP (and threshold for shock)
a) BP that is much lower than usual and which may be causing symptoms such as dizziness/ light-headedness.
b) Systolic < 90 mmHg , diastolic < 60 mmHg
c) 30 ?
d) 100 mmHg systolic
e) MAP = CO x TPR
- hence anything that reduces cardiac output or vascular resistance (low volume, vasodilation) will reduce BP
f) MAP = 1/3 (SBP - DBP) + DBP
- Shock = requires fluid resuscitation + inotropes/ vasopressors to maintain MAP > 65 mmHg
Orthostatic hypotension.
a) Define
b) Risk factors
c) Drug causes
d) Clinical features
a) A drop in BP (usually >20/10 mm Hg) within three minutes of standing
b) Age, HYPERtension, autonomic dysfunction (eg diabetes, PD, spinal cord lesions), hypovolaemia (dehydration, blood loss, diuretic therapy, Addison’s), drug causes
c) Antihypertensives, diuretics, vasodilators (eg nitrates), antidepressants, antipsychotics, levodopa, barbiturates, alcohol
c) Common: Dizziness, light-headedness, blurred vision, weakness, fatigue, nausea, palpitations, headache
Less common: syncope, chest pain, SOB
Types of shock.
Cardiogenic (reduced CO)
- following MI / arrhythmia / heart failure
Obstructive (physical obstruction of great vessels)
- Massive PE
- Tension pneumothorax
- Cardiac tamponade / constrictive pericarditis
- Critical aortic stenosis
Distributive (vasodilation = reduced TPR):
- Septic - Gram-negative septicaemia.
- Anaphylactic - type I IgE-mediated hypersensitivity reaction.
- Neurogenic - spinal cord lesion causing loss of sympathetic tone
Hypovolaemic:
- blood loss (haemorrhage)
- plasma loss (burns)
- dehydration (diarrhoea and/or vomiting), pooling of unavailable fluids (eg, pancreatitis).
Causes of hypotension.
- common causes
- Post-prandial
- Postural hypotension
- Dehydration/ fluid loss
- Antihypertensive treatment
- Cardiac conditions (heart failure, etc.)
- Adrenal insufficiency
Management of hypotension in acute setting.
a) A-E
b) Fluids prescribed
c) What must you do before prescribing fluids?
A-E assessment:
- Airway - stabilise, NG tube if vomiting/risk of aspiration or need feeding
- Breathing - 100% high-flow oxygen if septic/ reduced responsiveness/ abnormal breathing
- Circulation - Assess volume status, lie with head down, gain IV access, take bloods (FBC, CRP, UEs/ creatinine, glucose, cultures, gas, etc.); IV fluids (having excluded pulmonary oedema)
Fluid prescription:
- Bolus of 500 ml NaCl 0.9% over 15 mins (STAT)
c) Assess volume status: check for signs of overload (pulmonary oedema especially) before giving fluids
IV fluid management: Step 1 (assess volume status)
a) Signs of hypovolaemia
b) Aims of correcting hypovolaemia
a) Systolic BP <100; HR >90 bpm; CRT >2s; RR > 20; cool peripheries
b) To correct the hypovolaemia and hypoperfusion of vital organs such as the kidneys before irreversible damage occurs
IV fluid management: if patient is hypovolaemic
a) Initial management
b) Then do what?
c) How much fluid can you give before escalating?
d) Also in what instance should you escalate?
a) - Identify cause of deficit and respond.
- Fluid bolus 500 ml NaCl 0.9% over less than 15 mins.
- Fluid balance
b) - Reassess using A-E
- Assess volume status and need for further fluid
- If still hypovolaemic, give another fluid bolus of 250 - 500 ml NaCl 0.9%
c) 2000 mL (2L)
d) Signs of SHOCK
IV fluids management: if not hypovolaemic
a) If patient can feed / take fluids orally
b) Assessment of fluid /electrolyte requirements
c) If IV fluids required - normal maintenance fluids and electrolyte requirements
d) If more than 3 days of feeding required, do what?
a) Continue oral rehydration/ nutrition
b) - Obs - pulse, BP, capillary refill, JVP, oedema (peripheral/ pulmonary), postural hypotension
- Fluid balance chart and weight measurements
- Bloods (FBC, UEs, creatinine)
c) Normal daily fluid and electrolyte requirements:
25–30 ml/kg/d water
1 mmol/kg/day sodium, potassium*, chloride
50–100 g/day glucose (glucose 5% contains
5g/100ml)
d) Switch to NG fluids or enteral feeding
IV fluids: replacement and redistribution
a) Required in who?
b) Reasons for ongoing losses
c) Reasons for abnormal distribution issues
d) How to prescribe fluids
a) Those with complex fluid or electrolyte replacement or distribution issues: deficits or excesses, ongoing
abnormal losses, abnormal distribution or other
complex issues. Could be overloaded, dehydrated or have an electrolyte deficit
b) - GI loss: vomiting, NG tube loss, diarrhoea, high-output stoma, biliary drainage loss, GI bleed, pancreatic loss
- Blood loss
- Urinary loss, e.g. post AKI, polyuria.
- Insensible losses: sweating/fever/dehydration/SOB
c) - Gross oedema (renal, liver and/or cardiac impairment)
- Vasodilation (sepsis, anaphylaxis, drug induced)
- Hypernatraemia, hyponatraemia
- Post-operative fluid retention and redistribution
- Malnourished and refeeding issues
d) - Adding to or subtracting from routine maintenance, adjusting for all other sources of fluid and electrolytes (oral, enteral and drug prescriptions)
- Monitor obs, volume status, fluid balance, biochemistry and adjust as necessary
Investigating acute hypotension.
- Bedside: urine dip (or check catheter), assess volume status
- Bloods: FBC (anaemia - ?bleeding), UEs/creatinine (AKI), CRP (infection), lactate (sepsis), LFTs, glucose, clotting, group/save and cross-match
- Blood gas
- Sepsis 6 - BUFALO
- Imaging: CXR, ECHO, ?whole-body CT (trauma), specific for investigating causes (eg endoscopy)
- Special tests: CVP monitoring
