IV fluids in acute-care

IV fluids in acute-care

Isotonic Solutions

·         Normal saline    0.9%NaCl             pre/post-blood transfusion, hyponatremia, metabolic alkalosis

·         Lactated Ringer Na,Cl,K,Ca           electrolye replace, rehydration, metabolic acidosis, infant diarrhea

Hypotonic solutions

·         Half normal saline  0.45%NaCl     hyponatremia

·         D5W                      5% destrose       dehydration; vehicle for hypertonic IV meds

·         Sterile water      none                     vehicle for hypertonic IV meds

Hypertonic solutions

·         3% saline             3% NaCl                severe Na depletion and H2O overload, assess kidney function

·         5% saline             5% NaCl                severe Na depletion and H2O overload, assess kidney function

Types of fluid loss

Hyperacute fluid loss (min to hours):      Normal saline

Dehydration, typical (2-3 days):            Lactated ringer’s

Contraindications

·         Hypotonic solutions: circulatory collapse, hypotention

·         Isotonic solutions: circulatory overload, anemia.

o   Normal saline: elderly and glomerulonephritis (higher risk of hypernatremia)

o   Lactated Ringer’s: liver failure, addison’s dz, sever metabolic acidosis or alkalosis, sever hypovolemia or shock

Given using a large gauge needle (18) over 8-24hr period (a slow push)

Assessing volume status

History: Patient history, observation and fluid charts, patient notes, etc.

Examination: Blood pressure, pulse, respiratory rate, skin turgor and capillary refilll time, temperature

Investigations: urine output (<30 ml/hr for 70kg man), central venous pressure readings, blood tests, chest x-ray

Response to fluid challenge: Give a 500 ml 0.9% saline or 250 ml colloid through large bore 14G (brown) or 16G (grey) cannula over 5 minutes. Measure response: CVP monitoring, pulse or BP increase and reduction of respiratory stress. Repeat as necessary. Fluid challenge is safe is lungs are clear.

Dry patient

Nil-by-mouth, increased fluid loss (diarrhea ot vomiting), thirst and dry mouth

Low CVP, low BP, tachycardia, weight several kg below pre-op weight

Decreased urine output

Bloods: urea disproportionately raised to creatinine, high sodium and potassium levels

Fluid challenge may not be sufficient to raise CVP initially

Overloaded patient

Fluid intake > output

Raised CVP, pulmonary oedema, weight several kg above pre-op weight

Blood sodium level may be low

X-ray may show pulmonary oedema and effusion

CVP rises and plateaus with fluid challange

Daily fluid requirements increase in illness:

·         Fever (500 ml/day for every degree above 37oC)

·         Breathlessness and tachypnoea

·         Diarrhoea and vomiting

·         Haemorrhage

·         Surgical drains, stoma and fistulae

·         Polyuria

·         Third space losses (pancreatitis, bowel obstruction,  and after laparotomy)

·         SIRS – capillary leak

Fluid requirements in resuscitation depends on stages of hypovolemic shock:

Stage 1 (< 15% or <750ml loss):  Normal blood pressure as compensated by increased systemic vascular resistance --> give Crystalloid

Stage 2 (15-30% or 750-1500ml):  Tachycardia, postural hypotension, +/- sweating and anxiety – partially compensated by increased systemic vascular resistance --> give Colloid

Stage 3 (30-40% or 1500-2000ml):  Systolic blood pressure <100 mmHg, tachycardia, tachypnoea, altered mental state (confusion) --> give Colloid + Blood

Stage 4 (>40% or >2000ml):  Very low blood pressure, bradycardia, weak pulse pressure, depressed mental state, urine output negligible --> give Colloid + Blood

Fluid overload risk is high in:

·         Cardiac failure patients

·         Chronic renal failure patients

·         Elderly patients

Post-operation fluid maintenance

·         Aim for urine output of >30ml/hr

·         Maintenance fluid regime (see above)

·         Avoid potassium in the first 24-48 hr post-op

·         Encourage patient to start oral fluids as soon as possible

·         Account for extra fluid losses (drains, fever, etc.)