INTRAVENOUS CATHETERS AND FLUID THERAPY
Goals of Fluid Therapy
- Replace and correct any imbalances
- Restore effective circulating volume and blood pressure
- Provide the body‚Äôs maintenance requirements of water and electrolytes
- Summed up by replacing deficits, supplying maintenance requirements, and matching ongoing losses.
Origins of fluid, electrolyte, and metabolic disturbances
- Inability to eat or drink
- Loss of fluid and electrolytes
- Trapping of fluid with the body
- A consequence of shock
- Reduction in total body water
- Occurs due to water deprivation or excessive fluid loss
- Decreased circulating volume of fluid
- May result from dehydration, hemorrhage, shock, or sequestration of fluid in the body
- Reduces fluid volume returning to the heart
- Decreases cardiac output (volume of fluid pumped out by the heart)
- Inadequate tissue perfusion
- Profound physiologic changes in the body causing circulatory collapse, inadequate tissue oxygenation and perfusion
- Treatment is increasing tissue blood flow ‚Äì fluid therapy is vital
- Can be caused by allergic reactions, blood loss, dehydration, infection (and release of bacterial toxins), and trauma
Clinical signs of dehydration
- Dry mucous membranes
- Sunken eyes
- Decreased skin elasticity
Clinical signs of hypovolemia
- Tachycardia (increased heart rate)
- Pale mucous membrane color
- Prolonged capillary refill time
- Poor pulse quality
- Cool extremities
- Delayed jugular refill time
Packed cell volume and total plasma protein concentration
- Laboratory methods for assessing fluid deficits and monitoring fluid therapy
- Easily performed
- Packed cell volume refers to the percentage of blood that is taken up by cells
- Total plasma protein is an estimation of the concentration of proteins in the plasma (the fluid part of the blood)
Fluids and additives commonly used
- Isotonic (0.9%) saline ‚Äì this is rarely used for fluid therapy but may be used to treat certain conditions
- Lactated Ringers Solution ‚Äì the most commonly used fluid at the clinic (also known as LRS)
- Potassium chloride (KCl) ‚Äì a common additive to LRS for animals not eating (especially animals with intestinal diseases like colic or diarrhea).¬† Usually added at 20 mEq/L (100 mEq or 50 cc per 5 L bag)
- Calcium gluconate ‚Äì commonly added to LRS for animals with intestinal diseases (colic or diarrhea).¬† Usually added at 250 cc in one set of fluids (divided into two 5 L bags).¬†¬† With many post-operative colic cases, both potassium and calcium are mixed in the fluids and given in this manner. One set of fluids with additives followed by one set without and alternating back and forth.
- Dextrose ‚Äì a sugar added to fluids especially for babies who cannot maintain their blood sugar levels.¬† Usually made into a 5% solution by adding 100 cc of 50% dextrose to a 1 L bag of LRS.¬† This is dripped at a constant rate.¬† This fluid is never to be discontinued abruptly.¬† It is always meant to be stopped in gentle manner by slowing the drip over one day or so
- DMSO (dimethylsulfoxide) ‚Äì An anti-inflammatory added to fluids.¬† The amount is determined by the animal‚Äôs weight.¬† It is never to be more concentrated than 10%.¬† Therefore if the animal is to get 500 cc, that can go in no less than 5 L LRS.¬† It must be administered at a drip ‚Äì never administered as a bolus.¬† If administered too quickly, there will be damage to the patient‚Äôs red blood cells.
- Magnesium ‚Äì added to fluids frequently at a rate of 0.3 cc per kilogram body weight over a 24-hour period.
Fluid rates commonly used
- Each case will have a dictated rate of fluid administration
- Typically for adults the rate will be between one liter per hour (maintenance for most adults) and three liters per hour
- Foals will generally receive 3 to 5 ml/kg/hr.
- Note the formula for weight conversion is as follows:
- 2.2 pounds = 1 kilogram or kg Therefore 125 # foal/2.2=56.8 kgs
- 1000 # horse / 2.2 = 450 kgs
Where adults will generally be receiving a continuous infusion, foals may be getting fluids as a bolus every four hours.
- ¬†Drip rate is determined by the administration set.¬† Each administration set will say what drip rate (i.e. drops per second) is needed to achieve a certain fluid rate.
- Drip rate for the large animal administration set is as follows
- 3 drops per second is approximately 1 liter per hour
- 5 drops per second is approximately 2 liters per hour
- The transition from drop to flow is approximately 6 liters per hour (affectionately known as the ‚Äúmachine gun drip‚Äù)
- Full open is approximately 19 liters per hour
- Drip rate for foal set is 1 drop per 2 seconds is approximately 100 ml/hr.