IV Administration Dosage Calculation Keith Rischer RN

IV Administration – Dosage Calculation Keith Rischer, RN

Alternate Methods Dosage Calc. Formula Ø Ratio proportion Ø Dimensional analysis Ø

IV solutions Administered in plastic bags/bottles Ø Administered continuously and/or intermittently Ø Components: Ø q Water q Glucose(dextrose) q Saline q Electrolytes q Salts

IV solutions Ø Labeled q Letters – solution components q Numbers – concentration q LR – Lactated Ringers q NS: Normal Saline 0. 9% Na. Cl q D 5 W – 5% Dextrose in water = 5 g dextrose / 100 ml solution D 5 NS with 20 m. Eq KCL

IV Solution Label Ø Calculate components: q D 5 0. 45% NS in 1000 m. L q D 10 ¼ NS in 500 m. L

Tonicity of IV Solutions Ø Ø Ø Hypotonic Isotonic Hypertonic Ø Ø Ø Ø Ø 0. 9 NS D 5 W LR ½ (0. 45%) NS ¼ (0. 225%) NS D 5 ½ NS D 5 LR 3% NS

Calculating Flow Rates IV Pumps Ø Total m. L ordered Total hours ordered = m. L per hour Vancomycin 1000 mg (250 m. L) IV over 2 hours by infusion pump Vancomycin 750 mg (250 m. L) IV over 1. 5 hours

IV Flow Rate in m. L per hour: Infusion Rate is less than 1 hour Total m. L ordered X 60 min/hr = m. L/hr Total min ordered Ø Order: q Ampicillin minutes Ø 500 mg IV in 50 m. L NS over 30 Order: q Give Amiodarone 150 mg in 100 ml of D 5 W over 10 minutes

Setting Flow Rates for Manually Regulated IVs Adjusting the rate by hand Ø Counts drops per minute Ø Use the roller clamp to adjust rate Ø

Calculating flow rates - Manually Formula method V X C (gtt factor) = R T Volume (m. L) X drop factor (gtt per m. L)= Rate (gtt/min) Time (min) Ø Physician orders: D 5 W IV at 125 m. L/hr. q q Ø The IV infusion set is calibrated with a drop factor of 10 gtt/m. L. Calculate the IV flow rate Physician orders: 0. 9 NS IV at 75 m. L/hr. q q The IV infusion set is calibrated with a drop factor of 10 gtt/m. L. Calculate the IV flow rate

Calculating gtts per/minute Ø Once gtts/minute determined. . . q Divide this total by a factor of 4 ü 20 gtts/minute… 5 gtts every 15 seconds ü 12 gtts/minute… 3 gtts every 15 seconds q How many gtts every 15 seconds? . . . q Divide the gtts determined by 15 (seconds) q This will be the seconds between each gtt ü 5 gtts every 15 seconds – 15/5= x seconds ü 3 gtts every 15 seconds – 15/3= x seconds

Calculation of Drops per min: Microdrip Drop Factor Volume (m. L) X drop factor (gtt per m. L)= Rate Time (min) Ø Order: q D 5 NS IV at 50 m. L per h Drop factor is 60 drops per m. L Ø Calculate gtt/min Ø

Drop Factor Constants Drop Factor 10 drops per m. L 15 drops per m. L 20 drops per m. L 60 drops per m. L Drop Factor Constant

Drop Factor Constants Ø Physician orders: D 5 W IV at 125 m. L/hr q 10 gtts/m. L manual infusion set q 125 m. L=20. 8 gtt/minute or 21 gtts 6 Ø Physician orders: 0. 9 NS IV at 75 m. L/hr. q 75 m. L= 6

Adjusting IV Flow Rate Check for institutional policy regarding correcting off-schedule IV rates and the percentage of variation allowed Ø Variation should not exceed 25 percent Ø q% variation will be positive (+) if administration is slow and rate has to be increased q Negative ( ) if administration is too fast and rate has to be decreased

Adjusting IV flow rates Ø Follow three steps: q Remaining volume = recalculated m. L/h Remaining hours q V X C (gtt factor) = R T q Adjusted gtt per min – ordered gtt per min = % variation Ordered gtt per min

Calculation of IV Flow Rate Adjustment Ø Order: 500 m. L LR to run over 10 hours at 50 m. L per hour q Drop factor is 60 drops per m. L and IV is correctly infusing at 50 drops per min q After 2 hours, 300 m. L is remaining q Almost half of total volume infused in onequarter the time

Calculation of IV Flow Rate Adjustment IV infusion is ahead of schedule Ø Compute a new rate of 300 m. L to complete IV fluid order in remaining 7 hours Ø Patient would require close assessment for fluid overload Ø

Calculation of IV Flow Rate Adjustment Adju st rate ed flow 1 1

Calculation of IV Flow Rate Adjustment Ø Adjusted gtt per min – ordered gtt per min Ordered gtt per min 40 – 50 = -10 50 50 = -0. 2 = - 20%

Adjusting IV flow rates Ø The physician orders 1000 m. L of D 5 0. 45% NS at 100 m. L per hour over 10 hours. Drop factor-10 gtt per m. L q What is the initial correct gtt/minute ü How q After many gtts/15 seconds… 1 gtt every __ secs. 5 hours only 300 m. L has infused. The IV is behind schedule. Calculate the new flow rate. Is this new rate acceptable?

IV Push Injections Ø Use same calculations as other parenteral injections Ø IMPORTANT – Follow manufacturer or hospital guidelines for rate of administration

IV Push Rate Calculation Dosage Desired Quantity (available form) IV Push Rate Time Supply Dosage Recommended

Calculation of IV Push Rate Order: Furosemide (Lasix) 40 mg IV Push stat x 1 Ø Supply: Furosemide 10 mg per m. L with drug literature guidelines of “IV infusion not to exceed 20 mg over 1 minute” Ø

Calculation of IV Push Rate Ø How much Furosemide should you prepare? q Step ü No q Step 1. Convert conversion is necessary 2. Think ü You want to give more than 1 m. L

Calculation of IV Push Rate Ø How much Furosemide should you prepare? q Step 3. Calculate

Calculation of IV Push Rate Ø What is a safe infusion time? q Use the formula: D X Q =X H 40 mg X 1 min = 2 minutes 20 mg

Calculation of IV Push Rate Ø Ø How much should you infuse every 15 seconds? Push Factor Constant q 4 per minute 15 seconds = 1/4 60 seconds q 4 m. L over 2” q Push factor is 8 (4 x 2”=8) Volume 4 m. L=0. 5 m. L push every 15 seconds Push Factor 8

Calculation of IV Push Rate Ø Order: Dilantin 100 mg IV now q Supply: Dilantin 50 mg per m. L with drug literature guidelines of “the infusion rate should not exceed 50 mg per min”. q How much should you prepare? q What is safe infusion time? q How much should you infuse every 15 seconds?