Question

The doctor orders a continuous infusion (IV) of morphine for a post-operative teenager of 200 mcg/kg q 3 hr. The teenager weighs 105 lbs. You have 2 mg/mL solution of morphine available for IV injection. STATE THE ANSWER IN SCIENTIFIC NOTATION AND CORRECT NUMBER OF SIGNIFICANT FIGURES

a. What rate of infusion (mL/hr) should you set for the IV drip?

b. The continuous infusion device can only hold a total of 25 mL of morphine solution. How long will it be before you have to replace the morphine solution? Express your answer in hours with the remainder converted to minutes. (i.e. your answer should be something like “in 3 hours and 14 minutes”).

Answer 1

ANSWER

a, Rate of infusion set for the IV drip.

      Formula

        Rate of infusion = Amount desired (D) / Amount on hand (H) * Quantitiy(Q).

                 Amount desired (D) = 200 mcg / kg / q 3 hr.

                 Weight of the patient = 105 lbs.

                                            1 lbs = 0.45 kg.

                                                     = 47.3 kg.

                So,

                    Amount desired for this patient(D) = 200 mcg / kg / q 3hr

                                                                            = 0.2 mg / kg.

                                                                             = 0.2 mg * 47.3

                                                                             = 9.46 mg / q 3hr.

                   Amount on hand(H) = 2mg / ml.

                                                   Quantity(Q) = 1 ml.

                          As per formula

                                              Rate(ml/hr) = D / H *Q

                                                                   = 9.46 / 2 * 1

                                                                   = 4.73 ml / q 3 hr.

                                                                   = 1.58 ml / hr.

b. Infusion time

          Amount of morphine infusion hold by the infusion device = 25 ml.

                        Infusion rate of morphine solution = 1.58 ml / hr.

        Time taken for finish 25 ml of solution = Total volume infused / rate

                                       (Infusion time)               = 25 ml / 1.58ml / hr.

                                                                               = 15.82 hr

                                                                               = 16 hr and 22 minutes.