Calculating in obstetrics

CHAPTER 7 Calculating in obstetrics



Learning outcome


Be able to apply the principles of drug calculation previously covered to obstetrics



Introduction


Calculating drug doses in obstetrics is no different from calculating in other settings. Accuracy is as important as ever. Both mother and child must be considered (see Chapter 8 for paediatric calculations).



The mother


Extreme care is needed in the use of any medication during pregnancy because of the potential side-effects on the growing fetus. Calculating doses of drugs in obstetrics requires attention to the details set out in the prescription which may be more complex than in normal adult settings.


While most pregnancies are straightforward, complications such as pre-eclampsia, eclampsia or postpartum haemorrhage may arise. Because of the changing needs of the mother during labour, drug doses may need to be modified and rates of administration may alter. Termination of pregnancy may be achieved medically (with the help of drugs). The mother may have a pre-existing medical condition that requires ongoing medicine management or the mother may be a teenager with lower dose requirements. Mothers who are drug-abusing will also require special consideration.



The neonate


As well as caring for the mother, midwives have a responsibility for the immediate care of the newborn. In some cases, this may mean providing resuscitative measures. Premature and multiple births call for special measures.



Calculations




Demonstration 7.1


Atosiban is to be diluted to a concentration of 750 micrograms/mL. Prepare 100 mL of dilute solution for IV infusion (in glucose 5%).


Amount of atosiban required is:



image



Convert to mg:



image



The solution available (as a concentrate) for dilution contains 7.5 mg in 1 mL in 5 mL vials (or 37.5 mg in 5 mL).


Applying the formula,



image



10 mL is diluted to 100 mL (in glucose 5%)


18 mg/hour is to be administered over 3 hours. What volume per hour will require to be administered?



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Therefore 18 mg is contained in

Related posts:

  1. Prescriptions, labels and SI units
  2. Calculating parenteral doses: large volume
  3. Drug calculations explained
  4. Calculating parenteral doses: small volume

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Jun 18, 2016 | Posted by in MIDWIFERY | Comments Off on Calculating in obstetrics

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