How to administer inotropic drugs part 2

Evidence base

The administration of medication must comply with standards, which stipulate that two nurses should check intravenous drugs before administration (NMC 2010). This includes ensuring the prescription is accurate and clearly indicates patient identification, name of the medication, dose, route of administration and dilution fluid (National Patient Safety Agency 2007).

Inotropic drugs have a potent effect on the cardiovascular system, and the nurse should possess sound knowledge both of the pharmacodynamics of the drugs and the practicalities of administration. The appropriate dilution fluid can be ascertained using Appendix 4 of the British National Formulary (2016) (Table 1).

Using the correct dilution fluid is important because some inotropes such as noradrenaline undergo a greater degree of oxidisation when mixed with 0.9% sodium chloride compared with 5% dextrose. If there is doubt about the correct dilution fluid, the department pharmacist could be contacted to provide clarification.

Nursing management

Connecting infusions to a CVC poses an infection risk to patients, which carries a mortality rate of up to 25%, therefore infection control guidance should be followed stringently (Edwards et al 2014). This includes:

• Handwashing before preparing the infusion and wearing non-sterile gloves to prepare and connect the infusion (Dumyati et al 2014).
• The nurse should also ensure that the drug is mixed thoroughly in the dilution fluid to ensure even concentration throughout the infusion.
• Once the infusion has been prepared it should be labelled clearly reflecting the prescription.
• There are standardised drug concentrations that should be followed (Intensive Care Society 2014). The administration port on the CVC should be thoroughly cleaned with 2% chlorhexidine in 70% isopropyl alcohol solution to avoid introducing bacteria into the circulation (Loveday et al 2014).
• The administration line should be dated to ensure regular line changes are made, since research indicates administration lines should be changed every 96 hours (O’Grady et al 2011, Loveday et al 2014).

Risk assessment and management

The initiation and renewal of an infusion of an inotropic drug carries potential risks to the critically ill patient who depends on a stable therapeutic dose to maintain haemodynamic parameters. Different types of haemodynamic changes can occur when initiating or renewing inotropes, which are dictated by the receptors that a particular inotrope acts on, as detailed in Table 1

For example, dobutamine affects Beta-1 and Beta-2 receptors, resulting in an enhanced cardiac output by increasing myocardial contractility and heart rate, but decreases the diastolic pressure through vasodilation. Haemodynamic instability can often be observed when renewing the infusion and is caused by a reduction in serum levels of the inotrope; most inotropes have a half-life of 2-3 minutes (Trim and Roe 2004). The nurse should mitigate against this by preparing new infusion syringes well in advance of the current infusion finishing.

Methods such as double pumping involve commencing a second syringe of the inotrope before the previous infusion finishes. This avoids the abrupt drop in serum levels that would result in haemodynamic instability (Trim and Roe 2004). Anecdotal evidence suggests that there is a risk of administering an inadvertent bolus during this procedure, resulting in cardiovascular instability. This risk can be minimised if the nurse is knowledgeable about the mode of action of inotropes and is skilled in using infusion equipment and interpreting cardiovascular monitoring.

The use of invasive cardiac output monitoring devices assists the nurse in rapidly assessing the haemodynamic effects the patient experiences during infusion renewal (Cottis et al 2003). For example, when changing a dobutamine infusion using the double pumping technique, the cardiac output can be seen to increase when the second infusion is contributing to serum dobutamine levels. In the case of a noradrenaline infusion, the systemic vascular resistance index will increase when the second noradrenaline infusion is contributing to serum noradrenaline levels. These increases indicate to the nurse that the first infusion can be stopped with minimal risk of haemodynamic instability.

It is important the nurse makes use of monitoring equipment since each patient will display varying degrees of sensitivity to alterations in the infusion. The nurse should also consider the time it takes for the syringe driver to apply pressure on the syringe plunger. The method described in this module involves running the infusion before connecting it to the CVC, enabling visualisation of fluid dripping from the administration set.

Because of the vasoactive properties of inotropic drugs and poor tissue perfusion resulting from critical illness, skin perfusion may be poor and the risk of pressure ulcer development is therefore high. The nurse should regularly assess pressure areas and general skin integrity. Accurate completion of pressure area assessment and regular re-assessment can help prevent pressure ulcer development; regular re-positioning and use of pressure-relieving devices are also recommended.

Inotropic drugs can cause significant vasoconstriction at higher doses, meaning that the accuracy of oxygen saturation readings can be unreliable because of poor peripheral perfusion; one recommendation is to use a probe on the patient’s earlobe. Vasoconstriction can also result in peripheral ischaemia which, in severe cases, can lead to loss of digits. As before, regular skin assessment can alert the nurse to these issues, and any concerns should be reported to the medical team. The patient’s blood glucose levels should also be closely monitored since hyperglycaemia is common in critical illness. Blood glucose should be maintained below 10mmol/L (Finfer et al 2009).

• Morrill P (2000) Pharmacotherapeutics of positive inotropes. AORN Journal. 71, 1, 171-185.
• National Patient Safety Agency (2007) Promoting Safer Use of Injectable Medicines. NPSA, London.
• NHS Wales (2013) Use of the Injectable Medicines Guide Website in Clinical Areas – IntraVENOUS Medicine Monographs (January 2013). http://medusa.wales.nhs.uk/docs/Use%20of%20IV%20monographs%20in%20clinical%20areas%20January%202013.pdf (Last accessed: August 28 2015.)
• Palmer K, Pennefather SH (2009) Inotropes. Anaesthesia and Intensive Care Medicine. 10, 8, 362-366.
• Parry A (2012) Inotropic drugs and their uses in critical care. Nursing in Critical Care. 17, 1, 19-27.
• Trim JC, Roe J (2004) Practical considerations in the administration of intravenous vasoactive drugs in the critical care setting: the double pumping or piggyback technique – part one. Intensive and Critical Care Nursing. 20, 3, 153-160.
  

  References

  British National Formulary (2016) British National Formulary No. 71, September 2014 – March 2015. BMJ Group and the Royal Pharmaceutical Society of Great Britain, London.
  Cottis R, Magee N, Higgins DJ (2003) Haemodynamic monitoring with pulse-induced contour cardiac output (PiCCO) in critical care. Intensive and Critical Care Nursing. 19, 5, 301-307. MEDLINE •CROSSREF
  Dumyati G, Concannon C, Wijngaarden E et al (2014) Sustained reduction of central line associated bloodstream infections outside the intensive care unit with a multimodal intervention focusing on central line maintenance. American Journal of Infection Control. 42, 7, 723-730. MEDLINE •CROSSREF
  Edwards M, Purpura J, Kochvar G (2014) Quality improvement intervention reduces episodes of long-term acute care hospital central line-associated infections. American Journal of Infection Control. 42, 7, 735-738. MEDLINE •CROSSREF
  Finfer S, Chittock DR, Su SY et al (2009) Intensive versus conventional glucose control in critically ill patients. New England Journal of Medicine. 360, 13, 1283-1297. MEDLINE •CROSSREF
  Intensive Care Society (2014) Medication Concentrations in Critical Care Areas (2010) www.ics.ac.uk/ICS/guidelines-and-standards.aspx (Last accessed: October 3 2016.)