For many clinicians, the prescribing of intravenous fluids can be a complex and controversial issue due to different approaches to assessment and rationale for use. This could be a result of differing methods and thought processes, learnt historical practices, lack of clear guidance or personal preference of particular intravenous fluid solutions over others. Teaching and education around the topic of intravenous fluid prescriptions is often limited and of poor quality (McDougall et al, 2022).
Having recently undertaken the non-medical prescribing module, the author, a trainee advanced clinical practitioner (tACP), identified that there had been no specific teaching in relation to the prescribing of fluids during the module. This could be due to the programme being aimed at both primary care and secondary care clinicians. The non-medical prescribing module aims to deliver generic prescribing content, with the understanding that clinicians from specialist backgrounds will have an element of knowledge of prescribing within that area of practice (Royal Pharmaceutical Society, 2021). It is also expected that students on this module use their 90 hours of supervised practice to further tailor their learning needs.
With limited information on the wider curricula for the non-medical prescriber programmes in the UK in relation to prescribing intravenous fluid, studies focusing on medical education were reviewed.
Insufficient teaching on prescribing intravenous fluids
Powell et al (2014) identified that the majority of medical textbooks available in the UK are insufficient in providing knowledge around the considerations for the prescription of intravenous fluids. Despite a common consensus that the art of prescribing fluids can be learnt in clinical practice, it is suggested that assessment of intravenous therapy prescriptions in medical education is sub-optimal (Ding and Varkey, 2022). This may lead to the assumption that junior doctors leave their medical education with limited knowledge of fluid therapy. It is estimated that only 16% of consultant surgeons felt their trainee doctors had been provided with adequate training and knowledge in prescribing intravenous fluids (Powell et al, 2014).
Meanwhile, Ramsay et al (2018) examined the knowledge of junior doctors of the constituents of commonly prescribed fluids, with only 48% of doctors correctly identifying the sodium content in Hartmann's solution. Worryingly, of the incorrect answers, the average response to sodium content was 20% lower than the actual value, leading to concern that patients are being salt-loaded without intention, leading to a possibility of adverse effects on the patient (Ramsay et al, 2018). In areas of Scotland, however, there is dedicated teaching within the medical curricula in relation to prescribing intravenous fluids, this is linked closely to national guidelines, and newly qualified doctors receive additional fluid specific training within their first year of practice (Mathur et al, 2020).
Prescribing of intravenous fluids may seem commonplace, Glassford et al (2016) indicated that around £156 million was spent per year by the NHS, with an estimated 5 million acute admissions annually, and the assumption that the majority of these admissions will receive intravenous fluid therapy. It is acknowledged that this data does not reflect the present climate and is likely to now be an underestimation of current use.
Fluid prescribing errors
The National Institute for Heath and Care Excellence (NICE) (2013) suggests that almost 1 in 5 patients prescribed intravenous fluids develop complications or morbidity due to unsuitable administration. Reporting of fluid mismanagement and fluid prescribing error is poor and the causes of such are often multifactorial, although it is difficult to identify common errors and frequency in which they occur (Gao et al, 2015; Mathur et al, 2020). While medication errors have clear reporting procedures, intravenous fluids are not usually classified as medication; however, consideration must be given to the indications and contraindications of fluids prescribed, as with all prescribed drugs (Malbrain et al, 2018; Wuyts et al, 2022).
As a result, NICE issued guidelines (2013) on intravenous fluids for adults in hospital, which have been deemed important as, other than oxygen, intravenous fluids are the most commonly prescribed therapy for inpatients (Torjesen, 2013). These guidelines recommend that any mismanagement of intravenous fluid therapy or adverse effects are reported to encourage enhanced training and safer clinical practice (NICE, 2013).
It is important to note that there is often no clear correct clinical decision in relation to intravenous fluids and that no one regimen fits all; therefore, it is vital to maintain an element of self-awareness and preparedness that the prescription may not have the desired effect on the patient, and there may be a need for frequent reassessment (MacDonald and Pearse, 2017). Although deemed one of the most frequent interventions undertaken in hospitalised patients, intravenous fluids are complex, and the consequences of the incorrect volume, rate or constituent of prescribed fluid can have detrimental effects on the patient (Perner et al, 2019; Zellweger et al, 2021).
The 5 R's
In a bid to standardise the approach, NICE (2013) developed the 5 R's of fluid prescriptions as an aid for clinicians to consider ‘Resuscitation, Routine maintenance, Replacement, Redistribution and Re-assessment’. However, before any consideration of prescribing fluids, thorough assessments must be undertaken (Padhi et al, 2013).
‘It is important to note that there is often no clear correct clinical decision in relation to intravenous fluids and that no one regimen fits all’
When assessing the patient's need for fluid or electrolyte replacement, as with any assessment, a history is key (Padhi et al, 2013). The ability to decipher accurate information on fluid intake and measurement of insensible losses such as vomiting and diarrhoea can aid decision-making and safe prescribing of intravenous fluids (McNeil-Masuka and Boyer, 2021). The added benefit of laboratory trends, fluid balance assessments and discussion with nursing teams directly involved in the patient's care can facilitate a more accurate assessment.
To ensure a comprehensive fluid assessment of the patient, clinical examination should include observation of the patient's heart rate and blood pressure, ideally with lying and standing blood pressure readings obtained to assess for any postural hypotension (Wade, 2021). NICE (2013) recommends that capillary refill and measurement of the jugular venous pressure are also undertaken for all fluid assessments.
Auscultation of the chest to identify any evidence of pulmonary oedema is recommended and is characterised by crepitations that remain evident following the patient coughing (Ruthven, 2016). In addition, signs of peripheral oedema should be examined, as this accumulation of fluid may contribute to skin breakdown or lead to organ dysfunction (Malbrain et al, 2018). As previously discussed, fluid balance charts provide vital data to enable informed decision-making regarding fluid assessment, although trends in the patient's vital signs and NEWS score, alongside their weight, are also valuable tools to aid the clinician's assessment (NICE, 2013).
Scottish IV Fluid Improvement Programme
Locally, there is no standardised documentation for measuring fluid balance, with a mix of paper and electronic charts in use across the inpatient wards, and all fluid prescriptions are made on paper forms.
The Scottish National IV Fluid Improvement Programme was created to standardise the use and compliance of fluid balance charts and fluid prescriptions across Scotland (Mathur et al, 2020). These charts prompt the clinician to review the most recent laboratory results and guide clinical decision making, from determining the patient's fluid status and the rationale behind the consideration of prescribing fluids to the quantity and the fluid content to be prescribed (Mathur et al, 2020). In addition, the standardised fluid balance form prompts the calculations of subtotals at 2 pm and 6 pm, with the aim of detecting and recognising the deteriorating patient earlier (Mathur et al, 2020). For clinicians working in the out-of-hours setting, this could help to reduce the delayed referral into the service for deteriorating patients or requests for maintenance fluids overnight.
Despite this not being standardised practice for the rest of the UK, NICE (2013) guidance recommends that patients prescribed intravenous fluids should have a management plan, which should encompass fluid prescription for the following 24 hours, preventing the need for out-of-hours clinicians to intervene unless the patient's condition deteriorates. However, this relies on adequate monitoring from the nursing staff caring for the patient, and ensuring they are competent and confident in the recognition of the deteriorating patient, and able to escalate concerns effectively. Nursing staff are directly involved in administering and monitoring intravenous fluids, but have varying knowledge of their use, which has a variable impact on patient safety (Wuyts et al, 2022).
Importance of checking electrolytes
Laboratory investigations are a useful tool in monitoring the patient's hydration status and electrolyte levels (Eastwood et al, 2012). Observing for trends in periodic results may also guide the clinician to pre-empt or identify deterioration. NICE (2013) recommends that patients undergoing intravenous fluid therapy should have a minimum of urea, creatinine and electrolytes checked daily.
Once the patient and all available resources have been reviewed, the clinician should at this point be able to identify the fluid status of the patient and begin to consider the five ‘R's’ of fluid assessment (NICE, 2013). Imperative to the consideration of the suitability for intravenous fluids identifying whether the patient is hypovolaemic, euvolaemic or hypervolaemic will guide the most appropriate fluid management (Potter and Wynter, 2021).
Hypovolaemia
The NICE (2013) guidelines suggest signs of hypovolaemia include a systolic blood pressure of less than 100 mm of mercury (mmHg), a tachycardia greater than 90 beats per minute, prolonged capillary refill or cold peripheries, tachypnoea, an elevated National Early Warning Score (NEWS) of 5 or more, or via passive leg raising and observing for haemodynamic improvement. It is acknowledged that there is no standardised ideal treatment in cases of hypovolaemia, but fluid resuscitation is often required in these patients.
The primary focus of fluid resuscitation is the rapid replacement of the circulating volume to support adequate organ perfusion (MacDonald and Pearse, 2017). While identifying the cause for the hypovolaemia, such as sepsis, NICE (2013) guidelines advise administering a bolus of intravenous crystalloid fluid. A fluid bolus is a fast administration of a measured amount of fluid over a limited period of time, typically 500 ml over 15 minutes or less (Malbrain et al, 2018, Mathur et al, 2020). It is estimated that less than 50% of haemodynamically unstable patients will have a positive response from the fluid bolus, and in those who do respond, effects reduce within one hour of administration (Nickson, 2020).
Hypervolaemia
Hypervolaemia, or fluid overload, may present with peripheral oedema, weight gain, increased urine output and a positive fluid balance (Potter and Wynter, 2021). Fluid overload can affect most organ systems; for example, the formation of ascites, development of cerebral oedema or impaired cardiac contractility (Malbrain et al, 2018). In these cases, fluid administration should not be considered, and patients may instead require a fluid restriction (Mathur et al, 2020; Potter and Wynter, 2021).
Euvolaemia
Euvolaemic patients who are haemodynamically stable but unable to meet the fluid requirements required on a daily basis should be considered for routine maintenance (NICE, 2013; Potter and Wynter, 2021). NICE (2013) provides clear guidance on the daily requirements for the average adult, including 25–30 ml per kg of water per day, 1 mmol/L per kg per day of potassium, chloride and sodium and 50–100 g per day of glucose to prevent starvation ketosis. Theoretically, this should provide the clinician with adequate information to safely prescribe maintenance fluids, although there is no suggestion of ideal rates of administration.
Nevertheless, local guidelines, adapted from the NICE guidance, suggest a maintenance fluid rate of 1–1.5 ml per kg, per hour (ml/kg/hr) (University Hospitals of Derby and Burton NHS Foundation Trust (UHDB), 2021). More importantly, these guidelines address co-morbidities such frailty, cardiac or renal disease and suggest a reduced infusion rate of 0.5–0.75 ml/g/hr, with a total fluid allowance of 20–25 ml/kg per day (NICE, 2013; UHDB, 2021).
In the absence of insensible losses, alternative means of encouraging an adequate fluid intake should be considered before commencing intravenous fluids (UHDB, 2021). For example, during a night shift, the tACP asked to prescribe intravenous fluids for a patient who had a minimal fluid intake during the day. On review of the fluid balance chart, the patient had been sleeping for most of the day and the patient tended to be awake for most of the night. In this instance, the ward staff were asked to optimise the time that the patient was awake to encourage oral fluids overnight, and re-assess the fluid intake in the morning.
Types of intravenous fluids
Despite there being many types of intravenous fluid available, national and local guidelines provide limitations for a small number of crystalloids and colloids (Vincent, 2020). Crystalloids are solutions containing small molecules dissolved in water, such as sodium chloride, dextrose or Hartmann's solutions, while colloids are solutions containing larger molecules, such as albumin (Potter and Wynter, 2021).
It is understood that 0.9% sodium chloride, a commonly used fluid choice, has a higher chloride content than human plasma, which can attribute to metabolic acidosis if used for fluid resuscitation (Self et al, 2017). Malbrain et al (2018) indicate that 0.9% sodium chloride should not be administered in large quantities as it increases the risk of acute kidney injury, metabolic acidosis due to hypernatraemia and hyperchloraemia or even death. This interpretation contrasts with that of a Cochrane review of the use crystalloids vs colloids in fluid resuscitation in the critically unwell, where there was little to no difference in mortality using either solution (Lewis et al, 2018).
In addition to fluid resuscitation and maintenance, fluid and electrolyte replacement is another cause for prescribing intravenous fluids. NICE (2013) guidance for replacement and redistribution is to adjust the maintenance fluid guidelines to replace or reduce the electrolyte deficit as appropriate. Local guidelines provide clear treatment pathways for the common electrolyte imbalances, such as hyperkalaemia, hypokalaemia and hyponatraemia. For cases of ongoing fluid losses, there is evidence which provides values of electrolyte concentrations per mode of fluid loss so that prescriptions can be made to best match the losses (NICE, 2013).
This article highlights the multitude of considerations when prescribing intravenous fluids, and that reassessment is key to safe fluid administration, and forms the fifth and final principle of fluid prescriptions (NICE, 2013). Malbrain et al (2018) believe that intravenous fluids should be monitored similar to that of antibiotic stewardship. It also highlights that guideline are there only to support and guide a clinician, and that adaptations must be made on an individual basis. For example, the NICE (2013) fluid administration guidelines should not be utilised for patients who have had a traumatic brain injury, diabetic or pregnant patients (Woodcock, 2014).
Conclusion
The aim of this article has been to identify considerations for the prescription of intravenous fluids and to address a knowledge gap, using current guidelines and research to provide a thorough evidence base for clinical practice. What initially presented as a limitation to practice has now become a strength, and has instigated a drive to disseminate this knowledge and to work towards improving the intravenous fluid prescribing practice for both prescribers and patients.
Key Points
- Prescribing the incorrect type, volume and/or rate of intravenous fluids can have a detrimental effect on the patient
- The 5 ‘Rs’ of fluid prescriptions are: resuscitation, routine maintenance, replacement, redistribution and reassessment
- Evidence suggests that 1 in 5 patients prescribed intravenous fluids develop complications or morbidity
- 09.% sodium chloride contains more chloride than plasma can contribute to metabolic acidosis if used in fluid resuscitation
CPD reflective questions
- Colloids are also known as plasma expanders. How do they act differently compared to crystalloids?
- It is important to visually assess the patient prior to prescribing fluids. What should be included in this assessment?
- Reflecting on points highlighted in this article do you feel where you work, fluid intake and output is accurately recorded? If the answer is no, what can you do to improve this?
- What is a fluid bolus and how is it typically administered? How would you consider if it has been effective?