Monitoring patients on parenteral nutrition (PN) requires a multidisciplinary approach with effective communication throughout the team. This will help to minimise potential complications, and will aid safe, effective and appropriate use of PN. The team should include, at minimum, input from a Doctor, Nurse, Dietitian and Pharmacist, all experienced in PN.
When establishing a new patient on PN, daily review is recommended until the patient is stable in terms of electrolytes, nutrient provision and fluid balance. Achieving stability requires detailed, timely review, with appropriate alterations made to the PN.
| Patient | Guidance for review |
|---|---|
| Unstable inpatient | Daily |
| Stable inpatient | 2-3 times per week to weekly |
| Unstable home patients | 2-3 times per week to weekly |
| Stable home patients | Monthly to 3 monthly depending on condition |
Adapted from NICE (2006) ESPEN (2009)
Goals
The rationale for PN, together with clear goals, should be established at the initial assessment. Goals should then be reviewed at each contact to facilitate effective monitoring and appropriate use of PN (NCEPOD, 2010).
Nutritional status
Nutritional status is most effectively assessed and monitored through a combination of anthropometric data, biochemical and clinical measures. A stand-alone measure e.g. weight, can rarely provide adequate information.
| Parameter | Frequency | To assess |
|---|---|---|
| Weight | Daily if fluid balance concerns. Otherwise weekly. | Fluid balance and nutritional status. |
| Height | Baseline. Review with growth/degeneration. | Body Mass Index |
| BMI | Baseline then repeated if dry weight or height changes. | Nutritional status |
| Mid-arm circumference | Baseline, then monthly | Estimate body composition and function. |
| Triccep skin fold | Baseline, then weekly | Estimate body composition and function. |
| Grip strength | Baseline, then weekly | Estimate body composition and function. |
Clinical parameters
| Parameter | Frequency | To assess |
|---|---|---|
| Biochemistry | Baseline, daily then at each review once stable. | See biochemistry section below. |
| Temperature | Daily | Signs of sepsis and review fluid requirements. |
| Fluid balance | Daily, then at each planned review once stable. | Hydration and compare nutrition prescribed vs delivered. |
| Blood glucose | Baseline, 1-2 times/day then at each review. If has diabetes, follow local policy. | Glycaemic control. Signs of sepsis. Rebound hypoglycaemia if PN timings change or if PN stopped. |
| Access route | Daily | Signs of line infection or access issues. |
| Clinical condition and medical plan | Daily initially, reducing to twice weekly once stable | Whether goals of PN are being met. Nutritional requirements. Appropriateness of PN and manage potential complications. |
| Medications | Baseline then at each review once stable | Drug-nutrient interactions. Establish whether medications are affecting gastro-intestinal function/clinical condition. |
| GI function and enteral intake | Daily initially, reducing to twice weekly | Ability to take enteral nutrition. Tolerance to enteral nutrition. Establish the amount of PN required to meet nutritional needs. |
Adapted from NICE (2006) Nutrition support in adults.
Biochemistry
Careful interpretation of biochemistry can provide important information relating to a number of factors including hydration status, renal function, risk of re-feeding syndrome, sepsis, and both electrolyte deficiencies and excesses. Responding appropriately to this, in turn, will help to minimise the risk of complications.
Electrolytes (Sodium, Potassium & Magnesium), bone profile (Calcium & Phosphate), infection markers (such as C Reactive Protein and white blood cells) and liver function tests should be taken at baseline, reviewed daily until stable and then at each planned follow up.
Cholesterol and triglycerides should be reviewed weekly initially, reducing to 3 monthly once stable to monitor the risk of potential hyperlipidaemia.
Trace elements (zinc, copper, selenium and manganese) and vitamins (A, D, E, B12, Folate) should be checked at baseline if there is previous evidence of malnutrition. This should then be repeated 3 monthly in long term patients (NICE, 2006) to detect deficiencies or raised concentrations. It is important to interpret these results with caution and monitor clinical symptoms, as serum concentrations can be reduced or raised when inflammatory markers are raised during the acute phase response, and may not reflect total body stores.
Electrolyte disturbances
Electrolyte disturbances are a common complication of PN. Before altering the PN prescription, the following points should be considered:
- Trends – is the disturbance an acute or chronic issue?
- Clinical symptoms – some patients may become symptomatic at even mild disturbances and may need to be treated more aggressively.
- Establish the possible cause for disturbances e.g. re-feeding syndrome, GI losses, fluid overload, dehydration, medications, excessive replacement, IV therapy and clinical condition. Consider the composition of fluids lost by clinical condition to calculate PN electrolyte additions (NICE, 2013).
- What are the patients estimated requirements?
- What is the patient already receiving? e.g. through PN, enteral, IV therapy and other medications.
- Consider natural daily variation in electrolytes. These will require monitoring but do not always need to be acted upon.
| Electrolyte | Typical clinically significant adjustments |
|---|---|
| Sodium | Multiples of 40mmol. 50-100+mmol if severe GI losses/short bowel |
| Potassium | Multiples of 20mmol. May need 100+mmol/day in severe GI losses |
| Magnesium | Multiples of 5-10mmol. May need 15mmol or more in severe GI losses |
| Phosphate | Multiples of 10mmol |
| Calcium | Multiples of 2.5-5mmol |
Adapted from Austin and Stroud (2007)
Liver function tests (LFTs)
PN can contribute to abnormal LFTs; however, it is rarely the main cause. Factors such as sepsis, medications and underlying liver problems also lead to raised LFTs and must be taken into account.
Minimising risk of complications:
- Fat/lipid <1.5g/kg/day and change to an anti-inflammatory source. Long term PN may require lipid at 0.5-1.0g/kg/d.
- Do not exceed glucose oxidation rate.
- Do not over-feed energy or nitrogen. Gauge requirement on metabolic stress.
- Introduce even a small amount, ‘trophic’ / enteral feed if possible.
- Reduce PN to cyclical feeding e.g. 12-18hrs after 2 weeks of PN feeding.
- Liaise with the medical team regarding treatment of sepsis and review of medications.
References
ESPEN (2009) Guidelines on Parenteral Nutrition: Home Parenteral Nutrition (HPN) in adults patients.
NCEPOD (2010) PN: A mixed bag report. National confidential enquiry into patient outcome and death.
NICE (2006) Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition.
NICE (2013) Intravenous fluid therapy in adults in hospital.
Austin, P and Stroud, M (2007) Prescribing Adult Intravenous Nutrition. RPS publishing. London.
Rhys White in Todorovic V and Micklewright A (2011). The Parenteral and Enteral nutrition Group (2011) Pocket guide to clinical nutrition 4th Edition. British Dietetic Association
