3.3.2 Nutritional benefits of PN

This section summarises relevant studies reporting improved nutritional intake and/or nutritional status with PN. Functional and/or clinical benefits reported in these studies are summarised in Section 3.3.3 and Section 3.3.4.

3.3.2.1 NUTRITIONAL INTAKE

• Delivery of nutrition via the parenteral route is efficient, as research indicates that most patients prescribed PN receive their planned nutritional intake. For instance, data from the nutritionDay ICU survey, an annual one-day cross-sectional audit from 2007 to 2013, showed that 97% of patients prescribed PN received their planned nutritional intake.²²⁴

CRITICAL ILLNESS

Timely initiation of PN in hospital patients who cannot be fed adequately with enteral

• Doig and colleagues (2013) conducted a large multicentre single-blind RCT in Australia and New Zealand to evaluate the nutritional and clinical benefits of early PN in critically ill adults with a short-term relative contradiction to early ETF.¹⁴² A total of 1,372 surgical (65%) and medical (35%) patients admitted to the ICU were randomised to receive either pragmatic standard care (i.e., current practice in individual ICUs; n = 686) or PN provided within 24 hours of ICU admission (n = 686). Nine patients subsequently withdrew consent (4 standard care and 5 early PN). The mean time from ICU admission to enrolment was 13.8 hours. Of the 681 patients allocated to early PN, 679 (99.7%) started PN within 44 minutes of enrolment and 59.6% progressed to ETF within a mean of 3.83 days of starting PN. In total, 274 of 681 patients (40.2%) received ETF at some point during their ICU stay. Of the 682 patients who received pragmatic standard of care, 29.2% started ETF within a mean of 1.98 days after enrolment and 24.1% received supplemental PN (SPN) within 5.58 days after the start of ETF. Additionally, 27.3% initiated PN within 1.99 days after enrolment, with 43.0% progressing to ETF within 5.08 days after starting PN. Therefore, 40.8% of patients receiving standard care never received ETF or PN during their ICU stay (average 3.72 days). Patients who received early PN had significantly higher energy and amino acid/protein intakes on each of the first 6 days of admission to ICU after study enrolment (p values not reported).
• Heidegger and colleagues (2013) conducted an RCT (‘Swiss SPN study’) to assess whether delivering 100% of energy targets with SPN (ETF + PN) on days 4–8 of the ICU stay would optimise clinical outcome.¹⁴⁰ This study involved 305 medical and surgical ICU patients; patients who received <60% of their energy target on ETF alone on day 3 of ICU admission were enrolled and randomised to receive ETF alone or SPN. SPN significantly increased mean energy and protein delivery over days 4–8 (both p < 0.0001) compared with ETF alone; 103% and 100% of the energy and protein target, respectively, was achieved in the SPN group, compared with 77% and 71% in the ETF group.
• A cross-sectional retrospective observational study in eight Latin American countries found that patients receiving SPN (ETF + PN) were significantly more likely to achieve >90% of their daily energy and protein targets than patients receiving ETF alone (odds ratio [OR] 1.56; 95% CI 1.02–2.39; p = 0.038).²³⁰ SPN was associated with 64% and 56% increases, respectively, in the likelihood of achieving >90% of target daily energy and protein intake. Most patients (79.9%) received ETF alone, 9.4% received PN alone, and 10.7% received SPN. However, the authors argued that use of PN should have been higher, given that 74.1% of patients were assessed as having moderate or severe malnutrition and more than one-third had a contraindication or intolerance to ETF.
• The International Study Group of Pancreatic Surgery highlights that delayed gastric emptying and/or intestinal paralysis can occur after pancreaticoduodenectomy, leading to insufficient post-operative calorie intake and prolonged hospitalisation.²⁶⁵ Therefore, Probst and colleagues (2016) retrospectively evaluated the safety and efficacy of post-operative SPN in 69 consecutive patients who received pancreaticoduodenectomy between 2003 and 2012. Early SPN (ETF + PN) initiated immediately after surgery was safe and provided comprehensive coverage of nutritional needs during the post- operative period after pancreaticoduodenectomy.²⁶⁶ The median nutritional balance (i.e., coverage of calorie target per patient during hospitalisation) was 93.4%. Moreover, calorie targets were achieved for 71.3% of 1,516 patient-days and for 6 of the first 7 days after surgery, when catabolic stress is most intense.
• Kutsogiannis and colleagues (2011) reported an international multicentre observational study (29 countries) that evaluated the early use of SPN (ETF + PN) in 2,920 mechanically ventilated patients with GI dysfunction who spent more than 72 hours in the ICU.¹³⁴ Outcomes were compared for patients receiving early ETF alone, early SPN, and early ETF + late PN. The early SPN group were most likely to achieve energy and protein targets (81.2% and 80.1%, respectively vs 63.4% and 59.3% with ETF/late PN and 63.4% and 59.3% with early ETF; p < 0.0001).
• An international multicentre observational study by Cahill and colleagues (2011) evaluated the effects of timely initiation of PN on nutritional adequacy in critically ill patients who were not fed adequately with ETF.²⁶⁷ The analysis included data from 703 patients who spent >72 hours in the ICU and were eligible to receive ETF 48 hours after admission. Most patients (77%) received late ETF without PN. In patients receiving late ETF and PN, 11.8% received early PN and 11.2% received late PN. Patients receiving early PN were most likely to achieve adequate energy and protein intake (74.1% and 71.5%, respectively) whereas patients in the late ETF group were least likely to achieve adequate energy and protein intake (42.9% and 38.7%; p < 0.001).
• A systematic review and meta-analysis of 12 RCTs involving 5,543 patients in the acute phase of critical illness found that, although statistical pooling of results was not possible, patients receiving a combination of EN and PN received higher amounts of macronutrients compared to those receiving EN alone. Six trials reported significantly higher energy intake with combined EN and PN, and four trials showed significantly greater protein delivery in the combination group.²⁶⁸
• A systematic review and meta-analysis of five randomised controlled trials evaluated the clinical outcomes of combining SPN with EN compared to EN alone in critically ill adults. The results showed that protein intake was significantly higher in the SPN + EN group (SMD = 1.287, t = 4.371, p < 0.001), as was energy intake (SMD = 1.391, t = 8.097, p < 0.001). The authors concluded that adding SPN to EN improves both protein and energy intake, highlighting its benefit in cases where EN alone does not meet the nutritional needs of critically ill patients.¹²²