Introduction

Wound healing can be a problem in SCI patients following major surgery. While this may be due to many reasons such as the lack of pressure sensation allowing undue pressure on wounds, we were concerned about the possibility of nutritional and or immune problems following SCI that may have an effect on wound healing. Our aim was to attempt to identify and quantitate differences in nutritional risk, nutritional proteins, and immunological response to vaccination between SCI patients and age and gender matched control subjects.

Method

Thirty past patients of the Spinal Injuries Unit, Burwood Hospital, Christchurch, New Zealand were identified and enrolled in the study. The patients had no intercurrent illnesses other than the known stable SCI. Age and gender matched controls were selected from non SCI hospital staff. Permission was obtained from the SCI participants to retrieve data relating to their injury from hospital case notes. All SCI patients were otherwise well, all were injured more than one year previously and had no current problems such as chronic pressure ulcers.

Nutritional status was assessed by generating a Nutritional Risk Score (NRS, Appendix 11,2 and drawing blood for full blood count, iron studies, red blood cell folate, vitamin B12, ferritin, magnesium, and zinc. Immune status was assessed by vaccination response index (VRI) to Pneumovax 23 vaccine. The vaccine was administered intramuscularly. The post vaccination specimen was taken 14 days post operatively in all cases.

Informed consent was obtained from all participants prior to enrolment, drawing of blood and administration of Pneumovax. The study had ethical approval from the Canterbury Ethics Committee, Christchurch. Non parametric statistical analysis was undertaken to be Wilcoxon test (paired). Significance was assumed at (P<0.05).

Results

The mean age of the SCI participants was 44 years (range 22–67 years), four female and 26 male, and were matched with age, gender matched controls). Twenty SCI patients had cervical injuries (C3-C7, 10 SCI patients had thoracic injuries (T11-T12).

Full blood count, iron studies, and testing for red blood cell folate, total protein, albumin, prealbumin, vitamin B12, ferritin, magnesium and zinc was performed. Median results for each group and normal ranges are presented in Table 1. Results were not outside the normal laboratory range for either group, however the SCI group had significantly different median values than controls (P<0.01) for haemoglobin concentration, white blood cell count, albumin, prealbumin, serum iron and % saturation.

Table 1 Median values and normal range for blood parameters measured in SCI patients (n=30) and age and gender matched controls (n=30)
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Body mass index

Median weight for SCI participants was 65.5 kg (range 50–93 kg) compared to 80 kg (range 60–108 kg) for the control group. Mean body mass index (weight kg/(height cm2) 22.2 (range 15–30) for the SCI group, significantly less than the paired control group BMI of 26 (range 20–32, P=0.0004).

Nutritional risk score

Median NRS for SCI patients was 2 (range 0–6), compared to 0 (range 2–4) for paired controls. There is a significant difference in NRS between groups: P<0.0001. Scores ranged from 0 to 2 for each of the five NRS components for the SCI patients and 0 to 3 for the control group.

Immunoglobulin response

Response to Pneumovax 23 vaccine was assessed by calculating the pre/post vaccination ratio for IgG, IgA, and IgM (Table 2). There was no significant difference between SCI patients and the control group for any value, with all ratios lying within the normal laboratory ranges. There was no significant difference between SCI patients and controls, nor for cervical injury SCI patients compared with those with thoracic injuries.

Table 2 Immunoglobulin response to Pneumovax 23 vaccine for SCI patients (n=30) and age and gender matched controls (n=30)
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Discussion

Our results show a significant difference in certain nutritional parameters between healthy SCI patients and age and sex matched controls. SCI patients are lighter and have lower nutritional index scores. There was a significant difference between the two groups, with SCI patients more likely to fall in the `needs monitoring' (scores 4–5) group. Previous studies have suggested that indicators of nutritional function such as zinc and prealbumin have been shown to be low in SCI patients with pressure ulcers.3,4 None of the SCI patients in our study had pressure ulcers and median blood levels of zinc and prealbumin were inside the normal range.

There is some evidence for changes in immune function following SCI,5 including an impaired lymphocyte proliferation response in patients with complete SCI when compared with neurologically intact controls.6 These changes may be mediated by the autonomic nervous system and be dependent upon the neurological level.6 We found no significant difference in the ability of the SCI patients to mount an antibody response to the Pneumovax vaccine when compared to normal controls and did not demonstrate any association of strength of response with neurological level. This is consistent with responses to the trivalent 1994–1995 influenza vaccine reported previously.7

Pneumococcal vaccine responses have been shown to be impaired in immunocompromised patients in a variety of clinical settings.8,9,10 The implication of the Pneumovax response is that in healthy SCI patients both the afferent (antigen processing and presentation) and efferent (effector) limbs of the immune system remain globally intact. This appears to include the ability to mount both T-independent responses (i.e. the IgM response to pneumococcal polysaccharides) and T-dependent (IgG and IgA) responses. However, subtle changes in immune cell function and IgG isotype secretion have not been excluded by this simple study.

Screening SCI patients for nutritional risk factors is unlikely to be useful to identify those with nutritional problems unless there is a clinical suggestion of a problem. In this situation addressing nutritional problems early may be useful in reducing the incidence of complications such as pressure ulcers. Further work could be done to investigate the relationship of impaired nutrition to immune function in SCI patients.