Forty-nine studies (n=2,571) assessed efficacy. These were all either case series or case studies (the number of participants by study design was not reported). A further 34 studies provided information on intrathecal therapy, such as side-effects, complications, costs and patient selection criteria, but did not specifically measure efficacy.
Measurement of effectiveness by combining VAS pain scores.
Sixteen studies presented both pre- and post-therapy VAS scores. The results showed a substantial drop in pain score from 7.6 pre-therapy to 3.0 post-therapy. A further 27 studies used VAS pain scores, but pain was only measured after pump implantation. All of these studies showed some evidence of improvement after the use of intrathecal pumps, based on the authors' claims that there was an improvement as a result of the intervention.
Assessment of non-VAS pain scores.
The results of the pain rating intensity (PRI) on the MPQ showed a significant improvement in the overall PRI after 3 months (1 study). This was sustained for 18 months, but reduced slightly after 24 months from the beginning of therapy. The results on the individual sensory subscale of the MPQ (MPQ-s) showed an immediate improvement that was sustained over an 18-month period, but was followed by a return to baseline levels in the final 6 months. No significant differences were shown on either the individual affective subscale of the MPQ (MPQ-a) or the individual evaluative subscale of the MPQ (MPQ-e).
Use of supplemental analgesia (7 studies).
Six of the 7 studies reported a decrease in both the number and quantity of supplemental analgesics used, with 5 studies assigning this decrease as a percentage. The percentage decrease ranged from 15 to 50%. The decreases were observed for both opioids and non-opioids.
Functional assessment.
Ten studies reported on functional assessment outcomes such as daily activities, functional capacity and ability to return to work since undergoing therapy. All of the studies showed some functional improvement.
Sleep pattern.
The impact of the therapy on sleep patterns was assessed in 4 studies. These all suggested an increase in the number of hours patients were able to sleep when using intrathecal pump systems.
Gait.
Three studies assessed the effect on gait. The results were disparate: one study showed a statistically significant improvement, another showed no improvement, and the third showed minimal improvement.
Patient satisfaction or acceptability.
Five studies assessed patient satisfaction with treatment or acceptability of treatment. All 5 studies indicated that the majority of patients rated the treatment as acceptable (range: 77 to 92%). One study also assessed the views of clinical staff and spouses, as well as those of the patients. Whilst 77% of the patients rated the therapy as good, only 55% of the spouses rated the therapy as good to excellent compared with 100% of clinical staff.
Cancer versus non-cancer pain.
The use of intrathecal pumps in patients with non-malignant pain was specifically investigated in 5 studies. Four of these studies showed a beneficial effect of the therapy. The results of the last study indicated that intrathecal therapy was not useful in failed, back surgery patients.
Pharmacological side-effects.
The major side-effects reported in the studies were nausea and vomiting (25%; 17 studies), sedation and somnolence (17%; 11 studies), urinary retention (18%; 20 studies), pruritis (17%; 11 studies) and respiratory depression (3%; 10 studies). The other less frequently reported side-effects were amenorrhoea, altered libido, constipation, oedema, opioid overdose, polyarthralgia, provocation of asthma, parenteral abuse of opioids, sweating and incontinence.
Mechanical complications.
Fourteen meningitis cases (3%) were reported in a total of 454 patients. There were no deaths related to catheter-associated meningitis. When combining all data from the 16 studies that reported on catheter dislodgement, an overall incidence of between 5 and 18% was shown. Dislodgement of 18% of type 4 pumps (totally implanted intrathecal catheter with implanted infusion pump) was higher than for both type 5 pumps (13%; totally implanted intrathecal catheter with implanted programmable infusion pump) and type 2 pumps (5%; totally implanted intrathecal catheter with subcutaneous injection port).