Patients' expectations of patient-controlled analgesia

Subcutaneous Patient-Controlled Analgesia in Home-Based Palliative Care: "It's as Straightforward as Pushing a Button, Right at my Fingertips"

Subcutaneous patient-controlled analgesia (SCPCA) in home-based palliative care is a potentially valuable option for providing effective pain relief to some patients, particularly when conventional analgesic approaches prove ineffective or are refused. Our case report illustrates the use of SPCA for the management of breakthrough pain in a patient receiving palliative care at home with no improvement after multiple previous treatments. SCPCA was found to be safe and successful. Future research is essential to explore its precise role, appropriate indications, prescription guidelines, and safety considerations across various palliative care contexts.

Patient-controlled analgesia for the management of adults with acute trauma in the emergency department: A systematic review and meta-analysis

BACKGROUND

Patient-controlled analgesia (PCA) has potential as a form of analgesia for trauma patients in the emergency department (ED). The objective of this review was to evaluate the effectiveness and safety of PCA for the management of adults with acute traumatic pain in the ED. The hypothesis was that PCA can effectively treat acute trauma pain in adults in the ED, with minimal adverse outcomes and better patient satisfaction compared with non-PCA modalities.

METHODS

MEDLINE (PubMed), Embase, SCOPUS, ClinicalTrials.gov , and Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched from inception date to December 13, 2022. Randomized controlled trials involving adults presenting to the ED with acute traumatic pain who received intravenous (IV) analgesia via PCA compared with other modalities were included. The Cochrane Risk of Bias tool and the Grading of Recommendation, Assessment, Development, and Evaluation approach were used to assess the quality of included studies.

RESULTS

A total of 1,368 publications were screened, with 3 studies involving 382 patients meeting the eligibility criteria. All three studies compared PCA IV morphine with clinician-titrated IV morphine boluses. For the primary outcome of pain relief, the pooled estimate was in favor of PCA with a standard mean difference of -0.36 (95% confidence interval, -0.87 to 0.16). There were mixed results concerning patient satisfaction. Adverse event rates were low overall. The evidence from all three studies was graded as low-quality because of a high risk of bias from lack of blinding.

CONCLUSION

This study did not demonstrate a significant improvement in pain relief or patient satisfaction using PCA for trauma in the ED. Clinicians wishing to use PCA to treat acute trauma pain in adult patients in the ED are advised to consider the available resources in their own practice settings and to implement protocols for monitoring and responding to potential adverse events.

LEVEL OF EVIDENCE

Systematic Review/Meta-Analyses; Level III.

Perioperative pain management in COVID-19 patients: Considerations and recommendations by the Saudi Anesthesia Society (SAS) and Saudi Society of Pain Medicine (SSPM)

The COVID-19 pandemic has swept across the world over the past few months. Many articles have been published on the safety of anesthetic medications and procedures used in COVID-19 positive patients presenting for surgery. Several other articles covered the chronic pain management aspect during the pandemic. Our review aimed to focus on perioperative pain management for COVID-19 patients. We conducted a literature search for pertinent recent articles that cover considerations and recommendations concerning perioperative pain management in COVID-19 patients. We also searched the literature for the relevant adverse effects of the commonly used medications in the treatment of COVID-19, and their potential drug-drug interactions with the common medications used in perioperative pain management. Professional societies recommend prioritizing regional anesthesia techniques, which have many benefits over other perioperative pain management options. When neuraxial and continuous peripheral nerve block catheters are not an option, patient-controlled analgesia (PCA) should be considered if applicable. Many of the medications used for the treatment of COVID-19 and its symptoms can interfere with the metabolism of medications used in perioperative pain management. We formulated an up-to-date guide for anesthesia providers to help them manage perioperative pain in COVID-19 patients presenting for surgery.

Comparison of diclofenac gel, ibuprofen gel, and ibuprofen gel with levomenthol for the topical treatment of pain associated with musculoskeletal injuries

Objective

To determine whether 3% w/w levomenthol added to ibuprofen gel (5% w/w) improves its efficacy compared with ibuprofen gel alone or diclofenac gel (1.16%) for the treatment of soft-tissue injuries.

Methods

A total of 182 patients with acute soft-tissue injuries participated in a randomised, single-blind, single-dose study to assess the efficacy and safety of three topical analgesic gels. Efficacy was assessed as the score change in a numeric rating scale for pain.

Results

The median time to significant pain relief was 20 minutes for the ibuprofen/levomenthol and diclofenac gels but 25 minutes for ibuprofen gel. At 2 hours, significantly more patients treated with ibuprofen/levomenthol gel reported a cooling sensation (45.8%) compared with diclofenac (16.4%) or ibuprofen (14.7%) gels, and both ibuprofen/levomenthol and diclofenac gels provided significantly more effective global pain relief compared with ibuprofen gel. Few adverse events and no serious adverse events related to study medication were recorded.

Conclusions

Although all gels effectively relieved pain, both ibuprofen/levomenthol and diclofenac gels provided superior global pain relief compared with ibuprofen gel, with a shorter median time to significant pain relief. Only ibuprofen/levomenthol gel provided cooling for up to 2 hours. None of the gels were associated with serious safety concerns. EudraCT No 2015-005240-33 EU Clinical Trials Register URL: https://www.clinicaltrialsregister.eu/ctr-search/search

The efficacy of elastomeric patient-control module when connected to a balloon pump for postoperative epidural analgesia: A randomized, noninferiority trial

When considering the principles of a pain control strategy by patients, reliable administration of additional bolus doses is important for providing the adequate analgesia and improving patient satisfaction. We compared the efficacy of elastomeric patient-control module (PCM) with conventional PCM providing epidural analgesia postoperatively.A noninferiority comparison was used. Eighty-six patients scheduled for open upper abdominal surgery were randomized to use either an elastomeric or conventional PCM connected to balloon pump. After successful epidural catheter insertion at T6-8 level, fentanyl (15-20 μg/kg) in 0.3% ropivacaine 100 mL was administered at basal rate 2 mL/h with bolus 2 mL and lock-out time 15 minutes. The primary outcome was the verbal numerical rating score for pain.The 95% confidence intervals for differences in pain scores during the first 48 hours postoperatively were <1, indicating noninferiority of the elastomeric PCM. The duration of pump reservoir exhaustion was shorter for the elastomeric PCM (mean [SD], 33 hours [8 hours] vs 40 hours [8 hours], P = 0.0003). There were no differences in the frequency of PCM use, additional analgesics, or adverse events between groups.The elastomeric PCM was as effective as conventional PCM with and exhibited a similar safety profile.

Effect of nitrous oxide on fentanyl consumption in burned patients undergoing dressing change

BACKGROUND AND OBJECTIVES

Thermal injuries and injured areas management are important causes of pain in burned patients, requiring that these patients are constantly undergoing general anesthesia for dressing change. Nitrous oxide (N2O) has analgesic and sedative properties; it is easy to use and widely available. Thus, the aim of this study was to evaluate the analgesic effect of N2O combined with fentanyl in burned patients during dressing change.

METHOD

After approval by the institutional Ethics Committee, 15 adult burned patients requiring daily dressing change were evaluated. Patient analgesia was controlled with fentanyl 0.0005% administered by intravenous pump infusion on-demand. Randomly, in one of the days a mixture of 65% N2O in oxygen (O2) was associated via mask, with a flow of 10 L/min (N2O group) and on the other day only O2 under the same flow (control group).

RESULTS

No significant pain reduction was seen in N2O group compared to control group. VAS score before dressing change was 4.07 and 3.4, respectively, in N2O and control groups. Regarding pain at the end of the dressing, patients in N2O group reported pain severity of 2.8; while the control group reported 2.87. There was no significant difference in fentanyl consumption in both groups.

CONCLUSIONS

The association of N2O was not effective in reducing opioid consumption during dressing changes.

Patient perspectives of patient-controlled analgesia (PCA) and methods for improving pain control and patient satisfaction

BACKGROUND AND OBJECTIVES

This study aimed to (1) identify patient-controlled analgesia (PCA) attributes that negatively impact patient satisfaction and ability to control pain while using PCA and (2) obtain data on patient perceptions of new PCA design features.

METHODS

We conducted a prospective survey study of postoperative pain control among patients using a PCA device. The survey was designed to evaluate patient satisfaction with pain control, understanding of PCA, difficulties using PCA, lockout-period management, and evaluation of new PCA design features.

RESULTS

A total of 350 eligible patients completed the survey (91%). Patients who had difficulties using PCA were less satisfied (P < 0.001) and were more likely to feel unable to control their pain (P < 0.001). Satisfaction and self-reported ability to control pain were not affected by patient education about the PCA. Forty-nine percent of patients reported not knowing if they would receive medicine when they pushed the PCA button, and of these, 22% believed that this uncertainty made their pain worse. The majority of patients preferred the proposed PCA design features for easier use, including a light on the button, making it easier to find (57%), and a PCA button that vibrates (55%) or lights up (70%), alerting the patient that the PCA pump is able to deliver more medicine.

CONCLUSIONS

A majority of patients, irrespective of their satisfaction with PCA, preferred a new PCA design. Certain attributes of current PCA technology may negatively impact patient experience, and modifications could potentially address these concerns and improve patient outcomes.

Patient-Controlled Analgesia with Fentanyl for Burn Dressing Changes

In this randomized, double-blinded study in 60 ASA I or II adults with >20% body-surface area thermal burns, we investigated the feasibility of patient-controlled analgesia (PCA) with fentanyl for pain management during dressing changes and determined the optimal PCA-fentanyl demand dose. An initial loading dose of IV fentanyl 1 microg/kg was administered. Patients received on-demand analgesia with fentanyl (10, 20, 30, and 40 microg) whenever their visual analog scale (VAS) score was >2. Mean VAS scores in the 10 and 20 microg groups (7.73 +/- 1.33 and 7.20 +/- 1.21, respectively) were significantly higher than those in the 30 and 40 microg groups (4.47 +/- 0.83 and 3.90 +/- 0.63, respectively) (all P = 0.000). Demand/delivery ratios were significantly larger in the 10 and 20 microg groups (3.03 +/- 1.06 and 2.54 +/- 0.49, respectively) than those in the 30 and 40 microg groups (1.36 +/- 0.34 and 1.37 +/- 0.36, respectively) (all P = 0.000). VAS scores and demand/delivery ratios were comparable in the 30 and 40 microg groups (P = 0.260 and P = 0.977, respectively), which suggests comparable analgesic efficacy. There was no hemodynamic instability or respiratory depression. The optimal demand dose of PCA-fentanyl was 30 microg (5-min lockout interval) after an initial loading dose of IV fentanyl 1 microg/kg.

Pre-operative information and patient-controlled analgesia: much ado about nothing

We examined whether pre-operative information benefited patients receiving patient-controlled analgesia (PCA) after major surgery. We investigated whether patients felt better informed about PCA and also whether pre-operative information altered the use of PCA, the adequacy of pain relief, worries about addiction and safety, and knowledge of side-effects. We investigated the effectiveness of information provided in two ways, namely by a patient-determined leaflet or an interview by a trained nurse from the pain team, compared with routine pre-operative information. We studied 225 patients, 75 in each group. Patients in the leaflet group were better informed about PCA, became familiar with using PCA more quickly and were less confused about PCA than the control group. However, there were no effects on pain relief, worries about addiction and safety, and knowledge of side effects. The pre-operative interview resulted in no benefits. Our findings indicate that the detailed provision of pre-operative information failed to improve patients' experiences of PCA.

Patient-controlled analgesia: what information does the patient want?

AIMS OF THE STUDY

To formulate and evaluate an information leaflet for patients using patient-controlled analgesia (PCA), incorporating information thought to be important by patients.

RATIONALE

The benefit of current information leaflets, written by professionals, has not been studied and their value to patients is unknown.

BACKGROUND

Previous studies have shown that information leaflets were poorly designed and written in language too difficult for patients to understand.

RESEARCH METHODS

Seven focus groups were conducted to establish what information patients wanted to know about PCA. This information was incorporated into a new information leaflet. One hundred patients were randomized to receive either the new leaflet or the old leaflet in current use. A questionnaire was used to establish whether the new leaflet was more clear and informative than the old one.

RESULTS

Patients wanted to know that the drug used in PCA was morphine. They wanted more information about side-effects, needed to be reassured that it was safe, and that they could not overdose or become addicted. They wanted detailed instructions and diagrams about the technique. The questionnaire study established that the new leaflet was clearer and more informative.

CONCLUSION

Patients' contribution led to major change, producing a leaflet which was clearer, more attractive, more informative and which proved more satisfactory to patients.

Satisfaction With Epidural and Intravenous Patient-Controlled Analgesia

OBJECTIVE

Postoperative intravenous (i.v.) versus epidural morphine patient-controlled analgesia (PCA) were compared regarding maintenance of initial PCA route, pain levels, side effects, and levels of satisfaction. Additionally, the role of preoperative attitudinal expectations in predicting postoperative levels of satisfaction with pain management as well as maintenance of initial PCA route was evaluated.

DESIGN

After either abdominal or thoracic surgery, 70 eligible patients were randomized to receive morphine either through an epidural route (n = 37) or an intravenous PCA pump (n = 33).

SETTING

A large tertiary university teaching hospital in a major northeastern city.

OUTCOME MEASURES

Patients completed visual analogue rating scales 1 week before surgery regarding attitudes such as expectations of satisfaction with pain management after surgery and expectations of medication efficacy postsurgically. Postoperatively, beginning the day after surgery, patients were asked to complete visual analogue rating scales every 12 hours until they were discharged, for a maximum of 3 postoperative days. The scales evaluated included pain, ability to think, and satisfaction with pain control.

RESULTS

There were no significant between-group differences on the postoperative visual analogue scales. Although the overall rate of changing the initial PCA route to which the patients were randomized was identical for both groups (30%), those patients who had thoracic surgery changed their route of PCA administration significantly less when their initial PCA route was epidural (20%) than when their initial PCA route was i.v. (46%) (P <.05). Patients who were satisfied with pain control postoperatively were more likely to have been started on i.v. PCA (P =.001), have lower preoperative expectations of postoperative satisfaction with pain (P <.001), and have higher preoperative expectations of medication effects on postoperative pain (P <.001). Additionally, older patients (P =.007) and patients with lower preoperative expectations of postoperative satisfaction with pain (P =.003) were more likely to adhere to their initial treatment protocol.

CONCLUSIONS

Both techniques, i.v. and epidural PCA, result in high levels of satisfaction. Satisfaction with PCA can be accurately predicted in nearly three of four patients based on initial PCA route and preoperative attitudes. Additionally, maintaining the initial treatment plan can be accurately predicted based on age and preoperative attitudes. Patient expectations about pain relief should be addressed preoperatively, particularly with younger patients, for optimal results.

Implementation of research findings to reduce postoperative pain at night

This study was designed to introduce and evaluate a research-based intervention to improve night-time pain management. It involved the provision of patient information and the introduction of structured night-time pain assessment. The implementation of the intervention was undertaken by local opinion leader. The study involved 417 patients from two matched orthopaedic wards in a before and after trial with comparison group. Outcomes of night-time pain control were elicited from ward documentation and patients by structured interviews on the second postoperative morning. These incorporated retrospective pain assessments, analgesic provision and nursing comfort measures provided the previous night. The intervention was associated with statistically significant reductions in both average and worst overnight pain scores. The frequency of night-time pain assessment by nursing staff increased significantly, although patients did not volunteer reports of pain more frequently and analgesics and other comfort measures were no more frequent. The intervention required an investment in educational support but no additional resources were needed for the successful reduction in pain scores.

Fentanyl delivery from an electrotransport system: delivery is a function of total current, not duration of current

This open-label, parallel study of 28 men was conducted to evaluate the pharmacokinetics and safety of fentanyl delivered by the E-TRANS (fentanyl) electrotransport transdermal system (ALZA Corporation, Palo Alto, CA). The E-TRANS (fentanyl) system provided electrically assisted, transdermal, continuous delivery of fentanyl. Treatments consisted of no current (group A); a constant current of 100 microA for 26 hours plus 4 additional doses at varying currents for varying times during hour 25 (groups B, C, D); a constant current of 100 microA for 26 hours plus 4 additional doses at 1,200 microA over 2.5 minutes during hour 1 (group E); or 500 microA for 0.5 hours and 100 microA for 3.5 hours (group F). No fentanyl was detected in serum when no current had been applied. Mean serum fentanyl concentrations were similar regardless of current duration during hour 25 (treatments B, C, D). Increases in mean serum fentanyl concentrations were significantly lower during additional dosing for treatment E compared with treatments B, C, and D. Serum fentanyl concentrations sufficient for analgesia (1-3 ng/mL) were attained in treatments using the E-TRANS (fentanyl) system with basal current of 100 microA for 26 hours. There were no safety issues after treatment with E-TRANS (fentanyl) system with concurrent opioid antagonist (naltrexone) administration. The only adverse event requiring treatment was a headache (n = 1). The majority of subjects had no or barely perceptible erythema at the application site 24 hours after system removal. Application of E-TRANS (fentanyl) resulted in therapeutically significant serum fentanyl concentrations over a range of applied currents. Overall serum fentanyl concentrations were higher when the skin had been primed by constant-current fentanyl delivery.

Preoperative education and outcome of patient controlled analgesia

PURPOSE

To determine the effect of intensive preoperative education on the outcome of Patient Controlled Analgesia (PCA) postoperatively.

METHODS

This prospective randomised study was carried out in a single teaching hospital over three months. One group of patients (n = 42) received a 20 min standardised tutorial regarding PCA use from a single investigator and the other group (n = 43) received no additional education apart from the routine preoperative anaesthetic consultation. A blinded investigator assessed the patients following surgery. Pain scores and morphine consumption, patient satisfaction, side-effect profile and anti-emetic use were recorded at six, 24 and 48 hr postoperatively.

RESULTS

Pain scores, satisfaction scores and morphine consumption were similar in both groups throughout the study period. Fewer patients in the tutored group complained of nausea from 6 to 24 hr than did untutored patients (28% vs 51%; P < 0.05). More tutored patients used antiemetic medication from 0 to 6 (28% vs 12%; P < 0.05) and 6 to 24 hr (37% vs 19%; P < 0.05). Side effect profile and requirement for rescue analgesia was otherwise similar in both groups.

CONCLUSION

Our results suggest that specific preoperative education of patients using PCA does not alter pain scores, morphine consumption or patient satisfaction but may result in earlier and more effective use of anti-emetic medication.

Patient-controlled analgesia: an assessment by 200 patients

Two hundred patients completed a questionnaire about their experiences of patient-controlled analgesia. The questionnaire covered the following topics: pre-operative information, reasons for pressing and not pressing the button, pain relief, side-effects, safety, advantages and disadvantages of patient-controlled analgesia, worries associated with its use and control over pain. A high level of satisfaction with the device, together with a view that it afforded control over pain, emerged from replies to simple, general questions. However, more detailed questions revealed side-effects and fears that constrained its use and hence patients' ability to control pain. Control is predominantly a feature of the professional's view of patient-controlled analgesia, rather than the patient's experience of this analgesic technique.

Use of patient-controlled analgesia with alfentanil for burns dressing procedures: a preliminary report of five patients

The use of patient-controlled analgesia with alfentanil (PCA-alfentanil) as a form of pain relief for dressing procedures in patients during the acute phase of their burn injuries was investigated. Five ASA 1 and 2 patients with 10-30 per cent total body surface area (TBSA) thermal burns, had PCA-alfentanil for their dressing procedures after standard fluid resuscitation. One patient who did not receive a loading dose and a background infusion of alfentanil had unsatisfactory pain relief. Four patients had good pain relief after a loading dose of IV alfentanil 1 mg followed by a continuous background infusion of 200-800 micrograms/h. Demand dose ranged from 200 to 400 micrograms and lockout time ranged from 1 to 3 min. The total dose of alfentanil delivered ranged from 0.8 to 4.48 mg and duration of the dressings ranged from 30 to 60 min. All patients were mildly sedated, calm, communicative and cooperative during dressing procedures. None of them experienced hypotension or respiratory depression. One patient experienced nausea but no vomiting, no other adverse effects of alfentanil were noted. From the pilot study, PCA-alfentanil may be an effective form of pain relief for dressing procedures in patients during their acute phase of burn injuries. The optimal PCA-alfentanil setting has yet to be determined.

Attitudes to pain and pain relief in adult surgical patients

Pain relief after surgery is frequently inadequate. In the last few years much research has been devoted to improving the situation. Unfortunately, very little work has been undertaken to explore the patients' contribution to pain management. The beliefs and attitudes held by patients when they enter the hospital environment may be responsible in some instances for their not achieving optimal pain relief from the available techniques. We have studied some of these attitudes with a survey of 180 adult patients admitted for elective surgery. We found that most patients still expect pain following surgery. However, they are not afraid to ask for analgesics when in pain and do not attribute pain to their own wrong doing. There are, however, some patients who appear to have 'deviant' pain beliefs that could hinder their appropriate use of analgesics. Sadly, it is impossible to identify these patients according to age, gender, socio-economic group or previous experience of pain or surgery.

New developments in patient-controlled postoperative analgesia

Patient-controlled analgesia (PCA) is a newer technique for pain management. Patients are allowed to self-administer small analgesic bolus doses into a running intravenous infusion, intramuscularly, subcutaneously or even into the epidural space. Demands are usually controlled by computer-driven infusion pumps, but can also be delivered by disposable devices. Clinical experience demonstrates that individual variability in pain sensitivity and analgesic needs are of utmost importance. In contrast to earlier expectations, opioid consumption is usually higher than with restrictive conventional dosing regimes, but without an increase in serious side effects. Patients' acceptance is generally enthusiastic because of the possibility of self-control. PCA has proved its importance for pain studies, e.g. for algesimetry, to determine predictors of postoperative pain, to describe drug interactions, to evaluate the concept of pre-emptive analgesia or for pharmacokinetic designs. It is concluded that PCA results have been urgently required in order to change the mind of physicians and nursing staff with respect to individual pain management strategies. Once this goal is achieved, PCA concepts should also be used for the improvement of more conventional techniques.

[Introducing patient-controlled analgesia in a private hospital]

Patient controlled analgesia (PCA) is now a well recognized technique for postoperative analgesia. This study reports an experience of 24 months with 768 patients in a French private hospital. The first step was to train the team for this new technique. The second step was to agree on standards of prescription and safety monitoring rules (respiratory rate plus sedation score), as well as on the selection of patients. Analgesia was obtained with self administrated bolus plus a constant infusion (0.5 milligram per hour) of morphine in all patients, and in some with an addition of paracetamol or ketoprofene for a sparing effect on morphine consumption. All patients were returned to their ward, after an initial titration of pain treatment in the recovery room. No major problems occurred during the study period. In 13 patients the respiratory rate decreased to or under 10 c.min-1 without increased sedation and for safety reasons, the PCA was discontinued. PCA is now routinely used postoperatively for a majority of painful procedures in our institution.

Patient satisfaction with intravenous PCA or epidural morphine

In many institutions postoperative patients may receive morphine for analgesia administered into the epidural space, epidural opioid analgesia (EOA), or through intravenous self-administered patient-controlled analgesia pumps (PCA). Although a number of studies have compared the two approaches with regard to efficacy and side effects, there is less known with regard to patient satisfaction and its sources. In this study, 711 patients using PCA morphine and 205 patients receiving epidural morphine following a variety of gynaecological, urological, orthopaedic, and general surgical procedures rated their satisfaction with the method they used on a 0-10 verbal analogue satisfaction scale (0 = very dissatisfied; 10 = very satisfied). A consecutive subset of 100 patients (50 from EOA group and 50 from the PCA group) underwent further evaluation to identify advantages and disadvantages of the technique used which contributed to their satisfaction and/or dissatisfaction. Overall satisfaction (mean +/- SD) in the two large groups was 8.6 +/- 1.8 for PCA and 9.0 +/- 1.5 for EOA (P < 0.01). In the subset of 100 patients, there were differences between the EOA and PCA groups with regard to the advantages and disadvantages selected. Patients in the PCA group identified "personal control" and "method worked quickly" as advantages whereas patients receiving EOA selected "clear mind," "effective relief resting," and "effective relief while moving or coughing." The single disadvantage identified more frequently by PCA patients was "pain immediately after surgery before method became effective." Disadvantages identified more frequently by EOA patients were "side effects" and "poor pain relief." We conclude that overall patient satisfaction was high whether patients received PCA or EOA.(ABSTRACT TRUNCATED AT 250 WORDS)

Patient-controlled analgesia: can it be made safer?

Patient-controlled analgesia (PCA) has been shown to provide superior pain relief when compared with standard therapy options for postoperative analgesia. If PCA is to be implemented widely in teaching, private and country hospitals, its effectiveness needs balanced with a high safety profile. This can be achieved by consideration of patient selection, comprehensive education of patients, medical and nursing staff and equipment familiarisation. Continuous clinical audit allows identification of problem areas along with monitoring analgesic efficacy.