Opioid tolerance to sedation and analgesia

A randomized, controlled trial of immersive virtual reality analgesia, during physical therapy for pediatric burns

This randomized, controlled, within-subjects (crossover design) study examined the effects of immersive virtual reality as an adjunctive analgesic technique for hospitalized pediatric burn inpatients undergoing painful physical therapy. Fifty-four subjects (6-19 years old) performed range-of-motion exercises under a therapist's direction for 1-5 days. During each session, subjects spent equivalent time in both the virtual reality and the control conditions (treatment order randomized and counterbalanced). Graphic rating scale scores assessing the sensory, affective, and cognitive components of pain were obtained for each treatment condition. Secondary outcomes assessed subjects' perception of the virtual reality experience and maximum range-of-motion. Results showed that on study day one, subjects reported significant decreases (27-44%) in pain ratings during virtual reality. They also reported improved affect ("fun") during virtual reality. The analgesia and affect improvements were maintained with repeated virtual reality use over multiple therapy sessions. Maximum range-of-motion was not different between treatment conditions, but was significantly greater after the second treatment condition (regardless of treatment order). These results suggest that immersive virtual reality is an effective nonpharmacologic, adjunctive pain reduction technique in the pediatric burn population undergoing painful rehabilitation therapy. The magnitude of the analgesic effect is clinically meaningful and is maintained with repeated use.

The management of opioid-related sedation

There are many side effects of opioids used for cancer and non-cancer pain, which can limit their use and vastly undermine the quality of life for patients. Sedation is a frequent and serious side effect of opioid analgesics, sometimes reported as fatigue or tiredness from patients. There are a number of specific therapies to control or manage these adverse effects, making it feasible to dose opioids to adequate analgesia with tolerable side effects. The balance between effect and side effects is the goal of chronic opioid pharmacotherapy. In particular, sedation commonly can be problematic in a patient who is taking opioids, to the extent that one may want to discontinue the medication and suffer with the pain rather than experience debilitating fatigue or sedation. When sedation clinically becomes excessive, measures should be taken to make it possible to continue treatment with analgesics with acceptable sedation management. There are many techniques to oppose sedation including simple antidotes, such as rest, exercise, and timing of opioid medications, and more complex solutions, such as opioid rotation and the use of psychostimulants or other classes of medications to counteract sedation. The treatment of opioid-induced sedation can be very effective and should be part of a skill set that the clinician can easily employ to enhance the quality of life of patients.

Acetaminophen in cerebrospinal fluid in children

BACKGROUND

There are few studies describing acetaminophen (APAP) cerebrospinal fluid (CSF) concentrations in children. This current study was undertaken in children--from neonates to adolescents--in order to investigate age-related changes in the plasma to CSF equilibration half-time (Teq) of APAP.

METHODS

Children (n=41) 1 week to 18 years of age undergoing (semi) elective surgery for placement or revision of a ventriculo-peritoneal shunt or insertion of a temporary external ventricular drain received a loading dose of 30-40 mg/kg APAP 1 h before scheduled surgery. Blood and CSF samples for APAP concentration analysis were collected during surgery. In those children with a temporary external drain, blood and CSF sampling were extended into the postoperative period. APAP and CSF pharmacokinetics were estimated using non-linear mixed-effects models. Size was standardized to a 70-kg person using allometric "1/4 power models".

RESULTS

Median (25-75th percentile) age and weight of the patients included in this study were 12 months (3-62 months) and 10.0 kg (5.8-20.0 kg). Median (25-75th percentile) time between APAP loading dose administration and collection of blood samples and median time (25-75th percentile) between APAP loading dose and collection of CSF were, respectively, 125 min (95-210 min) and 133 min (33-202 min). The population mean Teq, standardized to a 70-kg person, was 1.93 h (CV 43%), an estimate similar to that described in adults (2.1 h). There was no relationship between age and Teq other than that predicted by size. APAP plasma concentrations ranged from 0.0 mg/l to 33.0 mg/l, APAP CSF concentrations ranged from 0.0 mg/l to 21.0 mg/l.

CONCLUSION

Size rather than blood-brain-barrier maturation determines Teq changes with age in children. We predict a neonate (3.5 kg), 1-year-old child (10 kg), 5-year-old child (20 kg), 10-year-old child (30 kg) and adult (70 kg) to have Teq values of 0.9, 1, 1.4, 1.6, and 1.93 h, respectively.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Effectiveness of virtual reality-based pain control with multiple treatments

OBJECTIVE

The current study explored whether immersive virtual reality continues to reduce pain (via distraction) with repeated use.

SETTING

The study was conducted in a burn care unit at a regional trauma center.

PATIENTS

Seven patients aged 9-32 years (mean age of 21.9 years; average of 23.7% total body surface area burned [range, 3-60%]) performed range-of-motion exercises of their injured extremity under an occupational therapist's direction on at least 3 separate days each.

INTERVENTION

For each physical therapy session, each patient spent equal amounts of time in virtual reality and in the control condition (no distraction). The mean duration of physical therapy in virtual reality was 3.5, 4.9, and 6.4 minutes for the first, second, and third session, respectively. Condition order was randomized and counter-balanced.

OUTCOME MEASURES

For each of the three physical therapy sessions, five visual analog pain scores for each treatment condition served as the dependent variables.

RESULTS

Pain ratings were statistically lower when patients were in virtual reality, and the magnitude of pain reduction did not diminish with repeated use of virtual reality. The results of this study may be examined in more detail at www.vrpain.com.

CONCLUSIONS

Although the small sample size limits generalizability. results provide converging preliminary evidence that virtual reality can function as a strong nonpharmacological pain reduction technique for burn patients during physical therapy. Results suggest that virtual reality does not diminish in analgesic effectiveness with three (and possibly more) uses. Virtual reality may also have analgesic potential for other painful procedures or pain populations. Practical implications are discussed.