Management of burn pain in children

Cannabinoid receptor type 1 antagonist, AM251, attenuates mechanical allodynia and thermal hyperalgesia after burn injury

BACKGROUND

Burn injury causes nociceptive behaviors, and inflammation-related pathologic pain can lead to glial cell activation. This study tested the hypothesis that burn injury activates glial cells, and cannabinoid receptor 1 (CB1R) antagonist, AM251, will decrease burn pain.

METHODS

Anesthetized rats received 0.75-cm third-degree burn on dorsal hind paw. Vehicle or AM251 30 μg intrathecally (older rats, n=6 per group) or, either vehicle, 0.1 or 1.0 mg/kg intraperitoneally (younger rats, n=6 per group), started immediate postburn, was administered for 7 days. Mechanical allodynia and thermal hyperalgesia were tested on ventral paw for 14 days. Microglial and astroglial activity was assessed by immunocytochemistry.

RESULTS

Allodynia, observed on burn side from day 1 to 14, was significantly (P<0.05) attenuated by intrathecal and intraperitoneal AM251 (1 mg/kg) starting from 3 to 14 days. Hyperalgesia, observed from day 3 to 12, was completely (P<0.05) reversed by intrathecal and intraperitoneal AM251 (1 mg/kg). AM251 0.1 mg/kg had no effect. Microglial activity (n=3 per time point) increased (P<0.05) 18.5±7.5 and 12.3±1.6 (mean±SD) fold at 7 and 14 days, respectively. Astroglial activity (n=4 per time point) increased 2.9±0.3 fold at day 7 only. Glial activities were unaltered by AM251.

CONCLUSIONS

AM251 inhibited nociceptive behaviors after burn even beyond 7-day period of administration. Although many studies have documented the utility of CB1R agonists, this study indicates that endogenous cannabinoids may have an unexpected pronociceptive effect during development of burn pain, explaining why CB1R antagonist, AM251, improves nociceptive behaviors. The decreased nociception with AM251 without altering glial activity indicates that AM251 acts further downstream of activated glial cells.

Acute and perioperative care of the burn-injured patient

Care of burn-injured patients requires knowledge of the pathophysiologic changes affecting virtually all organs from the onset of injury until wounds are healed. Massive airway and/or lung edema can occur rapidly and unpredictably after burn and/or inhalation injury. Hemodynamics in the early phase of severe burn injury is characterized by a reduction in cardiac output and increased systemic and pulmonary vascular resistance. Approximately 2 to 5 days after major burn injury, a hyperdynamic and hypermetabolic state develops. Electrical burns result in morbidity much higher than expected based on burn size alone. Formulae for fluid resuscitation should serve only as guideline; fluids should be titrated to physiologic endpoints. Burn injury is associated basal and procedural pain requiring higher than normal opioid and sedative doses. Operating room concerns for the burn-injured patient include airway abnormalities, impaired lung function, vascular access, deceptively large and rapid blood loss, hypothermia, and altered pharmacology.

[The pain from burns]

The painful events associated with the treatment of a severe burn can, because of their long-lasting and repetitive characteristics, be one of the most excruciating experiences in clinical practice. Moreover, burn pain has been shown to be detrimental to burn patients. Although nociception and peripheral hyperalgesia are considered the major causes of burn pain, the study of more hypothetical mechanisms like central hyperalgesia and neuropathic pain may lead to a better understanding of burn pain symptoms and to new therapeutic approaches. Continuous pain and intermittent pain due to therapeutic procedures are two distinct components of burn pain. They have to be evaluated and managed separately. Although continuous pain is by far less severe than intermittent pain, the treatment is, in both cases, essentially pharmacological relying basically on opioids. Because of wide intra- and inter-individual variations, protocols will have to leave large possibilities of adaptation for each case, systematic pain evaluation being mandatory to achieve the best risk/benefit ratio. Surprisingly, the dose of medication decreases only slowly with time, a burn often remaining painful for long periods after healing. Non pharmacological treatments are often useful and sometimes indispensable adjuncts; but their rationale and their feasibility depends entirely on previous optimal pharmacological control of burn pain. Several recent studies show that burn pain management is inadequate in most burn centres.

Chronic Persistent Pain After Severe Burns: A Survey of 358 Burn Survivors

OBJECTIVE

To determine the prevalence, characteristics, and effects of chronic persistent pain on burn survivors.

DESIGN

Mail survey.

SETTING

Respondents' homes.

PATIENTS

All members of the Phoenix Society for Burn Survivors.

INTERVENTIONS

None.

OUTCOME MEASURES

Twenty-three questions on the prevalence of pain and its characteristics, including the short form of the McGill-Melzack Pain Questionnaire.

RESULTS

Of 1,500 members who received the survey, 358 (24%) responded. Respondents had burns covering an average of 59% of their bodies. Time between the injury and the survey averaged 12 years. On the survey, 52% of respondents reported ongoing burn-related pain, and 46% were able to characterize their pain with one or more of 15 characteristics. Two-thirds (66%) reported that pain interfered with their rehabilitation, and 55% reported that pain interfered with their daily lives. Asked "what makes the pain worse now?," the most frequent reply (15%) was "the weather" (including "hot" or "cold"). Various physical activities (e.g., walking, bicycling) were also mentioned, along with nerve regrowth, contractures, remembering the accident, and depression. "Things that make your pain better now" included "nothing," a variety of over-the-counter analgesics, "rest,""exercise,""yoga,""acupuncture,""family and friends," and "God." In coping with their pain, most respondents found family the most helpful, although nurse(s) received almost as high a rating.

CONCLUSIONS

Pain associated with burn trauma continues to be of considerable significance in the lives of burn victims long after the initial injury and hospitalization. Little research has been done on this population.

Treatment of pain in severe burns

Burn pain can cause psychologic and functional difficulties, and is difficult to predict from wound depth. The initial painful stimulation of nerve endings by the burn with continued painful stimuli result in peripheral and central mechanisms causing amplification of painful stimuli, and the development of chronic pain syndromes that can be difficult to treat. In order to assess the effect of analgesic interventions it is essential to measure the patient's pain in a simple and reproducible manner. A number of tools exist for this measurement, ranging from longer and more detailed techniques such as the McGill pain questionnaire most suited to relatively stable pain, to visual analogue scores and picture-based scores for children. Pain management begins with the acute injury, with initial measures such as cooling of the burn and use of inhalational agents such as oxygen/nitrous oxide mixtures. On arrival in hospital, for any but trivial burns, intravenous opioids are appropriate and should be administered as small intravenous boluses titrated against effect. Following the initial resuscitation, pain may be divided into background pain and that associated with procedures. These often require different analgesic interventions. Background pain may be treated with potent intravenous opioids by infusion or patient controlled analgesia and then on to oral, less potent opioids, followed by other oral analgesics. Often drug combinations work best. More severe procedural pain may be treated with a variety of interventions from a slight increase in therapy for the background pain to more potent drugs, local blocks, or general anaesthesia. In addition to drug-based methods of managing burn pain, a number of nonpharmacologic approaches have been successfully employed including hypnosis, auricular electrical stimulation, massage, and a number of cognitive and behavioural techniques.

Dissociation of osmoregulation from plasma arginine vasopressin levels following thermal injury in childhood

Although the syndrome of inappropriate anti-diuretic hormone secretion has been recognised as a complication associated with burn and other trauma in adults, relatively little is known about its incidence in children. The objective of this study was to investigate whether it is a complication associated with burn injury in children. Plasma and urine levels of arginine vasopressin (anti-diuretic hormone), sodium and osmolality were measured in samples collected from 16 burn-injured children admitted to the burns unit of the regional children's hospital. No significant correlations were found between plasma vasopressin and plasma sodium or osmolality levels, but there were significant correlations between plasma vasopressin and urine osmolality, 36 (r=0.74, p=0. 009), 60 (r=0.92, p=0.000) and 84 h (r=0.84, p=0.001) after admission, respectively. There were also significant correlations between plasma sodium and plasma osmolality, 24 (r=0.7, p=0.005), 36 (r=0.57, p=0.04) and 84 h (r=0.84, p=0.004) after admission. The data suggest dissociation between the osmolar control of vasopressin secretion and vasopressin levels after burn injury in children, but do not support the incidence of inappropriate secretion of antidiuretic hormone.

Oral methadone for the treatment of severe pain in hospitalized children: a report of five cases

OBJECTIVE

Pain relief is still inadequate in many hospitalized patients, especially children in whom suboptimal use of analgesic drugs is still common. In the past 2 years, oral methadone has been used extensively in our institution for treating children with persistent pain from cancer, burns, or trauma who were capable of oral intake and whose pain was not relieved by nonopioid medications.

SETTING

Tertiary university hospital.

PATIENTS

Of the 70 children treated thus far with oral methadone, five are described in the present report.

MAIN OUTCOME MEASURE

Pain relief, acceptability, and side effects of oral methadone in children with pain.

RESULTS

Treatment with oral methadone (0.1% in 10% glucose, dose range of 0.2-0.6 mg/kg/day) for time periods of up to 6 weeks resulted in a rapid onset and stable pain relief, with no major side effects. No adverse responses were encountered after discontinuation of treatment. In three of the children, a parent-controlled analgesia regimen was successfully employed.

CONCLUSIONS

Oral methadone can be recommended for babies and children who have severe pain that is not alleviated by nonopioid medications and who are capable of oral intake.

The systemic stress response to thermal injury in children

OBJECTIVE

Thermal injury is extremely stressful, but data characterizing the endocrine stress response to this injury in children are sparse. The objective of this study was to measure the effects of thermal injury on the levels of stress hormones in children and to assess the temporal changes associated with them.

PATIENTS

Twenty-three children, 13 girls and 10 boys aged between 5 months and 12 years 3 months (mean, 2 years 11 months), with burns covering 10-61% of their body surface (mean, 20.5%) were studied during the first 5 days following injury.

MEASUREMENTS

The levels of arginine vasopressin, angiotensin II, cortisol, adrenaline, noradrenaline and dopamine were measured in sequential blood samples obtained from thermally injured children on admission and at specified time intervals during the 5 days of the investigation.

RESULTS

At admission the concentrations of all the hormones were high, and varied widely between individual patients. The geometric mean and 95% confidence intervals of admission hormone levels were as follows: arginine vasopressin 18.3 (8.3-40.7) pmol/l; angiotensin II 122.0 (56.0-266.2) pmol/l; cortisol 650.6 (473.0-895.0) nmol/l; dopamine 1.0 (0.1-8.0) nmol/l; adrenaline 6.4 (3.2-12.5) nmol/l and noradrenaline 2.3 (1.3-4.3) nmol/l. Although the concentrations of arginine vasopressin and cortisol returned to normal 24 to 36 h after admission, the levels of angiotensin II, adrenaline and dopamine fluctuated and remained higher than normal throughout the study (108 h).

CONCLUSIONS

Thermal injury results in the release of abnormally high levels of stress hormones in children. Although there are similarities between some of the data reported here and those reported in adults, higher levels of adrenaline and lower levels of noradrenaline than reported in adults suggest important differences too. These differences may need to be taken into account in the management of burn-injured children.

Anesthesia and pain management in pediatric burn patients

Patients with severe burn injury are a challenge for the pediatric anesthesiologist. Today with adequate care many children survive their trauma and have a good chance for complete functional and psychological rehabilitation. The anesthesiologist has to provide excellent care even for patients in suboptimal or unstable condition to enable wound debridement and grafting, because only rapid skin closure will stabilize the patient. Adequate pain treatment during all phases of burn treatment is mandatory.

[Treatment of pain in children burns]

Burn injury is considered by children as one of the most painful traumas (just after bone factures). Burn pain in children can and must be controlled as well as for adult patients, with almost identical techniques. Continuous pain from injury and intermittent pain caused by therapeutic procedures must be evaluated and treated separately. Due to very high levels of nociception, satisfactory management of procedural pain requires the use of opioid therapy. Non pharmacological methods are meaningless if pharmacological treatment is not optimal.

Acetaminophen in the management of background pain in children post-burn

This retrospective review evaluated the pain management of 395 acutely burned pediatric patients who were treated by a pain management protocol emphasizing acetaminophen as the initial medication to control background pain. Pain was assessed by using standardized instruments based on observations by patients, nurses, and parents. Morphine was added when scheduled acetaminophen (10-15 mg/kg/4 hr) did not control background pain. Fifty percent of the children received only acetaminophen to control background pain. Younger children and children with the smallest burns, regardless of age, were likely to be managed with acetaminophen alone. Most peak serum concentrations of acetaminophen were less than 10 micrograms/mL. When needed, children also received medication for painful procedures, anxiety, and posttraumatic stress symptoms. These additional medications were not more frequently given to children receiving only acetaminophen for background pain. These data suggest that acetaminophen is a safe, useful medication for the control of post-burn background pain in some children.

Pain in burn patients

While severe pain is a constant component of the burn injury, inadequate pain management has been shown to be detrimental to burn patients. Pain-generating mechanisms in burns include nociception, primary and secondary hyperalgesia and neuropathy. The clinical studies of burn pain characteristics reveal very clear-cut differences between continuous pain and pain due to therapeutic procedures which have to be treated separately. Some of the main features of burn pain are: (1) its long-lasting course, often exceeding healing time, (2) the repetition of highly nociceptive procedures which can lead to severe psychological disturbances if pain control is inappropriate. Pharmaco-therapy with opioids is the mainstay for analgesia in burned patients, but non-pharmacological techniques may be useful adjuncts. Routine pain evaluation is mandatory for efficient and safe analgesia. Special attention must be given to pain in burned children which remains too often underestimated and undertreated. More educational efforts from physicians and nursing staff are necessary to improve pain management in burned patients.

Sedative-analgesic agent administration in children: analysis of use and complications in the emergency department

The frequency of, indications for, and complications from non-acetaminophen sedative-analgesic agents (SAAs) administered to children less than 16 years of age in the emergency department (ED) were determined by a retrospective review. All 21,353 charts from a single university hospital ED over a 16-month period were included. Few children (N = 759; 3.5%) received SAAs. Of 919 total doses, 13% of children received a second and 4.5% received a third SAA. The group was 59% male. Most children were < or = 10 years of age. Sixty-two percent of SAAs were either sedatives or opioids. Sedatives given included chloral hydrate, diazepam, lorazepam, midazolam, and phenobarbital. Opioids given included morphine, codeine, and meperidine. Indications for SAAs included painful procedures, analgesia, radiographic imaging, and seizure activity. Complications (N = 51; 6.7%) included inadequate sedation, vomiting, and respiratory depression or oxygen desaturation. Respiratory depression or oxygen desaturation occurred only after intravenous administration of SAAs for seizures. In children, non-acetaminophen SAAs are used most commonly in younger patients requiring sedation for painful procedures or for radiologic imaging. Respiratory depression was observed only after intravenous administration of anticonvulsants.

Enhanced potency of intravenous, but not intrathecal, morphine and morphine-6-glucuronide after burn trauma

We examined the analgesic effect of morphine (M) and its metabolite morphine-6-glucuronide (M6G) in a rat model of acute thermal trauma. M or M6G were given by intrathecal (IT) or intravenous (i.v.) routes after brief burn or sham burn delivered during inhalational anesthesia. In the sham group, M6G was significantly less potent than M when given i.v., yet tended to be more potent than M when given IT. For both drugs, thermal injury increased i.v. potency, yet decreased (for M) or displayed a trend to decrease (for M6G) It potency. The increased potency seen with i.v. but not IT opioid administration may reflect pharmacokinetic (e.g., diminished clearance) and/or pharmacodynamic responses (e.g., activation of peripheral opioid receptors) after thermal injury.

Pain during burn dressing change in children: relationship to burn area, depth and analgesic regimens

To determine the level of pain that acutely burned children experience, we obtained pain scores before, during and after burn dressing change (BDC). Pain scores were higher during the BDC, consistent with severe pain during this procedure. A positive correlation between pain scores and the body surface area (BSA) burned suggests that pain increases with the size of the burn. Contrary to widely held beliefs, comparison of mean pain scores and the percent of 3rd degree burn revealed that the larger the area of full-thickness injury, the greater the pain. Regardless of wide variations in patient characteristics, fixed doses of oral narcotics were usually prescribed for pain. Patients with BSA greater than 70% experienced severe pain during BDC despite the type, dose or route of opioids. These findings suggest the need for (a) education to correct the myth that 'third-degree burns don't hurt'; (b) revision of analgesic prescribing patterns in the burned child; and (c) research to determine the mechanisms (e.g., tolerance or deafferentation) underlying the opioid-resistant nature of pain after large burns.