Peripheral neurological problems in the acute burn patient

Innervation of an Ultrasound-Mediated PVDF-TrFE Scaffold for Skin-Tissue Engineering

In this work, electrospun polyvinylidene-trifluoroethylene (PVDF-TrFE) was utilized for its biocompatibility, mechanics, and piezoelectric properties to promote Schwann cell (SC) elongation and sensory neuron (SN) extension. PVDF-TrFE electrospun scaffolds were characterized over a variety of electrospinning parameters (1, 2, and 3 h aligned and unaligned electrospun fibers) to determine ideal thickness, porosity, and tensile strength for use as an engineered skin tissue. PVDF-TrFE was electrically activated through mechanical deformation using low-intensity pulsed ultrasound (LIPUS) waves as a non-invasive means to trigger piezoelectric properties of the scaffold and deliver electric potential to cells. Using this therapeutic modality, neurite integration in tissue-engineered skin substitutes (TESSs) was quantified including neurite alignment, elongation, and vertical perforation into PVDF-TrFE scaffolds. Results show LIPUS stimulation promoted cell alignment on aligned scaffolds. Further, stimulation significantly increased SC elongation and SN extension separately and in coculture on aligned scaffolds but significantly decreased elongation and extension on unaligned scaffolds. This was also seen in cell perforation depth analysis into scaffolds which indicated LIPUS enhanced perforation of SCs, SNs, and cocultures on scaffolds. Taken together, this work demonstrates the immense potential for non-invasive electric stimulation of an in vitro tissue-engineered-skin model.

A review of burn symptoms and potential novel neural targets for non-invasive brain stimulation for treatment of burn sequelae

Burn survivors experience myriad associated symptoms such as pain, pruritus, fatigue, impaired motor strength, post-traumatic stress, depression, anxiety, and sleep disturbance. Many of these symptoms are common and remain chronic, despite current standard of care. One potential novel intervention to target these post burn symptoms is transcranial direct current stimulation (tDCS). tDCS is a non-invasive brain stimulation (NIBS) technique that modulates neural excitability of a specific target or neural network. The aim of this work is to review the neural circuits of the aforementioned clinical sequelae associated with burn injuries and to provide a scientific rationale for specific NIBS targets that can potentially treat these conditions. We ran a systematic review, following the PRISMA statement, of tDCS effects on burn symptoms. Only three studies matched our criteria. One was a feasibility study assessing cortical plasticity in chronic neuropathic pain following burn injury, one looked at the effects of tDCS to reduce pain anxiety during burn wound care, and one assessed the effects of tDCS to manage pain and pruritus in burn survivors. Current literature on NIBS in burn remains limited, only a few trials have been conducted. Based on our review and results in other populations suffering from similar symptoms as patients with burn injuries, three main areas were selected: the prefrontal region, the parietal area and the motor cortex. Based on the importance of the prefrontal cortex in the emotional component of pain and its implication in various psychosocial symptoms, targeting this region may represent the most promising target. Our review of the neural circuitry involved in post burn symptoms and suggested targeted areas for stimulation provide a spring board for future study initiatives.

Post-Burn Pruritus

Post-burn pruritus is the pruritus that occurs after burn during the rehabilitation and healing process of burn wounds. The post-burn pruritus is a common and serious complication of burn injury, which severely lowers the quality of life of the patient. Many potential treatments are available for pruritus but there is no consensus of the best single treatment yet. The precise mechanism of post-burn pruritus has not been elucidated, but it appears to have pruritogenic and neuropathic aspects. Clinically, post-burn pruritus tends to be intractable to conventional treatment but rather responds to neuroleptic agents, such as gabapentin and pregabalin. During wound healing, various neuropeptides secreted from the nerves of the skin control epidermal and vascular proliferation and connective tissue cells. When keratinocytes are activated by an itch-inducing substance, they secrete a variety of inflammatory substances that increase the susceptibility of the itch receptor. There are two mechanisms underlying post-burn neuropathic pruritus. The first one is peripheral sensitization. The second one is the intact nociceptor hypothesis. An effective treatment for post-burn pruritus will also be effective in other neuropathic and intractable itching. In this review, we summarized the interaction and mechanism of keratinocytes, immune cells, and nerve fibers related to post-burn pruritus.

Peripheral Neuropathy and Nerve Compression Syndromes in Burns

Peripheral neuropathy and nerve compression syndromes lead to substantial morbidity following burn injury. Patients present with pain, paresthesias, or weakness along a specific nerve distribution or experience generalized peripheral neuropathy. The symptoms manifest at various times from within one week of hospitalization to many months after wound closure. Peripheral neuropathy may be caused by vascular occlusion of vasa nervorum, inflammation, neurotoxin production leading to apoptosis, and direct destruction of nerves from the burn injury. This article discusses the natural history, diagnosis, current treatments, and future directions for potential interventions for peripheral neuropathy and nerve compression syndromes related to burn injury.

Intensive care unit-acquired weakness in the burn population

Intensive care unit-acquired weakness is an evolving problem in the burn population. As patients are surviving injuries that previously would have been fatal, the focus of treatment is shifting from survival to long-term outcome. The rehabilitation of burn patients can be challenging; however, a certain subgroup of patients have worse outcomes than others. These patients may suffer from intensive care unit-acquired weakness, and their treatment, physiotherapy and expectations need to be adjusted accordingly. This study investigates the condition of intensive care unit-acquired weakness in our burn centre. We conducted a retrospective analysis of all the admissions to our burn centre between 2008 and 2012 and identified 22 patients who suffered from intensive care unit-acquired weakness. These patients were significantly younger with significantly larger burns than those without intensive care unit-acquired weakness. The known risk factors for intensive care unit-acquired weakness are commonplace in the burn population. The recovery of these patients is significantly affected by their weakness.

Physical and psychiatric recovery from burns

Burn injuries pose complex biopsychosocial challenges to recovery and improved comprehensive care. The physical and emotional sequelae of burns differ, depending on burn severity, individual resilience, and stage of development when they occur. Most burn survivors are resilient and recover, whereas some are more vulnerable and have complicated outcomes. Physical rehabilitation is affected by orthopedic, neurologic, and metabolic complications and disabilities. Psychiatric recovery is affected by pain, mental disorders, substance abuse, and burn stigmatization. Individual resilience, social supports, and educational or occupational achievements affect outcomes.

Physical and psychiatric recovery from burns

Burn injuries pose complex biopsychosocial challenges to recovery and improved comprehensive care. The physical and emotional sequelae of burns differ, depending on burn severity, individual resilience, and stage of development when they occur. Most burn survivors are resilient and recover, whereas some are more vulnerable and have complicated outcomes. Physical rehabilitation is affected by orthopedic, neurologic, and metabolic complications and disabilities. Psychiatric recovery is affected by pain, mental disorders, substance abuse, and burn stigmatization. Individual resilience, social supports, and educational or occupational achievements affect outcomes.

Inhibition of inducible nitric oxide synthase reduces an acute peripheral motor neuropathy produced by dermal burn injury in mice

The systemic inflammatory response produced by a full-thickness dermal burn injury is associated with a peripheral motor neuropathy. We previously reported that a 20% body surface area (BSA) full-thickness dermal burn in C57BL6 mice produced structural and functional deficits in motor axons at a distance from the burn site. The etiology of the neuropathy, however, is not well characterized. Burn injury leads to an increase in production of a number of proinflammatory mediators, including nitric oxide (NO). We tested the hypothesis that dermal burn-induced motor neuropathy is mediated by increased production of NO. NO synthase (NOS) activity was inhibited following a 20% BSA full-thickness burn by injection of non-specific NOS inhibitor, nitro-L-arginine methyl ester or inducible NOS (iNOS) inhibitors, L-N6-(1-iminoethyl) lysine, and aminoguanidine. NOS inhibitors also prevented the reduction in ventral roots mean axon caliber and the decrease in a motor nerve conduction velocity (MCV) following burn. iNOS knockout mice prevented MCV decrease in the first 3 days post-burn, but iNOS knockout MCV was significantly reduced at 7-14 days post-burn. These results suggest that an increase in NO production generated by systemic inflammatory response pathways after burn injury contributes to the development of structural and functional deficits in peripheral motor axons.

Neuromuscular manifestations of critical illness

Critical illness, more precisely defined as the systemic inflammatory response syndrome (SIRS), occurs in 20%-50% of patients who have been on mechanical ventilation for more than 1 week in an intensive care unit. Critical illness polyneuropathy (CIP) and myopathy (CIM), singly or in combination, occur commonly in these patients and present as limb weakness and difficulty in weaning from the ventilator. Critical illness myopathy can be subdivided into thick-filament (myosin) loss, cachectic myopathy, acute rhabdomyolysis, and acute necrotizing myopathy of intensive care. SIRS is the predominant underlying factor in CIP and is likely a factor in CIM even though the effects of neuromuscular blocking agents and steroids predominate in CIM. Identification and characterization of the polyneuropathy and myopathy depend upon neurological examination, electrophysiological studies, measurement of serum creatine kinase, and, if features suggest a myopathy, muscle biopsy. The information is valuable in deciding treatment and prognosis.

Electrical injuries: a 20-year review

Electrical injuries continue to present problems with devastating complications and long-term socioeconomic impact. The purpose of this study is to review one institution's experience with electrical injuries. From 1982 to 2002, there were 700 electric injury admissions. A computerized burn registry was used for data collection and analysis. Of these injuries, 263 were high voltage (> or =1000 V), 143 were low voltage (<1000 V), 277 were electric arc flash burns, and 17 were lightning injuries. Mortality was highest in the lightning strikes (17.6%) compared with the high voltage (5.3%) and low voltage (2.8%) injuries, and mortality was least in electric arc injuries without passage of current through the patient (1.1%). Complications were most common in the high-voltage group. Mean length of stay was longest in this group (18.9 +/- 1.4 days), and the patients in this group also required the most operations (3 +/- 0.2). Work-related activity was responsible for the majority of these high-voltage injuries, with the most common occupations being linemen and electricians. These patients tended to be younger men in the prime of their working lives. Electrical injuries continue to make up an important subgroup of patients admitted to burn centers. High-voltage injuries in particular have far reaching social and economic impact largely because of the patient population at greatest risk, that is, younger men at the height of their earning potential. Injury prevention, although appropriate, remains difficult in this group because of occupation-related risk.

Peripheral axon caliber and conduction velocity are decreased after burn injury in mice

Peripheral neuropathies are reported to arise as a result of the systemic inflammatory response produced by a full-thickness cutaneous burn injury. This study was designed to characterize the magnitude and time course of functional and morphological changes in peripheral axons that arise after a full-thickness dermal burn injury in an animal model. A 20% body surface area (20% BSA) full-thickness dermal burn was applied to the back of C57BL6 female mice. Longitudinal H- and M-wave recordings were used to determine the conduction velocities (CV) of large myelinated motor and sensory axons in the tibial nerve of sham control and burn-injured mice. Motor CVs were significantly reduced from 6 h to 28 days after the burn, and sensory CVs were significantly reduced from 7 to 14 days after the burn. Morphological evaluation also showed that the mean caliber of large axons in tibial nerves and L5 ventral and dorsal roots in burned mice was significantly decreased. The results demonstrate that both functional and morphological deficits may be produced in peripheral nerve axons at sites well removed from a full-thickness dermal burn injury. The neural deficits may contribute to changes in neuromuscular transmission and the development of limb and respiratory muscle weakness that also accompany burn injury.

Neuropathy after burn injury

The purpose of this study was to evaluate the incidence of neuropathy in a consecutive cohort of patients with major burn injuries and investigate the clinical correlates for both mononeuropathy and generalized peripheral polyneuropathy. Of 572 patients examined, 64 (11%) patients had clinical evidence of mononeuropathy or peripheral neuropathy or both. Associations of mononeuropathy and peripheral neuropathy with potential risk factors were identified using logistic regression analyses. Electrical cause (odds ratio [OR] = 4.1022, P < .01), history of alcohol abuse (OR = 2.2893, P <.05), and number of days in intensive care (OR = 1.0457, P < .001) were significantly associated with mononeuropathy. The number of days in intensive care (OR = 1.0740, P < .001) and patient age (OR = 1.0543, P < .01) were significantly associated with peripheral neuropathy. This study demonstrates that neuropathy is a common complication of severe burn injury in patients who are older, critically ill, have an electrical cause, or history of alcohol abuse.

Psychosocial care in oncology nursing: a study of social knowledge

A combination of focus group and individual interviews aimed to examine psychosocial aspects of nursing within a social context and social knowledge held by two teams of ward-based oncology nurses. Five core categories of knowledge emerged: knowledge of how to care, knowledge of the patient, knowledge of the ward, knowledge of nurses coping, and knowledge of involvement. Involvement or emotional closeness was seen as a necessary, inevitable and potentially stressful feature of psychosocial care. The authors conclude that interpersonal and professional aspects of nursing must be balanced in order to provide effective psychosocial care.

Peripheral neuropathy in burn patients

Neuropathy in burn patients is frequently overlooked. This study aimed at looking for neuropathies among burn patients. It included 55 burn patients, whether symptomatic or asymptomatic, with variable depths of burn at different stages. Their ages ranged from 8 to 55 years with a mean age of 23.6 +/- 11.1 years. All patients were submitted to clinical examination, electromyographic and motor conduction velocities of burned and unburned limbs. Serum electrolyte, blood urea and creatinine were measured for all patients. Sixteen patients (29 per cent) had peripheral neuropathy. Only six had symptoms and signs of peripheral neuropathy. The most frequently diagnosed neuropathy in this study was mononeuritis multiplex in nine patients (56 per cent), then generalized distal axonal neuropathy in five patients (31 per cent) and entrapment neuropathy in two patients (13 per cent). In patients with mononeuritis, 29 nerves were affected, 24 nerves related to the site of the burn and five nerves were away from the site of the burn. All the entrapment neuropathy developed after wound healing. Age above 20 years, electric burns burns involving full thickness of the skin and a surface area of more than 20 per cent were associated with a significantly higher prevalence of neuropathy. Other parameters were not found to be significant in the development of neuropathy.

Neurological sequelae following a high voltage electrical burn

Neurological complications secondary to electrical injury can manifest themselves either early or late. A small percentage of these patients develop delayed peripheral neuropathy. However, patients experiencing transient spinal cord symptoms have been described. We describe the development of a lower motor neurone syndrome affecting all the limbs in a patient following a significant electrical injury, which although expected to cause spinal cord necrosis showed no evidence of this on magnetic resonance imaging. The fact that neurophysiology was unable to localize the problem made this case all the more perplexing. Similar cases reported in the literature are discussed.

Sepsis and the systemic inflammatory response syndrome: neuromuscular manifestations

OBJECTIVE

To describe the various conditions of peripheral nerve, neuromuscular junction, and muscle associated with the systemic inflammatory response syndrome (SIRS).

DATA SOURCES

Publications in the scientific literature and personal observations during the last 15 yrs.

DATA EXTRACTION

Computer search of the literature and review of patient records relating to polyneuropathy, neuromuscular transmission defects, and myopathies associated with sepsis, the septic syndrome, and SIRS.

SYNTHESIS

SIRS is a new concept in which infection and trauma induce a systemic inflammatory response affecting the microcirculation to organs throughout the body. The nervous system is commonly affected in the forms of septic encephalopathy and critical illness polyneuropathy. Neuromuscular blocking agents and corticosteroids may have additional toxic effects on the neuromuscular system that are manifest as transient neuromuscular blockade, an axonal motor neuropathy, or a thick filament myopathy. Clinical examination in the critical care unit is often unreliable and electrophysiologic studies, at times accompanied by magnetic resonance imaging of the spinal cord, measurement of the circulating creatine phosphokinase concentration, and muscle biopsy, are often necessary to establish the diagnosis. Variants of critical illness polyneuropathy may occur outside the critical care unit. The precise mechanism of these neuromuscular conditions is not known, and further basic research is needed.

CONCLUSIONS

A variety of neuromuscular conditions complicates SIRS. The identification of these conditions is important in patient management and in rendering a prognosis.

[Curare and burns]

Burns of more than 15% of the body surface area result in major physiological changes with an alteration of cardiovascular, pulmonary, hepatic and renal functions, as well as modifications in the pharmacokinetics and the pharmacodynamics of many drugs. Among these, a major change in the activity of muscle relaxants occurs which can be specific to this pathology. Succinylcholine is contra-indicated during recovery from a burn trauma because of a possible hyperkaliemic response, directly related to the dose, the post-burn delay and the area of burned body surface. The kaliemic response and the related cardiac complications remain unpredictable. The height of twich depression with small doses of succinylcholine such as 0.1 to 0.2 mg.kg-1, demonstrates the hypersensitivity to this agent and does cause neither metabolic disturbances nor cardiac arrest. Nevertheless, the administration of succinylcholine is contra-indicated for from the 5th day on at least two years after the burn injury. Conversely, the action of non-depolarizing muscle relaxants is characterized by a resistance, which is correlated to both the post-traumatic delay and the extent of the burned area. It starts on about the seventh day, reaches peak intensity between day 15 and day 40 and can persist up two years after the thermal injury. In the course of a burn, the so-called "immature" acetylcholine receptors, characterized by the substitution of the sub-unit epsilon by a protein gamma, increase at the level of the end plate areas and the extra-synaptic muscle membrane. These receptors explain both the hyperkaliemic response and the hypersensitivity to succinlycholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Postburn peroneal nerve palsy--a report of two consecutive cases

We report two patients suffering from mixed deep partial and full skin thickness flame burns covering 45 and 95 per cent of the total body surface area respectively. These patients, following sepsis and multisystem failure, developed unilateral peroneal nerve palsy. The possible aetiology of isolated injury to the peroneal nerve in burned and critically ill trauma patients is discussed.

Sciatic nerve function following hindlimb thermal injury

Peripheral neuropathy occurs in approximately 20% of patients with major burns and seriously impairs rehabilitation. We describe an experimental model which permits elevation of the tissue temperature in the region of the distal sciatic nerve trunk of rats at a reproducible rate to a predetermined level without inflicting concomitant major cutaneous injury. Radiofrequency current is delivered through parallel copper electrodes mounted in a chamber into which the limb has been inserted. In the present experiments, tissue temperature was arbitrarily elevated to 47 degrees C for 30 sec in 62 rats. There were 43 normal controls. The posterior tibial branch was the most intensively studied, as some of its conduction characteristics can be serially assessed percutaneously. Conduction block, which was apparently irreversible, was present in 67% of posterior tibials by 24 hr postinjury. In branches which were still excitable, prolongation of the absolute refractory period was the most consistent abnormality noted. Slowing of conduction, as evidenced by prolongation of inflection velocity or peak velocity, was never observed. However, this injury resulted in selective conduction failure of sural--but not of peroneal--fibers which conducted at 40 m/sec or greater. Fiber modality is an important determinant of the vulnerability to direct thermal injury of peripheral nerve in vivo.

Severe peripheral burn polyneuropathy: a case report

This report describes a 30-year-old man with a 45 per cent mixed deep partial and full thickness flame burn, who--following sepsis and multisystem failure--developed a severe polyneuropathy affecting the left median and both ulnar nerves, and both peroneal and posterior tibial nerves. The neurological alterations were significantly reversible, early reinnervation in all limbs was demonstrated by electromyography at 8 months, with subsequent progressive reinnervation at 1 year. The most likely cause of this polyneuropathy was the acute development of uraemia, at day 33 post-burn.

Clinical pharmacology of muscle relaxants in patients with burns

Pathophysiologic changes accompanying burn trauma can alter the pharmacokinetics and pharmacodynamic responses to neuromuscular relaxants. Pathophysiologic changes that can potentially affect kinetics in the hypermetabolic phase of burn injury include increased hepatic blood flow, increased glomerular filtration, and increased protein binding. Except for D-tubocurarine, the pharmacokinetics of neuromuscular relaxants relative to burn trauma have not been studied. The unbound volume of distribution, clearance, and half-life of D-tubocurarine were not significantly different from controls, but the plasma binding and renal elimination at 24 hours was increased in burn patients. The aberrant pharmacodynamic responses to neuromuscular relaxants in burn patients include the potential for lethal hyperkalemia with the administration of depolarizing relaxant, succinylcholine, and a 2.5- to 5.0-fold increase in the dose or plasma concentration requirement for nondepolarizing relaxant, including D-tubocurarine, metocurine, pancuronium, and atracurium. The altered pharmacodynamic responses are probably related to an increase in nicotinic acetylcholine receptor number. An alternative to succinylcholine to produce rapid-onset neuromuscular paralysis include the administration of 3XED95 doses of pancuronium and metocurine in combination (but recovery from paralysis is prolonged). Vecuronium and atracurium have good cardiovascular stability and faster recovery times even in high dosages in healthy patients, but the pharmacokinetics and pharmacodynamics of these drugs in patients with burns have not been fully characterized.

Burn rehabilitation-a team approach

The team concept in the treatment of burned patients is an effective approach in caring for the physical, psychological, and social needs of the patient. Through the initiation of early rehabilitation services, long-term problems can be prevented and a quicker return to a meaningful life style is possible.