Biochemical and pharmacological properties of a neurotoxic protein isolated from the blood serum of heavily burned patients

Nerve Pain after Burn Injury: A Proposed Etiology-Based Classification

BACKGROUND

Understanding the mechanism of nerve injury may facilitate managing burn-related nerve pain. This proposed classification, based on cause of nerve injury, was developed to enhance the understanding and management of burn-related nerve pain.

METHODS

This retrospective investigation included patients aged 15 years or older admitted to the burn center from 2014 to 2019. Burn-related nerve pain was patient-reported and clinically assessed as pain 6 months or more after burn injury, unrelated to preexisting illnesses/medications. The pain classification consisted of direct nerve injury, nerve compression, electrical injury, and nerve dysfunction secondary to systemic injury. The four categories were statistically analyzed between groups, using 52 variables.

RESULTS

Of the 1880 consecutive burn patients, 113 developed burn-related nerve pain and were eligible for validation of the classification: direct nerve injury, n = 47; nerve compression, n = 12; electrical injury, n = 7; and nerve dysfunction secondary to systemic injury, n = 47. Factors, significantly increased, that distinguished one category from another were as follows: for direct nerve injury, continuous symptoms (p < 0.001), refractory nerve release response (p < 0.001), nerve repair (p < 0.001), and pruritus (p < 0.001); for nerve compression, Tinel signs (p < 0.001), shooting pain (p < 0.001), numbness (p = 0.003), intermittent symptoms (p < 0.001), increased percentage total body surface area burned (p = 0.019), surgical procedures (p < 0.001), and nerve release (p < 0.001); and for electrical injury, Tinel sign (p < 0.001), intermittent symptoms (p = 0.002), amputations (p = 0.002), fasciotomies (p < 0.001), and nerve release (p < 0.001). Nerve dysfunction secondary to systemic injury was distinguished by significantly less Tinel signs (p < 0.001), shooting pain (p < 0.001), numbness and tingling (p < 0.001), pruritus (p < 0.001), fascial excision (p = 0.004), skin grafts (p < 0.001), amputation (p = 0.004), nerve releases (p < 0.001), and third-degree burns (p = 0.002).

CONCLUSION

A classification consisting of direct nerve injury, nerve compression, electrical injury, and nerve dysfunction secondary to systemic injury is presented that may guide patient management and research methods, with the goal of improving pain outcomes in burn-related nerve pain.

Prevalence and associated predictors for patients developing chronic neuropathic pain following burns

BACKGROUND

Chronic pain, unrelated to the burn itself, can manifest as a long-term complication in patients sustaining burn injuries. The purpose of this study was to determine the prevalence of chronic neuropathic pain (CNP) and compare burn characteristics between patients who developed CNP and patients without CNP who were treated at a burn center.

METHODS

A single-center, retrospective analysis of 1880 patients admitted to the adult burn center was performed from 1 January 2014 to 1 January 2019. Patients included were over the age of 15 years, sustained a burn injury and were admitted to the burn center. CNP was diagnosed clinically following burn injury. Patients were excluded from the definition of CNP if their pain was due to an underlying illness or medication. Comparisons between patients admitted to the burn center with no pain and patients admitted to the burn center who developed CNP were performed.

RESULTS

One hundred and thirteen of the 1880 burn patients developed CNP as a direct result of burn injury over 5 years with a prevalence of 6.01%. Patients who developed CNP were a significantly older median age (54 years vs. 46 years, p = 0.002), abused alcohol (29% vs. 8%, p < 0.001),abused substances (31% vs. 9%, p < 0.001), were current daily smokers (73% vs. 33%, p < 0.001), suffered more full-thickness burns (58% vs. 43%, p < 0.001), greater median percent of total body surface area (%TBSA) burns (6 vs. 3.5, p < 0.001), were more often intubated on mechanical ventilation (33% vs. 14%, p < 0.001), greater median number of surgeries (2 vs. 0, p < 0.001) and longer median hospital length of stay (LOS) (10 days vs. 3 days, p < 0.001), compared to those who did not develop CNP, respectively. Median patient follow-up was 27 months.

CONCLUSIONS

The prevalence of CNP over 5 years was 6.01% in the burn center. Older ages, alcohol abuse, substance abuse, current daily smoking, greater percent of total body surface area (%TBSA) burns, third degree burns, being intubated on mechanical ventilation, having more surgeries and longer hospital LOS were associated with developing CNP following burn injury, compared to patients who did not develop CNP following burn injury.

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.

Bench-to-bedside review: Burn-induced cerebral inflammation--a neglected entity?

Severe burn injury remains a major burden on patients and healthcare systems. Following severe burns, the injured tissues mount a local inflammatory response aiming to restore homeostasis. With excessive burn load, the immune response becomes disproportionate and patients may develop an overshooting systemic inflammatory response, compromising multiple physiological barriers in the lung, kidney, liver, and brain. If the blood–brain barrier is breached, systemic inflammatory molecules and phagocytes readily enter the brain and activate sessile cells of the central nervous system. Copious amounts of reactive oxygen species, reactive nitrogen species, proteases, cytokines/chemokines, and complement proteins are being released by these inflammatory cells, resulting in additional neuronal damage and life-threatening cerebral edema. Despite the correlation between cerebral complications in severe burn victims with mortality, burn-induced neuroinflammation continues to fly under the radar as an underestimated entity in the critically ill burn patient. In this paper, we illustrate the molecular events leading to blood–brain barrier breakdown, with a focus on the subsequent neuroinflammatory changes leading to cerebral edema in patients with severe burns.

Specific deposition of passively transferred monoclonal antibodies against herpes simplex virus type 1 in rat brain infected with the virus

The kinetics of human monoclonal antibody (anti-gB) to herpes simplex virus type 1 (HSV-1) were investigated after intravenous injection of anti-gB into an HSV-1 encephalitis animal model. Immunohistochemical study revealed specific deposition of passively transferred anti-gB in the hippocampus and thalamus of the infected rat brain, and it bound to the same neurons in which HSV-1 antigen was positively stained. To examine the macroscopic distribution of anti-gB in the infected brain, we undertook an 125I-labeled anti-gB injection study, and the same distribution of 125I-labeled anti-gB deposition was observed by brain semimicroautoradiography as in the immunohistochemical study. These results suggest that anti-gB easily permeates the capillary wall and is deposited in the inflammatory site where HSV-1-specific antigen is detectable. The use of radioisotope-labeled anti-gB injection and external brain imaging could lead to a noninvasive diagnostic tool for the early detection of HSV-1 antigen in cases of suspected HSV-1 encephalitis.

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.

Neurotoxic components in normal serum

Serum neurotoxicity was studied by adding whole or fractionated serum (adult human, adult horse, or newborn calf) to neuron-rich cultures prepared from various regions of embryonic (Days 14-15) rat brain, including spinal cord, ventral mesencephalon, cerebellum, septum, and striatum. Effects of serum were also tested on several types of embryonic non-neuronal cells (skeletal muscle myotubes, cardiac muscle myocytes, and fibroblasts from skin and lung). Serum concentrations of 50% or more killed more than 95% of all neurons within 3 days. Serum concentrations as low as 10% also killed some neurons, especially those from cerebellum. Septal, cerebellar, and spinal cord neurons were more sensitive than striatal or mesencephalic neurons. All the tested non-neuronal cells survived much better than neurons at serum concentrations of 20% or more. Neurotoxicity was present in both fresh (human) and previously frozen (human and animal) sera, and affected both young (4 days in vitro) and older (42 days in vitro) cultures. Neurotoxicity was greatly diminished by heating the serum to 56 degrees C for 30 min. Experiments indicated that serum toxicity was not due to lipoprotein, complement, or tumor necrosis factor. All serum neurotoxicity was retained by an ultrafilter with a nominal molecular weight cutoff of 10 kDa. The profile of neurotoxicity following gel filtration at neutral pH was variable, with high toxicity most consistently observed in fractions with apparent molecular weights exceeding 100 kDa, and variable degrees of toxicity at lower molecular weights.

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.

Effects of thermal trauma on cardiac force of contraction

Previous studies have reported that administration of potent peripheral vasodilating drugs will significantly increase thermal trauma-induced depression of cardiac output. This finding suggests that most of the depression in cardiac output after thermal trauma is due to an increase in peripheral resistance and a decrease in venous return rather than a direct depression of myocardial contractile force. Studies have been carried out using a strain gauge arch sewn on the left ventricle to measure myocardial force of contraction in the mongrel dog anaesthetized with sodium pentobarbital and receiving a 15 per cent total body surface area full skin thickness flame burn. The results of this study showed a significant decrease in cardiac output immediately after burn, which persisted for 7 h. Myocardial force of contraction, measured in grams, fell immediately after burn and returned to pre-burn values by 3 h post-burn. In one series of animals, verapamil, a calcium-channel-blocking substance, was administered. In these animals cardiac output returned to pre-burn levels following the administration of the drug, but myocardial force of contraction remained significantly lower than pre-burn value for the duration of the experiment. Correlation coefficients comparing cardiac output and myocardial force of contraction showed no significant relationship between values in either untreated or verapamil-treated animals.

'Metabolic' factors in thermal injury: role of nucleic acids

We believe that toxic events observed after thermal injury may be caused by the release of normally intracellular substances into the circulation. We define these substances as 'metabolic' factors. Analysis of extracts prepared from normal and burned mouse skin indicates that the burned skin extract contains increased clot-promoting (Thromboplastin-like) substances and, perhaps, less RNA than normal skin extracts. Injection of RNA or its breakdown products into the burned site significantly increases the acute mortality in burned mice. No increase in mortality is observed when these substances are injected into a non-burned site on burned mice. We suggest that 'Thromboplastin-like substances and RNA or RNA breakdown products may be some of the 'metabolic' factors involved in acute burn toxicity. Upon being released from their intracellular residence after thermal injury, their combined activity contributes to the acute mortality observed.

Leukoencephalopathy associated with extensive burns

Unusual neuropathological changes were observed in two cases following extensive burns. These consisted of perivascular areas of demyelination distributed symmetrically in the brain and affecting the white matter predominantly. One case in addition had widespread petecchial and ring haemorrhages characteristic of brain purpura. Both patients sustained second and third degree burns in greater than 50% of the body surface area, developed metabolic acidosis, sepsis, disturbance in consciousness and multiple episodes of cardiorespiratory arrest prior to death. A toxic metabolic state related to a burn toxin released from the damaged tissue or from bacterial action to the tissue in addition to low platelet level is proposed as the major pathogenetic factor in the development of the neurological symptoms and the patients' demise.

Biochemical and pharmacological properties of a cardiotoxic factor isolated from the blood serum of burned patients

Blood serum of severely burned patients contains several substances which are not present in normal sera. One of these substances, a small protein of an approximate molecular weight of 12 to 14,000 daltons displayed a toxic action on the circulatory system. This cardiotoxic factor was obtained in a purified form by alcohol precipitation followed by gel filtration and carboxymethyl cellulose chromatography. The purified preparation seems to be a low molecular weight protein of about 8000 daltons. The biological effects of this substance consist essentially of alterations of the ECG pattern, indicating decreased cardiac output and ischaemia of the cardial muscle. The blood pressure decreases and respiratory function is also altered. The presence of such a toxic factor in sufficient concentration in the blood serum may explain the cardiovascular complications observed in some burned patients.