Impact of burn size and initial serum albumin level on acute renal failure occurring in major burn

BACKGROUND: Acute renal failure (ARF) is not a rare occurrence in severe burns and is an important complication leading to an increase in mortality. The severity of the burn is largely determined by the burn size, and severe burns are likely to cause enough loss of extracellular fluid and albumin from plasma volume to produce shock and hypoalbuminemia. HYPOTHESIS: We hypothesized that initial serum albumin level may be useful as an indicator of prognosis and severity of injury in burned patients. METHODS: The clinical characteristics of 147 adult patients with second- and third-degree burns covering 30% or more of their body surface area were analyzed retrospectively. Logistic regression was used to estimate the relative risks of ARF and mortality associated with the larger burn size and the lower serum albumin level at admission. RESULTS: Mean burned body surface was 60.0 +/- 21.8% (range 30-100%). Twenty-eight (19.0%) out of 147 patients experienced ARF, defined as a serum creatinine > or = 2 mg/dl, during the admission. The patients with ARF had larger burn size (79.5 +/- 15.4 vs. 55.3 +/- 20.5%, p < 0.0001) and lower serum albumin concentration at admission (1.92 +/- 0.66 vs. 2.48 +/- 0.82 g/dl, p < 0.0005) compared with those without ARF. All patients with ARF expired, whereas 29.4% (35/119) of the patients without ARF died. The burn size > or = 65% was associated with a risk of ARF that was 9.9 times and with a risk of death that was 14.2 times as high as that for the burn size <65%. The initial serum albumin level <2.5 g/dl was associated with a risk of death that was 2.7 times as high as that for the initial serum albumin level > or = 2.5 g/dl. CONCLUSIONS: When major burns are complicated by ARF, the mortality rate increases significantly. Burn size is an independent predictor of ARF occurring in major burns. Initially depressed serum albumin level is associated with an increase in mortality in the major burn patients.     

Influence of demographics and inhalation injury on burn mortality in children

BACKGROUND: Pulmonary failure has emerged as one of the leading causes of mortality in burned children due, in part, to the success in reducing the incidence of sepsis, early surgery and fluid resuscitation, and new advances in nutritional support. To evaluate the effect of pulmonary injury, age, gender, race, and burn size on mortality, the records of 3179 burned children admitted to our burn center from 1985 to 2001 were reviewed. In this population, 1246 were admitted within 14 days of injury with burns greater than 20% of their total body surface area (TBSA). METHODS: Lethal burn areas (LAs) for a thermal injury only or burn plus inhalation injury were estimated from best fit probit curve within 95% confidence limits. Data analysis was by chi(2)-test, t-test, or Fisher's exact test where appropriate. RESULTS: The lethal burn area for a 10% mortality rate with and without concomitant inhalation injury was a 50 and 73% TBSA burn, respectively. Children up to the age of 3 with >/=20% TBSA burns had a higher rate of mortality (9.9%) compared to those 3-12 years of age (4.9%) and 13-18 years of age (4.2%). Children with 21-80% TBSA burns showed a significant difference in mortality (P<0.05) between those with burn plus inhalation injury (13.9%) and burn only (2.9%), while those with 81-100% TBSA burns showed no significant difference between burn only and burn plus inhalation injury. CONCLUSION: Inhalation injury remains one of the primary contributors to burn mortality. Children under the age of 3 years, however, are at a higher risk both with and without inhalation injury.     

Mortality determinants in massive pediatric burns. An analysis of 103 children with > or = 80% TBSA burns (> or = 70% full-thickness).

OBJECTIVE: Survivors and nonsurvivors among 103 consecutive pediatric patients with massive burns were compared in an effort to define the predictors of mortality in massively burned children. SUMMARY BACKGROUND DATA: Predictors of mortality in burns that are used commonly are age, burn size, and inhalation injury. In the past, burns over 80% of the body surface area that are mostly full-thickness often were considered fatal, especially in children and in the elderly. In the past 15 years, advances in burn treatment have increased rates of survival in those patients treated at specialized burn centers. The purpose of this study was to document the extent of improvement and to define the current predictors of mortality to further focus burn care. METHODS: Beginning in 1982, 103 children ages 6 months to 17 years with burns covering at least 80% of the body surface (70% full-thickness), were treated in the authors' institution by early excision and grafting and have been observed to determine outcome. The authors divided collected independent variables from the time of injury into temporally related groups and analyzed the data sequentially and cumulatively through univariate statistics and through pooled, cross-sectional multivariate logistic regression to determine which variables predict the probability of mortality. RESULTS: The mortality rate for this series of massively burned children was 33%. Lower age, larger burn size, presence of inhalation injury, delayed intravenous access, lower admission hematocrit, lower base deficit on admission, higher serum osmolarity at arrival to the authors' hospital, sepsis, inotropic support requirement, platelet count < 20,000, and ventilator dependency during the hospital course significantly predict increased mortality. CONCLUSIONS: The authors conclude that mortality has decreased in massively burned children to the extent that nearly all patients should be considered as candidates for survival, regardless of age, burn size, presence of inhalation injury, delay in resuscitation, or laboratory values on initial presentation. During the course of hospitalization, the development of sepsis and multiorgan failure is a harbinger of poor outcome, but the authors have encountered futile cases only rarely. The authors found that those patients who are most apt to die are the very young, those with limited donor sites, those who have inhalation injury, those with delays in resuscitation, and those with burn-associated sepsis or multiorgan failure.     

Radiological manifestation of pulmonary complications in deceased intensive care burn patients

The chest radiographs of 46 burn patients who died in the burn intensive care unit (BICU) were retrospectively analyzed to study the spectrum of pulmonary complications and their contribution to patient's mortality. There were 25 male and 21 female patients and their mean ages were 34 and 30 years, respectively. Forty-three patients had flame burns, two chemical, and one scald with a mean total burn surface area (TBSA) of 71%. Thirty-six of them had inhalation injury and of these 25 patients developed septicaemia. Out of these 46 patients, 39 had a total of 60 pulmonary complications on various postburn days. The commonest complications were consolidation (28.3%) and adult respiratory distress syndrome (ARDS) (26.7%) mainly due to inhalation injury and/or following septicaemia. The majority of these complications (46.7%) occurred in the late phase (postburn day 5 onwards). Forty-one (89.2%) patients died due to multi-organ failure (MOF) and a good number of them had secondary respiratory failure. The flame burn patients with large TBSA, presence of inhalation injury, and occurrence of septicaemia, are at risk for pulmonary complications that equally affect adult males and females. Pulmonary complications irrespective of the cause significantly contribute to the mortality. This study suggests that serial chest X-rays done in BICU form an important diagnostic tool for pulmonary complications from postburn day 1 onwards, and is useful for subsequent monitoring of the treatment. All burn intensive care units may not be privileged to have a full time radiologist, and intensivist. Therefore, the burn surgeon needs to metamorphose into an intensivist and double as a burn radiologist for early detection and quick treatment if his surgical skills are to be adequately rewarded.     

Burns in pregnancy

A 9-year prospective study of burns in pregnant women hospitalized at the Sina hospital burn center was conducted to determine the etiology and outcome of pregnant patients. Fifty-one patients (27.45% self-inflicted, 72.55% unintentional) were identified and stratified by age, burn size, presence or absence of inhalation injury, trimester of pregnancy, maternal and fetal mortality, and cause of burn. The mean patient age was 24.2 years. There were 20 maternal deaths and 23 fetal deaths. The majority of which (maternal: 13 and fetal: 13) were among self-inflicted burned pregnant women. The mean burn size was 37.7%, and was significantly larger for nonsurvivors of mother than survivors (68.8% versus 17.6%; p<0.001). In the 51 pregnant women, as the total burned body surface area exceeds 40%, both maternal and fetal mortality reaches 100%. Inhalation injuries were strongly associated with large burns, and were presents in all suicide patients. Kerosene ignition (68.6% of all patients, 100% of self-inflicted patients) was the most common type of burn. Large burn size was the strongest predictor of mortality of mother and fetus followed by the presence of inhalation injury.     

Resurgence of methamphetamine related burns and injuries: A follow-up study

Purpose

Legislation enacted to curb methamphetamine production has only temporarily succeeded. Experiencing a recent increase in burns as a result of the new one-pot method, we compared methamphetamine related burn patients who utilized the previous anhydrous ammonia method of production to current patients who largely used the new one-pot method of production.

Basic procedures

Patients who were burned as a result of methamphetamine production were retrospectively reviewed. Comparisons were made including demographics, length of stay, injury severity score, hospital charges, total body surface area burned, inhalation injury, intubation, ventilator days, toxicology, fluid volumes, surgeries and complications.

Main findings

Eighteen current study patients (88.9% male) were compared to twenty-nine (86.2% male) previous study patients. The groups were similar in age, pattern of burn injury and intubation. Total body surface area burned, injury severity score, inhalation injuries, and ventilator days were not significantly increased in the current study. Longer length of stay and greater hospital charges were incurred by the current group. Burn surgeries per patient were significantly increased in the current group.

Principal conclusions

A new one-pot method has emerged despite legislative attempts to curtail methamphetamine production, and burns have also increased. The reason for more extensive burn surgeries in the current METH related burn patients remains enigmatic. Severity of injury and cost to society remain high.     

Helicopter transportation of burn patients

Analysis of 437 consecutive acute burn patients transported to our burn center revealed 339 transported by ground and 98 by helicopter. There were 18 air transport patients from within a 25-mile-radius, and 80 flown further than 25 miles. Mean age was the same in all groups (P>0.05). Percent total body surface area (TBSA) burned was 8.26% in ground transport patients, significantly less than the 20.35% (within 25 miles) and 21.40% (greater than 25 miles) seen in helicopter transports (P<0.0001). Three percent of ground transport patients and 28% of helicopter patients had inhalation injury (P<0.0001). There was no difference in incidence of inhalation injury among helicopter groups (28 vs. 29%, P=0.8). In patients with coexistent inhalation injury, the mean TBSA burned was significantly larger when compared with the TBSA of burns without inhalation injury (P<0.001). Air transported groups contained patients whose status was not critical based upon lack of inhalation injury and small burn size, and who could have been transported by ground. Non clinical factors such as insurance status, desire to keep ground ambulances in their community, and competing helicopter services reluctant to refuse to transport a patient appears to be factors in choosing air ambulance transportation. Regional single helicopter services and regional cooperative ground ambulance services should reduce use of helicopter transport of burn patients when it is not clinically indicated.     

Microskin autografting in the treatment of burns over 70% of total body surface area: 14 years of clinical experience

Despite the fact that early excision and grafting have significantly improved burn outcomes, the management of severely burned patients whose burn size exceeds 70% total body surface area (TBSA) still represents a big challenge for burn surgeons all over the world. During the period of 1997-2010 at our centre, aggressive excision and microskin autografting were performed in 63 severely burned patients. Their burn sizes ranged from 70% to 98% TBSA with a mean of 84.9%. The average full-thickness burn was 66.3% (range, 29-94%). Thirty patients had concomitant inhalation injury. Two to 7 days after burn, these patients underwent aggressive excisions ranging from 25% to 60% TBSA and transplantation of microskin autograft overlaid with allograft. The ratios of donor-site to recipient-site surface area were between 1:6 and 1:18. Signs of epithelialization were shown within 35-55 days. The wound healing rate was 74.9% (176/235), with 51.1% of cases (120/235) healing completely and 23.8% (56/235) improving. Microskin autografting yielded an overall survival rate of 63.5%; only 23 patients died. Our clinical experience in using the microskin autografting for burn coverage suggests that the technique is very effective in covering extensive burns, and that it is particularly useful when graft donor sites are very limited due to its high utilization rate of donor site. The factors affecting the outcome of microskin autografting are discussed herein.     

Characterization of the immunosuppressive effect of burned tissue in an animal model

The immunosuppressive effect of burned tissue was studied using a mouse burn model. To evaluate the immunologic status an in vivo measure of cell-mediated immunity (CMI) involving contact sensitization of mice by painting the skin with dinitrofluorobenzene was used; mice were challenged 5 days later by painting the ear with the same antigen. Ear swelling in response to antigenic challenge was used as a quantitative measure of CMI; diminution in ear swelling in treatment mice compared to sensitized, unburned control mice indicated the degree of immunosuppression. A full-thickness steam burn covering 20% body surface ares (BSA) was profoundly immunosuppressive as reflected by ear swelling of 45 to 60% of that found in normal mice; partial thickness burns and burns of 10% BSA extent were not significantly immunosuppressive. Transfer into unburned mice of burned skin equivalent in size to a 20% BSA burn eschar resulted in marked immunosuppression, but transfer of smaller amounts of burned skin, or of larger amounts of unburned skin and normal and burned liver tissue, did not produce immunosuppression. Mice receiving a very high-temperature (300°C), dry burn were only slightly more suppressed than mice receiving a standard steam burn. Normal immunity was preserved in burned mice which received daily application of cerium nitrate to the wound for 7 days, but application of other topical agents commonly used in burn treatment did not preserve immunity. Postburn immunosuppression thus appears related quantitatively to toxic factors in burned skin, and these toxic factors can be abrogated in burned mice by the topical application of cerium nitrate.     

Legionnaire''s pneumonia complicating a thermal burn

The report describes a patient with 45 per cent BSA burns who developed Legionnaire's disease 3 days after the acute injury. The diagnosis of this life-threatening complication was late because most of its signs and symptoms can be encountered in the burned patient. This delay could have been fatal to the patient and required the evacuation of the burn centre for disinfection     

Mortality and morbidity among elderly people with burns--evaluation of data on admission

People aged >or=65 years represent a growing population within burns units in the Western world. In 2001, this group was reported to rise to 20% of such admissions. We reviewed the records of 265 burn cases with complete admission and discharge histories, from January 1990 to December 2003 in an A-level regional burns centre. The predictive value of age, gender, total body surface area burned (TBSA), inhalation trauma (IT), premorbid conditions and currently used burn scores (Baux, ABSI, Ryan) for haemodynamic or respiratory complications, mortality and morbidity were analysed. Additionally a subset of patients with diabetes mellitus and >30% total body surface area burned were reviewed. About 16% of all admissions with burns were >or=65 years of age, with a mortality rate of 30.6% (81/265). Only gender and premorbid conditions did not influence mortality. Haemodynamic and respiratory complications were significantly related to TBSA, presence of I and any of the three scores (all p<0.001). Among survivors (184/265), the median duration of hospital stay was 26.0 days. Factors contributing to a significantly increased length of stay were, in decreasing order, total body surface area burned, high levels of burn scores, inhalation trauma, flame injury and certain premorbid conditions (cardiovascular disease, alcoholism). About 77.7% of all patients were discharged either to a rehabilitation centre or back to their previous form of housing. This study showed that among burned people aged >or=65 years a good outcome as evaluated on discharge can be achieved. Studies pooling different centres' results are needed to improve the significance of conclusions drawn from these data.     

Extracorporeal Life Support for Severely Burned Patients with Concurrent Inhalation Injury and Acute Respiratory Distress Syndrome: Experience from a Military Medical Burn Center

BackgroundBoth inhalation injury and acute respiratory distress syndrome (ARDS) are risk factors that predict mortality in severely burned patients. Extracorporeal life support (ECLS) is widely used to rescue these patients; however, its efficacy and safety in this critical population have not been well defined. We report our experience of using ECLS for the treatment of severely burned patients with concurrent inhalation injury and ARDS.MethodsThis was a retrospective analysis of 14 patients collected from a single medical burn center from 2012 to 2019. All patients suffered from major burns with inhalation injury and ARDS, and were treated with ECLS.ResultsThe median total body surface area of deep dermal or full thickness burns was 94.5%, ranging 47.7-99.0 %. The median revised Baux score was 122.0, ranging 90.0-155.0. All patients developed ARDS with a median partial pressure of arterial oxygen to a fraction of inspired oxygen ratio of 61.5, ranging 49.0-99.0. Indications for ECLS included sustained hypoxemia and unstable hemodynamics. The median interval for initiating ECLS was 2.5 days, ranging 1.0-156.0 days. The median duration of ECLS was 2.9 days, ranging 0.3-16.7 days. The overall survival to discharge was 42.8%. Causes of death included sepsis and multiple organ failure. ECLS-related complications included cannulation bleeding, catheter-related infection, and hemolysis. The incidence of risk factors reported in literature were higher in non-survivors, including Baux>120, albumin < 3.0 g/dL, and lactate > 8 mmol/L.ConclusionsFor severely burned patients with concurrent inhalation injury and ARDS, ECLS could be a salvage treatment to improve sustained hypoxemia. However, the efficacy of hemodynamic support was limited. Identifying definite ECLS indications and rigorous patient selection would contribute to better clinical outcomes.     

Determinants of mortality in pediatric patients with greater than 70% full-thickness total body surface area thermal injury treated by early total excision and grafting

Recent advancements in burn care have improved the survival rates of victims with severe burn injuries. The total mortality rate in a series of 1,057 pediatric patients admitted to Shriners Burns Institute Galveston Unit between 1982 and 1986 was 2.7%. The burn size resulting in a 50% death rate was 95% of the total body surface area (TBSA). In this study 19 survivors and 13 nonsurvivors with greater than 70% full-thickness TBSA burn injuries were compared. All survivors were adequately resuscitated upon arrival 11% sustained an inhalation injury. Forty-six per cent of the nonsurvivors sustained an inhalation injury; 31% were not initially adequately resuscitated. The presence of preadmission shock and inhalation injury were early determinants of mortality with secondary renal, pulmonary, or cardiovascular collapse being the later predictors of mortality in these massively burned pediatric patients.     

Comparison of combat and non-combat burns from ongoing U.S. military operations

BACKGROUND: Military burns result from either combat or non-combat causes. We compared these etiologies from patients involved in ongoing conflicts to evaluate their impact and provide prevention recommendations. METHODS: All military patients with significant burns treated at the United States Army Institute of Surgical Research from April 2003 to May 2005 were reviewed. Injuries were categorized as having resulted from combat or non-combat causes. Demographics, burn severity and pattern, mortality, and early outcomes were compared. RESULTS: There were 273 burn patients seen with 63% injured in combat. A high early rate of non-combat injuries was noted. Feedback on non-combat burn prevention was provided to the combat theater, and the incidence of non-combat burns decreased. Mean age and time from injury to admission did not differ. The majority of combat injuries resulted from explosive device detonation. Waste burning, ammunition handling, and gasoline caused most non-combat injuries. Combat casualties had more associated and inhalation injuries and greater full-thickness burn size; total body surface area burned was equivalent. The hands and the face were the most frequently burned body areas. Mortality was 5% in combat and 2% in non-combat patients. The majority of survivors in both groups returned to military duty. CONCLUSIONS: The disparity in full-thickness burn size and incidence of inhalation and associated injuries resulted from differing mechanisms of injury, with explosions and penetrating trauma more common in combat wounds. Despite the severity of combat burns, mortality was low and outcomes generally good. Non-combat burns are preventable and have decreased in incidence.     

A model for predicting mortality among critically ill burn victims

Objective

To develop a model for predicting mortality among burn victims.

Methods

All casualties admitted to our intensive care burn unit (ICBU) with a diagnosis of thermal or inhalation injury were studied. Age, total and full-thickness body surface area (BSA) burned, presence of inhalation injury, gender, mechanism of injury, delay to ICBU admission and mechanical ventilation during the first 72 h were recorded. The 851 participants were randomly divided into derivation (671) and validation (180) sets. From univariate and multivariate logistic regression analyses a mortality predictive equation was derived.

Results

Mortality was 17.6%. In univariate analysis, all variables were significantly associated with mortality except mechanism of injury and delay to ICBU admission. In multivariate analysis, age, total and full-thickness BSA burned, female gender and early mechanical ventilation were independently associated with mortality.

Conclusions

We propose a mortality predictive equation for burned victims. In this model, MV and not inhalation injury is a mortality risk factor.     

A comparison of conservative versus early excision. Therapies in severely burned patients.

Early excision and grafting of small burn wounds is a generally accepted treatment. Early excision of burn injuries greater than 30% total body surface area (TBSA) in adults, however, has not been universally accepted. In this study, 85 patients whose ages ranged from 17 to 55 years with greater than 30% total body surface area (TBSA) burns were randomly assigned to either early excision or topical antimicrobial therapy and skin grafting after spontaneous eschar separation. Mortality from burns without inhalation injury was significantly decreased by early excision from 45% to 9% in patients who were 17 to 30 years of age (p less than 0.025). No differences in mortality could be demonstrated between therapies in adult patients older than 30 years of age or with a concomitant inhalation injury. Children (n = 259) with similar large burns treated by early excision showed a significant increase in mortality with increasing burn size and with concomitant inhalation injury (p less than 0.05). The mean length of hospital stay of survivors was less than one day per per cent of TBSA burn in both children and adults.     

The role of inhalation injury in burn trauma. A Canadian experience.

From 1977 to 1987, 1705 thermally injured patients were admitted to the Firefighters' Burn Center at the University of Alberta Hospitals. Thirteen hundred forty-four were male (78.8%) and 361 were female (21.2%), with a mean total burn surface area (TBSA) of 15.1 (SEM +/- 0.4%) and a range of 1% to 99% TBSA. Sixteen hundred thirty-five patients survived to be discharged from hospital, with an overall survival rate of 95.9%. One hundred twenty-four burn patients (7.3%) suffered concomitant inhalation injury diagnosed by bronchoscopy. Patients with inhalation injury suffered from larger TBSA (39.7% +/- 2.8% versus 12.2% +/- 0.3%; p less than 0.01) than those without inhalation injury. Inhalation injury increased the number of deaths from burn injury (34.7% versus 1.7%; p less than 0.01) independent of age and TBSA. Inhalation injury was associated with a threefold prolongation of hospital stay (23.7 +/- 0.7 versus 74.4 +/- 6.2 days; p less than 0.01) and was independent of age and TBSA. Multifactorial probit analysis was performed for both inhalation- and noninhalation-injured burned patients to allow TBSA and age adjusted rates of mortality for the burn population presented. The maximum detrimental effects of inhalation injury in burn patient outcome occurred when it coexisted with moderate (15% to 29% TBSA) to large (30% to 69% TBSA) thermal injuries. These data demonstrate that inhalation injury is an important comorbid factor in burn injury that increases the number of deaths substantially. Most importantly such injuries also independently prolong the duration of hospitalization in a highly unpredictable fashion as compared to patients with cutaneous burns only. As such our data illustrate the extreme importance of inhalation injury as a comorbid factor following thermal injury and reveal the present limitations for accurate quantification of the magnitude of respiratory tract injury accompanying thermal trauma.     

An analysis of 11,196 burn admissions and evaluation of conservative management techniques

We present an 8-year analysis (1993-2000) of 11,196 burn admissions with an average of 116.6 patients per month. Patients were largely treated by conservative techniques. The mean burn percentage was 50.35. Almost 80% of admissions were in the 16-55 years age group. Paediatric and geriatric burns were 17.1 and 3.1%, respectively. Flame burns accounted for 82.15% of admissions and of these 77.5% were sustained in the kitchen. A total of 35.32% of flame accidents were due to malfunctioning kerosene pressure stove. The overall mortality was 51.80%. These figures need further qualification because 46.8% of patients had more than 50% BSA burns and 50.72% patients reported to the hospital more than 6h after sustaining burns. Patients with <60% BSA burns, and who were received within 6h of injury had a mortality of 23% only. Significantly, 1078/1952 deaths (55.23%) of patients <60% BSA burns took place in first 6 days of admission when 3639 patients with <60% BSA injury were received more than 6h after burn injury. This reflects that even if economic constraints preclude one from having the best infrastructure reasonable mortality rates are still achievable with conservative line of management, even in face of a heavy work load. This also makes one question the cost effectiveness of high cost technology in burn management.     

Effect of inhalation injury on fluid resuscitation requirements after thermal injury

The presence of inhalation injury has been reported to increase fluid requirements for resuscitation from burn shock after thermal injury. To evaluate the effect of inhalation injury on the magnitude of burn-induced shock, the characteristics of resuscitation of 171 patients with burns covering at least 25 percent of the total body surface area were reviewed. When inhalation injury was suspected, confirmation by xenon-133 scanning, bronchoscopy, or both was obtained. Initial fluid resuscitation was calculated according to the Parkland formula, and titration was initiated to maintain a urine output of 30 to 50 ml/hour. Fifty-one patients had inhalation injuries. Patients with inhalation injuries had a mean fluid requirement of 5.76 ml/kg per percentage of total body surface area burned and a mean sodium requirement of 0.94 mEq/kg per percentage of total body surface area burned to achieve successful resuscitation, compared with a fluid requirement of 3.98 ml/kg per percentage of total body surface area burned and a sodium requirement of 0.68 mEq/kg per percentage of total body surface area burned for the group without inhalation injury (p less than 0.05). These data confirm and quantitate that inhalation injury accompanying thermal trauma increases the magnitude of total body injury and requires increased volumes of fluid and sodium to achieve resuscitation from early burn shock.