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Effect of inhalation injury on fluid resuscitation requirements after thermal injury
Effect of Inhalation Injury on Fluid Resuscitation Requirements After Thermal Injury
Paul D. Navar, MD, Salt Lake City, Utah Jeffrey R. Saffle, MD, Salt Lake City, Utah Glenn D. Warden, MD, Salt Lake City, Utah
The presence of inhalation injury is generally thought to increase the fluid requirements for resuscitation from burn shock after thermal injury [l-3]. At the 1980 National Institutes of Health consensus conference, Baxter [4] noted that patients with large burns and concomitant inhalation injury have the largest fluid requirements. Scheulen and Munster [2] found a 37 percent increase in fluid requirements when inhalation injury was present; however, no one has proposed a specific modification of resuscitation formulas to accommodate the presence of inhalation injury. To address this concept, the fluid requirements of all patients treated over a 6 year period at our burn center are reviewed herein. Material and Methods The resuscitation characteristics of 171 patients with burns covering at least 25 percent of the total body surface area treated between 1978 and 1984 were reviewed. Patients with high-voltage electric current injuries and those who did not survive the initial 24 hour resuscitation period were excluded. Burn wounds covering at least 25 percent of the total body surface area were selected because lesser injuries did not usually require formal resuscitation. In all patients who suffered flame burns, inhalation injury was suspected when suggestive physical findings, such as carbonaceous sputum, facial burns, hoarseness, dyspnea, abnormal blood gas values, or abnormal chest roentgenographic findings, were demonstrated on admission. In all cases, inhalation injury was confirmed by xenon-133 scanning, bronchoscopy, or both [5]. Initial fluid resuscitation for each patient was initiated From the Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah. Requests for reprints should be addressed to Jeffrey R. Saffle, MD, Department of Surgery, #38306, University of Utah Medical Center, 50 North Medical Drive, Salt Lake City, Utah 64132. Presented at the 37th Annual Meeting of the Southwestern Surgical Congress, Las Vegas, Nevada, April 28-May 2, 1985.
716
according to the Parkland formula (4 ml Ringer’s lactate solution per kilogram of body weight per percentage of total body surface area burned). This formula was utilized only to estimate initial fluid requirements, which were subsequently adjusted according to clinical response, the primary criterion being the maintenance of adequate urine output. Fluid infusion was titrated to maintain a urine output of 30 to 50 ml/kg per hour in adults, and 1 ml/kg per hour in children. Patients without maintenance of that rate of urine output were given increasing volumes of crystalloid solution as needed. In several instances, those who required unusually large fluid volumes were switched to a resuscitation regimen based on hypertonic lactated saline solution (sodium 180 to 230 mEq/liter) in an attempt to minimize fluid intake and restore urine output [6]. Swan-Ganz catheters were utilized in only a few high risk patients. Resuscitation was considered to be complete when patients maintained adequate urine output for 2 consecutive hours at an infusion equivalent to calculated maintenance requirements. Maintenance fluid requirements are increased in patients with major burns and were predicted by the following formula [7]: total maintenance requirements equal basal requirements plus evaporative loss. In adults, it was calculated as 87.5 ml/hour + percentage of total body surface area burned X body surface area (Ms). In children, it was calculated as 97.5 ml/hour + the percentage of total body surface area burned X body surface area (M2). Data are presented as the mean f the standard error of the mean. The Student’s t test was used for statistical evaluation of paired groupings. p <0.05 was considered significant. FbSUitS
The patient population is summarized in Table I. Fifty-one patients had documented inhalation injuries, all of whom suffered flame burns. Of 120 patients without inhalation injury, 23.4 percent were scalded. The two groups did not differ significantly in regard to mean burn size, but differed slightly
The American
Journal of Surgery
Inhalation
TABLE I
Summary of Patient and Resuscitation
p Value
120
28.88 1-62
21.97 l-59
<0.05
45.75 25-90
42.93 25-91
NS
30.04 O-78
16.82 O-65
<0.05
39 (76.5)’ 12 (23.5)
91 (75.8) 29 (24.2)
51 (100)
5.76 f 0.39
92 (76.6) 28 (23.4) 15 3.98 f 0.19
0.94 f 0.06
0.65 f 0.03
<0.05
23.81 f 0.74
<0.05
Age (Y;)
Mean Range Burn Size (% TBSA) Mean Range Full-thickness burn size (% TBSA) Mean Range Sex Male Female Cause Flame Scald Mortality (%) Resuscitation fluid requirement (ml/kg/ % TBSA) Resuscitation sodium requirement (mEq/kg/% TBSA) Duration of resuscitation
Inhalation Injury Absent
51
No. of oatients
iii
29.82 f
Requirements
Data
Present
Parameters
Injury and Fluid Resuscitation
1.33
(h) * Numbers in parentheses indicate percentages. NS = not significant; TBSA = total body surface area.
with respect to age and size of the full-thickness burns. Resuscitation data for the two groups are also presented. Patients with inhalation injury 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 resuscitation, compared with a fluid requirement of 3.98 ml/kg per percentage of total body surface area burned and a sodium requirement of 0.65 mEq/kg per percentage of total body surface area burned for patients without inhalation injuries (p <0.05). Patients with inhalation injuries also required a significantly longer time (29.82 versus 23.81 hours, p <0.05) to be completely resuscitated from burninduced shock. Because of the diversity in patient ages and sizes of the burns, and because the two groups were not completely similar with respect to these variables, resuscitation requirements were analyzed according to age and burn size (Table II). The presence of inhalation injury was associated with a remarkably uniform increase in fluid requirements for all age groups and burn sizes, although statistical significance was not reached in some cases because of the small sample size. Fluid requirements for patients with inhalation injuries were between 5.2 and 6.3 ml/kg per percentage of total body surface area burned, compared with 3.5 to 4.5 ml/kg per percentage of total body surface area burned for those pa-
Volume 150. December 1985
tients without inhalation injury. Requirements sodium were parallel to those for fluid.
for
Comments The presence of inhalation injury complicates many aspects of burn care, and in some ways represents an unsolved problem in treatment of burns. Inhalation injury greatly increases the anticipated rate of mortality for thermal injuries of all sizes, a fact that has not been altered by recent advances in other aspects of burn care [8,9]. Whereas most deaths from inhalation injury are secondary to pulmonary infection, pulmonary injury also complicates initial fluid resuscitation, and may increase mortality during the early postburn course [3]. Monafo et al [IO] found inhalation injury to be the principal cause of early death in patients with neartotal burns. Several investigators [1-31 have demonstrated that inhalation injury increases fluid requirements for resuscitation in both pediatric and adult populations. Our study confirms that patients with inhalation injuries require volumes of fluid in excess of those predicted by the Parkland formula. Our data suggest that the magnitude of increase in fluid requirements imposed by inhalation injury is remarkably constant regardless of age or the size of burns. The mean fluid requirement in our patients with inhalation injury was 5.76 ml/kg per percentage of total body surface area burned, whereas patients
717
Navar et al
TABLE II
Fluid and Sodium Resuscitation Requirements In Patients Wlth and Without Inhalation Injuries
Patient Age & Requirements*
25-39
Burn Size (% total body surface area) 40-60 <60
Totals
Patients With Inhalation Injuries O-5 yr n Fluid requirements Sodium requirements 6-35 yr n Fluid requirements Sodium requirements 36-62 yr n Fluid requirements Sodium requirements Total n Fluid requirements (average) Sodium requirements (average)
3 6.13 f 2.70 1.37 f 0.46
2 3.99 f 0.63 0.86 f 0.06
1 5.23 0.78
6 6.27 f 1.49 1.11 f 0.24
11 5.76 f 0.91 0.91 f 0.14
11 5.13 f 0.61 0.84 f 0.11
7 5.75 f 0.89 0.79 f 0.09
29 5.52 f 0.46 0.85 f 0.07
9 6.32 f 1.31 1.14 f 0.22
5 5.87 f 1.11 1.01 f 0.17
2 4.84 f 0.52 0.67 f 0.11
16 6 f 0.80 1.04 f 0.14
23 6.29 f 0.73
18 5.21 f 0.48
10 5.51 f 0.63
51 5.76 f 0.39
1.06 f 0.12
0.89 f 0.08
0.76 f 0.07
0.94 f 0.06
Patients Without Inhalation Injuries O-5 yr n Fluid requirements Sodium requirements 6-35 yr n Fluid requirements Sodium requirements 35-62 yr n Fluid requirements Sodium requirements Total n Fluid requirements (mean) Sodium requirements (mean)
17 4.57 f 0.48+ 0.81 f 0.08+
7 5.14 f 0.59 0.82 f 0.11
2 4.05 l 0.95 0.61 f 0.11
26 4.68 f 0.35 0.80 f 0.06
30 3.06 f 0.28+ 0.54 f 0.04+
30 4.24 f 0.44 0.64 f 0.06
a 4.54 f 0.99 0.68 f 0.16
68 3.75 f 0.26+ 0.60 f 0.04+
9 3.52 f 0.71 0.49 f 0.08+
14 4.35 f 0.42 0.75 f 0.08
3 2.77 f 0.37 0.47 f 0.04
26 3.89 f 0.34+ 0.63 f 0.05+
56 3.59 f 0.25+
51 4.40 f 0.29
13 4.06 f 0.64
120 3.98 f 0.19+
0.62 f 0.04+
0.69 f 0.04
0.62 f 0.10
0.65 f 0.03+
All fluid requirements and sodium requirements are expressed as ml/kg/ % of total body surface area and mEq/kg/ % total body surface area, respectively. + p (0.05, when compared with the corresponding values in the group with inhalation injuries. l
without pulmonary damage required fluid volumes almost exactly equal to the guidelines of the Parkland formula. This 44 percent increase in fluid requirements is consistent with the 37 percent increase described by Scheulen and Munster [2]. We believe that the Parkland formula should be modified accordingly for estimating the fluid requirements of patients with inhalation injuries. Debate continues over the most appropriate parameters for assessing the adequacy of fluid resuscitation during burn shock. In our study, fluids were titrated to maintain urine output at a commonly accepted level of 30 to 50 ml/kg per hour for adults and 1 ml/kg per hour for children. It has been suggested that burn patients with inhalation injuries be
718
given minimal fluids in order to lessen the deleterious effects of increased fluid infusion on pulmonary function. Scheulen and Munster [2] have suggested that much lower urine outputs should be acceptable in resuscitating patients with inhalation injuries, but such a policy may be incorrect or even dangerous. There is no consistent evidence that resuscitation, even with large volumes of crystalloid solution, adversely affects pulmonary function. Tranbaugh et al [11] found that extravascular lung water is only rarely increased in patients with severe inhalation injury after fluid resuscitation, whereas Herndon et al [12] recently demonstrated that such an accumulation progresses for several days after fluid resuscitation and may be more dependent on
The American Journal of Surgery
Inhalation injury
the magnitude of inhalation injury than on the volof resuscitation fluid employed. These findings are consistent with the classic observation that pulmonary edema is characteristically absent for 48 to 72 hours after thermal injury [8]. It has similarly been argued that colloid-containing fluids may be superior to crystalloid solution in the resuscitation of patients with inhalation injury, but Goodwin et al [13] did not show any advantage of early colloid resuscitation, and in fact, demonstrated a progressive increase in extravascular water in the lungs over a 7 day period, which was not observed in the group resuscitated with crystalloid solution. Resuscitation with crystalloid solution may be superior to resuscitation with colloid solution because of its more transient effect on lung water. At the 1980 NIH consensus conference on burn care, Pruitt [I43 stated that the goal of fluid resuscitation is the preservation of vital organ function. The maintenance of adequate urine output is therefore itself a major goal of fluid therapy, as well as an indirect indicator of intravascular volume and cardiovascular function. Baxter and Shires [4] demonstrated that fluid resuscitation, even by the Parkland formula, which is the most generous of standard regimens, maintains intravascular volume at levels below the normal range. Monitoring of cardiac output has been suggested as a more accurate parameter of fluid resuscitation. Although cardiac output determinations can be of value in resuscitating patients with marginal cardiac reserve, fluctuations in cardiac output are probably not sensitive enough to provide hourly information about organ perfusion and intravascular volume. Patients with inhalation injuries have lower cardiac output than that of patients with burn injuries of equivalent size 141. Resuscitation of such patients to restore normal cardiac function may require increased quantities of fluid [13]. Agarwal et al [3] demonstrated that elderly patients who died, most of whom had inhalation injury, had higher pulmonary capillary wedge pressures and lower cardiac outputs than elderly patients who survived. This seemed to reflect a profound decrease in cardiac function rather than inappropriate fluid overload. The patient with inhalation injury presents a challenge in many aspects of burn care, especially fluid resuscitation. Such patients are comparable to patients with high-voltage electric current injuries or extensive fourth degree burns in that their fluid requirements reflect an increased magnitude of injury. We believe that restricting fluid resuscitation below pPy.siologic requirements represents an error in priorities. Resuscitation formulas are simply guidelines to fluid therapy and should be continuously adjusted according to response of the patient. It is likely that fluid resuscitation for burn patients with inhalation injuries could be simplified if an infusion of 5.5 to 5.75 ml/kg per percentage of total ume
Volume 150, December 1985
and Fluid Resuscitation Requirements
body surface area burned was used as an initial estimate of resuscitation needs. Summary 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 <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. References 1. O’Neill 2. 3. 4.
5.
6. 7. 8.
9.
10. 11.
JA. Fluidresuscitation in the burned child: a reappraisal. J Pediatr Surg 1982; 17:604-7. Scheulen JJ, Munster AM. The Parkland formula in patients with burns and inhalation injury. J Trauma 1982;22:869-71. Agarwal N, Petro J, Salisbury RE. Physiologic profile monitoring in burned patients. J Trauma 1982;23:577-83. Baxter CR, Shires GT. Guidelines for fluid resuscitation. Proceedings of the Second Consensus Development Confetence on Supportive Therapy in Burn Care. .J Trauma 1981;21 (suppl):687-9. Moylan JA, Wilmore DW, Mouton DE, et al. Early diagnosis of inhalation injury using xenon-133 lung scan. Ann Surg 1972;176:477-84, Moylan JA, Reckler JM, Mason AD. Resuscitation with hypertonic saline in thermal injury. Am J Surg 1973;125:580-4. Moncrief JA. In: Artz CP, Moncrief JA, Pruitt BA Jr, eds. Burns: a team approach. Philadelphia: WE Saunders, 197923-44. Achauer BM, Allyn PA, Furnas DW, Bartlett RI-I. Pulmonary complications of burns: the major threat to the burn patient. Ann Surg 1973;178:311-9. Thompson P, Herndon DN, Abston S. Effect on mortality of inhalation injury. Proceedings of the American Burn Association, 17th Annual Meeting, Orlando, Florida, March 27-30, 1985. Monafo WW, Robinson HN, Yoshihara T, Azvazian VH. Lethal burns. Arch Surg 1978; 113:397-40 1. Tranbaugh RF, Elings VB, Christiansen JM, Lewis FR. Effect of inhalation injury on lung water accumulation. J Trauma
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1983;23:597-604. 12. Herndon DN, Stein MD, Rutan TC, Abston S. Predictors of mortality in patients with inhalation injury. Proceedings of the American Burn Association, 17th Annual Meeting, Orlando, Florida, March 27-30, 1965. 13. Goodwin CW, Dorethy J, Lam V, Pruitt BA Jr. Randomized trial of efficacy of crystalloid and colloid resuscitation on hemodynamic response and lung water following thermal injury. Ann Surg 1983;197:520-31. 14. Pruitt BA Jr. Summary, fluid resuscitation. Proceedings of the Second Consensus Development Conference on Supportive Therapy in Burn Care 8 Trauma 198 1.
Diiussion John L. Hunt (Dallas, TX): Dr. Navar, you have presented an important topic that up to now has been believed to be true, but has been based only on anecdotal information. There is now hard data to confirm that patients with inhalation injuries require additional fluid. Dr. Navar, you arbitrarily chose to include burns covering more than 25 percent of the total body surface area for evaluation of inhalation injury. In our experience, more than a third of patients with inhalation injuries have burns covering less than 25 percent of the total body surface area. Do you have any information on fluid requirements in such patients? The patients with inhalation injury had a significantly greater component of third degree burns compared with those without an inhalation injury, which in itself could account for a major portion of the excess fluid that was administered to the patients in the inhalation group. Could you comment further on this? Your unit is unique in that many of your patients are transferred from regions outside of Salt Lake City, and consequently a delay in treatment or inadequate resuscitation is apparently common. We have the clinical impression that patients with delayed or inadequate resuscitation often require more fluid than would be anticipated by most formulas. Dr. Navar, could you also comment on whether there are any subgroups of patients with inhalation injuries who seemed to be more prone to pulmonary complications? Inhalation injuries in general are associated with a increased number of pulmonary complications, but are
720
there certain patients, characterized by age or percentage of burns, in whom this is more common? Again, I would like to reemphasize what your group has stated, that patients probably have more harm done to them by underresuscitation than overresuscitation. No formula is ideal for all patients, and they must be monitored frequently. Paul D. Navar (closing): Dr. Hunt, we did not include patients with smoke inhalation who had burns over less than 25 percent of the total body surface area. A higher incidence of long-term pulmonary complications occurred in the patients with inhalation injury. There was no evidence from the study that this was due to increased amounts of intravenous fluid. As previously mentioned, those patients with inhalation injury who ultimately died did not require more fluid than the group as a whole. Several studies have shown that extravascular lung water is only rarely increased in patients with severe inhalation injury. It is well known that patients with an increased component of third degree burns require more fluid to achieve resuscitation than those patients with lesser third degree burn injury, as you pointed out, Dr. Hunt. In our series, there was a slight increase in fluid requirements with increasing burn size in patients without inhalation injuries. However, this did not exceed 4.4 ml/kg per percentage of total body surface area in the groups with greater than 40 percent of total body surface area burned, where one would expect a correspondingly increased component of third degree burn. This was in contrast to the fluid requirement of 5.5 to 6 ml/kg per percentage of total body, surface area seen in the group with inhalation injury with burns of less than 40 percent of total body surface area. We concluded that the increased component of third degree burns seen in the group with inhalation injury plays only a minor part in the significant increase in fluid requirements seen in these patients. Delay in the initiation of resuscitation is a feature of our burn unit in Salt Lake City because many of our patients are transported by air from outlying areas. We did see a delay in resuscitation in both groups, however, this did not predominate in one group or the other.
The American Journal of Surgery
Paul D. Navar, MD, Salt Lake City, Utah Jeffrey R. Saffle, MD, Salt Lake City, Utah Glenn D. Warden, MD, Salt Lake City, Utah
The presence of inhalation injury is generally thought to increase the fluid requirements for resuscitation from burn shock after thermal injury [l-3]. At the 1980 National Institutes of Health consensus conference, Baxter [4] noted that patients with large burns and concomitant inhalation injury have the largest fluid requirements. Scheulen and Munster [2] found a 37 percent increase in fluid requirements when inhalation injury was present; however, no one has proposed a specific modification of resuscitation formulas to accommodate the presence of inhalation injury. To address this concept, the fluid requirements of all patients treated over a 6 year period at our burn center are reviewed herein. Material and Methods The resuscitation characteristics of 171 patients with burns covering at least 25 percent of the total body surface area treated between 1978 and 1984 were reviewed. Patients with high-voltage electric current injuries and those who did not survive the initial 24 hour resuscitation period were excluded. Burn wounds covering at least 25 percent of the total body surface area were selected because lesser injuries did not usually require formal resuscitation. In all patients who suffered flame burns, inhalation injury was suspected when suggestive physical findings, such as carbonaceous sputum, facial burns, hoarseness, dyspnea, abnormal blood gas values, or abnormal chest roentgenographic findings, were demonstrated on admission. In all cases, inhalation injury was confirmed by xenon-133 scanning, bronchoscopy, or both [5]. Initial fluid resuscitation for each patient was initiated From the Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah. Requests for reprints should be addressed to Jeffrey R. Saffle, MD, Department of Surgery, #38306, University of Utah Medical Center, 50 North Medical Drive, Salt Lake City, Utah 64132. Presented at the 37th Annual Meeting of the Southwestern Surgical Congress, Las Vegas, Nevada, April 28-May 2, 1985.
716
according to the Parkland formula (4 ml Ringer’s lactate solution per kilogram of body weight per percentage of total body surface area burned). This formula was utilized only to estimate initial fluid requirements, which were subsequently adjusted according to clinical response, the primary criterion being the maintenance of adequate urine output. Fluid infusion was titrated to maintain a urine output of 30 to 50 ml/kg per hour in adults, and 1 ml/kg per hour in children. Patients without maintenance of that rate of urine output were given increasing volumes of crystalloid solution as needed. In several instances, those who required unusually large fluid volumes were switched to a resuscitation regimen based on hypertonic lactated saline solution (sodium 180 to 230 mEq/liter) in an attempt to minimize fluid intake and restore urine output [6]. Swan-Ganz catheters were utilized in only a few high risk patients. Resuscitation was considered to be complete when patients maintained adequate urine output for 2 consecutive hours at an infusion equivalent to calculated maintenance requirements. Maintenance fluid requirements are increased in patients with major burns and were predicted by the following formula [7]: total maintenance requirements equal basal requirements plus evaporative loss. In adults, it was calculated as 87.5 ml/hour + percentage of total body surface area burned X body surface area (Ms). In children, it was calculated as 97.5 ml/hour + the percentage of total body surface area burned X body surface area (M2). Data are presented as the mean f the standard error of the mean. The Student’s t test was used for statistical evaluation of paired groupings. p <0.05 was considered significant. FbSUitS
The patient population is summarized in Table I. Fifty-one patients had documented inhalation injuries, all of whom suffered flame burns. Of 120 patients without inhalation injury, 23.4 percent were scalded. The two groups did not differ significantly in regard to mean burn size, but differed slightly
The American
Journal of Surgery
Inhalation
TABLE I
Summary of Patient and Resuscitation
p Value
120
28.88 1-62
21.97 l-59
<0.05
45.75 25-90
42.93 25-91
NS
30.04 O-78
16.82 O-65
<0.05
39 (76.5)’ 12 (23.5)
91 (75.8) 29 (24.2)
51 (100)
5.76 f 0.39
92 (76.6) 28 (23.4) 15 3.98 f 0.19
0.94 f 0.06
0.65 f 0.03
<0.05
23.81 f 0.74
<0.05
Age (Y;)
Mean Range Burn Size (% TBSA) Mean Range Full-thickness burn size (% TBSA) Mean Range Sex Male Female Cause Flame Scald Mortality (%) Resuscitation fluid requirement (ml/kg/ % TBSA) Resuscitation sodium requirement (mEq/kg/% TBSA) Duration of resuscitation
Inhalation Injury Absent
51
No. of oatients
iii
29.82 f
Requirements
Data
Present
Parameters
Injury and Fluid Resuscitation
1.33
(h) * Numbers in parentheses indicate percentages. NS = not significant; TBSA = total body surface area.
with respect to age and size of the full-thickness burns. Resuscitation data for the two groups are also presented. Patients with inhalation injury 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 resuscitation, compared with a fluid requirement of 3.98 ml/kg per percentage of total body surface area burned and a sodium requirement of 0.65 mEq/kg per percentage of total body surface area burned for patients without inhalation injuries (p <0.05). Patients with inhalation injuries also required a significantly longer time (29.82 versus 23.81 hours, p <0.05) to be completely resuscitated from burninduced shock. Because of the diversity in patient ages and sizes of the burns, and because the two groups were not completely similar with respect to these variables, resuscitation requirements were analyzed according to age and burn size (Table II). The presence of inhalation injury was associated with a remarkably uniform increase in fluid requirements for all age groups and burn sizes, although statistical significance was not reached in some cases because of the small sample size. Fluid requirements for patients with inhalation injuries were between 5.2 and 6.3 ml/kg per percentage of total body surface area burned, compared with 3.5 to 4.5 ml/kg per percentage of total body surface area burned for those pa-
Volume 150. December 1985
tients without inhalation injury. Requirements sodium were parallel to those for fluid.
for
Comments The presence of inhalation injury complicates many aspects of burn care, and in some ways represents an unsolved problem in treatment of burns. Inhalation injury greatly increases the anticipated rate of mortality for thermal injuries of all sizes, a fact that has not been altered by recent advances in other aspects of burn care [8,9]. Whereas most deaths from inhalation injury are secondary to pulmonary infection, pulmonary injury also complicates initial fluid resuscitation, and may increase mortality during the early postburn course [3]. Monafo et al [IO] found inhalation injury to be the principal cause of early death in patients with neartotal burns. Several investigators [1-31 have demonstrated that inhalation injury increases fluid requirements for resuscitation in both pediatric and adult populations. Our study confirms that patients with inhalation injuries require volumes of fluid in excess of those predicted by the Parkland formula. Our data suggest that the magnitude of increase in fluid requirements imposed by inhalation injury is remarkably constant regardless of age or the size of burns. The mean fluid requirement in our patients with inhalation injury was 5.76 ml/kg per percentage of total body surface area burned, whereas patients
717
Navar et al
TABLE II
Fluid and Sodium Resuscitation Requirements In Patients Wlth and Without Inhalation Injuries
Patient Age & Requirements*
25-39
Burn Size (% total body surface area) 40-60 <60
Totals
Patients With Inhalation Injuries O-5 yr n Fluid requirements Sodium requirements 6-35 yr n Fluid requirements Sodium requirements 36-62 yr n Fluid requirements Sodium requirements Total n Fluid requirements (average) Sodium requirements (average)
3 6.13 f 2.70 1.37 f 0.46
2 3.99 f 0.63 0.86 f 0.06
1 5.23 0.78
6 6.27 f 1.49 1.11 f 0.24
11 5.76 f 0.91 0.91 f 0.14
11 5.13 f 0.61 0.84 f 0.11
7 5.75 f 0.89 0.79 f 0.09
29 5.52 f 0.46 0.85 f 0.07
9 6.32 f 1.31 1.14 f 0.22
5 5.87 f 1.11 1.01 f 0.17
2 4.84 f 0.52 0.67 f 0.11
16 6 f 0.80 1.04 f 0.14
23 6.29 f 0.73
18 5.21 f 0.48
10 5.51 f 0.63
51 5.76 f 0.39
1.06 f 0.12
0.89 f 0.08
0.76 f 0.07
0.94 f 0.06
Patients Without Inhalation Injuries O-5 yr n Fluid requirements Sodium requirements 6-35 yr n Fluid requirements Sodium requirements 35-62 yr n Fluid requirements Sodium requirements Total n Fluid requirements (mean) Sodium requirements (mean)
17 4.57 f 0.48+ 0.81 f 0.08+
7 5.14 f 0.59 0.82 f 0.11
2 4.05 l 0.95 0.61 f 0.11
26 4.68 f 0.35 0.80 f 0.06
30 3.06 f 0.28+ 0.54 f 0.04+
30 4.24 f 0.44 0.64 f 0.06
a 4.54 f 0.99 0.68 f 0.16
68 3.75 f 0.26+ 0.60 f 0.04+
9 3.52 f 0.71 0.49 f 0.08+
14 4.35 f 0.42 0.75 f 0.08
3 2.77 f 0.37 0.47 f 0.04
26 3.89 f 0.34+ 0.63 f 0.05+
56 3.59 f 0.25+
51 4.40 f 0.29
13 4.06 f 0.64
120 3.98 f 0.19+
0.62 f 0.04+
0.69 f 0.04
0.62 f 0.10
0.65 f 0.03+
All fluid requirements and sodium requirements are expressed as ml/kg/ % of total body surface area and mEq/kg/ % total body surface area, respectively. + p (0.05, when compared with the corresponding values in the group with inhalation injuries. l
without pulmonary damage required fluid volumes almost exactly equal to the guidelines of the Parkland formula. This 44 percent increase in fluid requirements is consistent with the 37 percent increase described by Scheulen and Munster [2]. We believe that the Parkland formula should be modified accordingly for estimating the fluid requirements of patients with inhalation injuries. Debate continues over the most appropriate parameters for assessing the adequacy of fluid resuscitation during burn shock. In our study, fluids were titrated to maintain urine output at a commonly accepted level of 30 to 50 ml/kg per hour for adults and 1 ml/kg per hour for children. It has been suggested that burn patients with inhalation injuries be
718
given minimal fluids in order to lessen the deleterious effects of increased fluid infusion on pulmonary function. Scheulen and Munster [2] have suggested that much lower urine outputs should be acceptable in resuscitating patients with inhalation injuries, but such a policy may be incorrect or even dangerous. There is no consistent evidence that resuscitation, even with large volumes of crystalloid solution, adversely affects pulmonary function. Tranbaugh et al [11] found that extravascular lung water is only rarely increased in patients with severe inhalation injury after fluid resuscitation, whereas Herndon et al [12] recently demonstrated that such an accumulation progresses for several days after fluid resuscitation and may be more dependent on
The American Journal of Surgery
Inhalation injury
the magnitude of inhalation injury than on the volof resuscitation fluid employed. These findings are consistent with the classic observation that pulmonary edema is characteristically absent for 48 to 72 hours after thermal injury [8]. It has similarly been argued that colloid-containing fluids may be superior to crystalloid solution in the resuscitation of patients with inhalation injury, but Goodwin et al [13] did not show any advantage of early colloid resuscitation, and in fact, demonstrated a progressive increase in extravascular water in the lungs over a 7 day period, which was not observed in the group resuscitated with crystalloid solution. Resuscitation with crystalloid solution may be superior to resuscitation with colloid solution because of its more transient effect on lung water. At the 1980 NIH consensus conference on burn care, Pruitt [I43 stated that the goal of fluid resuscitation is the preservation of vital organ function. The maintenance of adequate urine output is therefore itself a major goal of fluid therapy, as well as an indirect indicator of intravascular volume and cardiovascular function. Baxter and Shires [4] demonstrated that fluid resuscitation, even by the Parkland formula, which is the most generous of standard regimens, maintains intravascular volume at levels below the normal range. Monitoring of cardiac output has been suggested as a more accurate parameter of fluid resuscitation. Although cardiac output determinations can be of value in resuscitating patients with marginal cardiac reserve, fluctuations in cardiac output are probably not sensitive enough to provide hourly information about organ perfusion and intravascular volume. Patients with inhalation injuries have lower cardiac output than that of patients with burn injuries of equivalent size 141. Resuscitation of such patients to restore normal cardiac function may require increased quantities of fluid [13]. Agarwal et al [3] demonstrated that elderly patients who died, most of whom had inhalation injury, had higher pulmonary capillary wedge pressures and lower cardiac outputs than elderly patients who survived. This seemed to reflect a profound decrease in cardiac function rather than inappropriate fluid overload. The patient with inhalation injury presents a challenge in many aspects of burn care, especially fluid resuscitation. Such patients are comparable to patients with high-voltage electric current injuries or extensive fourth degree burns in that their fluid requirements reflect an increased magnitude of injury. We believe that restricting fluid resuscitation below pPy.siologic requirements represents an error in priorities. Resuscitation formulas are simply guidelines to fluid therapy and should be continuously adjusted according to response of the patient. It is likely that fluid resuscitation for burn patients with inhalation injuries could be simplified if an infusion of 5.5 to 5.75 ml/kg per percentage of total ume
Volume 150, December 1985
and Fluid Resuscitation Requirements
body surface area burned was used as an initial estimate of resuscitation needs. Summary 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 <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. References 1. O’Neill 2. 3. 4.
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6. 7. 8.
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10. 11.
JA. Fluidresuscitation in the burned child: a reappraisal. J Pediatr Surg 1982; 17:604-7. Scheulen JJ, Munster AM. The Parkland formula in patients with burns and inhalation injury. J Trauma 1982;22:869-71. Agarwal N, Petro J, Salisbury RE. Physiologic profile monitoring in burned patients. J Trauma 1982;23:577-83. Baxter CR, Shires GT. Guidelines for fluid resuscitation. Proceedings of the Second Consensus Development Confetence on Supportive Therapy in Burn Care. .J Trauma 1981;21 (suppl):687-9. Moylan JA, Wilmore DW, Mouton DE, et al. Early diagnosis of inhalation injury using xenon-133 lung scan. Ann Surg 1972;176:477-84, Moylan JA, Reckler JM, Mason AD. Resuscitation with hypertonic saline in thermal injury. Am J Surg 1973;125:580-4. Moncrief JA. In: Artz CP, Moncrief JA, Pruitt BA Jr, eds. Burns: a team approach. Philadelphia: WE Saunders, 197923-44. Achauer BM, Allyn PA, Furnas DW, Bartlett RI-I. Pulmonary complications of burns: the major threat to the burn patient. Ann Surg 1973;178:311-9. Thompson P, Herndon DN, Abston S. Effect on mortality of inhalation injury. Proceedings of the American Burn Association, 17th Annual Meeting, Orlando, Florida, March 27-30, 1985. Monafo WW, Robinson HN, Yoshihara T, Azvazian VH. Lethal burns. Arch Surg 1978; 113:397-40 1. Tranbaugh RF, Elings VB, Christiansen JM, Lewis FR. Effect of inhalation injury on lung water accumulation. J Trauma
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1983;23:597-604. 12. Herndon DN, Stein MD, Rutan TC, Abston S. Predictors of mortality in patients with inhalation injury. Proceedings of the American Burn Association, 17th Annual Meeting, Orlando, Florida, March 27-30, 1965. 13. Goodwin CW, Dorethy J, Lam V, Pruitt BA Jr. Randomized trial of efficacy of crystalloid and colloid resuscitation on hemodynamic response and lung water following thermal injury. Ann Surg 1983;197:520-31. 14. Pruitt BA Jr. Summary, fluid resuscitation. Proceedings of the Second Consensus Development Conference on Supportive Therapy in Burn Care 8 Trauma 198 1.
Diiussion John L. Hunt (Dallas, TX): Dr. Navar, you have presented an important topic that up to now has been believed to be true, but has been based only on anecdotal information. There is now hard data to confirm that patients with inhalation injuries require additional fluid. Dr. Navar, you arbitrarily chose to include burns covering more than 25 percent of the total body surface area for evaluation of inhalation injury. In our experience, more than a third of patients with inhalation injuries have burns covering less than 25 percent of the total body surface area. Do you have any information on fluid requirements in such patients? The patients with inhalation injury had a significantly greater component of third degree burns compared with those without an inhalation injury, which in itself could account for a major portion of the excess fluid that was administered to the patients in the inhalation group. Could you comment further on this? Your unit is unique in that many of your patients are transferred from regions outside of Salt Lake City, and consequently a delay in treatment or inadequate resuscitation is apparently common. We have the clinical impression that patients with delayed or inadequate resuscitation often require more fluid than would be anticipated by most formulas. Dr. Navar, could you also comment on whether there are any subgroups of patients with inhalation injuries who seemed to be more prone to pulmonary complications? Inhalation injuries in general are associated with a increased number of pulmonary complications, but are
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there certain patients, characterized by age or percentage of burns, in whom this is more common? Again, I would like to reemphasize what your group has stated, that patients probably have more harm done to them by underresuscitation than overresuscitation. No formula is ideal for all patients, and they must be monitored frequently. Paul D. Navar (closing): Dr. Hunt, we did not include patients with smoke inhalation who had burns over less than 25 percent of the total body surface area. A higher incidence of long-term pulmonary complications occurred in the patients with inhalation injury. There was no evidence from the study that this was due to increased amounts of intravenous fluid. As previously mentioned, those patients with inhalation injury who ultimately died did not require more fluid than the group as a whole. Several studies have shown that extravascular lung water is only rarely increased in patients with severe inhalation injury. It is well known that patients with an increased component of third degree burns require more fluid to achieve resuscitation than those patients with lesser third degree burn injury, as you pointed out, Dr. Hunt. In our series, there was a slight increase in fluid requirements with increasing burn size in patients without inhalation injuries. However, this did not exceed 4.4 ml/kg per percentage of total body surface area in the groups with greater than 40 percent of total body surface area burned, where one would expect a correspondingly increased component of third degree burn. This was in contrast to the fluid requirement of 5.5 to 6 ml/kg per percentage of total body, surface area seen in the group with inhalation injury with burns of less than 40 percent of total body surface area. We concluded that the increased component of third degree burns seen in the group with inhalation injury plays only a minor part in the significant increase in fluid requirements seen in these patients. Delay in the initiation of resuscitation is a feature of our burn unit in Salt Lake City because many of our patients are transported by air from outlying areas. We did see a delay in resuscitation in both groups, however, this did not predominate in one group or the other.
The American Journal of Surgery