Trends in blood conservation in burn care.

Traditional burn surgery is very bloody, but wide use of blood conserving strategies is becoming common. Uniform application of blood conserving techniques of burn wound excision may substantially decrease blood utilization in burn patients. We chose to examine this trend in our unit. All fresh frozen plasma (FFP) and packed red blood cell (pRBC) use in children with burns of 10% or more of the body surface who were admitted during 2-3 year intervals, separated by a decade, was reviewed in detail. Three subgroups were separately analyzed: children with 10-24% (small), 25-49% (medium) and 50-100% (large) body surface area burns. Between these two intervals a major emphasis was made in techniques of blood conservation during surgery and fresh frozen plasma was replaced by 5% albumin as the routine resuscitative colloid. In Group 1, there were 189 children, of whom 184 (97%) survived to discharge. In Group 2, there were 203 children, of whom 199 (98%) survived to discharge (N.S.). All subgroups were well matched for age, weight and burn size. Discharge hemocrits exceeded 30% in all subgroups. Reductions in FFP use were 100, 95 and 97% in the small, medium and large burn size groups, respectively. Reductions in pRBC use were 89, 63, and 80% in the small, medium and large burn size groups, respectively. These differences were all highly significant (P<0.001). Uniform application of blood conserving techniques of burn wound excision result in highly significant reductions in blood product exposure without sacrifice of clinical outcomes.

Neuromuscular effects of mivacurium in 2- to 12-yr-old children with burn injury.

BACKGROUND: Burned patients are usually resistant to the neuromuscular effects of nondepolarizing relaxants, mostly because of receptor changes. The magnitude of the resistance is related to burn size and time after burn. Mivacurium is a muscle relaxant, degraded by plasma cholinesterase, whose enzyme activity is decreased in burns. The present study tested the hypothesis that burn-induced depressed plasma cholinesterase activity counteracts the receptor-mediated resistance, resulting in a lack of resistance to mivacurium. METHODS: Burned patients (n = 23), aged 2-12 yr, subclassified into burns of 10-30% or > 30% of body surface, were studied at < or = 6 days and again at 1-12 weeks after burn if possible. Thirteen additional patients served as controls. Neuromuscular variables monitored included onset and recovery following bolus dose, continuous infusion rates required to maintain 95 +/- 4% paralysis, and recovery rates following infusion. RESULTS: The onset times of maximal twitch suppression were not different between burns and controls, but recovery to 25% of baseline twitch height was prolonged in patients with > 30% burn irrespective of time after injury. The continuous infusion rates to maintain twitch suppression at 95 +/- 4% were not different between groups. The recovery indices, including train-of-four to > 75%, 25-75%, or 5-95% in burned patients, were similar or prolonged compared with controls. The prolonged recovery in burned patients was inversely related to plasma cholinesterase activity (R2 = 0.86, r = -0.93, P < 0.001), and the decreased plasma cholinesterase activity was related to burn size and time after burn. CONCLUSIONS: A normal mivacurium dosage (0.2 mg/kg) effects good relaxation conditions in burned patients, with an onset time similar to that in controls. This finding contrasts with the response seen with other nondepolarizing drugs, higher doses of which are required to effect paralysis. The decreased metabolism of mivacurium, resulting from depressed plasma cholinesterase activity, probably counteracts the receptor-mediated potential for resistance. Because succinylcholine is contraindicated in burned patients, larger doses of nondepolarizing agents are advocated to effect rapid onset of paralysis. This generalization does not hold for mivacurium. diatrics; plasma cholinesterase; relaxant resistance; succinylcholine, alternative to.)

Staged high-dose epinephrine clysis is safe and effective in extensive tangential burn excisions in children.

Prodigious blood loss commonly accompanies extensive tangential burn excisions. Staged high-dose epinephrine clysis may facilitate blood conserving excisional burn surgery. Prospective data was collected in 25 consecutive children who underwent tangential excision over the torso of at least 10% of the body surface with staged high dose epinephrine clysis. The children had an average age of 6.3 +/- 1.1 years and burn size of 45.7 +/- 3.9%. Total operative wound size (excision plus donor site) averaged 2 +/- 0.8% of the body surface. Total dose of epinephrine averaged 24.6 +/- 2.8 mcg/kg. Based on pre- and postoperative hematocrit and known volume of transfusion, the percent of the total blood volume lost per percent total wound generated averaged 0.98 +/- 0.19% of the blood volume per % of the body surface; 18 of the children (72%) required no blood in the perioperative period. There were no complications related to epinephrine use, graft take averaged 98 +/- 0.6% and all children survived and have been discharged home in good condition. Due to its rapid metabolism, subcutaneous epinephrine at high doses can be repetitively administered as long as time is allowed for its metabolism to occur. Use of this technique facilitates a marked reduction in blood requirements for these traditionally bloody operations.

Dose effects of morphine and butorphanol alone and in combination after burn injury in the rat.

To test the effectiveness of analgesics after thermal trauma, butorphanol, a predominately opioid kappa-receptor agonist, and morphine, a mu-agonist, were administered alone and in combination 2 days after rats were subjected to scald burn or sham burn. After graded doses of morphine were administered, analgesia, assessed by tail flick latency and tail pinch latency, was similar in the sham-burn and scald-burn rats. With butorphanol alone analgesic effects were greater in the scald-burn than the sham-burn rats. When graded doses of butorphanol were given with a fixed dose of morphine (0.5 mg/kg), the tail pinch latency response was less in scald-burn rats and markedly less in sham-burn rats. The tail flick latency responses, however, moved in opposite directions in sham-burn and scald-burn rats receiving the drug combination: in sham-burn rats, tail flick latency effects were the same as with butorphanol alone; whereas in scald-burn rats, tail flick latency increases were suppressed except at the lowest dose.

Intraoperative reflectance oximetry in burn patients.

OBJECTIVE: Transmission oximetry sites for intraoperative monitoring are frequently difficult to find in burn patients, as standard transmission oximetry sites are often burned or contained within the operative field. The objective of this study was to determine if reflectance oximetry is of potential value in monitoring this group of patients. METHODS: A total of 16 operative procedures in a group of acutely burned adult and pediatric patients with an average age of 9.7 years (range, 10 months to 37 years), average burn size of 42% of the body surface (range, 15% to 94%), and average weight of 34.2 kg (range, 9 to 100 kg) were done with simultaneous transmission and reflectance oximetry monitoring. RESULTS: During these 16 procedures in a diverse group of acutely burned adult and pediatric patients, there was no significant difference in saturations derived from transmission and reflectance oximetry probes. In smaller children, adequate signal for reflectance probe monitoring was often detected in hyperemic sites, such as healed partial thickness burn. CONCLUSIONS: This is the first published report documenting both the clinical use of the reflectance oximetry in burn patients and the clinical use of the Nellcor Oxisensor II RS-10 reflectance oximetry probe (Nellcor Corporation, Hayward, CA). This technique can facilitate the intraoperative monitoring of acutely burned adult and pediatric patients in whom standard transmission oximetry sites are difficult to find.

Morphine-3-glucuronide: silent regulator of morphine actions.

To assess whether stoichiometric manipulation of morphine (M) metabolism can enhance analgesia or slow the development of M tolerance we co-administered M-3- glucuronide (M3G) during single or repeated doses of morphine in rats. Although M3G itself lacked analgesic activity, co-injection of M3G with M increased and prolonged analgesia beyond that seen with M. In addition, diminution of the acute analgesic effect of M after 3 once-daily doses of M did not occur after daily co-injection of M3G and M. Thus the traditional view that tolerance to the effects of M is due solely to effects mediated through opioid receptors must be broadened to include the contributions of enzyme induction or stoichiometric equilibration of M3G in this process.

Non-deterministic individual responses to receptor-selective opioid agonists.

To assess within a single rat strain individual variability of analgesic responses to sub-ED50 doses of receptor-selective opioids, we measured: 1) tail flick latency (TFL) responses after intrathecal (ith) injection of delta, mu, and kappa agonists administered serially; 2) TFL and tail pinch latencies (TPch) after intravenous (iv) mu and kappa agonists; and 3) TFL and TPch after iv agonists of mu or combined mu + delta selectivity. Mean values in each study confirmed an analgesic response, but individual TFL and TPch responses were chaotic and, within each study, rank order correlations between TFL and TPch values within or between drugs were insignificant. Our results suggest a hypothesis that such responses are intrinsically nondeterministic because--resembling other complex dynamic systems--they are generated by stochastic receptor-transmitter interactions that in turn evoke a series of nonlinearly coupled cellular and neural events.

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

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

Spinal co-administration of peptide substance P antagonist increases antinociceptive effect of the opioid peptide biphalin.

Intrathecal injection of 0.25 micrograms of undecapeptide substance P antagonist (SPA) produced transient antinociception with a peak effect at 5 min. Increasing the SPA dose resulted in neurotoxicity. Intrathecal injection of the opioid peptide biphalin (BIP) produced antinociception for over 3 hrs without neurotoxicity. Co-administration of SPA (at subtoxic doses) increased BIP's antinociceptive effect. Naltrexone reversed analgesia due to BIP alone as well as after BIP+SPA.

Local increases of subcutaneous beta-endorphin immunoactivity at the site of thermal injury.

To examine interactions between exogenous opioid analgesia and endogenous opioid generation at a site of burn-induced tissue injury, we measured beta-endorphin (BE) and corticosterone (C) in aliquots of plasma and wound fluid withdrawn from subcutaneous wire mesh chambers beneath the site of a 3-5% surface area burn. After brief inhalational anesthesia at the time of thermal injury, rats received morphine (4 mg/kg, single dose), fentanyl (0.02 mg/kg hourly for 4 h), or no opioid. Systemic hormone responses and behavioral changes were minimal as expected for the minimal percentage burn. In all three groups intrachamber BE and C rose above baseline at 1, 2 and 4 h postburn, then returned to baseline at 24 h. Systemic opioid treatment produced analgesia (by tail flick latency testing) but did not reduce intrachamber hormone responses. Thus local BE and C responses at the site of thermal injury are regulated differently from systemic pituitary-adrenal responses.