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Hypothermia from realistic fluid resuscitation in a model of hemorrhagic shock.

STUDY OBJECTIVE: To correlate changes in core body temperature with changes in mean arterial pressure (MAP) and cardiac output (CO) and with the administration of room-temperature intravenous fluids in a clinically relevant large-animal model of uncontrolled hemorrhage. METHODS: Ten swine were subjected to uncontrolled hemorrhage through a flow-monitored shunt placed between the femoral artery and the peritoneal cavity. Animals were randomly assigned to a treatment or a control group. The control group (n=5) received no intravenous fluids. The treatment group (n=5) received 80 mL/kg (3:1 crystalloid/blood loss) ambient-temperature lactated Ringer's solution over a 10-minute resuscitation phase initiated 10 minutes after injury. CO and core body temperature, measured with the use of a pulmonary artery catheter, and MAP were the primary outcomes. We analyzed differences between groups with the use of repeated-measures ANOVA. Change of temperature was analyzed against the change in CO, and against fluid infusion for each interval, by means of regression analysis. RESULTS: The unresuscitated control animals had no change in core temperature despite profound hemorrhagic shock and hypotension. The animals treated with fluids had a mean 2.6 degrees C decrease in core temperature during fluid resuscitation (95% confidence interval [CI], 1.8 to 3.5). A 1.5 degrees C decrease in core temperature (95% CI, .1 to 2.0) persisted at the end of 60 minutes (40 minutes after fluid resuscitation was discontinued). Core temperatures in control animals were 2.8 degrees C lower than those in treated animals after fluid resuscitation (95% CI, .8 to 4.8). Decreases in core temperature correlated with fluid infusion (beta=-35.2 mL/kg x degrees C, R2=.75) and increases in CO (beta=-1.46 L/min x degrees C, R2=.69). CONCLUSION: Ambient-temperature crystalloid resuscitation in a clinically relevant large-animal model of hemorrhagic shock causes small decreases in core body temperature. Resuscitation rather than shock is the main cause of decreased body temperature in this model.

Analysis of Variance↗

Blood substitute resuscitation as a treatment modality for moderate hypovolemia.

Blood substitute resuscitation as a treatment modality for moderate hypovolemia (approximately 40% blood loss) in a canine model has been evaluated using Oxyglobin (Biopure Hemoglobin Glutamer-200/ Bovine; a hemoglobin-based oxygen-carrier) and Hespan (6% hetastarch; a nonoxygen-carrier) as resuscitants. Autologous (shed) blood served as control. Nine dogs were studied--after splenectomy, each dog was hemorrhaged (32-36 mL/kg; MAP = approximately 50 mmHg) and randomly assigned to the three resuscitation groups. Microvascular, systemic function and oxygenation characteristics were monitored and/or measured simultaneously in prehemorrhagic (baseline), posthemorrhagic and postresuscitation phases for correlation-real-time microvascular changes in the bulbar conjunctiva were noninvasively measured via computer-assisted intravital microscopy and systemic function and oxygenation changes were monitored and/or measured via instrumentation and devices incorporated into our bioengineering station in an operating room setting. Blood chemistry was also studied for relevant measurements. Prehemorrhagic microvascular characteristics were similar in all animals (venular diameter = 41 +/- 12 microm, A:V ratio = approximately 1:2, red-cell velocity = 0.5 +/- 0.3 mm/s). All animals also showed similar prehemorrhagic systemic function and oxygenation measurements comparable to a previous study and were consistent with normal measurements in dogs. At the completion of hemorrhaging to achieve moderate hypovolemia (approximately 40% blood loss with MAP at approximately 50 mmHg), all nine animals showed similar significant (P < 0.01) posthemorrhagic microvascular changes, including approximately 17% decrease in diameter (34 +/- 7 microm), A:V ratio = variable, and approximately 80% increase in velocity (0.9 +/- 0.5 mm/s). All animals also showed similar significant (P < 0.01) posthemorrhagic systemic function and oxygenation changes, with decreases in Hct, aHb(total), MPAP, MAP, SAP, DAP, CO, SVI, CaO2, and CvO2 and increases in HR and lactic acidosis. Shed blood (control) resuscitation restored posthemorrhagic microvascular changes close to prehemorrhagic values (diameter = 39 +/- 6 microm, A:V ratio = approximately 1:2, velocity = 0.6 +/- 0.4 mm/s). Oxyglobin and Hespan restored microvascular changes in similar manner close to prehemorrhagic values (Oxyglobin: diameter = 38 +/- 3 microm, A:V ratio = approximately 1:2, velocity = 0.6 +/- 0.4 mm/s; Hespan: diameter = 38 +/- 7 microm, A:V ratio = 1:2, velocity = 0.5 +/- 0.4 mm/s). After resuscitation, shed blood (control) restored all systemic function and oxygenation changes close to prehemorrhagic values. However, both Oxyglobin and Hespan resuscitation restored systemic function changes, but not oxygenation changes, to prehemorrhagic values. This was an interesting finding because of the different oxygen-carrying capability of Oxyglobin (oxygen-carrying) and Hespan (nonoxygen-carrying). The result suggests that either volume replenishment alone (and not oxygen-carrying capability) is needed to treat moderate hypovolemia or oxygenation measurements obtained by standard methods (oximetry, blood chemistry) may not reflect tissue oxygenation levels.

Animals↗

Suspended animation for delayed resuscitation.

'Suspended animation for delayed resuscitation' is a new concept for attempting resuscitation from cardiac arrest of patients who currently (totally or temporarily) cannot be resuscitated, such as traumatic exsanguination cardiac arrest. Suspended animation means preservation of the viability of brain and organism during cardiac arrest, until restoration of stable spontaneous circulation or prolonged artificial circulation is possible. Suspended animation for exsanguination cardiac arrest of trauma victims would have to be induced within the critical first 5 min after the start of cardiac arrest no-flow, to buy time for transport and resuscitative surgery (hemostasis) performed during no-flow. Cardiac arrest is then reversed with all-out resuscitation, usually requiring cardiopulmonary bypass. Suspended animation has been explored and documented as effective in dogs in terms of long-term survival without brain damage after very prolonged cardiac arrest. In the 1990s, the Pittsburgh group achieved survival without brain damage in dogs after cardiac arrest of up to 90 min no-flow at brain (tympanic) temperature of 10 degrees C, with functionally and histologically normal brains. These studies used emergency cardiopulmonary bypass with heat exchanger or a single hypothermic saline flush into the aorta, which proved superior to pharmacologic strategies. For the large number of normovolemic sudden cardiac death victims, which currently cannot be resuscitated, more research in large animals is needed.

Journal Article↗

Crystalloids vs. colloids in fluid resuscitation: a systematic review.

OBJECTIVE: To systematically review the effects of isotonic crystalloids compared with colloids in fluid resuscitation. DATA SOURCES: Computerized bibliographic search of published research and citation review of relevant articles. STUDY SELECTION: All randomized clinical trials of adult patients requiring fluid resuscitation comparing isotonic crystalloids vs. colloids were included. Pulmonary edema, mortality, and length of stay were evaluated. Independent review of 105 articles identified 17 relevant primary studies of 814 patients. Weighted c about article inclusion was high (0.76). DATA EXTRACTION: Data on population, interventions, outcomes, and methodologic quality of the studies were obtained by duplicate independent review with differences resolved by consensus. Weighted ic on the validity assessment was moderate (0.54). DATA SYNTHESIS: No difference was observed overall between crystalloid and colloid resuscitation with respect to mortality and pulmonary edema; however, the power of the aggregated data was insufficient to detect small but potentially clinically important differences. Subgroup analysis suggested a statistically significant difference in mortality in trauma in favor of crystalloid resuscitation (relative risk 0.39, 95% confidence intervals: 0.17 to 0.89). Several methodologic issues are noteworthy regarding the primary studies, including lack of blinding (except in three studies). The type, dose, and duration of fluid administration and outcomes measured were different across these trials. CONCLUSIONS: Overall, there is no apparent difference in pulmonary edema, mortality, or length of stay between isotonic crystalloid and colloid resuscitation. Crystalloid resuscitation is associated with a lower mortality in trauma patients. Methodologic limitations preclude any evidence-based clinical recommendations. Larger well-designed randomized trials are needed to achieve sufficient power to detect potentially small differences in treatment effects if they truly exist.

Colloids↗

Fluid resuscitation and hyperchloremic acidosis in experimental sepsis: improved short-term survival and acid-base balance with Hextend compared with saline.

OBJECTIVE: To compare resuscitation with 0.9% saline with Hextend, a synthetic colloid in a balanced electrolyte solution, in terms of acid-base status and survival time in an experimental model of septic shock in the rat. DESIGN: Randomized, open-label, controlled experiment. SETTING: University research laboratory. SUBJECTS: Sixty adult, male Sprague-Dawley rats. INTERVENTION: Animals were studied for 12 hrs after intravenous infusion of Escherichia coli endotoxin (20 mg/kg). Animals were volume resuscitated to maintain a mean arterial pressure >60 mm Hg using either 0.9% saline (n = 25), Hextend (n = 25), or lactated Ringer's (n = 10). MEASUREMENTS: Arterial blood gases and electrolytes were measured before and after resuscitation (0, 180, 360, and 540 mins after endotoxin infusion). Survival time was measured, up to 12 hrs. RESULTS: Mean survival time among animals treated with saline or Ringer's was 45% less compared with Hextend-treated animals: 391 +/- 151 mins and 362 +/- 94 mins vs. 567 +/- 140 mins, respectively, p <.0001. Overall survival (at 12 hrs) was 0% with saline or Ringer's vs. 20% with Hextend, p =.05. After resuscitation with saline, arterial standard base excess and plasma apparent strong ion difference were both significantly lower (-19.3 +/- 5.2 vs. -12.1 +/- 5.7, p <.001, and 23.0 +/- 6.2 vs. 30.3 +/- 2.9, p <.0001, respectively) and plasma Cl(-) was significantly higher (123 +/- 7 vs. 115 +/- 3 mmol/L, p <.0001) compared with Hextend. Resuscitation with Ringer's solution resulted in a standard base excess, and Cl(-) between that of saline and Hextend (-15.4 +/- 3.1, and 117 +/- 3, respectively). CONCLUSION: Compared with 0.9% saline, volume resuscitation with Hextend was associated with less metabolic acidosis and longer survival in this experimental animal model of septic shock.

Acid-Base Equilibrium↗

Serum lactate and base deficit suggest inadequate resuscitation of patients with burn injuries: application of a point-of-care laboratory instrument.

Urinary output of 30 to 50 ml/hr and mean arterial pressure of more than 70 mm Hg continue to be the yardsticks by which patients with burn injuries are resuscitated. We designed this prospective, descriptive study to compare these parameters with serial base deficit and serum lactate values, which have been found to be sensitive indicators of adequate fluid resuscitation in trauma patients. The sample group consisted of 53 patients, consecutively admitted to the burn intensive care unit, who had 15% or more total body surface area burns. No changes in resuscitation protocol were implemented. Within the 48-hour period after admission, 2 ml heparinized venous blood samples were collected and analyzed every 2 to 4 hours, and vital signs, urinary output, fluid type, and volume administered were documented each hour. Urinary output and mean arterial pressure were maintained at more than 30 ml/hr and more than 70 mm Hg, respectively. Partial correlations between the traditional resuscitation variables and serum lactate and base deficit were low. On average, serum lactate and base deficit remained abnormally high during the study period. These new parameters may be used to improve the fidelity with which burn shock resuscitation is undertaken. Further studies of these parameters and how they may be used as endpoints in fluid resuscitation are needed.

Acidosis↗

How well does the Parkland formula estimate actual fluid resuscitation volumes?

We had anecdotally observed that fluid resuscitation volumes often exceed those estimated by the Parkland Formula in adults with isolated cutaneous burns. The purpose of this study was to compare estimated and actual fluid resuscitation volumes using the Parkland Formula. We performed a retrospective study of fluid resuscitation in patients with burns > or = 15% TBSA. Patients with inhalation injury, high voltage electrical injury, delayed resuscitation, or associated trauma were excluded. We studied 31 patients (mean age 51 +/- 20 years, mean TBSA burn 27 +/- 10%). The 24 hour resuscitation volume of 13 354 +/- 7386 ml (6.7 +/- 2.8 ml/kg/%TBSA) was significantly greater than predicted (P = 0.001) and exceeded estimated volume in 84% of the patients. The mean urine output in the first 24 hrs was 1.2 +/- 0.6 ml/kg/hr. After the first 8 hours of resuscitation, the infusion rate decreased by 34% in 16 patients (DCR group), while in 15 patients the rate increased by 47% (INCR group). Both the DCR and INCR groups received significantly more fluid than predicted, (5.6 +/- 2.1 ml/kg/%TBSA and 7.7 +/- 3.1 ml/kg/%TBSA respectively). The INCR patients had significantly larger full thickness burns (14 +/- 11% vs 3 +/- 6%, P < 0.001). Our findings reveal that despite its effectiveness, the Parkland Formula underestimated the volume requirements in most adults with isolated cutaneous burns, and especially in those with large full thickness burns.

Adult↗

The effect of hypertonic resuscitation on pial arteriolar tone after brain injury and shock.

Acute brain injury followed by hemorrhagic shock (HEM) causes prohibitive mortality in trauma patients because these combined events lead to low cerebral blood flow (CBF) and cerebral oxygen delivery (co2del). Proper treatment therefore requires rapid correction of cerebral perfusion deficits. Previous studies have shown that hypertonic crystalloid resuscitation significantly improves CBF and co2del in a model of brain injury and HEM when compared to lactated Ringer's (LR) solution. The mechanism or mechanisms for this advantage, however, are not well understood. We hypothesized that hypertonic fluid resuscitation would reduce pial arteriolar tone after brain injury and HEM resulting in an increase in CBF when compared to LR resuscitation. We measured cerebral and systemic variables in a porcine model of focal cryogenic brain injury and hemorrhagic shock over a 5-hour period. Swine were randomized to receive either hypertonic sodium lactate (HSL) or LR fluid resuscitation. The HSL resuscitation produced a significant and sustained elevation in cerebral perfusion pressure and pial arteriole diameter (p < 0.05), and a sustained elevation in CBF after brain injury and HEM when compared with LR. These data suggest that hypertonic fluid resuscitation following brain injury and HEM improves CBF, at least in part, by causing vasodilation of cerebral resistance vessels.

Animals↗

Resuscitation from hemorrhagic shock with diaspirin cross-linked hemoglobin, blood, or hetastarch.

BACKGROUND: An oxygen-transporting hemoglobin solution should be more effective than a nonhemoglobin solution for resuscitation from hemorrhagic shock. A way to evaluate this effectiveness is to determine whether a hemoglobin solution can reverse the base deficit accumulated during hemorrhage at a faster rate than a nonhemoglobin solution. Using this criterion, we compared the resuscitative powers of autologous blood, hetastarch (Het), and diaspirin cross-linked hemoglobin (DCLHb). METHODS: Fifteen sedated, spontaneously breathing sheep (37.5 +/- 10.2 kg) were bled until base deficits fell to -5 to -10 mEq/L, and plasma lactate concentrations rose to 6 to 9 mg/L. The animals were resuscitated with autologous blood (n = 5), Het (n = 5), or DCLHb (n = 5) (3.5-4.0 mL/kg every 15 minutes) until base deficits returned to prehemorrhage baseline. RESULTS: Exsanguination to target base deficits required removal of an average of 41.4 +/- 5.5 mL blood/kg (estimated total blood volume, 80 mL/kg). Resuscitation required 18 +/- 3, 38 +/- 2 (different from blood), and 35 +/- 1 (different from blood) mL/kg of autologous blood, Het and DCLHb, respectively, over periods of 78 +/- 8, 163 +/- 10 (different from blood), and 129 +/- 9 minutes (different from blood and different from Het (p < or = 0.05)). Based on regression analysis, autologous blood, Het, and DCLHb corrected the base deficit at rates of, respectively, 0.074 (different from Het (p < or = 0.05)), 0.016, and 0.056 (different from Het (P < or = 0.05)) mEq/L/min. CONCLUSIONS: Based on the rate of base deficit correction and the volume of solution required, autologous blood was the most effective resuscitation solution. However, DCLHb was more effective than Het. DCLHb may be an attractive alternative to blood for resuscitation from hemorrhagic shock.

Animals↗

Fluid resuscitation and blood replacement in patients with polytrauma.

Hemorrhage is the most common cause of shock in patients with polytrauma, leading to cellular hypoxia and death. A large body of experimental and clinical research has greatly expanded our knowledge of cellular mechanisms and clinical outcomes in resuscitation of patients with hypovolemic shock. However, the fundamental principles of fluid resuscitation have not changed during the past few decades. Aggressive resuscitation to correct tissue hypoperfusion within 24 hours of injury is associated with improved clinical outcomes. Initial volume expanders of choice are crystalloid solutions, with blood and blood products used for patients who are hemodynamically unstable, patients with Class III and Class IV hemorrhage, and patients with ongoing uncontrolled sources of bleeding. The incidence of immunologic and infectious complications associated with blood transfusions in resuscitation of patients with polytrauma has not been shown to be any higher than in other clinical settings. Massive resuscitations, however, are associated with specific complications such as hypothermia, coagulopathy, and abdominal compartment syndrome. Novel blood substitutes, hypertonic saline, and minimally invasive hemodynamic monitoring techniques have the potential of optimizing fluid resuscitation in patients with polytrauma. Additional research using standardized animal models and randomized clinical trials is needed.

Blood Substitutes↗

Hypertonic saline and pentoxifylline reduces hemorrhagic shock resuscitation-induced pulmonary inflammation through attenuation of neutrophil degranulation and proinflammatory mediator synthesis.

BACKGROUND: Ringer's lactate (RL), the current standard resuscitation fluid, potentiates neutrophil activation and is associated with pulmonary inflammation. Resuscitation with hypertonic saline and pentoxifylline (HSPTX) has been shown to attenuate hemorrhagic shock-induced injury when compared with RL. Because the neutrophil plays a major role in postshock inflammation, we hypothesized that HSPTX reduces pulmonary inflammation after resuscitation in comparison to RL. METHODS: Sprague-Dawley rats underwent controlled shock and were resuscitated with RL (32 mL/kg) or HSPTX (4 mL/kg 7.5% NaCl + pentoxifylline 25 mg/kg). Animals who did not undergo shock or resuscitation served as controls. After 24 hours, bronchoalveolar lavage fluid (BALF) and lung tissue were collected. Cytokine induced neutrophil chemoattractant (CINC) was measured in BALF by enzyme-linked immunosorbent assay. Matrix metalloproteinases (MMP)-2 and -9 were measured by zymography. Hemeoxygenase-1 (HO-1) was assessed by Western blot and immunohistochemistry. RESULTS: HSPTX resuscitation led to a 62% decrease in CINC levels compared with RL (p < 0.01). BALF MMP-2 expression was attenuated by 11% with HSPTX (p = 0.09). Lung MMP-2 and MMP-9 expression was reduced by 89% (p < 0.01) and 76%, respectively (p < 0.05). Lung HO-1 expression declined by 34% with HSPTX in comparison to RL (p < 0.01), indicating less oxidative injury. Lung immunohistochemistry localized HO-1 to neutrophils, macrophages, and airway epithelial cells. CONCLUSION: Collectively, the attenuation of pulmonary inflammation with HSPTX after shock when compared with RL is associated with downregulation of neutrophil activation, oxidative stress, and proinflammatory mediator production.

Animals↗

Fluid resuscitation in major burns.

BACKGROUND: The Parkland formula is established as the "gold standard" for initial fluid resuscitation for major burns. The purpose of this study was to review our fluid resuscitation practice for major burns to determine whether anecdotal observations of significant variations from the Parkland formula were wide spread and whether any difference could be used as a basis for a revision of fluid resuscitation in major burns. METHODS: A retrospective review of 127 presentations to The Alfred Burns Unit with total body surface area (TBSA) affected > or =15% was conducted. A retrospective review of the resuscitation data from these patients was compared with the Parkland formula as well as other studies. RESULTS: A total of 49 patients with complete data on fluid administration and uncomplicated burns were included in the analysis. Significantly larger volumes of fluid (5.58 mL/kg per %TBSA) were given to these patients in the first 24 h than predicted by the Parkland formula. Mean arterial pressure, pulse rate and urine output were at satisfactory levels. Clinically evident complications from fluid administration were minimal. Mortality was similar to that in other centres. CONCLUSION: Fluid resuscitation volumes significantly higher than those predicted by the Parkland formula were given, without adverse consequences. This retrospective review supports a prospective, multicentre, randomized, controlled study comparing this study with the Parkland formula, resulting in a better guide to initial fluid resuscitation in major burns.

Adult↗

Effects of isovolemic resuscitation with hemoglobin-based oxygen carrier Hemoglobin glutamer-200 (bovine) on systemic and mesenteric perfusion and oxygenation in a canine model of hemorrhagic shock: a comparison with 6% hetastarch solution and shed blood.

OBJECTIVE: To study Hemoglobin glutamer-200 bovine (Hb-200), 6% hetastarch (HES) and shed whole blood (WB) resuscitation in canine hemorrhagic shock. STUDY DESIGN: Prospective laboratory investigation. Animals Twelve adult dogs [29 +/- 1 kg (mean +/- SD)]. METHODS: Anesthetized dogs were instrumented for recording systemic and mesenteric hemodynamic parameters and withdrawal of arterial, mixed and mesenteric venous blood, in which hematological, oxygenation, blood gas and acid-bases variables were determined. Recordings were made before [baseline (BL)], after 1 hour of hypovolemia and immediately and 3 hours post-resuscitation with 30 mL kg(-1) of either Hb-200, HES, or WB. RESULTS: Blood withdrawal (average 34 +/- 2 mL kg(-1)) caused significant hemodynamic changes, metabolic acidosis and hyperlactatemia characteristic for hemorrhagic shock. Only WB transfusion restored all variables. Hemoglobin glutamer-200 bovine infusion returned most hemodynamic parameters including cardiac output and mesenteric arterial blood flow to BL but increased mean arterial pressure above BL (p < 0.05). However, Hb-200 failed to restore total Hb and arterial oxygen content (CaO2), leaving systemic (DO2I) and mesenteric O2 delivery (DO2Im) below BL (p < 0.05). Nevertheless, acid-base variables recovered completely after Hb-200 resuscitation, and met-hemoglobin (Met-Hb) levels increased (p < 0.05). Hetastarch resuscitation returned hemodynamic variables to or above BL but further decreased total Hb and CaO2, preventing recovery of sDO2I and mDO2I (p < 0.05). Thus, systemic and mesenteric O2 extraction stayed above BL (p < 0.05) while acid-base variables recovered to BL, although slower than in Hb-200 and WB groups (p < 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Resuscitation with Hb-200 seemed to resolve metabolic acidosis and lactatemia more rapidly than HES, but not WB; yet it is not superior to HES in improving DO2I and DO2Im. The hyperoncotic property of solutions like Hb-200 that results in rapid volume expansion with more homogenous microvascular perfusion and the ability to facilitate diffusive O2 transfer accelerating metabolic recovery may be the key mechanisms underlying their beneficial effects as resuscitants.

Animals↗

Resuscitation of acid-injured Salmonella in enrichment broth, in apple juice and on the surfaces of fresh-cut cucumber and apple.

AIMS: To investigate the resuscitation of acid-injured Salmonella enterica in selected enrichment broths, in apple juice and on cut surfaces of apple and cucumber slices. METHODS AND RESULTS: Following exposure to 2.4% acetic acid for 7 min, S. enterica (serovars Mbandaka, Chester and Newport) cells were used to inoculate enrichment broths, phosphate-buffered saline (PBS), apple juice and fruit slices. Injured Salmonella cells resuscitated and regained the ability to form colonies on selective agar (Xylose-Lysine-Tergitol 4) if they were incubated in lactose broth (LB), universal pre-enrichment broth (UPB) or buffered peptone water (BPW), but not in tetrathionate broth, PBS or apple juice. The resuscitation occurred at a significantly (P > 0.05) faster rate in UPB than in LB or BPW. The resuscitation also occurred on the surfaces of fresh-cut cucumber at 20 degrees C, but not at 4 degrees C. CONCLUSIONS: Acid-injured Salmonella cells resuscitated in nonselective enrichment broths at different rates, but not in selective enrichment broth, apple juice, PBS or on fresh-cut apple. SIGNIFICANCE AND IMPACT OF THE STUDY: Pre-enrichment of food samples in UPB prior to selective enrichment is recommended. Injured Salmonella cells have the ability to resuscitate on fresh-cut surfaces of cucumber when stored at abusive temperatures.

Acids↗

PEG-Hemoglobin as a resuscitation solution in the treatment of hypovolemic shock in the anesthetized rat.

This study was designed to determine the advantages of using the hemoglobin-based oxygen carrier, polyethylene glycol conjugated bovine hemoglobin (PEG-Hb), as an additive to Ringer's lactate solution (RLS) for the treatment of acute hemorrhage in anesthetized female rats. Different compositions of PEG-Hb and RLS were administered intravenously in a paradigm that provided 30 ml/kg of resuscitation fluid following an episode of 15 min of hypotension. Hypotension was achieved by the removal of blood (1 ml/min) from the femoral vein until the mean arterial pressure was lowered to or below 50 mmHg and subsequently maintained until resuscitation. Short-term cardiovascular assessment showed that resuscitation fluids containing PEG-Hb resulted in higher mean arterial pressure, aortic blood flow, renal blood flow, and less dramatic shifts in arterial base excess and respiratory blood gases than plain RLS. The long-term survival experiment showed lower lactate dehydrogenase, alkaline phosphatase, and serum glutamic pyruvic transaminase levels in most groups resuscitated with solutions containing PEG-Hb, but no differences in survival (100%) were observed. The data suggest that the addition of PEG-Hb to RLS improves its resuscitative effects. Specifically, a solution of 50% RLS:50% PEG-Hb appeared to have the most favorable cardiovascular and metabolic effects in this anesthetized rat hypovolemic shock resuscitation model. Presumably, the improved effects seen with the addition of PEG-Hb were due to its innate plasma expansion and oxygen-delivery capabilities.

Analysis of Variance↗

Resuscitation of Vibrio vulnificus from the Viable but Nonculturable State.

Like many other gram-negative bacteria, the human pathogen Vibrio vulnificus is induced into a viable but nonculturable (VBNC) state by incubation at low temperatures. The ability of any bacterium to resuscitate from this dormant state would appear to be essential if the VBNC state is truly a survival strategy. The question as to whether the culturable cells which appear following removal of the inducing stress are a result of true resuscitation or of regrowth of a few residual culturable cells has long been debated. V. vulnificus was examined for its ability to resuscitate from this state following a temperature upshift. Several lines of investigation, including dilution studies, determination of the time necessary for appearance of a culturable population, and the effects of nutrient on recovery, all indicated that, at least for V. vulnificus, true resuscitation does occur. Our studies further suggest that nutrient is in some way inhibitory to the resuscitation of cells in the VBNC state and that studies which add nutrient in an attempt to detect resuscitation are able to detect only residual culturable cells which might be present and which were not inhibited by the added nutrient.

Journal Article↗

Changes in resuscitation practice at birth.

AIM: To investigate secular changes in neonatal resuscitation at birth. METHODS: Single centre observational study of 17 890 infants born between May 1993 and April 1997. T-piece ventilation was introduced in April 1995. OBSERVATIONS: Rates and modes of ventilatory resuscitation, early neonatal encephalopathy, neonatal convulsions, and meconium aspiration syndrome; 1 and 5 min Apgar scores; maternal age and method of delivery; paediatric attendance at delivery and resuscitation. RESULTS: The rate of all forms of ventilatory resuscitation fell during the four year period from 11.0% to 8.9%. The rate of intubation fell from 2.4% to 1.2%. A reduced rate of intubation was seen at all gestations of 30 weeks and above. There was no difference in rates of relevant neonatal problems during the period except for a reduction in neonatal convulsions. The introduction of T-piece ventilation did not contribute to the reduction in intubation in a logistic regression model that included time trend. CONCLUSION: A marked reduction in the rate of intubation was observed, without any reduction in the efficacy of resuscitation. This may reflect improvements and changing emphasis in resuscitation training.

Adult↗

Resuscitation affects microcirculatory polymorphonuclear leukocyte behavior after hemorrhagic shock: role of hypertonic saline and pentoxifylline.

We have previously shown that lung injury following fluid resuscitation either with hypertonic saline (HS) or lactated Ringer's (LR) plus pentoxifylline (PTX) attenuated acute lung injury when compared with LR resuscitation. The objective of the present study is to determine whether our previous observations are accompanied by changes in polymorphonu-clear leukocyte (PMN) behavior. To study this, PMN-endothelial cell interactions, microcirculatory blood flow, lung histology, lung PMN infiltration (MPO, Myeloperoxidase), and lung intra-cellular adhesion molecule-1 (ICAM-1) expression were assessed in a controlled hemorrhagic shock model followed by LR, HS, and LR+PTX resuscitation in rodents. Rats (240-300 g) were bled to a mean arterial pressure (MAP) of 35 mm Hg for 1 hr and then randomized into three groups: HS (7.5% NaCl, 4 ml/kg); LR (3x shed blood); and LR+PTX (25 mg/kg). Additionally, total shed blood was reinfused. A sham group underwent no shock and no treatment. The internal spermatic fascia was exteriorized and the microcirculation was observed by closed-circuit TV coupled to a microscope, 2 and 6 hrs after treatment. The number of leukocytes sticking to the venular endothelium was determined 2 hrs after fluid resuscitation. Microcirculatory blood flow was measured by an optical Doppler velocimeter. Lung histology and lung MPO immunostaining were assessed at 6 hrs, and lung ICAM-1 expression was determined by immunostaining at 2 hrs following fluid resuscitation. Two hours after treatment, HS (1.4 +/- 0.4), LR+PTX (1.7 +/- 0.3), and sham (0.4 +/- 0.2) groups presented significant reductions in leukocyte adherence (cells/100 microm venule length), compared with the LR group (4.0 +/- 0.9, P < 0.05). No differences were observed 6 hrs after treatment on leukocyte adherence and microcirculatory blood flow. ICAM-1 expression was significantly higher in LR-treated animals compared with the HS, LR+PTX, and sham groups (P < 0.01). PMN infiltration and overall lung injury were significantly attenuated by HS and LR+PTX. These results support earlier studies that indicated the potential application of HS and PTX in shock therapy and the increase in PMN-endothelial cell interaction and lung injury after LR resuscitation.

Animals↗