Human albumin solution for resuscitation and volume expansion in critically ill patients

BACKGROUND

Human albumin solutions are used for a range of medical and surgical problems. Licensed indications are the emergency treatment of shock and other conditions where restoration of blood volume is urgent, such as in burns and hypoproteinaemia. Human albumin solutions are more expensive than other colloids and crystalloids.

OBJECTIVES

To quantify the effect on mortality of human albumin and plasma protein fraction (PPF) administration in the management of critically ill patients.

SEARCH METHODS

We searched the Cochrane Injuries Group Specialised Register (searched 31 May 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2), MEDLINE (Ovid) (1948 to week 3 May 2011), EMBASE (Ovid) (1980 to Week 21 2011), CINAHL (EBSCO) (1982 to May 2011), ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED) (1970 to May 2011), ISI Web of Science: Conference Proceedings Citation Index - Science (CPCI-S) (1990 to May 2011), PubMed (www.ncbi.nlm.nih.gov/sites/entrez/) (searched 10 June 2011, limit: last 60 days). Reference lists of trials and review articles were checked, and authors of identified trials were contacted.

SELECTION CRITERIA

Randomised controlled trials comparing albumin or PPF with no albumin or PPF or with a crystalloid solution in critically ill patients with hypovolaemia, burns or hypoalbuminaemia.

DATA COLLECTION AND ANALYSIS

We collected data on the participants, albumin solution used, mortality at the end of follow up, and quality of allocation concealment. Analysis was stratified according to patient type.

MAIN RESULTS

We found 38 trials meeting the inclusion criteria and reporting death as an outcome. There were 1,958 deaths among 10,842 trial participants.For hypovolaemia, the relative risk of death following albumin administration was 1.02 (95% confidence interval (CI) 0.92 to 1.13). This estimate was heavily influenced by the results of the SAFE trial, which contributed 75.2% of the information (based on the weights in the meta-analysis). For burns, the relative risk was 2.93 (95% CI 1.28 to 6.72) and for hypoalbuminaemia the relative risk was 1.26 (95% CI 0.84 to 1.88). There was no substantial heterogeneity between the trials in the various categories (Chi(2) = 26.66, df = 31, P = 0.69). The pooled relative risk of death with albumin administration was 1.05 (95% CI 0.95 to 1.16).

AUTHORS' CONCLUSIONS

For patients with hypovolaemia, there is no evidence that albumin reduces mortality when compared with cheaper alternatives such as saline. There is no evidence that albumin reduces mortality in critically ill patients with burns and hypoalbuminaemia. The possibility that there may be highly selected populations of critically ill patients in which albumin may be indicated remains open to question. However, in view of the absence of evidence of a mortality benefit from albumin and the increased cost of albumin compared to alternatives such as saline, it would seem reasonable that albumin should only be used within the context of well concealed and adequately powered randomised controlled trials.

Human albumin solution for resuscitation and volume expansion in critically ill patients

BACKGROUND

Human albumin solutions are used for a range of medical and surgical problems. Licensed indications are the emergency treatment of shock and other conditions where restoration of blood volume is urgent, such as in burns and hypoproteinaemia. Human albumin solutions are more expensive than other colloids and crystalloids.

OBJECTIVES

To quantify the effect on mortality of human albumin and plasma protein fraction (PPF) administration in the management of critically ill patients.

SEARCH STRATEGY

We searched the Cochrane Injuries Group Specialised Register (searched 31 May 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2), MEDLINE (Ovid) (1948 to week 3 May 2011), EMBASE (Ovid) (1980 to Week 21 2011), CINAHL (EBSCO) (1982 to May 2011), ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED) (1970 to May 2011), ISI Web of Science: Conference Proceedings Citation Index - Science (CPCI-S) (1990 to May 2011), PubMed (www.ncbi.nlm.nih.gov/sites/entrez/) (searched 10 June 2011, limit: last 60 days). Reference lists of trials and review articles were checked, and authors of identified trials were contacted.

SELECTION CRITERIA

Randomised controlled trials comparing albumin or PPF with no albumin or PPF or with a crystalloid solution in critically ill patients with hypovolaemia, burns or hypoalbuminaemia.

DATA COLLECTION AND ANALYSIS

We collected data on the participants, albumin solution used, mortality at the end of follow up, and quality of allocation concealment. Analysis was stratified according to patient type.

MAIN RESULTS

We found 38 trials meeting the inclusion criteria and reporting death as an outcome. There were 1,958 deaths among 10,842 trial participants.For hypovolaemia, the relative risk of death following albumin administration was 1.02 (95% confidence interval (CI) 0.92 to 1.13). This estimate was heavily influenced by the results of the SAFE trial, which contributed 75.2% of the information (based on the weights in the meta-analysis). For burns, the relative risk was 2.93 (95% CI 1.28 to 6.72) and for hypoalbuminaemia the relative risk was 1.26 (95% CI 0.84 to 1.88). There was no substantial heterogeneity between the trials in the various categories (Chi(2) = 26.66, df = 31, P = 0.69). The pooled relative risk of death with albumin administration was 1.05 (95% CI 0.95 to 1.16).

AUTHORS' CONCLUSIONS

For patients with hypovolaemia, there is no evidence that albumin reduces mortality when compared with cheaper alternatives such as saline. There is no evidence that albumin reduces mortality in critically ill patients with burns and hypoalbuminaemia. The possibility that there may be highly selected populations of critically ill patients in which albumin may be indicated remains open to question. However, in view of the absence of evidence of a mortality benefit from albumin and the increased cost of albumin compared to alternatives such as saline, it would seem reasonable that albumin should only be used within the context of well concealed and adequately powered randomised controlled trials.

Increased blood volume following resolution of acute cardiogenic pulmonary oedema: a retrospective analysis

BACKGROUND

Acute cardiogenic pulmonary oedema (APO) occurs due to an increase in pulmonary microvascular pressure and massive transvascular fluid filtration into the lungs, causing respiratory insufficiency.

OBJECTIVE

To determine whether fluid sequestration in the lungs effectively leads to contraction of the circulating blood volume, leading to relative hypovolaemia, and whether resolution of APO and fluid shift to the vascular compartment restores the circulating volume.

METHODS

A retrospective analysis was conducted in the intensive care unit of a university teaching hospital, April - September 2007. It comprised a cohort of APO patients and a control group of patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) with similar demographics. Patient demographics, haematocrit, haemoglobin levels, total protein and albumin levels, and arterial blood gas were analysed at presentation and after clinical resolution or at 24 hours. Fluid balance charts were reviewed. Blood, plasma and cell volume changes were calculated using haemoglobin levels and haematocrit.

RESULTS

52 patients (27 with APO; 25 with COPD) were included. Median haematocrit decreased significantly and the calculated blood and plasma volumes showed statistically significant increases after treatment in the APO group when compared with the COPD group (P < 0.001). Fluid intake and output were well balanced in both groups.

CONCLUSIONS

Patients with APO are hypovolaemic at the onset relative to their state after treatment. With treatment and resolution of APO, hypovolaemia is corrected and circulating volume is restored.

[Volume replenishment in haemorrhage: caution advised]

Acute haemorrhage is a frequent problem in medicine. Patients with acute bleeding may present with signs of hypotension and reduced organ perfusion. The physician's reflex action is often to treat such patients with intravenous volume replenishment using colloid or cristalloid liquids. Intravenous volume replenishment has, however, a downside: it increases the tendency to bleed and therefore can increase blood loss. Previous clinical observations and experimental animal and human studies addressing volume replenishment in haemorrhagic shock have repeatedly shown that accepting hypotension favourably affects prognosis. However, relevant practice guidelines, such as for gastrointestinal bleeding, usually advise liberal intravenous volume replenishment if hypotension is present. In this article we advocate caution when considering intravenous blood volume adjustment in haemorrhage.

A positive fluid balance does not deteriorate tissue metabolism during fluid resuscitation of sepsis

OBJECTIVE

Hypovolemia has occurs frequently in sepsis. Due to pathologically increased permeability of the capillaries, the fluid leaks to the interstitium. An adequate fluid therapy is the corner stone to achieve circulatory stabilization and sufficient tissue perfusion; on the other hand, according to the data from the literature a tissue swelling is associated with a risk of deteriorated function of the tissues. The study aimed to examine the effect of a positive fluid balance on muscular metabolism.

METHODS

The experimental study employed the model of sepsis in the domestical pig. Ten animals were randomly distributed into a control and a septic group. Sepsis was induced by intravenous administration of E. coli, followed by fluid resuscitation by crystaloids. Microdialysis samples were withdrawn at one-hour intervals for a period of 24 hours and values of lactate, pyruvate, glycerol, and glucose.

RESULTS

Pearson's method revealed positive correlations between the lactate/pyruvate ratio and cumulative fluid balance in the septic group (R=0.292, p<0.001) and negative correlations in the control group (R=-0.279, p<0.05). In both groups, however, there was a gradual significant decrease in glycerol values.

CONCLUSION

Fluid resuscitation results in positive fluid balance in both septic and control animals. This leads to circulatory stabilization of septic animals, but not a decrease in the anaerobic share of glycolysis. A positive fluid balance in control animals does not result in alteration of muscular aerobic glycolysis. Decreasing glycerol levels in both groups give evidence that a positive fluid balance does not exert a negative impact on cell metabolism.

Phase II trial of isotonic fluid resuscitation in Kenyan children with severe malnutrition and hypovolaemia

BACKGROUND

Children with severe malnutrition who develop shock have a high mortality. Contrary to contemporaneous paediatric practice, current guidelines recommend use of low dose hypotonic fluid resuscitation (half-strength Darrows/5% dextrose (HSD/5D). We evaluated the safety and efficacy of this guideline compared to resuscitation with a standard isotonic solution.

METHODS

A Phase II randomised controlled, safety and efficacy trial in Kenyan children aged over 6 months with severe malnutrition and shock including children with severe dehydration/shock and presumptive septic shock (non-diarrhoeal shock). Eligible children were randomised to HSD/5D or Ringer's Lactate (RL). A maximum of two boluses of 15 ml/kg of HSD/5D were given over two hours (as recommended by guidelines) while those randomised to RL received 10 ml/kg aliquots half hourly (maximum 40 ml/kg). Primary endpoint was resolution of shock at 8 and 24 hours. Secondary outcomes included resolution of acidosis, adverse events and mortality.

RESULTS

61 children were enrolled: 41 had shock and severe dehydrating diarrhoea, 20 had presumptive septic shock; 69% had decompensated shock. By 8 hours response to volume resuscitation was poor with shock persisting in most children:-HSD/5D 15/22 (68%) and RL14/25 (52%), p = 0.39. Oliguria was more prevalent at 8 hours in the HSD/5D group, 9/22 (41%), compared to RL-3/25 (12%), p = 0.02. Mortality was high, HSD/5D-15/26(58%) and RL 13/29(45%); p = 0.42. Most deaths occurred within 48 hours of admission. Neither pulmonary oedema nor cardiogenic failure was detected.

CONCLUSIONS

Outcome was universally poor characterised by persistence of shock, oliguria and high case fatality. Isotonic fluid was associated with modest improvement in shock and survival when compared to HSD/5D but inconclusive due to the limitations of design and effectiveness of either resuscitation strategy. Although isotonic fluid resuscitation did not result in cardiogenic heart failure, as previously feared, we conclude that the modest volumes used and rate of infusion were insufficient to promptly correct shock. The adverse performance of the recommended fluid resuscitation guideline for severe malnutrition should prompt clinical investigation of isotonic fluids for resuscitation of compensated shock, defining rate and volumes required to inform future guidelines.

TRIAL REGISTRATION

The trial is registered as ISCRTN: 61146418.

Effects of IgM-enriched immunoglobulin and fluid replacement on nerve conduction velocity in experimental sepsis

BACKGROUND

Neuromuscular abnormalities in sepsis, termed critical illness polyneuropathy (CIP), have been suggested to be induced by inflammatory mechanisms and/or relative hypovolemia. CIP is characterized by early electrophysiological findings before the clinical symptoms. This study aimed to investigate the effect of intravenous immunoglobulin (IVIG) and volume replacement therapies on the possible nerve conduction velocity (NCV) alterations in the early phase of experimental sepsis.

METHODS

Forty-six Sprague-Dawley rats were randomly assigned to four groups. Cecal ligation/perforation was performed to induce experimental sepsis. NCV was assessed in the tail nerve.

RESULTS

There was no statistically significant difference in NCV levels within and among the Sham-operated, colloid- and IVIG-treated groups. In the sepsis without treatment group, there was a statistically significant decrease in NCV levels.

CONCLUSION

NCV is decreased in the early stage of experimental sepsis and it may be accepted as an early electrophysiological sign in CIP. Treatment with either IgM-enriched IVIG or early volume replacement appears to prevent the decrease in NCV in the early phase of experimental sepsis. Results were statistically indistinguishable between the IVIG- and colloid-treated groups. No statistical difference between these groups is noteworthy. There is a need to clarify the mechanisms of action with further randomized, clinical and experimental trials.

[Primary management and treatment of paediatric septic shock]

Paediatric shock is common. Hypovolaemic and septic shock are the main forms. Early and rapid results-oriented therapy of paediatric septic shock has a favourable effect on survival. There is an international guideline for the primary management of paediatric shock during the first hour after presentation of the patient. The goal of treatment is to prevent oxygen debt and consequently organ failure. The main symptoms of paediatric shock are tachycardia and reduced consciousness. In a child in shock, the clinical picture should be recognized within 15 minutes and an attempt should be made to reverse the situation by rapid fluid infusion. If the shock persists after 15 minutes, vasoactive medication should be given and the child should be transferred to a local paediatric intensive care unit. Intubation and mechanical ventilation are then also required.

Improved intradialytic stability during haemodialysis with blood volume-controlled ultrafiltration

BACKGROUND

Intradialytic morbid events (IMEs) during haemodialysis (HD), including symptomatic hypotension, are related to ultrafiltration (UF)-induced hypovolaemia. Blood volume monitoring and automatic feedback control of the UF rate were developed to limit the extent of hypovolaemia during dialysis. The present study investigated the effect of blood volume (BV)-controlled UF on the incidence of HD treatments with IMEs.

METHODS

This prospective randomised crossover study included hypotension-prone patients, characterised by occurrence of IMEs in at least 33% of HD treatments during a 6-week screening phase. These patients underwent 2 treatment phases, each lasting 6 weeks, in randomised order. Each patient served as their own control, treated with standard HD in one phase and with BV-controlled UF in the other phase.

RESULTS

Thirty-four patients from 9 HD centres were enrolled; 26 could be included in the analysis population. In comparison with standard HD, BV-controlled UF reduced the percentage of HD sessions complicated by IME significantly from 40%+/-27% to 32%+/-25% (p=0.02). A lower frequency of HD sessions with IME could be observed in 46% of the patients. The frequency of treatments with symptomatic hypotension was reduced from 32%+/-23% in standard HD to 24%+/-21% with BV-controlled UF (p=0.04). Changes in blood pressure and heart rate from start to end of the HD session were not different between the 2 treatment modes.

CONCLUSIONS

This crossover study showed improved intradialytic stability with BV-controlled UF, compared with standard HD.

Methods for the quantitative assessment of electrolyte disturbances in hyperglycaemia

AIM

While empirical calculations are presently used, exact solutions to compute volume and solute changes of hyperosmolar coma (HC) can be obtained by subdividing the patients according to well defined clinical and laboratory conditions. These are represented by PNa(G), the plasma Na concentration that would be present if there were only glucose addition (GA), that discloses prevalent Na depletion when >PNa(1), prevalent water deficit when <PNa(1) (value measured during HC). Exact solutions are available when Na is lost as NaCl, and when patients are subdivided according to Posm(1) (plasma osmolality during HC) >, = or <Posm(0) (the normal value). When Posm(1)=Posm(0), GA must equal the loss of ions induced by the osmotic diuresis (2 x DeltaNa), and the math solution is exact. We herein report data validating these new computational methods.

DATA SYNTHESIS

We built a mathematical model describing fluid derangements used to execute computer-simulated experiments of HC. The derangements were generated on the computer by adding, to the extra-cellular volume, different amounts of glucose while subtracting variable combinations of ions and solvent. The model yielded true solute concentrations from which our formulas computed the amounts lost or gained. These were identical to the true changes introduced to simulate the derangements (R(2)=1.00, P<0.0001) when the boundary conditions for PNa(G), exclusive NaCl loss and Posm(1)-Posm(0) were met. In patients with HC in whom these same boundary conditions were satisfied, the computations of glucose and Na changes with our new formulas were not significantly different from those estimated after correction of the derangements, considered true values (R(2)=0.60, P<0.05), and showed a satisfactory agreement with the clinical evaluation.

CONCLUSIONS

Our new methods are more accurate than the traditional ones, as they reach a better quantitative assessment of the entity of the derangements, avoiding iatrogenic dysnatraemias after correction of HC.

Methods for the quantitative assessment of electrolyte disturbances in hyperglycaemia

AIM

While empirical calculations are presently used, exact solutions to compute volume and solute changes of hyperosmolar coma (HC) can be obtained by subdividing the patients according to well defined clinical and laboratory conditions. These are represented by PNa(G), the plasma Na concentration that would be present if there were only glucose addition (GA), that discloses prevalent Na depletion when >PNa(1), prevalent water deficit when <PNa(1) (value measured during HC). Exact solutions are available when Na is lost as NaCl, and when patients are subdivided according to Posm(1) (plasma osmolality during HC) >, = or <Posm(0) (the normal value). When Posm(1)=Posm(0), GA must equal the loss of ions induced by the osmotic diuresis (2 x DeltaNa), and the math solution is exact. We herein report data validating these new computational methods.

DATA SYNTHESIS

We built a mathematical model describing fluid derangements used to execute computer-simulated experiments of HC. The derangements were generated on the computer by adding, to the extra-cellular volume, different amounts of glucose while subtracting variable combinations of ions and solvent. The model yielded true solute concentrations from which our formulas computed the amounts lost or gained. These were identical to the true changes introduced to simulate the derangements (R(2)=1.00, P<0.0001) when the boundary conditions for PNa(G), exclusive NaCl loss and Posm(1)-Posm(0) were met. In patients with HC in whom these same boundary conditions were satisfied, the computations of glucose and Na changes with our new formulas were not significantly different from those estimated after correction of the derangements, considered true values (R(2)=0.60, P<0.05), and showed a satisfactory agreement with the clinical evaluation.

CONCLUSIONS

Our new methods are more accurate than the traditional ones, as they reach a better quantitative assessment of the entity of the derangements, avoiding iatrogenic dysnatraemias after correction of HC.

[Case of cerebrospinal fluid hypovolemia possibly due to acceleration of cerebrospinal fluid absorption]

The authors present a case of a 31-year-old man suffering from intractable cerebrospinal fluid hypovolemia (CSFH), in whom autologous epidural blood patch at the cervical, thoracolumbal, and sacral sites was not effective. Repeated radionuclide cisternography reproducibly demonstrated "early accumulation of radioactivity in the bladder", "cystic accumulation of radioactivity at the sacral site" and "less activity than expected over the cerebral convexities"; but computerized tomography myelography did not demonstrate CSF leakage but detected a sacral cyst. These repeated radionuclide cisternography findings suggested unusually rapid uptake of tracer by the circulation but did not always CSF leakage. The finding of strong accumulation of radioactivity in the sacral cyst might mean the opposite CSF flow against normal caudal-cranial flow. The formation of this abnormal cranial-caudal CSF flow could be produced with CSF leakage or abnormal absorption at the caudal site, where the cyst existed in the patient. Therefore, it is not unreasonable to suppose that the sacral cyst appeared to be responsible for development of CSFH in the patient. The possibility of acceleration of cerebrospinal fluid absorption in the sacral cyst was proposed for the cause of CSFH if CSF leakage was denied.

Treatment of hyponatremia

Hyponatremia is an electrolyte disorder that is defined by a serum sodium concentration of less than 136 mmol/L. Hyponatremia occurs at a high incidence. It is commonly associated with mild to moderate mental impairment. Hypoosmolar hyponatremia occurs in the setting of plasma volume deficiency ("hypovolemia", e. g. after gastrointestinal fluid loss), liver cirrhosis and cardiac failure ("hypervolemic" hyponatremia) and syndrome of inappropriate antidiuretic hormone secretion ("euvolemic" hyponatremia). Excessive antidiuretic hormone and continued fluid intake are the pathogenetic causes of these hyponatremias. Whereas hypovolemic hyponatremia is best corrected by isotonic saline, conventional proposals for euvolemic and hypervolemic hyponatremia consist of the following: fluid restriction, lithium carbonate, demeclocycline, urea and loop diuretic. None of these nonspecific treatments is entirely satisfactory. Recently a new class of pharmacological agents -orally available vasopressin antagonists, collectively called vaptans- have been described. A number of clinical trials using vaptans have been performed already. They showed vaptans to be effective, specific and safe in the treatment of euvolemic and hypervolemic hyponatremia.

A volume loading test for the detection of hypovolemia and dehydration

BACKGROUND AND OBJECTIVES

There is a need for simple method allowing detection of dehydration and hypovolemia. Based on a new theory of homeostatic blood states, we hypothesized that hemodilution following standardized crystalloid fluid bolus can be used to discriminate between baseline normohydration and dehydration, also normovolemia and hypovolemia.

METHODS

Computer simulations based on previously published kinetic data were used to define the best time points for discrimination between baseline normohydration and dehydration, also normovolemia and hypovolemia. Hemodilution was compared at the proposed timing in 20 volunteers who received 40 infusions of Ringer's solution of 25 mL/kg during 30 minutes.

RESULTS

Simulations indicated that preexisting hypovolemia could be best detected at the end of infusion, while dehydration 20-30 min later. In baseline hypovolemia, the peak reduction of hemoglobin concentration was 16.0% at the end of infusion, while it was only 11.8%, when participants were normovolemic (P<0.004). In baseline dehydration, the residual hemodilution was 8.6%, when measured 30 min after the end of infusion. It was only 3.1% in baseline normohydration (P<0.006).

CONCLUSIONS

In response to fluid load, the baseline dehydration exaggerates the lowering of residual hemoglobin in respect to baseline. Meanwhile, baseline hypovolemia exaggerates the lowering of peak hemoglobin concentration. The volume loading test that deploys interpretation of hemoglobin dynamics in response to the test volume load could possibly serve as an easily available guide to indicate an individual patient's baseline hydration state and volemia. The introduction of continuous noninvasive monitoring of hemoglobin concentration would expand the applicability of the new method.

Impact of norepinephrine and fluid on cerebral oxygenation in experimental hemorrhagic shock

Few data exist regarding resuscitation of hypovolemic shock in infants, and alternative strategies such as vasopressor therapy merit further evaluation. However, the effects of norepinephrine on cerebral perfusion and oxygenation during hemorrhagic shock in the pediatric population are still unclear. Eight anesthetized piglets were subjected to hypotension by blood withdrawal of 25 mL/kg. Norepinephrine was titrated to achieve baseline mean arterial blood pressure (MAP), and cerebral oxygenation was determined by brain tissue Po2 (Ptio2) and near-infrared spectroscopy-derived tissue oxygen index (TOI). Then, norepinephrine was stopped, MAP was allowed to decrease again below 30 mm Hg, and shed blood was retransfused. During hemorrhage, TOI dropped from 69+/-3 to 59+/-3%, and Ptio2 from 29+/-6 to 13+/-1 mm Hg (mean+/-SEM; p<0.001). Following norepinephrine, cerebral perfusion pressure (CPP) could be restored immediately, whereas TOI and Ptio2 did not increase significantly. In contrast, following retransfusion, TOI and Ptio2 increased to 68+/-3% and 27+/-7 mm Hg reaching baseline values, respectively. In conclusion, while norepinephrine increased CPP immediately, cerebral oxygenation as reflected by TOI and Ptio2 could not be improved by norepinephrine, but only by retransfusion.

Intrathoracic pressure regulation for intracranial pressure management in normovolemic and hypovolemic pigs

OBJECTIVE

To evaluate the potential to use subatmospheric intrathoracic pressure to regulate intracranial pressure (ICP) in normovolemic and hypovolemic animals, we tested the hypothesis that mechanical devices designed to reduce intrathoracic pressure will decrease ICP in a dose-related manner. An inspiratory impedance threshold device was used in spontaneously breathing animals and an intrathoracic pressure regulator was attached to a positive pressure ventilator and used in apneic animals: both devices lower intrathoracic pressure.

DESIGN

Prospective, randomized animal study.

SETTING

Animal laboratory facilities.

SUBJECTS

A total of 36 female farm pigs in four different protocols (n = 12, 6, 12, and 6, respectively).

INTERVENTIONS, MEASUREMENTS, AND MAIN RESULTS

In all protocols, endotracheal, right atrial, central aortic, and ICP were measured continuously. In protocol 1, spontaneously breathing animals were randomized to breath for 15 mins through an impedance threshold device with a cracking pressure of -10 or -15 mm Hg. In protocol 2, after untreated ventricular fibrillation for 4 mins and successful defibrillation to a normal rhythm, spontaneously breathing pigs were used to evaluate the effect of two different impedance threshold device cracking pressures (-10 and -15 mm Hg) on increased ICP. In protocol 3, the acute effects of an intrathoracic pressure regulator on ICP were evaluated in combination with a positive pressure mechanical ventilator in apneic hypovolemic hypotensive pigs after 35% or 50% blood loss. In protocol 4, after 40% blood loss, an intrathoracic pressure regulator was applied for 120 mins and ICP was recorded to determine whether the intrathoracic pressure regulator effects were sustained over time. Inspiratory impedance successfully decreased ICP in spontaneously breathing pigs in a dose-dependent manner and decreased elevated ICP immediately after cardiac arrest and successful resuscitation. The same effect was seen in apneic animals with the use of the intrathoracic pressure regulator. The effect was more pronounced in hypovolemia, and it was sustained for >/=2 hrs.

CONCLUSIONS

Reduction of intrathoracic pressure to subatmospheric levels resulted in an instantaneous and sustained reduction in ICP in spontaneously breathing and apneic animals. The effect was most pronounced in the hypovolemic animals.

Are Selective Lung Recruitment Maneuvers Hemodynamically Safe in Severe Hypovolemia? An Experimental Study in Hypovolemic Pigs with Lobar Collapse

BACKGROUND

We have previously shown, in normovolemic pigs, that a selective lung recruitment maneuver (S-LRM), i.e., insufflation of air-oxygen via a balloon catheter with its tip located in the bronchus of a collapsed lung lobe, effectively improves oxygenation and lung volume without affecting hemodynamics negatively. In this study, we examined the respiratory and circulatory effects of S-LRM during hypovolemia with compromised circulation.

METHODS

In eight ventilated (fraction of inspired oxygen, Fio2 1.0) and anesthetized pigs a balloon catheter was inserted in the bronchus of the right lower lung lobe. The lobe was selectively lavaged to create a dense lobar collapse. The pigs were then subjected to S-LRM (40 cm H2O airway pressure for 30 s) at normovolemia, after venesection of 20% and 40% of the blood volume, respectively. Blood gases, compliance of the respiratory system (Crs), vascular pressures, and cardiac output were registered before, during, and after the S-LRM.

RESULTS

Pao2, venous admixture, and Crs improved significantly with S-LRM at all three volume levels. No change in hemodynamics with S-LRM occurred in normovolemia and 20% hypovolemia. For 40% hypovolemia, cardiac output was unchanged by S-LRM, whereas minor decreases in mean arterial blood pressure were seen: 48 (37-52) mm Hg (median, 25th and 75th percentiles) 3 min before S-LRM, 40 (35-44) mm Hg at the end of S-LRM (P = 0.0207), and 47 (39-54) mm Hg 3 min after S-LRM.

CONCLUSION

A S-LRM effectively improved oxygenation and Crs and had only minor circulatory side effects, even in severe hypovolemia in this animal model of lobar collapse.

Determinanten des insensiblen Flüssigkeitsverlustes

Accurate perioperative fluid balance is the basis of a targeted infusion regimen. However, neither the initial status nor perioperative changes of the fluid compartments can be reliably measured in daily routine. In particular, insensible losses are not consistently assessed, so that substitution therapy is generally empirical. The object of this paper is to communicate the scientific data on this topic. Preoperative fasting (10 h) does not per se cause intravascular hypovolemia. In adults, total basal evaporation by way of the skin and airways and of any wounds during major abdominal interventions is usually less than 1 ml/kg/h. An inconstant fluid and protein shift towards the interstitial space perioperatively seems to be associated with hypervolemia, which suggests it should be preventable. The decisive factor in this context seems to be deterioration of the endothelial glycocalyx, whose further patho-physiological impact is currently only partially known. Clinical studies have revealed a link between fluid restriction and improved outcome after major abdominal surgery.

Comparative effects of early versus delayed use of norepinephrine in resuscitated endotoxic shock

OBJECTIVE

To assess hemodynamic, tissue oxygenation, and tissue perfusion changes by comparing traditional therapy (fluid resuscitation followed by vasopressor treatment) and alternative therapy (early vasopressor treatment) in a hyperkinetic and sedated model of endotoxic shock.

DESIGN

Prospective controlled experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Rats were anesthetized, mechanically ventilated, paralyzed, and instrumented to measure mean arterial pressure, heart rate, pulse pressure variation, aortic and mesenteric blood flow, muscle and liver tissue oxygen pressure, blood gas, and lactate. Rats were randomly divided into five groups (n = 7): endotoxin alone (Endo), endotoxin plus norepinephrine (Endo/NE), endotoxin plus fluid therapy alone (ENDO/Fl), endotoxin plus fluid therapy plus late catecholamine (Endo/Fl/Late NE), and endotoxin plus fluid therapy plus simultaneous norepinephrine administration (Endo/Fl/Early NE).

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure increased to baseline values only in the catecholamine-treated group (p < .05). In ENDO/Fl, Endo/Fl/Late NE, and Endo/Fl/Early NE, aortic blood flow was maintained. Mesenteric blood flow was maintained at baseline values only in the catecholamine-treated groups. Mesenteric/aortic blood flow ratio was higher in the early catecholamine group (p < .05). Endo and ENDO/Fl were associated with a marked decrease in liver PO2, which was maintained in catecholamine-treated groups (p < .01). Plasma lactate was lower in the Endo/Fl/Early NE group. Volume resuscitation was higher in Endo and Endo/Fl/Late NE groups with 28 +/- 6 and 27 +/- 4 mL, respectively, when compared with the Endo/Fl/Early NE group (19 +/- 3 mL) (p < .05).

CONCLUSIONS

The use of norepinephrine was associated with improved mean arterial pressure, sustained aortic and mesenteric blood flow, and better tissue oxygenation when compared with fluid resuscitation alone, irrespective of time of administration. The early use of norepinephrine plus volume expansion was associated with a higher proportion of blood flow redistributed to the mesenteric area, lower lactate levels, and less infused volume. Thus, the early use of norepinephrine is safe and may decrease the need for volume resuscitation.

Intravenous hypertonic NaCl acts via cerebral sodium-sensitive and angiotensinergic mechanisms to improve cardiac function in haemorrhaged conscious sheep

Acute NaCl loading as resuscitation in haemorrhagic hypovolaemia is known to induce rapid cardiovascular recovery. Besides an osmotically induced increase in plasma volume the physiological mechanisms of action are unknown. We hypothesized that a CNS mechanism, elicited by increased periventricular [Na(+)] and mediated by angiotensin II type 1 receptors (AT(1)), is obligatory for the full effect of hypertonic NaCl. To test this we investigated the cardiovascular responses to haemorrhage and subsequent hypertonic NaCl infusion (7.5% NaCl, 4 ml (kg BW)(-1)) in six conscious sheep subjected to intracerebroventricular (i.c.v.) infusion of artificial cerebrospinal fluid (aCSF; control), mannitol solution (Man; 75 mmol l(-1) [Na(+)], total osmolality 295 mosmol kg(-1)) or losartan (Los; 1 mg ml(-1), AT(1) receptor antagonist) at three different occasions. Man normalized (144 +/- 6 mmol l(-1), mean +/- s.d.) the increase in i.c.v. [Na(+)] seen after aCSF (161 +/- 2 mmol l(-1)). Compared with control, both Man and Los significantly (P < 0.05) attenuated the improvement in mean arterial blood pressure (MAP), cardiac index and mesenteric blood flow (SMBF) in response to intravenous hypertonic NaCl: MAP, rapid response +45 mmHg versus +38 mmHg (Man) and +35 mmHg (Los); after 180 min, +32 mmHg versus +21 mmHg (Man) and +19 mmHg (Los); cardiac index after 180 min, +1.9 l min(-1) (m(2))(-1) versus +0.9 l min(-1) (m(2))(-1) (Man) and +0.9 l min(-1) (m(2))(-1) (Los); SMBF rapid response, +981 ml min(-1) versus +719 ml min(-1) (Man) and +744 ml min(-1) (Los); after 180 min, +602 ml min(-1) versus +372 ml min(-1) (Man) and +314 ml min(-1) (Los). The results suggest that increased periventricular [Na(+)] and cerebral AT(1) receptors contribute, together with plasma volume expansion, to improve systemic haemodynamics after treatment with hypertonic NaCl in haemorrhagic hypovolaemia.

Identifying physiological measurements for medical monitoring: implications for autonomous health care in austere environments

In a patient who has lost a significant amount of blood, avoiding cardiovascular collapse and impending circulatory shock depends on the ability to maintain adequate arterial blood pressure in the presence of significant central hypovolemia. Our analysis of hemodynamic, autonomic, and metabolic data obtained from healthy human subjects exposed to progressive reduction in central blood volume and supported by data from trauma patients provide evidence to support the following conclusions: 1. Because of autonomically-mediated compensatory mechanisms, standard vital signs can remain unchanged or change too late, when cardiovascular collapse is imminent. 2. Currently proposed closed-loop resuscitation and oxygen delivery systems controlled by arterial blood pressure and SpO2 may prove inadequate for early intervention decision-support. 3. Continuous capture of PP, ECG R-wave amplitude, indices of HRV, cardiac BRS, and/or muscle PO2 could improve the sensitivity of closed-loop resuscitation and oxygen delivery by providing earlier indications of clinical status.

Blood Volume Perturbations in the Postural Tachycardia Syndrome

The postural tachycardia syndrome (POTS) is characterized by excessive orthostatic tachycardia with chronic symptoms that are associated with upright posture. These chronic symptoms (of at least 6 months' duration) include tachycardia, exercise intolerance, lightheadedness, extreme fatigue, headache, and mental clouding. Patients with POTS demonstrate an increase in heart rate of at least 30 beats/min within 5 to 30 minutes of assuming an upright posture, in the absence of orthostatic hypotension (a fall in blood pressure >20/10 mm Hg) and in the absence of other medical disorders that might cause tachycardia. POTS can be associated with a high degree of functional disability. The blood volume has been found to be low in many patients with POTS. This article will review some of the data regarding blood volume perturbations in POTS, blood volume regulation in POTS, and potential treatment approaches.

The critically ill injured patient

Patients admitted to the ICU after severe trauma require frequent procedures in the operating room, particularly in cases where a damage control strategy is used. The ventilatory management of these patients in the operating room can be particularly challenging. These patients often have severely impaired respiratory mechanics because of acute lung injury and abdominal compartment syndrome. Consequently, the pressure and flow generation capabilities of standard anesthesia ventilators may be inadequate to support ventilation and gas exchange. This article presents the problems that may be encountered in patients who have severe abdominal and lung injuries, and the current management concepts used in caring for these patients in the critical care setting, to provide guidelines for the anesthetist faced with these patients in the operating room.

Diagnosis of central hypovolemia by using passive leg raising

OBJECTIVE

Suspected central hypovolemia is a frequent clinical situation in hospitalized patients, and no simple bedside diagnostic test in spontaneously breathing patients is available. We tested the value of passive leg raising to predict hemodynamic improvement after fluid expansion in patients with suspected central hypovolemia.

DESIGN AND SETTING

Prospective study in four intensive care units at the Amiens university hospital. Thirty-four spontaneously breathing patients with suspected hypovolemia were included and were classified as responders (cardiac output increased by 12% or more after fluid expansion) or nonresponders. Patients were analyzed in the supine position during 30 degrees leg raising and after fluid expansion.

MEASUREMENTS AND RESULTS

Stroke volume and cardiac output determined by echocardiographic and Doppler techniques and heart rate and blood pressure were measured at baseline, during passive leg raising and after fluid expansion. An increase of cardiac output or stroke volume by 12% or more during passive leg raising was highly predictive of central hypovolemia (AUC 0.89+/-0.06, 95% CI 0.73-0.97 for cardiac output and AUC 0.9+/-0.06, 95% CI 0.74-0.97 for stroke volume). Sensitivity and specificity values were 63% and 89% for cardiac output and 69%, 89% for stroke volume respectively. A close correlation (r=0.75; p<0.0001) was observed between cardiac output changes during leg raising and changes in cardiac output after fluid expansion.

CONCLUSIONS

Bedside measurement of cardiac output or stroke volume by Doppler techniques during passive leg raising was predictive of a positive hemodynamic effect of fluid expansion in spontaneously breathing patients with suspected central hypovolemia.

Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat

This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of ∼185 min (33°C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36°C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na+, osmolality, aldosterone, and arginine vasopressin concentrations were elevated ( P < 0.05) in each trial, accompanied by a −4% hemoconcentration. Following Rehy, there were no differences ( P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na+, osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different ( P > 0.05) among the Rehy treatments. Plasma osmolality, Na+, percent change in plasma volume, and fluid regulatory hormones responded similarly among all Rehy treatments. Neither a fluid of greater tonicity nor the route of administration resulted in a more rapid or greater fluid retention, nor did it enhance heat tolerance or diminish physiological strain during subsequent exercise in the heat.

Pulse Pressure Respiratory Variation as an Early Marker of Cardiac Output Fall in Experimental Hemorrhagic Shock

Pulse pressure (DeltaPp) and systolic pressure (DeltaPs) variations have been recommended as predictors of fluid responsiveness in critically ill patients. We hypothesized that changes in DeltaPp and DeltaPs parallel alterations in stroke volume (SV) and cardiac output (CO) during hemorrhage, shock, and resuscitation. In anesthetized and mechanically ventilated mongrel dogs, a graded hemorrhage (20 mL/min) was induced to a target mean arterial pressure (MAP) of 40 mm Hg, which was maintained for additional 30 min. Total shed-blood volume was then retransfused at a 40 mL/min rate. CO, SV, right atrial pressure (RAP), pulmonary artery occlusion pressure (PAOP), and continuous mixed venous oxygen saturation (SvO(2)) were assessed. Both DeltaPp and DeltaPs were calculated from direct arterial pressure waveform. Removal of about 9% of estimated blood volume promoted a reduction in SV (14.8 +/- 2.2 to 10.6 +/- 1.3 mL, P < 0.05). At approximately 18% blood volume removal, significant changes in CO (2.4 +/- 0.2 to 1.5 +/- 0.2 mL/min, P < 0.05), DeltaPp (12.6 +/- 1.4 to 15.8 +/- 2.0%, P < 0.05), and SvO(2) (82 +/- 1.4 to 73 +/- 1.7%, P < 0.05) were observed. Alterations in MAP, RAP, PAOP, and DeltaPs could be detected only after each animal had lost over 36% of estimated initial blood volume. There was correlation between blood volume loss and SV, CO, and SvO(2), as well as between blood loss and MAP, DeltaPp, and DeltaPs. Blood volume loss showed no correlation with cardiac filling pressures. DeltaPp is a useful, early marker of SV and CO for the assessment of cardiac preload changes in hemorrhagic shock, while cardiac filling pressures are not.

A total balanced volume replacement strategy using a new balanced hydoxyethyl starch preparation (6% HES 130/0.42) in patients undergoing major abdominal surgery

BACKGROUND AND OBJECTIVE

The kind of fluid for correcting hypovolaemia is still a focus of debate. In a prospective, randomized, controlled and double-blind study in patients undergoing major abdominal surgery, a total balanced volume replacement strategy including a new balanced hydroxyethyl starch (HES) solution was compared with a conventional, non-balanced fluid regimen.

METHODS

In Group A (n = 15), a new balanced 6% HES 130/0.42 was given along with a balanced crystalloid solution; in Group B (n = 15), an unbalanced conventional HES 130/0.42 plus an unbalanced crystalloid (saline solution) were administered. Volume was given when mean arterial pressure (MAP) was <65 mmHg and central venous pressure (CVP) minus positive end-expiratoric pressure (PEEP) level was <10 mmHg. Haemodynamics, acid-base status, coagulation (thrombelastography (TEG)) and kidney function (including kidney-specific proteins, N-acetyl-beta-d-glucosaminidase (beta-NAG) and alpha-1-microglobulin) were measured after induction of anaesthesia, at the end of surgery, 5 and 24 h after surgery.

RESULTS

Group A received 3533 +/- 1302 mL of HES and 5333 +/- 1063 mL of crystalloids, in Group B, 3866 +/- 1674 mL of HES and 5966 +/- 1202 mL of crystalloids were given. Haemodynamics, laboratory data, TEG data and kidney function were without significant differences between the groups. Cl- concentration and base excess (-5 +/- 2.4 mmol L-1 vs. 0.4 +/- 2.4 mmol L-1) were significantly higher in patients of Group B than of Group A.

CONCLUSIONS

A complete balanced volume replacement strategy including a new balanced HES preparation resulted in significantly less derangement in acid-base status compared with a non-balanced volume replacement regimen. The new HES preparation showed no negative effects on coagulation and kidney function.

[Perioperative colloid administration: a survey of Spanish anesthesiologists' attitudes]

OBJECTIVES

To determine the availability of intravascular fluid volume replacement solutions in Spanish hospitals, to survey the extent of use of colloids by anesthesiologists, to ascertain the possible adverse effects they seek to prevent when using each solution, and to assess their level of knowledge about the subject.

MATERIAL AND METHODS

A questionnaire was administered over a period of 6 months (July 2004-January 2005). The questionnaire was available online at www.encuestacoloides.com. The address was distributed by e-mail to anesthesiologists of all the Spanish autonomous communities and published in the Revista Española de Anestesiología y Reanimación.

RESULTS

One hundred forty-two anesthesiologists responded. Crystalloids and colloids were widely available in most hospitals. Hydroxyethyl starch (HES) solutions were the colloids most often used (73%), followed by gelatins (28%). Dextran solutions, on the other hand, were no longer being used. The reasons the respondents gave for using these solutions were related to the time they remained in the vascular system, their greater effect of volume expansion, and the preservation of hemostasis. The most-feared complication was anaphylactic reaction to gelatins and there were concerns about the dose limit for infusion of HES solutions and about hemodynamic instability caused by dextran solutions. Fifty-four percent felt that scientific meetings provide little information about colloids and volume replacement.

CONCLUSIONS

There is widespread use of colloids other than dextran along with crystalloids for plasma volume replacement. Spanish anesthesiologists are clear about important concepts related to colloid use. However, a high percentage have doubts about certain fundamental issues. Continuing professional development opportunities related to intravascular fluid replacement therapy should be increased.

[Hypotension in the very preterm infant]

One out of four very preterm infants will present with circulatory maladaptation during the first two days of life, with an increased risk of early complications and long term sequelae. Appreciation of those transitional difficulties cannot be limited to blood pressure. Assesment of blood pressure itself must be done in relation with gestational age and birth weight adapted norms. The effects of therapies for low systemic blood flow on blood pressure, organs and cerebral circulations are better understood, but none of them has assessed for mortality or neurodevelopmental outcomes.

Invasive und nichtinvasive Diagnostik der Hypovolämie bei akuter Pankreatitis

Severe acute pancreatitis leads to a dramatic fluid loss in the intraperitoneal space which may result in circulatory decompensation. Sequestration of fluid can amount up to 40 percent of the circulating blood volume. The amount of fluid and electrolyte replacement is often misjudged leading to a higher rate of complications and a higher mortality rate of the disease. Furthermore, subsequent and adequate fluid resuscitation seems to influence the prognostic course of the disease by improving the perfusion and oxygenation of the pancreas. Otherwise volume overload may cause cardiopulmonary decompensation in the case of synchronous cardiopulmonary comorbidities. Therefore, an important part of treatment relies on careful haemodynamic monitoring, if necessary managed in an intensive care unit. Usually most patients with acute pancreatitis will be treated on a non-intensive medical ward which allows a differentiated and continuous haemodynamic monitoring only to a limited extent. Apart from monitoring circulatory parameters and measuring central venous pressure, there are other clinical methods, laboratory tests and radiological diagnostic procedures to determine the amount of intravascular fluid deficit and the individual volume demand of patients with acute pancreatitis. Prospective clinical trials for evaluation of pancreatitis-specific volume management do not exist so far. The aim of this review is to provide background information on invasive and non-invasive diagnostic methods for detection of circulatory hypovolemia in acute pancreatitis.

Emergent Fetal Intracardiac Transfusion for Thrombocytopenia and Acute Hypovolemia due to Cordocentesis-Associated Hemorrhage in Parvovirus-Induced Hydrops

OBJECTIVES

To demonstrate the utility of fetal intracardiac transfusion to correct acute fetal hypovolemia and thrombocytopenia in fetal Parvovirus infection.

METHODS

Intracardiac transfusion in a 19-week gestation was indicated due to cordocentesis-associated hemorrhage.

RESULTS

Intracardiac transfusion resulted in correction of acute bradycardia, anemia and thrombocytopenia and persistent umbilical cord hemorrhage following attempted intravascular transfusion.

CONCLUSIONS

This case illustrates the importance of anticipating both thrombocytopenia and anemia in fetal Parvovirus infection and how an intracardiac approach can be employed in the setting of acute, life-threatening hemorrhage.

[The practice guideline 'Volume suppletion in critically-ill neonates and children up to the age of 18 years' of the Dutch Paediatric Association]

Hypovolaemia is the most common cause of circulatory failure in children. Treatment consists of volume suppletion with a crystalloid or colloid solution; which agent is the best in children is not clear. This evidence-based practice guideline formulates recommendations as to which fluid should be used for volume suppletion in critically-ill neonates and children up to the age of 18 years with hypovolaemia. Before the guideline development first-choice fluid for volume resuscitation was in 50% a colloid and in 50% a crystalloid solution for both neonatologists and paediatric intensivists. The neonatologists used human albumin as a priority, and the paeditric intensivists predominantly used a synthetic colloid. The guideline was developed on the basis of a comprehensive search and analysis of the literature according to the principles of evidence-based guideline development. The recommendations were formulated by a committee based on evidence from the literature and, when evidence from the literature was insufficient, on consensus after discussion in the committee. Since colloids are much more expensive than crystalloids and can give an anaphylactic reaction, their added value over crystalloids must be proven. In sick neonates and children, insufficient clinical trials have been done to reach the conclusion that colloids are more effective than crystalloids in hypovolaemia. A number of meta-analyses in adults revealed excess mortality in the group treated with albumin, but one recent, large, randomised study showed no difference in mortality. No added value could be demonstrated for the administration of synthetic colloids. On the basis of data from the literature and considerations regarding the applicability of evidence in adults to children and neonates, the side effects of resuscitation fluids, pathophysiology and costs, the first-choice fluid for neonates and children with hypovolaemia is isotonic saline. Albumin should not be used for the treatment of hypovolaemia. The volume to be administered and the infusion rate depend on the severity of the hypovolaemia and should be determined on an individual basis.

Critical care delivery: the experience of a civilian terrorist attack

It has been recognised for some time that a terrorist incident was threatened in the U.K. and it has been noted previously in the JRAMC that the locations for terrorist atrocities are likely to be more diverse than previously experienced. July 7th 2005 witnessed the first terrorist suicide bombing on the U.K. mainland, targeting the public transport system in London. These attacks were unprecedented in both scale and intensity but they were anticipated in London. However there were clear difficulties, relating to multiple sites, their location underground and early problems with communication (2). This article highlights some of the experiences and learning points of the Intensive Care Medicine Service at the Royal London Hospital (RLH) in the wake of the July 7th bombings. The RLH was the single biggest receiver of casualties (195); seven of whom were admitted to the Intensive Care Unit. The Defence Medical Services have tri-service representation (both regular and reserve) at the RLH in Emergency Medicine and Pre-hospital Care, Surgical Services and Intensive Care Medicine.

Hypovolemia and dehydration in the oncology patient

Dehydration is commonly but often inappropriately diagnosed in cancer patients. Dehydration is the loss of water from the intracellular compartment due to hypernatremia. Dehydration can occur among patients who are hypervolemic, euvolemic, or hypovolemic. Cancer patients are more often hypovolemic, reflecting depletion of water from the extracellular space due to excessive loss, such as from vomiting and diarrhea, or inadequate intake of fluids. Hypovolemia can be hypernatremic, eunatremic, or hyponatremic. The appropriate state of the patient should be determined prior to attempts at correcting the problem. A hyponatremic patient would rehydrate more quickly with a solution higher in sodium, whereas this solution could be dangerous for a hypernatremic patient. Rapid or inappropriate treatment of hypernatremia can lead to death. Subjective findings, physical findings, and laboratory values will help direct the appropriate resuscitation methods. This paper reviews the physiologic control of extracellular volume and electrolytes, diagnosis of sodium and water balance problems, and the management of these concerns.

Evidence based checklists for objective structured clinical examinations

How doctors examine a patient is often influenced more by tradition than by evidence. But trainees should be assessed on what works and not personal preferences

Intrathoracic pressure regulation improves vital organ perfusion pressures in normovolemic and hypovolemic pigs

BACKGROUND

The intrathoracic pressure regulator (ITPR) was created to improve hemodynamics by generating continuous negative airway pressure between positive pressure ventilations to enhance cardiac preload in apnoeic animals. In normovolemic and hypovolemic pigs, we tested the hypothesis that continuous negative intrathoracic pressure set at -5 or -10mmHg, interrupted only for intermittent positive pressure ventilations, would decrease intracranial (ICP) and right atrial (RAP) pressure, and increase mean arterial pressure (MAP).

METHODS

Twelve pigs were anesthetized with propofol and ventilated with a bag. The ITPR was used to vary baseline endotracheal pressures (ETPs) for 5min periods in the following sequence: 0, -5, 0, -10, 0mmHg under normovolemic conditions. Six pigs were bled 50% (32.5+/-mL/kg) of their estimated blood volume and the airway pressure sequence was repeated. Six other pigs were bled 35% (22.75+/-mL/kg) of their estimated blood volume and the same airway pressure sequence was repeated. Intracranial, aortic, right atrial pressures, arterial blood gases, end tidal CO(2) (ETCO(2)), were measured. ANOVA was used for statistical analysis. Linear regression analysis was performed for ETP and ICP.

RESULTS

Mean arterial and vital organ perfusion pressures were significantly improved and RA pressure significantly decreased with the use of the ITPR; the effect was greater with the more negative ETPs and lower circulating blood volume. The change of ICP was linearly related to the ETP and blood loss: DeltaICP=[1.22-0.84(1-%blood loss/100)]xETP, r(2)=0.88 (in mmHg), p<0.001. There were no adverse device effects and there was a significant increase of ETCO(2) with the use of ITPR.

CONCLUSION

The ITPR decreased RAP and ICP significantly and improved mean arterial and cerebral and coronary perfusion pressures without affecting acid base balance severely. The decrease in ICP was directly proportional to the reduction in intrathoracic pressure. The effects were more pronounced in severe hypovolemic and hypotensive states with more negative ETP pressure.

Fluid resuscitation in neonatal and pediatric hypovolemic shock: a Dutch Pediatric Society evidence-based clinical practice guideline

OBJECTIVE

To develop a clinical practice guideline that provides recommendations for the fluid, i.e. colloid or crystalloid, used for resuscitation in critically ill neonates and children up to the age of 18 years with hypovolemia.

METHODS

The guideline was developed through a comprehensive search and analysis of the pediatric literature. Recommendations were formulated by a national multidisciplinary committee involving all stakeholders in neonatal and pediatric intensive care and were based on research evidence from the literature and, in areas where the evidence was insufficient or lacking, on consensus after discussions in the committee.

RESULTS

Because of the lack of evidence in neonates and children, trials conducted in adults were considered. We found several recent meta-analyses that show excess mortality in albumin-treated groups, compared with crystalloid-treated groups, and one recent large randomized controlled trial that found evidence of no mortality difference. We found no evidence that synthetic colloids are superior to crystalloid solutions.

CONCLUSIONS

Given the state of the evidence and taking all other considerations into account, the guideline-developing group and the multidisciplinary committee recommend that in neonates and children with hypovolemia the first-choice fluid for resuscitation should be isotonic saline.