Improved outcome based on fluid management in critically ill patients requiring pulmonary artery catheterization

Transesophageal pulsed Doppler echocardiography of pulmonary venous flow to assess left ventricular filling pressure in ventilated patients with acute respiratory distress syndrome

OBJECTIVE

To determine whether the systolic fraction (SF) of the pulmonary venous flow (PVF), measured by transesophageal echocardiography (TEE) could be used to estimate the pulmonary artery occlusion pressure (PAOP).

DESIGN

Prospective clinical investigation.

PATIENTS

Nineteen intubated patients with ARDS.

INTERVENTIONS

Doppler examinations with measurement of the SF of the PVF (ie, the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integrals) were performed simultaneously with measurements of PAOP via a right heart catheter at 0 cmH2O PEEP (ZEEP), at PEEP = 8 cmH20 and at PEEP = 16 cmH2O.

MEASUREMENTS AND MAIN RESULTS

At ZEEP, PAOP was inversely correlated with the SF of the PVF (r = -.89). The difference of SF between the group with PAOP <18 mm Hg and the group with PAOP > or = 18 mm Hg was statistically significant (P < .05). A SF > or = 55% predicted a PAOP < 15 mm Hg with a positive predictive value of 100% (95% CI = 63-100%). A SF < or = 40% predicted a PAOP > or =18 mm Hg with a positive predictive value of 100% (95% CI = 52-100%). At PEEP = 8 cm H20 (12 patients studied) and at PEEP = 16 cmH2O (10 patients studied), PAOP was inversely correlated with the SF of the PVF: r = -.84, and r = -.85, respectively.

CONCLUSION

The SF of the PVF measured by Pulsed Doppler TEE seems to be a valuable index to estimate the left ventricular filling pressure in mechanically ventilated patients with ARDS.

Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

INTRODUCTION

There is no consensus definition of acute renal failure (ARF) in critically ill patients. More than 30 different definitions have been used in the literature, creating much confusion and making comparisons difficult. Similarly, strong debate exists on the validity and clinical relevance of animal models of ARF; on choices of fluid management and of end-points for trials of new interventions in this field; and on how information technology can be used to assist this process. Accordingly, we sought to review the available evidence, make recommendations and delineate key questions for future studies.

METHODS

We undertook a systematic review of the literature using Medline and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated recommendations and/or directions for future research.

RESULTS

We found sufficient consensus on 47 questions to allow the development of recommendations. Importantly, we were able to develop a consensus definition for ARF. In some cases it was also possible to issue useful consensus recommendations for future investigations. We present a summary of the findings. (Full versions of the six workgroups' findings are available on the internet at http://www.ADQI.net)

CONCLUSION

Despite limited data, broad areas of consensus exist for the physiological and clinical principles needed to guide the development of consensus recommendations for defining ARF, selection of animal models, methods of monitoring fluid therapy, choice of physiological and clinical end-points for trials, and the possible role of information technology.

Accuracy of transpulmonary thermodilution versus gravimetric measurement of extravascular lung water

OBJECTIVE

Pulmonary edema is a severe and often life-threatening condition. The diagnosis of pulmonary edema and its quantification have great clinical significance and yet can be difficult. A new technique based on thermodilution measurement using a single indicator has recently been developed (PiCCO, Pulsion Medical Systems, AG Germany). This method allows the measurement of extravascular lung water and thus can quantify degree of pulmonary edema. The technique has not been compared with a gold standard, gravimetric measurement of extravascular lung water. Therefore, the objective of this study was to determine the ability of extravascular lung water measurement with the PiCCO to reflect the extravascular lung water as measured with a gravimetric technique in a dog model of pulmonary edema.

DESIGN

Prospective, randomized animal study.

SETTING

A university animal research laboratory.

SUBJECTS

Fifteen mongrel dogs (n = 5/group) weighing 20-30 kg.

INTERVENTIONS

The dogs were anesthetized and mechanically ventilated. Five dogs served as controls; in five dogs hydrostatic pulmonary edema was induced using inflation of a left atrial balloon combined with fluid administration to maintain a high pulmonary artery occlusion pressure; and in five dogs pulmonary edema was induced by intravenous injection of oleic acid. After a period of stabilization in a state of pulmonary edema, extravascular lung water was measured with the PiCCO monitor. The animals were then killed, and extravascular lung water was measured using a gravimetric technique.

MEASUREMENTS AND MAIN RESULTS

There was a very close (r =.967, p <.001) relationship between transpulmonary thermodilution and gravimetric measurements. The measurement with the PiCCO was consistently higher, by 3.01 +/- 1.34 mL/kg, than the gravimetric measurement.

CONCLUSIONS

Measurement of extravascular lung water using transpulmonary thermodilution with a single indicator is very closely correlated with gravimetric measurement of lung water in both increased permeability and hydrostatic pulmonary edema.

Acute lung injury and acute respiratory distress syndrome

Acute lung injury and acute respiratory distress syndrome are an important challenge for pediatric intensive care units. These disorders are characterized by a significant inflammatory response to a local (pulmonary) or remote (systemic) insult resulting in injury to alveolar epithelial and endothelial barriers of the lung, acute inflammation and protein rich pulmonary edema. The reported rates in children vary from 8.5 to 16 cases / 1000 pediatric intensive care unit (PICU) admissions. The pathological features of ARDS are described as passing through three overlapping phases - an inflammatory or exudative phase (0-7 days), a proliferative phase (7-21 days) and lastly a fibrotic phase (from day 10). The treatment of ARDS rests on good supportive care and control of initiating cause. The goal of ventilating patients with ALI/ARDS should be to maintain adequate gas exchange with minimal ventilator induced lung injury. This can be achieved by use of optimum PEEP, low tidal volume and appropriate FiO2. High frequency ventilation can improve oxygenation but does affect the outcomes. Prone positioning is a useful strategy to improve oxygenation. Pharmacological strategies have not made any significant impact on the outcomes. Preliminary data suggests some role for use of corticosteroids in non-resolving ARDS. The mortality rates have declined over the last decade chiefly due to the advances in supporting critically ill patients.

Fluids reverse the early lipopolysaccharide-induced albumin leakage in rodent mesenteric venules

OBJECTIVE

Volume resuscitation is clinically beneficial in patients with sepsis, but few data exist concerning the effects of fluid administration on early events in the inflammatory process. Vascular permeability, leukocyte rolling and leukocyte adhesion in the rodent mesenteric microcirculation were assessed in vivo using intravital microscopy, and the effect of fluid administration on lipopolysaccharide (LPS)-induced changes recorded.

DESIGN

Prospective, repeated measures study.

SETTING

University hospital laboratory.

SUBJECTS

Male Wistar rats in six groups.

INTERVENTIONS

All animals underwent intravital microscopic examination of mesenteric post-capillary venules. LPS or vehicle was applied topically. Animals received either no additional fluids, 0.9% saline (16 ml/kg per h) or 5% human albumin (16 ml/kg per h) commencing 30 min prior to LPS/vehicle administration.

MEASUREMENTS AND MAIN RESULTS

Leukocyte rolling, firm adhesion and blood velocity were observed directly. Vascular permeability was assessed using the flux of fluorescently labelled albumin into the interstitium. LPS significantly increased the median (IQR) number of leukocytes rolling and firmly adherent relative to baseline (at 60 min rolling increased from 12.0 (10.3-13.8) to 40.3 (36.0-47.5) cells/min; adhesion increased from 1 (1-2) to 17 (12-26) cells/100 microm; n=5, p<0.01). Transvascular albumin flux was significantly increased 45 min after LPS application (p<0.01), but not after vehicle. Administration of either 0.9% saline (n=5) or 5% human albumin (n=6), significantly attenuated LPS-induced increases in albumin flux (p<0.05), leukocyte rolling (p<0.01) and adhesion (p<0.01). Fluid administration did not appear to alter shear rates.

CONCLUSIONS

Pre-emptive volume administration with either saline or albumin prevented early LPS-induced microcirculatory changes by an undefined effect that is unrelated to changes in microvascular flow.

Quantification of lung water by transpulmonary thermodilution in normal and edematous lung

PURPOSE

To analyze the accuracy of the transpulmonary thermodilution method in the determination of extravascular lung water (EVLW).

MATERIAL AND METHODS

Acute lung injury was produced in eight adolescent pigs weighing 28 to 35 kg by bronchoalveolar lung lavage. EVLW was measured by transpulmonary thermodilution method before and after the intratracheal introduction of 250 or 500 mL of saline solution in different lung injury conditions. No corrections for anatomic dead space were made.

RESULTS

When 250 mL was introduced, 195 +/- 17 mL was detected in normal (uninjured) lungs versus 74 +/- 57 mL in edematous (injured) lungs (P <.05). When 500 mL was introduced, 343 +/- 67 mL was detected in normal lungs versus 160 +/- 51 mL in edematous lungs (P <.001). Considering all determinations together, there was a very high negative correlation between the baseline EVLW and the percentage of EVLW detected (r = -0.92, P <.001).

CONCLUSION

The transpulmonary thermodilution method is very accurate to detect changes in EVLW in normal lungs. In edematous lung, this method may underestimate the EVLW.

Understanding and managing fluid balance in patients with acute lung injury

PURPOSE OF REVIEW

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) affect hundreds of thousands of people each year worldwide, resulting in a significant healthcare burden. Over the past four decades, much has been discovered regarding the pathophysiology of lung injury, yet little progress has been made in advancing effective treatment strategies. In this article, we discuss the current knowledge as to fluid balance in the pathophysiology of ALI/ARDS and the recent innovations that have been described related to manipulations of hydrostatic or oncotic pressure in this condition.

RECENT FINDINGS

Hypoproteinemia is a clear marker for ALI/ARDS and may play a pathophysiologic role given its independent prognostic value. Fluid balance and oncotic pressure alterations induced by diuretic and colloid therapy improve respiratory physiology and likely alter net flux of fluid across the injured capillary-alveolar membrane. Chest radiographs serve as a useful adjunctive tool in monitoring longitudinal fluid balance manipulations in ALI/ARDS.

SUMMARY

Manipulation of Starling forces in established ALI/ARDS produces significant physiologic benefit and may influence outcome. Future research should focus on determining a mortality benefit with this readily available intervention.

SARS in the Intensive Care Unit

Approximately 20% of patients with severe acute respiratory syndrome (SARS) develop respiratory failure that requires admission to an intensive care unit (ICU). Old age, comorbidity, and elevated lactate dehydrogenase on hospital admission are associated with increased risk for ICU admission. ICU admission usually is late and occurs 8 to 10 days after symptom onset. Acute respiratory distress syndrome occurs in almost all admitted patients and most require mechanical ventilation. ICU admission is associated with significant morbidity, particularly an apparent increase in the incidence of barotrauma and nosocomial sepsis. Long-term mortality for patients admitted to the ICU ranges from 30% to 50%. Many procedures in ICUs pose a high risk for transmission of SARS coronavirus to health care workers. Contact and airborne infection isolation precautions, in addition to standard precautions, should be applied when caring for patients with SARS. Ensuring staff safety is important to maintain staff morale and delivery of adequate services.

Iced versus room temperature injectate for assessment of cardiac output, intrathoracic blood volume, and extravascular lung water by single transpulmonary thermodilution

PURPOSE

To assess the accuracy of iced versus room (RT) temperature single transpulmonary thermodilution (STPD) measurements for cardiac output, intra-thoracic blood, volume and extravascular lung water.

MATERIALS AND METHODS

We studied 15 critically ill patients in a surgical intensive care unit with sepsis/septic shock (n = 8), pancreatitis (n = 2), acute liver failure (n = 2), orthotopic liver transplantation (n = 2) and lung resection (n = 1). All patients were sedated and mechanically ventilated. A 4-French femoral arterial catheter was inserted into each patient and connected to the pulse contour computer system (PiCCO). The pulse contour computer was then consecutively calibrated by triplicate STPD with 20 mL of RT and iced saline solution. The measurements with RT injectate were performed with a special in-line sensor adapted for measurement with RT injectate. All measurements were completed in less than 10 min.

RESULTS

A total of 144 measurements were carried out. Linear regression analysis revealed good correlation between the two methods [r = 0.95; r = 0.91 and r = 0.97 for iced v RT cardiac index (CI), intrathoracic blood volume index (ITBVI) and extravascular lung water index (ELWI) respectively]. The bias +/- 2 * standard deviation of difference was -0.2 +/- 0.7 L/min/m2 for CIIT v CIRT; -4,9 +/- 194 mL/m2 for ITBVIIT v ITBVIRT and -0.535 +/- 1,5 mL/kg for ELWIIT v ELWIRT. CIRT and ELWIRT were measured slightly higher compared to IT injectate (P <.05).

CONCLUSIONS

CI, ITBVI, and ELWI assessed by STPD with RT injectate are well correlated with measurements by iced injectates. According to our results room temperature injectates can be used in critically ill patients for assessment of CI, ITBVI and ELWI, which is more convenient for both the patients and medical staff and is also less expensive.

Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

INTRODUCTION

There is no consensus definition of acute renal failure (ARF) in critically ill patients. More than 30 different definitions have been used in the literature, creating much confusion and making comparisons difficult. Similarly, strong debate exists on the validity and clinical relevance of animal models of ARF; on choices of fluid management and of end-points for trials of new interventions in this field; and on how information technology can be used to assist this process. Accordingly, we sought to review the available evidence, make recommendations and delineate key questions for future studies.

METHODS

We undertook a systematic review of the literature using Medline and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated recommendations and/or directions for future research.

RESULTS

We found sufficient consensus on 47 questions to allow the development of recommendations. Importantly, we were able to develop a consensus definition for ARF. In some cases it was also possible to issue useful consensus recommendations for future investigations. We present a summary of the findings. (Full versions of the six workgroups' findings are available on the internet at http://www.ADQI.net)

CONCLUSION

Despite limited data, broad areas of consensus exist for the physiological and clinical principles needed to guide the development of consensus recommendations for defining ARF, selection of animal models, methods of monitoring fluid therapy, choice of physiological and clinical end-points for trials, and the possible role of information technology.

Fluid resuscitation with colloids of different molecular weight in septic shock

OBJECTIVE

The aim of this study was to investigate the short-term effect of fluid resuscitation with 4% modified fluid gelatine (GEL) versus 6% hydroxyethyl starch (HES) on haemodynamics and oxygenation in patients with septic shock and acute lung injury (ALI).

DESIGN

Prospective randomised clinical trial.

SETTING

Twenty-bed intensive care unit in a university hospital.

PATIENTS

Thirty hypovolemic patients (intrathoracic blood volume index, ITBVI <850 ml/m(2)) in septic shock with ALI were randomised into HES (mean molecular weight: 200,000 Dalton, degree of substitution 0.6) and GEL (mean molecular weight: 30,000 Dalton) groups (15 patients each).

INTERVENTIONS

For fluid resuscitation 250 ml/15 min boluses (max. 1,000 ml) were given until the end point of ITBVI >900 ml/m(2) was reached. Repeated haemodynamic measurements were done at baseline (t(b)), at the end point (t(ep)) then at 30 min and 60 min after the end point was reached (t(30), t(60)). Cardiac output, stroke volume, extravascular lung water (EVLW), and oxygen delivery was determined at each assessment point. For statistical analysis two-way ANOVA was used.

MEASUREMENTS AND RESULTS

ITBVI, cardiac index, and oxygen delivery index increased significantly at t(ep) and remained elevated for t(30) and t(60), but there was no significant difference between the two groups. The increase in the ITBVI by 100 ml of infusion was similar in both groups (HES: 26+/-19 ml/m(2) vs GEL: 30+/-19 ml/m(2)). EVLW, remained unchanged, and there was no significant difference between the groups (HES, t(b): 8+/-6, t(60): 8+/-6; GEL, t(b): 8+/-3, t(60): 8+/-3 ml/kg). The PaO(2)/FiO(2) did not change significantly over time or between groups (HES, t(b): 207+/-114, t(60): 189+/-78; GEL, t(b): 182+/-85, t(60): 182+/-85 mmHg).

CONCLUSION

The results of this study indicate that both HES and GEL infusions caused similar short-term change in ITBVI in septic shock, without increasing EVLW or worsening oxygenation.

Acute respiratory distress syndrome

Several combination therapies have been described throughout this article: in all likelihood, it is combination therapy that will allow improved survival of ARDS patients. As medicine moves into the future, clinical trials evaluating the efficacy of therapies for ARDS will be performed. In human critical care medicine, a large forward step was taken when ALI and ARDS were clearly defined. Unfortunately. as good as the definition is, ALI and ARDS occur secondary to many different underlying pathologic processes,perhaps obscuring the benefits of certain therapies for ARDS based on the underlying condition, for example, trauma versus sepsis. Selection of patients entering any ARDS trial is crucial: not only must those patients meet the strict definition of ARDS but the underlying disease process should be clearly identified. Identification of patients suffering from different disease processes before the onset of ARDS will allow for stratification of outcomes according to the intervention and the underlying pathology--comparing apples to apples and not to oranges. We are in a unique position in veterinary medicine. Although frequently financially limited by our clients, we have the opportunity to achieve several goals. First, we need to clearly define what constitutes ALI and ARDS in veterinary medicine. Do we want to rely on the human definitions? Probably not; however, as a group, we need to determine what we will accept as definitions. For example, we may not be able perform right heart catheterizations on all our patients to meet the wedge pressure requirement of human beings of less than 18 mm Hg. Do we agree that a PAOP of less than 18 mmHg is appropriate for animals, and is it appropriate for all animals? Will we accept another measure, for example, pulmonary artery diameter increases with echocardiographic evidence of acceptable left heart function? What is acceptable left heart function? As veterinarians, what do we consider to be hypoxemia? Is it the same in all species that we work with? What do we define as acute onset? Most human ARDS cases occur while patients are in hospital being treated for other problems, whereas many of our patients present already in respiratory distress. If we are unable to ventilate patients for economic or practical reasons, what do we use as the equivalent of the Pao2/Flo, ratio'? Reliance on the pathologist is not reasonable, because many disease processes can look similar to ARDS under the microscope. If anything, ALI and ARDS are clinical diagnoses. It is time for veterinarians to reach a consensus on the definition for ALI and ARDS in our patients. Only when we have a consensus of definition can rational prospective clinical trials of therapies be designed.

Management of post traumatic respiratory failure

Acute respiratory distress syndrome (ARDS) is a severe and common complication of major trauma. The most important early management principle is to identify the inciting event and remove the ongoing insult aggressively. It is important to immediately resuscitate the patients and prepare them for a complex and difficult hospitalization. Avoiding secondary insults is the cornerstone of supportive care, and this is based primarily on aggressive immune surveillance, full nutrition, and unrelenting oxygen delivery. The use of aggressive immune surveillance, nutritional support, and fluid management is critical to support ventilator management for oxygenation and ventilation. In general, although essential, the ventilator has great potential for harm in patients who are compromised seriously with ARDS. Physicians must establish reasonable therapeutic goals based on oxygen delivery rather than arbitrary normal values of blood gas measurement. The impact of the ventilator should be limited with regard to aspiratory pressure, tidal volume, inspired oxygen, and levels of expiratory end expiratory pressure. Use of pulmonary toilet, including therapeutic bronchoscopy; patient positioning, including intermittent prone positioning, and recruitment maneuvers are useful therapeutic complements for maintaining functional residual capacity and decreasing shunt. Overall, ARDS represents a clear indication that the patient is failing to meet the demands of their stress and without prompt attention likely will die. It is a challenge and an opportunity to identify the underlying situation and to manage the patient while not causing additional harm as the patient's intrinsic resources can bring about the healing necessary to recover from the situation of extremis.

Accuracy of the double indicator method for measurement of extravascular lung water depends on the type of acute lung injury*

OBJECTIVE

The double indicator method is sensitive to alterations in the distribution of pulmonary blood flow. This distribution is influenced by the type of lung injury. The aim of this study was to compare measurements of lung water by the double indicator method with measurements obtained by gravimetry in a direct lung injury model induced by tracheal instillation of hydrochloric acid and in an indirect lung injury model induced by the intravenous injection of oleic acid.

DESIGN

Prospective, randomized laboratory study.

SETTING

Animal research laboratory.

SUBJECTS

Forty-two female pigs (28+/-3 kg).

INTERVENTIONS

Pigs were anesthetized and ventilated and were allocated into three groups: control (n = 6), hydrochloric acid (4 mL/kg intratracheally, n = 24), or oleic acid (0.1 mL/kg intravenously, n = 12).

MEASUREMENTS AND MAIN RESULTS

Hydrochloric acid instillation or oleic acid injection resulted in a similar hypoxemia and induced a two- to three-fold increase in extravascular lung water (EVLW) by gravimetry (EVLWG) at 3 hrs compared with controls. In the oleic acid group, there was a significant correlation between EVLWG and EVLW by double indicator method (EVLWDI; r =.88, p <.0001). The bias for EVLWDI - EVLWG measurements was -5.2 mL/kg (95% confidence interval, -5.7 to -4.7 mL/kg) with 95% limits of agreement of -7 to -3.4 mL/kg. In the hydrochloric acid group, there was no significant correlation between EVLWDI and EVLWG values, and the double indicator method failed to detect pulmonary edema in 65% of the animals (EVLWDI <8 mL/kg). The bias was -7.9 mL/kg (95% confidence interval, -9.3 to -6.5 mL/kg) with 95% limits of agreement of -14.4 to -1.4 mL/kg.

CONCLUSIONS

The double indicator method is useful for evaluation of pulmonary edema in indirect lung injury, as induced by oleic acid, but produces misleading values in direct lung injury, as produced by hydrochloric instillation.

Assessment of cardiac preload and left ventricular function under increasing levels of positive end-expiratory pressure

OBJECTIVE

(1) To assess the impact of high intrathoracic pressure on left ventricular volume and function. (2) To test the hypothesis that right ventricular end-diastolic volume (RVEDV) and intrathoracic blood volume (ITBV) represent cardiac preload and are superior to central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP). The validity of these parameters was tested by means of correlation with left ventricular end-diastolic volume (LVEDV), the true cardiac preload.

DESIGN

Prospective animal study.

SUBJECTS

Fifteen adult sheep.

INTERVENTIONS

All animals were studied before and after saline washout-induced lung injury, undergoing volume-controlled ventilation with increasing levels of PEEP (0, 7, 14 and 21 cmH2O, respectively).

MEASUREMENTS AND MAIN RESULTS

Left ventricular ejection fraction (LVEF), stroke volume (LVSV) and LVEDV were measured using computed tomography. ITBV and RVEDV were obtained by the thermal dye dilution technique. At PEEP 21 cmH2O, LVSV significantly decreased compared to baseline, PEEP 0 and PEEP 7 cmH2O. LVEDV was maintained except for the highest level of PEEP, while LVEF remained unchanged. RVEDV and RVEF also remained unchanged. The overall correlation of RVEDV and ITBV with LVEDV was satisfactory ( r=0.56 and r=0.62, respectively) and clearly superior to cardiac filling pressures.

CONCLUSION

In the present study, (1) ventilation with increasing levels of PEEP did not alter RV function, while LV function was impaired at the highest level of PEEP; (2) unlike cardiac filling pressures, ITBV and RVEDV both provide valid estimates of cardiac preload even at high intrathoracic pressures.

Fluid and electrolytes in the elderly

PURPOSE OF REVIEW

The intake of water and electrolytes is inseparable from the ingestion of nutrients by normal or artificial means. Recent reports have agreed in criticizing the poor standards of practice and of training in the management of fluid and electrolyte balance, resulting in a large amount of avoidable morbidity, particularly in the elderly who are more vulnerable to fluctuations in body composition.

RECENT FINDINGS

Ageing is associated with impaired physiological reserve and a reduced ability to compensate for fluctuations in environmental conditions. These changes include reduced cardiac and renal reserve, making the elderly more vulnerable to changes in water and electrolyte gain or loss with a resulting increase in morbidity and mortality. The ability to cope with errors in prescriptions is correspondingly diminished. Dehydration is a common problem in nursing homes and in the community, due often to failures in detection and appropriate management. In many cases, the cause is iatrogenic due to diuretics or drugs which impair the intake of food and fluid. Salt and water overload, particularly in hospital patients, is also common and results in impaired recovery from surgery and increased perioperative mortality and morbidity. Hyponatraemia is also an important clinical problem in hospital and the community.

SUMMARY

Better training in the detection, prevention and management of fluid and electrolyte imbalance is needed to reduce common and serious morbidity associated with this problem to which the elderly are especially prone, owing to their diminished physiological reserves and increased comorbidity.

Comparison of Hemodynamic and Biochemical Effects of Furosemide by Continuous Infusion and Intermittent Bolus in Critically Ill Patients

Positive fluid balance in critically ill patients is a common problem in the intensive care unit (ICU) often associated with a poor outcome. In addition, clinically important changes in hemodynamic variables have been found to occur after diuretic therapy. This study was conducted to evaluate the safety and relative effectiveness of two diuretic protocols in the ICU. Twenty-two patients in the medical ICU with pulmonary edema or fluid overload and PaO2/FIO2 pressure less than 300, were randomized to diuretic therapy by either continuous infusion or intermittent bolus. Hemodynamic and biochemical measurements were recorded. Protocol-guided diuretic management can be readily and safely implemented in the ICU. Although both continuous and bolus diuretic regimens appear to be equally effective in achieving negative fluid balance, the clinician may consider a continuous infusion of furosemide in the hemodynamically and electrolytically unstable patient to ensure more controlled diuresis with less hemodynamic and electrolyte alteration. From a nursing perspective, a continuous infusion of furosemide is a more efficient means of drug delivery.

Haemodynamic monitoring with pulse-induced contour cardiac output (PiCCO) in critical care

Haemodynamic monitoring is essential for the management of the critically ill. Effective monitoring can give data that permit analysis of key circulatory functions and the anticipation of deterioration so that pro-active treatments can be initiated. There are many methods of monitoring the haemodynamic status of patients. The authors have compared three of the most commonly used methods in the general Critical Care Unit. These are the pulmonary artery catheter (PAC), oesophageal Doppler, and pulse-induced contour cardiac output (PiCCO) studies. The focus is upon PiCCO, which is a comparatively less invasive method than the traditionally used PAC. This has been chosen due to the authors' particular interest in the additional parameters which can be monitored using PiCCO. With the PiCCO system it is possible to measure intrathoracic blood volume (ITBV), extravascular lung water (EVLW) and cardiac function index (CFI). These parameters are of interest as they are considered to be the most specific measures of cardiac preload, pulmonary oedema and contractility and a global indicator of cardiac performance.

PEEP decreases atelectasis and extravascular lung water but not lung tissue volume in surfactant-washout lung injury

OBJECTIVE

To examine the effects of positive end-expiratory pressure (PEEP) on extravascular lung water (EVLW), lung tissue, and lung volume.

DESIGN AND SETTING

Experimental animal study at a university research facility.

SUBJECTS

Fifteen adult sheep.

INTERVENTIONS

All animals were studied before and after saline washout-induced lung injury while ventilated with sequentially increasing PEEP (0, 7, 14, or 21 cmH(2)O).

MEASUREMENTS AND RESULTS

Lung volume was determined by computed tomography and EVLW by the thermal dye dilution technique. Saline washout significantly increased lung tissue volume (21+/-3 to 37+/-5 ml/kg) and EVLW (9+/-2 to 36+/-9 ml/kg). While increasing levels of PEEP reduced EVLW (30+/-7, 24+/-8, and 18+/-4 ml/kg), lung tissue volume remained constant. Total lung volume significantly increased (50+/-8 ml/kg at PEEP 0 to 77+/-12 ml/kg at PEEP 21). Nonaerated lung volume significantly decreased and was closely correlated with the changes in EVLW ( r=0.67). In addition, a highly significant correlation was found between PEEP-induced decrease in nonaerated lung volume and decrease in transpulmonary shunt ( r=0.83).

CONCLUSIONS

The main findings are as follows: (a) PEEP effectively decreases EVLW. (b) The decrease in EVLW is closely correlated with the PEEP-induced decrease in nonaerated lung volume, making EVLW a valuable bedside parameter indicating alveolar recruitment, similar to measurements of transpulmonary shunt. (c) As excess tissue volume remained constant, however, EVLW may not be suitable to reflect overall severity of lung disease

Acute lung injury and the acute respiratory distress syndrome

Although ALI/ARDS mortality rates have improved over the last several decades, they remain high, particularly in the geriatric patient population. Although considerable progress has been made in understanding the pathogenesis of the disease, a large number of promising treatments have proven unsuccessful. One exception has been in the area of ventilator management, where a strategy of protective ventilation with low tidal volumes has demonstrated a significant mortality benefit. Basic research continues to help advance our understanding of this complex syndrome and identify interesting new directions of investigation. The results of several large, randomized trials of new ventilatory and pharmacologic strategies currently underway may help identify successful methods of treating this important disease.

Approach to intradialytic hypotension in intensive care unit patients with acute renal failure

The increasing prevalence of acute renal failure (ARF) patients with hemodynamic intolerance of intermittent hemodialysis (HD), generally because of septic vasoparesis or severe cardiac dysfunction, has led to the development of several strategies to improve the delivery of renal replacement therapy (RRT) in ARF patients. Intradialytic hypotension (IDH) is caused by the interaction of dialysis-dependent and dialysis-independent factors. Dialysis-dependent factors include the prescriptions for fluid removal, solute removal, and dialysate components such as sodium, buffer, and calcium. Dialysis-independent factors include hemodynamic compromise caused by hypovolemic, cardiogenic, vasodilatory, and mixed mechanisms. We propose an approach to the prevention and management of IDH in critically ill ARF patients, which minimizes hypovolemic, cardiogenic, and vasodilatory insults by optimizing fluid removal, cardiac function, and vascular contractility.

Prone position in subarachnoid hemorrhage patients with acute respiratory distress syndrome: effects on cerebral tissue oxygenation and intracranial pressure

OBJECTIVE

To analyze the effect of prone position on cerebral perfusion pressure and brain tissue oxygen partial pressure in subarachnoid hemorrhage patients with acute respiratory distress syndrome (ARDS).

DESIGN

Clinical study with retrospective data analysis.

SETTING

Neurosurgical intensive care unit of a primary level university hospital.

PATIENTS

Sixteen patients treated for intracranial aneurysm rupture with initial Hunt and Hess grade III or worse who developed ARDS within 2 wks after the bleeding.

INTERVENTIONS

Routine neurosurgical intensive care treatment for subarachnoid hemorrhage and posthemorrhagic vasospasm including cerebral monitoring with continuous intracranial pressure and brain tissue oxygen partial pressure recordings.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, arterial oxygenation, ventilatory setting, intracranial pressure, cerebral perfusion pressure, and brain tissue oxygen partial pressure in the supine as well as in the prone position were analyzed and compared. A significant increase in Pao(2) from 97.3 +/- 20.7 torr (mean +/- sd) in the supine position to 126.6 +/- 31.7 torr in the prone position was joined by a significant increase in brain tissue oxygen partial pressure from 26.8 +/- 10.9 torr to 31.6 +/- 12.2 torr (both p <.0001), whereas intracranial pressure increased from 9.3 +/- 5.2 mm Hg to 14.8 +/- 6.7 mm Hg and cerebral perfusion pressure decreased from 73.0 +/- 10.5 mm Hg to 67.7 +/- 10.7 mm Hg (both p <.0001).

CONCLUSIONS

The beneficial effect of prone positioning on cerebral tissue oxygenation by increasing arterial oxygenation appears to outweigh the expected adverse effect of prone positioning on cerebral tissue oxygenation by decreasing cerebral perfusion pressure in ARDS patients.

Effects of albumin and Ringer's lactate on production of lung cytokines and hydrogen peroxide after resuscitated hemorrhage and endotoxemia in rats

RATIONALE AND HYPOTHESIS

Acute lung injury is a frequent complication of severe sepsis or blood loss and is often associated with an excessive inflammatory response requiring mechanical ventilation. We tested the hypothesis that the types of fluids used during early resuscitation have an important effect on the evolution of lung injury.

METHODS

Rats were subjected to either hemorrhage or endotoxemia for 1 hr, followed by resuscitation to a controlled mean blood pressure with Ringer's lactate, 5% albumin, or 25% albumin for 1 hr. After resuscitation, blood cytokine levels were measured. The lung was then excised and ventilated with a tidal volume of 30 mL/kg for 2 hrs.

RESULTS

The volume of fluids required was significantly smaller in the albumin-treated groups than in the Ringer's lactate groups. In the hemorrhagic shock model, plasma concentrations of tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2 were significantly lower and interleukin-10 was significantly higher in the albumin-treated groups compared with the Ringer's lactate-treated group. The levels of tumor necrosis factor-alpha and macrophage inflammatory protein-2 in bronchoalveolar lavage fluid were lower and interleukin-10 was higher in the albumin-treated groups than in the Ringer's lactate group. The decreased cytokine production was associated with a reduction of hydrogen peroxide formation with albumin resuscitation. The lung wet/dry ratio was lower in the 5% albumin (0.54 +/- 0.01) and 25% albumin (0.55 +/- 0.02) groups than in the Ringer's lactate group (0.62 +/- 0.02; both p <.05). These effects of albumin seen in the hemorrhagic shock model were not observed in the endotoxic shock model.

CONCLUSIONS

We conclude that resuscitation with albumin may have utility in reducing ventilator-induced lung injury after hemorrhagic shock, but not after endotoxic shock. These findings suggest that the mechanisms leading to ventilator-induced lung injury after hemorrhage differ from those after endotoxemia.

Techniques for assessing and achieving fluid balance in acute renal failure

Fluid therapy, together with attention to oxygen supply, is the cornerstone of resuscitation in all critically ill patients. Hypovolemia results in inadequate blood flow to meet the metabolic requirements of the tissues and must be treated urgently to avoid the complication of progressive organ failure, including acute renal failure. The kidney plays a critical role in body fluid homeostasis. Renal dysfunction disturbs this homeostasis and requires special attention to issues of fluid balance and fluid overload. In addition, fluid therapy is the only treatment that has been shown to be effective in the prevention of acute renal failure. Special attention to volume status is therefore required in patients at risk for acute renal failure. Hypovolemia is also a major causal factor of morbidity during hemodialysis and may contribute to further renal insults. Although the importance of fluid management is generally recognized, the choice of fluid, the amount, and assessment of fluid status are controversial. As the choice of fluids becomes wider and monitoring devices become more sophisticated, the controversy increases. This article provides an overview of the concept of fluid management in the critically ill patient with acute renal failure.

Prognostic value of extravascular lung water in critically ill patients

OBJECTIVE

Measurement of extravascular lung water (EVLW) as a clinical tool for the assessment of pulmonary function has been found to be more appropriate than oxygenation parameters or radiographic techniques. In this study, we analyzed the prognostic value of EVLW in critically ill patients.

DESIGN

Retrospective analysis.

SETTING

Operative ICU of a university hospital.

MEASUREMENTS AND RESULTS

We retrospectively analyzed 373 critically ill patients (133 female and 240 male patients; age range, 10 to 89 years; mean +/- SD age, 53 +/- 19 years) who were treated in our ICU between 1996 and 2000. All these patients were hemodynamically monitored by the transpulmonary double-indicator (thermo-dye) dilution technique. Each patient received a femoral artery sheath through which a 4F flexible catheter with an integrated thermistor and fiberoptic was advanced into the infradiaphragmatic aorta. EVLW was calculated using a computer system. For each measurement, 15 to 17 mL of cooled 2% indocyanine green were injected central venously. In our results, maximum EVLW was significantly higher in nonsurvivors (n = 186) than in survivors (n = 187) [median, 14.3 mL/kg vs 10.2 mL/kg, respectively; p < 0.001]. In univariate logistic regression models, EVLW (r(2) = 0.024, p = 0.003) at baseline as well as simplified acute physiology score (SAPS) II (r(2) = 0.135, p < 0.0001) and APACHE (acute physiology and chronic health evaluation) II scores (r(2) = 0.050, p < 0.0001) were significant predictors of mortality. If SAPS II and APACHE II scores are combined, r(2) increases to 0.136, but the improvement over SAPS II alone is not significant. The addition of baseline EVLW further increases r(2) to 0.149 (p = 0.021 for the improvement), indicating that EVLW contributes independently to prognosis.

CONCLUSION

EVLW correlated well with survival (ie, nonsurvivors had significantly higher EVLW values than survivors) and is an independent predictor of prognosis.

Findings on the portable chest radiograph correlate with fluid balance in critically ill patients

STUDY OBJECTIVES

Fluid balance concerns occur daily in critically ill patients, complicated by difficulties assessing intravascular volume. Chest radiographs (CXRs) quantify pulmonary edema in acute lung injury (ALI) and total blood volume in normal subjects. We hypothesized that CXRs would reflect temporal changes in fluid balance in critically ill patients.

DESIGN

Standardized scoring of 133 supine, portable, anteroposterior CXRs. Outcomes included subjective and objective measures of intravascular volume and pulmonary edema.

SETTING

Academic university medical center and affiliated Veterans Affairs hospital.

PATIENTS

Thirty-seven patients with ALI receiving mechanical ventilation blindly randomized to treatment with diuretics and colloids or dual placebo for 5 days.

MEASUREMENTS AND RESULTS

Treated patients experienced a 3.3-L diuresis and 10-kg weight loss during the 5-day period. A significant correlation was observed in all patients between changes in vascular pedicle width (VPW) and net intake/output (r = 0.50, p = 0.01) or weight (r = 0.51, p = 0.01). The correlation between VPW and fluid balance was greatest for weight changes in the treatment group alone (r = 0.71, p = 0.005). Pulmonary artery occlusion pressure correlated highly with changes in VPW (r = 0.70, p < 0.001). After day 1, CXRs revealed significant between-group differences in VPW without changes in cardiothoracic ratio or subjective measures of edema. The proportion of patients with VPW < 70 mm did not differ at baseline but was significantly more in the treatment group on all subsequent days (p < 0.05).

CONCLUSIONS

We conclude that temporal fluid balance changes are reflected on commonly utilized portable CXRs. Objective radiographic measures of intravascular volume may be more appropriate indicators of fluid balance than subjective measures, with VPW appearing most sensitive. If systematically quantitated, serial CXRs provide a substantial supplement to other clinically available data for the purpose of fluid management in critically ill patients.

Vascular pharmacology of acute lung injury and acute respiratory distress syndrome

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) following sepsis, major trauma and surgery are leading causes of respiratory insufficiency, warranting artificial ventilation in the intensive care unit. It is caused by an inflammatory reaction in the lung upon exogenous or endogenous etiologies eliciting proinflammatory factors, and results in increased alveolocapillary permeability and protein-rich alveolar edema. The interstitial and alveolar inflammation and edema alter ventilation perfusion matching, gas exchange and mechanical properties of the lung. The current therapy of the condition is supportive, paying careful attention to fluid balance, relieving the increased work of breathing and improving gas exchange by mechanical ventilation, but in vitro, animal and some clinical research is done to evaluate the value of anti-inflammatory therapies on morbidity and outcome, including inflammatory cell-stabilizing corticosteroids, xanthine derivates, prostanoids and inhibitors, O(2) radical scavenging factors such as N-acetylcysteine, surfactant replacement, vasodilators including inhaled nitric oxide, vasoconstrictors such as almitrine, and others. None of these compounds has been proven to benefit survival in patients, however, even though carrying a physiologic benefit, except perhaps for steroids that may improve outcome in the later stage of ARDS. This partly relates to the difficulty to assess the lung injury at the bedside, to the multifactorial pathogenesis and the severity of comorbidity, adversely affecting survival.

The first international consensus conference on continuous renal replacement therapy

BACKGROUND

Management of acute renal failure (ARF) in the critically ill is extremely variable and there are no published standards for the provision of renal replacement therapy in this population. We sought to review the available evidence, make evidence-based practice recommendations, and delineate key questions for future study.

METHODS

We undertook an evidence-based review of the literature on continuous renal replacement therapy (CRRT) using MEDLINE searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated practice guidelines and/or directions for future research.

RESULTS

Of the 46 questions considered, we found consensus for 20. We found inadequate evidence for 21 questions and for the remaining five we found data but no consensus. Full versions of workgroup findings are available on the Internet at http://www.ADQI.net.

CONCLUSIONS

Despite limited data, broad areas of consensus exist for use of CRRT and guideline development appears feasible. Equally broad areas of disagreement also exist and additional basic and applied research in acute renal failure is needed.

Minimally invasive hemodynamic monitoring for the intensivist: current and emerging technology

OBJECTIVE

To review minimally invasive cardiac output monitoring devices currently available for use in the intensive care unit.

DATA SOURCES

Medline search from 1966 to present plus cited reference studies and abstracts from available product literature.

STUDY SELECTION

Selection criteria included published reports and abstracts comparing the accuracy of minimally invasive cardiac output monitors to a "gold standard."

DATA SYNTHESIS

Many reports have been published on the accuracy of individual minimally invasive cardiac output monitors, but cumulative data reviewing each type of monitor have not been synthesized and made available to the clinician.

CONCLUSIONS

Emerging noninvasive or minimally invasive means of cardiac output monitoring are based on varied physiologic principles and can be used for following hemodynamic trends. Each of these methods has advantages and disadvantages; it is important for the clinician to understand the strengths and limitations of each device to effectively use the information derived.

Impact of low pulmonary vascular pressure on ventilator-induced lung injury

OBJECTIVE

To study the impact of low pulmonary vascular pressure on ventilator-induced lung injury.

DESIGN

Randomized prospective animal study.

SUBJECTS

Isolated perfused rabbit heart-lung preparation.

SETTINGS

Animal research laboratory in a university hospital.

INTERVENTIONS

Twenty isolated sets of normal lungs were perfused (constant flow, 0.3 L/min; left atrial pressure, 6 mm Hg), ventilated for 20 min (pressure control ventilation, 15 cm H2O; baseline period), and then randomized into three groups. Group A (control, n = 7) was perfused and ventilated as previously described during three consecutive 20-min periods. In group B (high airway pressure/normal left atrial pressure, n = 7), pressure control ventilation was 20, 25, and 30 cm H2O during each period. Group C (high airway pressure/low left atrial pressure, n = 6) was ventilated as group B but, in contrast to groups A and B, left atrial pressure was reduced to 1 mm Hg.

MEASUREMENTS AND MAIN RESULTS

The rate of edema formation (WGR, weight gain per minute normalized for initial lung weight) and the ultrafiltration coefficient (Kf) were measured during and after each period and their changes from baseline [DeltaWGR (edema formation index) and DeltaKf (vascular permeability index)] calculated to compare groups. The incidence and timing of vascular failure were compared. Vascular failure was considered to be present if all the following conditions were met: pulmonary hypertension, accelerated weight gain, and occurrence of fluid leak from the lungs. At the end of the study, DeltaWGR (g.g.min(-1)) was higher in group C (0.54 +/- 0.17) than in groups B (0.08 +/- 0.04) and A (0.00 +/- 0.01; p<.05), as well as in group B compared with A (p <.05). Similar differences between groups (p <.05) were found for DeltaK (g x min(-1) x cm H2O(-1) x 100 g(-1)): C, 7.24 +/- 2.36; B, 1.40 +/- 0.49; A, 0.01 +/- 0.03. Vascular failure was not observed in groups A and B but occurred in all but one preparation in group C (p <.05; C vs. A and B).

CONCLUSION

Reducing left atrial pressure results in more severe ventilator-induced lung injury. These results suggest that lung blood volume modulates cyclic tidal lung stress.

The Acute Dialysis Quality Initiative--part VII: fluid composition and management in CRRT

Fluid composition and management are important parts of continuous renal replacement therapy (CRRT). Most commercially available CRRT solutions are able to reestablish electrolyte homeostasis provided some phosphate supplementation is given. Supraphysiologic glucose concentrations should be avoided. Predilution fluid replacement allows higher ultrafiltration rates and can be considered as an adjunct to the anticoagulation regimen. Lactate is an effective buffer in most CRRT patients. Bicarbonate is preferred in patients with lactic acidosis and/or liver failure. When citrate is used as anticoagulant, frequent monitoring of pH is required. The clinical consequences of CRRT-induced decreases of body temperature are not clear. Substitution fluid should be sterile, but the bacteriologic requirements for CRRT dialysate are less clear. There is no consensus on the optimal parameters to monitor fluid management. Integrated balancing systems have theoretical advantages over adaptive use of intravenous fluid pumps. Although there is evidence that volume overload is associated with adverse outcome, there is no evidence that fluid removal per se improves outcome in critically ill patients with or without acute renal failure.

Albumin and furosemide therapy in hypoproteinemic patients with acute lung injury

OBJECTIVE

Hypoproteinemia, fluid retention, and weight gain are associated with development of acute lung injury and mortality in critically ill patients, without proof of cause and effect. We designed a clinical trial to determine whether diuresis and colloid replacement in hypoproteinemic patients with acute lung injury would improve pulmonary physiology.

DESIGN

Prospective, randomized, double-blind, placebo-controlled trial.

SETTING

All adult intensive care units from two university hospitals.

PATIENTS

Thirty-seven mechanically-ventilated patients with acute lung injury and serum total protein </=5.0 g/dL.

INTERVENTIONS

Five-day protocolized regimen of 25 g of human serum albumin every 8 hrs with continuous infusion furosemide, or dual placebo, targeted to diuresis, weight loss, and serum total protein.

MEASUREMENTS AND MAIN RESULTS

Measured outcomes included change in weight, serum total protein, fluid balance, hemodynamics, respiratory system compliance, and oxygenation. Baseline characteristics were similar between groups (treatment, n = 19; control, n = 18), with trauma being the major cause of acute lung injury. Diuresis and weight loss over 5 days (5.3 kg more in the treatment group, p =.04) was accompanied by improvements in the Pao2/Fio2 ratio in the treatment group within 24 hrs (from 171 to 236, p =.02). Respiratory mechanics were unchanged. Mean arterial pressure increased from 80 to 88 mm Hg (p =.10), and heart rate decreased from 110 to 95 beats/min (p =.008) over time in the treatment group. No difference in mortality was observed, with favorable trends in measures of intensive care.

CONCLUSIONS

Albumin and furosemide therapy improves fluid balance, oxygenation, and hemodynamics in hypoproteinemic patients with acute lung injury. Determining the effect of this simple therapy on cost, outcomes, and other patient populations requires further study.

The pulmonary physician in critical care - part 9: non-ventilatory strategies in ARDS

Pharmacological approaches to the treatment of ARDS are reviewed. Future treatments should be targeted at elements of the pathological process that produce specific clinical problems.

Pharmacology of acute lung injury

The acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a clinical syndrome that affects both medical and surgical patients. To date, despite improved understanding of the pathogenesis of ALI/ARDS, pharmacological modalities have been unsuccessful in decreasing mortality. However, several pharmacological agents for ARDS are in development and have shown great promise. In addition to the anti-inflammatory category including late corticosteroids, inhaled nitric oxide, alveolar surfactant, and vasodilators are being evaluated. Replacements of anticoagulation mediators have also suggested beneficial effects on the patient outcome. This article provides an overview of pharmacological treatments of ALI/ARDS.

Management of the acute respiratory distress syndrome

Significant advances have occurred in the knowledge of the pathogenesis of ARDS. It is now recognized that ARDS is a manifestation of a diffuse process that results from a complicated cascade of events following an initial insult or injury. Mechanical ventilation and PEEP are still important components of supportive therapy. To avoid ventilator-associated lung injury there is emphasis on targeting ventilator management based on measurement of pulmonary mechanics. For those with resistant hypoxia and severe pulmonary hypertension adjunctive modalities, such as prone positioning and low-dose iNO, may provide important benefit. Alternative modes of supporting gas exchange, such as with partial liquid ventilation and extracorporeal gas-exchange, may serve as rescue therapies. Advances in cell and molecular biology have contributed to a better understanding of the role of inflammatory cells and mediators that contribute to the acute lung injury and the pathophysiology of the syndrome that manifests as ARDS. Based on this new understanding, the potential targets for intervention to ameliorate the systemic inflammatory response have proliferated. Examples include the cytokine network and its receptors, antioxidants, and endothelins. Apart from the challenge of testing these agents in experimental models, it seems likely that determination of the optimum combination of agents will become an equally important endeavor. A particular challenge is to develop better methods of predicting which of the many at-risk patients will go on to full-blown ARDS and MODS, thereby targeting subgroups of patients most likely to benefit from anti-inflammatory therapies. Similarly, the adverse effects of immunosuppressive therapy may be diminished by improved, perhaps molecular, techniques to detect microbial pathogens and permit differentiation between Systemic inflammatory response syndrome and sepsis.

Clinical review: hemodynamic monitoring in the intensive care unit

Since the beginning of modern anesthesia, in 1846, the anesthetist has relied on his natural senses to monitor the patient, aided more recently by simple technical devices such as the stethoscope. There has been a tremendous increase in the availability of monitoring devices in the past 30 years. Modern technology has provided a large number of sophisticated monitors and therapeutic instruments, particularly in the past decade. Most of these techniques have enhanced our understanding of the mechanism of the patients' decompensation and have helped to guide appropriate therapeutic interventions. As surgery and critical care medicine have developed rapidly, patient monitoring capability has become increasingly complex. The most important aspect in monitoring the critically ill patient is the detection of life-threatening derangements of vital functions. Aggressive marketing strategies have been promoted to monitor almost every aspect of the patient's status. However, these strategies are only telling us what is possible; they do not tell us whether they enhance patient safety, improve our therapy, or even improve patient outcome.

Pulmonary capillary pressure during acute lung injury in dogs

OBJECTIVES

To measure pulmonary capillary pressure and pulmonary artery occlusion pressures both during control conditions and during acute lung injury and to evaluate the effects of inotropic therapy and volume loading on these measurements after lung injury.

DESIGN

Prospective, randomized, controlled laboratory trial.

SETTING

University research laboratory.

SUBJECTS

Eighteen heartworm-free mongrel dogs.

INTERVENTIONS

Dogs were anesthetized (sodium pentobarbital, 30 mg/kg intravenously), intubated, and mechanically ventilated. A femoral artery and vein and the right external jugular vein were cannulated. After a median sternotomy, two pulmonary artery catheters were inserted via the jugular vein into the left and right lower lobar pulmonary arteries. Oleic acid (0.03 mL/kg) was administered to all dogs via the left pulmonary artery catheter, whereas the right lower lobe served as control. A baseline group of dogs received no further interventions, whereas two additional groups were given dobutamine (30-60 microg x kg(-1) x min(-1)intravenously) or saline boluses (1-2 L) before measurements were obtained after oleic acid lung injury.

MEASUREMENTS AND MAIN RESULTS

Capillary pressure was estimated in both lower lung lobes by using the pulmonary artery occlusion method. Pulmonary capillary and pulmonary artery occlusion pressures were measured before and 2 hrs after oleic acid administration. Left lower lobar capillary pressure increased in all three groups, as did the difference between capillary pressure and pulmonary artery occlusion pressure. Capillary pressure in the control right lower lobe increased significantly only in the saline-loaded dogs, whereas the difference between the right-sided capillary and occlusion pressures increased only in the dogs given dobutamine.

CONCLUSIONS

Oleic acid lung injury increases pulmonary capillary pressure independent of pulmonary artery occlusion pressure. The gradient between the two pressures was not significantly affected by volume loading or dobutamine infusion.

Effects of resuscitation with hydroxyethyl starch (HES) on pulmonary hemodynamics and lung lymph balance in hemorrhagic sheep; comparative study of low and high molecular HES

Synthetic starch solution, such as hydroxyethyl starch (HES), has been used clinically to restore cardiovascular volume in patients with hemorrhagic shock. Several HES solutions are available clinically, but each HES has a broad range of molecular mass fractions. We performed comparative studies of extremely low and high molecular HES to evaluate the effects of these HES solutions on lung lymph filtration during resuscitation. We prepared awake sheep with vascular monitoring and lung lymph fistulas. After baseline measurements, animals were bled from an arterial line to maintain shock. After 2 h of hemorrhagic period, the following three solutions were infused over 1 h, respectively. Experiment (Exp) 1 (n=6); low molecular HES; (molecular weight (MW) 70000, substitution fractions 0.5-0.55, Exp 2 (n=6); high molecular HES; (MW 450000, substitution fractions 0.65). Exp 3 (n=6); normal saline (NS). The quantity of solution was determined as the same volume of blood lost to induce hemorrhagic situation in each animal (Exp 1; 940+/-36 ml, Exp 2; 910+/-50 ml, Exp 3; 920+/-42 ml). Both low and high molecular HES could restore the systemic artery pressure and cardiac output, and significantly increased pulmonary microvascular pressure equally, which were significantly higher than those in normal saline. However, actual oncotic pressure gradient (plasma-lymph) rose transiently during low molecular HES infusion, while high molecular HES widened the oncotic pressure gradient even after the cessation of the infusion. Lung lymph flow during and after resuscitation with low molecular HES and NS rose significantly from the pre-shock baseline. There was no significant difference in increased lung lymph flow between low molecular HES and NS. However, lung lymph flow after high molecular HES was significantly less than that after low molecular HES. These data suggest that low molecular HES is as useful a plasma substitute as high molecular HES, but has a possibility to increase lung lymph filtration during the early phase of resuscitation.

Clinical developments for treating ARDS

Acute respiratory distress syndrome (ARDS), is characterised by capillary permeability and pulmonary oedema formation and may complicate a variety of medical and surgical illnesses. As a self-perpetuating state of inflammatory derangement, acute lung injury (ALI)/ARDS is manifest clinically as rapid development of radiographic infiltrates, severe hypoxaemia and reduced lung compliance. Over the years, researchers have made significant progress in elucidating the pathophysiology of this complex syndrome. Therapies targeting specific pathophysiologic steps in the development or persistence of this syndrome are in various stages of laboratory and clinical testing. Results to date have shown nitric oxide (NO) to improve oxygenation in the majority of patients but fail to improve mortality. Surfactant replacement has had limited success in adults, but new formulations and delivery methods may prove beneficial. Several inflammatory mediator-targeted therapies have progressed successfully through early clinical evaluation. Among these, neutrophil elastase inhibitors have shown the most promise and are currently undergoing Phase III trials. Other mediator-targeted therapies, such as prostaglandin E1, IL-10 and platelet activating factor antagonists, have not been found efficacious in large clinical trials of ARDS. However, these therapies, along with coagulation modulators, may have a favourable impact on ARDS by improving outcomes in sepsis, the greatest risk factor for developing this condition. In the interim, supportive care through improvements in mechanical ventilation are beneficial, while specific fluid balance and nutrition strategies may prove advantageous.

Rational use of computerized protocols in the intensive care unit

Excess information in complex ICU environments exceeds human decision making limits, increasing the likelihood of clinical errors. Explicit decision-support tools have favorable effects on clinician and patient outcomes and can reduce the variation in clinical practice that persists even when guidelines based on reputable evidence are available. Computerized protocols used for complex clinical problems generate, at the point-of-care, patient-specific evidence-based therapy instructions that can be carried out by different clinicians with almost no inter-clinician variability. Individualization of patient therapy is preserved by these explicit protocols since they are driven by patient data. Computerized protocols that aid ICU decision-makers should be more widely distributed.