Pulmonary artery catheterization and esophageal doppler monitoring in the ICU

Fluid and Volume Monitoring

Background

Fluid resuscitation is not only used to prevent acute kidney injury (AKI) but fluid management is also a cornerstone of treatment for patients with established AKI and renal failure. Ultrafiltration removes volume initially from the intravascular compartment inducing a relative degree of hypovolemia. Normal reflex mechanisms attempt to sustain blood pressure constant despite marked changes in blood volume and cardiac output. Thus, compensated shock with a normal blood pressure is a major cause of AKI or exacerbations of AKI during ultrafiltration.

Methods

We undertook a systematic review of the literature using MEDLINE, Google Scholar 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 clinical practice recommendations and/or directions for future research.

Results

We defined three aspects of fluid monitoring: i) normal and pathophysiological cardiovascular mechanisms; ii) measures of volume responsiveness and impending cardiovascular collapse during volume removal, and; iii) measured indices of each using non-invasive and minimally invasive continuous and intermittent monitoring techniques. The evidence documents that AKI can occur in the setting of normotensive hypovolemia and that under-resuscitation represents a major cause of both AKI and mortality ion critically ill patients. Traditional measures of intravascular volume and ventricular filling do not predict volume responsiveness whereas dynamic functional hemodynamic markers, such as pulse pressure or stroke volume variation during positive pressure breathing or mean flow changes with passive leg raising are highly predictive of volume responsiveness. Numerous commercially-available devices exist that can acquire these signals.

Conclusions

Prospective clinical trials using functional hemodynamic markers in the diagnosis and management of AKI and volume status during ultrafiltration need to be performed. More traditional measure of preload be abandoned as marked of volume responsiveness though still useful to assess overall volume status.

2017 Comprehensive Update of the Canadian Cardiovascular Society Guidelines for the Management of Heart Failure

Since the inception of the Canadian Cardiovascular Society heart failure (HF) guidelines in 2006, much has changed in the care for patients with HF. Over the past decade, the HF Guidelines Committee has published regular updates. However, because of the major changes that have occurred, the Guidelines Committee believes that a comprehensive reassessment of the HF management recommendations is presently needed, with a view to producing a full and complete set of updated guidelines. The primary and secondary Canadian Cardiovascular Society HF panel members as well as external experts have reviewed clinically relevant literature to provide guidance for the practicing clinician. The 2017 HF guidelines provide updated guidance on the diagnosis and management (self-care, pharmacologic, nonpharmacologic, device, and referral) that should aid in day-to-day decisions for caring for patients with HF. Among specific issues covered are risk scores, the differences in management for HF with preserved vs reduced ejection fraction, exercise and rehabilitation, implantable devices, revascularization, right ventricular dysfunction, anemia, and iron deficiency, cardiorenal syndrome, sleep apnea, cardiomyopathies, HF in pregnancy, cardio-oncology, and myocarditis. We devoted attention to strategies and treatments to prevent HF, to the organization of HF care, comorbidity management, as well as practical issues around the timing of referral and follow-up care. Recognition and treatment of advanced HF is another important aspect of this update, including how to select advanced therapies as well as end of life considerations. Finally, we acknowledge the remaining gaps in evidence that need to be filled by future research.

Hemodynamic Effects of Volume-Controlled Ventilation Versus Pressure-Controlled Ventilation in Head Trauma Patients

Background. Controlled ventilation for head trauma patients should reduce hypoxemia, hypercapnia and prevent secondary brain injury. However, changes in cardiac output and arterial blood pressure are the common consequences of mechanical ventilation. This study was designed to compare pressure- versus volume-controlled ventilation modes in severe head trauma patients to identify the mode with least hemodynamic compromise and best oxygenation profile. Methods. This prospective crossover study was carried out on 15 severe head trauma patients admitted to surgical ICU for mechanical ventilation and critical care. All patients were initially ventilated with volume-controlled ventilation for 12 hours then the mode of ventilation was changed to pressure-controlled ventilation for the next 12 hours. Arterial and pulmonary artery catheters were inserted for continuous monitoring of arterial blood pressure, cardiac output, pulmonary artery pressure, pulmonary wedge pressure, pulmonary vascular resistance, and systemic vascular resistance every 4 hours from the start of each ventilation mode. Lung mechanics and arterial blood gases were simultaneously recorded during the times of hemodynamic monitoring. Results. Cardiac output did not show significant changes between the 2 ventilation modes and mean group differences at 4, 8, and 12 hours were −0.2, −0.2, −0.1 L/min (95% confidence interval = −1.04 to 0.64, −0.92 to 0.52, and −0.68 to 0.48 L/min), respectively. Additionally, the other hemodynamic variables were comparable at all levels of study analysis. Volume-controlled ventilation was associated with significant higher peak air way pressure in comparison with pressure-controlled ventilation after 4, 8, and 12 hours. The oxygenation values and other lung mechanics were not significantly change between the 2 ventilation modes. Conclusion. Both volume-controlled and pressure-controlled ventilations have comparable hemodynamic and oxygenation profiles in severe head trauma patients for short-term ventilation.

The 2012 Canadian Cardiovascular Society heart failure management guidelines update: focus on acute and chronic heart failure

The 2012 Canadian Cardiovascular Society Heart Failure (HF) Guidelines Update provides management recommendations for acute and chronic HF. In 2006, the Canadian Cardiovascular Society HF Guidelines committee first published an overview of HF management. Since then, significant additions to and changes in many of these recommendations have become apparent. With this in mind and in response to stakeholder feedback, the Guidelines Committee in 2012 has updated the overview of both acute and chronic heart failure diagnosis and management. The 2012 Update also includes recommendations, values and preferences, and practical tips to assist the medical practitioner manage their patients with HF.

Applications of minimally invasive cardiac output monitors

Because of the increasing age of the population, critical care and emergency medicine physicians have seen an increased number of critically ill patients over the last decade. Moreover, the trend of hospital closures in the United States t imposes a burden of increased efficiency. Hence, the identification of devices that facilitate accurate but rapid assessments of hemodynamic parameters without the added burden of invasiveness becomes tantamount. The purpose of this review is to understand the applications and limitations of these new technologies.

Routine transthoracic echocardiography in a general Intensive Care Unit: an 18 month survey in 704 patients

The authors analyzed 704 transthoracic echocardiographic (TTE) examinations, performed routinely to all admitted patients to a general 16-bed Intensive Care Unit (ICU) during an 18-month period. Data acquisition and prevalence of abnormalities of cardiac structures and function were assessed, as well as the new, previously unknown severe diagnoses. A TTE was performed within the first 24 h of admission on 704 consecutive patients, with a mean age of 61.5+/-17.5 years, ICU stay of 10.6+/-17.1 days, APACHE II 22.6+/-8.9, and SAPS II 52.7+/-20.4. In four patients, TTE could not be performed. Left ventricular (LV) dimensions were quantified in 689 (97.8%) patients, and LV function in 670 (95.2%) patients. Cardiac output (CO) was determined in 610 (86.7%), and mitral E/A in 399 (85.9% of patients in sinus rhythm). Echocardiographic abnormalities were detected in 234 (33%) patients, the most common being left atrial (LA) enlargement (n=163), and LV dysfunction (n=132). Patients with these alterations were older (66+/-16.5 vs 58.1+/-17.4, p<0.001), presented a higher APACHE II score (24.4+/-8.7 vs 21.1+/-8.9, p<0.001), and had a higher mortality rate (40.1% vs 25.4%, p<0.001). Severe, previously unknown echocardiographic diagnoses were detected in 53 (7.5%) patients; the most frequent condition was severe LV dysfunction. Through a multivariate logistic regression analysis, it was determined that mortality was affected by tricuspid regurgitation (p=0.016, CI 1.007-1.016) and ICU stay (p<0.001, CI 1-1.019). We conclude that TTE can detect most cardiac structures in a general ICU. One-third of the patients studied presented cardiac structural or functional alterations and 7.5% severe previously unknown diagnoses.

Bedside echocardiography in the assessment of the critically ill

Advances in ultrasound technology continue to enhance its diagnostic applications in daily medical practice. Bedside echocardiographic examination has become useful to properly trained cardiologists, anesthesiologists, intensivists, surgeons, and emergency room physicians. Cardiac ultrasound can permit rapid, accurate, and noninvasive diagnosis of a broad range of acute cardiovascular pathologies. Although transesophageal echocardiography was once the principal diagnostic approach using ultrasound to evaluate intensive care unit patients, advances in ultrasound imaging, including harmonic imaging, digital acquisition, and contrast for endocardial enhancement, has improved the diagnostic yield of transthoracic echocardiography. Ultrasound devices continue to become more portable, and hand-carried devices are now readily available for bedside applications. This article discusses the application of bedside echocardiography in the intensive care unit. The emphasis is on echocardiography and cardiovascular diagnostics, specifically on goal-directed bedside cardiac ultrasonography.

Canadian Cardiovascular Society Consensus Conference recommendations on heart failure update 2007: Prevention, management during intercurrent illness or acute decompensation, and use of biomarkers

Heart failure is common, yet it is difficult to treat. It presents in many different guises and circumstances in which therapy needs to be individualized. The Canadian Cardiovascular Society published a comprehensive set of recommendations in January 2006 on the diagnosis and management of heart failure, and the present update builds on those core recommendations. Based on feedback obtained through a national program of heart failure workshops during 2006, several topics were identified as priorities because of the challenges they pose to health care professionals. New evidence-based recommendations were developed using the structured approach for the review and assessment of evidence adopted and previously described by the Society. Specific recommendations and practical tips were written for the prevention of heart failure, the management of heart failure during intercurrent illness, the treatment of acute heart failure, and the current and future roles of biomarkers in heart failure care. Specific clinical questions that are addressed include: which patients should be identified as being at high risk of developing heart failure and which interventions should be used? What complications can occur in heart failure patients during an intercurrent illness, how should these patients be monitored and which medications may require a dose adjustment or discontinuation? What are the best therapeutic, both drug and nondrug, strategies for patients with acute heart failure? How can new biomarkers help in the treatment of heart failure, and when and how should BNP be measured in heart failure patients? The goals of the present update are to translate best evidence into practice, to apply clinical wisdom where evidence for specific strategies is weaker, and to aid physicians and other health care providers to optimally treat heart failure patients to result in a measurable impact on patient health and clinical outcomes in Canada.

Transcutaneous pressure of oxygen: a noninvasive and early detector of peripheral shock and outcome

A noninvasive tool to recognize early shock would improve outcome by providing prompt recognition of tissue ischemia and precise resuscitation endpoint. The skin is the first tissue bed to vasoconstrict in shock states. Studies have demonstrated that transcutaneous partial pressure of oxygen (PtCO2) increases with higher FiO2 in nonshock states as arterial pressure of oxygen (PaO2) increases, but in shock situations, PtCO2 mirrors changes in cardiac output and oxygen delivery with minimum response to increasing FiO2 and PaO2. This study examined the relationship of hemodynamic variables and the degree of PtCO2 response to FiO2 of 1.0 (identified as the "oxygen challenge test") to mortality and organ failure. This prospective observational study examined 38 patients requiring at least 24 h of cardiac output monitoring for shock resuscitation in the Surgical Intensive Care Unit. Patients were resuscitated to the standard protocol of blood pressure, urine output, oxygen delivery (DO2), and mixed venous O2 (SvO2). Seventy-nine percent of the patients (30/38) with a mean age of 59 +/- 21 years had septic shock or severe sepsis with a 26% mortality (10/38). Measurements included hemodynamic variables, PtCO2, and outcome (mortality and organ failure). In this study, the ability of PtCO2 value to increase by 21 mmHg on a FiO2 of 1.0, at 24 h of resuscitation, divided survivors from nonsurvivors, P <.001. The PtCO2 response to FiO2 may provide an additional noninvasive method of detecting early shock as well as a specific endpoint of resuscitation.

Real-time Three-dimensional Color Doppler Echocardiography Overcomes the Inaccuracies of Spectral Doppler for Stroke Volume Calculation

Real-time 3-dimensional echocardiography is increasingly used in clinical cardiology. Studies have been shown that this technique can be accurately used to assess both cardiac mass and chamber volumes. We review the work showing that real-time 3-dimensional Doppler echocardiography can be used to accurately calculate intracardiac flow volumes that can potentially be used to assess cardiac function, intracardiac shunt, and valve regurgitation.

The effect of fundal pressure at Caesarean section on maternal haemodynamics

In 20 women undergoing Caesarean section, we determined brachial arterial blood pressure, heart rate and cardiac output (using an oesophageal Doppler probe) just after uterine incision and during the application of extra-abdominal uterine fundal pressure to facilitate delivery. Mean (SD) systolic aortic flow time (354.3 (35.4) ms), cardiac output (3.85 (0.68) l.min(-1)), heart rate (80.6 (14.2) beats.min(-1)) and blood pressure (84.7 (12.1) mmHg) decreased when fundal pressure was applied compared with after uterine incision (397.6 (31.6) ms, 4.69 (0.78) l.min(-1), 95.1 (14.0) beats.min(-1)and 100.3 (12.0) mmHg, respectively; p < 0.05). Peak velocity and stroke distance of the aortic flow when fundal pressure was applied was similar to after uterine incision. The mothers and babies were not observed to be clinically compromised. The results suggest that applying fundal pressure to facilitate Caesarean delivery produces significant haemodynamic effects but the impact of these effects may be clinically insignificant.

Esophageal Doppler (ODM II) improves intraoperative hemodynamic monitoring during laparoscopic surgery

Minimally invasive laparoscopic surgery has been expanded to the elderly and high-risk surgical patients with underlying cardiac and pulmonary disease. However, possible cardiovascular changes during CO2 pneumoperitoneum necessitate close intraoperative monitoring. In this prospective study, 55 patients (mean age 62.52 years, range 26-82) undergoing laparoscopic surgery were included. Patients were categorized into 3 groups of low (group A: 12 patients, mean age 55.5 years), moderate (group B: 22 patients, mean age 59.5 years), and high (group C: 21 patients, mean age 69.71 years) surgical risk according to ASA physical status classification. Similar anesthetic agents and anesthetic techniques were used in the above cases. An esophageal Doppler (ODM II, Abbott Laboratories) was used to measure aortic blood flow velocity and thereby estimating stroke volume (SVe) and cardiac output (COe) throughout anesthesia, in addition to traditional monitoring. After abdominal insufflation (peak intra-abdominal pressure: 13-15 mm Hg) COe values decreased from the initial value after induction of anesthesia by 22%, 20%, and 18% for groups A, B, and C, respectively (P < 0.05). The above values further deteriorated (25%, 28%, and 30% for groups A, B, and C, respectively) in the anti-Trendelenburg positioning of the patient. The peak aortic blood flow velocity (PV) followed the changes, thus indicating that heart muscle contractility is affected during the procedure. Stabilization of the above values was achieved after 20 minutes of CO(2) pneumoperitoneum and improvement was noted only after deflation of the abdomen. Heart rate and blood pressure essentially remained unchanged throughout the procedure, although the final values were increased compared with initial. Insufflation of the abdomen with CO(2) produces measurable effects on the cardiovascular system that require reappraisal of hemodynamic monitoring during anesthesia. ODM II offers a reliable, relatively noninvasive, cost-effective tool for intraoperative monitoring of the hemodynamic changes with a potential for future application for improvement of intraoperative hemodynamic status of patients.

Bedside Ultrasonography in the ICU

This is the second of a two-part review on the application of bedside ultrasonography in the ICU. In this part, the following procedures will be covered: (1) echocardiography and cardiovascular diagnostics (second part); (2) the use of bedside ultrasound to facilitate central-line placement and to aid in the care of patients with pleural effusions and intra-abdominal fluid collections; (3) the role of hand-carried ultrasound in the ICU; and (4) the performance of bedside ultrasound by the intensivist. The safety and utility of bedside ultrasonography performed by adequately trained intensivists has now been well demonstrated. This technology, as a powerful adjunct to the physical examination, will become an indispensable tool in the management of critically ill patients.

Advances and New Insights in Monitoring

It cannot be overemphasized that a piece of electrical equipment is not capable of replacing a vigilant, well-trained clinician. As monitoring devices become more sophisticated, the potential for artifact or misinterpretation increases. When applied appropriately, operated properly, and interpreted correctly, however, the monitors afford the patient the best possible outcome.

The use of live three-dimensional Doppler echocardiography in the measurement of cardiac output

OBJECTIVES

The purpose of this study was to investigate whether cardiac output (CO) could be accurately computed from live three-dimensional (3-D) Doppler echocardiographic data in an acute open-chested animal preparation.

BACKGROUND

The accurate measurement of CO is important in both patient management and research. Current methods use invasive pulmonary artery catheters or two-dimensional (2-D) echocardiography or esophageal aortic Doppler measures, with the inherent risks and inaccuracies of these techniques.

METHODS

Seventeen juvenile, open-chested pigs were studied before undergoing a separate cardiopulmonary bypass procedure. Live 3-D Doppler echocardiography images of the left ventricular outflow tract and aortic valve were obtained by epicardial scanning, using a Philips Medical Systems (Andover, Massachusetts) Sonos 7500 Live 3-D Echo system with a 2.5-MHz probe. Simultaneous CO measurements were obtained from an ultrasonic flow probe placed around the aortic root. Subsequent offline processing using custom software computed the CO from the digital 3-D Doppler DICOM data, and this was compared to the gold standard of the aortic flow probe measurements.

RESULTS

One hundred forty-three individual CO measurements were taken from 16 pigs, one being excluded because of severe aortic regurgitation. There was good correlation between the 3-D Doppler and flow probe methods of CO measurement (y = 1.1x - 9.82, R(2) = 0.93).

CONCLUSIONS

In this acute animal preparation, live 3-D Doppler echocardiographic data allowed for accurate assessment of CO as compared to the ultrasonic flow probe measurement.

Hemodynamic Assessment

Hemodynamic monitoring has become an integral component of the assessment of the critically ill. Any technology used for monitoring is a diagnostic tool and only as good as the provider interpreting the data. The article focuses on providing the practitioner the physiologic basis of the hemodynamic profile to cross the chasm of turning data into clinically useful information. Decision-making models are described to facilitate data synthesis and clinical intervention.

Determination of Cardiac Output With Multislice Spiral Computed Tomography

OBJECTIVE

To validate and to determine the reproducibility of cardiac output (CO) measurements based on a test-bolus examination in multislice spiral computed tomography (MSCT) in comparison with invasively measured CO using the thermal dilution technique.

MATERIAL AND METHODS

In 8 swine, CO was determined by invasive thermal dilution technique and by analysis of enhancement data from dynamic MSCT test-bolus examinations. To assess reproducibility, all MSCT examinations were performed twice. Results were compared using Pearson's correlation coefficient and Bland-Altman plots.

RESULTS

Measure by thermal dilution technique CO was 3.71 +/- 1.12 L/min, whereas CO was 3.67 +/- 1.30 L/min using MSCT. Pearson's correlation coefficient was 0.89. The average deviation between MSCT and thermal dilution technique was 0.04 L/min with a standard deviation of 0.59 L/min. There was a good agreement between both MSCT measurements with a mean deviation of -0.03 L/min and a standard deviation of 0.51 L/min.

CONCLUSION

CO can reliably be determined from MSCT by means of indicator dilution technique. Measurements are reproducible and provide valuable information on the overall cardiovascular performance without application of additional contrast material or radiation. As this technique does not require time-consuming postprocessing it can be added to routine reporting.

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.

Cardiac Output Determination During Experimental Hemorrhage and Resuscitation Using a Transesophageal Doppler Monitor

Transesophageal Doppler (TED) monitoring has been considered a noninvasive and accurate alternative to pulmonary artery catheterization for volume replacement and cardiac output measurement in patients undergoing major surgery. This study tested the hypothesis that TED can accurately predict cardiac output during hemorrhage, shock, and resuscitation, by comparing it to total pulmonary artery blood flow (PABF) and to standard intermittent bolus cardiac output (ICO). In eight anesthetized dogs (18 +/- 1.0 kg), PABF was measured with an ultrasonic flowprobe while ICO and mixed venous O2 saturation (SvO2) were measured through a Swan-Ganz catheter. A TED probe (CardioQ, Deltex Medical Inc., Irving, TX, U.S.A.), designed for adult use (minimum 30 kg, 16 years), was placed in midesophageous to evaluate stroke volume. A graded hemorrhage (20 mL/min) was produced (H5-H35) to a mean arterial pressure (MAP) of 40 mm Hg and maintained by additional blood removal for 30 min (S1-S30). Total shed blood volume was retransfused (541 +/- 54.2 mL) over 30 min (T5-T30), after which a massive hemorrhage, 100 mL/min rate, was produced over 10 min (MH5-MH10). In general, TED overestimated PABF (r2 = 0.3472), but changes in TED paralleled PABF throughout the experimental protocol, particularly during massive hemorrhage (r2 = 0.9001). We concluded that TED accurately reflected the direction and magnitude of the changes of cardiac output over time during abrupt hemodynamic changes. Probes designed for lower weights and smaller aortas may improve its accuracy in medium size animal models under less dramatic alterations induced by hemorrhage, shock, and resuscitation.

Management of Severe Sepsis: Integration of Multiple Pharmacologic Interventions

Severe sepsis is an infection-induced process that often promotes organ dysfunction and death in up to 50% of afflicted patients. Clinical advances that improve patient survival include early goal-directed volume resuscitation, broad-spectrum empiric antimicrobial therapy with deescalation strategies, therapy with drotrecogin alfa (activated), glucocorticoid replacement in patients with adrenal insufficiency, and tight control of blood glucose levels. The challenge for critical care practitioners is to integrate the many pharmacologic and supportive interventions required for optimal care of these patients.

Critical care in cardiovascular medicine

The field of cardiac intensive care is rapidly evolving with nearly simultaneous advances in surgical techniques and adjunctive therapies, respiratory care, intensive care technology and monitoring, pharmacologic research and development, and computing and electronics. The focus of care has now shifted toward reducing morbidity and improving "quality of life" while the survival of infants and children with congenital heart defects, including those with univentricular hearts has dramatically improved during the last three decades. Despite these advances, there remains a predictable fall in cardiac output after cardiopulmonary bypass. This article focuses on early identification and aggressive treatment of the low cardiac output syndrome peculiar to these patients. The authors also briefly review the recent advances in the treatment of pulmonary hypertension, mechanical support, and neurologic surveillance after cardiac surgery.

Physicians’ Estimates of Cardiac Index and Intravascular Volume Based on Clinical Assessment Versus Transesophageal Doppler Measurements Obtained by Critical Care Nurses

• Objectives To compare physicians’ estimates of cardiac index and intravascular volume with transesophageal Doppler measurements obtained by critical care nurses, to assess the overall safety of transesophageal Doppler imaging by critical care nurses, and to compare hemodynamic measurements obtained via transesophageal Doppler imaging with those obtained via pulmonary artery catheterization.

• Methods Data were collected prospectively on 106 patients receiving mechanical ventilation. Physicians estimated cardiac index and intravascular volume status by using bedside clinical assessment; critical care nurses, by using transesophageal Doppler imaging. In 24 patients, Doppler measurements were obtained within 6 hours of placement of a pulmonary artery catheter and recording of cardiac output and pulmonary artery occlusion pressure.

• Results With Doppler measurements as the reference, physicians correctly estimated cardiac index in 46 (43.8%) of 105 patients, underestimated it in 24 (22.9%), and overestimated it in 35 (33.3%). They correctly estimated volume status in 31 patients (29.5%), underestimated it in 16 (15.2%), and overestimated it in 58 (55.2%). Doppler measurements of cardiac output correlated with those obtained via pulmonary artery catheterization (r = 0.778; P &lt; .001). Two patients had minor complications: dislodgement of a nasogastric tube and inability to obtain a Doppler signal.

• Conclusion Physicians’ assessment of cardiac index and intravascular volume in patients receiving mechanical ventilation is correct less than half of the time. Transesophageal Doppler imaging by critical care nurses appears to be a safe method for measuring cardiac index and estimating intravascular volume. Measurements obtained via Doppler imaging correlate well with those obtained via pulmonary artery catheterization.

Sublingual capnometry versus traditional markers of tissue oxygenation in critically ill patients

OBJECTIVE

The purpose of this study was to determine the prognostic value of sublingual PCO2 (P(SL)CO2), lactate concentration, and mixed venous oxygen saturation (S(MV)O2) in hemodynamically unstable intensive care patients and, additionally, to compare the temporal changes of these variables in response to treatment.

SETTING

Medical/surgical intensive care unit.

SUBJECTS

Fifty-four patients, mean age 58 +/- 8 yrs.

INTERVENTIONS

Oxyhemodynamic variables, arterial lactate concentration, and P(SL)CO2 were recorded in unselected sequential intensive care patients undergoing pulmonary artery catheterization. A data set was obtained immediately after insertion of the pulmonary artery catheter and repeated 4 and 8 hrs later.

MEASUREMENTS AND MAIN RESULTS

Twenty-one patients had severe sepsis or septic shock. Twenty-seven (50%) patients died. The initial P(SL)CO2_PaCO2 gradient (P(SL)CO2-diff) and the initial P(SL)CO2 were highly predictive of outcome (p =.0004 and p =.004, respectively); however, there was no difference in the arterial lactate concentration and S(MV)O2 between the survivors and nonsurvivors. The P(SL)CO2-diff had the best receiver operator characteristic characteristics (area under the curve, 0.75), with a P(SL)CO2-diff >25 mm Hg being the best discriminator of outcome. With treatment, the P(SL)CO2-diff decreased in both survivors and nonsurvivors; however, the lactate and S(MV)O2 remained relatively unchanged during the study period.

CONCLUSIONS

The baseline P(SL)CO2-diff and P(SL)CO2 were better predictors of outcome than traditional markers of tissue hypoxia and were more responsive to therapeutic interventions. The P(SL)CO2-diff and/or P(SL)CO2 may prove to be a useful marker for goal-directed therapy and for assessing the response to clinical interventions aimed at improving tissue oxygenation.

Monitoring cardiac function in intensive care

Systolic cardiac function results from the interaction of four interdependent factors: heart rate, preload, contractility, and afterload. Heart rate can be quantified easily at the bedside, while preload estimation has traditionally relied on invasive pressure measurements, both central venous and pulmonary artery wedge. These have significant clinical limitations; however, adult literature has highlighted the superiority of several novel preload measures. Measurement of contractility and afterload is difficult; thus in clinical practice the bedside assessment of cardiac function is represented by cardiac output. A variety of techniques are now available for cardiac output measurement in the paediatric patient. This review summarises cardiac function and cardiac output measurement in terms of methodology, interpretation, and their contribution to the concepts of oxygen delivery and consumption in the critically ill child.

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.

Management of head trauma

Traumatic brain injury (TBI) is a major cause of disability and death in most Western nations and consumes an estimated $100 billion annually in the United States alone. In the last 2 decades, the management of TBI has evolved dramatically, as a result of a more thorough understanding of the physiologic events leading to secondary neuronal injury as well as advances in the care of critically ill patients. However, it is likely that many patients with TBI are not treated according to current treatment principles. This article presents an overview of the current management of patients with TBI.

Measurement of cardiac output and tissue perfusion

Recent technologic innovations have allowed a greater scope for cardiac output measurement in critically ill children. There is a move toward both less invasive and continuous methods, several of which also offer novel measures of preload. Many of the new methods are still undergoing preliminary evaluation in the pediatric population and will be summarized in this article.

Hemodynamic monitoring of the postoperative adult cardiac surgical patient

Surgery on the central blood pump, the heart, is performed either to prevent homeostatic compromise (ie, coronary artery disease potentially causing myocardial infarction and heart failure) or to treat actual homeostatic imbalance (ie, valvular disease causing heart failure). The cardiovascular homeostatic state is what we generally define as hemodynamics. The heart must deliver adequate oxygen and nutrients to all organs at appropriate pressures to allow optimal organ function. We monitor hemodynamic variables to assess the adequacy of a given cardiac repair and to detect any organ dysfunction that may independently coexist or be intimately related with the cardiac disease or its surgical repair. Hemodynamic monitoring initially relied on vital signs and periodic physical examination. The current monitoring capabilities have field expanded to include systemic and pulmonary arterial pressures, central venous pressures, cardiac output, systemic and pulmonary vascular resistance, and systemic and mixed venous oxygen saturation. These variables reflect a synthesis of global cardiac function and the peripheral or pulmonary vascular state. Arterial blood gas analysis further assesses the adequacy of overall oxygen delivery, carbon dioxide removal and acid-base balance. Echocardiography allows a qualitative and quantitative description of both global and regional cardiac function to better define the cardiac components of any hemodynamic state.