Goal-directed transesophageal echocardiography performed by intensivists to assess left ventricular function: comparison with pulmonary artery catheterization

OBJECTIVES

Transesophageal echocardiography (TEE) is a valuable procedure for assessing left ventricular (LV) function, but it has not been widely applied in critical care because of the limited number of intensivists who are trained in echocardiography. This prospective study was designed to evaluate the feasibility of training intensivists to perform a goal-directed, limited-scope TEE to assess LV function in critically ill patients using a pediatric monoplane TEE probe. A secondary goal was to compare the usefulness of the TEE data with that of data obtained by a simultaneous pulmonary artery catheter (PAC).

DESIGN

Prospective, blinded.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred consecutive, intubated, intensive care unit patients.

INTERVENTIONS

Five surgical intensivists with no previous background in echocardiography were trained under the supervision of two cardiologists to perform limited-scope TEE using a monoplane pediatric probe. One intensivist (A) reviewed the PAC data and recorded a diagnostic impression and therapeutic plan. A second intensivist (B), blinded to the PAC data, then performed TEE to determine cardiac volume, LV wall thickness, and LV global and regional wall motion. Intensivists A and B reviewed the data from both PAC and TEE, and intensivist A then formulated a new diagnosis and therapeutic plan.

MEASUREMENTS AND MAIN RESULTS

Intensivists performed 48 TEE examinations under direct supervision of a cardiologist, and 52 without supervision, but reviewed poststudy. The average duration of TEE was 12 +/- 7 minutes. The intensivists' interpretations of TEE data were deemed correct in 93% of cases for LV wall thickness, 87% for intracardiac volume status, 81% for regional LV wall motion abnormalities, and 77% for global LV function. When the TEE and PAC technologies were compared, it was found that the TEE data disagreed with the PAC evaluation of intracardiac volume in 55% of cases and with the PAC assessment of myocardial function in 39% of cases. The post-PAC therapeutic recommendations were different from the post-TEE therapeutic recommendations in 58% of patients.

CONCLUSIONS

Training intensivists in limited-scope, goal-directed TEE, using a pediatric monoplane probe to evaluate LV function, can be done rapidly and safely, and yield data pertinent to management of critically ill patients even in the early stages of skill acquisition.

Pulmonary artery catheters and outcome in the perioperative period

OBJECTIVE

To review the literature addressing use of the pulmonary artery catheter (PAC) in the perioperative patient.

DATA SOURCE

All pertinent English language articles dealing with the use of pulmonary artery catheterization in perioperative patients were retrieved from 1977 through 1996.

STUDY SELECTION

Articles were chosen if the perioperative use of pulmonary artery catheterization was studied or reviewed.

DATA EXTRACTION

From the articles selected, information was obtained about changes in therapy and changes in outcome associated with PAC use in patients undergoing cardiac surgery, aortic surgery, peripheral vascular surgery, and neurosurgery. Information was also extracted about perioperative PAC use in geriatric patients and in patients with preeclampsia.

DATA SYNTHESIS

Low-risk patients undergoing cardiac surgery do not appear to benefit from PAC use. Studies looking at high-risk patients undergoing cardiac surgery are lacking, making accurate determination of patient benefit difficult. The PAC may be useful in the management of some patients undergoing aortic surgery, though recent studies have identified populations of patients that can be safely monitored by less invasive means. Use of the PAC may lead to fewer complications in high-risk patients undergoing peripheral vascular surgery. Until data are forthcoming, it is not possible to accurately assess the overall impact of PAC use on complications and mortality in patients undergoing neurosurgical procedures. However, use of the PAC to monitor and treat air embolism in this group of patients does not appear to be appropriate. Routine perioperative use of the PAC does not appear to be appropriate because of age alone. Available scientific data do not support use of the PAC in patients with uncomplicated preeclampsia; however, some experts feel that PAC use may be helpful in the management of selected patients with severe preeclampsia.

CONCLUSION

There are no Grade A indications for PAC use in the perioperative period. Current available literature suffers from a lack of randomized controlled clinical trials. Multicentered randomized controlled trials are needed.

Practice patterns of anesthesiologists regarding situations in obstetric anesthesia where clinical management is controversial

A survey consisting of 47 questions, 40 regarding clinical practice and 7 regarding demographics, was mailed to 153 directors of obstetric anesthesia in academic practice and to 153 anesthesiologists in private practice. Questions relating to the following areas of practice were asked: 1) preoperative laboratory testing; 2) preeclampsia and possible coagulopathies; 3) epidural catheter placement in women with "spinal problems"; and 4) use of epidural opioids and intravenous supplementation. Surveys were returned by 113 (74%) academic anesthesiologists and 94 (61%) private practice anesthesiologists. By univariate analysis, 14 questions showed a significant difference in response between those in academic and private practice, but only eight remained significant after accounting for the amount of clinical time currently devoted to obstetric anesthesia (>50% or < or = 50%). These eight questions related to preoperative laboratory testing in the healthy parturient, preoperative laboratory testing in the preeclamptic patient, and the use of intravenous supplementation during a cesarean section with regional anesthesia. Although there were some differences in the responses between anesthesiologists in academic and private practice, overall the responses were similar.

Do pulmonary artery catheters improve patient outcome? No

The PAC has allowed physicians to obtain information that was unavailable prior to its introduction into clinical medicine. There are numerous pitfalls, however, in obtaining and interpreting this information. Even if these pitfalls are avoided, changing therapy to the patient's benefit based on PAC data is not guaranteed. In addition, application of new technologies, particularly TEE, has led to the suspicion that PA catheterization may frequently yield an incorrect assessment of the patient. Can PA catheterization lead to an improved outcome in an individual patient? If the patient is chosen carefully, the catheter inserted successfully and safely, the data obtained meticulously and interpreted correctly, and this interpretation leads to a change in therapy to which the patient responds appropriately, then the patient will experience an improved outcome based on PAC use. Does this happen often enough in the millions of catheterizations that are performed each year to improve the outcome of the group significantly as a whole? Almost certainly not.

Postoperative intravenous infusion of alprostadil (PGE1) does not improve renal function in hepatic transplant recipients

BACKGROUND

Acute renal failure is a frequent complication following orthotopic hepatic transplantation. A reduction in the synthesis of intrarenal vasodilator prostaglandins has been proposed as having an important role in the pathogenesis of renal insufficiency associated with hepatic dysfunction, as well as in the nephrotoxicity associated with cyclosporine and FK506 immunosuppressive therapy. Therefore, administration of vasodilator prostaglandins may improve renal function following hepatic transplantation. This study was designed to determine the effect of continuous intravenous alprostadil (prostaglandin E1) on postoperative renal function in hepatic transplant patients.

STUDY DESIGN

In a randomized, double-blind, placebo-controlled trial, 21 patients who had undergone orthotopic hepatic transplantation and had a measured postoperative glomerular filtration rate (GFR) of less that 50 mL/minute received intravenous alprostadil at 0.6 microgram/kg/hour or placebo for five days. Glomerular filtration rate and effective renal plasma flow (ERPF) were measured by a single-injection clearance method using a radionuclide agent in 53 patients within 12 hours after admission to our surgical intensive care unit. Usual postoperative care was not modified. Radionuclide GFR and ERPF measurements were repeated on postoperative day 3. Serum creatinine was measured preoperatively and postoperatively on day 3 and on day 5. A 24-hour serum creatinine clearance was measured on days 1, 5, and 14. Urine output was recorded hourly during the infusion period.

RESULTS

Ten patients received alprostadil, and 11 patients received placebo. There was a significant increase in GFR and ERPF in both groups on post-operative day 3 as compared with baseline values. There was no difference in GFR and ERPF between the two groups on day 3 (48 +/- 18 and 246 +/- 68 mL/minute in the alprostadil group compared with 53 +/- 17 and 270 +/- 131 mL/minute in the placebo group). Serum creatinine levels increased on day 3 in both groups but returned to baseline by day 5.

CONCLUSIONS

These results indicate that a reversible decrease in GFR is common on hepatic transplant patients during the postoperative period. Administration of a continuous intravenous infusion of alprostadil in the immediate postoperative period had no effect on renal function when compared with placebo.

Assessment of critical care nurses' knowledge of the pulmonary artery catheter. The Pulmonary Artery Catheter Study Group

OBJECTIVES

To assess the knowledge and understanding of the use of the pulmonary artery catheter and interpretation of data derived from it in a group of nurses attending the American Association of Critical Care Nurses' National Teaching Institute conference.

DESIGN

A 37-question multiple choice examination that tested knowledge regarding the use of the pulmonary artery catheter was administered to a group of nurses, attending a national conference, who preregistered for a hemodynamics workshop.

SETTING

American Association of Critical Care Nurses' National Teaching Institute Conference, New Orleans, LA, May 1992.

MEASUREMENTS AND MAIN RESULTS

Two-hundred sixteen nurses completed the questionnaire. The mean test score was 16.5 +/- 5.7 (SD) (48.5%). Test scores were significantly associated with years of experience in critical care, critical care registered nurse certification, responsibility for repositioning and manipulating the catheter, frequency of use, and self-assessed adequacy of knowledge.

CONCLUSIONS

A wide variation in the understanding of the use of the pulmonary artery catheter exists among nurses using this device in the care of seriously ill patients. The results indicate that current teaching practices regarding the pulmonary artery catheter need to be reevaluated and specific credentialing policies need to be considered.

Anesthesia for an achondroplastic dwarf presenting for urgent cesarean section

Achondroplasia is a physeal dysplasia which leads to dwarfism secondary to a decrease in the proliferation of cartilage in the growth plate. This, coupled with normal persistent bone formation, leads to the development of short tubular bones. Achondroplastic dwarfism is among the more common types of dwarfism and is inherited as an autosomal dominant trait. Its incidence is reported as 1 in 26,000 live births. Most achondroplastic dwarfs have a normal life span. The selection and management of anesthesia for the achondroplastic dwarf must take into account a variety of anatomic deformities. The physiologic and hormonal changes of pregnancy further complicate anesthetic administration. We report the safe use of a continuous lumbar epidural anesthetic in an achondroplastic dwarf who presented for urgent cesarean section.

Myocardial ischemia during the weaning period

OBJECTIVES: To estimate the incidence of silent myocardial ischemia, its pattern over time and its relationship to the time and mode of weaning high-risk cardiac patients after noncardiac surgery. DESIGN: Prospective study with random assignment to one of three weaning modes. SETTING: A surgical intensive care unit in a university hospital and a Veterans Administration hospital. PATIENTS: Sixty-two patients meeting standard criteria for extubation were randomized to one of three modes of weaning: synchronized intermittent mandatory ventilation (n = 19), T-Bar (n = 21) or continuous positive airway pressure (n = 22). METHODS: Ischemia was monitored with a continuous two-lead (V5, III) ST segment analyzer. Tracings were reviewed by a cardiologist. Ischemia was defined as greater than 1 mm ST segment depression 60 milliseconds after the J point. The monitoring period included a prewean (mean 654.0 minutes), wean (mean 46.5 minutes) and postwean (mean 1223.4 minutes) period. RESULTS: Of 62 patients, 12 (19.3%) experienced ischemia at some time during the monitoring period, most often during the weaning period. Ischemia during weaning was detected in 3 of 21 (14.3%) T-Bar patients and 2 of 22 (9.1%) continuous positive airway pressure patients but in no synchronized intermittent mandatory ventilation patients. CONCLUSION: This study demonstrates that silent myocardial ischemia occurs frequently in high-risk postoperative patients, with the highest incidence during weaning.

Myocardial ischemia during the weaning period

OBJECTIVES

To estimate the incidence of silent myocardial ischemia, its pattern over time and its relationship to the time and mode of weaning high-risk cardiac patients after noncardiac surgery.

DESIGN

Prospective study with random assignment to one of three weaning modes.

SETTING

A surgical intensive care unit in a university hospital and a Veterans Administration hospital.

PATIENTS

Sixty-two patients meeting standard criteria for extubation were randomized to one of three modes of weaning: synchronized intermittent mandatory ventilation (n = 19), T-Bar (n = 21) or continuous positive airway pressure (n = 22).

METHODS

Ischemia was monitored with a continuous two-lead (V5, III) ST segment analyzer. Tracings were reviewed by a cardiologist. Ischemia was defined as greater than 1 mm ST segment depression 60 milliseconds after the J point. The monitoring period included a prewean (mean 654.0 minutes), wean (mean 46.5 minutes) and postwean (mean 1223.4 minutes) period.

RESULTS

Of 62 patients, 12 (19.3%) experienced ischemia at some time during the monitoring period, most often during the weaning period. Ischemia during weaning was detected in 3 of 21 (14.3%) T-Bar patients and 2 of 22 (9.1%) continuous positive airway pressure patients but in no synchronized intermittent mandatory ventilation patients.

CONCLUSION

This study demonstrates that silent myocardial ischemia occurs frequently in high-risk postoperative patients, with the highest incidence during weaning.

Left-sided superior vena cava: a not-so-unusual vascular anomaly discovered during central venous and pulmonary artery catheterization

OBJECTIVE

To report our ICU experience with patients noted to have a left-sided superior vena cava after central venous and pulmonary artery catheterization.

DESIGN

Retrospective review.

SETTING

Surgical ICUs in a University and Veterans Administration Medical Center.

PATIENTS

Five patients who had insertion of central venous or pulmonary artery catheters were noted to have abnormal placement.

RESULTS

Five patients were noted to have a left-sided superior vena cava that was not appreciated on preinsertion radiography after central venous (two patients) or pulmonary artery catheterization (three patients). The finding of left-sided superior vena cava was confirmed by computed tomography scan (one patient), transesophageal echocardiography (one patient), bolus contrast injection (two patients), and intraoperative inspection (one patient).

CONCLUSIONS

Left-sided superior vena cava occurs infrequently, most often in association with a right-sided superior vena cava. It is often associated with cardiac septal defects. The intensivist should be aware of its occurrence in order to not mistake catheters placed in it as being present in the arterial circulation or malpositioned outside of the venous circulation.

Intravenous fat emulsions and the pancreas: a review

There is conflicting evidence of the effect of intravenous fat emulsions on pancreatic secretion. Intralipid is a safe component of intravenous nutritional support in patients with pancreatic fistulas, though it may minimally increase the volume, as well as the bicarbonate and amylase concentrations, of the output. Intravenous fat emulsions may rarely cause pancreatitis; this may be more likely in patients with Crohn's disease, given that three of the four reported cases occurred in patients with Crohn's disease. It is unclear whether hypertriglyceridemia secondary to the intravenous fat emulsion is a prerequisite for this complication to occur. Intravenous fat emulsions appear to be a safe component of intravenous nutritional support for the patient with pancreatitis, based on multiple studies proving their safety in a total of nearly 100 patients. It seems prudent to avoid hypertriglyceridemia secondary to intravenous fat emulsions, as this alone is a cause of pancreatitis, albeit uncommon, in patients with abnormalities of triglyceride metabolism. However, hypertriglyceridemia resulting from parenteral nutrition may be caused by glucose intolerance and not intravenous fat emulsion administration.

Anesthesia: what the internist needs to know

We have attempted to acquaint the internist with some aspects of anesthesiology that need to be kept in mind when performing perioperative consultation. Communication among and between the entire operative team will reduce risk and untoward reactions and will enhance the likelihood of successful outcome and rapid recovery.

A multicenter study of physicians' knowledge of the pulmonary artery catheter. Pulmonary Artery Catheter Study Group

We administered a 31-question multiple-choice examination to 496 physicians practicing in 13 medical facilities in the United States and Canada to assess their knowledge and understanding of the use of the pulmonary artery catheter and interpretation of data derived from it. The mean test score was 20.7 (67% correct), with an SD of 5.4 and a range of 6 to 31 (19% to 100%). Mean scores varied independently by training, frequency of use of pulmonary artery catheter data in patient treatment, frequency of inserting a pulmonary artery catheter, and whether the respondent's hospital was a primary medical school affiliate. Given the variability in physician understanding of the pulmonary artery catheter, we believe that credentialing policies should be reevaluated and that consideration should be given to restricting its use to individuals with documented competency.

Low sensitivity of the anion gap as a screen to detect hyperlactatemia in critically ill patients

The anion gap is commonly used as a screening test for the presence of lactic acidosis. Analysis of the distribution of anion gaps for 56 adult surgical ICU patients with peak blood lactate levels greater than or equal to 2.5 mmol/L showed the anion gap to be an insensitive screen for elevated lactate in a critically ill, hospitalized population. All patients (11/11) with a peak lactate greater than or equal to 10 mmol/L had an anion gap greater than or equal to 16 mmol/L; however, 50% (6/12) of patients with lactates between 5.0 and 9.9 mmol/L and 79% (26/33) of those with lactates between 2.5 and 4.9 mmol/L had anion gaps less than 16 mmol/L. Hyperlactatemia was associated with considerable mortality at all levels: 100% among patients with lactate levels greater than or equal to 10 mmol/L, 75% between 5.0 and 9.9 mmol/L, and 36.4% between 2.5 and 4.9 mmol/L. Acidosis (pH less than 7.30) did not significantly alter mortality by lactate level. The observation that, for 57% of patients in this study, an elevated lactate level was not accompanied by an elevated anion gap suggests that hyperlactatemia should be included in the differential diagnosis of nonanion gap acidosis.