Thermodilution cardiac output measurement during simultaneous volume infusion through the venous infusion port of the pulmonary artery catheter

OBJECTIVE

To determine the effect on thermodilution cardiac output (TDCO) measurements of continuous volume infusion through the right atrial venous infusion port of the pulmonary artery catheter.

DESIGN

Prospective, blinded, randomly allocated crossover.

SETTING

Surgical intensive care unit in a university hospital.

PARTICIPANTS

Forty-nine hemodynamically stable patients between the ages of 43 and 84 in the intensive care unit and with a pulmonary artery catheter in place.

INTERVENTIONS

Each patient received two room-temperature infusions (250 or 500 mL/hr) of 5% dextrose. Consecutive TDCO measurements were taken during each infusion and during a control period (no infusion). The sequence of infusion rates and control period was randomly determined. At both infusion rates, most patients exhibited a decrease in TDCO measurement of between 0.1 and 3.0 L/min. Although some patients exhibited an increase in measured TDCO, this increase was primarily between 0.1 and 0.5 L/min.

MEASUREMENTS AND MAIN RESULTS

The mean TDCO measurements at infusion rates of 0, 250, and 500 mL/hr were 6.77, 6.49, and 6.47 L/min, respectively. Measured TDCO decreased on volume infusion by 0.3 +/- 0.13 L/min (mean +/- SD, p < 0.02).

CONCLUSION

Rapid continuous infusion of fluid through the venous infusion port of the pulmonary artery catheter significantly limits the accuracy of simultaneous TDCO measurements. Optimally, TDCO measurements should be avoided during rapid volume infusion.

A second large controlled clinical study of E5, a monoclonal antibody to endotoxin: results of a prospective, multicenter, randomized, controlled trial. The E5 Sepsis Study Group

OBJECTIVE

To evaluate the safety and efficacy of E5, a murine, monoclonal antibody directed against endotoxin, in the treatment of patients with Gram-negative sepsis.

DESIGN

A multicenter, randomized, double-blind, placebo-controlled trial.

SETTING

Fifty-three hospitals across the United States, including university medical centers, Veterans Affairs Medical Centers, and community hospitals.

PATIENTS

847 patients were randomized into this study. Enrolled patients met criteria for three conditions: a) known or suspected Gram-negative infection; b) clinical evidence of sepsis; and c) signs of end-organ dysfunction. Patients with refractory shock were excluded from the study.

INTERVENTIONS

Two doses of E5 (2 mg/kg/day by intravenous infusion 24 hrs apart), or placebo that was identical in appearance were administered. In addition, all patients received standard supportive therapy and broad-spectrum antibiotics.

MEASUREMENTS AND MAIN RESULTS

The primary end point was mortality over 30 days. Secondary outcome measures included the resolution and prevention of organ failure in the same two populations. Additionally, the safety of E5 was evaluated. There was no significant improvement in survival over 30 days among patients with Gram-negative sepsis who received E5 compared with those patients who received placebo (n = 530; p = .21). In addition, E5 did not improve survival for patients with Gram-negative sepsis and organ failure (n = 139; p = .3). However, a significantly greater percentage of patients with Gram-negative sepsis experienced resolution of major organ failure if they received E5, compared with those patients who received placebo (n = 139; 48% E5 vs. 25% placebo; p = .005). This result extended to all patients who entered the study with one or more major organ failures, regardless of the etiology of the infection (n = 225; 41% E5 vs. 27% placebo; p = .024). E5 also provided protection against the development of some organ failures, but significant prevention was only observed for adult respiratory distress syndrome (p = .007) and central nervous system dysfunction (p = .050). Hypersensitivity reactions attributable to E5 occurred in 2.6% of patients. An asymptomatic antibody response occurred in 44% of the E5-treated patients and in 12% of the patients who received placebo.

CONCLUSIONS

In this study, E5 did not reduce mortality in nonshock patients with Gram-negative sepsis whether or not those patients also had organ failure. However, E5 did result in greater resolution of organ failure in patients with Gram-negative sepsis. This benefit extended to those patients with suspected Gram-negative etiology. This finding is important because patients with suspected Gram-negative sepsis and organ failure can be identified without waiting for culture results. In addition, E5 resulted in the prevention of adult respiratory distress syndrome and central nervous system organ failure. However, more studies are needed to determine if this result can be extended to organ failure in general. E5 is safe as a treatment for patients with Gram-negative sepsis.

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.

Effects of acid-base correction on hemodynamics, oxygen dynamics, and resuscitability in severe canine hemorrhagic shock

OBJECTIVE

To compare the effects of hypertonic saline, sodium bicarbonate, and Carbicarb resuscitation on acid-base balance, hemodynamics, and oxygen dynamics in a reperfused, canine hemorrhagic shock model.

DESIGN

Prospective, randomized trial.

SETTING

Laboratory at a university medical center.

SUBJECTS

Thirty-five anesthetized, mongrel dogs.

INTERVENTIONS

After the administration of anesthesia, the dogs were intubated and mechanically ventilated. Vascular catheters were inserted into each femoral artery, for continuous blood pressure monitoring, intermittent blood sampling, and for establishing controlled hemorrhage. A pulmonary artery catheter was inserted via the right jugular vein. Inhaled and exhaled gases were continuously analyzed using a metabolic gas monitor. The animals were subjected to 90 mins of controlled hemorrhagic shock. They were then randomly given a 2.5-mL/kg equimolar injection of 8.4% sodium bicarbonate, Carbicarb, or 5.84% hypertonic saline. The sodium load per kilogram of body weight was identical in all three groups. Thirty minutes later, the animals were retransfused with the shed blood over 15 mins and further observed for 120 mins.

MEASUREMENTS AND MAIN RESULTS

Carbicarb and sodium bicarbonate both significantly increased bicarbonate concentrations compared with saline. Arterial and venous blood pH increased more with Carbicarb than with bicarbonate but this increase was not statistically significant. After shock but before retransfusion, all three treatments moderately increased blood pressure, cardiac index, oxygen delivery index, and oxygen consumption index to a similar extent. After retransfusion, blood pressure, cardiac index, and oxygen dynamics temporarily improved in all groups, without significant improvement in the bicarbonate and Carbicarb-treated animals, despite their excellent acid-base status.

CONCLUSIONS

In severe canine hemorrhagic shock, Carbicarb, bicarbonate, and hypertonic saline appear to possess similar hemodynamic properties despite the buffering properties of bicarbonate and Carbicarb. The similar responses may be due to their identical sodium content. Arterial pH correction does not appear to further improve the responses to blood retransfusion.

Recombinant human interleukin 1 receptor antagonist in the treatment of patients with sepsis syndrome. Results from a randomized, double-blind, placebo-controlled trial. Phase III rhIL-1ra Sepsis Syndrome Study Group

OBJECTIVE

To further define the safety and efficacy of recombinant human interleukin 1 receptor antagonist (rhIL-1ra) in the treatment of sepsis syndrome.

STUDY DESIGN

Randomized, double-blind, placebo-controlled, multicenter, multinational clinical trial.

POPULATION

A total of 893 patients with sepsis syndrome received an intravenous loading dose of rhIL-1ra, 100 mg, or placebo followed by a continuous 72-hour intravenous infusion of rhIL-1ra (1.0 or 2.0 mg/kg per hour) or placebo.

OUTCOME MEASURE

Twenty-eight-day all-cause mortality.

RESULTS

There was not a significant increase in survival time for rhIL-1ra treatment compared with placebo among all patients who received the study medication (n = 893; generalized Wilcoxon statistic, P = .22) or among patients with shock at study entry (n = 713; generalized Wilcoxon statistic, P = .23), the two primary efficacy analyses specified a priori for this trial. Results from secondary analyses suggest an increase in survival time with rhIL-1ra treatment among patients with dysfunction of one or more organs (n = 563; linear dose-response, P = .009). Retrospective analysis demonstrated an increase in survival time with rhIL-1ra treatment among patients with a predicted risk of mortality of 24% or greater (n = 580; linear dose-response, P = .005) as well as among patients with both dysfunction of one or more organs and a predicted risk of mortality of 24% or greater (n = 411; linear dose-response, P = .002).

CONCLUSIONS

There was not a statistically significant increase in survival time for rhIL-1ra treatment compared with placebo among all patients who received the study medication or among patients with shock at study entry. Secondary and retrospective analyses of efficacy suggest that treatment with rhIL-1ra results in a dose-related increase in survival time among patients with sepsis who have organ dysfunction and/or a predicted risk of mortality of 24% or greater.

Abnormal coagulation profile in brain tumor patients during surgery

Neurosurgical patients are at high risk for the development of thrombosis and thromboembolism. We compared the perioperative clotting factor and coagulation parameters of 20 patients undergoing elective craniotomy for brain tumors to those of 20 patients undergoing elective abdominal surgery. We also measured the levels of plasma arginine vasopressin to determine if changes in this hormone might be associated with changes in clotting factors, activated partial thromboplastin times, or bleeding times. The results demonstrated a significant reduction in partial thromboplastin times and bleeding times in the neurosurgery group, which began at the initiation of surgery and lasted to the end of the study (12 h postoperatively). Elevations in factor assays and plasma arginine vasopressin occurred in both groups during surgery, but there were no differences between the neurosurgical and abdominal surgical patients, except with Factor IX levels, which were elevated only in the neurosurgical patients. Serum osmolality and hemoglobin levels were significantly higher in the neurosurgical cohort. These results suggest that there are hemostatic differences between neurosurgical patients with brain tumors and abdominal surgery patients that cannot be explained solely by elevations in plasma arginine vasopressin or the clotting factors measured; these differences may be the consequence of perioperative variables such as dehydration and hyperosmolality.

Epidemiology, pathophysiology and clinical presentation of gram-negative sepsis

OBJECTIVE

To review the epidemiology and pathophysiology of gram-negative sepsis and the new consensus terminology describing the clinical signs of sepsis.

DATA SOURCES

Review of the medical literature and compiled data from animal and clinical trials.

PARTICIPANTS

Members of the Society of Critical Care Medicine, American College of Chest Physicians and American Association of Critical-Care Nurses with expertise on the subject of sepsis and its complications.

RESULTS

Preconference and general sessions were offered at the National Teaching Institutes of the American Association of Critical-Care Nurses, with the goal of clarifying the epidemiology, risk factors and pathophysiology of gram-negative sepsis. In addition, current terminology and new (1992) consensus terminology describing the clinical signs of sepsis were presented. Special emphasis was placed on the role of the healthcare provider in the prevention and recognition of sepsis and the role of the septic mediators in the septic cascade.

CONCLUSIONS

If the incidence of sepsis is to be reduced, the healthcare provider must be aware of the risk factors for sepsis and methods of reducing nosocomial infections. A thorough understanding of the role of mediators and consensus terminology used to describe sepsis, severe sepsis, septic shock and multiple organ dysfunction syndrome is necessary to recognize early or progressive signs of sepsis and to initiate state-of-the-art therapy.

Epidemiology, pathophysiology and clinical presentation of gram-negative sepsis

OBJECTIVE: To review the epidemiology and pathophysiology of gram-negative sepsis and the new consensus terminology describing the clinical signs of sepsis. DATA SOURCES: Review of the medical literature and compiled data from animal and clinical trials. PARTICIPANTS: Members of the Society of Critical Care Medicine, American College of Chest Physicians and American Association of Critical-Care Nurses with expertise on the subject of sepsis and its complications. RESULTS: Preconference and general sessions were offered at the National Teaching Institutes of the American Association of Critical-Care Nurses, with the goal of clarifying the epidemiology, risk factors and pathophysiology of gram-negative sepsis. In addition, current terminology and new (1992) consensus terminology describing the clinical signs of sepsis were presented. Special emphasis was placed on the role of the healthcare provider in the prevention and recognition of sepsis and the role of the septic mediators in the septic cascade. CONCLUSIONS: If the incidence of sepsis is to be reduced, the healthcare provider must be aware of the risk factors for sepsis and methods of reducing nosocomial infections. A thorough understanding of the role of mediators and consensus terminology used to describe sepsis, severe sepsis, septic shock and multiple organ dysfunction syndrome is necessary to recognize early or progressive signs of sepsis and to initiate state-of-the-art therapy.

Acute mesenteric ischemia: pathophysiology, diagnosis, and treatment

Ischemia has traditionally been viewed as arising only from abnormalities of oxygen dynamics, namely the cellular hypoxia resulting from the imbalances between oxygen supply, consumption, and demand. Recently, it has become clear that such a view is too restrictive. Hypoperfusion may be caused by both anatomic and functional impediments to either inflow or to outflow from an organ. Furthermore, the pathophysiologic consequences are likely to involve not only cellular hypoxia, but also a restricted supply of nutrients and other important molecules and an abnormal elimination of physiologic wastes such as carbon dioxide. Hence the recommendation that ischemia be defined as a dual defect of oxygen deficit and carbon dioxide excess. AMI is, therefore, a severe anatomic or functional impediment to the splanchnic circulation, resulting in a dual defect of intestinal hypoxia and cellular hypercarbia. Although the functional and structural consequences of cellular hypoxia are well known, the pathophysiology of cellular hypercarbia has only begun to be explored. AMI syndromes include three related processes: occlusive mesenteric ischemia, nonocclusive ischemia, and sepsis-induced SI. Leakage of bacteria or bacterial toxins into the circulation during mesenteric ischemia forms the basis of the systemic components of this syndrome. Striving for an earlier diagnosis, treating the systemic (septic) consequences, and taking measures to promptly restore mucosal oxygen balance through aggressive pharmacologic and appropriate surgical intervention have significantly improved the prognosis. About 80% of patients with acute arterial embolism, 60% of those with nonocclusive ischemia, and only 20% of patients with arterial thrombosis are expected to live without significant residual nutritional deficits. The cause of death is usually sepsis and multisystem organ failure, and therefore, further reductions in mortality are likely to occur with the improved prevention and treatment of sepsis.

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.

Chest tube thoracostomy

Knowledge of the indications, placement, and management of chest tubes in the intensive care unit is essential for the care of the critically ill patient. Awareness of the complications and mechanical difficulties that can occur with chest tubes and their drainage systems is essential for the safe and effective use of these devices.

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.

Effects of pentoxifylline on hemodynamics, oxygen transport, and tissue metabolism in experimental, severe hemorrhagic shock

BACKGROUND AND METHODS

It is hypothesized that pentoxifylline may be beneficial during shock states by improving tissue oxygenation. To test this hypothesis, we examined the effect of pentoxifylline on hemodynamics, oxygen delivery (DO2), and tissue metabolism during severe hemorrhagic shock. We conducted a placebo-controlled, randomized trial using anesthetized, mechanically ventilated dogs in hemorrhagic shock maintained at a mean arterial pressure of 45 to 50 mm Hg. Six animals were treated with a 10-mg/kg bolus of iv pentoxifylline followed by a continuous infusion at 5 mg/kg.hr. The controls consisted of six animals treated with saline.

RESULTS

There were no significant differences between the groups before treatment. During 150 mins of posttreatment, repeated measurements of the control and pentoxifylline groups showed no significant differences in heart rate (HR), cardiac output, systemic and pulmonary vascular resistances, DO2, or blood lactate concentration (repeated-measures analysis of variance).

CONCLUSIONS

In this acute, nonresuscitated, canine hemorrhagic shock model, pentoxifylline did not act as a vasodilator, or have any significant effect on HR, cardiac output, oxygen transport, or lactic acidosis.

Toxic shock syndrome after pilonidal cystectomy. Report of a case

Toxic shock syndrome is an uncommon disease associated with staphylococcal infections. Although most frequently reported in menstruating women and associated with tampon use, toxic shock syndrome has been described following many types of surgical procedures. In this report we describe a case of toxic shock syndrome occurring in a previously healthy young man after elective surgery for a pilonidal cyst.

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.

Hemodynamic effects of H2-receptor antagonists

Histamine H2-receptor antagonists (H2RAs) often are administered to intensive care unit patients in an attempt to reduce gastric acidity and to prevent stress-related mucosal damage. These agents have an extremely low overall incidence and severity of adverse reactions; however, hemodynamically significant hypotension has been noted. Clinical studies with rapidly administered intravenous cimetidine in critically ill patients have demonstrated a depression in blood pressure in up to 75 percent of patients. Ranitidine, also studied in this setting, does not appear to induce similar hemodynamic changes. The newer H2RAs, famotidine and nizatidine, have not been evaluated in critically ill patients.

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.

Use of bedside laparoscopy to identify intestinal ischemia in postoperative cases of aortic reconstruction

Gangrenous bowel after aortic reconstructive surgery is associated with an exceptionally high mortality rate. Numerous diagnostic modalities have not reduced the incidence of death from infarcted bowel because of their lack of specificity and the associated delays in diagnosis. Recently, we have begun to use bedside laparoscopy to identify suspected gangrenous bowel in critically ill postoperative patients. Herein we describe a case of small-bowel infarction after aortic aneurysm surgery that was identified by the use of a laparoscope, with successful surgical repair and return of bowel function. Postoperative gangrenous bowel, standard diagnostic tests used in this setting, and the use and indications for beside laparoscopy are reviewed.

Determination of intra-abdominal pressure using a transurethral bladder catheter: clinical validation of the technique

The determination of intra-abdominal pressures (IAP) may be useful in many clinical situations. The authors recently demonstrated in the canine model a close correlation between actual IAP and the bladder pressure measurements obtained from a transurethral catheter. The purpose of this study was to clinically validate this technique. The authors studied 16 patients, and compared IAP in three positions (supine, with compressions, and semi-erect) utilizing both direct intraperitoneal pressure monitoring and the pressure obtained with a transurethral bladder catheter. Their results demonstrated a linear relationship between the two methods described, with a mean r value of 0.95 in the supine and semi-erect positions, and 0.99 with abdominal compressions (P less than 0.0001). The authors conclude that transurethral monitoring of bladder pressure offers a safe, simple, and highly accurate method for evaluating IAP at the bedside. Studies evaluating the indication for its use in the operating room and intensive care settings appear warranted.

The hemodynamic effects of intravenous ranitidine in intensive care unit patients: a double-blind prospective study

The hemodynamic effects of intravenous ranitidine were studied in a prospective double-blind fashion in postoperative intensive care unit patients to determine if this H2 blocker produced the same transient fall in mean arterial pressure and systemic vascular resistance known to occur with cimetidine infusion. We found no statistically significant hemodynamic changes from baseline associated with infusion of 50 mg ranitidine over a 5-minute period. The different chemical ring structure of ranitidine and its effect on H2 vascular and cardiac receptors may account for these observations.

Cardiopulmonary effects of the head-down tilt position in elderly postoperative patients: a prospective study

We studied the use of the head-down tilt position (Trendelenburg) in elderly postoperative patients in the intensive care unit to determine its effect upon cardiac and pulmonary function. Twenty-two patients (mean age 68.4 years) were placed in a 12 degrees head-down tilt position for 15 minutes. No deterioration was shown in any measured cardiac parameter; mean arterial pressure, cardiac index, and right and left ventricular stroke work increased significantly (P less than .05). Further, there were no observed changes in arterial or venous oxygenation, or in venous admixture. Because of the uncertain effect of the head-down tilt position upon cerebral blood flow, the routine use of this position is not recommended for the treatment of hypotension or during cardiopulmonary resuscitation. The results of this study, however, show that the cardiopulmonary effects are well tolerated if the position is required, as during central venous access procedures.

Effects of sodium bicarbonate in canine hemorrhagic shock

We studied the use of sodium bicarbonate administration in a canine model of hemorrhagic shock to determine its effect on hemodynamics, arterial and venous blood gases, respiratory gases, and blood lactate levels. Thirteen dogs were anesthetized, paralyzed, mechanically ventilated, and hemodynamically monitored. Hypotension was induced and maintained at a mean arterial pressure of 40 to 45 mm Hg using controlled hemorrhage and reinfusion. After 2.5 h of shock, the dogs were randomized into two groups: one group (n = 6) received NaCl infusion; the other (n = 7) received sodium bicarbonate (1 mEq/kg followed by a continuous infusion of 2.5 mEq/kg.h for 2.5 h). CO2 production was increased in the alkali group, but there was no statistically significant difference between groups in any measured hemodynamic, blood gas, or respiratory gas variable. These included heart rate, BP, cardiac output, arterial and venous pH, CO2 production, and bicarbonate levels. Blood lactate levels, however, in the bicarbonate treated animals were significantly (p less than .01) higher than in the group treated with NaCl alone (10.1 +/- 3.2 vs. 5.1 +/- 1.2 mEq/L). These results are similar to the effects of bicarbonate found in other models of lactic acidosis, and suggest that bicarbonate therapy may have limited usefulness in the treatment of lactic acidosis.

Use of percutaneous gastrostomy in the intensive care patient

We evaluated the use of percutaneous endoscopic gastrostomy in 30 ICU patients. There was a 14% incidence of minor complications, no major complications, and no mortality. We conclude that percutaneous endoscopic gastrostomy is a useful alternative to operative gastrostomy in the ICU patient.

A simple technique to accurately determine intra-abdominal pressure

The determination of intra-abdominal pressure (IAP) may be useful in a variety of clinical situations. Despite this, invasive IAP monitoring is seldom performed due to the risks involved. Using a standard canine model of increased IAP, we evaluated the accuracy of transurethral bladder catheter pressure in reflecting IAP. Throughout the range of IAP studied (10 +/- 5 to 70 +/- 10 mm Hg), bladder pressure did not differ significantly from the direct measurement of IAP. We conclude that the measurement of bladder pressure using a standard transurethral bladder catheter provides an accurate determination of IAP.

Control of catecholamine-induced tachycardia with alinidine in the anesthetized dog

Sinus tachycardia is a common complication of beta-adrenergic agonist therapy. A new selective bradycardic agent, N-allyl-clonidine, or alinidine, has been found effective against sinus tachycardia caused by a variety of stimuli. To determine whether it would also control catecholamine-induced sinus tachycardia, the effects of alinidine in two groups of anesthetized dogs treated with either dobutamine, 10 microg/ kg/min, or isoproterenol, 0.1 microg/kg/min, were studied. In both groups, alinidine significantly reduced the heart rate (P < .0001 in the dobutamine group, and P < .005 in the isoproterenol-infused dogs). The other hemodynamic effects of dobutamine were not adversely affected by alinidine, while the isoproterenol-infused dogs had a further afterload reduction when treated with alinidine. It is concluded that alinidine is effective against catecholamine-induced sinus tachycardia, possibly through mechanisms not related to beta-adrenergic receptors.

Venous hypercarbia in canine hemorrhagic shock

The venous-arterial PCO2 gradient may increase in certain low-flow states, such as CPR and canine endotoxemia. To determine whether venous hypercarbia also occurs in hemorrhagic shock, we studied 12 anesthetized, mechanically ventilated dogs. We performed laparotomies on the animals, inserting catheters into their renal, superior mesenteric, and external iliac veins. Flow in the corresponding arteries were determined using electromagnetic flow probes. The dogs were randomized into a control group (n = 6), and a hemorrhagic shock group (n = 6) which was bled to a mean arterial pressure of 45 to 50 mm Hg and maintained at this pressure for the 6-h study. The results demonstrated a significant (p less than .05) increase in lactate and venous-arterial PCO2 gradient systemically and in all three regional beds. A significant decrease of venous blood pH accompanied these changes which are consistent with our previous findings in low-flow, canine endotoxemia. We conclude that venous hypercarbia is a nonspecific phenomenon, common to low-flow states. The increased CO2 represents both an increased CO2 production and a decreased removal, secondary to low-flow.

Thrombocytopenia following peritonitis in surgical patients. A prospective study

Thrombocytopenia is commonly found in patients with serious infection. To investigate this phenomenon, 14 consecutive patients (68 +/- 10 years) who underwent laparotomy for bowel perforation and culture-proven peritonitis were prospectively studied. Ten noninfected laparotomy patients served as a control group. None of the 10 control patients developed thrombocytopenia. Of the infected group, 12 of 14 patients (85%) developed thrombocytopenia (less than 100,000/mm3). One patient (9%) developed disseminated intravascular coagulation (DIC). Of the remaining 11 patients with thrombocytopenia, platelet counts fell from preoperative level of 350,000 +/- 166,000 to 54,000 +/- 30,000 (p less than 0.001) and reached this nadir 4.3 +/- 2 days after surgery. There was no statistically significant difference in prothrombin time, partial thromboplastin time, or fibrinogen levels before versus after operation in this group. Bleeding times in seven patients were 5.5 +/- 2 minutes, and bone marrow examination in five patients with platelet counts of less than 50,000/mm3 revealed normal or increased megakaryocytes. No patient in this group bled, had medications held, or received platelet transfusions. Platelet counts increased greater than 100,000/mm3 at a mean of 8.9 +/- 4.1 days after operation. It is concluded that thrombocytopenia is common following surgery for intra-abdominal infection, is not usually associated with DIC, clinical bleeding, or coagulation abnormalities, does not commonly result from bone marrow suppression, and is transient and does not require routine platelet transfusions.

Use of constant-infusion verapamil for the treatment of postoperative supraventricular tachycardia

The effects of constant-infusion verapamil were studied in ten postoperative ICU patients who developed supraventricular tachycardia (atrial fibrillation) with rapid ventricular response rates. A 5-mg iv bolus dose of verapamil was followed by a 5-mg/h infusion that continued for 8 h. Ventricular rates were significantly (p less than .005) reduced from a pretreatment mean of 156 +/- 14 (SD) to 104 +/- 9 beat/min on constant-infusion therapy. This therapy was well tolerated without observed side-effects. Moreover, constant-infusion verapamil might avoid the hypotension and wide range of ventricular rates frequently encountered with repeated bolus doses of verapamil.