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Biomedical subjects

J W Meredith

Publications and source records attributed to J W Meredith.

At least 37 records · Page 2Linked to original sources
PubMed1998

Redefining cardiovascular performance during resuscitation: ventricular stroke work, power, and the pressure-volume diagram.

OBJECTIVES: (1) To compare left ventricular stroke work index (SW) and left ventricular power output (LVP), hemodynamic variables that encompass blood pressure as well as blood flow, with the purely flow-derived hemodynamic and oxygen transport variables as markers of perfusion and outcome in critically injured patients during resuscitation. (2) To use the ventricular pressure-volume diagram to define characteristic hemodynamic patterns in the determinants of SW and LVP that are associated with survival. METHODS: This was a cohort study at a university Level I trauma center during the course of 1 year. A consecutive series of patients was monitored with a volumetric pulmonary artery catheter during the initial 48 hours of resuscitation. Heart rate, SW, LVP, cardiac index, and oxygen delivery and consumption during resuscitation were compared using multivariate logistic regression analysis with regard to the ability to clear lactate in less than 24 hours and survival. Receiver operating characteristic curves were constructed to determine threshold values for SW and LVP. Ventricular pressure-volume diagrams were used to describe characteristic patterns in the determinants of SW and LVP in survivors and nonsurvivors. Preload was expressed as left ventricular end-diastolic volume index, afterload as aortic input impedance (Ea), and contractility as ventricular end-systolic elastance (Ees). The ratio of Ea/Ees (RATIO) was used as a measure of ventricular-arterial coupling, which describes the efficacy of energy transfer from the heart to the vascular system. RESULTS: One hundred eleven patients (87 survivors, 24 nonsurvivors) met study criteria. Survivors had a significantly higher SW (4,510 +/- 1,070 vs. 3,440 +/- 980 mm Hg x mL x m(-2); p < 0.0001) and LVP (370 +/- 94 vs. 270 +/- 81 mm Hg x L x min(-2) x m(-2); p < 0.0001) than nonsurvivors. Heart rate, SW, and LVP were the only studied variables that were significantly related to lactate clearance and survival by logistic regression. Threshold values determined by the receiver operating characteristic curves were 4,000 mm Hg x mL x m(-2) for SW and 320 mm Hg x L x min(-1) x m(-2) for LVP. Survivors had better ventricular-arterial coupling than nonsurvivors, indicated by a lower RATIO (0.32 +/- 0.22 vs. 0.54 +/- 0.38; p = 0.003). This lower RATIO was attributable to lower levels of Ea (2.7 +/- 0.7 vs. 3.4 +/- 0.8 mm Hg x mL(-1) x m(-2); p = 0.0003) and a trend toward higher levels of Ees (13 +/- 11 vs. 9.9 +/- 7.3 mm Hg x mL(-1) x m(-2); p = 0.12). CONCLUSION: Thermodynamic perfusion variables that encompass both pressure and flow, such as SW and LVP, are more closely related to perfusion and outcome than the purely flow-derived variables. The higher SW and LVP in survivors is related to better ventricular-arterial coupling, and therefore more efficient cardiac function. Cutoff values for LVP of 320 mm Hg x L x min(-1) x m(-2) and for SW of 4,000 mm Hg x mL x m(-2) may be useful thresholds for evaluating hemodynamic performance during resuscitation.

Adolescent↗
PubMed1998

Threshold values of intramucosal pH and mucosal-arterial CO2 gap during shock resuscitation.

BACKGROUND: The gastric intramucosal pH (pHi) and gastric mucosal-arterial CO2 gap (GAP) estimate visceral perfusion and predict outcome. Threshold values of these variables for use during resuscitation, however, remain poorly defined. The purpose of this study was to develop clinically derived cutoffs for both pHi and GAP for predicting death and multiple organ failure (MOF) in trauma patients. METHODS: This was a cohort study of 114 consecutive trauma patients who had pHi determined at 24 hours after intensive care unit admission. The corresponding GAP for each of these values of pHi was obtained through chart review. Receiver operating characteristic curves were constructed for both pHi and GAP with respect to death and MOF. These curves were used to determine the value of each variable that maximized the sum of sensitivity and specificity in predicting outcome. chi2 tests and odds ratios were used to determine if significant differences in outcome occurred above and below these cutoff values. RESULTS: Of 114 patients who had pHi determined at 24 hours after admission, 108 had corresponding GAP values available. The values of pHi and GAP that maximized sensitivity and specificity were 7.25 and 18 mm Hg, respectively. The odds ratio for pHi versus death was 4.6 and for pHi versus MOF was 4.3. The odds ratios for GAP versus death and MOF were 2.9 and 3.3, respectively. CONCLUSION: In trauma patients, the ability to predict death and MOF is maximized at values of pHi less than 7.25 and GAP greater than 18 mm Hg. These values represent clinically derived cutoffs that should be useful for evaluating the adequacy of intestinal perfusion during resuscitation.

Acid-Base Equilibrium↗
PubMed1998

Enalaprilat improves gut perfusion in critically injured patients.

Inadequate splanchnic perfusion, detected as a low gastric intramucosal pH (pHi), in the face of normal systemic perfusion predicts an increased risk for multiple organ failure after trauma. Although the exact etiology of this low pHi is unknown, angiotensin II is thought to be an important regulator of gut perfusion during and after resuscitation from shock. The purpose of this study is to determine whether enalaprilat, an angiotensin-converting enzyme inhibitor, improves gut perfusion in critically injured patients. To test this hypothesis, 18 trauma patients monitored with a nasogastric tonometer and a pulmonary artery catheter were enrolled in a prospective study. A single dose of enalaprilat, .625 mg, was given as an i.v. bolus or a 4 h infusion following systemic resuscitation. Pre- and postdrug tonometric and hemodynamic data, including cardiac index, mean arterial pressure, right ventricular end-diastolic volume index, systemic vascular resistance index, and oxygen transport variables were compared using the paired t test. Results demonstrate that pHi was significantly improved after 4 h (7.13 +/- .04 to 7.19 +/- .03, p = .03) and after 24 h compared with baseline (7.14 +/- .04 to 7.25 +/- .04, p = .04). Overall, pHi increased in 12 of 18 patients. No significant differences were observed in any of the studied hemodynamic or systemic perfusion variables including mean arterial pressure (92 +/- 4 to 87 +/- 4, p = .24) and oxygen delivery (669 +/- 33 to 675 +/- 32, p = .82). In examining the determinants of pHi, the intramucosal-arterial PCO2 difference was improved after enalaprilat administration (27 +/- 6 to 17 +/- 3 mmHg, p = .04) while no difference was observed in arterial bicarbonate (19.5 +/- .7 to 19.7 +/- .8, p = .90). Additionally, the change in pHi observed with enalaprilat correlated with predrug intramucosal-arterial PCO2 difference (r = .74, r2 = .55, p = .0005). These results demonstrate that enalaprilat improves gut perfusion as measured by gastric tonometry in critically injured patients, and that this effect appears to be independent of changes in systemic perfusion.

Adult↗
PubMed1998

Validity of CT classification on management of occult pneumothorax: a prospective study.

OBJECTIVE: In the setting of blunt trauma, abdominal CT, which routinely includes images of the lower thorax, frequently reveals pneumothoraces that have not been detected on routine supine chest radiographs. Proper management of these occult pneumothoraces remains controversial. The purpose of this study was to test the hypothesis that small (minuscule) to moderate (anterior) radiographically occult pneumothoraces can be safely managed without chest tube placement for patients in whom the need for positive pressure ventilation is not anticipated. SUBJECTS AND METHODS: We undertook a prospective study in which 44 occult pneumothoraces were classified into three groups, minuscule, anterior, or anterolateral, according to size and location on CT scans. Choice of initial management (tube thoracostomy versus close observation) was based in part on this classification system and in part on individual circumstances of a surgeon's decision. RESULTS: Of the 44 pneumothoraces found in 36 patients, 16 pneumothoraces were minuscule, 20 were anterior, and eight were anterolateral. Thirteen minuscule pneumothoraces and 11 anterior pneumothoraces initially managed with observation did not require subsequent tube thoracostomy. All eight patients with anterolateral pneumothoraces underwent tube thoracostomy. CONCLUSION: Most small (minuscule) occult pneumothoraces can successfully be managed with close observation. The risk that the pneumothorax will progress is slight. Moderate-sized (anterior) pneumothoraces may also be successfully managed without initial placement of a chest tube if the patient is not to undergo positive pressure ventilation.

Adolescent↗
PubMed1998

Pancreatic injuries resulting from penetrating trauma: a multi-institution review.

Pancreatic injury from penetrating trauma continues to be a source of significant morbidity and mortality, with questions remaining regarding optimal treatment of injuries. Our goal was to evaluate current trends in the operative management of these injuries. Our patient population comprised all patients admitted to one of three Level I trauma centers over an 8-year period that had sustained penetrating pancreatic trauma. The study was a retrospective chart review. Sixty-two patients were identified. All had associated abdominal injuries, with the liver and stomach being the most commonly injured organs. There were 14 deaths (mortality 22.6%), 10 within the first 48 hours due to associated vascular injury. In the 52 patients surviving beyond 48 hours, there were 19 patients with injuries to the main pancreatic duct and 33 with parenchymal injuries only. Pancreatic resection was carried out for all patients with ductal injury except for one, who later required distal pancreatectomy for pseudocyst and pancreatic fistula. Significant pancreatic fistulae developed in five patients, three in patients treated by drainage and two in patients treated by resection. The incidence of fistula formation was significantly higher for drainage versus resection in the patients with ductal injuries. The incidences of other complications were not affected by type of pancreatic injury, associated injuries, or method of management. We conclude that the majority of deaths in patients with penetrating pancreatic trauma are due to associated organ or vascular injuries. Appropriate management of the pancreatic injury can reduce the long-term complications. These results support treating patients with suspected ductal injuries by appropriate resection. Drainage should probably be sufficient for most nonductal pancreatic injuries.

Abdominal Abscess↗
PubMed1997

The effect of oxygen delivery-directed resuscitation on splanchnic and hepatic oxygen transport after hemorrhagic shock.

BACKGROUND: Gut and hepatic dysfunction, during and after hypovolemic shock, have been implicated as causative mechanisms in the development of multiple system organ failure in the trauma patient. Current techniques of assessment of perfusion only detect changes in systemic oxygen transport. We designed an animal model that can measure changes in oxygen transport in the liver and gut during hypovolemic shock and resuscitation. MATERIALS AND METHODS: Animals were hemorrhaged to a mean arterial pressure (MAP) of 60 mm Hg and maintained at 60 mm Hg for 60 min. Animals were then assigned to one of three groups. Group I served as nontreatment controls. Group II received shed blood and saline in sufficient volumes to restore MAP to baseline. Group III animals were resuscitated with shed blood, saline, and donor blood to restore systemic oxygen delivery to the preshock value. RESULTS: The animals resuscitated to their baseline systemic oxygen delivery, Group III, had significantly higher systemic, hepatic, and splanchnic oxygen delivery than the remaining groups. In addition, Group III had higher oxygen consumption, portal flow, and hepatic artery flow than the blood pressure-directed group, Group II. The decrease in oxygen extraction ratio in the gut and liver was significantly greater in Group III than in Group II. CONCLUSIONS: These data show that hepatic and gut vascular beds are better perfused when resuscitation from hemorrhage is guided by systemic oxygen transport measurements compared to resuscitation guided by blood pressure.

Animals↗
PubMed1997

Management outcomes in splenic injury: a statewide trauma center review.

OBJECTIVE: Clinical pathways now highlight both observation and operation as acceptable initial therapeutic options for the management of patients with splenic injury. The purpose of this study was to evaluate treatment trends for splenic injury in all North Carolina trauma centers over a 6-year period. METHODS: Splenic injuries in adults over a 6-year period (January 1988-December 1993) were identified in the North Carolina Trauma Registry using ICD-9-CM codes. Patients were divided into four groups by method of management: 1) no spleen operation, 2) splenectomy, 3) definitive splenorrhaphy, and 4) splenorrhaphy failure followed by splenectomy. The authors examined age, mechanism of injury, admitting blood pressure, and severity of injury by trauma score and injury severity score. SUMMARY BACKGROUND DATA: Comparisons were made between adult (17-64 years of age) and geriatric (older than 65 years of age) patients and between patients with blunt and penetrating injury. Resource utilization (length of stay, hospital charges) and outcome (mortality) were compared. RESULTS: One thousand two hundred fifty-five patients were identified with splenic injury. Rate of splenic preservation increased over time and was achieved in more than 50% of patients through nonoperative management (40%) and splenorrhaphy (12%). Splenorrhaphy was not used commonly in either blunt or penetrating injury. Overall mortality was 13%. Geriatric patients had a higher mortality and resource utilization regardless of their mechanism of injury or method of management. CONCLUSIONS: Nonoperative management represents the prevailing method of splenic preservation in both the adult and geriatric population in North Carolina trauma center hospitals. Satisfactory outcomes and economic advantages accompany nonoperative management in this adult population.

Adult↗
PubMed1997

Cardiac preload, splanchnic perfusion, and their relationship during resuscitation in trauma patients.

INTRODUCTION: Low gastric intramucosal pH (pHi) after shock resuscitation is associated with organ dysfunction and death in trauma patients. However, the relationship between hemodynamic performance, global oxygen transport, and pHi is unclear. Our purpose was to evaluate the relationship between intravascular volume status, splanchnic hypoperfusion, and outcome after shock resuscitation in trauma patients. DESIGN/SETTING: Cohort study of 79 consecutive critically ill patients at a Level I trauma center stratified by normal (NORM, > or = 7.32) or low (LOW, < 7.32) pHi when lactate normalized (< 2.2 mmol/L). MAIN OUTCOME MEASURES: Differences during resuscitation in mean values of right ventricular end-diastolic volume index (RVEDVI), pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, and oxygen consumption index. The incidence of multiple organ failure and death in the NORM and LOW groups were analyzed via odds ratio and chi 2. RESULTS: Patients in the NORM group (n = 45) had a lower incidence of multiple organ failure (4 of 45 vs. 11 of 34, odds ratio 5.0, p < 0.01) and death (5 of 45 vs. 11 of 34, odds ratio 3.8, p < 0.05) than patients in the LOW group (n = 34). NORM patients had a higher initial RVEDVI (116 +/- 31 vs. 95 +/- 25 mL/m2, p < 0.001) and maintained a significantly higher RVEDVI (114 +/- 27 vs. 97 +/- 17 mL/m2, p = 0.003) throughout resuscitation than the LOW group did. There were no differences in the other studied variables. CONCLUSIONS: Supranormal levels of preload during shock resuscitation are associated with better outcome. Maintaining a RVEDVI higher than 100 mL/m2 during shock resuscitation may be of benefit in critically injured patients.

Adult↗
PubMed1997

Clinical application of ventricular end-systolic elastance and the ventricular pressure-volume diagram.

The ability to clinically assess myocardial contractility in a load-independent fashion facilitates the selection of appropriate inotropes, when needed, during shock resuscitation. Within the framework of the ventricular pressure-volume diagram, the slope of the ventricular end-systolic pressure-volume relationship (expressed as ventricular end-systolic elastance, Ees), has been shown to accurately reflect ventricular inotropic state, and to be insensitive to loading conditions. It has not, however, been widely used at the bedside. Our goal was to evaluate the clinical utility of Ees and the ventricular pressure-volume diagram as bedside methods of hemodynamic assessment. We performed a prospective study of 123 hemodynamic interventions in 100 trauma patients during shock resuscitation in which contractility (Ees), preload (left ventricular end-diastolic volume index), and afterload (effective arterial elastance) were calculated before and after addition of inotropes, fluid bolus, and afterload reduction. Mean values of each variable were compared before and after each type intervention using the paired t test. The ventricular pressure-volume diagram was used to predict changes in the studied variables, and the experimental results were compared with predicted changes. Ees (mmHg/mL/m2) increased significantly with inotropes (4.7 +/- 3.2 to 10 +/- 8.7, p < .0001), but was not affected by clinically significant fluid administration (7.0 +/- 4.7 to 8.3 +/- 8.0, p = .10) or afterload reduction (9.6 +/- 5.2 to 9.2 +/- 4.7, p = .72). Left ventricular end-diastolic volume index (mL/m2) improved with fluid administration (54 +/- 8.9 to 62 +/- 9.8, p < .0001) and effective arterial elastance (mmHg/mL/m2) decreased with afterload reduction (3.3 +/- .9 to 2.6 +/- .7, p < .0001). We conclude that Ees is a load-independent measure of contractility, which is measurable at the bedside. The pressure-volume diagram is a useful method of monitoring hemodynamic changes associated with interventions during shock resuscitation.

Adult↗
PubMed1996

Infant survival after cesarean section for trauma.

HYPOTHESIS: Emergency cesarean sections in trauma patients are not justified and should be abandoned. SETTING AND DESIGN: A multi-institutional, retrospective cohort study was conducted of level 1 trauma centers. METHODS: Trauma admissions from nine level 1 trauma centers from January 1986 through December 1994 were reviewed. Pregnant women who underwent emergency cesarean sections were identified. Demographic and clinical data were obtained on all patients undergoing a cesarean section. Fetal distress was defined by bradycardia, deceleration, or lack of fetal heart tones (FHTs). Maternal distress was defined by shock (systolic blood pressure < 90) or acute decompensation. Statistical analyses were performed. RESULTS: Of the 114,952 consecutive trauma admissions, more than 441 pregnant women required 32 emergency cesarean sections. All were performed for fetal distress, maternal distress, or both. Overall, 15 (45%) of the fetuses and 23 (72%) of the mothers survived. Of 33 fetuses delivered, 13 had no FHTs and none survived. Twenty infants (potential survivors) had FHTs and an estimated gestational age (EGA) of greater than or equal to 26 weeks, and 75% survived. Infant survival was independent of maternal distress or maternal Injury Severity Score. The five infant deaths in the group of potential survivors resulted from delayed recognition of fetal distress, and 60% of these deaths were in mothers with mild to moderate injuries (Injury Severity Score < 16). CONCLUSIONS: In pregnant trauma patients, infant viability is defined by the presence of FHTs, estimated gestational age greater than or equal to 26 weeks. In viable infants, survival after emergency cesarean section is acceptable (75%). Infant survival is independent of maternal distress or Injury Severity Score. Sixty percent of infant deaths resulted from delay in recognition of fetal distress and cesarean section. These were potentially preventable. Given the definition of fetal viability, our initial hypothesis is invalid.

Adolescent↗
PubMed1996

Thoracic aorta injuries: management and outcome of 144 patients.

Rupture of the thoracic aorta from blunt injury is often lethal. Methods of operative repair vary, based on the surgeon's preference and circumstances. The primary hypothesis of this study was that operative management choices would correlate with outcome. Data on demographics, injury mechanism, initial evaluation, diagnostic procedures, operative treatment, and outcome were obtained from chart review at the state's eight trauma centers. Rates of paraplegia and survival were compared for different methods of operative repair. Of 63,507 hospitalized trauma patients, 144 patients sustained thoracic aortic injury (incidence = 0.23%). Sixty-four died (44.1%), most of whom died in the emergency department (26) or the operating room (12). Eighty-six patients had complete operative data for analysis, including cross-clamp time and methods of repair. No patient in the group with a cross-clamp time of less than 35 minutes developed paraplegia (p = 0.02). For the patients with longer cross-clamp times, 6 of 14 patients (42.9%) undergoing clamp and sew repair developed paraplegia, as compared to 2 of 37 patients (5.4%) repaired on bypass (p = 0.005). This study suggests that the rate of paraplegia after repair of thoracic aortic injury can be minimized with short cross-clamp times or the use of bypass when long cross-clamp times can be anticipated.

Adolescent↗
PubMed1996

Acid-induced laryngospasm in a canine model.

A canine model was used to investigate the efferent laryngeal responses to stimulation by topically applied acid and pepsin. Five adult mongrel dogs were studied. Electromyographic recordings from the thyroarytenoid muscle were measured with hooked-wire electrodes as an acid solution (normal saline/hydrochloric acid at pH 6.0, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, and 1.0) was sequentially instilled into the larynx. Laryngospasm (tonic, sustained contraction of the thyroarytenoid muscle) occurred in all animals at pH 2.5 to 2.0 or less. Control substances such as neutral pH isotonic saline, hypotonic saline, hypertonic saline, water, and pepsin alone failed to produce laryngospasm. Next, solutions containing both acid (in the same pH range) and pepsin were tested. The laryngeal responses were similar to those of acid alone. The superior laryngeal nerves were sectioned bilaterally and the above experiments repeated. None of the test solutions produced laryngospasm; however, when capsaicin (1%) was instilled into the subglottis, laryngospasm occurred. Thus, chemoreceptors in the subglottis (supplied by the recurrent laryngeal nerves) appear to be responsive to capsaicin stimulation but not to acid stimulation. The data suggest that pH-sensitive chemoreceptors in the canine larynx cause laryngospasm (when the pH of the test solution is 2.5 or less) and that these acid receptors are supplied by the superior laryngeal nerves.

Animals↗
PubMed1996

Volumetric assessment of preload in trauma patients: addressing the problem of mathematical coupling.

The availability of the volumetric thermodilution pulmonary artery catheter allows preload assessment based on ventricular volume rather than pressure. This technique has been shown clinically to be a better measure of preload than the pulmonary artery occlusion pressure (PAOP). Critics of the technique argue that the use of thermodilution to measure cardiac output (CO) accounts for the better correlation between right ventricular end-diastolic volume (RVEDV) and CO than PAOP and CO, since stroke volume derived from the CO is a common term to both RVEDV and CO. Previous studies have attempted mathematical corrections for this coupling effect, but direct comparisons using a nonthermodilution measure of CO have not been reported. Our objective was to evaluate the importance of mathematical coupling between RVEDV and CO by assessing the ability of RVEDV to predict CO measured by thermodilution (COTH) compared with CO simultaneously determined by the Fick principle (COFICK). We performed a prospective study of 53 consecutive trauma patients admitted to a Level I trauma center between 10/1/94 and 6/1/95 who received a volumetric pulmonary artery catheter. Using linear regression analysis, RVEDV and PAOP were correlated with simultaneous measurements of both COFICK determined via indirect calorimetry and COTH. Fisher's z-transformation was used to evaluate the correlation coefficients for significant differences (p < .05). The correlation coefficients for RVEDV vs. COTH and RVEDV vs. COFICK were similar (.48 vs. 0.45, p = .76). There was a significant correlation between COTH and COFICK (r = .74, p < .001). RVEDV was significantly better than PAOP at predicting both COTH (p < .001) and COFICK (p = .04). Multivariate regression analysis confirmed that RVEDV was the only estimate of preload which was significantly related to CO. We conclude that mathematical coupling does not have a significant clinical effect on the relationship between RVEDV and CO.

Blood Pressure↗
PubMed1996

Pneumonia in intubated trauma patients. Microbiology and outcomes.

To describe the epidemiology of nosocomial pneumonia in trauma patients and its impact on outcome, we performed a retrospective case-control analysis. Quantitative bronchoscopic cultures were collected from 62 intubated patients with suspected pneumonia. Patients with proven pneumonia had higher abdominal injury scores. Those with bronchoscopy-negative pneumonitis were older. Age and injury severity were used to match two controls to each case. The incidence of pneumonia was 5.8% Streptococci and Hemophilus were common pathogens, but gram-negative rods were isolated more frequently after lengthier intubation. Polymicrobial infections were common. There were no serious complications of bronchoscopy, and culture results often led to antibiotic therapy. No excess mortality could be attributed to pneumonia. Patients with pneumonia and those with bronchoscopy-negative pneumonitis required prolonged care compared with others (p < 0.05). Patients with pneumonia did not receive excess ventilation or hospitalization but incurred hospital charges 1.5 times higher than controls (p = 0.04). Pneumonia was confirmed in less than half of those suspected of having it on the basis of clinical findings. When severity of injury was considered, pneumonia was associated with neither increased mortality nor increased hospital care, but the clinical features suggesting respiratory infection identified trauma patients requiring prolonged hospitalization and incurring higher costs.

Adult↗
PubMed1996

Pharmacodynamics and pharmacokinetics of milrinone administration to increase oxygen delivery in critically ill patients.

OBJECTIVES: The positive inotropic and vasodilator actions of phosphodiesterase (PDE) inhibitor drugs may offer therapeutic alternatives to beta-agonists in critically ill patients. We hypothesized that milrinone administration would increase cardiac index (CI) and oxygen delivery (Do2) in ICU patients, and that a pharmacokinetic model previously developed in cardiac surgery patients may be used to predict milrinone plasma concentrations in a medical-surgical ICU population. SETTING: ICU in two tertiary-care, university medical centers. DESIGN AND INTERVENTIONS: A prospective, open-label, multicenter, dose-escalating study in three successive groups of eight ICU patients who received a 10-min loading dose of milrinone (25 micrograms/kg [LOW], 50 micrograms/kg [MED], and 75 micrograms/kg [HIGH]). In addition, all patients then received a milrinone infusion of 0.5 microgram/kg/min for 1 h. MEASUREMENTS: Hemodynamic measurements included heart rate (HR); mean arterial, pulmonary artery, central venous, and pulmonary artery occlusion pressures; and thermodilution cardiac output. Oxygen transport indexes included arterial and venous blood oxygen tensions to determine Do2 and oxygen consumption (Vo2). Data were analyzed by univariate repeated measures analysis of covariance, with baseline values utilized as covariate regressors. RESULTS: Twenty-four adult ICU patients 20 to 84 years of age completed the study. The three groups did not differ, except that the patients in the MED group were significantly older (67 +/- 4 years, mean +/- SEM) compared with either the patients in the LOW (48 +/- 7 years) or HIGH (47 +/- 6 years) group. While HR did not change in the LOW group (90 +/- 4 to 93 +/- 3 beats/min), HR increased significantly in the HIGH group (94 +/- 5 to 112 +/- 8 beats/min) (baseline to 60 min infusion time points). All milrinone doses increased both CI and Do2. At the end of the 10-min loading dose, CI increased 0.3 L/min/m2 in the LOW group, 1.1 L/min/m2 in the MED group, and 0.9 L/min/m2 in the HIGH group. Do2 increased 8% in the LOW group, 33% in the MED group, and 23% in the HIGH group, similar to the changes in CI. Mixed venous oxygen saturation increased 3 to 5% during the 10-min loading dose of milrinone. During this same time period, mean arterial pressure decreased 6 to 16% and pulmonary artery pressures decreased 9 to 15%. Peak plasma milrinone concentrations increased as a function of the loading dose (159 +/- 9 ng/mL in the LOW group, 302 +/- 33 ng/ml in the MED group, and 411 +/- 45 ng/mL in the HIGH group). However, milrinone concentrations were similar in all three groups after the 1-h infusion; 113 +/- 14 ng/ml (LOW), 147 +/- 22 ng/mL (MED), and 119 +/- 14 ng/ml (HIGH). In all patients with final plasma milrinone concentrations greater than 100 ng/mL (15/23), the CI increased by at least 0.4 L/min/m2 (range, 0.4 to 1.8 L/min/m2). CONCLUSIONS: Our study confirms that a milrinone loading dose of 50 micrograms/kg/min followed by an infusion of 0.5 microgram/kg/min achieves adequate plasma concentrations of 100 ng/mL or greater, which significantly increases both CI and Do2. In addition, a previously established pharmacokinetic model of milrinone disposition is confirmed in this mixed ICU population.

Adult↗
PubMed1995

Does oxygen delivery-directed resuscitation worsen outcome of head injured patients with multisystem injuries?

There is concern that oxygen delivery-directed resuscitation in patients with multiple trauma, including severe head injury, may worsen neurologic recovery. To study this, we retrospectively examined 31 patients admitted over an 18-month period who met the inclusion criteria of having suffered blunt trauma, were between 15 and 65 years of age, had an admission Glasgow coma scale of < or = 8, intact corneal and gag reflexes, and extracranial injury with an Abbreviated Injury score of > or = 3. All patients were placed on intracranial pressure monitors. In comparing the 14 patients whose resuscitation was guided by oxygen delivery (DO2) with the 17 who were resuscitated by standard fluid restriction (FR), we found that despite the DO2 group's having received a significantly greater volume of resuscitation fluids in the first 48 hours after injury, there was no difference in the neurologic recovery between the two groups.

Abbreviated Injury Scale↗