摘要:

Objective:To determine factors influencing the individual effects of blood transfusions regarding oxygen delivery and consumption.Design:Chart review.Setting:A university hospital cardiosurgical intensive care unit.Patients:Sixty-seven patients with 170 transfusion events evaluated.Interventions:Blood transfusion.Measurements and Main Results:Measurements were performed before and after a blood transfusion, separated by 302 ± 13 mins (mean ± SEM). The individual increase in cardiac index resulting from a blood transfusion was inversely related to cardiac index before transfusion (p< .001), oxygen delivery index before transfusion (p< .001), and oxygen consumption index before transfusion (p< .001). The individual increase in oxygen delivery index was inversely related to oxygen consumption index before transfusion (p< .001). The individual increase in oxygen consumption index was inversely related to oxygen consumption index before transfusion (p< .001). Individual changes in cardiac index, oxygen delivery index, and oxygen consumption index were not significantly related to preoperative ejection fraction (25%-87%), age (32-81 yrs), and pretransfusion hemoglobin concentration (5.0-11.8 g/dL).Conclusion:In adult patients after cardiovascular surgery, oxygen delivery- and oxygen consumption-related variables predict the individual response to blood transfusions better than do patient characteristics such as preoperative ejection fraction, age, and pretransfusion hemoglobin concentration. Including oxygen delivery and oxygen consumption, variables into the transfusion decision, thus, may enable a more individual use of allogeneic blood in specific situations.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:This study was conducted to stimulate respiratory muscles by functional magnetic stimulation (FMS) of the spinal nerves (T1-L5) to obtain maximum expiratory function.Design:A prospective before and after trial.Setting:Functional Magnetic Stimulation Laboratory, Spinal Cord Injury Service, VA Palo Alto Health Care System, Palo Alto, CA.Participants:Twelve normal able-bodied subjects.Intervention:A commercially available magnetic stimulator with a round magnetic coil (MC) was used. Respiratory muscle activation was achieved by placing the MC at each spinous process ranging from T1 to L5 vertebral levels.Main Outcome Measure:The planned major outcome was to determine the optimal MC placement for producing maximal expiratory pressure (MEP) and expiratory reserve volume (ERV) by FMS. These measurements were compared with the subjects' voluntary maximal efforts. A profile with varying stimulation intensities was also obtained in select individuals for determining the highest expiratory pressure.Results:Stimulation at the T9 spinal level resulted in the highest mean MEP and ERV. Stimulation between T8 and L5 produced similar MEP and ERV as obtained from the T9 MC placement. The mean maximum MEP and ERV produced by FMS were 76.8 ± 6.4 cm H2O (7.52 ± 0.62 kPa) and 1.28 ± 0.15 L, which were 67% and 79% of the subjects' voluntary maximal efforts, respectively. A stimulation intensity of 80% resulted in the highest expiratory pressure.Conclusion:FMS of lower thoracic and lumbar regions produced significant expiratory pressures and volumes. FMS of the expiratory muscles may prove to be a valuable technique for restoring cough in patients with spinal cord injury or other neurologic diseases, and in critical care or perioperative settings.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To evaluate the reliability of whole-body impedance cardiography in the measurement of cardiac output after coronary artery bypass grafting operation in comparison with the thermodilution method.Design:Prospective, consecutive sampling.Patients:A total of 82 patients undergoing coronary artery bypass surgery were investigated. In a group of 41 patients who were intubated, cardiac output measurements were taken simultaneously with whole-body impedance cardiography and the thermodilution method within the first 3 hrs after the operation (early intensive care unit [ICU] period). In another group of 41 patients, the measurements were taken before the operation and in the second 12 hrs after cardiac surgery (late ICU period).Interventions:None.Measurements and Main Results:The agreement between the thermodilution and whole-body impedance cardiography cardiac output measurements was good before the operation, bias 0.04 ± 1.64 L/min (n = 41), and in the late ICU period, bias 0.00 ± 1.84 L/min (±2 SD) (n = 41). The results were within 20% in 81%-85% of the cases. The agreement was satisfactory in the early ICU period, bias 0.38 ± 2.74 L/min (n = 41). It was presumed that thermal instability of the patients was one possible source of measurement errors in the thermodilution method, causing reduced agreement between the methods in this period. The repeatability values (rv = 2.83 × SDs) for whole-body impedance cardiography were 0.44 L/min before the operation, 0.30 L/min in the early ICU period, and 0.65 L/min in the late ICU period, being significantly better than for the thermodilution method (0.79, 0.51, and 1.11 L/min, respectively) in all phases of the investigation (p< .001). The agreement between the thermodilution method and whole-body impedance cardiography is similar to reported comparisons between invasive methods in analogous settings.Conclusions:Whole-body impedance cardiography reliably measures cardiac output in patients after coronary artery bypass grafting operation. The excellent repeatability of whole-body impedance cardiography enhances the value of the method in continuous monitoring of patients after the operation.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:Auto-positive end-expiratory pressure (auto-PEEP) is a physiologic phenomenon defined as the positive alveolar pressure that exists at the end of expiration. Normally, the alveolar pressure is near zero at the end of expiration. However, certain ventilatory and/or physiologic paradigms can cause the development of auto-PEEP during cardiopulmonary resuscitation (CPR). Auto-PEEP has a detrimental cardiovascular effect similar to that of positive end-expiratory pressure that is intentionally applied to the ventilatory circuit in a mechanically ventilated patient. The connection between auto-PEEP and its cardiovascular effects, however, may go undetected. In this study, the effect that ventilatory factors have on auto-PEEP in a simulation of patients with lung disease undergoing CPR was delineated.Design:A case control study.Setting:Laboratory of a university hospital anesthesia department.Subjects:A baseline quantification of breathing patterns that occur during CPR was obtained by recording observed respiratory rate and relative tidal volume during treatment of in-hospital cardiac arrests.Measurements and Main Results:A test lung was set up to mimic a series of different airway resistances and lung compliances as would be seen in different types of pulmonary pathology. A sensitivity analysis was performed on each of the factors of respiratory rate, tidal volume, and inspiratory/expiratory ratio as to the effect each of these factors has on the development of auto-PEEP. Our study suggests that in various combinations of airway resistances and lung compliances, auto-PEEP can be generated to substantial levels depending on the methods of ventilation performed.Conclusion:We conclude from our findings that ventilation techniques during CPR may need to be altered to avoid the development of what may be a hemodynamically significant level of auto-PEEP.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To determine whether treatment with patient-controlled analgesia (PCA) alone or in combination with nonsteroidal anti-inflammatory drugs can prevent postoperative pulmonary complications after cardiac surgery, when compared with conventional nurse-controlled analgesia.Design:Randomized controlled trial.Setting:University Medical Center.Patients:A total of 120 patients undergoing elective coronary artery bypass grafting.Interventions:After extubation of the trachea, 120 patients were randomly allocated to three different methods of postoperative pain relief for 72 hrs. In group 1, patients received PCA with a bolus of 1.5 mg piritramide combined with a 10-min lockout interval. Group 2 patients were treated with a combination of PCA and administration of nonsteroidal anti-inflammatory drugs prescribed three times per day. Patients of group 3 received conventional nurse-controlled analgesia. Postoperative assessment included daily visual analog pain scoring (VAS) and chest radiographs. All chest radiographs were graded for the extent of atelectasis by a radiologist blinded as to treatment using a scale from 0 to 9 for each of the three lung fields of the right and left lungs.Measurements and Main Results:Chest radiograph atelectasis scores and VAS values were similar among the three groups on the first and second days. On the third day, the chest radiograph atelectasis scores of the left lower and the right middle lung field were significantly better in the groups treated with PCA alone (4.7 ± 3.0; 0.3 ± 1.0) and in combination with nonsteroidal anti-inflammatory drugs (3.9 ± 1.1; 0.4 ± 1.2) than in the control group (5.5 ± 3.1; 0.8 ± 1.8). Furthermore, on the third day, the VAS values for maximum pain were higher in the control group (42.6 ± 19.7) compared with the VAS values in the two groups with PCA (32.2 ± 17.9 and 34.5 ± 21.0).Conclusions:PCA significantly decreases postoperative pulmonary atelectasis in patients after coronary artery bypass grafting when compared with nurse-controlled analgesia. In addition, patients treated with PCA experienced a higher quality of analgesia. We therefore conclude that treatment with PCA may reduce respiratory complications after coronary artery bypass grafting.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To compare the efficacy, safety, and cost of fixed-dose low-molecular-weight heparin (dalteparin) with adjusted-dose unfractionated heparin as anticoagulant for continuous hemofiltration.Design:Prospective, randomized, controlled clinical trial.Setting:University-affiliated adult intensive care unit.Patients:All patients requiring continuous hemofiltration for acute renal failure or systemic inflammatory response syndrome (SIRS) were eligible. Fifty-seven patients were enrolled. Eleven were excluded, seven because of major protocol violations and four died before hemofiltration.Interventions:Patients received continuous venovenous hemodialysis with filtration with prefilter replacement at 500 mL/hr and countercurrent dialysate at 1000 mL/hr. Filters were primed with normal saline containing anticoagulant. Dalteparin-treated patients received a commencement bolus of 20 units/kg and a maintenance infusion at 10 units/kg/hr. Heparin-treated patients received a commencement bolus of 2000-5000 units and a maintenance infusion at 10 units/kg/hr, titrated to achieve an activated partial thromboplastin time in the patient of 70-80 secs.Measurements and Main Results:The primary outcome measure-time to failure of the hemofilter-was compared using survival analysis. Twenty-two patients (13 with acute renal failure and nine with SIRS; total, 41 filters) were randomized to heparin. Twenty-five patients (16 with acute renal failure and nine with SIRS; total, 41 filters) were randomized to dalteparin. Mean (SE) activated partial thromboplastin time in the heparin group was 79 (4.3) secs. Mean (SE) anti-factor-Xa activity in the six patients given dalteparin who were assayed was 0.49 (0.07). Mean (SE) prehemofiltration platelet count was 225 (35.5) × 109for heparin and 178 (18.1) × 109for dalteparin (p= .24, unpaired Student'st-test). Mean (SE) prehemofiltration hemoglobin was 11.4 (0.61)g/dL for heparin and 10.6 (0.38) g/dL for dalteparin (p= .31, unpaired Student'st-test).Primary Outcome:There was no significant difference in the time to failure between the two groups (p= .75, log rank test). For dalteparin, Kaplan-Meier (K-M) mean (SE) time to failure of the hemofilter was 46.8 (5.03) hrs. For heparin, K-M mean (SE) time to failure was 51.7 (7.51) hrs. The 95% CI for difference in mean time to failure was −13 to 23 hrs. The power of this study to detect a 50% change in filter life was >90%.Secondary Outcomes:Mean (SE) reduction in platelet count during hemofiltration was 63 (25.8) × 109for heparin and 41.8 (26.6) × 109for dalteparin (p= .57, unpaired Student'st-test). Eight patients given dalteparin and four patients given heparin had screening for heparin-induced thrombocytopenia; three of the dalteparin patients and one of the heparin patients were positive (p= 1.0, Fisher's exact test). There were three episodes of trivial bleeding and two episodes of significant bleeding for dalteparin, and there were three episodes of trivial bleeding and four episodes of significant bleeding for heparin (p= .53, chi-square test). The mean (SE) decrease in hemoglobin concentration during hemofiltration was 0.51 (0.54) g/dL for heparin and 0.28 (0.49) g/dL for dalteparin (p= .75, unpaired Student'st-test). The mean (SE) packed-cell transfusion volume during hemofiltration was 309 (128) mL for heparin and 290 (87) mL for dalteparin (p= .90, unpaired Student'st-test). Daily costs, including coagulation assays, of hemofiltration were approximately 10% higher using dalteparin than with heparin.Conclusions:Fixed-dose dalteparin provided identical filter life, comparable safety, but increased total daily cost compared with adjusted-dose heparin. Unfractionated heparin remains our anticoagulant of choice for continuous hemofiltration in intensive care.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To evaluate and compare the factors associated with pulmonary edema in cardiac tamponade and myocardial ischemia.Design:Prospective, controlled laboratory study.Setting:Animal research laboratory of a university hospital.Subjects:Fourteen anesthetized dogs.Intervention:Extravascular lung water (EVLW) was measured with thermal indocyanine green dye double-indicator dilution method and hemodynamic indices were determined by the pulmonary artery flotation catheter. Seven dogs were used in the tamponade model, and seven other dogs were used in the myocardial ischemia model. Furthermore, ten dogs were dedicated to measure plasma colloid osmotic pressure (COP) and blood gas analysis during cardiac tamponade and myocardial ischemia.Measurements and Main Results:Mean right atrial pressure (MRAP) (7→10 mm Hg), pulmonary capillary wedge pressure (PCWP) (10→13 mm Hg), and EVLW (5.4→10.1 mL/kg) increased during tamponade, but all of these indices returned to the control level after release of tamponade (MRAP, 7 mm Hg; mean PCWP, 11 mm Hg; mean EVLW, 5.2 mL/kg). Myocardial ischemia caused increases in PCWP (10→14 mm Hg) and EVLW (5.6→9.6 mL/kg). Although PCWP returned to the control level, EVLW remained elevated (9.2 mL/kg) after reperfusion. EVLW had good correlations with MRAP (r2= .64,p< .05) and PCWP (r2= .62,p< .05) during cardiac tamponade. Despite a fair correlation between EVLW and PCWP during ischemia (r2= .73,p< .05), EVLW was not related to PCWP after reperfusion. COP decreased during myocardial ischemia and at the reperfusion period, but there was no significant change in COP in the cardiac tamponade model.Conclusions:In contrast to a close relation between hydrostatic pressure and EVLW in cardiac tamponade, hydrostatic pressure was not a determinant of pulmonary edema during the reperfusion period after myocardial ischemia.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:Hypoxia may alter the neuroendocrine control of catabolic and anabolic states early in postnatal life by modulating the growth hormone-insulin-like growth factor-I (GH-IGF-I) system. We wondered: a) to what extent hypoxia effects on the GH-IGF-I axis differed from those of food deprivation alone; and b) whether administration of exogenous GH mitigates alterations of the GH-IGF-I axis caused by hypoxia or food restriction.Design:Prospective laboratory investigation using nursing dams and suckling pups. Experimental groups included: a) room air control subjects; b) hypoxia-exposed subjects (FIO2, 0.12); or c) room air breathing subjects whose dam food intake was matched to that of hypoxic dams. Half of the pups in each group were administered rat GH (100 μg subcutaneously each day), and the remaining received vehicle alone. The intervention lasted 18 days.Setting:Research laboratory in a university medical center.Subjects:Twelve litters of 1-day-old Sprague-Dawley rat pups and nursing dams.Interventions:Hypoxia exposure, food restriction, GH administration.Measurements and Main Results:By the end of the study, body weights of the hypoxic and pair-fed pups were significantly lower than the weights of control animals (p< .001 for both groups), and weight gain correlated significantly with total dam food consumption (r2= .85,p< .0001). GH administration increased weight gain only in hypoxic animals (p< .001) but it increased tail lengths significantly in both hypoxic and control pups (p< .001). Serum IGF-I levels in both hypoxic and pair-fed pups were significantly lower than in control animals. Serum IGF-binding protein-3 (IGFBP-3) was significantly lower in the hypoxic compared with the control animals. GH administration resulted in significant increases in serum levels of IGFBP-3 in both the control (p< .05) and the hypoxic (p< .01) pups compared with their vehicle-treated litter mates.Conclusions:Exogenous GH attenuates growth impairment associated with hypoxia but not with food restriction, and these effects may be mediated in part by IGFBP-3.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To study the changes in neuroautonomic regulation of heart rate and the effects of NG-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of nitric oxide synthase, on efferent sympathetic cardiac activity and blood pressure during hypovolemic shock. Hypotension during hypovolemic shock may be attributable, in part, to the failure of neuroautonomic regulation of heart rate and blood pressure. In addition, the release of nitric oxide may contribute to hypotension through vasodilation and inhibition of efferent sympathetic activity.Design:Prospective, controlled trial.Setting:Experimental laboratory in a university hospital.Subjects:Seventeen anesthetized adult male New Zealand White rabbits.Interventions:The rabbits were divided into four groups: control (n = 3), control plus L-NAME (n = 5), hypovolemic (n = 4), and hypovolemic plus L-NAME (n = 5). Hypovolemic rabbits were bled of 10% of their circulating blood volume (85 mL/kg) every 10 mins until 30% cumulative hypovolemia was reached. Rabbits received either three doses of saline 1 mL/kg every 10 mins or L-NAME 10 mg/kg in 1 mL/kg of saline solution administered after each hemorrhage for a total of three doses. Changes in heart rate, respiratory rate, mean arterial pressure, plasma catecholamine levels, and heart rate power spectra were recorded every 10 mins during serial hypovolemia and during a 30-min recovery period.Measurements and Main Results:During hypovolemic shock there was a decrease in log low-frequency heart rate power (p= .001) and in systolic (p= .003), diastolic (p< .001), and mean (p< .001) blood pressures compared with control rabbits. Treatment with L-NAME during hypovolemia resulted in increased log low-frequency heart rate power (p= .03) and systolic (p= .01), diastolic (p= .007), and mean (p= .009) blood pressures compared with hypovolemic rabbits who received saline placebo.Conclusions:We found that treatment with L-NAME increased efferent sympathetic cardiac activity and mean arterial pressure during hypovolemic shock compared with control rabbits. We conclude that L-NAME may blunt hypotension during hypovolemic shock by inhibiting nitric oxide synthase and may act to restore neuroautonomic cardiovascular reactivity. Spectral analysis of heart rate variability may allow for insights into the pathophysiology of shock and provide a means of monitoring the neuroautonomic cardiovascular response to therapy.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:Incubation of enterocytic monolayers with interferon (IFN)-γ increases nitric oxide (NO) production and permeability, but NO synthesis inhibitors ameliorate the development of IFN-γ-induced hyperpermeability. Induction of inducible nitric oxide synthase (iNOS), an isoform of the enzyme responsible for NO biosynthesis, is often enhanced by the synergistic effects of multiple cytokines. Moreover, many of the cytopathic effects of NO are mediated by peroxynitrite, which is produced by the reaction of NO with superoxide radical anion. In the present study, we sought to determine whether combinations of several proinflammatory cytokines, including IFN-γ, interleukin-1β, and tumor necrosis factor-α, have synergistic effects on the induction of iNOS expression and/or hyperpermeability to hydrophilic solutes in cultured enterocytic monolayers. We also assessed the effects of aminoguanidine (a relatively selective iNOS inhibitor), L-NG-monomethyl arginine (an isoform-nonselective NO synthase inhibitor), and Tiron (a superoxide radical anion scavenger) on the development of cytokine-induced hyperpermeability.Design:Caco-2 monolayers were incubated under control conditions or with IFN-γ, interleukin-1β, or tumor necrosis factor-α alone, pairwise combinations of these cytokines, or all three cytokines together (cytomix; CM). iNOS messenger RNA (mRNA) expression was assessed using Northern blot analysis. The permeability of Caco-2 monolayers growing on permeable supports in bicameral chambers was assessed by measuring the apical-to-basolateral flux of fluorescein disulfonic acid. The concentration of nitrate plus nitrite in culture supernatants, an indirect measure of NO production, was determined using the Griess reaction.Results:After 24 hrs of incubation, up-regulation of iNOS mRNA expression was evident only in cells exposed to IFN-γ-containing formulations. Expression of iNOS mRNA was far greater in cells incubated with CM than in cells treated with IFN-γ alone or either of the two-component IFN-γ-containing cytokine combinations. Compared with IFN-γ, CM resulted in a higher rate of NO production over 48 hrs of incubation. The permeability of Caco-2 monolayers increased by approximately six-fold and ∼20-fold after incubation for 48 hrs with IFN-γ alone and CM, respectively. The increase in permeability induced by incubation with CM was significantly ameliorated by the addition of aminoguanidine, L-NG-monomethyl arginine, or Tiron.Conclusions:IFN-γ-containing combinations of cytokines are potent inducers of iNOS in cultured enterocytic monolayers. Peroxynitrite may be an important mediator of cytokine-induced gut epithelial hyperpermeability.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID