Does intermittent mandatory ventilation correct respiratory alkalosis in patients receiving assisted mechanical ventilation?

One of the claimed advantages of intermittent mandatory ventilation (IMV) over assisted mechanical ventilation (AMV) (assist-control) is the avoidance or correction of acute respiratory alkalosis, ostensibly by allowing patients to achieve normal alveolar ventilation (VA) and PaCO2 through the function of an intact ventilatory drive. However, although respiratory alkalosis in patients being hyperventilated with controlled mechanical ventilation (CMV) can be corrected by a change to IMV, CMV is seldom appropriate for patients with acute respiratory failure, and whether IMV affects respiratory alkalosis in patients triggering the ventilator in the AMV mode has not previously been tested. We studied 26 patients with acute respiratory alkalosis (pH greater than or equal to 7.48) while receiving AMV. Measurements of arterial blood gases and CO2 production (VCO2), and calculation of VA, were performed after 30 min of AMV, repeated after 30 min of IMV at a mandatory rate one half the previous AMV rate, and then repeated again 30 min after a return to the original AMV settings. Mean arterial pH decreased slightly from 7.51 during AMV to 7.48 during IMV, and returned to 7.51 on resumption of AMV (p less than 0.05 for both changes); corresponding mean values for PaCO2 were 28.6, 29.7, and 27.5 mmHg, respectively. These changes were related to an increase in VCO2 during IMV as compared with AMV (p less than 0.05), without a significant alteration in VA. When the mandatory rate was further reduced during IMV from one half to one fourth the prior, triggered AMV rate in 10 patients, no additional reduction in pH occurred.(ABSTRACT TRUNCATED AT 250 WORDS)     

A randomized clinical trial of continuous aspiration of subglottic secretions in cardiac surgery patients

STUDY OBJECTIVES: To determine whether the application of continuous aspiration of subglottic secretions (CASS) is associated with a decreased incidence of ventilator-associated pneumonia (VAP). DESIGN: Prospective clinical trial. SETTING: Cardiothoracic ICU (CTICU) of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital. PATIENTS: Three hundred forty-three patients undergoing cardiac surgery and requiring mechanical ventilation in the CTICU. INTERVENTIONS: Patients were assigned to receive either CASS, using a specially designed endotracheal tube (Hi-Lo Evac; Mallinckrodt Inc; Athlone, Ireland), or routine postoperative medical care without CASS. RESULTS: One hundred sixty patients were assigned to receive CASS, and 183 were assigned to receive routine postoperative medical care without CASS. The two groups were similar at the time of randomization with regard to demographic characteristics, surgical procedures performed, and severity of illness. Risk factors for the development of VAP were also similar during the study period for both treatment groups. VAP was seen in 8 patients (5.0%) receiving CASS and in 15 patients (8. 2%) receiving routine postoperative medical care without CASS (relative risk, 0.61%; 95% confidence interval, 0.27 to 1.40; p = 0. 238). Episodes of VAP occurred statistically later among patients receiving CASS ([mean +/- SD] 5.6 +/- 2.3 days) than among patients who did not receive CASS (2.9 +/- 1.2 days); (p = 0.006). No statistically significant differences for hospital mortality, overall duration of mechanical ventilation, lengths of stay in the hospital or CTICU, or acquired organ system derangements were found between the two treatment groups. No complications related to CASS were observed in the intervention group. CONCLUSIONS: Our findings suggest that CASS can be safely administered to patients undergoing cardiac surgery. The occurrence of VAP can be significantly delayed among patients undergoing cardiac surgery using this simple-to-apply technique.     

气管导管气囊上滞留物引流预防呼吸功能不全危重患者医院获得性肺炎的研究

目的 观察气管导管气囊上可吸引滞留物对呼吸功能不全行气管切开的危重患者医院获得性肺炎(HAP)的发病、成本及预后的影响.方法 选择2004年5月至2006年5月中山大学附属东华医院重症监护病房(ICU)呼吸功能不全的气管切开危重患者120例.将其随机分为气囊上滞留物引流(subballonet secretion drainage,SSD)组60例和未引流组(对照组)60例,记录细菌培养的结果、发生医院内获得性肺炎的时间、气管切开气道开放时间、ICU住院时间.结果 SSD组痰液量较对照组明显减少(t=3.304,P<0.05),气囊上滞留物引流量每日达(53±9)mL/d,气囊上滞留物与下呼吸道病原体有一致性和相似的构成比(P>0.05);SSD组HAP发生率、气道开放时间、住ICU时间、总住院时间、患者最后转归等明显优于对照组.结论 持续气囊上滞留物引流可以明显降低ICU气管切开危重患者院内感染肺炎发生率,减少气道开放时间,减少ICU住院时间,降低总住院时间及病死率.     

GI complications in patients receiving mechanical ventilation

Mechanical ventilation (MV) can be lifesaving by maintaining gas exchange until the underlying disorders are corrected, but it is associated with numerous organ-system complications, which can significantly affect the outcome of critically ill patients. Like other organ systems, GI complications may be directly attributable to MV, but most are a reflection of the severity of the underlying disease that required intensive care. The interactions of the underlying critical illness and MV with the GI tract are complex and can manifest in a variety of clinical pictures. Incorporated in this review are discussions of the most prevalent GI complications associated with MV, and current diagnosis and management of these problems.     

A randomized trial of iloprost in patients with intermittent claudication

Prostanoids, which promote vasodilation and reduce platelet aggregation, have been proposed as candidate therapies for intermittent claudication due to peripheral arterial disease (PAD). However, studies of these medications have yielded inconsistent results. This study tested the hypothesis that iloprost, an oral prostacyclin analogue, would improve walking distance and quality of life in patients with intermittent claudication. The study was a multi-center, randomized, double-blind, placebo-controlled trial comparing three doses of oral iloprost (50 microg, 100 microg, or 150 microg twice daily), pentoxifylline, or placebo in 430 patients with intermittent claudication. The primary outcome measure was improvement in absolute claudication distance (ACD) after 6 months. Secondary outcomes included initial claudication distance and quality of life assessment. Placebo increased ACD by 3.3%, and iloprost increased peak ACD by 7.7%, 8.8% and 11.2% at the 50 microg, 100 microg, and 150 microg twice-daily doses, respectively (all insignificant relative to placebo). Pentoxifylline increased ACD by 13.9% relative to placebo (p = 0.039). Neither iloprost nor pentoxifylline enhanced quality of life. These results indicate that oral iloprost is not effective in improving exercise performance or quality of life in patients with PAD who have intermittent claudication.     

A multicenter randomized trial of computer-driven protocolized weaning from mechanical ventilation

RATIONALE AND OBJECTIVES: Duration of weaning from mechanical ventilation may be reduced by the use of a systematic approach. We assessed whether a closed-loop knowledge-based algorithm introduced in a ventilator to act as a computer-driven weaning protocol can improve patient outcomes as compared with usual care. METHODS AND MEASUREMENTS: We conducted a multicenter randomized controlled study with concealed allocation to compare usual care for weaning with computer-driven weaning. The computerized protocol included an automatic gradual reduction in pressure support, automatic performance of spontaneous breathing trials (SBT), and generation of an incentive message when an SBT was successfully passed. One hundred forty-four patients were enrolled before weaning initiation. They were randomly allocated to computer-driven weaning or to physician-controlled weaning according to local guidelines. Weaning duration until successful extubation and total duration of ventilation were the primary endpoints. MAIN RESULTS: Weaning duration was reduced in the computer-driven group from a median of 5 to 3 d (p=0.01) and total duration of mechanical ventilation from 12 to 7.5 d (p=0.003). Reintubation rate did not differ (23 vs. 16%, p=0.40). Computer-driven weaning also decreased median intensive care unit (ICU) stay duration from 15.5 to 12 d (p=0.02) and caused no adverse events. The amount of sedation did not differ between groups. In the usual care group, compliance to recommended modes and to SBT was estimated, respectively, at 96 and 51%. CONCLUSIONS: The specific computer-driven system used in this study can reduce mechanical ventilation duration and ICU length of stay, as compared with a physician-controlled weaning process.     

A descriptive evaluation of transfusion practices in patients receiving mechanical ventilation

STUDY OBJECTIVES: To characterize and compare transfusion practices in a broad sample of patients receiving mechanical ventilation (MV) and not receiving MV in the ICU. DESIGN: Retrospective subgroup analysis from the prospective, multicenter, observational CRIT study. SETTING: Two hundred eighty-four medical, surgical, or medical/surgical ICUs. PATIENTS: Critically ill adults.Main results: Of the 4,892 patients enrolled in the CRIT study, 60% were receiving MV on ICU admission or within 48 h after admission for a median of 4 days. Patients receiving MV had higher baseline APACHE (acute physiology and chronic health evaluation) II scores than patients not receiving MV (22.8 +/- 7.8 and 14.9 +/- 6.4, respectively [mean +/- SD]; p < 0.0001). Despite similar baseline hemoglobin levels (11.0 +/- 2.3 g/dL and 10.9 +/- 2.5 g/dL, p = 0.17), more patients receiving MV underwent transfusions (49% vs 33%, p < 0.0001), and they received significantly more RBCs than patients not receiving MV (p < 0.0001). The principal reason for transfusion in both groups was low hemoglobin level (78.4% and 84.6%, respectively); however, patients receiving MV had higher pretransfusion hemoglobin levels (8.7 +/- 1.7 g/dL) than patients not receiving MV (8.2 +/- 1.7 g/dL, p < 0.0001). Notably, 40.1% of all transfusions in patients receiving MV were administered after day 3 of the ICU stay, compared to 21.2% in patients not receiving MV (p < 0.0001), and a higher percentage of patients receiving MV remaining in the ICU after day 3 underwent transfusions (33.4% vs 18.3%, p < 0.0001). Mortality was higher (17.2% vs 4.5%, p < 0.0001) and mean hospital (15 days vs 10 days, p < 0.0001) and ICU stays (9 days vs 4 days, p < 0.0001) were longer in the subgroup receiving MV. CONCLUSIONS: Mechanical ventilation appears to be an easily identifiable early marker for allogeneic blood exposure risk in ICU patients. While the longer ICU stays account for much of this risk, patients receiving MV also appear to undergo transfusions at higher hemoglobin thresholds than patients not receiving MV, at least early in the ICU stay. Justification of this relatively liberal transfusion practice in patients receiving MV will require further study.     

Persistent air leaks in patients receiving mechanical ventilation

The term bronchopleural fistula (BPF) can be loosely defined as persistent leakage of gas from the airways into the pleural space. A true BPF, however, is located in the central airways, whereas leaks located peripherally are better described by the term parenchymal-pleural fistula (PPF). The presence of a persistent leak in a mechanically ventilated patient is a worrisome prognostic sign independent of the precise origin, yet it is important to distinguish BPF from PPF in this population. Fundamental differences in the pathogenesis and natural history of these two entities dictate divergent approaches to management. This review compares and contrasts the evaluation and management of BPF and PPF in patients receiving mechanical ventilation, and provides an overview of the many nonsurgical interventions used to manage persistent leaks.     

Safety of ultrasound-guided thoracentesis in patients receiving mechanical ventilation

OBJECTIVE: To determine the safety of ultrasound-guided thoracentesis (UST) performed by critical care physicians on patients receiving mechanical ventilation. DESIGN: Prospective and observational. SETTING: ICUs in a teaching hospital. PATIENTS: Two hundred eleven serial patients receiving mechanical ventilation with pleural effusion requiring diagnostic or therapeutic thoracentesis. INTERVENTIONS: Two hundred thirty-two separate USTs were performed by critical care physicians without radiology support. Anteroposterior chest radiographs were reviewed for possible postprocedure pneumothorax. RESULTS: Pneumothorax occurred in 3 of 232 USTs (1.3%). The procedure was well tolerated in this critically ill population. CONCLUSIONS: UST performed in patients receiving mechanical ventilation without radiology support results in an acceptable rate of pneumothorax.     

Role of transbronchial needle aspiration in patients receiving mechanical ventilation

STUDY OBJECTIVE:s: To evaluate the diagnostic accuracy and safety of transbronchial needle aspiration (TBNA) in patients receiving mechanical ventilation in the ICU. METHODS: Retrospective review of all patients in the medical and surgical ICUs from February 1999 to July 2001 who underwent TBNA while receiving mechanical ventilation. RESULTS: A total of eight histology (19 gauge) and eight cytology (22 gauge) TBNAs were performed on eight patients (four men and four women). TBNA yielded a definitive pathologic diagnosis in five of eight patients (62.5%). Diagnoses were posttransplantation lymphoproliferative disorder, large cell carcinoma, poorly differentiated non-small cell carcinoma, squamous cell carcinoma, and adenocarcinoma. Among patients with negative TBNA results (n = 3), two patients underwent mediastinoscopy. Results of mediastinoscopy were non-small cell carcinoma and inflamed tissue. TBNA led to management changes in five of these patients. Excluding one patient in whom a negative TBNA result could not be further confirmed, TBNA yielded a sensitivity of 83%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 50%. The overall accuracy of the procedure was 75%. There were no complications following any of the TBNAs. CONCLUSIONS: In this small group of patients, TBNA was safe and had a high diagnostic accuracy in selected patients receiving mechanical ventilation in the ICU.     

机械通气患者不同声门下吸引方式的临床对比研究

目的 比较持续性声门下吸引(CASS)和间歇性声门下吸引(IASS)在预防呼吸机相关性肺炎(VAP)中的临床价值,及其对气道黏膜的影响.方法 将ICU收治的116例机械通气患者随机分为3组:CASS组(40例)、IASS组(38例)和对照组(不行声门下吸引,38例).记录并比较3组患者早发性和晚发性VAP发病率、发生时间,以及CASS组、IASS组患者气囊上方吸引液潜血阳性例数.结果 ①CASS组和IASS组的早发性和晚发性VAP发病率相似,差异无统计学意义(P＞0.05).CASS组和IASS组的早发性和晚发性VAP发病率均低于对照组(P＜0.05或P＜0.01).②CASS组和IASS组VAP发生时间晚于对照组(P＜0.05).CASS组和IASS组VAP发生时间相似,差异无统计学意义(P＞0.05).③IASS组的气囊上方吸引液潜血阳性率低于CASS组(P＜0.05).结论 CASS和IASS均可降低早发性和晚发性VAP发病率,并延迟VAP的发生,两者临床效果相似.但IASS有更低的气囊上方气道黏膜损伤风险.     

A clinical trial of Gingkco Biloba Extract in patients with intermittent claudication

Thirty-seven patients with stage 2 peripheral vascular disease were randomised to receive a six month course of Gingkco Biloba Extract (Tanakan) or matching placebo. Assessment, by claudication distance, A/B ratio, Doppler ankle pressure response to exercise together with recovery time, and a 10 cm analogue scale (LAS) estimation of maximal pain severity, was performed before treatment, and at 6, 12 and 24 weeks. LAS scores were significantly improved after 24 weeks in patients receiving EgB, but not placebo. Claudication distance was significantly increased by Egb. Although claudication distance also increased in the placebo group, this was not significant. A/B ratio and Doppler ankle responses to exercise did not show any significant change in either group at any time interval, nor did the post exercise recovery time. Gingkco Biloba Extract is a safe and effective method of improving walking distance and reducing pain severity in patients with intermittent claudication, although Doppler studies have failed to suggest any gross improvement in the perfusion of the ischaemic leg.     

Prognosis of noncardiac medical patients receiving mechanical ventilation in a veterans hospital

In order to determine prognostic factors in noncardiac medical patients treated by mechanical ventilation in a Veterans Administration hospital, 78 patient records were reviewed. Disease severity was scored by the Acute Physiology and Chronic Health Evaluation (APACHE) II system. Physicians' prior impressions of prognostic factors were compared with the actual results of this study. Most patients were middle-aged men with respiratory diseases. Fifty-nine patients (76 percent) died in the hospital. Survivors of hospitalization and nonsurvivors had similar age, diagnoses, emergency intubations, duration of ventilation, and pH and oxygen tension after 24 hours of ventilation. However, only one of 31 patients with a serum albumin level of 2.5 g/dl or less at the initiation of mechanical ventilation survived (p less than 0.001). Of 24 patients requiring a fractional inspired oxygen concentration greater than 50 percent at 24 hours, none survived (p less than 0.005). At all APACHE II scores, the mortality rates documented in this study were higher than predicted. Physicians overestimated the impact of several variables, including age and presence of pneumonia, on mortality. At the San Francisco Veterans Administration Medical Center, a low serum albumin level may aid in the decision whether to begin mechanical ventilation, and a high fractional inspired oxygen concentration at 24 hours may aid in the decision regarding further aggressive care. These findings need to be validated in other patients before being applied. Conversely, certain older patients, and those undergoing emergency intubation or intubation for a prolonged time, may have as good a prognosis as patients without these factors.     

The impact of tracheotomy timing in critically ill patients undergoing mechanical ventilation: A meta-analysis of randomized controlled clinical trials with trial sequential analysis

Background

The optimal timing of tracheotomy in critically ill ventilated patients remains controversial.