Right ventricular function during weaning from mechanical ventilation after coronary artery bypass grafting: effect of volume loading

Objective: The study was designed to investigate the right ventricular (RV) reaction to weaning from mechanical ventilation (MV) in patients with and without volume loading after coronary artery bypass grafting (CABG). Design: Controlled study. Setting: Surgical intensive care unit in a university hospital. Patients: 18 patients were randomized in two groups, Control group (n = 9) and Volume group (n = 9), when the established criteria for weaning from the respirator were satisfied. Intervention: During MV, patients in the Volume group received in rapid (10-min) 6 ml/kg infusion of a 6 % hydroxyethyl starch preparation. Measurements and results: Hemodynamic parameters were measured using a combined right ventricular (RV) ejection fraction-oximetry pulmonary artery catheter at T0 (during MV: baseline), T1 (during MV: 10 min after volume loading or at the same time in the Control group), T2 [after 20 min of spontaneous ventilation (SV)]. In the Control group, RV volumes did not differ throughout the study, while cardiac index (CI) and RV stroke work index (RVSWI) increased from T1 to T2. In the Volume group, RV volumes increased from T0 to T1, further increasing from T1 to T2, whereas CI increased only from T0 to T1. In this group, RVSWI increased from T0 to T1 in 8/9 patients and from T1 to T2 in 6/9 patients. Conclusions: An increase in RV volumes with a concomitant increase in RVSWI was observed in high preload patients when going from MV to SV, suggesting a preserved RV function during weaning from MV in this group compared with control patients. The depression in RV contractility observed in some patients suggested that rapid volume expansion before weaning from MV in CABG patients must be done carefully. Received: 25 April 1997 Accepted: 24 September 1997     

Fade of pulmonary function during residual neuromuscular blockade

OBJECTIVES: A decrement in evoked muscle force with repetitive nerve stimulation (fade) suggests impaired neuromuscular transmission. We tested the hypothesis that fade of pulmonary function, ie, a decrease in values of FVC with the second spirometric maneuver compared to the first maneuver, occurs during impaired neuromuscular transmission. DESIGN: Prospective study. PARTICIPANTS: Six healthy male volunteers. INTERVENTIONS: A series of three consecutive spirometric maneuvers was performed every 5 min in six awake healthy volunteers before, during, and after partial paralysis evoked by rocuronium (0.01 mg/kg IV plus 2 to 8 microg/kg/min). MEASUREMENTS AND RESULTS: We measured FVC, FEV(1), forced inspiratory volume in 1 s (FIV(1)), peak expiratory flow (PEF), and peak inspiratory flow (PIF) by spirometry, and force of adductor pollicis muscle by mechanomyography (train-of-four [TOF] stimulation). A statistically significant fade (reduction of the second maneuver from the first maneuver) of FVC, FEV(1), FIV(1), PEF, and PIF was observed during neuromuscular blockade. With peak relaxation (TOF ratio, 0.5) fade amounted to medians of 10% (interquartile range [IQR], 9 to 23%), 7% (IQR, 2 to 16%), 31 (IQR, 19 to 47%), 9% (IQR, 3 to 24%), and 30% (IQR, 5 to 43%), respectively. A fade of >or= 10% was always associated with a clinically relevant (>or= 10%) FVC reduction from baseline (ie, FVC before rocuronium administration). However, FVC reduction from baseline was still present in 23% of measurements without a relevant FVC fade. CONCLUSIONS: A clinically relevant fall (fade) in FVC from the first to the second value during or after neuromuscular blockade suggests impaired pulmonary function and may be due to muscle paralysis. For this reason, the first (best) FVC value may overestimate pulmonary function and expose the patient to an unidentified risk.     

血清甲状腺激素检测对COPD机械通气患者的临床价值

目的评价甲状腺激素检测对入住ICU行机械通气的慢性阻塞性肺疾病（COPD）病人治疗及预后的价值。方法选择入住ICU机械通气的COPD病人86例,在机械通气时和脱机后均进行甲状腺激素水平的检测,并对数据进行分析。结果患者入住ICU行机械通气时血清TT3、FT3、TT4、FT4水平与脱机时比较均有降低,脱机越困难,甲状腺激素下降越明显。经治疗病情好转,脱呼吸机后,血清TT3、FT3、TT4、FT4显著回升。结论机械通气的COPD患者血清甲状腺激素水平出现异常,其甲状腺激素水平高低与CQPD患者脱机难易和预后有一定关系。     

Interobserver agreement rate of the spontaneous breathing trial

Purpose

During the mechanical ventilation weaning process, the spontaneous breathing trial (SBT) is the confirmatory test of patients' capability to breathe unassisted. However, the SBT interobserver agreement rate (its reliability) is unknown, and our objective was to evaluate it.

Materials and Methods

This is a prospective, multicentric and observational study. Patients were included when the SBT criteria were fulfilled. Two physicians and 2 respiratory therapists (RTs) rated each SBT. The SBT interobserver agreement was measured using κ statistic and also the percentage of agreement with its 95% credible interval (CrI) calculated by a Bayesian inference.

Results

Ninety-three distinct physicians and 91 distinct RTs rated 130 SBTs. The κ coefficient was 0.46 for physicians and 0.57 for RT, indicating a moderate interobserver agreement rate. The percentage of agreement was 87.7% between physicians (95% CrI, 81.0%-92.3%) and 86.2% between RT (95% CrI, 79.2%-91.1%). The physicians' and RT' percentage of agreement were not statistically different (P = .71).

Conclusions

The SBT interobserver agreement rate is only moderate for physicians and RT. The percentage of agreement between 2 different SBT observers is 79.2% to 92.3%. Therefore, a relevant percentage of patients will have different extubation decisions depending on the SBT observer.     

Neurally adjusted ventilatory assist in weaning of neonates affected by congenital diaphragmatic hernia

Objective: The aim of the study is to evaluate the application of neurally adjusted ventilatory assist (NAVA) in the respiratory weaning of patients affected by congenital diaphragmatic hernia (CDH). Methods: We analyzed the NAVA weaning in 12 neonates affected by CDH, relating the effectiveness of the electrical activation of the diaphragm (EAdi) signal to the type of CDH repair (with or without patch), the size of the patch, the stomach and His angle position, and the trend evaluation of some cardiorespiratory parameters with NAVA compared to pressure-support-ventilation (PSV). Results: 5 neonates submitted to primary repair showed a regular EAdi signal and were successfully weaned with NAVA. Of the seven patients submitted to patch repair, five operated with patch limited to the diaphragmatic postero-lateral area had an active EAdi signal that permitted weaning with NAVA. Only in two neonates with hemidiaphragm agenesis was NAVA not feasible due to the impossibility to capture the EAdi signal. Compared to PSV, NAVA allows a significant improvement of oxygenation-linked indexes and paCO₂, while PIP is reduced. Conclusion: Neonatal CDH with a postero-lateral diaphragmatic defect allows the NAVA catheter to obtain a correct EAdi signal and develop a viable NAVA ventilation. The lower risk of lung injury in NAVA appears compatible with current ventilatory strategies considered useful in CDH.     

长期机械通气的老年患者撤机的影响因素分析

目的 筛选老年患者长期机械通气(PMV)的影响因素。方法 收集154例肺部感染或慢性阻塞性肺疾病(COPD)急性加重患者，在机械通气(简称通气)前及撤机或通气21d时的各项指标。结果 单因素分析结果表明：年龄、是否卧床、白细胞数、中性粒细胞比例、肺泡动脉血氧分压差[P（A-a）O2]、尿素氮、肌酐、上消化道出血、心率、血压，短期通气组撤机时或PMV组通气21d时上述指标及心功能、意识状态为PMV的影响因素。多因素分析结果表明：与PMV相关的独立因素为年龄、通气21d时P（A-a）O2及心功能；年龄≥82．0岁、通气21d时P（A-a）O2≥95．0mmHg、心功能≥3级为PMV的危险因素。随后检验8例PMV患者，同时满足3项指标判定PMV的准确性为87．5％。结论 年龄、通气21d时P（A-a）O2及心功能为影响PMV的独立因素。     

Tolerance of heat-treated kiwi by children with kiwifruit allergy

Kiwifruit allergy is increasing among children but whether heating affects clinical tolerance to kiwifruit is unknown. To assess tolerance to heated kiwifruit in children allergic to fresh kiwifruit. In this prospective trial, 20 children (median age 9.4 yr) with a history of immediate allergic reactions to fresh kiwifruit underwent double-blind placebo-controlled food challenges with steam-cooked (100 degrees C for 5') and industrially homogenised kiwifruit. Skin prick tests with a commercial kiwifruit allergen, raw kiwifruit and double-blind placebo-controlled food challenge with 25 g of fresh kiwifruit were used to confirm the history. Specific kiwifruit IgE to native and homogenized fruit were identified by immunoblotting. Fresh kiwifruit induced positive skin prick wheals in all children (confirmed during challenge in 19 patients). Commercial skin prick test elicited a positive response in five children, steam-cooked kiwifruit in five, and the homogenised kiwifruit preparation in none. UniCAP determinations were positive for kiwifruit in three patients. All children's sera showed specific IgE at immunoblotting with raw kiwifruit and one with the homogenised preparation (major allergens identified: Act c 1 and Act c 2). There was no clinical reactivity following challenge with homogenised kiwifruit but one child reacted to cooked kiwifruit challenge. Industrial heat treatment and homogenisation can make kiwifruit safe for children who are allergic to this increasingly popular fruit. This has dietary implications for children who are allergic to several fruit and vegetable proteins.