Weaning from Mechanical Ventilation in Children: Are We Getting It Right?

How to cite this article: Baalaaji ARM. Weaning from Mechanical Ventilation in Children: Are We Getting It Right? Indian J Crit Care Med 2021;25(9):974–975.

Respiratory disorders are one of the major reasons for admission into the Pediatric Intensive Care Unit (PICU), and mechanical ventilation is a major intervention carried out to save lives in these children. Although mechanical ventilation is lifesaving, it is not free of complications. Airway injury, ventilator-induced lung injury, ventilator-associated pneumonia (VAP), need for sedatives, and their resultant effects can all lead to prolonged morbidity in children. Hence, it becomes imperative to identify the patient''s readiness to sustain spontaneous breathing independent of a ventilator and liberate them from mechanical ventilation promptly. On the contrary, premature extubation exposes the child to risks of extubation failure, reintubation, aspiration, higher risks of VAP, and mortality. Both delayed and premature extubation result in higher complication rates, increased morbidity and mortality, and also escalating the costs involved.The phase of transition from complete ventilatory support to complete spontaneous breathing while maintaining adequate gas exchange is referred to as “weaning from ventilation.” It should be distinguished from extubation that refers to the physical removal of an endotracheal tube. Approximately 40–50% of the total ventilation duration is occupied by this weaning phase.¹ The clinical decision to wean from ventilation has been traditionally based on physician''s judgment and clinical experience. The steps involved in weaning and subsequent extubation include (1) assessment of the readiness to wean; (2) spontaneous breathing trial (SBT) while monitoring the child for possible weaning failure; and (3) extubation. Readiness to wean is assessed once the child is stabilized and the primary indication for initiating ventilation is reversed. The parameters considered are (i) reversal of the primary reason for ventilation; (ii) ability to maintain oxygenation and ventilation with low FiO₂ and positive end-expiratory pressure (PEEP); (iii) hemodynamic stability; (iv) acceptable consciousness level and airway protective reflexes; (v) adequate spontaneous respiratory efforts; (vi) sedation level; and (vii) fluid balance. This assessment is done daily, and eligible children are then weaned from ventilation.²Once it is decided that the child is ready to be weaned, the most common approach is a gradual decrease in ventilatory support and assessing the readiness to extubate once they tolerate a low level of ventilator support. The alternative approach is to assess the readiness to extubate as soon as the patient meets the criteria to initiate the ventilator weaning process. SBT is used to assess the ability of a patient to maintain acceptable gas exchange with minimal/no ventilator assistance. Pressure support (PS) with PEEP, Continuous Positive Airway Pressure (CPAP), or a T-piece trial are the various accepted SBTs. Once the child is able to tolerate one of the three SBTs without any increase in effort of breathing, they can be extubated, provided, protective airway reflexes are intact and are able to handle tracheal secretions. It was previously believed that breathing through a narrow endotracheal tube by infants imposes additional work of breathing and PS is needed to overcome this presumed additional work, although it has been proven to be not the case.^3,4 It is also important to realize that provision of “minimal PS” offers substantial ventilatory assistance to the child and does not truly represent complete spontaneous breathing. A T-piece or CPAP ≤5 cm H₂O provides the best assessment of unassisted effort of breathing.^5,6This entire process of weaning assessment and subsequent extubation could be protocolized or driven by individual physician. Protocolized weaning aims at having a uniform set of rules to reduce unwanted variability in the clinical practice. The use of protocols may also have the potential to enable nonmedical healthcare personnel, namely the nurses and respiratory therapists to take up the responsibility in weaning, thus initiate the weaning process at an appropriate time and potentially reduce the risks and costs associated with unnecessary prolongation of ventilation duration.⁷In the current study, the authors have compared the duration of mechanical ventilation and extubation failure rates using two different approaches: protocolized weaning using PS SBT followed by T-piece vs nonprotocolized physician-driven weaning, which was synchronized intermittent mandatory ventilation followed by the T-piece trial.⁸ The children were randomized once they met the eligibility criteria for SBT. Prior to extubation, children in both the groups were given a T-piece trial of 2 hours duration. A majority of children (38/40) in both the groups could be extubated, and no significant difference could be demonstrated between the two groups. Also, the ventilation duration was similar between the two groups.Previous studies in children gave conflicting results with respect to protocolized weaning. In the study by Foronda et al., children randomized to SBT protocol using PS with PEEP had a significant reduction in average ventilation duration compared to standard care.⁹ In another study conducted by Ferreira et al, during the postoperative period following cardiac surgery, the SBT group had a greater extubation success and shorter PICU length of stay compared to the control group.¹⁰ A few other randomized controlled trials did not find significant differences in the duration of ventilation or reintubation rates between protocolized and control groups.^11,12 The results of these studies are not generalizable due to the heterogeneous study population, varying practices of weaning protocol, and different end points chosen as primary outcome measures.While comparing the different modalities that assess weaning and extubation in children, it is essential to understand the differences in the terminologies—extubation failure and weaning failure. Extubation failure is defined as a requirement for reintubation within 48 hours of extubation. In children, one of the major reasons for reintubation is upper airway obstruction due to injury or edema and while, it denotes extubation failure, it cannot be termed as weaning failure. On similar grounds, patients who are electively initiated on noninvasive ventilation postextubation cannot be termed as successful weaning or “complete liberation from ventilator” but they might have been successfully extubated.The current study has demonstrated that PS SBT could be utilized to assess readiness to extubate; however, the authors have also performed additional T-piece trials following PS SBT prior to extubation. Also, the shorter weaning duration in the control group could be due to decisions being taken by the Pediatric Intensivist in the unit. Although data in adults support the use of a dedicated weaning protocol that results in faster weaning, the data are still less clear in children.¹³ The reasons for this disparity could be due to shorter duration of mechanical ventilation and lower extubation failure rates in children.¹⁴Thus, the process of weaning of children from mechanical ventilation continues to involve as much an art as science. Consistent and daily application of practice such as sedation holidays, assessing readiness to wean, and SBTs would be needed to liberate them from mechanical ventilation at appropriate time point. The exact way of conducting the various SBTs, the relation with weaning success, and the effect on ventilator-free days or length of stay still remain unanswered.     

人类免疫缺陷病毒阳性肺结核患者临床分析

目的 提高人类免疫缺陷病毒（ＨＩＶ）阳市肺结核（ＰＴＢ）的认识。方法 对赤道几内亚巴塔医院１９９６年１月～１９９９年１１月确诊的１６８例ＨＩＶ阳性ＰＴＢ进行分析。结果 ＨＩＶ在ＰＴＢ患的感染率由１９９６年的１１．４％升至１９９９年的２２．７％。患多急骤起病（９４．６％）,以近期消瘦（８２．１％）、全身关节酸痛（７８．６％）、皮肤瘙痒（４２．９％）、慢性腹泻（２３．２％）、浅表淋巴结肿大（２０．     

类风湿性关节炎病人关节滑膜液与外周血中G1特异性T细胞的特点

目的为比较研究类风湿性关节炎病人 T细胞库中是否存在 G1特异性 T淋巴细胞极其生物学特性。方法应用重组人软骨抗原凝集原 G1为抗原 (r G1) ,采用国际标准半有限稀释建立细胞株法 ,从类风湿性关节炎病人外周血中分离建立 G1特异性 T细胞并分析其生物学特性。结果从 4名类风湿性关节炎病人外周血中分别分离建立了 13株 G1特异性 T细胞株。分析比较了这些细胞株 ,发现病人的 G1特异性 T淋巴细胞出现频率为 36 .2 %。所有 T细胞株与 r G1及 WT和 PPD共同培养以观察其特异性反应性 ,结果发现所建立的 13株 T细胞株对人软骨抗原凝集素 G1区具有良好的特异性。进一步用r G1肽段分析 ,发现其中 5株主要对 G1C末端呈特异性反应。细胞表型分析发现 ,所有这些 T细胞株均表现为 CD3 、CD4 与αβ TCR阳性 ;细胞因子分泌类型以 TH1为主。结论 RA病人外周血与关节滑膜液中均有 G1特异性 T细胞。     

Individual differences in psychotic effects of ketamine are predicted by brain function measured under placebo

The symptoms of major psychotic illness are diverse and vary widely across individuals. Furthermore, the prepsychotic phase is indistinct, providing little indication of the precise pattern of symptoms that may subsequently emerge. Likewise, although in some individuals who have affected family members the occurrence of disease may be predicted, the specific symptom profile may not. An important question, therefore, is whether predictive physiological markers of symptom expression can be identified. We conducted a placebo-controlled, within-subjects study in healthy individuals to investigate whether individual variability in baseline physiology, as assessed using functional magnetic resonance imaging, predicted psychosis elicited by the psychotomimetic drug ketamine and whether physiological change under drug reproduced those reported in patients. Here we show that brain responses to cognitive task demands under placebo predict the expression of psychotic phenomena after drug administration. Frontothalamic responses to a working memory task were associated with the tendency of subjects to experience negative symptoms under ketamine. Bilateral frontal responses to an attention task were also predictive of negative symptoms. Frontotemporal activations during language processing tasks were predictive of thought disorder and auditory illusory experiences. A subpsychotic dose of ketamine administered during a second scanning session resulted in increased basal ganglia and thalamic activation during the working memory task, paralleling previous reports in patients with schizophrenia. These results demonstrate precise and predictive brain markers for individual profiles of vulnerability to drug-induced psychosis.     

红豆杉中紫杉醇的高效液相色谱法测定(英文)

本文研究了高效液相色谱法测定红豆杉Taxus chinensis中紫杉醇的含量,以倍他米松作内标,在填充以YWG 80(10μm)固定相的不锈钢色谱柱上,以CH₂Cl₂-MeOH(95:5)作流动相,在UV 228 nm波长进行检测,其变异系数小于2%。     

Gallbladder bile: an experimental study in dogs using MR imaging and proton MR spectroscopy

Magnetic resonance (MR) imaging, proton MR spectroscopy, and biochemical analysis were performed to investigate MR signal intensity (SI) differences between concentrated and dilute gallbladder bile of seven fasting and five sincalide-treated dogs. MR images revealed high SI from bile of fasting dogs and low to medium SI in sincalide-treated dogs when spin-echo (SE) pulse sequences with repetition rates of 0.5 and 2.0 sec were used. Proton MR spectra were similar for fasting and sincalide-treated dogs. In fasting dogs, water content in the bile was slightly lower, and cholesterol, phospholipid, and bile acid concentrations were higher. More than 90% of proton signals in all Fourier transform free induction decay spectra emanated from water molecules, and no lipid proton resonances were detected in Fourier transform SE spectra after tau delays of 7 msec. These results indicate that the differences in SI are caused by alterations in relaxation times of water protons, possibly resulting from the interactions of water protons and macromolecules.