Today’s Pediatric Anesthesia Article of the Day is yet another from the special pulmonary issue of the Journal of Pediatric Anesthesia. And this is not the last…there will be a couple of others coming to your mailbox in the next couple of days and weeks. I am especially proud of this one. The authors, Drs. Chinyere (Chi-Chi) Egbuta of the Boston Children’s Hospital and R. Blaine Easley of the Texas Children’s Hospital as well as our PAAD reviewer Dr. Justin Lockman were all my former fellows and current mentees. Myron Yaster MD
“I have learned much from my teachers, more from my colleagues and most from students.” Rabbi Chanina in the Talmud
Original article
Egbuta C, Easley RB. Update on ventilation management in the Pediatric Intensive Care Unit. Paediatr Anaesth. 2022 Feb;32(2):354-362. PMID: 34882910
Many of the patients we care for in the operating room either come from, or will go to, the PICU or NICU. Because of the “wide range of clinical diagnoses found in pediatric critical care, and variability in PICU patient size and lung maturity, there is little scientific evidence to standardize pediatric mechanical ventilation practices.”(1) Today’s Pediatric Anesthesia Article of the Day summarizes some of the recent advances in pediatric mechanical ventilation in the PICU population while highlighting the available evidence supporting clinical practice. Another article on the NICU population will be discussed in a future PAAD.
“Non-invasive ventilation (NIV) is the delivery of mechanical respiratory support without the use of an endotracheal tube and is usually deployed during the initiation phase in the management of acute respiratory failure (ARF) when respiratory distress and hypoxia are persisting or worsening despite initial application of basic oxygen therapy via nasal cannula or facemask.”(2) Over the past 2 decades, NIV in children has dramatically changed ventilation strategies in the PICU. In many centers now, the first step in management of respiratory distress is the application of high-flow nasal cannula (HFNC), which delivers a constant flow of heated, humidified O2 flow at rates of up tp 2 L/kg/min. It is unclear how much positive pressure this provides for individual patients, since Ohm’s law (V=IR) means that constant flow in the setting of variable resistance (patient inspiratory flow, mouth open vs. closed, size of nares relative to size of cannula) leads to variable pressure. Nonetheless, many patients do well with HFNC and avoid more aggressive therapies. When HFNC fails, therapy often escalates to CPAP (generally 5-12 cm H20) or BiPAP (IPAP generally between 10 and 20 cm H2O, EPAP between 5 and 12 cm H2O). The major downsides of NIV over invasive ventilation include aspiration risk, leak at the interface site, and skin breakdown (especially with higher pressures necessitating tighter straps).
NIV (including HFNC, CPAP, and BiPAP) therapies are often also utilized upon tracheal extubation as a bridge to weaning completely off support. There is some controversy about whether or not extubation has “failed” if NIV is required – after all, the classic teaching is that an ETT is a safer way to deliver pressure if it’s needed; however, in recent years we have recognized the risks of prolonged intubation to a greater extent and often push to extubate critically-ill children sooner.
Signs of success of NIV include improvement of oxygen saturation or resolution of hypoxemia, decreased work of breathing, and clinical and radiographic (if available) signs of lung recruitment, such as resolution of atelectasis. Interestingly, and not discussed in the article, is the dramatically decreased need for tracheal intubation with institution of NIV and the profound effects on the airway management skills (i.e., intubation technical skills) among pediatric intensivists. In the past, when tracheal intubation prior to mechanical ventilation was common, pediatric intensivists were always considered experts at intubation. We wonder whether this is still true now that fewer and fewer intubations occur in the PICU – in many PICUs, a majority of breathing tubes even among intubated patients are inserted in the operating room or in an emergency department.
Speaking of breathing tubes, conventional mechanical ventilation has also undergone profound changes over recent years. In the past it was simple: “In continuous mandatory ventilation or intermittent mandatory ventilation, the patient gets a breath regardless of respiratory effort. In assisted ventilation, like in assist control or synchronized intermittent ventilation (SIMV), the patient not only receives volume or pressure support for every breath initiated but also receives breaths at a set rate if the patient fails to breathe.” Most of us always used pressure control in children because it was thought to be safer. In newer ventilation modes, such as pressure regulated volume control (PRVC) (also called pressure control with volume guarantee (PC-VG) or volume control with “autoflow,” depending on device manufacturer), tidal volumes are set and are delivered at the lowest possible airway pressures using a decelerating inspiratory flow velocity that is continuously adjusted by the ventilator based on the compliance of the prior breath. Most of you are likely familiar with these changes because the modern anesthesia workstation ventilator has increasingly incorporated many of the features of PICU ventilators into their design. ICU ventilators are even better because they can incorporate tidal volume measurement at the Y-connector for the smallest patients. The result is that most of us now use volume-set modes like PRVC when caring for even tiny patients.
The data about optimal ventilation strategies in children are complex and somewhat unclear, unlike in adults where the data seem more clear. Still, most intensivists follow adult guidelines for ARDS patients including “open lung” strategies (high PEEP), low tidal volume (4-6 mL/kg), and permissive hypercapnia (PaCO2 in the 45-70 mmHg range unless contraindicated due to other conditions.
Today’s article concludes with a discussion of both tracheotomy criteria in children and issues surrounding delirium and (opioid, benzodiazepine, and dexemdetomidine) withdrawal in PICU patients. In adult patients, tracheostomy is one of the “most commonly performed invasive, bedside procedures impacting between 10% and 24% of mechanically ventilated adult patients.”(2) It is much more rarely done in children; the procedure is more complex, and both families and physicians associate tracheostomy with long-term care and chronic ventilation in children. Unfortunately, the latter becomes a self-fulfilling prophesy since the result is lack of tracheostomy for patients who might benefit in the short term. The failure to make this conversion early for pediatric patients in our opinion results in prolonged sedation, often including neuromuscular blockade, and resultant sleep disruption, delirium, development of tolerance and withdrawal, abnormal brain development/maturity, difficulties with gut motility, delayed rehabilitation services, and longer ICU stays because of slow sedation weans AND multiple failed extubation/reintubation attempts. For many patients, we think these are preventable challenges and we hope to see a move toward early tracheostomy in children who could benefit from it. Although there are several strategies to reduce the need for sedation and analgesia, such as early progressive mobilization(3,4), none are as effective as waking the kid up after a trach! We recognize that this is very controversial, but wonder what you think? Myron Yaster MD and Justin L. Lockman MD, MSEd
References
1. Kneyber MCJ, de Luca D, Calderini E, Jarreau PH, Javouhey E, Lopez-Herce J, Hammer J, Macrae D, Markhorst DG, Medina A, Pons-Odena M, Racca F, Wolf G, Biban P, Brierley J, Rimensberger PC. Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC). Intensive Care Med 2017;43:1764-80.
2. Egbuta C, Easley RB. Update on ventilation management in the Pediatric Intensive Care Unit. Paediatr Anaesth 2022;32:354-62.
3. Patel RV, Redivo J, Nelliot A, Eakin MN, Wieczorek B, Quinn J, Gurses AP, Balas MC, Needham DM, Kudchadkar SR. Early Mobilization in a PICU: A Qualitative Sustainability Analysis of PICU Up! Pediatr Crit Care Med 2021;22:e233-e42.
4. Wieczorek B, Ascenzi J, Kim Y, Lenker H, Potter C, Shata NJ, Mitchell L, Haut C, Berkowitz I, Pidcock F, Hoch J, Malamed C, Kravitz T, Kudchadkar SR. PICU Up!: Impact of a Quality Improvement Intervention to Promote Early Mobilization in Critically Ill Children. Pediatr Crit Care Med 2016;17:e559-e66.