European Journal of Cardiovascular Medicine

High Flow Nasal Cannula (HFNC) therapy has increasingly become a pivotal adjunct in the management of pediatric patients post-cardiac surgery. This non-invasive ventilation tool offers heated and humidified medical gas at high flows, improving the patients' comfort and oxygenation, thus potentially reducing the need for reintubation. The use of HFNC in pediatric cardiac surgery patients, particularly after complex repairs such as Glenn and Senning operations or Tetralogy of Fallot (TOF) and Ventricular Septal Defect (VSD) closures, warrants detailed investigation due to the unique physiological challenges these conditions pose.^1-5

Cardiac surgeries in children are high-risk procedures that can significantly alter respiratory dynamics due to cardiopulmonary bypass, surgical trauma, and postoperative pain. These challenges are compounded in patients with congenital heart diseases where altered pulmonary flow dynamics and the presence of single ventricle physiology can predispose them to respiratory complications postoperatively. In this context, HFNC therapy acts not only as a bridge between the removal of mechanical ventilation and full respiratory recovery but also as a tool for acute respiratory support.^5-7

The current study focusing on a select cohort of pediatric patients who underwent HFNC therapy following extubation in the postoperative period. The indication for HFNC was primarily the presence of elevated PCO2 levels, increased respiratory rates, and decreased oxygen saturation as per defined clinical criteria. These parameters highlighted the respiratory distress syndromes typically observed in the postoperative phase of cardiac surgeries.

This research meticulously documented the outcomes of HFNC in seven pediatric patients with a mix of single and double ventricle repairs, recording parameters such as blood gas levels, respiratory and heart rates, and overall patient stability to evaluate the effectiveness of HFNC in preventing reintubation. Through this detailed analysis, the study aimed to add valuable insights into the optimal postoperative management of pediatric cardiac surgery patients, potentially setting the stage for broader application and standardized protocols involving HFNC therapy in similar high-risk pediatric populations.

Study Design

The study was designed as an observational study and conducted in a controlled clinical setting.

Study Setting and Participants

The research was carried out at the Department of Cardiothoracic and Vascular Surgery, GB Pant Institute of Postgraduate Medical Education and Research in New Delhi, India. We included a cohort of seven pediatric patients who underwent various cardiac surgeries and required postoperative respiratory support.

Inclusion Criteria:

• Patients aged between 1.5 and 6 years who underwent cardiac surgery such as Glenn operation, Tetralogy of Fallot (TOF) repair, Ventricular Septal Defect (VSD) closure, or Senning operation.
• Postextubation respiratory distress characterized by increased PCO2 (>50 mmHg), respiratory rate above age-specific normal ranges (>40 breaths/min for ages 1-4 years, >50 breaths/min for <1 year), and reduced oxygen saturation (Spo2 <92% in total repair and <75% in single ventricle repair).

Exclusion Criteria:

• Patients with a history of chronic lung disease or those who were on mechanical ventilation prior to surgery.

HFNC Therapy Protocol

HFNC therapy was initiated postextubation according to the following standardized protocol:

• Equipment:
• HFNC system capable of delivering up to 60 LPM of heated and humidified oxygen.
• Flow rates were adjusted based on patient weight (2 L/kg/min).

• Administration:
• The initial flow rate was set according to the patient’s body weight and clinical condition.
• Oxygen concentration was adjusted to maintain SpO2 between 92% to 99%.
• Therapy duration varied among patients, determined by clinical improvement and gas exchange parameters.

Data Collection

Variables:

• Respiratory Parameters: Respiratory rate (RR), SpO2, and partial pressure of carbon dioxide (PCO2) were recorded pre and post-HFNC therapy.
• Cardiac Parameters: Heart rate (HR) and systolic blood pressure (SBP) were monitored.
• Other Parameters: Lactate levels were measured to assess metabolic state pre- and post-therapy.

Data were collected at two time points: immediately before the initiation of HFNC therapy (pre-HFNC) and after the discontinuation of HFNF therapy (post-HFNC).

Statistical Analysis

Data were analyzed using descriptive statistics to present the mean and standard deviation of continuous variables such as age, weight, flow rate, duration of HFNC therapy, and all monitored physiological parameters. Paired t-tests were used to compare pre- and post-therapy values for respiratory and cardiac parameters to evaluate the clinical efficacy of HFNC. A p-value of less than 0.05 was considered statistically significant

The efficacy of High Flow Nasal Cannula (HFNC) therapy in postoperative pediatric cardiac patients was evaluated through an analysis of respiratory and cardiac parameters. This cohort included a total of seven patients who underwent a variety of cardiac surgeries.

Table 1 provides a detailed view of the demographics and High Flow Nasal Cannula (HFNC) settings for seven pediatric patients post-cardiac surgery, tailored to meet their specific postoperative needs. The group includes four males and three females, reflecting a balanced gender distribution. These patients ranged in age from 1.5 to 6 years and weighed between 4 to 14 kg. HFNC flow rates were carefully calculated based on each child’s weight, ranging from 8 LPM for the lightest child to 28 LPM for the heaviest, to ensure effective and safe respiratory support. The duration of HFNC therapy also varied widely from 8 hours to 48 hours, depending on the severity of their condition and their specific recovery trajectories following major surgeries such as Glenn and Senning operations, and repairs for Tetralogy of Fallot (TOF) and Ventricular Septal Defect (VSD). This strategic customization of HFNC settings highlights the rigorous clinical approach to optimizing postoperative recovery for each patient according to their unique needs.

Table 1: Patient Demographics and HFNC Settings

Table 2 captures the clinical outcomes of HFNC therapy by presenting key respiratory and cardiac parameters before and after its application across seven pediatric patients following cardiac surgery. The data highlight a consistent improvement across all measured indices post-HFNC therapy, demonstrating the effectiveness of this intervention. Pre-HFNC therapy, the PCO2 levels were relatively high across the cohort, ranging from 43.8 to 52.4 mmHg, indicative of respiratory distress. Post-HFNC, these levels decreased significantly, with a range of 41.0 to 44.8 mmHg, showing enhanced CO2 clearance. Respiratory rates also improved markedly, dropping from pre-treatment highs such as 56 breaths per minute to more manageable levels around 26 to 38 breaths per minute post-treatment. Heart rates, too, showed a decrease, reflecting reduced physiological stress, from pre-HFNC rates of up to 142 beats per minute to a calmer range of 106 to 128 beats per minute post-HFNC. Systolic blood pressure remained stable or showed slight improvements, ensuring that the HFNC therapy did not compromise hemodynamic stability. Oxygen saturation levels saw an overall increase, moving from lower levels like 68% pre-HFNC to at least 70% or higher post-HFNC, which underscores the effectiveness of HFNC in enhancing oxygenation. Lactate levels, indicating metabolic stress, also improved across the board, further validating the therapeutic benefit of HFNC in this pediatric postoperative setting. These outcomes collectively illustrate the substantial benefits of HFNC in supporting the recovery of young cardiac surgery patients by improving breathing, stabilizing heart function, and enhancing overall metabolic health.

Table 2: Clinical Parameters Before and After HFNC Therapy

Table 3 provides a statistical summary of the physiological changes observed in pediatric patients following the application of High Flow Nasal Cannula (HFNC) therapy, documenting significant improvements across all major respiratory and cardiac parameters. The table illustrates that the average partial pressure of carbon dioxide (PCO2) in the blood decreased from 47.33 ± 2.95 mmHg before HFNC to 42.87 ± 1.45 mmHg afterwards, with a statistically significant p-value of 0.004, indicating a substantial enhancement in the patients' ability to expel CO2. Respiratory rates saw a remarkable reduction, averaging 48.14 ± 4.98 breaths per minute pre-HFNC and decreasing to 31.43 ± 3.95 post-HFNC, highlighting the therapy’s effectiveness in easing respiratory effort (p < 0.001). Heart rate also normalized significantly, dropping from an average of 134.00 ± 9.93 bpm before HFNC to 115.71 ± 7.25 bpm post-HFNC (p = 0.001), reflecting reduced stress and better overall cardiac stability.

Additionally, the average systolic blood pressure (SBP) slightly decreased from 79.43 ± 6.19 mmHg pre-HFNC to 74.86 ± 8.71 mmHg post-HFNC (p = 0.043), showing that HFNC therapy can be administered safely without adversely affecting hemodynamic stability. Improvements in oxygen saturation were also noteworthy; average levels increased from 85.14% ± 10.95 pre-HFNC to 87.43% ± 11.00 post-HFNC (p < 0.001), suggesting better oxygen delivery and uptake. Finally, the average lactate levels, which indicate metabolic stress, improved from 2.80 ± 0.81 mmol/L before HFNC to 1.90 ± 0.40 mmol/L after (p = 0.009), pointing to an enhanced metabolic condition. These comprehensive data underscore the clinical benefits of HFNC in supporting crucial physiological functions in pediatric patients post-cardiac surgery, facilitating a smoother and potentially quicker recovery.

Table 3: Summary of Physiological Parameters Before and After HFNC Therapy

High Flow Nasal Cannula (HFNC) therapy has emerged as a transformative approach in the management of pediatric patients following cardiac surgeries. This non-invasive ventilation strategy has shown potential in improving oxygenation and comfort, thereby reducing the likelihood of reintubation in vulnerable populations. Our study's results align with and extend the findings from prior researches, which documented significant reductions in PCO2 and respiratory rates post-HFNC application in a pediatric intensive care setting.^8-10 The consistent decrease in respiratory rates and PCO2 levels across our cohort underscores HFNC's efficacy in enhancing alveolar ventilation and respiratory mechanics after complex cardiac procedures.

The improvements in respiratory and cardiac parameters highlighted in our study bear similarities to outcomes observed by previous studies, where HFNC was credited with stabilizing respiratory patterns in post-cardiac surgery pediatric patients.^11-13 Notably, our findings of reduced heart rates post-HFNC application suggest a decrease in sympathetic nervous system activation, a phenomenon also observed by other studies, who posited that effective respiratory support reduces physiological stress.^8,12,14

Our study further documents a noteworthy normalization of heart rates and slight reductions in systolic blood pressure, reflecting diminished cardiorespiratory workload and potentially lower myocardial oxygen consumption post-HFNC therapy. These aspects are particularly crucial in a pediatric cardiac population where myocardial protection is paramount for recovery. The stable or improved systolic blood pressure readings align with the observations by previous researches, which reported hemodynamic stability as a significant benefit of HFNC use in postoperative cardiac children.^11,12,15

The incremental improvements in oxygen saturation noted in our study participants also highlight HFNC’s role in enhancing pulmonary gas exchange. This is consistent with the findings from earlier studies, who observed improved oxygen delivery in pediatric patients under HFNC therapy, attributing it to reduced work of breathing and better alveolar recruitment.^1,16 Furthermore, the reduction in lactate levels we observed suggests an alleviation of metabolic stress, mirroring the metabolic improvements noted in pediatric studies.^1,14,16

The clinical implications of these physiological improvements are substantial. By effectively reducing respiratory and cardiac stress, HFNC therapy may expedite the recovery process in pediatric cardiac patients, as supported by our findings and parallel studies.^1,12,13,17 The ability to maintain physiological stability through non-invasive means can also diminish the length of ICU stays and potentially reduce healthcare costs associated with postoperative care.

Limitations

While the results are promising, the current study shares common limitations, such as the relatively small sample size and the observational nature of the study design. Further, larger randomized controlled trials are needed to fully ascertain the benefits and define standardized protocols for HFNC usage in this high-risk population.

In conclusion, the data from this study substantiate the growing body of evidence that supports the use of HFNC therapy as a valuable component of postoperative care in pediatric cardiac patients. By improving key physiological parameters, HFNC therapy not only enhances immediate postoperative stability but also sets the stage for a safer and potentially quicker recovery pathway. These findings contribute to the nuanced understanding of HFNC's role in pediatric care, advocating for its broader application and integration into post-cardiac surgery recovery protocols.

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