From the Guidelines
For patients with restrictive ventilatory defects after scoliosis surgery, optimal mechanical ventilation settings typically include low tidal volumes of 6-8 mL/kg ideal body weight and PEEP of 5 cm H2O, which can be individualized thereafter. The initial ventilator settings should be tailored to the patient's specific needs, taking into account their predicted body weight and respiratory mechanics. According to the international expert panel-based consensus recommendations 1, a low-tidal-volume protective-ventilation strategy (6-8 ml/kg predicted body weight) and lower inspiratory pressures (plateau pressure < 30 cm H2O) are recommended to reduce postoperative pulmonary complications.
Some key considerations for mechanical ventilation in these patients include:
- Using a dedicated score for preoperative pulmonary risk evaluation, as recommended by the consensus guidelines 1
- Implementing individualized mechanical ventilation to improve intraoperative respiratory function and prevent postoperative pulmonary complications 1
- Avoiding zero end-expiratory pressure (ZEEP) and using appropriate PEEP and recruitment maneuvers to improve intraoperative respiratory function and prevent postoperative pulmonary complications 1
- Monitoring for and preventing upper airway obstruction during induction of anesthesia, as recommended by the consensus guidelines 1
- Using the lowest possible fraction of inspired oxygen (FiO2) to achieve a peripheral oxygen saturation (SpO2) of 94% or higher, as recommended by the consensus guidelines 1
The most recent and highest quality study on this topic is the international expert panel-based consensus recommendations published in the British Journal of Anaesthesia in 2019 1. This study provides a comprehensive review of the current evidence and expert opinion on lung-protective ventilation for surgical patients, including those with restrictive ventilatory defects after scoliosis surgery.
In terms of specific ventilation settings, the guidelines recommend:
- Tidal volumes of 6-8 mL/kg predicted body weight
- PEEP of 5 cm H2O, which can be individualized thereafter
- Plateau pressures < 30 cm H2O to prevent barotrauma
- Higher respiratory rates (18-25 breaths/minute) to maintain adequate ventilation
- FiO2 titrated to maintain SpO2 > 92% while avoiding oxygen toxicity
Overall, the goal of mechanical ventilation in patients with restrictive ventilatory defects after scoliosis surgery is to provide adequate ventilation while minimizing the risk of lung injury and postoperative pulmonary complications. By following the recommended ventilation settings and guidelines, clinicians can help to improve patient outcomes and reduce morbidity and mortality.
From the Research
Ideal Mechanical Ventilation Settings
The ideal mechanical ventilation (mech vent) settings for a patient with a restrictive ventilatory defect after scoliosis surgery are not explicitly stated in the provided studies. However, the following points can be considered:
- Patients with neuromuscular scoliosis or those with preoperative forced expired volume in 1 second (FEV1) <40% predicted are at higher risk for prolonged postoperative mechanical ventilation 2, 3.
- Preoperative pulmonary function tests, such as FEV1, vital capacity (VC), inspiratory capacity (IC), maximal inspiratory pressure (MIP), and total lung capacity (TLC), can help predict the need for prolonged postoperative mechanical ventilation 2, 3.
- The use of low tidal volume (Vt) ventilation may result in higher patient-ventilator dyssynchrony, which can be reduced by using adaptive pressure-control (APC) mode instead of volume assist-control (VC) mode 4.
Ventilatory Settings Considerations
When considering ventilatory settings for patients with restrictive ventilatory defects after scoliosis surgery, the following points should be taken into account:
- Tidal volume size: Lower Vt sizes may result in higher patient-ventilator dyssynchrony, but may be necessary to prevent lung injury 4.
- Ventilator mode: APC mode may be preferred over VC mode to reduce dyssynchrony, but requires careful monitoring to avoid larger-than-target delivered volumes 4.
- Inspiratory time and flow: These settings should be adjusted to minimize dyssynchrony and ensure adequate ventilation.
Risk Factors for Prolonged Mechanical Ventilation
The following risk factors for prolonged mechanical ventilation after scoliosis surgery have been identified: