Programming pressure support ventilation in pediatric patients in ambulatory surgery with a laryngeal mask airway

A comparison of the breathing apparatus deadspace associated with a supraglottic airway and endotracheal tube using volumetric capnography in young children

Background

Supraglottic airway (SGA) devices including the air-Q^® are being used with increasing frequency for anesthesia in infants and younger pediatric patients. To date, there is minimal research documenting the potentially significant airway deadspace these devices may contribute to the ventilation circuit when compared to an endotracheal tube (ETT). The aim of this study was to evaluate the airway apparatus deadspace associated with an air-Q^® versus an ETT in young children.

Methods

In a prospective cohort study, 59 patients between 3 months and 6 years of age, weighing between 5 and 20 kg, scheduled for outpatient urologic or general surgery procedures were recruited. An air-Q^® or ETT was inserted at the discretion of the attending anesthesiologist, and tidal volume, positive end expiratory pressure, respiratory rate, and end-tidal CO₂ were controlled according to protocol. Airway deadspace was recorded using volumetric capnography every 2 min for 10 min.

Results

Groups were similar in demographics. There was a significant difference in weight-adjusted deadspace volume between the air-Q^® and ETT groups, 4.1 ± 0.8 ml/kg versus 3.0 ± 0.7 ml/kg, respectively (P < 0.001). Weight-adjusted deadspace volume (ml/kg) increased significantly with decreasing weight for both the air-Q^® and ETT groups.

Conclusions

In healthy children undergoing positive pressure ventilation for elective surgery, the air-Q^® SGA introduces significantly greater airway deadspace than an ETT. Additionally, airway deadspace, and minute ventilation required to maintain normocarbia, appear to increase with decreasing patient weight irrespective of whether a SGA or ETT is used.

Pressure support ventilation-pro decreases propofol consumption and improves postoperative oxygenation index compared with pressure-controlled ventilation in children undergoing ambulatory surgery: a randomized controlled trial

PURPOSE

The PSVPro mode is increasingly being used for surgeries under laryngeal mask airway owing to improved ventilator-patient synchrony and decreased work of breathing. We hypothesized that PSVPro ventilation mode would reduce consumption of anesthetic agents compared with pressure control ventilation (PCV).

METHODS

Seventy children between three and eight years of age undergoing elective lower abdominal and urological surgery were randomized into PCV group (n = 35) or PSVPro group (n = 35). General anesthesia was induced with sevoflurane and a Proseal LMA™ was inserted. Anesthesia was maintained with propofol infusion to maintain the entropy values between 40 and 60. In the PCV mode, the inspiratory pressure was adjusted to obtain an expiratory tidal volume of 8 mL·kg-1 and a respiratory rate of 12-20/min. In the PSVPRO group, the flow trigger was set at 0.4 L·min-1 and pressure support was adjusted to obtain expiratory tidal volume of 8 mL·kg-1. Consumption of anesthetic agent was recorded as the primary outcome. Emergence time and discharge time were recorded as secondary outcomes.

RESULTS

The PSVPro group showed significant reduction in propofol consumption compared with the PCV group (mean difference, 33.3 µg-1·kg-1·min-1; 95% confidence interval [CI], 24.2 to 42.2). There was decrease in the emergence time in the PSVPro group compared with the PCV group (mean difference, 3.5 min; 95% CI, 2.8 to 4.2) and in time to achieve modified Aldrete score > 9 (mean difference, 3.6 min; 95% CI, 1.9 to 5.2).

CONCLUSION

The PSVPro mode decreases propofol consumption and emergence time, and improves oxygenation index in children undergoing ambulatory surgery.

TRIAL REGISTRATION

Clinical Trial Registry of India (CTRI/2017/12/010942); registered 21 December, 2017.

Recruitment manoeuvres in anaesthesia: How many more excuses are there not to use them?

Pulmonary recruitment manoeuvres (RM) are intended to reopen collapsed lung areas. RMs are present in nature as a physiological mechanism to get a newborn to open their lungs for the first time at birth, and we also use them, in our usual anaesthesiological clinical practice, after induction or during general anaesthesia when a patient is desaturated. However, there is much confusion in clinical practice regarding their safety, the best way to perform them, when to do them, in which patients they are indicated, and in those where they are totally contraindicated. There are important differences between RM in the patient with adult respiratory distress syndrome, and in a healthy patient during general anaesthesia. Our intention is to review, from a clinical and practical point of view, the use of RM, specifically in anaesthesia.

Impact of high concentrations of sevoflurane on laryngeal reflex responses

BACKGROUND

Exaggerated defensive upper airway reflexes, particularly laryngospasm, may cause hypoxemic damage, especially in children. General clinical experience suggests that laryngeal reflex responses are more common under light levels of anesthesia, and previous clinical studies have shown an inverse correlation between laryngeal responsiveness and depth of hypnosis. However, this seems to be less obvious in children anesthetized with sevoflurane. The aim of this study was to assess the impact of high concentrations of sevoflurane on laryngeal and respiratory reflex responses in spontaneously breathing children. Accordingly, we tested the hypothesis that laryngeal and respiratory reflex responses were completely suppressed in spontaneously breathing children when anesthetized with sevoflurane 4.7% (=MAC_{ED95Intubation} ) as compared with sevoflurane 2.5% (=1 MAC).

METHODS

In this prospective observational study, we tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is diminished under high concentrations of sevoflurane. Following Ethics approval, trial registration, and informed consent, 40 children (3-7 years) scheduled for elective surgery participated in the trial. All children received sevoflurane 2.5% (1 MAC) and 4.7% (ED_95Intubation ) in random order with 5-min equilibration between the states. Under both conditions, distilled water was sprayed under bronchoscopic view onto the larynx. Potential laryngeal and respiratory reflex responses were assessed offline by a blinded reviewer.

RESULTS

Laryngospasm (episodes lasting >10 s) occurred in 12/38 (32%) of the patients anesthetized with sevoflurane 2.5%, vs 7/38 (18%) in those anesthetized with sevoflurane 4.7% (difference: OR 3.5; 95% CI [0.72-16.84], P = 0.18). All other reflex responses (coughing, expiration reflexes, and spasmodic panting) were infrequent and were similar among the examined concentrations.

CONCLUSION

Against our hypothesis, laryngospasm could still be observed in 18% of children under the higher concentration of sevoflurane (4.7%, ED_95Intubation ).

A comparison of 3 ventilation strategies in children younger than 1 year using a Proseal laryngeal mask airway: a randomized controlled trial

STUDY OBJECTIVE

To determine quantitative differences in several routinely measured ventilation parameters using a standardized anesthetic technique and 3 different ventilation modalities in patients younger than 1 year with a ProSeal laryngeal mask airway (PLMA).

DESIGN

Randomized prospective study.

SETTING

Tertiary care pediatric hospital.

PATIENTS

Thirty-nine American Society Anesthesiologists classifications 1 to 2, pediatric patients younger than 1 year.

INTERVENTIONS

Three different ventilation strategies (spontaneous ventilation [SV], pressure support ventilation [PSV], and pressure-controlled ventilation [PCV]) were randomly applied to patients who underwent a standardized mask induction with sevoflurane/oxygen and propofol 2 mg/kg and fentanyl 2 μg/kg administered intravenously followed by PLMA insertion. Patients were maintained on sevoflurane and N₂O.

MEASUREMENTS

We measured the differences in end-tidal CO₂ (etco₂), tidal volume (TV), and respiratory rate (RR) over time between SV, PSV, and PCV. These data were recorded at 5-minute intervals.

MAIN RESULTS

etco₂ (mm Hg) was not significantly higher in the SV vs PSV (P=2.11) and SV vs PCV (P=.24). TV (mL/kg) was significantly lower in SV vs PSV (P<.005) and SV vs PCV (P<.005). RR was not significantly higher in SV vs PSV (P=.43), but was significantly higher in SV vs PCV (P<.005). Three patients in the SV group and 1 patient in the PSV group failed to initiate SV and required PCV and were thus excluded from analysis.

CONCLUSIONS

All 3 modes of ventilation using a PLMA were safe in children younger than 1 year. Although we did not observe a statistically significant increase in etco₂, differences in TV and RR, and the small but significant incidence of apnea may make PSV or PCV more optimal ventilation strategies in children younger than 1 year when using a PLMA.

An ADARPEF survey on respiratory management in pediatric anesthesia

BACKGROUND

There have been recent changes with regard to tools and concepts for respiratory management of children undergoing general anesthesia.

OBJECTIVES

To determine the practice of pediatric anesthetists concerning: preoxygenation, breathing systems, ventilation modes, anesthetic agent and airway device, strategies for a general anaesthetic of less than 30 min using spontaneous respiration, and opinion about technical aspects of ventilation.

METHODS

Online questionnaire sent by e-mail to all the anesthetists registered on the mailing list of the French-speaking Pediatric Anesthetists and Intensivists Association (ADARPEF).

RESULTS

232 questionnaires (46%) were returned. More than 25% of anesthetists surveyed declared that they do not perform preoxygenation before induction for children <15 years old, apart from neonates and clinical specific situations. When performed, <65% chose a FiO2 higher than 80%. Inhalational induction with sevoflurane is the preferred mode of induction set at 6% or 8%, respectively, 69% [62-75] vs 25% [18-31]. For induction, the circle system was the most popular circuit used in all ages. The accessory breathing system-Mapleson B type-was predominantly used for neonates (44% [37-54]). For maintenance of an anesthesia lasting <30 min in spontaneous breathing, the use of laryngeal mask increased with age, and the endotracheal tube was reserved for neonates (40% [33-48]). Pressure support ventilation was rarely used from the beginning of induction but was widely used for maintenance, whatever the age-group. Results differed according to the type of institution.

CONCLUSION

Ventilation management depends on the age and institutions in terms of circuit, airway device or ventilation mode, and specific differences exist for neonates.

[The choice of a pediatric anesthesia ventilator]

The technology of anesthesia ventilators has substantially progressed during last years. The choice of a pediatric anesthesia ventilator needs to be led by multiple parameters: requirement, technical (pneumatic performance, velocity of halogenated or oxygen delivery), cost (purchase, in operation, preventive and curative maintenance), reliability, ergonomy, upgradability, and compatibility. The demonstration of the interest of pressure support mode during maintenance of spontaneous ventilation anesthesia makes this mode essential in pediatrics. In contrast, the financial impact of target controlled inhalation of halogenated has not be studied in pediatrics. Paradoxically, complex and various available technologies had not been much prospectively studied. Anesthesia ventilators performances in pediatrics need to be clarified in further clinical and bench test studies.

Anesthesia and spinal muscle atrophy

Spinal muscle atrophy (SMA) is autosomal recessive and one of the most common inherited lethal diseases in childhood. The spectrum of symptoms of SMA is continuous and varies from neonatal death to progressive symmetrical muscle weakness first appearing in adulthood. The disease is produced by degeneration of spinal motor neurons and can be described in three or more categories: SMA I with onset of symptoms before 6 months of age; SMAII with onset between 6 and 18 months and SMA III, which presents later in childhood. Genetics: The disease is in more than 95% of cases caused by a homozygous deletion in survival motor neuron gene 1 (SMN1).

PATHOPHYSIOLOGY

The loss of full-length functioning SMN protein leads to a degeneration of anterior spinal motor neurons which causes muscle weakness. Anesthetic risks: Airway: Tracheal intubation can be difficult. Respiration: Infants with SMA I almost always need postoperative respiratory support. Patients with SMA II sometimes need support, while SMA III patients seldom need support. Circulation: Circulatory problems during anesthesia are rare. Anesthetic drugs: Neuromuscular blockers: Patients with SMA may display increased sensitivity to and prolonged effect of nondepolarizing neuromuscular blockers. Intubation without muscle relaxation should be considered. Succinylcholine should be avoided. Opioids: These should be titrated carefully. Anesthetic techniques: All types of anesthetic technique have been used. Although none is absolutely contraindicated, none is perfect: anesthesia must be individualized.

CONCLUSION

The perioperative risks can be considerable and are mainly related to the respiratory system, from respiratory failure to difficult/impossible intubation.

Pressure support ventilation vs spontaneous ventilation via ProSeal™ laryngeal mask airway in pediatric patients undergoing ambulatory surgery: a randomized controlled trial

AIM

To investigate the advantages of using pressure support ventilation (PSV) vs spontaneous ventilation via ProSeal™ laryngeal mask airway in children undergoing ambulatory surgery.

BACKGROUND

In our ambulatory surgical unit, the use of unassisted spontaneous breathing via laryngeal mask airway is a common anesthetic technique during general anesthesia. However, this may be associated with inadequate ventilation. PSV is a ventilatory mode that is synchronized with the patient's respiratory effort and may improve gaseous exchange under general anesthesia.

MATERIALS AND METHODS

After the approval from the ethics committee, a randomized controlled trial involving 24 pediatric patients was conducted in our ambulatory surgical unit. They were randomized into two groups, namely Group PSV (receiving PSV) and Group SV (unassisted spontaneous ventilation). Outcome measures included intraoperative respiratory and hemodynamic parameters as well as recovery room data.

RESULTS

There were no significant differences in baseline characteristics between the two groups. Patients in Group PSV had lower ETCO(2) (42.8 ± 5.8 vs 50.4 ± 4.0, P = 0.001) and higher expiratory tidal volume per kg bodyweight (8.3 ± 1.8 ml kg(-1) vs 5.8 ± 0.8 ml kg(-1), P = 0.001) compared with patients in Group SV. There were no significant differences in other respiratory and hemodynamic parameters or recovery room data between the two groups.

CONCLUSION

Pressure support ventilation via ProSeal™ laryngeal mask airway during general anesthesia improves ventilation in pediatric patients undergoing ambulatory surgery. However, this did not translate to a difference in clinical outcome among our study patients.

Equipment and monitoring--what is in the future to improve safety?

There have been a number of recent developments in the practice of anesthesia and intensive care aimed at improving outcome in terms of reducing both morbidity and mortality, as well as other less-defined factors, such as quality of service provision. Significant advances have been made in airway devices such as pediatric tracheal tube designs, Microcuff(®) tracheal tubes, and new laryngoscopes. Noninvasive monitoring devices, including continuous hemoglobin analysis and near infrared spectrometry, are being increasingly used in pediatric anesthesia. Other, 'scaled-down' versions from adult anesthesia care, however, have not universally been shown to result in improved safety and outcomes in pediatric anesthesia.

Adaptive support ventilation for gynaecological laparoscopic surgery in Trendelenburg position: bringing ICU modes of mechanical ventilation to the operating room

BACKGROUND AND OBJECTIVE

The aim of the present study was to test the efficacy of adaptive support ventilation (ASV) to automatically adapt the ventilatory settings to the changes in the respiratory mechanics that occur during pneumoperitoneum and Trendelenburg position in gynaecological surgeries.

METHODS

We prospectively studied 22 ASA I women scheduled for gynaecological laparoscopic surgery in the Trendelenburg position. After intravenous induction of general anaesthesia, patients were ventilated with ASV, a closed-loop mode of mechanical ventilation based on the Otis formula, designed to automatically adapt the ventilatory settings to changes in the patient's respiratory system mechanics, while maintaining preset minute ventilation. Respiratory mechanics variables, ventilatory setting parameters and analysis of blood gases were recorded at three time points: 5 min after induction (baseline), 15 min after pneumoperitoneum and Trendelenburg positioning (Pneumo-Trend) and 15 min after pneumoperitoneum withdrawal (final).

RESULTS

A reduction of 44.4% in respiratory compliance and an increase of 29.1% in airway resistance were observed during the Pneumo-Trend period. Despite these changes in respiratory mechanics, minute ventilation was kept constant. ASV adapted the ventilatory settings by automatically increasing inspiratory pressure by 3.2 +/- 0.9 cmH(2)O (+19%), P < 0.01, respiratory rate by 1.3 +/- 0.5 breaths per minute (+9%) and the inspiratory to total time ratio (T(i)/T(tot)) by 43.3%. At final time, these parameters returned towards their baseline values. Adequate gas exchange was maintained throughout all periods. PaCO(2) increased moderately (+13%) from 4.4 +/- 0.6 (baseline) to 5.0 +/- 0.9 kPa (Pneumo-Trend), P < 0.01; and decreased slightly at final time (4.7 +/- 0.8 kPa), P < 0.05. Clinician's intervention was needed in only one patient who showed a moderate hypercapnia (PaCO(2) 6.9 kPa) during pneumoperitoneum.

CONCLUSION

In healthy women undergoing gynaecologic laparoscopy, ASV automatically adapted the ventilatory settings to the changes in the respiratory mechanics, keeping constant the preset minute ventilation, providing an adequate exchange of respiratory gases and obviating clinician's interventions.