Safe Apnea Time Research Articles

Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) in children: a randomized controlled trial

BackgroundTransnasal humidified rapid-insufflation ventilatory exchange (THRIVE) was introduced to adult anaesthesia to improve the safety of airway management during apnoea before intubation. The objective of our study was to determine whether THRIVE safely prolongs apnoeic oxygenation in children. MethodsThis was a randomized controlled trial in 48 healthy children, with normal airways and cardiorespiratory function, in age groups 0–6 and 7–24 months, 2–5 and 6–10 yr old, presenting for elective surgery or imaging under general anaesthesia. All children were induced with sevoflurane, O2, and N2O, followed by muscle relaxation with rocuronium, and standardized preoxygenation with bag-and-mask ventilation. The control arm received jaw support during apnoea, whereas the THRIVE arm received jaw support during apnoea and age-specific flow rates. The primary outcome was to demonstrate that children allocated to THRIVE maintain transcutaneous haemoglobin saturation at least twice as long as the expected age-dependent apnoea time in the control group. ResultsBoth study arms (each n=24) were similar in age and weight. The apnoea time was significantly shorter in the control arm: average 109.2 (95% CI 28.8) s in the control arm and 192 s in the THRIVE arm (0–6 months), 147.3 (95% CI 18.9) and 237 s (7–24 months), 190.5 (95% CI 15.3) and 320 s (2–5 yr), and 260.8 (95% CI 37.5) and 430 s (6–10 yr), respectively. Average transcutaneous haemoglobin saturation remained at 99.6% (95% CI 0.2) during THRIVE. Transcutaneous CO2 increased to a similar extent in both arms, with 2.4 (95% CI 0.5) mm Hg min−1 for the control arm and 2.4 (95% CI 0.4) mm Hg min−1 for the THRIVE arm. ConclusionTransnasal humidified rapid-insufflation ventilatory exchange prolongs the safe apnoea time in healthy children but has no effect to improve CO2 clearance. Clinical trial registrationACTRN12615001319561.

Abstract PR532

Background & Objectives: Preoxygenation is used to maximise alveolar oxygen reserves prior to induction of anaesthesia thus allowing a longer safe apnoea time prior to securing the airway. A barrier to routine preoxygenation is the delay that such practice might incur in the time to induction of anaesthesia1. Optimal preoxygenation is defined as FeO2≥0.9. However, this may predispose to alveolar absorption atelectasis and may be unachievable within an acceptable timeframe. Therefore, a FeO2≥0.8 is a compromise target. The purpose of this study was to determine whether Non-Invasive Ventilation (NIV) would achieve a targeted Fractional Expired Oxygen (FeO2) concentration faster than standard ventilation (SV) during preoxygenation prior to induction of anaesthesia. Materials & Methods: This was a cross-over study of 20 adult patients (age range 18-80) undergoing elective surgery. The patients were recruited via the Pre-Operative Assessment Clinic to undergo a controlled comparison of two preoxygenation techniques. SV consisted of 10L/min of 100% oxygen via tight fitting facemask. NIV consisted of 10L/min of 100% oxygen via tight fitting facemask, with 5cmH20 pressure support and 5cmH20 positive end expiratory pressure. Each patient was preoxygenated using both techniques. The sequence of preoxygenation was randomised, with sufficient time interval between techniques to allow alveolar gas composition to return to baseline. Patients were placed in the supine position and initial FeO2 after the first breath was recorded. The time the patient reached a FeO2 0.8 was recorded. An additional 2 minutes were allowed for the patient to reach 0.9. If this was not achieved the maximal FeO2 was recorded. At the end of the study patients were asked for their preferred technique. Results: Of the 20 patients recruited 14 were male and 6 female. The average age was 60 years. The mean time to achieve FeO20.8 using NIV (57 seconds: range 30 - 105 sec) was faster than SV (148 seconds: range 50 - 440 sec). The mean difference was 92 seconds faster for NIV (95% confidence interval: range 43.3 -142.6; P=0.0009). In addition, when subjected to NIV, 15/20 patients (75%) achieved FeO2 0.9 in a further 2 minutes, compared to only 6/20 patients (30%) in the standard preoxygenation group. 78% of patients preferred NIV to standard technique (P=0.0184).Conclusion: This study demonstrates that NIV is a technique that achieves a FeO2 0.8 faster and is better tolerated than standard preoxygenation.

Преоксигенация: можно ли сделать меру безопасности менее опасной?

While providing reserve time for dificult airway management, preoxygenation with pure oxygen increases the risk of pulmonary complications due to absorption atelectases. The authors explored when it could be appropriate to prevent atelectases by preoxygenation with decreased FiO₂. ASA I-II elective gynecological surgery patients were randomized among five groups (n = 22 each) with preoxygenation using FiO₂ 100, 70, 60, 60% + PEEP 5 mbar and 50%. Even FiO₂ 70% led to decrease. in safe apnea time (i.e. time interval to Sp²O₂ 95%) by two, while FiO₂ 50% - by more than three times. Furthermore, in five similar additional groups of women with same techniques ofpreoxygenation (n = 10 each) it was shown that for FiO₂ 5 70% very fast pattern of SpO2 fall after the first change ofpulseoxymeter figure (100% by 99%) is typical: interval to SpO2 90% was less than 1 min, while for FiO₂ 100% it lasts for 200 s. Since critical problem is "Cannot intubate, cannot ventilate", the authors tried to focus on the difficultfacemask ventilation prognosis. In the group of 71 elective general surgery patients (31 males, 40 females, ASA I-III) original prognostic model based on seven simple bedside tests (removable dentures, beard, snoring, Mallampati class 2-4, age > 50 y.o., BM > 30 kg/m², sternomental distance < 12 cm) demonstrated the reliability of difficult facemask ventilation negative prognosis of 97,5%. The authors suggest that only in patients with reliable prognosis of easy facemask ventilation prevention ofpulmonary complications by preoxygenation with FiO₂ 50-60% could be safely recommended.

ProSeal™ LMA Increases Safe Apnea Period in Morbidly Obese Patients Undergoing Surgery under General Anesthesia

Morbidly obese patients are at risk of hypoxemia at the time of induction of anesthesia. The aim of this study was to assess the possible increase in the safe apnea time with the use of ProSeal laryngeal mask airway (PLMA) as a conduit prior to laryngoscope-guided intubation in morbidly obese patients undergoing surgery under general anesthesia. Hundred patients with BMI greater than 35 kg/m2, undergoing surgery under general anesthesia, were randomly divided to receive either PLMA or facemask with oropharyngeal airway (FM) as the airway device. Following preoxygenation with 100% oxygen with continuous positive airway pressure of 10 cm H2O, in ramp position for 5 min the patients were made apneic. From start of apnea to the time to reach SpO2 to 92% was recorded as safe apnea time. Ventilation was initiated and time to reach SpO2 of 100% was recorded as recovery time. The mean safe apnea time was 205 (96-320)s in FM vs. 337 (176-456) s in PLMA (P = 0.0000). The mean recovery period was 49 (36-68)s in FM vs. 42(30-56)s in PLMA groups (P = 0.0000). Arterial blood gas analysis showed significant difference in pO2 between the two groups. The use of ProSeal laryngeal mask airway prior to laryngoscope-guided intubation is beneficial in increasing safe apnea period and achieving faster recovery from hypoxemia in morbidly obese patients.

Desaturation following rapid sequence induction using succinylcholine vs. rocuronium in overweight patients

Rapid sequence induction may be associated with hypoxemia. The purpose of this study was to investigate the possible difference in desaturation during rapid sequence induction in overweight patients using either succinylcholine or rocuronium. Sixty patients with a body mass index (BMI) between 25 and 30 kg/m², American Society of Anesthesiologists class I or II, undergoing general anesthesia were randomly divided into a succinylcholine group and a rocuronium group. After a 3-min preoxygenation, patients received rapid sequence induction of general anesthesia with midazolum-fentanyl-propofol and succinylcholine (1.5 mg/kg) or rocuronium (0.9 mg/kg). Ventilation was not initiated until oxygen saturation declined to 92%. We measured the times when oxygen saturation reached 98%, 96%, 94% and 92%. Safe Apnea Time was defined as the time from administration of neuromuscular blocking drugs to oxygen saturation fell to 92%. The recovery period was defined as the time from initiation of ventilation until oxygen saturation was 97%. Arterial blood gases were taken at baseline, after preoxygenation and at 92% oxygen saturation. The mean Safe Apnea Time (95% CI) was 283 (257-309) s in succinylcholine vs. 329 (303-356) s in rocuronium (P=0.01). The mean recovery period (95% CI) was 43 (39-48) s in succinylcholine vs. 36 (33-38) s in rocuronium (P=0.002). Blood gas analysis showed no difference between the two groups. Succinylcholine was associated with a significantly more rapid desaturation and longer recovery of oxygen saturation than rocuronium during rapid sequence induction in overweight patients.

Succinylcholine and Morbid Obesity: The Debate Continues…

Despite its potential adverse side effects, succinylcholine has been used in clinical anesthetic practice for more than 50 years. Its benefits include rapid onset (<1 min) with excellent tracheal intubating conditions and rapid recovery from paralysis [1]. Although potential replacements for succinylcholine have been sought, no other neuromuscular blocking agent has yet been equal to succinylcholine in its onset time and time to full recovery from block [2]. Currently, the agent deemed most likely to replace succinylcholine is rocuronium. Although its onset to paralysis is almost equivalent to succinylcholine, rocuronium has a much longer (30–50min) duration of action [3]. For a normal weight surgical patient with a normal airway and a long safe apnea time (time from paralysis until oxyhemoglobin desaturation), rocuronium can be substituted for succinylcholine. This is not the case for the morbidly obese patient in whom rapid access to a potentially difficult airway under the best possible laryngoscopy conditions is always necessary [4]. In several studies, it has been demonstrated that although rocuronium and succinylcholine are equivalent in achieving “good” intubating conditions, for consistently excellent conditions, succinylcholine is always a better choice [5]. Because of its short duration of action, in our opinion, succinylcholine is indicated for every morbidly obese patient since laryngoscopy may not always be successful, mask ventilation can be challenging, and safe apnea time is very short, increasing the need for rapid emergence from the block. The reversal agent sugammadex can decrease the duration of action of rocuronium, and its release into clinical practice has led some to state that a replacement for succinylcholine has finally been found [1]. However, sugammadex is not available in the USA. In Europe where sugammadex is currently in use, a single reversal dose costs several hundred dollars (M. Margarson, Chichester, UK, personal communication) compared to succinylcholine which is very inexpensive. Although the more serious side effects of succinylcholine (significant hyperkalemia, anaphylaxis, malignant hyperthermia) can be life-threatening, their occurrence is extremely rare. The more common side effects of succinylcholine are usually minor, and in our opinion, the benefits of succinylcholine in the morbidly obese surgical patient far outweigh any reason not to use it.