O1) What is Althesin?
- Intravenous hypnotic agent introduced in 1970s
- Mixture of alphaxalone and alphadolone, both steroids, dissolved in Cremophor EL
- Rapid onset, short duration, hemodynamic stability and rapid recovery
- Became obsolete because of increased incidence of allergic and anaphylactic reactions, mainly due to the stabilizing agent
- Recently, alphaxalone has been reformulated with cyclodextrin
- What are the recruitment manoeuvres which can be used perioperatively?
- Alveolar recruitment manoeuvre (ARM) under anaesthesia is what sigh is for spontaneously breathing awake persons. ARM is commonly used in ICU in the ventilatory management of injured lungs like ARDS. A normal person has 9-10sighs/min and sigh is a
- General anaesthesia alone favours a tendency for reduction in FRC and a tendency for alveolar collapse. This tendency is enhanced by obesity, preexisting respiratory dysfunction, laparoscopic procedures due to pneumoperitoneum, Trendelenburg position and high inspired FiO2 (this is one of the reasons why simply increasing FiO2 to manage desaturation can be counterproductive)
- Aim is to open the collapsed alveoli or prevent alveolar collapse during general anaesthesia
- It could be a) Sustained manual hyperinflation at a set peak airway pressure 930 to 40cmH2O), also achieved by partial closure of APL valve followed by Positive end expiratory pressure or b) Incremental PEEP.
- Introperatively, when SpO2 starts dropping, recruitment manoeuvres should be considered as one of the strategies of improving oxygenation. The opening of collapsed alveoli (recruitment) leads to reduction in ventilation perfusion mismatch.
- Different studies have utilized different time duration for which the increased airway pressure is sustained ( from 6sec to 40 sec), single vs multiple hyperinflations per minute and hyperinflation followed by PEEP of 10cmH2O. Addition of PEEP helps to sustain the beneficiary effects of hyperinflation.
- Indicators of successful recruitment is indicated by a) increase in oxygen saturation b) increase in pulmonary compliance, static and dynamic, as indicated by increased expired tidal volume during pressure controlled ventilation c) CT evidence
More from 1)Anesthesiology 2010; 113: 1310-19, 2) Respiratory Care 2015, April Vol 60, No 4, P610 -620
03 What are the main disadvantages of RAE tube?
- Length at the angulation may not be appropriate in a given patient which means that fixing the tube at the angulation can lead to endobronchial intubation, especially during neck flexion
- Suctioning is difficult
- Using RAE tube over a fiberscope is more difficult
- Some of the RAE tubes are extremely soft predisposing for compression during maintenance phase
- Increased resistance to spontaneous ventilation (usually at the end of procedure)