|LETTER TO EDITOR|
Unseen complication of the exhausted soda lime
Deepak Dwivedi, Saurabh Sud, Sadhan Sawhney, Shyam P Panjiyar
Department of Anesthesia and Critical Care, Command Hospital (Southern Command), Pune, Maharashtra, India
|Date of Web Publication||11-Feb-2019|
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dwivedi D, Sud S, Sawhney S, Panjiyar SP. Unseen complication of the exhausted soda lime. Indian J Anaesth 2019;63:150-1
|How to cite this URL:|
Dwivedi D, Sud S, Sawhney S, Panjiyar SP. Unseen complication of the exhausted soda lime. Indian J Anaesth [serial online] 2019 [cited 2019 Feb 12];63:150-1. Available from: http://www.ijaweb.org/text.asp?2019/63/2/150/251974
During general anaesthesia an average adult produces 10–12 l of carbon dioxide per hour. Ralph Waters in 1923 pioneered the use of soda lime for chemically absorbing carbon dioxide. Approximately 100 g of soda lime absorbs around 26 l of carbon dioxide. Soda lime by removing carbon dioxide from fresh gas flow helps in recirculating the unused gases back into the circle system. This helps in economically reducing the requirement of fresh gas flow (oxygen, nitrous, and inhalation agents), and thus decreases pollution in operation theatre. We present here reporting of an unusual incident of an excessive water collection in the soda lime canister assembly at the anaesthesia workstation.
A 56-year-old lady was administered general anaesthesia with continuous epidural analgesia for total abdominal hysterectomy. After 25 min into surgery, monitoring showed increased peak airway pressure from the baseline of 16 to 28 cm H2O and increase in end-tidal carbon dioxide (ETCO2) from the initial value of 35 to 46 mmHg with normal wave morphology of the capnogram not touching the baseline, indicating toward rebreathing. The heart rate (HR) and mean arterial pressure (MAP) showed more than 25% variation from the baseline.
At this juncture the probable causes of the increased airway pressure such as excessive tidal volume, high inspiratory flow rate, kinking of endotracheal tube, and endobronchial intubation were ruled out and patient factors such as obesity, head down position, pneumoperitoneum, tension pneumothorax, and bronchospasm were also excluded. On inspection, the faulty packing of soda lime canister was observed in both upper and lower canisters with 20% of space left empty. Moreover, there was a presence of totally exhausted soda lime in the upper canister, and the lower canister was warm to touch with water levels between the outer wall of the lower canister and the inner wall of the canister assembly [Figure 1]a and [Figure 1]b. Further to this, each time when the bellows moved, it resulted in water being sucked in and out of the canister with bubbling evident in the canister assembly [[Figure 1]a and [Video 1] (online)]. The soda lime was changed and when inspected revealed completely exhausted (white) dry soda lime granules of the upper canister in comparison to wet and less exhausted lower canister soda lime granules [Figure 1]b. Following the change of soda lime, patient's peak airway pressure, ETCO2, HR, and MAP stabilised and the rest of the surgery proceeded uneventfully.
|Figure 1: (a) Excessive water bubbling between the outer wall of lower soda lime canister and the inner wall of the canister assembly. (b) The exhausted dry soda lime in the upper canister and the wet soda lime in the lower canister|
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Regeneration/peaking occurs because of surface regeneration of active hydroxides at the soda lime granules surface. The amount of regeneration depends on the duration of rest given to soda lime and this may be the explanation of the reappearance of the original pink color next morning in our case after its continuous use a day before the incident.
Explanation for both rebreathing leading to hypercapnia and collection of excessive water could be due to channeling, which led to nonhomogenous flow of gases that occurs due to incorrect packing of soda lime in the canister. The gas as well as the moisture collected from the exhaustion of the upper canister took the path of the least resistance forming channels and bypassing majority of the soda lime granules and hence moisture was collected in large quantity by gravity into the canister assembly. Presence of the excessive moist granules led to the phenomenon called "caking," which increased the peak airway pressure in our case., Therefore, careful marking of the date of change on the canister alone cannot guarantee prevention of such phenomenon, but utmost vigilance, care during refilling of canister, and knowing the total duration of use of the soda lime the day before the surgery should help in preventing such incidents.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
Stolp BW, Moon RE. Sodasorb CO2 Absorbents Manual – Shearwater Research. [monograph on the internet]. Cambridge: W.R Grace and Co.- Conn; 1993. Available from: https://www.shearwater.com/wp-content/uploads/2012/08/Sodasorb_Manual.pdf. [Last cited on 2018 Aug 23].