• Users Online: 3162
  • Print this page
  • Email this page

 Table of Contents    
Year : 2016  |  Volume : 60  |  Issue : 12  |  Page : 965-966  

Halothane: I am still there

Department of Anaesthesiology, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India

Date of Web Publication9-Dec-2016

Correspondence Address:
Pooja Bihani
Department of Anaesthesiology, All India Institute of Medical Sciences, Jodhpur - 342 005, Rajasthan
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0019-5049.195505

Rights and Permissions

How to cite this article:
Bihani P, Choudhary D, Bhatia PK, Mohammed S. Halothane: I am still there. Indian J Anaesth 2016;60:965-6

How to cite this URL:
Bihani P, Choudhary D, Bhatia PK, Mohammed S. Halothane: I am still there. Indian J Anaesth [serial online] 2016 [cited 2021 Jan 21];60:965-6. Available from: https://www.ijaweb.org/text.asp?2016/60/12/965/195505


Modern anaesthesia workstation uses advanced electronic and software technologies to provide low-flow anaesthesia which requires monitoring of oxygen (O 2 ), carbon dioxide (CO 2 ) and volatile anaesthetic agents (VAA). These advanced gas monitoring (AGM) devices help in accurate titration of delivery of anaesthetics to patients. However, the erroneous reading of agents by these monitors may incite alteration of vapouriser output with inherent danger of light anaesthesia or VAA toxicity. In analyses conducted by Cassidy et al. on critical incidents related to anaesthetic equipment, 13.4% of incidences were reported with gas monitoring. [1] We report a case of erroneous detection of halothane despite the fact that the agent was never used with this workstation.

A 45-year-old patient was planned to be operated for laparoscopic abdominal hysterectomy under general anaesthesia, for which Drager Fabius GS premium anaesthesia workstation was used. The patient was induced with intravenous propofol and fentanyl. Anaesthesia was maintained with O 2 -air mixture and isoflurane, maintaining its end-tidal concentration at 1.2. Just before the end of surgery, isoflurane was turned off. Meanwhile, monitor started showing halothane concentration up to 1.3% and residual isoflurane concentration of 0.2% simultaneously. The minimum alveolar concentration (MAC) value increased to 1.7 despite no agent being administered [Figure 1]. Halothane was never used with this workstation and anywhere in the operation theatre (OT) complex. It was considered as erroneous reading, and the patient was extubated when clinical recovery was appreciable as MAC value was not considered reliable in this case.
Figure 1: Erroneous display of halothane

Click here to view

The agent analyser with this workstation works at the principle of pulsed, non-dispersive infrared radiation (IR) method and a multispectral detector. IR absorption is a common method of gas analysis for measuring concentrations of CO 2 , nitrous oxide (N 2 O) and VAA in gas mixture during anaesthesia. Different wavelengths of IR light are used to determine concentrations of CO 2 , N 2 O and VAA. Although the same wavelength is used for all current VAAs, different sensitivities are set for each agent, typically the highest for halothane and lowest for sevoflurane. Furthermore, the refractive indices of halothane, isoflurane and sevoflurane are overlapping (1603.2, 1563.3 and 1538.3, respectively), and complex mathematical calculations are used to identify and measure them. [2]

Switching over of anaesthetic (one for induction followed by other agent for the maintenance of anaesthesia), vaporiser filling with an incorrect agent, the absence of scavenging system leading to accumulation of anaesthetic in OT and anaesthesia machine leading to false agent identifications were explanations given by service engineer for this problem. As halothane is not available anywhere in OT complex and only isoflurane was used throughout surgery, so above possibilities were ruled out. Hawkes et al. reported wrong detection of halothane during trigger-free anaesthesia in malignant hyperthermia susceptible patient. It was a factitious reading resulting from incorrect identification of patient's expired methane as halothane by agent analyser. [3] Similarly, halothane misinterpretation for hydrofluoroalkane-based medical aerosol propellant by agent analyser has been reported. [4],[5] Agent analyser using a lower wavelength of IR spectra (3-5 μm) range can lead to false interpretation of halothane for methane, water vapour and isopropyl alcohol, etc. Above conditions could not explain this case as agent analyser with this workstation uses a higher wavelength of IR spectra for VAA discrimination.

On examination, we noted condensation in sampling line and the presence of water in water trap of gas analyser. After changing this part, sensor started identifying agents correctly. Water vapour and secretions in the sampling line of side stream could damage expired gas membrane of AGM sensor. This could be an explanation of agent misidentification in our case.

It is recommended that water trap and sensor of gas analyser should be periodically checked and replaced according to manufacturer's recommendation, and sensors with higher wavelengths (10-13 μm) which do not cross-react with gases exhaled from patients such as methane, acetone, alcohol and CO 2 should be used with closed circuit anaesthesia.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Cassidy CJ, Smith A, Arnot-Smith J. Critical incident reports concerning anaesthetic equipment: Analysis of the UK National Reporting and Learning System (NRLS) data from 2006-2008. Anaesthesia 2011;66:879-88.  Back to cited text no. 1
Wallroth CF, Gippert KL, Ryschka M, Falb W, Hattendorff HD, Schramm B, et al. Refractive indices for volatile anesthetic gases: Equipment and method for calibrating vaporizers and monitors. J Clin Monit 1995;11:168-74.  Back to cited text no. 2
Hawkes CA. Factitious halothane detection during trigger-free anesthesia in a malignant hyperthermia susceptible patient. Can J Anaesth 1999;46:567-70.  Back to cited text no. 3
Levin PD, Levin D, Avidan A. Medical aerosol propellant interference with infrared anaesthetic gas monitors. Br J Anaesth 2004;92:865-9.  Back to cited text no. 4
Shah SB, Hariharan U, Bhargava AK. Anaesthetic in the garb of a propellant. Indian J Anaesth 2015;59:258-60.  Back to cited text no. 5
[PUBMED]  Medknow Journal  


  [Figure 1]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
    Article Figures

 Article Access Statistics
    PDF Downloaded400    
    Comments [Add]    

Recommend this journal