An audit of intravenous access visibility and bispectral (BIS) use during total intravenous anaesthesia. Are we compliant with guidelines?

Abstract

Total intravenous anaesthesia (TIVA) use is becoming increasingly popular for a number of reasons, including quality of patient recovery, the possibility of an impact on cancer recurrence and environmental sustainability 1. However, the 5th UK National Audit Project NAP5 reported an association between TIVA and increased risk of accidental awareness during general anaesthesia (AAGA) 2. This risk occurs because pharmacological monitoring of drug delivery to the patient is not possible with TIVA, as it is for volatile anaesthetics. This means anaesthetists may be unaware of technical problems with drug delivery including accidental disconnection or displacement of the intravenous (i.v.) line. Three current guidelines recommend that the i.v. access site should be visible ‘where practical’ when TIVA is used; the Association of Anaesthetists minimum monitoring guidelines 3; the NAP5 report 2; and the Association of Anaesthetists/Society of Intravenous Anaesthesia TIVA guidelines 4. These publications also recommend processed EEG ‘depth of anaesthesia’ monitoring when TIVA is used with a neuromuscular blocking (NMB) drug and the TIVA guidelines recommend a lower threshold for its use when the i.v. access site is not continuously visible. We undertook a semi-blinded audit (i.e. the observed anaesthetists were not aware of the purpose of the audit) of 100 cases, across a range of surgical specialties and grades of anaesthetist. In 99 (99%) cases the cannula was in a vein in the hand and in one case it was in a vein in the foot. In 68% of cases, the patient's arms were at their sides. In 46% of cases the cannula being used for TIVA was not visible, in 11% it was also not accessible and in 43 (93%) of these cases it was judged to be not visible either out of necessity or due to surgical choice. Bispectral index (BIS) monitoring was used in 60% of cases: in 40 out of 41 (98%) when a NMB drug was used and in 20 out of 59 (34%) when no NMB drug was used. In 2 out of the 60 (4%) cases, BIS monitoring failed; in one the monitoring module failed and in one the BIS strip lost contact and was not accessible during surgery. In the one case where TIVA and NMB drugs were administered without BIS monitoring, this had been intended but was forgotten. In 16 cases, BIS was not used and the cannula was not visible. We noted no clear differences in practices between different grades of anaesthetist. We have shown low compliance with the recommendation to have the i.v. line visible and high but imperfect compliance with the recommendation to use BIS when TIVA and NMB drugs are used together. We do not know of any comparative data for visibility of i.v. access sites. Our rate of BIS use during TIVA is higher than that reported in NAP6 5 with NMB drug use (98% vs. 40%) and similar without NMB drugs (34% vs. 32%). In NAP6 6, TIVA was reported to be used in 9% of all general anaesthetics, a rise from below 6% in NAP5 7. It is likely that use is increasing further. In our hospital TIVA is used for 53% of all general anaesthetics and BIS monitoring is available in all theatres. For many surgical procedures, for example, laparoscopy, the patient's arms are routinely wrapped by their sides, therefore, the cannula is not visible and is often inaccessible. There is a balance to strike between visibility of the i.v. access site and the risk of other complications from repositioning the arm, such as impeding surgical access and risking compression neuropraxias. We are aware that some will place the hand in a sterile plastic bag to maintain visibility (Dr D. Mulvaney, Personal communication) but this is not routine in our hospital and we are not aware how widespread this practice is. After reflecting on our results, it is likely that our use of BIS monitoring will increase, whether or not NMB drugs are used. If almost half of venous access sites in other hospitals are also not visible it is likely that the use of processed EEG monitoring should increase generally in order to comply with the guidelines and to reduce the risk of AAGA.