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ANALGESIA WITHOUT SEDATIVES DURING COLONOSCOPIES: WORTH CONSIDERING?
5
associated with chronic exposure to N
2
O, whereby the exact level to induce patient
harm cannot be predicted. Only long-term exposure to N
2
O in sufficient concentrations
seems to produce irreversible, toxic changes and has been associated with reproductive,
haematologic, immunological, neurological, liver and kidney disorders. Hence,
administration to patients for a short-term colonoscopy procedure seems to be safe.
Attention should be paid for personnel working in environments in which N
2
O is used the
whole day, especially without an adequate extraction system.
The safety level for N
2
O exposure is yet not clearly defined. The National Institute for
Occupational Safety and Health recommended “an exposure limit for N
2
O of 25 parts per
million (ppm) as a time-weighted average for a normal 8-hour workday and a 40-hour
workweek”.
48
The American Conference of Governmental Industrial Hygienists has assigned
for N
2
O an exposure limit of 50 ppm. In Germany, the occupational exposure limit is 100
ppm.
49
Lacking exact data, it is important to minimise exposure.
Every N
2
O apparatus must have a scavenging system
50
with sufficient extraction and
routinely checked for leaks. A minimum air exchange of 2-3 per hour must be guaranteed,
when N
2
O is used. Patients should wear an on demand valve mask perfectly fitting their
faces and be suggested not to speak during colonoscopy. After finishing the procedure and
stopping N
2
O, patients should receive 100% oxygen for 3-5 minutes via the mask.
CONCLUSION
The discussion on the ideal analgesic agent for colonoscopy demonstrates that in fact
none of the latter agents is ideal. Almost all have side effects, have less patient satisfaction
scores, have been used with sedatives, or have been studied in very small trials. But if pain is
relieved adequately during colonoscopy, sedation is indeed not required in a huge number
of patients. The use of N
2
O instead of IV drugs is “no laughing matter”,
51
for several reasons:
N
2
O with a loading dose and continuous administration provides adequate analgesia with
a patient being awake and co-operative; after cessation patient is awake, ready to get the
information necessary, and to leave the hospital soon after the procedure. Patients without
escort and living alone may in particular benefit from the fast recovery of psychomotoric
functions provided by N
2
O. However, there are some limitations of N
2
O like uncertainty
about chronic side effects and need for air conditioning and efficient ventilation together
with efficient active scavenging systems.
Alfentanil is a strong analgesic, facilitating a fast turnover of satisfied, pain free patients,
which are able to cooperate with the endoscopist. Its respiratory depressant effects are
without clinical impact. Moreover, all actions of alfentanil can be immediately reversed by
naloxone, making the substance safe in general use.
Further studies are needed to assess efficiency and last but not least patients and physicians
satisfaction level with use of these two forms of analgesia.