CHAPTER 5 - ANESTHESIA
The aim of anesthesia is to prevent pain during a medical
procedure. But what is pain? One woman does not move a muscle during
the procedure and walks away without discomfort . But later she may
complain bitterly about the pain she suffered. Another woman keeps
yelling during the procedure but she says later that she felt almost
nothing. Most patients are somewhere in between, expressing more or
less pain. There is no direct relationship between the ease of the
procedure and the reported pain. A difficult procedure requiring much
force in dilation may be painless while a very smooth procedure may
cause much pain. In the latter case the doctor may get irritated and
rebuke the patient for exaggerating, which only makes the matter
worse. The most important way to prevent pain is a careful counseling
before the procedure and careful attention during the procedure.
In some cases the procedure may be done under local anesthesia
only, especially if the pregnancy is about 8 to 12 weeks. In a
younger pregnancy the dilation may cause more pain, in a more
advanced pregnancy the duration of the procedure may be exhausting.
In the advanced pregnancy a local anesthetic with nor- adrenaline as
a vasoconstrictor is recommended. (do not use adrenaline as this
causes tachycardia that may cause panic) In a number of cases a
so-called augmented local anesthesia is advisable, this is local
anesthesia combined with a suitable pre medication .
Since the beginning of this century general anesthesia is desired. Since only a very
light general anesthesia is feasible which has no analgesic
properties the combination with local anesthesia or a painkiller, like members of the fentanyl family, is recommended,
particularly in the case of an advanced pregnancy for the added
advantage of vasoconstriction.
A procedure developed in the Netherlands in 2006 is
the IV administered combination of midazolam (Versed®) 1 to 3 mg and alfentanil 1
mg ; this combination ('Rapidorm') gives a ± 3 minutes black out
with amnesia and "absolute" absence of pain.
1. PREMEDICATION - It is advisable to give atropine 0.5 mg in all
cases. It prevents or reduces vagal stimulation by handling the
uterus (especially during dilation), like bradycardia, vomiting, fall
of blood pressure and sweating. In general anesthesia it prevents or
reduces salivation and mucus formation in the respiratory tract. Not
everybody is convinced of the necessity in local anesthesia. At least
a syringe containing atropine should be kept ready for I.V.
administration in case of bradycardia. In an experiment where the ECG
was taken in a series of patients with and without atropine Schlebaum
found that the incidence of ECG changes, mainly bradycardia and
reduction of PR time, was significantly more frequent if no atropine
was given. Intramuscular administration of atropine has little or no
effect since the compound is rapidly disintegrated within the muscle
tissue.
In some patients local anesthesia is not sufficient to prevent
pain, or the patient is scared or restless. In these cases a suitable
pre medication can be given (augmented local). In the case of general
anesthesia a suitable sedative should be given, and an analgesic if
the general anesthesia is not combined with local. Fentanyl is a safe
and effective analgesic. It may cause pain along the vein in which it
is injected. Injection besides the vein is very painful. A possible
side effect is respiratory depression. Although we have never seen
this, naloxone should be kept ready as an antidote. More effective
but with a shorter duration is alfentanil (rapifen ®). The last
novelty is remifentanyl (Ultiva®) which is even stronger and
shorter acting than alfentanil.
Sedation can be obtained by giving diazepam or midazolam 2 -5 mg IV.
Diazepam has the disadvantage that certain products of metabolism
produce undesirable effects several hours after the procedure.
Midazolam lacks this disadvantage and has the advantage that it has a
marked anterograde amnesia. This pre medication also prevents muscle
movements caused by etomidate. Droperidol has a strong anti emetic
action, and a anxiolytic effect as well. It may be given together
with one of the other sedatives. Flumazenil may be used to reverse
the sedative effects of benzodiazepines (diazepam and midazolam) if
the patients sleeps too long. An ampoule should be kept ready for use
if the effect of the pre medication is too strong. A dose of 0.2 mg
(2 ml) is given slowly IV during 15 seconds. This may be repeated
till the desired effect is reached. The maximum dose is 2 mg (20 ml).
In the advanced pregnancy (over 13 weeks) ergometrine and
oxytocin are given to obtain a firm uterine wall. It is recommended
to bring a venous canula into a suitable vein in all cases. Best is a
type of canula with an injection valve, a side opening for a syringe,
allowing injection without the risk of contaminating the syringe with
blood. A suitable type is Venflon®. This allows repeated use of
syringes and an intravenous injection can be given without delay if
the need arises.
Anno 2010 we cannot finish this chapter without mentioning the use of propofol (Diprivan ®) as an anaestetic. The dosage is 6-12 mg/kg/hour. It has certain advantages over etomidate as patients are less drowsy postoperatively. TCI (target controlled infusion) icm Remifentanyl gives excellent results.
last revision spring 2010