Pages From Acute Tocolysis Using Glyceryltrinitrate GTN WSYD PROC201847 (003) - 4

This document is valid on the day of printing only: 23 Apr 2021
Intrapartum: Acute Intravenous or Sub lingual / Lingual Spray Glyceryl Trinitrate (GTN) for Fetal Entrapment,
Retained Placenta or Uterine Inversion in Operating Theatre (OT) and Birth Unit (BU) – WSLHD
4. Precautions, Side Effects, Monitoring of GTN
GTN Contraindications
Because GTN can cause marked vasodilation, especially venodilation, it results in
peripheral pooling of blood and reduced venous return to the heart.
Extreme caution must therefore be used in the following situations:

 Sensitivity to glyceryl trinitrate or any of its components
 Obstructive or restrictive cardiac dysfunction or cardiac failure
 Uncorrected hypovolaemia or hypotension
 Severe anaemia or arterial hypoxaemia
 Primary pulmonary hypertension
 Increased intracranial pressure
(MIMS GTN 2019a and 2019b; AHFS 2019)
Patients should remain supine for 15 minutes after acute GTN use, whether IV or SPRAY
GTN, to minimise postural hypotension side-effects.
GTN Side Effects
GTN side-effects with both IV and SPRAY GTN are:
 Hypotension: All women will have some decrease in BP.

o Most have a modest decrease in BP and no symptoms, but some can have a large
fall and become symptomatic.
o In one study where 23 women were given Sublingual / Lingual SPRAY GTN 800
microgram during CS, the mean systolic blood pressure (SBP) decrease was
18%, with the largest fall being 46% (Craig 1998).
o In another study, a significantly larger decrease in SBP was seen with
Sublingual SPRAY 400 microgram compared to IV 100 microgram in cardiac
patients (Curry 1993).
 Headache: Up to 50%, but often much lower. Dose related.
 Tachycardia, less commonly bradycardia.
 Nausea/vomiting, allergic skin reaction, flushing (all rare).
 No uterine atony or postpartum haemorrhage due to short duration of action (Craig 1998)
unlike terbutaline (Eisler 1999).
 No adverse neonatal effects (David 1998; David 2000 - see Education Notes).
(MIMS Online 2019; AHFS 2019; various studies as above)
Western Sydney Local Health District Page 15 of 25

NB: This document will not necessarily apply in all circumstances. It does not replace professional and/or clinical judgement.
It may be amended/withdrawn at any time. Printed copies should not be relied upon. ALWAYS refer to the electronic copy.
WSYD-PROC201847.pdf • Release 1
This document is valid on the day of printing only: 23 Apr 2021
Intrapartum: Acute Intravenous or Sub lingual / Lingual Spray Glyceryl Trinitrate (GTN) for Fetal Entrapment,
Retained Placenta or Uterine Inversion in Operating Theatre (OT) and Birth Unit (BU) – WSLHD
Anaesthetic Support and Monitoring for GTN Administration
An anaesthetist should always be present to manage hypotension if IV GTN is being given

(only used in OT), and should ideally* also always be present if Sublingual / Lingual SPRAY
is being given.
The anaesthetist should:

 Exclude contraindications before administering GTN.
 Ensure IV access and volume support.
 Monitor blood pressure and respiratory rate, together with electrocardiogram (ECG) if
available (ECG may not be available in BU).
 Manage significant hypotension by:
o Keeping the woman recumbent and comfortably warm.
o Providing volume support.
o Considering an IV alpha-adrenergic agonist when necessary (MIMS Online 2019).
o NOTE: Because of short half-life, GTN effects usually wear off quickly and other
measures are not generally needed.
*On rare occasions, an obstetrician may have no choice but to administer or direct the
administration of SPRAY GTN for a critical event in birth unit (such as fetal head
entrapment) while awaiting the arrival of the anaesthetist. IV access must be instituted
before the administration of SPRAY GTN.
Western Sydney Local Health District Page 16 of 25

NB: This document will not necessarily apply in all circumstances. It does not replace professional and/or clinical judgement.
It may be amended/withdrawn at any time. Printed copies should not be relied upon. ALWAYS refer to the electronic copy.
WSYD-PROC201847.pdf • Release 1

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4. Precautions, Side Effects, Monitoring of GTN

Extreme caution must therefore be used in the following situations:

GTN Side Effects

GTN side-effects with both IV and SPRAY GTN are:

 Hypotension: All women will have some decrease in BP.

(MIMS Online 2019; AHFS 2019; various studies as above)

Western Sydney Local Health District Page 15 of 25

Anaesthetic Support and Monitoring for GTN Administration

An anaesthetist should always be present to manage hypotension if IV GTN is being given

The anaesthetist should:

Western Sydney Local Health District Page 16 of 25

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