The noxious mechanism of pain after intravenous injections.
Propofol is an iv general anaesthetic also used as sedative, that
besides hypotension and respiratory depression, frequently induces pain
after intravenous injection. Jalota et al(1). comparing several measures
to mitigate pain, interestling found that using the antecubital vein
instead of the hand vein was the most effective single intervention to
reduce pain. Other drugs (iv anaesthetics, diazepam, antibiotics,
anticancer drugs) may also induce pain after intravenous injection.
It seems worthy to look at the noxious mechanism of this pain.
Nociceptive pain is an alarm signal meaning an underlying lesion, which in
the case of an intravenous injection may correspond to a chemical or
osmotic aggression of the endothelium, especially when the venous flow is
small to dilute drugs. The lesion of the endothelium, which has
antithrombotic properties, sometimes results in the thrombosis of the vein
used for injection. Some caustic drugs must be administered in central
veins (with greater blood flow). I have seen many cases of phlebitis after
administration of diazepam trough catheters placed on hand's veins (low
blood flow).
The administration of drugs in the flow of a polyelectrolytic solution, is
another simple way to dilute drugs, remaining the solution more isosmotic
and likely less aggressive to vascular endothelium.
Besides the chemical/osmotic aggression provoked by drugs, it must also be
considered the lesion induced by the catheter itself.
Vascular endothelium is a very friable structure that in the lab is easily
removed from the vascular wall with a simple passage of cotton gauze. So,
is not surprising that the catheter may injure endothelium when its
diameter is similar to that of the vein, or when it is placed on mobile
zones (like the hand near the wrist) producing scrubbing movements inside
the vessel (2). The forearm length favours a much more stable catheter
than the short hand, and is less throbbing for patient activities like
eating or writing. It could be interesting to study a possible relation of
the catheter location with the phlebitis incidence.
Finally, it is also important to have in mind, that pain elicited by
catheter introduction is greater on hands, which are one of the most
sensitive areas (with a big cortical somatosensory projection), than on
the forearm.
These seem important reasons to prefer for intravenous injections an
antecubital catheter placement instead of their introduction on hands.
References.
1- Jalota L, Kalira V, George E, Shi Y-Y, Hornuss C, Radke O, et al.
Prevention of pain from propofol injection: systematic review and meta-
analysis. BMJ 2011;342:d1110.
Rapid Response:
The noxious mechanism of pain after intravenous injections.
Propofol is an iv general anaesthetic also used as sedative, that
besides hypotension and respiratory depression, frequently induces pain
after intravenous injection. Jalota et al(1). comparing several measures
to mitigate pain, interestling found that using the antecubital vein
instead of the hand vein was the most effective single intervention to
reduce pain. Other drugs (iv anaesthetics, diazepam, antibiotics,
anticancer drugs) may also induce pain after intravenous injection.
It seems worthy to look at the noxious mechanism of this pain.
Nociceptive pain is an alarm signal meaning an underlying lesion, which in
the case of an intravenous injection may correspond to a chemical or
osmotic aggression of the endothelium, especially when the venous flow is
small to dilute drugs. The lesion of the endothelium, which has
antithrombotic properties, sometimes results in the thrombosis of the vein
used for injection. Some caustic drugs must be administered in central
veins (with greater blood flow). I have seen many cases of phlebitis after
administration of diazepam trough catheters placed on hand's veins (low
blood flow).
The administration of drugs in the flow of a polyelectrolytic solution, is
another simple way to dilute drugs, remaining the solution more isosmotic
and likely less aggressive to vascular endothelium.
Besides the chemical/osmotic aggression provoked by drugs, it must also be
considered the lesion induced by the catheter itself.
Vascular endothelium is a very friable structure that in the lab is easily
removed from the vascular wall with a simple passage of cotton gauze. So,
is not surprising that the catheter may injure endothelium when its
diameter is similar to that of the vein, or when it is placed on mobile
zones (like the hand near the wrist) producing scrubbing movements inside
the vessel (2). The forearm length favours a much more stable catheter
than the short hand, and is less throbbing for patient activities like
eating or writing. It could be interesting to study a possible relation of
the catheter location with the phlebitis incidence.
Finally, it is also important to have in mind, that pain elicited by
catheter introduction is greater on hands, which are one of the most
sensitive areas (with a big cortical somatosensory projection), than on
the forearm.
These seem important reasons to prefer for intravenous injections an
antecubital catheter placement instead of their introduction on hands.
References.
1- Jalota L, Kalira V, George E, Shi Y-Y, Hornuss C, Radke O, et al.
Prevention of pain from propofol injection: systematic review and meta-
analysis. BMJ 2011;342:d1110.
2- Catheter associated thrombophlebitis and endothelium. Fernando
Martins do Vale. Rapid Responses for Webster et al.:
http://www.bmj.com/cgi/eletters/337/jul08_1/a339
Fernando Martins do Vale, MD, PhD.
Competing interests: No competing interests