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Syringe dead space: difference between revisions

Diff·revision 9 → 10·08:02, 4 Nov 2025

Difference between revision 9 and revision 10 of Syringe dead space. 16 lines changed; the page grew by 1,422 bytes.

Revision 9 — 02:17, 26 Oct 2025
ColdChainCleo (talk)
fix indentation in the source
9,004 bytes +393		Revision 10 — 08:02, 4 Nov 2025
Chromatokid (talk)
clarify that the figure is per dose, not per vial
10,426 bytes +1,422
1{{Infobox concept1{{Infobox concept
2| name = Syringe dead space2| name = Syringe dead space
+3| subtitle = Residual volume
3| image = syringe.svg4| image = syringe.svg
4| caption = Dead space lies distal to the plunger tip at full depression: the hub cavity, the needle lumen and any recess in the plunger face.5| caption = Dead space lies distal to the plunger tip at full depression: the hub cavity, the needle lumen and any recess in the plunger face.
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12| 3 mL syringe, Luer lock plus 21G needle = ≈0.080–0.100 mL13| 3 mL syringe, Luer lock plus 21G needle = ≈0.080–0.100 mL
13| Low-dead-space needle on a Luer hub = ≈0.010 mL14| Low-dead-space needle on a Luer hub = ≈0.010 mL
+15<!-- Applicable standards -->
+16| Hypodermic syringes = ISO 7886-1
+17| Insulin syringes = ISO 8537
+18| Hypodermic needles = ISO 7864
+19| Needle tubing dimensions = ISO 9626
+20| Delivered-volume tolerance at nominal capacity = ±5% (ISO 7886-1)
14}}21}}
15{{hatnote|For the devices in which dead space is measured, see [[Insulin syringe]]. For the volume arithmetic of a reconstituted vial, see [[Reconstitution calculator]].}}22{{hatnote|For the devices in which dead space is measured, see [[Insulin syringe]]. For the volume arithmetic of a reconstituted vial, see [[Reconstitution calculator]].}}
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70=== Effect of needle length ===77=== Effect of needle length ===
71Doubling cannula length from 12.7 mm to 25.4 mm doubles the lumen volume, taking a 25G needle from 0.67 to 1.34 µL. Against a hub of 60–70 µL this is immaterial. Needle length is selected on anatomical grounds — 4, 6 and 8 mm pen needles and 12.7 mm syringe needles are the common lengths for [[Subcutaneous injection|subcutaneous administration]] — and not on dead-space grounds.{{r|iso7864}}78Doubling cannula length from 12.7 mm to 25.4 mm doubles the lumen volume, taking a 25G needle from 0.67 to 1.34 µL. Against a hub of 60–70 µL this is immaterial. Needle length is selected on anatomical grounds — 4, 6 and 8 mm pen needles and 12.7 mm syringe needles are the common lengths for [[Subcutaneous injection|subcutaneous administration]] — and not on dead-space grounds.{{r|iso7864}}
+79
+80== Consequences for delivered dose and for vial yield ==
+81The two consequences are separable and are treated separately here because the distinction is the most common error in secondary discussion of the topic.
+82
+83'''Wastage.''' When a syringe is filled by drawing liquid through the needle, the hub and lumen fill first and remain full. Setting the plunger tip to a graduation then places the nominal volume in the barrel ''in addition'' to the dead-space volume already drawn. Full depression delivers the barrel volume — the dose is correct — and discards the dead-space volume with the device. The loss is to vial yield, not to the dose.
+84
+85'''Dose error.''' If an air pocket equal to the dead space sits in the hub when the graduation is read, the barrel contains that much less liquid than the graduation indicates. Expelling the air before injection then leaves a shortfall equal to the air volume. The proportional error is the dead-space volume divided by the intended dose.
+86
+87A worked case. A vial containing 5.0 mg of peptide is reconstituted with 2.00 mL of diluent, giving 2.50 mg·mL⁻¹. An intended dose of 0.50 mg corresponds to 0.20 mL.
7288
73== References ==89== References ==