Between 2011 and 2021, after written informed consent, participants underwent LP by anaesthetists for one of two institutionally approved research studies on Alzheimer’s disease:
All relevant information pertaining to the LP was recorded on a specific case report form at the time of the LP.
Lumbar puncture
A medical history, coagulation studies and full blood count were performed prior to the procedure. All anticoagulants were stopped. Drugs that may interfere with coagulation, including aspirin and anti-inflammatory drugs were ceased.
Participants fasted and LP was undertaken in the clean environment of an anaesthetic room with blood pressure and pulse oximetry monitoring. The LP was performed with a strictly aseptic technique. All personnel wore surgical scrubs as is routine for spinal anaesthesia to prevent the rare complication of CSF infection.7
Participants were seated upright, the back prepared with antiseptic and draped. A sterile regional pack was used. Lidocaine 1% was injected subcutaneously prior to the LP. For the first five DIAN LP, a 24 gauge Sprotte needle was used. Subsequently, the LP was undertaken with a Temena (Polymedic, Carrieres-sur-Sine, France) microtip spinal needle (22/27 gauge×103 mm) with introducer (20 gauge×38 mm). The microtip 22/27 gauge needle has an atraumatic 27 gauge point and a 22 gauge shaft. The small calibre atraumatic point minimises CSF leak, while the larger gauge shaft maximises CSF flow for extraction.8
Specifically, this spinal needle is 103 mm in length with the proximal 88 mm having a 22 gauge external diameter (external diameter 0.68 mm, internal diameter 0.54 mm) and the distal 14 mm having a 27 gauge external diameter (external diameter 0.40 mm, internal diameter 0.19 mm) with a pencil point tip. Using a pulsatile CSF model, flow characteristics of this spinal needle are similar to a 22 gauge spinal needle. From Poiseuille’s law, flow rates are proportional to the fourth power of needle radius and inversely proportional to only the first power of needle length. Thus, the 14 mm length at 27 gauge would be expected to reduce flow rates, but this effect would be dwarfed by the increased shaft radius of the remaining 88 mm at 22 gauge.8
If there was difficulty using this fine needle, we used a pencil point 25 gauge spinal needle and 19 gauge introducer.
Puncture was in the second or third lumbar interspace, using surface markings. CSF (1–2 mL) was aspirated for microbiological and biochemical assessment, then 8–25 mL of CSF was collected by gravity flow (DIAN) or aspiration (AIBL) using a polypropylene syringe. Participants were then elevated at 45°, and admitted to the day case recovery lounge for observation of vital signs, oral intake and discharge (accompanied) at a minimum of 30 min postprocedure. Participants were followed up with a structured interview.