Identification of epidural space using air with normal saline
Bibliographic record
Abstract
Identification of the epidural space has been achieved by a number of techniques, of which loss of resistance to air or saline is the most commonly used. Some anaesthetists prefer air while others advocate using normal saline [1]. Whereas no serious adverse effects have been associated with the use of saline, there are a number of case reports describing complications associated with the use of air for identification of the epidural space [2]. The list of complications includes venous air embolism, pneumocephalus and patchy distribution of epidural block [2]. Despite this, a large number of anaesthetists including ourselves have been continuing to use air for identifying the epidural space. A recent survey showed that more than 30% of obstetric anaesthetists in Britain preferred air to normal saline [3]. The superior quality of the ‘feel’ that one gets throughout the insertion of the Tuohy needle is the reason why we prefer using air. Recently, we devised a new approach using both air and normal saline together. We use a combination of three-way taps connected together between the Tuohy needle and the loss of resistance syringe ( Fig. 9). The side ports of these three-way taps are connected using a short length of extension tubing forming a vertical loop. The three-way taps are then turned so that they communicate with each other through the extension tubing connected to their side ports. Arrangement of three-way taps and tubing attached to Tuohy needle and loss of resistance syringe. Note that for the purpose of illustration an opaque liquid has been used in place of saline. Normal saline is drawn up through the Tuohy needle connected to this assembly. Thus, the dead space of the needle and the descending limb of the loop formed by the extension tubing contain normal saline. The syringe and the ascending limb, on the other hand, contain only air. The three-way taps are locked, the tip of the Tuohy needle inserted into the lumbar intervertebral space selected and at a depth of 2 cm the three-way taps are unlocked. The needle is advanced feeling the resistance to the column of air in the syringe and the ascending limb of the loop. On entering the epidural space, however, it is the normal saline from the descending limb of the loop that is injected first and not the air. Using this technique, we experience the same quality of resistance that is usually felt using air. An extension tubing with two male ends can be used to connect the three-way taps. We constructed our own as shown in the figure. The dead space of the descending limb should be 2–4 ml as this is the volume that tends to get injected at loss of resistance. The whole assembly must be tested for leaks before beginning the procedure.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".