51st Annual Regional Anesthesiology and Acute Pain Medicine Meeting

Rescue Saline Washout for Popliteal Sciatic Peripheral Nerve Block

BACKGROUND

Peripheral nerve blocks are a common and highly effective method ofmitigating perioperative pain, but could be associated with less desirableeffects like motor blockades
Previous literature described successful alleviation of respiratory distressfrom phrenic nerve palsy secondary to interscalene blocks using rescuesaline washouts [1]
Mechanism of saline washouts is not completely elucidated, it potentiallyreverses the effects of local anesthetic blockade by diluting it, or perhapschanging the pH and the sodium concentration [2]
This case report showcases a successful rescue saline washout for apopliteal sciatic block with regain of motor and sensory function for a patientthat required expedited return to ambulation.

Case Presentation

A 73 year old, 62.4 kg, female with PMH of insulin dependent type 1diabetes, contracture of right achilles tendon, presented for an elective rightankle arthrodesis with allograft and achilles tendon lengthening
Single shot adductor canal (10 mL of Ropivacaine 0.5%) and sciaticpopliteal fossa block (20 mL of Ropivacaine 0.5%) performed
Case unexpectedly cancelled, but patient needed to be discharged sameday
Rescue saline washout performed with 25 mL of 0.9% normal saline toapproximate a similar volume as the initial block without causing discomfort(Fig 1 & Fig 2)
Within the first 30 minutes of the rescue saline washout, the patientreported regaining some sensation
1 hour after the washout she did note some dorsiflexion and plantarflexion at 1+/4 strength (Table 1)
3 hours after the rescue washout, the physical therapists noted that thepatient had “light and deep touch to the lower extremity,” was able toperform the “sit and stand” maneuvers with a four wheel walker, and wasalso able to ambulate 200 feet with the walker (Table 1)
Overall, the patient regained modest sensory and motor function faster thanexpected at 3.5 hours and 4 hours after the initial block respectively

Discussion

Current literature peripheral nerve blockade rescue washouts come fromcase reports attempting to reverse phrenic nerve palsy
The mechanism of saline washouts in discontinuing the effects of a localanesthetic block is not fully understood
Proposed mechanism of rescue saline washout is dilution of localanesthetic, pH change, or sodium concentration effects [2]
Expected sensory blockade with ropivacaine 0.5% in popliteal sciaticblockade is 20.7 + 6.2 hours [3]. Expected motor blockade is 10.5 + 3.8hours [4].
The patient regained modest sensory and motor function faster thanexpected at 3.5 hours and 4 hours after the initial block respectively (Table1).
Of note, the patient reported having sensation return first prior tomeaningful motor restoration. This pattern is atypical, but at this time thepossible mechanism of this is unelucidated by the authors.
The clinical scenario described in this case report is significant because it isamong the first in current literature that utilizes a rescue saline washout fora lower extremity block

Conclusions

In circumstances of a block that is “no longer needed” due to unforeseencircumstances, a rescue saline washout for a popliteal sciatic nerve blockcan potentially provide modest return of sensory and motor function
Further studies should take place before identifying rescue washouts asstandard of care

References

Smith LM, Barrington MJ: A novel approach to reversal of respiratory distress following insertion of an interscalene nerve catheter. J Clin Anesth. 2018;47:43–4.10.1016/j.jclinane.2018.03.009.
Meulemans RJ, Gerritse BM: Acute reversal of respiratory distress after a preoperative single-shot interscalene nerve block. Regional anesthesia and pain medicine. 2025,rapm-2024-105728.10.1136/rapm-2024-105728.
Fernández-Guisasola J, Andueza A, Burgos E, et al.: A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa. Acta AnaesthesiolScand. 2001;45(8):967-970. 10.1034/j.1399-6576.2001.450808.x
Casati A, Fanelli G, Borghi B, Torri G: Ropivacaine or 2% mepivacaine for lower limb peripheral nerve blocks. Study Grou

Rescue Saline Lavage for Popliteal Sciatic Block