Ambulatory perineural catheter management – by promoting earlier home discharge – ensures the cost effectiveness of continuous peripheral nerve blockade.12 The technique also suits patients who prefer to recuperate in their own home rather than in hospital. 3 It has also been suggested that the earlier discharge enabled by ambulatory perineural catheters may theoretically reduce the perioperative nosocomial wound infection risk.
Depending on the surgery, individual patients' pain tolerances and the logistical setup of the hospital and ambulatory perineural catheter service, an ambulatory infusion/perineural catheter can reduce hospital stay by 0.5-2 nights – an average of a 1 night saving (approx. $600) is commonly quoted. 1, 2 A $600 saving typically exceeds the ambulatory pump cost and extra professional fees required for safe management.
Successful ambulatory infusion and ambulatory perineural catheter management requires commitment. Practice models where the technique has proven successful frequently involve (solo) private practice settings where through adequate case exposure, anesthesiologists can acquire the required expertise for successful and efficient catheter placement. Private practice anesthesiologists may also be in a better position to ensure delivery of the required patient education, and can easily provide the required supervision themselves to ensure safety. The ambulatory infusion technique is more challenging in large departments, as it requires logistics setup and the creation of new protocols/personnel for postoperative catheter supervision. A further challenge for large departments is the required anesthesiologist subspecialisation to allow anesthesiologists' placing catheters to gain the required expertise.
All our patients receive an information leaflet a few days before surgery, which introduces the expectation of a home catheter and ambulatory infusion. This is usually followed up by a phone call by the anesthesiologist the day before surgery. Patients receive a second leaflet on the day of surgery with detailed instructions on home catheter management (see Appendix at end of page). The anesthesiologist verbally reinforces these instructions before hospital discharge. Patients are given the mobile phone number of the anesthesiologist (and hospital) but generally no further follow up is arranged. Patients remove the catheter themselves without additional assistance. We have been administering this treatment since 2003 and have managed thousands of patients without major complication. The most common procedures are:
1. Continuous interscalene analgesia for shoulder surgery (most anesthesiologists place a catheter for rotator cuff repair, but some will place a catheter for all shoulder surgery). Home discharge day 0-1.
3. Continuous femoral block for TKJR and ACLR. Following TKJR, catheters are usually removed prior to day 3 discharge. However, if patients are motivated for home discharge on day 2, we allow catheter management at home. Occasionally, ongoing pain beyond day 2-3 will necessitate ambulatory catheter management beyond day 3. ACLR patients receiving an ambulatory femoral catheter are discharged on the day of surgery.
1. Motor block: This is not usually a problem for the upper extremity as the arm is typically supported with a sling. The only precaution is patients are warned to be careful with the arm while dense motor block is present. If early active physiotherapy is planned (e.g. arthroscopic capsular release or some elbow procedures), it may be necessary to turn the infusion off until significant pain occurs. For continuous distal thigh sciatic block, foot drop is not an issue because the foot is usually supported with a below knee cast. As the block is performed distal to the hamstrings, patients can flex the knee to keep the foot off the ground while mobilising with crutches (Fig. 2). Motor block secondary to continuous femoral block can be problematic and requires caregiver commitment. 4 See continuous femoral block for guidance.
3. Showering/bathing: patients are instructed to try to keep the dressing site relatively dry. Patients either shower by hand with a mobile shower nozzle or for shoulder surgery patients, bathing works well while stretching the tubing over the side of the tub.
Fig. 1. Ambulatory continuous interscalene analgesia illustrating the typical sling after shoulder surgery.
Fig. 2. Continuous sciatic block. Patients can still flex the hip and knee, thus keeping the foot off the ground.
Ambulatory pump choice
Best results are achieved with a low background infusion (e.g. 2-5 mL/hr) and patient controlled boluses (e.g. 5-10 mL every 30-60 min). A low background infusion maximises patient control, minimises motor block, and maximises pump duration for a given reservoir volume. When extra LA requirement is expected (e.g. rotator cuff repair), patients are instructed to administer boluses 4-6 hourly regardless of pain. For multi-orifice catheters, there is limited evidence that compared with continuous only infusions, intermittent bolus regimens provide a better block for a given LA dose. This is thought to be related to better LA spread from the higher flows/pressures during bolus flow. Central to this concept is a critical pump flow rate/pressure during boluses. However, all the currently available ambulatory pumps are limited by their relatively low bolus flow rates (< 150 ml/hr). Depending on the anticipated postoperative pain, the catheter location and requirement for early mobilisation, some infusions are left off unless pain becomes problematic (e.g. infraclavicular catheters in patients who are to receive early physiotherapy). A small subset of patients who require more than 72 hours of potent analgesia can be safely and effectively managed by having their elastomeric 7 or electronic pump refilled to provide extended nerve blockade.
Elastomeric and electronic pumps are widely available, but there are two particular standouts; both having been used in our practice with great success (Fig 3A/3B).
Electronic pumps have the advantage of programmability for a wide range of background infusions and bolus volumes, and many have alarms, which will alert both patients and caregivers to catheter obstruction. This may provide early warning regarding catheter obstruction and subsequent block failure. Electronic pump flow rates are said to be less subject to changes in ambient temperature, although the clinical relevance of this observation is uncertain. Although there is some evidence to suggest patients prefer the simplicity of elastomeric pumps, 6 advances have since been made to electronic designs. A notable example is the ambIT® pump (Fig. 3A), which has easy to use bolus and start/stop buttons. Nevertheless, patients need to be reminded to not confuse the function of each button and to not push either button accidentally.
Fig. 3A. ambIT® ambulatory pump: left, LA reservoir, infusion mechanism and right, carry bag.
Elastomeric pumps have the advantage of being simpler to operate, and not subject to inadvertent false alarms leading to possible phone calls to the ambulatory service. We have significant experience with the On-Q range of elastomeric pumps®, in particular the On-Q PainBuster® elastomeric device (2 ml/hr + hrly 5 ml boluses), which has a delivery regimen appropriate for virtually all perineural indications (Fig. 3B). For continuous lumbar plexus block, we prefer the higher flow rate delivered by the On-Q C-bloc elastomerc pump®, which delivers a 5 mL/hr background infusion and on-demand hourly 5 mL boluses. All the On-Q elastomeric devices enable the infusion to be stopped by squeezing the clamp around the elasotemic pump tubing.
Fig. 3B. PainBuster® elastomeric device which delivers a 2 mL/hr background infusion and 5 mL boluses up to every hour (bolus flow rate=150 mL/hr).
It goes without saying that all patients receiving regional blocks for postoperative analgesia still benefit from concomitant multimodal analgesia:
1. Paracetamol / acetaminophen
2. NSAID. We use diclofenac SR 75 mg 12 hrly PRN (ibuprofen if patients are intolerant of diclofenac, and celecoxib if patients are intolerant of COX2 non-selective NSAIDS)
3. Tramadol for pain uncontrolled by the regional block + drugs (1) + (2). We use the SR preparation because of the reduced side effects associated with this preparation outweighing the downside of a slower onset time.
See also perineural catheter technique
1. Ilfeld BM, Mariano ER, Williams BA, et al. Hospitalization costs of total knee arthroplasty with a continuous femoral nerve block provided only in the hospital versus on an ambulatory basis: a retrospective, case-control, cost-minimization analysis. Reg Anesth Pain Med 2007;32:46-54.
2. Fredrickson MJ, Stewart AW. Continuous interscalene analgesia for rotator cuff repair: a retrospective comparison of effectiveness and cost in 205 patients from a multi-provider private practice setting. Anaesth Intensive Care 2008;36:786-91.
3. Ilfeld BM, Esener DE, Morey TE, et al. Ambulatory perineural infusion: the patients' perspective. Reg Anesth Pain Med 2003;28:418-23.
4. Ilfeld BM, Duke KB, Donohue MC. The association between lower extremity continuous peripheral nerve blocks and patient falls after knee and hip arthroplasty. Anesth Analg 2010;111:1552-4.
5. Fredrickson MJ, Ball CM, Dalgleish AJ. Successful continuous interscalene analgesia for ambulatory shoulder surgery in a private practice setting. Reg Anesth Pain Med 2008;33:122-8.
6. Capdevila X, Macaire P, Aknin P, et al. Patient-controlled perineural analgesia after ambulatory orthopedic surgery: a comparison of electronic versus elastomeric pumps. Anesth Analg 2003;96:414-7
7. Grant CR, Fredrickson MJ. Regional anaesthesia elastomeric pump performance after a single use and subsequent refill: a laboratory study. Anaesthesia 2009;64:770-5.
Appendix: Ambulatory Pump Home Instructions