References

1. Practice guidelines for moderate procedural sedation and analgesia 2018: a report by the American Society of Anesthesiologists task force on moderate procedural sedation and analgesia, the American Association of Oral and Maxillofacial Surgeons, American College of Radiology, American Dental Association, American Society of Dentist Anesthesiologists, and Society of Interventional Radiology. Anesthesiology 2018;128(3):437-79. https://doi.org/10.1097/ALN.0000000000002043
2. Song J, Kim WM, Lee SH, et al. Dexmedetomidine for sedation of patients undergoing elective surgery under regional anesthesia. Korean J Anesthesiol 2013;65(3):203-8. https://doi.org/10.4097/kjae.2013.65.3.203
3. Kim S, Hahn S, Jang MJ, et al. Evaluation of the safety of using propofol for pediatric procedural sedation: a systematic review and meta-analysis. Sci Rep 2019;9(1):12245. https://doi.org/10.1038/s41598-019-48724-x
4. Yang CH, Chen PJ, Mori M, et al. Cross-cultural comparison of continuous deep sedation for advanced cancer patients in East Asian countries: prospective cohort study. Jpn J Clin Oncol 2023;53(8):714-21. https://doi.org/10.1093/jjco/hyad037
5. Kumar A, Ramesh A, Kumar AJ, et al. Perioperative anxiety in regional anesthesia: implications, evaluation, and management. Journal of Indian College of Anaesthesiologists 2024;3(2):56-9. |https://doi.org/10.4103/jica.jica_25_24

Regional Anesthesia and Conscious Sedation: Optimising Safety, Comfort, and Clinical Outcomes

By Salah Uddin Al Azad, FCPS, DA, and Lutful Aziz, FCPS, PhD, FRCA

Introduction

The application of sedation during regional anaesthesia has evolved significantly to address not just procedural tolerance but patient-centered outcomes such as comfort, anxiolysis, and recall prevention. A growing body of evidence, particularly from elderly and high-risk cohorts, emphasizes the need for tailored sedation that preserves spontaneous ventilation and airway reflexes while offering cooperative sedation. Current trends also explore advanced delivery methods, such as target-controlled infusion (TCI) and the use of newer agents like dexmedetomidine and remimazolam.

Pre-sedation Planning and Risk Stratification

An effective sedation plan begins with a comprehensive pre-operative assessment, including systemic disease burden, cognitive status, and airway risk. American Society of Anesthesiologists (ASA) guidelines recommend standard fasting precautions, written informed consent with sedation discussion, and a structured sedation protocol that includes intra- and post-operative monitoring.

Special caution is warranted in elderly patients (age > 70) and those with ASA III/IV status, as their sensitivity to sedatives and risks of desaturation and hemodynamic instability are markedly increased. In geriatric patients or those with obstructive sleep apnea, COPD, or cardiac disease, sedatives that minimize respiratory depression and preserve hemodynamic stability are essential. Dexmedetomidine has been shown to reduce the incidence of postoperative delirium, facilitate cognitive recovery, and maintain spontaneous breathing with minimal fluctuation in vital signs.¹

Pediatric Patients

Regional anaesthesia is increasingly used in children, necessitating sedation strategies that ensure immobility and pain-free block placement. However, caution is advised in children with upper airway obstruction, epilepsy, or metabolic disorders. Dexmedetomidine has demonstrated favorable outcomes even in high-risk pediatric cases, particularly when used intranasally or in combination with ketamine.^2,3

Sedation Techniques and Drug Modalities

A variety of agents and methods have been applied with distinct pharmacokinetic and safety profiles. Incremental boluses of midazolam (0.5–2 mg) or fentanyl (25–50 mcg) are common but associated with unpredictable depth, variability in sedation scores, and unstable hemodynamics.

Continuous infusion or TCI offers superior control:

• Propofol at 25–75 μg/kg/min provides rapid titratable sedation but may cause hypotension, bradycardia, and apnoea.⁵
• Remifentanil TCI at 0.5–1.0 ng/mL is effective but should be used cautiously in opioid-naïve or high airway-risk patients.
• Dexmedetomidine, infused at 0.2–0.7 μg /kg/hr following a loading dose of 1 mcg/kg over 10–15 minutes, allows for cooperative sedation and prolongs sensory block when combined with local anaesthetics. Bradycardia and hypotension are dose-related but manageable.^6,7

Ketamine offers dissociative sedation with preserved airway reflexes and sympathetic stimulation. Its sub-anaesthetic doses (0.15–0.35 mg/kg bolus followed by 0.1–0.5 mg/kg/hr) support hemodynamic stability and analgesia without significant respiratory depression.⁸

Remimazolam, a novel ester-metabolized benzodiazepine, results in rapid onset anxiolysis, minimal accumulation, and cardiorespiratory stability—an advantage in elderly and ASA III/IV patients. It offers predictable sedation with reduced fentanyl requirements and faster recovery than midazolam or propofol.⁹

EEG-Based Understanding of Sedative Effects

EEG monitoring reveals distinct cortical patterns:

• Propofol induces frontal alpha and delta oscillations, associated with global cortical depression and unresponsiveness.
• Dexmedetomidine produces dominant theta waves and sleep spindles, closely resembling natural stage II non-rapid eye movement sleep with arousable but calm sedation.¹

This difference reflects not only the pharmacology (GABA-A potentiation vs α2 agonism) but also clinical utility—propofol being suited for deep sedation or brief procedures. At the same time, dexmedetomidine supports prolonged, cooperative sedation with minimal respiratory risk.

Advanced Delivery Systems and Emerging Models

Recent efforts have refined sedation delivery via TCI using pharmacokinetic models. Effect-site targeting (Ce) has been shown to be clinically superior to plasma targeting (Cp) for sedation due to its ability to achieve more consistent sedation depth and minimize overshoot [10]. In effect, site-targeting models involve drug equilibration between plasma and the brain (effect site) using a rate constant (kₑ₀). This ensures the infusion rate is adjusted to achieve and maintain the desired biophase concentration rapidly.¹¹ For example:

• Dexmedetomidine: Colin’s effect-site model suggests a mean Ce of ~0.99 ng/mL for deep sedation based on processed EEG analysis[6]; Hannivort's plasma-targeted model supports Cp 0.3–0.6 ng/mL with minimal hemodynamic compromise.⁷
• Remimazolam: Schüttler’s Ce model (0.6–1.0 µg/mL) offers reliable sedation with rapid recovery.⁹

Patient-Controlled Sedation (PCS)

PCS with propofol or midazolam offers patients autonomy and safety through lock-out mechanisms. Though not widely adopted, it shows promise in day-case regional procedures. Studies show that more than 50% of patients using PCS without supplemental oxygen experienced insufficient respiratory function, including oxygen desaturation (SpO₂ < 90%) or hypercarbia (PtcCO₂ > 6.5 kPa).¹²

Conclusion

Sedation during regional anaesthesia demands a nuanced approach tailored to individual patient profiles and surgical demands. Based on current evidence, dexmedetomidine and remimazolam offer the most favorable profiles in terms of safety, efficacy, and recovery, especially in vulnerable populations. As TCI models and monitoring evolve, anaesthesiologists are better equipped to deliver precise, safe, and patient-friendly sedation, improving perioperative outcomes.

References

1. Arslan G, Korkmaz Ş, Temizel F, et al. Comparison of propofol and dexmedetomidine spinal anaesthesia for intraoperative sedation. Reg Anesth Pain Med 2006;31:35.
2. Patel A, Davidson M, Tran MCJ, et al. Dexmedetomidine infusion for analgesia and prevention of emergence agitation in children with obstructive sleep apnea syndrome undergoing tonsillectomy and adenoidectomy. Anesth Analg 2010;111(4):1004-10. https://doi.org/10.1213/ANE.0b013e3181ee82fa
3. Bong CL, Tan J, Lim S, et al. Randomised controlled trial of dexmedetomidine sedation vs general anaesthesia for inguinal hernia surgery on perioperative outcomes in infants. Br J Anaesth 2019;122(5):662-70. https://doi.org/10.1016/j.bja.2018.12.027
4. Gabopoulou Z, Mavrommati P, Papaioannou L, et al. Conscious sedation with propofol during elective orthopaedic surgery under regional blockade. Reg Anesth Pain Med 2005;30(1):21.
5. Höhener D, Blumenthal S, Borgeat A. Sedation and regional anaesthesia in the adult patient. Br J Anaesth2008;100(1):8-16. https://doi.org/10.1093/bja/aem342
6. Kim KM, Seo KH, Lee JM, et al. Target-controlled infusion of dexmedetomidine effect-site concentration for sedation in patients undergoing spinal anaesthesia. J Clin Pharm Ther 2020;45(2):347–53. https://doi.org/10.1111/jcpt.13085
7. Delgado MA, de Lanna Rocha RT, dos Santos Mendonça A, et al. Sedation with dexmedetomidine target controlled infusion during dental surgery: a retrospective case report. J Oral Maxillofac Anesth 2023;2:32. https://doi.org/10.21037/joma-23-29
8. Schwenk ES, Viscusi ER, Buvanendran A, et al. Consensus guidelines on the use of intravenous ketamine infusions for acute pain management. Reg Anesth Pain Med 2018;43(5):456-66. https://doi.org/10.1097/AAP.0000000000000806
9. Schüttler J, Eisenried A, Lerch M, et al. Pharmacokinetics and pharmacodynamics of remimazolam after continuous infusion in healthy male volunteers: Part I. Pharmacokinetics and clinical pharmacodynamics. Anesthesiology2020;132(4):636-51. https://doi.org/10.1097/ALN.0000000000003103
10. Enlund M. TCI: Target controlled infusion, or totally confused infusion? Call for an optimised population based pharmacokinetic model for propofol. Ups J Med Sci 2008;113(2):161-70. https://doi.org/10.3109/2000-1967-222
11. Cuiabano IS, de Miranda GP, Módolo NSP, et al. Safety and efficacy of target-controlled infusion versus intermittent bolus administration of propofol for sedation in colonoscopy: a randomized controlled trial. Braz J Anesthesiol2023;73(6):751-7. https://doi.org/10.1016/j.bjane.2022.06.003
12. Nilsson A, Sjöberg F, Öster S, et al. Patient-controlled sedation and analgesia with propofol and alfentanil: a preliminary safety evaluation prior to use of non-anaesthesiology doctors. Open J Anesthesiol 2012;2(2):47-52. https://doi.org/10.4236/ojanes.2012.22012

Regional Anesthesia and Conscious Sedation: Our Practice

By Iskandar Khalid, MBBS, MMED, EDRA

Introduction

Procedural sedation during surgery under regional anaesthesia (RA) provides anxiolysis, enhanced patient comfort, and improved patient satisfaction.¹ Conscious (or moderate) sedation, defined by the American Society of Anesthesiologists as a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, leads to faster cognitive recovery and a lower risk of postoperative neurocognitive complications compared to deeper levels of sedation.^1,2

Conscious Sedation: Practices

In our practice, all patients undergoing surgery under RA will be offered conscious sedation.

After a thorough pre-sedation assessment, which includes reviewing for potential contraindications, airway evaluation, fasting status, and aspiration risk, as well as medical history and medication review, patients are counseled on the benefits and risks of procedural sedation, and informed consent is obtained.

Patients are put on supplemental oxygen and standard monitoring, including, electrocardiography, non-invasive blood pressure, pulse oximetry, and capnography as per the College of Anaesthesiology recommendations.³ Processed EEG monitors are not routinely used for conscious sedation in our practice. Still, we do recognize their utility as a more objective measure of depth of anaesthesia, especially in specific patient populations, such as the elderly.⁴ Procedural sedation is commenced after confirmation of the adequacy of RA for surgical anaesthesia and completion of the surgical safety checklist.

While a variety of intravenous (IV) sedatives may be used, our guiding principle is an individualized sedation plan, aiming to use the minimal effective dose for conscious sedation with careful titration and continuous monitoring. The primary pharmacological agent used in our practice is intravenous propofol due to its rapid titratability, favorable recovery profile, and antiemetic properties, either given as a manually-controlled infusion (MCI) or target-controlled infusion (TCI). Before the administration of propofol, patients would receive 0.5 to

1.0 mg/kg of IV lignocaine to alleviate propofol-induced pain on injection. Using an MCI technique, patients typically receive an initial bolus of 0.5 mg/kg (~30-40 mg in an average adult), followed by an initial infusion rate of 25 to 75 µg/kg/min, and intermittent boluses of 10 to 20 mg as needed with careful observation. If a TCI of propofol is used, a plasma or effect site concentration of 1 to 1.5 µg/ml is initially targeted followed by titration to the desired effect.

We also use IV midazolam as an alternative or adjunct for conscious sedation, especially when hypotension precludes standard doses of propofol. Our approach involves administering incremental boluses of 1 to 2 mg IV midazolam, followed by a 3-5 minute wait for the effect to take hold, until the desired level of sedation is achieved. IV dexmedetomidine infusion is another alternative to propofol, which we use in our practice. Randomized trials have shown that compared to propofol, use of dexmedetomidine for moderate sedation during regional anaesthesia may offer better sedative properties, greater overall patient satisfaction, and fewer negative effects on hemodynamics and respiration.^5,6 We typically start with a loading dose of 0.5 to 1 µg/kg over 10 to 15 minutes, followed by a maintenance infusion of 0.2 to 0.6 µg/kg/hour titrated to effect. Incidence of hypotension and bradycardia appears to be low within this dose range, but we do have a low threshold to use lower infusion rates or omit the loading dose completely in at-risk populations (eg, elderly, severe cardiac disease).

Special Considerations for Elderly Patients

Elderly and frail patients require particular caution when performing sedation during RA due to their altered pharmacokinetics and pharmacodynamics as well as decreased physiological reserve.⁷ In our practice, the key tenet for effective and safe conscious sedation in this population would be “start low and go slow.” We generally reduce initial doses by 30%-50% in patients over 70 years old and give smaller incremental boluses with longer pauses in between to observe for effect. We also have a lower threshold to prevent and treat sedative-induced hypotension in the elderly, including starting a low-dose intravenous vasopressor (eg, phenylephrine) infusion to maintain a mean arterial pressure close to the patient’s baseline. Additionally, we find that reassurance and effective communication are often an ample substitute for higher sedative drug doses in the elderly population.

Conclusion

Conscious sedation during surgery under RA is a valuable technique that, when applied thoughtfully, can enhance patient experience without compromising safety. Our overarching principle is to individualize the sedation plan; some patients may do best with just a touch of midazolam and reassurance, while others may need a steady infusion of propofol or dexmedetomidine. With a practical, patient-centered approach, conscious sedation can be delivered effectively, keeping patients comfortable yet protected throughout their surgical procedure under regional anaesthesia.

References

1. Barry G, Uppal V. Sedation during regional anesthesia: less is more. Can J Anaesth 2022;69(12):1453-8. https://doi.org/10.1007/s12630-022-02338-6
2. Practice guidelines for moderate procedural sedation and analgesia 2018: a report by the American Society of Anesthesiologists task force on moderate procedural sedation and analgesia, the American Association of Oral and Maxillofacial Surgeons, American College of Radiology, American Dental Association, American Society of Dentist Anesthesiologists, and Society of Interventional Radiology. Anesthesiology 2018;128(3):437-79. https://doi.org/10.1097/ALN.0000000000002043
3.  Recommendations for Patient Safety and Minimal Monitoring Standards during Anaesthesia and Recovery (5th Edition) 2022. College of Anaesthesiologists, Academy of Medicine of Malaysia and Malaysian Society of Anaesthesiologists. https://www.msa.net.my/view_file.cfm?fileid=230
4. Bocskai T, Kovács M, Szakács Z, et al. Is the bispectral index monitoring protective against postoperative cognitive decline? a systematic review with meta-analysis. PLoS One 2020;15(2): e0229018. https://doi.org/10.1371/journal.pone.0229018
5. Padhi N, Hota S, Ekka M, et al. Comparison of dexmedetomidine and propofol for sedation in patients undergoing upper limb orthopedic surgery under regional anesthesia with brachial plexus block. Journal of Surgical Specialties and Rural Practice 2024;5(1):14-9. https://doi.org/10.4103/jssrp.jssrp_35_23
6. Shah PJ, Dubey KP, Sahare KK, et al. Intravenous dexmedetomidine versus propofol for intraoperative moderate sedation during spinal anesthesia: a comparative study. J Anaesthesiol Clin Pharmacol 2016;32(2):245-9. https://doi.org/10.4103/0970-9185.168172
7. Irwin MG, Ip KY, Hui YM (2019). Anaesthetic considerations in nonagenarians and centenarians. Curr Opin Anaesthesiol 32(6):776-82. https://doi.org/10.109 7/ACO.0000000000000793