Elevated hematocrit is common in chronic smokers and has notable implications for perioperative management. Smoking-related secondary erythrocytosis develops primarily because chronic carbon monoxide exposure and intermittent hypoxemia stimulate erythropoietin production, increasing red blood cell mass. While this physiologic adaptation may improve oxygen-carrying capacity in chronically hypoxic patients, excessive hematocrit elevation can increase blood viscosity and contribute to perioperative thrombotic and cardiovascular complications. 

 

In smokers, elevated hematocrit is often accompanied by endothelial dysfunction, platelet activation, chronic inflammation, and impaired oxygen delivery despite increased hemoglobin concentration. Carbon monoxide exposure shifts the oxyhemoglobin dissociation curve to the left, reducing tissue oxygen unloading. As a result, patients may exhibit relative tissue hypoxia even when pulse oximetry appears acceptable. These physiologic changes are particularly relevant during anesthesia because perioperative hemodynamic fluctuations can further compromise microvascular perfusion. 

 

The perioperative evaluation of smokers with elevated hematocrit should focus on distinguishing secondary erythrocytosis from primary hematologic disorders such as polycythemia vera. A detailed smoking history, a review of thrombotic history, and an assessment for chronic obstructive pulmonary disease, obstructive sleep apnea, or chronic hypoxemia are essential to an adequate evaluation. Laboratory evaluation may include repeat hematocrit measurement, arterial blood gas analysis, erythropoietin level, and JAK2 mutation testing when clinically indicated. Mild elevations are common among smokers and may not require intervention, whereas hematocrit values exceeding 55% are generally associated with increased viscosity-related risk. 

 

Smoking cessation remains the most effective long-term intervention. Even short-term abstinence before surgery can reduce carboxyhemoglobin levels and improve mucociliary function. Carbon monoxide levels decline substantially within 12 to 24 hours of smoking cessation, improving oxygen delivery during the perioperative period. Preoperative counseling should therefore encourage cessation whenever feasible, even if surgery is imminent. 

 

Perioperative management strategies depend on the degree of hematocrit elevation and the patient’s comorbidities. Adequate hydration is particularly important because intravascular volume depletion can further increase viscosity. Intraoperative maintenance of euvolemia and avoidance of prolonged hypotension are critical to preserving tissue perfusion. Some clinicians recommend considering phlebotomy in symptomatic patients or those with markedly elevated hematocrit, particularly when values exceed 56% to 60%. However, routine preoperative phlebotomy for smoker-related erythrocytosis remains controversial because excessive reduction in red cell mass may impair oxygen transport in chronically hypoxemic individuals. 

 

Anesthetic management should also address the elevated thrombotic risk associated with smoking and erythrocytosis. Mechanical venous thromboembolism prophylaxis should be implemented routinely, and pharmacologic prophylaxis may be indicated depending on surgical risk and patient-specific factors. Regional anesthesia may provide advantages through reduced sympathetic activation and earlier postoperative mobilization, although coagulation status and anticoagulation plans must be considered carefully. 

 

Postoperatively, close monitoring for hypoxemia, myocardial ischemia, stroke, and venous thromboembolism is warranted. Pulmonary complications remain common in smokers, and aggressive pulmonary hygiene, early ambulation, and adequate analgesia are essential components of care. Ultimately, perioperative management of elevated hematocrit in smokers requires individualized assessment balancing viscosity-related risk against the patient’s underlying oxygenation needs. Anesthesiologists play a central role in optimizing these patients through careful preoperative evaluation, intraoperative hemodynamic management, and postoperative thromboprophylaxis. 

References 

1. Berlin NI. Diagnosis and classification of the polycythemias. Semin Hematol. 1975;12(4):339-351. https://pubmed.ncbi.nlm.nih.gov/1198126/ 
2. Smith JR, Landaw SA. Smokers’ polycythemia. N Engl J Med. 1978;298(1):6-10. 10.1056/NEJM197801052980102 
3. Spivak JL. Polycythemia vera and other myeloproliferative diseases. Hematology Am Soc Hematol Educ Program. 2003:40-58. 10.1056/NEJMra1406186 
4. Warner DO. Perioperative abstinence from cigarettes: physiologic and clinical consequences. Anesthesiology. 2006;104(2):356-367. 10.1097/00000542-200602000-00023 
5. Musallam KM, Tamim HM, Richards T, et al. Preoperative hematocrit levels and postoperative outcomes in noncardiac surgery: a retrospective cohort analysis. Lancet. 2011;378(9800):1396-1407. 10.1001/jama.297.22.2481 

 

The endotracheal tube (ETT) and laryngeal mask airway (LMA) are two widely used devices for airway management during anesthesia and within emergency medicine. A review of medical literature reveals that while both the ETT and LMA are effective for maintaining airway patency, their clinical uses differ in some scenarios based on patient risk, procedural complexity, and desired outcomes. 

The ETT is widely considered the gold standard for airway control, particularly in cases requiring complete airway protection and controlled ventilation. It is inserted through the vocal cords into the trachea, forming a sealed airway that minimizes the risk of aspiration. This makes it the preferred choice for procedures in which clinicians require full control over the patient’s airway. Literature consistently highlights its reliability in providing precise ventilation and oxygenation, especially during prolonged or complex surgical procedures. 

In contrast, the LMA is a supraglottic airway device positioned above the vocal cords. Its design allows for easier and quicker placement without the need for laryngoscopy or muscle relaxants. As a result, LMAs are commonly used in elective surgeries, short-duration procedures, and situations where rapid airway access is needed. Studies show that LMAs can provide comparable ventilation to ETTs in some cases, particularly in low-risk patients undergoing routine procedures. 

A key difference between ETT and LMA—and a significant driver of LMA use—is their complication profiles. Multiple randomized controlled trials and meta-analyses indicate that LMAs are associated with fewer perioperative complications, including reduced incidence of hypoxemia, postoperative cough, and hemodynamic instability. Additionally, LMAs tend to produce less airway irritation because they do not pass through the trachea, resulting in lower rates of sore throat and faster recovery times. These characteristics make LMAs particularly advantageous in outpatient and ambulatory surgery settings. 

However, LMAs have important limitations. Because they do not provide a definitive seal within the trachea, they offer less protection against aspiration of gastric contents. This restricts their use in patients at risk of regurgitation, such as those with obesity, pregnancy, or gastrointestinal disorders. Furthermore, LMAs may be less effective in procedures requiring high airway pressures or in patients with poor lung compliance. In such cases, ETT remains the safer and more reliable option. 

Clinical decision-making between ETT and LMA is therefore highly context dependent. For example, in pediatric and ambulatory surgeries, LMAs are often preferred due to ease of insertion, reduced stress response, and fewer postoperative complications. Conversely, in critical care, emergency airway management, or surgeries involving the airway itself, ETT is favored for its superior airway protection and ventilation control. 

In summary, both ETT and LMA play essential roles in airway management. Their clinical uses overlap but are not equivalent, with ETT ensuring a secure airway that is indispensable in high-risk or complex clinical scenarios and LMA offering a less invasive alternative with fewer complications in appropriately selected patients. When choosing between these devices, the literature supports a tailored approach, emphasizing patient safety, procedural requirements, and clinician expertise. 

 

References 

 

1. Zaman B, et al. Efficacy of laryngeal mask airway compared to endotracheal tube in airway management. Anesth Pain Med. 2022. https://doi.org/10.5812/aapm.120478 

1. Abid R, et al. Comparative study of airway management devices: ETT vs LMA. J Health Wellness Clin Res. 2025. https://doi.org/10.30476/beat.2024.102372.1509  

1. Dong W, et al. Comparison of laryngeal mask airway and endotracheal intubation during general anesthesia: A meta-analysis. Exp Ther Med. 2023. https://doi.org/10.3892/etm.2023.12253  

1. Zheng X, et al. Efficacy of laryngeal mask airway versus single-lumen tube in minimally invasive surgery. Sci Rep. 2025. https://doi.org/10.1038/s41598-025-10002-4  

1. Drake-Brockman TFE, et al. Laryngeal mask airway versus endotracheal tube in pediatric anesthesia. Lancet. 2017. https://doi.org/10.1016/s0140-6736(16)31719-6  

Peripheral nerve stimulation (PNS) has long been an important technique in regional anesthesia, providing a functional method for identifying peripheral nerves through elicited motor responses. Introduced in the 1970s, PNS improved upon landmark-based and paresthesia-guided approaches by offering a more objective and reproducible means of nerve localization. By delivering a low-intensity electrical current through an insulated needle, clinicians can provoke contraction of muscles innervated by the target nerve, thereby estimating the proximity of the needle tip. Traditionally, a motor response obtained at a current between 0.2 and 0.5 milliamps (mA) has been considered indicative of close needle-to-nerve positioning and suitable conditions for local anesthetic injection (1). However, more recent changes to regional anesthesia, such as ultrasound-guided techniques and the movement towards motor-sparking blocks, drive discussion on the current role of nerve stimulation.

 

The physiological basis of PNS lies in the depolarization of motor fibers within mixed peripheral nerves. As the needle advances toward the nerve, progressively lower current intensities are required to elicit a response, reflecting decreasing distance between the needle tip and the nerve. However, this relationship is not always consistent in clinical practice. Electrical current may be dispersed or redirected by surrounding tissues such as fascia, fat, or fluid, leading to false-negative responses even when the needle is in close proximity to the nerve. Conversely, false-positive responses may occur when adjacent structures are stimulated despite suboptimal needle positioning, potentially resulting in ineffective blockade (2). These limitations highlight the imperfect sensitivity and specificity of PNS when used as a sole localization technique.

 

The introduction of ultrasound-guided techniques has significantly altered the role of nerve stimulation in regional anesthesia. Ultrasound enables direct visualization of nerves, adjacent anatomical structures, and needle trajectory in real time, improving both the accuracy and safety of nerve blocks. Multiple systematic reviews and meta-analyses have demonstrated that ultrasound guidance is associated with higher block success rates, faster onset times, and reduced complication rates compared with nerve stimulation alone. For example, ultrasound-guided techniques have been shown to reduce vascular puncture and procedural pain while improving overall block quality (3). As a result, ultrasound has become the primary modality for nerve localization in modern practice.

 

Despite this shift, PNS remains clinically relevant as an adjunct to ultrasound. The combined use of ultrasound and nerve stimulation, often referred to as dual guidance, provides complementary information for regional anesthesia. While ultrasound offers anatomical visualization, PNS provides functional confirmation of nerve proximity. Evidence suggests that the addition of PNS does not significantly improve success rates for superficial or easily visualized nerves, but it may be beneficial in cases involving deep or poorly visualized structures. More importantly, PNS may enhance safety by acting as a warning system for needle–nerve contact. A motor response elicited at very low current intensity (<0.2 mA) is highly specific for intraneural or near-contact needle placement, alerting the clinician to reposition the needle to avoid nerve injury (1).

 

In addition to its clinical applications, PNS plays a valuable role in education and training. For novice practitioners, correlating ultrasound images with evoked motor responses reinforces understanding of anatomical relationships and improves procedural skills. This combined feedback can accelerate the learning process and minimize technical errors during the initial stages of regional anesthesia practice.

 

The role of nerve stimulators in regional anesthesia has evolved with advances in imaging technology, particularly ultrasound-guided blocks. While ultrasound has largely replaced PNS as the primary method of nerve localization, nerve stimulation continues to serve as a valuable adjunct that enhances safety, supports difficult blocks, and facilitates education. A multimodal approach that integrates both techniques offers the most balanced strategy for optimizing outcomes in contemporary regional anesthetic practice.

 

References

 

1. Gadsden JC. The role of peripheral nerve stimulation in the era of ultrasound-guided regional anaesthesia. Anaesthesia. 2021;76 Suppl 1:65-73. doi:10.1111/anae.15257

2. Perlas A, Niazi A, McCartney C, Chan V, Xu D, Abbas S. The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound. Reg Anesth Pain Med. 2006;31(5):445-450. doi:10.1016/j.rapm.2006.05.017

3. Abrahams MS, Aziz MF, Fu RF, Horn JL. Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Br J Anaesth. 2009;102(3):408-417. doi:10.1093/bja/aen384

Traditional regional anesthesia for hand surgery has historically relied on brachial plexus blockade via interscalene, supraclavicular, infraclavicular, or axillary approaches. These proximal techniques anesthetize the terminal branches of the plexus en bloc, producing dense sensory and motor blockade of the upper extremity. While highly effective for surgical anesthesia, they predictably result in global limb weakness and may be associated with complications such as pneumothorax and phrenic nerve–related diaphragmatic paralysis, particularly with interscalene and supraclavicular approaches (1). With advances in regional anesthesia, motor-sparing blocks have become increasingly preferred for hand surgery. Motor-sparing forearm blocks are grounded in precise anatomical localization and ultrasound-guided deposition of low volumes of local anesthetic around individual terminal nerves rather than within the brachial plexus sheath. This selective strategy limits proximal motor involvement while maintaining dense sensory anesthesia of the hand. The median, ulnar, superficial radial, and lateral antebrachial cutaneous nerves are targeted at distal forearm or wrist levels where motor branches have largely separated from sensory components. Chin et al. describe ultrasound-guided motor-sparing forearm blocks as an approach that aligns anesthetic planning with surgical objectives, especially when preserving movement improves procedural accuracy (1). The median nerve block is typically performed in the middle of the forearm, below the flexor digitorum superficialis and profundus muscles, to minimize spread to the motor branches that supply the forearm flexors. Under ultrasound visualization, local anesthetic is deposited within the surrounding fascial plane to achieve volar radial hand anesthesia (2). The ulnar nerve is blocked in the distal half of the forearm, proximal to the dorsal and palmar cutaneous branches yet distal enough to spare motor innervation to the flexor carpi ulnaris. This positioning provides sensory blockade of the ulnar digits without compromising intrinsic or extrinsic muscle strength. The superficial radial nerve, being purely sensory, is anesthetized through subcutaneous infiltration along the dorsolateral wrist. Because the thumb base and lateral wrist may also receive innervation from the lateral antebrachial cutaneous nerves, a supplemental subcutaneous injection superficial to the brachioradialis muscle is frequently added to ensure complete coverage (2). Motor-sparing regional anesthesia is particularly advantageous in hand surgery cases that require a dynamic intraoperative assessment. For example, in flexor and extensor tendon repairs, active motion preservation enables surgeons to evaluate tendon glide, detect gapping at the repair site, and optimize tensioning before closing the incision. Similarly, tendon transfers and reconstructive procedures benefit from immediate assessment of excursion and functional positioning, which cannot be performed under complete motor blockade. Trigger finger release and selective nerve decompression also lend themselves to this approach because real-time feedback confirms the restoration of motion without the interference of limb paralysis. Ultrasound-guided distal blocks have demonstrated effective analgesia with minimal motor impairment in ambulatory hand surgery, supporting early mobilization and discharge (3). By preserving forearm muscle function while providing targeted sensory anesthesia, this approach aligns with modern ambulatory and “wide-awake” surgical models. Ultrasound guidance allows visualization of neural structures, adjacent vessels, and fascial planes. This facilitates low-volume anesthetic deposition and reduces the risk of vascular puncture or intraneural injection (3). Using a small-gauge needle, such as a 25-gauge needle, minimizes patient discomfort during infiltration. The needle tip should be positioned tangentially adjacent to the nerve within the perineural sheath. Incremental injection confirms circumferential spread rather than direct neural penetration. When executed carefully, motor-sparing regional anesthesia is a function-preserving, anatomically rational alternative to traditional brachial plexus blockade in modern hand surgery. References 1. Kowa CY, Ravarian B, Baltzer H, Chin KJ. Ultrasound-guided motor-sparing forearm blocks for hand surgery: surgical and anesthetic perspectives. Reg Anesth Pain Med. Published online December 13, 2025. doi:10.1136/rapm-2025-107388 2. Sehmbi H, Madjdpour C, Shah UJ, Chin KJ. Ultrasound guided distal peripheral nerve block of the upper limb: A technical review. J Anaesthesiol Clin Pharmacol. 2015;31(3):296-307. doi:10.4103/0970-9185.161654 3. Dufeu N, Marchand-Maillet F, Atchabahian A, et al. Efficacy and safety of ultrasound-guided distal blocks for analgesia without motor blockade after ambulatory hand surgery. J Hand Surg Am. 2014;39(4):737-743. doi:10.1016/j.jhsa.2014.01.011

Methadone is a synthetic opioid with unique pharmacokinetic and pharmacodynamic properties that distinguish it from other commonly used opioids. Originally developed as an analgesic and later adopted for opioid use disorder (OUD) treatment, methadone’s duration of action plays a central role in both its therapeutic benefits and its risks. Understanding the distinction between its analgesic duration and elimination half-life is essential for safe and effective clinical use.

 

Methadone acts primarily as a μ-opioid receptor agonist but also exhibits N-methyl-D-aspartate (NMDA) receptor antagonism and inhibits serotonin and norepinephrine reuptake. These additional mechanisms contribute to its efficacy in chronic pain, neuropathic pain, and opioid tolerance. Clinically, methadone’s analgesic duration of action is relatively short, typically lasting 4 to 8 hours after a single dose. This duration is comparable to that of other short-acting opioids and explains why methadone, when used for pain management, often requires divided dosing throughout the day.

 

In contrast, methadone’s elimination half-life is prolonged and highly variable, ranging from approximately 8 hours to more than 50, with reports of even longer half-lives in some individuals. This disparity between analgesic duration and elimination half-life is one of methadone’s most clinically significant features. While analgesia may wane within hours, the drug continues to accumulate in tissues and plasma with repeated dosing. As a result, steady-state concentrations may not be achieved for several days, increasing the risk of delayed toxicity if doses are escalated too rapidly.

 

The prolonged and variable half-life of methadone is largely explained by its pharmacokinetics. Methadone is highly lipophilic, leading to extensive tissue distribution and slow release back into circulation. It is metabolized primarily by hepatic cytochrome P450 enzymes, including CYP3A4, CYP2B6, and CYP2D6, which exhibit significant interindividual variability. Genetic polymorphisms, drug–drug interactions, and hepatic function can therefore markedly influence methadone clearance and duration of action.

 

In the treatment of opioid use disorder, methadone’s long duration of action is therapeutically advantageous. Once-daily dosing suppresses opioid withdrawal symptoms and cravings for 24 hours or longer, while also attenuating the euphoric effects of shorter-acting opioids. This pharmacologic profile supports treatment adherence and reduces illicit opioid use. However, the same properties necessitate careful induction and titration, particularly during the first one to two weeks of therapy, when accumulation can lead to oversedation or respiratory depression.

Methadone’s extended duration of action also has important safety implications. Respiratory depression may occur late after dosing, especially during initiation or dose increases. Additionally, methadone is associated with QT interval prolongation, a risk that may increase with higher plasma concentrations and prolonged exposure. These factors underscore the need for cautious dosing, patient education, and, in selected cases, electrocardiographic monitoring.

 

Methadone’s duration of action is characterized by a short analgesic effect and a long, variable elimination half-life. This unique pharmacologic profile underlies its effectiveness in chronic pain and opioid use disorder while also contributing to its narrow therapeutic margin. Clinicians must account for these properties to maximize benefit and minimize harm when prescribing methadone.

 

References

1. Eap CB, Buclin T, Baumann P. Interindividual variability of the clinical pharmacokinetics of methadone: implications for the treatment of opioid dependence. Clin Pharmacokinet. 2002;41(14):1153-1193. DOI: 10.2165/00003088-200241140-00003
2. Kreek MJ. Methadone-related opioid agonist pharmacotherapy for heroin addiction. Ann N Y Acad Sci. 2000;909:186-216. DOI: 10.1111/j.1749-6632.2000.tb06683.x
3. Inturrisi CE. Pharmacology of methadone and its isomers. Minerva Anestesiol. 2005;71(7-8):435-437.
4. Chou R, Cruciani RA, Fiellin DA, et al. Methadone safety: a clinical practice guideline from the American Pain Society. J Pain. 2014;15(4):321-337. DOI: 10.1016/j.jpain.2014.01.494
5. Ferrari A, Coccia CP, Bertolini A, Sternieri E. Methadone—metabolism, pharmacokinetics and interactions. Pharmacol Res. 2004;50(6):551-559. DOI: 10.1016/j.phrs.2004.05.002