Mandeep Singh

Proportion of surgical patients with undiagnosed obstructive sleep apnoea

BACKGROUNDnObstructive sleep apnoea (OSA) affects ~9-24% of the general population, and 90% remain undiagnosed. Those patients with undiagnosed moderate-to-severe OSA may be associated with an increased risk of perioperative complications. Our objective was to evaluate the proportion of surgical patients with undiagnosed moderate-to-severe OSA.nnnMETHODSnAfter research ethics board approval, patients visiting preoperative clinics were recruited over 4 yr and screened with the STOP-BANG questionnaire. The 1085 patients, who consented, subsequently underwent polysomnography (PSG) (laboratory or portable) before operation. Chart review was conducted in this historical cohort to ascertain the clinical diagnosis of OSA by surgeons and anaesthetists, blinded to the PSG results. The PSG study-identified OSA patients were further classified based on severity using the apnoea-hypopnoea index (AHI) cut-offs.nnnRESULTSnOf 819 patients, 111 patients had pre-existing OSA and 58% (64/111) were not diagnosed by the surgeons and 15% (17/111) were not diagnosed by the anaesthetists. Among the 708 study patients, PSG showed that 233 (31%) had no OSA, 218 (31%) patients had mild OSA (AHI: 5-15); 148 (21%) had moderate OSA (AHI: 15-30), and 119 (17%) had severe OSA (AHI>30). Before operation, of the 267 patients with moderate-to-severe OSA, 92% (n=245) and 60% (n=159) were not diagnosed by the surgeons and the anaesthetists, respectively.nnnCONCLUSIONSnWe found that anaesthetists and surgeons failed to identify a significant number of patients with pre-existing OSA and symptomatic undiagnosed OSA, before operation. This study may provide an impetus for more diligent case finding of OSA before operation.

Use of Sonography for Airway Assessment An Observational Study

Objective. The purpose of this study was to evaluate the feasibility of sonography in identifying the anatomic structures of the upper airway and to describe their appearance on sonography. Methods. We enrolled 24 healthy volunteers, placed them supine with their head extended and neck flexed (the “sniffing” position), and performed a systematic sonographic examination of their upper airway from the floor of the mouth to the suprasternal notch. Results. We were able to visualize all relevant anatomic structures in all of the participants using either a linear or curved transducer oriented in 1 of 3 planes: sagittal, parasagittal, and transverse. Bony structures (eg, the mandible and hyoid) were brightly hyperechoic with an underlying hypoechoic acoustic shadow. Cartilaginous structures (eg, the epiglottis, thyroid cartilage, cricoid cartilage, and tracheal rings) were hypoechoic, and their intraluminal surface was outlined by a bright air‐mucosa interface. The vocal cords were readily visualized through the thyroid cartilage. However, the posterior pharynx, posterior commissure, and posterior wall of the trachea could not be visualized because of artifacts created by an intraluminal air column. Conclusions. Sonography of the upper airway is capable of providing detailed anatomic information and has numerous potential clinical applications.

CPAP in the Perioperative Setting: Evidence of Support

OSA is a commonly encountered comorbid condition in surgical patients. The risk of cardiopulmonary complications is increased by two to threefold with OSA. Among the different treatment options for OSA, CPAP is an efficacious modality. This review examines the evidence regarding the use of CPAP in the preoperative and postoperative periods in surgical patients with diagnosed and undiagnosed OSA.

Infraclavicular brachial plexus block for regional anaesthesia of the lower arm.

BACKGROUNDnSeveral approaches exist to produce local anaesthetic blockade of the brachial plexus. It is not clear which is the technique of choice for providing surgical anaesthesia of the lower arm, although infraclavicular blockade (ICB) has several purported advantages. We therefore performed a systematic review of ICB compared to the other brachial plexus blocks (BPBs). This review was originally published in 2010 and was updated in 2013.nnnOBJECTIVESnThe objective of this review was to evaluate the efficacy and safety of infraclavicular block (ICB) compared to other approaches to the brachial plexus in providing regional anaesthesia for surgery on the lower arm.nnnSEARCH METHODSnWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2013, Issue 5); MEDLINE (1966 to June 2013) via OvidSP; and EMBASE (1980 to June 2013) via OvidSP. We also searched conference proceedings (from 2004 to 2012) and the www.clinicaltrials.gov trials registry. The searches for the original review were performed in September 2008.nnnSELECTION CRITERIAnWe included any randomized controlled trials (RCTs) that compared ICB with other BPBs as the sole anaesthetic technique for surgery on the lower arm.nnnDATA COLLECTION AND ANALYSISnThe primary outcome was adequate surgical anaesthesia within 30 minutes of block completion. Secondary outcomes included sensory block of individual nerves, tourniquet pain, onset time of sensory blockade, block performance time, block-associated pain and complications related to the block.nnnMAIN RESULTSnIn our original review we included 15 studies with 1020 participants and excluded two. In this updated review we included seven new studies and excluded six, bringing the total number of included studies to 22 and involving 1732 participants. The control group intervention was the axillary block in 14 studies, supraclavicular block in six studies, mid-humeral block in two studies, and parascalene block in one study. One study compared ICB to both axillary and supraclavicular blocks. Nine studies employed ultrasound-guided ICB. The risk of failed surgical anaesthesia 30 minutes after block completion was similar for ICB and all other BPBs (11.4% versus 12.9%, risk ratio (RR) 0.88, 95% CI 0.51 to 1.52, P = 0.64), but tourniquet pain was less likely with ICB (11.9% versus 18.0%; RR of experiencing tourniquet pain 0.66, 95% CI 0.47 to 0.92, P = 0.02). Subgroup analysis by method of nerve localization, and by control group intervention, did not show any statistically significant differences in the risk of failed surgical anaesthesia. However when compared to a single-injection axillary block, ICB was better at providing complete sensory block of the musculocutaneous nerve (RR for failure 0.46, 95% CI 0.27 to 0.60, P < 0.0001). ICB had a slightly longer sensory block onset time (mean difference (MD) 1.9 min, 95% CI 0.2 to 3.6, P = 0.03) but was faster to perform than multiple-injection axillary (MD -2.7 min, 95% CI -3.4 to -2.0, P < 0.00001) or mid-humeral (MD -4.8 min, 95% CI -6.0 to -3.6, P < 0.00001) blocks.nnnAUTHORS CONCLUSIONSnICB is as safe and effective as any other BPBs, regardless of whether ultrasound or neurostimulation guidance is used. The advantages of ICB include a lower likelihood of tourniquet pain during surgery, more reliable blockade of the musculocutaneous nerve when compared to a single-injection axillary block, and a significantly shorter block performance time compared to multi-injection axillary and mid-humeral blocks.

Infraclavicular brachial plexus block for regional anaesthesia of the lower arm

BACKGROUND:Several approaches exist to produce local anaesthetic blockade of the brachial plexus. It is not clear which is the technique of choice for providing surgical anaesthesia of the lower arm although infraclavicular blockade (ICB) has several purported advantages. We therefore performed a systematic review of ICB compared to the other brachial plexus blocks (BPBs). OBJECTIVES:To evaluate the efficacy and safety of ICB compared to other BPBs in providing regional anaesthesia of the lower arm. SEARCH STRATEGY:We searched CENTRAL (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to September 22nd 2008) and EMBASE (1980 to September 22nd 2008). We also searched conference proceedings (from 2004 to 2008) and the www.clinicaltrials.gov registry. No language restriction was applied. SELECTION CRITERIA:We included any randomized controlled trials (RCTs) that compared ICB with other BPBs as the sole anaesthetic techniques for surgery on the lower arm. DATA COLLECTION AND ANALYSIS:The primary outcome was adequate surgical anaesthesia within 30 minutes of block completion. Secondary outcomes included sensory block of individual nerves, tourniquet pain, onset time of sensory blockade, block performance time, block-associated pain and complications related to the block. MAIN RESULTS:We identified 15 studies with 1020 participants, of whom 510 received ICB and 510 received other BPBs. The control group intervention was the axillary block in 10 studies, mid-humeral block in two studies, supraclavicular block in two studies and parascalene block in one study. Three studies employed ultrasound-guided ICB. The risk of failed surgical anaesthesia and of complications were low and similar for ICB and all other BPBs. Tourniquet pain was less likely with ICB (risk ratio (RR) 0.47, 95% CI 0.24 to 0.92, P = 0.03). When compared to a single-injection axillary block, ICB was better at providing complete sensory block of the musculocutaneous nerve (RR for failure 0.46, 95% CI 0.27 to 0.60, P < 0.0001) and the axillary nerve (RR of failure 0.37, 95% CI 0.24 to 0.58, P < 0.0001). ICB was faster to perform than multiple-injection axillary (mean difference (MD) −2.7 min, 95% CI −4.2 to −1.1, P = 0.0006) or midhumeral blocks (MD −4.8 min, 95% CI −6.0 to −3.6, P < 0.00001) but this was offset by a longer sensory block onset time (MD 3.9 min, 95% CI 3.2 to 4.5, P < 0.00001). AUTHORS CONCLUSIONS:ICB is a safe and simple technique for providing surgical anaesthesia of the lower arm, with an efficacy comparable to other BPBs. The advantages of ICB include a lower likelihood of tourniquet pain during surgery, and more reliable blockade of the musculocutaneous and axillary nerves when compared to a single-injection axillary block. The efficacy of ICB is likely to be improved if adequate time is allowed for block onset (at least 30 minutes) and if a volume of at least 40 ml is injected. Since publication of many of the trials included in this review, it has become clear that a distal posterior cord motor response is the appropriate endpoint for electrostimulation-guided ICB; we recommend it be used in all future comparative studies. There is also a need for additional RCTs comparing ultrasound-guided ICB with other BPBs.

Ultrasound imaging of the airway

To the Editor, We read with interest the articles by Tsui et al. regarding ultrasound imaging of the airway using a sublingual scanning approach. A small footprint high frequency curved transducer placed intra-orally failed to capture images of the epiglottis and the laryngeal inlet due to posterior acoustic shadowing of the hyoid bone. Transcutaneous ultrasound scanning of the airway may overcome some of these challenges. In our pilot study, we were able to image airway structures in the transverse and parasagittal (1 cm away from midline) views using a linear 38 mm, 13–6 MHz transducer with the Sonosite M-Turbo ultrasound machine (Bothell, WA, USA). The epiglottis can be visualized (Fig. 1) through the transverse and parasagittal windows both above and below the hyoid bone. Because the hyoid bone casts an acoustic shadow posteriorly, part of the epiglottis is obscured. The epiglottis is best seen through the hyo-thyroid window between the hyoid bone and the thyroid cartilage. It appears as a hypoechoic structure with a curvilinear shape on parasagittal view and an inverted ‘C’ on transverse view. It is related anteriorly by the hyperechoic triangular preepiglottic space and lined posteriorly by a hyperechoic air–mucosa interface. Compared with the sublingual technique, the transcutaneous scan has several advantages. A high frequency transducer for transcutaneous scan captures images of higher resolution. A good transducer to skin contact can be maintained even at the level of the thyroid prominence with the linear transducer in the parasagittal position. Visualization of the epiglottis is possible without ultrasound beam interference due to hyoid acoustic shadow and attenuation by hypopharyngeal air (as seen with the sublingual scan). Furthermore, airway scanning at the level of the laryngeal inlet is possible and not impaired by restricted caudad transducer angulation due to the presence of upper incisors or the smaller capacity of the sublingual space (as seen with the sublingual scan). Both scanning approaches visualize tongue substance and musculature. Future studies will determine if the sublingual and transcutaneous approaches are complementary to each other. Ultrasound may prove to be an exciting evaluation tool for airway structures and ease of intubation.

Postoperative Oxygen Therapy in Patients With OSA: A Randomized Controlled Trial

BACKGROUND: Surgical patients with OSA are at increased risk for perioperative complications. Postoperative supplemental oxygen is commonly used, but it may contribute to respiratory depression in patients with OSA receiving opioids. The objective of the study is to investigate the effect of postoperative supplemental oxygen on arterial oxygen saturation (Sao2), sleep respiratory events, and CO2 level in patients with untreated OSA. METHODS: Consented patients with an apnea hypopnea index (AHI) > 5 events per hour on a preoperative polysomnography were randomized (1:1) to oxygen (O2 group) or no oxygen (control group). The O2 group received oxygen at 3 L/min via nasal prongs for three postoperative nights. The primary outcomes were polysomnographic parameters measuring Sao2, sleep respiratory events, and Pco2 measured by transcutaneous CO2 monitor (PtcCO2) on nights 1 through 3. The intention‐to‐treat and per protocol analysis were completed. RESULTS: There were 123 patients randomized (O2 group: n = 62; control group: n = 61). On night 3, the O2 vs control group had a higher average Sao2 (95.2% ± 3% vs 91.4% ± 4%, respectively; P < .001) and lower oxygen desaturation index (median, 2.3; 25th‐75th percentile, 0.2–13.8 vs median, 18.5; 25th‐75th percentile, 8.2–45.9 events per hour, respectively; P < .0001). The O2 group had a decreased AHI (median, 8.0; 25th‐75th percentile, 2.1–19.9 vs median, 15.6; 25th‐75th percentile, 9.5–45.8, respectively; P = .016), hypopnea index (P < .001), and central apnea index (P = .026) and a shortened longest apnea hypopnea duration (P = .002). Although time percentage with PtcCO2 ≥ 55 mm Hg ≥ 10% on postoperative night 1, 2, or 3 was found in 11.4% patients, there was no difference in PtcCO2 between the groups. CONCLUSIONS: Postoperative supplemental oxygen was found to improve oxygenation and decrease the AHI without increasing the duration of apnea‐hypopnea event or PtcCO2 level. A small number of patients had significant CO2 retention while receiving supplemental oxygen. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01552304; URL: www.clinicaltrials.gov

Postoperative Oxygen Therapy in Patients with Obstructive Sleep Apnea: A Randomized Controlled Trial.

BACKGROUND: Surgical patients with OSA are at increased risk for perioperative complications. Postoperative supplemental oxygen is commonly used, but it may contribute to respiratory depression in patients with OSA receiving opioids. The objective of the study is to investigate the effect of postoperative supplemental oxygen on arterial oxygen saturation (Sao2), sleep respiratory events, and CO2 level in patients with untreated OSA. METHODS: Consented patients with an apnea hypopnea index (AHI) > 5 events per hour on a preoperative polysomnography were randomized (1:1) to oxygen (O2 group) or no oxygen (control group). The O2 group received oxygen at 3 L/min via nasal prongs for three postoperative nights. The primary outcomes were polysomnographic parameters measuring Sao2, sleep respiratory events, and Pco2 measured by transcutaneous CO2 monitor (PtcCO2) on nights 1 through 3. The intention‐to‐treat and per protocol analysis were completed. RESULTS: There were 123 patients randomized (O2 group: n = 62; control group: n = 61). On night 3, the O2 vs control group had a higher average Sao2 (95.2% ± 3% vs 91.4% ± 4%, respectively; P < .001) and lower oxygen desaturation index (median, 2.3; 25th‐75th percentile, 0.2–13.8 vs median, 18.5; 25th‐75th percentile, 8.2–45.9 events per hour, respectively; P < .0001). The O2 group had a decreased AHI (median, 8.0; 25th‐75th percentile, 2.1–19.9 vs median, 15.6; 25th‐75th percentile, 9.5–45.8, respectively; P = .016), hypopnea index (P < .001), and central apnea index (P = .026) and a shortened longest apnea hypopnea duration (P = .002). Although time percentage with PtcCO2 ≥ 55 mm Hg ≥ 10% on postoperative night 1, 2, or 3 was found in 11.4% patients, there was no difference in PtcCO2 between the groups. CONCLUSIONS: Postoperative supplemental oxygen was found to improve oxygenation and decrease the AHI without increasing the duration of apnea‐hypopnea event or PtcCO2 level. A small number of patients had significant CO2 retention while receiving supplemental oxygen. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01552304; URL: www.clinicaltrials.gov

Musculoskeletal Sonopathology and Ultrasound-Guided Regional Anesthesia

The use of real-time ultrasound guidance has revolutionized the practice of regional anesthesia. Ultrasound is rapidly becoming the technique of choice for nerve blockade due to increased success rates, faster onset, and potentially improved safety. In the course of ultrasound-guided regional anesthesia, unexpected pathology may be encountered. Such anomalous or pathological findings may alter the choice of nerve block and occasionally affect surgical management. This case series presents a variety of musculoskeletal conditions that may be encountered during ultrasound-guided regional anesthesia practice.

Interpretation of sleep studies for patients with sleep-disordered breathing: What the anesthesiologist needs to know

There is increased interest in the perioperative management of patients with sleep-disordered breathing (SDB). Anesthesiologists must distill information from clinical reports to make key decisions for optimizing perioperative care. A patient with SDB may present with a sleep study report at the time of surgery. Knowledge of the essential components of such a report can help the anesthesiologist evaluate the patient and optimize the perioperative management. In this narrative review, we describe how level I (i.e., laboratory-based) polysomnography (PSG) data are collected and scored using the recommended scoring guidelines, as well as the basic information and salient features of a typical PSG report relevant to the anesthesiologist. In addition, we briefly review the indications for sleep studies, including the types of laboratory-based studies, as well as the role and limitations of portable monitors (level II-IV studies) and examples of PSG reports in the clinical context.RésuméLa prise en charge périopératoire des patients souffrant de troubles respiratoires du sommeil (TRS) suscite un intérêt croissant. Les anesthésiologistes doivent extraire les informations issues de comptes rendus cliniques afin de prendre des décisions cruciales à l’optimisation des soins périopératoires. Il arrive qu’un patient atteint de TRS se présente avec un rapport d’étude du sommeil au moment de sa chirurgie. Une connaissance des composantes essentielles d’un tel rapport peut aider l’anesthésiologiste à évaluer le patient et optimiser sa prise en charge périopératoire. Dans ce compte rendu narratif, nous décrivons comment les données de polysomnographie (PSG) de niveau I (c.-à-d. réalisée en laboratoire) sont colligées et notées à l’aide des directives de notation recommandées, ainsi que les informations de base et les caractéristiques principales d’un rapport typique de PSG pertinentes à l’anesthésiologiste. En outre, nous passons brièvement en revue les indications des études sur le sommeil, notamment les types d’études de laboratoire, ainsi que le rôle et les limites des moniteurs portables (études de niveau II-IV) et présentons quelques exemples de rapports de PSG dans le contexte clinique.