Mohammad El-Orbany

Rapid Sequence Induction and Intubation: Current Controversy

The changing opinion regarding some of the traditional components of rapid sequence induction and intubation (RSII) creates wide practice variations that impede attempts to establish a standard RSII protocol. There is controversy regarding the choice of induction drug, the dose, and the method of administration. Whereas some prefer the traditional rapid injection of a predetermined dose, others use the titration to loss of consciousness technique. The timing of neuromuscular blocking drug (NMBD) administration is different in both techniques. Whereas the NMBD should immediately follow the induction drug in the traditional technique, it is only given after establishing loss of consciousness in the titration technique. The optimal dose of succinylcholine is controversial with advocates and opponents for both higher and lower doses than the currently recommended 1.0 to 1.5 mg/kg dose. Defasciculation before succinylcholine was traditionally recommended in RSII but is currently controversial. Although the priming technique was advocated to accelerate onset of nondepolarizing NMBDs, its use has decreased because of potential complications and the introduction of rocuronium. Avoidance of manual ventilation before tracheal intubation was traditionally recommended to avoid gastric insufflation, but its use is currently acceptable and even recommended by some to avoid hypoxemia and to “test” the ability to mask ventilate. Cricoid pressure remains the most heated controversy; some believe in its effectiveness in preventing pulmonary aspiration, whereas others believe it should be abandoned because of the lack of scientific evidence of benefit and possible complications. There is still controversy regarding the best position and whether the head-up, head-down, or supine position is the safest during induction of anesthesia in full-stomach patients. These controversial components need to be discussed, studied, and resolved before establishing a standard RSII protocol.

Difficult Mask Ventilation

Mask ventilation is the most fundamental skill in airway management. In this review, we summarize the current knowledge about difficult mask ventilation (DMV) situations. Various definitions for DMV have been used in the literature. The lack of a precise standard definition creates a problem for studies on DMV and causes confusion in data communication and comparisons. DMV develops because of multiple factors that are technique related and/or airway related. Frequently, the pathogenesis involves a combination of these factors interacting to cause the final clinical picture. The reported incidence of DMV varies widely (from 0.08% to 15%) depending on the criteria used for its definition. Obesity, age older than 55 yr, history of snoring, lack of teeth, the presence of a beard, Mallampati Class III or IV, and abnormal mandibular protrusion test are all independent predictors of DMV. These signs should, therefore, be recognized and documented during the preoperative evaluation. DMV can be even more challenging in infants and children, because they develop hypoxemia much faster than adults. Finally, difficult tracheal intubation is more frequent in patients who experience DMV, and thus, clinicians should be familiar with the corrective measures and management options when faced with a challenging, difficult, or impossible mask ventilation situation.

Head and neck position for direct laryngoscopy.

The sniffing position (SP) has traditionally been considered the optimal head position for direct laryngoscopy (DL). Its superiority over other head positions, however, has been questioned during the last decade. We reviewed the scarce literature on the subject to examine the evidence either in favor or against the routine use of the SP. A standard definition for the position should be used (e.g., 35° neck flexion and 15° head extension) to avoid confusion about what constitutes a proper SP and to compare the results from different studies. Although several theories were proposed to explain the superiority of the SP, the three axes alignment theory is still considered a valid anatomical explanation. Although head elevation is needed to achieve the desired neck flexion, the elevation height may vary from one patient to another depending on head and neck anatomy and size of the chest. In infants and small children, for example, no head elevation is needed because the size and shape of the head allow axes approximation in the head-flat position. Horizontal alignment of the external auditory meatus with the sternum, in both obese and non-obese patients, indicates, and can be used as a marker for, proper positioning. Analysis of the available literature supports the use of the SP for DL. To achieve a proper SP in obese patients, the “ramped” (or the back-up) position should be used. The SP does not guarantee adequate exposure in all patients, because many other anatomical factors control the final degree of visualization. However, it should be the starting head position for DL because it provides the best chance at adequate exposure. Attention to details during positioning and avoidance of minor technical errors are essential to achieve the proper position. DL should be a dynamic procedure and position adjustment should be instituted in case poor visualization is encountered in the SP.

Preoxygenation with tidal volume and deep breathing techniques : The impact of duration of breathing and fresh gas flow

Various techniques of “preoxygenation” before anesthetic induction have been advocated, including tidal volume breathing (TVB) for 3–5 min, four deep breaths (DB) in 0.5 min, and eight DB in 1 min. However, no study has compared the effectiveness of these techniques, assessed extending deep breathing beyond 1 min, or investigated the influence of fresh gas flow (FGF) in the same subjects using a circle absorber system. In 24 healthy adult volunteers breathing oxygen from a circle absorber system by tight-fitting mask, we compared TVB/5 min and deep breathing at a rate of 4 DB/0.5 min for 2 min at 5, 7, and 10 L/min FGF. Inspired and end-tidal respiratory gases were measured at 0.5-min intervals. During TVB, end-tidal oxygen (ETO2) increased rapidly and plateaued by 2.5 min at 86%, 88%, and 88% with 5, 7 and 10 L/min FGF, respectively. ETO2 values of ≥90% were attained between 3 and 4 min. Four DB/0.5 min increased ETO2 to 75%, 77%, and 80% at 5, 7, and 10 L/min FGF. Eight DB/min resulted in ETO2 values of 82% and 87% at 7 and 10 L/min, respectively. Extending deep breathing to 1.5 and 2 min with 10 L/min FGF increased ETO2 by ≥90%, although a decrease in ETco2 was noted. We concluded that TVB/3–5 min was effective in achieving maximal “preoxygenation” whereas 4 DB/0.5 min resulted in submaximal “preoxygenation,” and thus should be used only when time is limited. Increasing FGF from 5 to 10 L/min does not enhance “preoxygenation” with either TVB or 4 DB/0.5 min. Deep breathing yields maximal “preoxygenation” when extended to 1.5 or 2 min, and only when high (10 L/min) FGF is used.

Reversal of profound vecuronium-induced neuromuscular block under sevoflurane anesthesia: sugammadex versus neostigmine.

BackgroundAcetylcholinesterase inhibitors cannot rapidly reverse profound neuromuscular block. Sugammadex, a selective relaxant binding agent, reverses the effects of rocuronium and vecuronium by encapsulation. This study assessed the efficacy of sugammadex compared with neostigmine in reversal of profound vecuronium-induced neuromuscular block under sevoflurane anesthesia.MethodsPatients aged ≥18 years, American Society of Anesthesiologists class 1-4, scheduled to undergo surgery under general anesthesia were enrolled in this phase III, multicenter, randomized, safety-assessor blinded study. Sevoflurane anesthetized patients received vecuronium 0.1 mg/kg for intubation, with maintenance doses of 0.015 mg/kg as required. Patients were randomized to receive sugammadex 4 mg/kg or neostigmine 70 μg/kg with glycopyrrolate 14 μg/kg at 1-2 post-tetanic counts. The primary efficacy variable was time from start of study drug administration to recovery of the train-of-four ratio to 0.9. Safety assessments included physical examination, laboratory data, vital signs, and adverse events.ResultsEighty three patients were included in the intent-to-treat population (sugammadex, n = 47; neostigmine, n = 36). Geometric mean time to recovery of the train-of-four ratio to 0.9 was 15-fold faster with sugammadex (4.5 minutes) compared with neostigmine (66.2 minutes; p < 0.0001) (median, 3.3 minutes with sugammadex versus 49.9 minutes with neostigmine). No serious drug-related adverse events occurred in either group.ConclusionsRecovery from profound vecuronium-induced block is significantly faster with sugammadex, compared with neostigmine. Neostigmine did not rapidly reverse profound neuromuscular block (Trial registration number: NCT00473694).

The Eschmann tracheal tube introducer is not gum, elastic, or a bougie

To the Editor:—The case reported by Dietrich and Smith again demonstrates that performing steroid epidural injections under fluoroscopic guidance does not absolutely prevent perforation of the dura by the needle tip, because the needle is usually advanced before the next bolus of dye is injected. Measurements of skin to epidural space in magnetic resonance imaging films showed that the posterior epidural space at C6–C7 averages 3 mm in adults; in the case in question, it was not visible in the magnetic resonance imaging in figure 1 or in the computerized tomography scan in figure 3. There are two possible explanations. One is shown in figures 1 and 2 demonstrating that the patient had Chiari I syndrome usually accompanied by a narrow posterior cervical epidural and intrathecal compartments. The other is the C6–C7 space, where a herniated nucleus pulposus is still present, displacing the dural sac posteriorly. There is no posterior epidural space in either figure 1 or figure 3, as noted before. As far as how the mass got there, if the steroid was injected epidurally, the substance loculated anteriorly where there was more room. Because the epidural space stops at the foramen magnum, it is likely that some of it went intrathecally through the previously made orifice, distributing through the subdural space above the clivus and other areas (figs. 1 and 2). However, 4 weeks is too soon to develop a granuloma, which was not seen at the time of surgery. Most likely, what the authors called collections is more likely the “depo” vehicle of triamcinolone preparation. Interestingly enough, when this type of steroid is deposited epidurally, the steroid fraction is absorbed within 2 days into the circulation; it does not cross the dura, as long as it remains intact. The depo vehicle may stay in the epidural compartment for 2–6 weeks. Three doses of 60 mg triamcinolone given within 1 month may be responsible for the accumulation of this substance in the anterior cervical epidural space and the smaller fractions shown intracranially (even after the drainage of the anterior epidural mass). The so-called intracranial hypotension was leakage of cerebrospinal fluid through the hole made at the time of the last epidural steroid injection. The hanging drop method is not an appropriate technique in the absence of cervical epidural space, although it can be distended if a solution is injected from below. There is no solid evidence that depositing the steroid medication precisely in the intervertebral space where pathologic findings have been reported produces better results than if injected one or two spaces away or, for that reason, if steroids are deposited paravertebrally. Cervical epidural steroid injection can be performed safely and effectively at C7–T1, where there is consistently a wider epidural space that can be reached in more than 85% of the patients with a 11/2-in-long needle without danger of perforating the dura. Without doubt, a “lightening bolt” sensation with radicular distribution, while the physician is looking for the epidural space, means paraesthesia on one of the intrathecal nerve roots, because there are not nerve roots in the posterior epidural space. If there is a “wet tap,” the injection of steroids should be deleted because every steroid preparation available in the United States has preservatives and triamcinolone has polyethylene glycol and benzylic alcohol that may enter the subarachnoid space, initiating an inflammatory reaction in the arachnoid. These are not urgent procedures, and the usual option of trying one space above is not applicable because the medication may pass through the previously made hole, as in this case. One hopes that the autologous blood and the fibrin, both well-known central nervous system irritants, injected in the anterior epidural space will not produce arachnoiditis at the operative level. After all, it was neither a granuloma nor a case of primary intracranial hypotension.

Gastric tubes and airway management in patients at risk of aspiration: history, current concepts, and proposal of an algorithm.

Rapid sequence induction and intubation (RSII) and awake tracheal intubation are commonly used anesthetic techniques in patients at risk of pulmonary aspiration of gastric or esophageal contents. Some of these patients may have a gastric tube (GT) placed preoperatively. Currently, there are no guidelines regarding which patient should have a GT placed before anesthetic induction. Furthermore, clinicians are not in agreement as to whether to keep a GT in situ, or to partially or completely withdraw it before anesthetic induction. In this review we provide a historical perspective of the use of GTs during anesthetic induction in patients at risk of pulmonary aspiration. Before the introduction of cricoid pressure (CP) in 1961, various techniques were used including RSII combined with a head-up tilt. Sellick initially recommended the withdrawal of the GT before anesthetic induction. He hypothesized that a GT increases the risk of regurgitation and interferes with the compression of the upper esophagus during CP. He later modified his view and emphasized the safety of CP in the presence of a GT. Despite subsequent studies supporting the effectiveness of CP in occluding the esophagus around a GT, Sellick’s early view has been perpetuated by investigators who recommend partial or complete withdrawal of the GT. On the basis of available information, we have formulated an algorithm for airway management in patients at risk of aspiration of gastric or esophageal contents. The approach in an individual patient depends on: the procedure; type and severity of the underlying pathology; state of consciousness; likelihood of difficult airway; whether or not the GT is in place; contraindications to the use of RSII or CP. The algorithm calls for the preanesthetic use of a large-bore GT to remove undigested food particles and awake intubation in patients with achalasia, and emptying the pouch by external pressure and avoidance of a GT in patients with Zenker diverticulum. It also stipulates that in patients with gastric distension without predictable airway difficulties, a clinical and imaging assessment will determine the need for a GT and in severe cases an attempt to insert a GT should be made. In the latter cases, the success of placement will indicate whether to use RSII or awake intubation. The GT should not be withdrawn and should be connected to suction during induction. Airway management and the use of GTs in the surgical correction of certain gastrointestinal anomalies in infants and children are discussed.

Head elevation improves laryngeal exposure with direct laryngoscopy

STUDY OBJECTIVE The aim of this study was to examine the effect of changing head position on the laryngeal view in the same subject. DESIGN Prospective, randomized, crossover comparison of laryngeal views. SETTING Operating suite at a university-affiliated, community hospital. PATIENTS One hundred sixty-seven consenting adult patients scheduled to undergo elective surgery with general anesthesia. INTERVENTIONS After anesthesia induction and muscle relaxation and the head in extended position, the laryngeal view was graded in 3 different head height positions. A special inflatable pillow was placed under the subjects head before induction and was deflated to produce no head elevation or inflated to produce either 6.0cm (sniffing position), or 10.0cm elevation (elevated sniffing position) in random order. MAIN RESULTS The incidence of difficult laryngoscopy (grade ≥3) was 8.38% with no head elevation, 2.39% in the sniffing position, and 1.19% in the elevated sniffing position. Head elevation was not associated with a worse grade in any single patient. CONCLUSIONS Sniffing position improves glottic exposure when the laryngoscopic grade is greater than 1 in the head-flat position. The elevated sniffing position improves the view to a better grade in some patients. Because head elevation was not associated with a worse grade in any subject, the elevated sniffing position should be considered as the initial head position before direct laryngoscopy when a difficult exposure is anticipated.

Endotracheal tube cuff leaks: causes, consequences, and management.

The consequences of endotracheal tube (ETT) cuff leak may range from a bubbling noise to a life-threatening ventilatory failure. Although the definitive solution is ETT replacement, this is often neither needed nor safe to perform. Frequently, the leak is not caused by a structural defect in the ETT. Cuff underinflation, cephalad migration of the ETT (partial tracheal extubation), misplaced orogastric or nasogastric tubes, wide discrepancy between ETT and tracheal diameters, or increased peak airway pressure can cause leaks around intact cuffs. Correction of these problems will stop the leak without ETT replacement. Alternatively, ETT cuff, pilot balloon, and inflation system damage due to inadvertent trauma or manufacturing defects may be responsible. Conservative management ideas (management without ETT replacement) were previously published to solve the problem. However, when a large structural defect is identified or conservative measures fail, ETT replacement becomes necessary. This can be performed with direct laryngoscopy if laryngeal visualization is adequate. A difficult exchange with possible airway loss should be anticipated, and prepared for, when there are signs and/or history of difficult intubation. A risk/benefit analysis of each individual situation is warranted before decisions are made on how best to proceed. Alternative back-up ventilation plans should be preformulated and the necessary equipment ready before the exchange. In this review, various management concerns and plans are discussed, and a simple algorithm to manage leaky ETT cuff situations is presented.

Hemodilution does not alter the coronary vasodilating effects of endogenous or exogenous nitric oxide.

Introduction: It is well known that hemoglobin is a scavenger of nitric oxide (NO). The present study used a canine model to test the hypothesis that acute normovolemic hemodilution (ANH) affects NO-mediated coronary vasodilation.Methods: Studies were performed in 18 open-chest, anesthetized dogs. In Series 1, the contribution of endogenous NO to coronary vasodilatation during ANH with 5% dextran-40 (reduction in hematocrit by 50%) was assessed. This was accomplished by comparing myocardial blood flow (MBF; radioactive microspheres) in the left anterior descending (LAD) region, which was treated with the NO synthase inhibitor, NG-nitro-Larginine methyl ester (L-NAME), to that in the circumflex (control) region. In Series 2, the LAD was perfused via a controlledpressure extracorporeal system with coronary blood flow (CBF) measured with an ultrasonic, transit-time flow transducer. The dose-dependent increases in CBF caused by acetylcholine (ACh), which releases endogenous NO from the vascular endothelium, and sodium nitroprusside (SNP), which provides exogenous NO, were compared before and during ANH.Results: Acute normovolemic hemodilution caused similar (approximately twofold) increases in MBF (P<0.01) in the absence and presence of L-NAME, and it did not affect the dose-related increases in CBF caused by ACh and SNP.Conclusions: Series 1: under baseline conditions, hemoglobin in red blood cells does not limit the coronary vasodilatation resulting from tonic release of NO; NO does not mediate coronary vasodilation during ANH. Series 2: ANH does not influence the coronary vasodilating effects of increased levels of NO, whether due to endogenous release (ACh) or infusion of an NO donor (SNP).RésuméIntroduction: Le fait que l’hémoglobine puisse désactiver l’oxyde nitrique (NO) est bien connu. Cette étude s’est servi d’un modèle canin pour tester l’hypothèse que l’hémodilution normovolémique aiguë (ANH) affecte la vasodilatation coronarienne produite par l’oxyde nitrique.Méthode: Les études ont été réalisées sur 18 chiens anesthésiés, à thorax ouvert. Dans la série 1, nous avons évalué la contribution d’oxyde nitrique endogène à la vasodilatation coronarienne pendant une ANH avec du dextran-40 5 % (réduction de 50 % de l’hématocrite). Pour ce faire, nous avons comparé le débit sanguin myocardique (MBF ; microsphères radioactives) dans la région de l’artère interventriculaire antérieure (LAD — left anterior descending), qui a été traitée avec l’inhibiteur de synthase d’oxyde nitrique, le NG-nitro-L-arginine methyl ester (L-NAME), à celle de l’artère auriculoventriculaire (témoin). Dans la série 2, la LAD a été perfusée via un système extracorporel à pression contrôlée avec un débit coronarien (CBF) mesuré à l’aide d’un capteur ultrasonique de débit mesurant le temps de transit. Les augmentations de CBF liées à la dose provoquées par l’acétylcholine (ACh), qui libère de l’oxyde nitrique endogène de l’endothélium vasculaire, et par le nitroprussiate de sodium (SNP), qui fournit de l’oxyde nitrique exogène, ont été comparées avant et pendant l’ANH.Résultats: L’hémodilution normovolémique aiguë a provoqué des augmentations similaires (environ deux fois) de MBF (P<0,01) en l’absence et en présence de L-NAME, et cela n’a pas affecté les augmentations liées à la dose du CBF provoquées par l’ACh et le SNP.Conclusion: Série 1 : dans des conditions de base, l’hémoglobine dans les érythrocytes ne limite pas la vasodilatation coronarienne résultant de la libération tonique d’oxyde nitrique ; l’oxyde nitrique ne joue pas de rôle vasodilatateur durant une ANH. Série 2 : L’ANH n’influence pas les effets vasodilatateurs coronariens de niveaux élevés d’oxyde nitrique, que ce soit en raison d’une libération endogène (ACh) ou d’une perfusion d’un donneur d’oxyde nitrique (SNP).