Robert P. From

Endoscopic Study of Mechanisms of Failure of Endotracheal Tube Advancement into the Trachea during Awake Fiberoptic Orotracheal Intubation

Background: Advancing the endotracheal tube (ETT) over a flexible bronchoscope (FB) during awake fiberoptic orotracheal intubation is often impeded. The goal of this study was to identify the sites and mechanisms that inhibit the passing of the ETT into the trachea. Methods: Forty-five consenting patients underwent a clinically indicated awake fiberoptic orotracheal intubation. After topical anesthesia, nerve block, or both, an awake fiberoptic orotracheal intubation was performed. The placement of the FB and advancement of the ETT over the FB were videotaped using a second nasally inserted FB. An otolaryngologist later reviewed the videotaped data. Results: The right arytenoid or the interarytenoid soft tissues inhibited advancement of the ETT in 42 and 11% of all patients, respectively. In all cases in which the FB was located on the right side of the larynx, failure of ETT advancement almost always occurred at the right arytenoid. Withdrawing the ETT and rotating it 90° counterclockwise resulted in successful intubation on the second, third, and fourth attempts in 26.6, 20, and 0.7% of patients, respectively. Conclusion: The right arytenoid frequently inhibits advancement of the ETT over the FB into the trachea during awake fiberoptic orotracheal intubation. The FB position in the larynx before tube advancement and the orientation of the ETT are relevant factors in failure of advancement of the ETT into the trachea. The authors recommend positioning the FB in the center of the larynx and orienting the bevel of the ETT to face posteriorly during the first attempt at intubation.

Ventilatory frequency influences accuracy of end-tidal CO2 measurements. Analysis of seven capnometers.

An accurate high-frequency response is mandatory when end-tidal CO2 (PETCO2) is monitored during pediatric general anesthesia. The purpose of this study was to assess the accuracy of six infrared-based capnometers and one multiplexed mass spectrometer available at our institution at increasing frequency. Capnometers studied were the Datascope Accucap, Hewlett-Packard 47210A capnometer, Narkomed 3 Capnomed, Novametrix Capnogard model 1250, Perkin-Elmer Advantage, Puritan-Bennett Datex CO2 monitor, and Traverse Medical Monitor model 2200 capnometer. Changes in CO2 concentration were generated by a solenoid valve switching between 100% O2 and 7% CO2 in O2. Frequencies, 8-101 cycles/min were chosen to stimulate a range that might be generated by children during general endotracheal anesthesia. At every rate the displayed PETCO2 was recorded. Differences in displayed PETCO2 from known CO2 ranged from -16.4 to +6.6. At or below frequencies of 31 cycles/min, four capnometers overreported and three underreported PETCO2. At frequencies above 31 cycles/min, six capnometers underreported and one overreported PETCO2. Errors may be clinically significant if they influence ventilator settings for patients.

Effects of alfentanil and lidocaine on the hemodynamic responses to laryngoscopy and tracheal intubation.

This study was undertaken to determine whether lidocaine and/or alfentanil can effectively abolish or attenuate the increase in mean arterial pressure (MAP), heart rate (HR), and rate pressure product (RPP) associated with rapid sequence induction of anesthesia. Sixty patients were randomly divided into four groups. Group 1 received saline 10 ml, group 2 received lidocaine 2 mg/kg, group 3 received alfentanil 15 micrograms/kg, and group 4 received alfentanil 30 micrograms/kg. All patients were induced with sodium thiopental 4 mg/kg and succinylcholine 1.5 mg/kg to facilitate tracheal intubation. The study drug was given after sodium thiopental was administered, and the investigator was blinded to it. Blood pressure (BP) and HR were recorded at the following times: before induction; after induction but before laryngoscopy and intubation; and 1, 3, and 5 minutes after intubation. Alfentanil 15 and 30 micrograms/kg given in rapid sequence fashion with thiopental and succinylcholine effectively blunted the hemodynamic responses to laryngoscopy and tracheal intubation. Lidocaine 2 mg/kg and saline were found to be ineffective in blunting these same responses.

The comparative effects of sevoflurane and methohexital for electroconvulsive therapy

The standard anesthetic agent for electroconvulsive therapy (ECT) has been methohexital. We compared sevoflurane, a short-acting halogenated anesthetic, to methohexital for induction in ECT. Twelve subjects received sevoflurane or methohexital on alternating treatment days. Seizure duration, time to administering ECT, emergence and recovery, as well as several hemodynamic measures were recorded. A total of 69 treatments were analyzed. When sevoflurane was used, seizure durations recorded by observation and by EEG, were shorter by 10 and 23 seconds, respectively. With sevoflurane, seizure duration remained, however, within a clinically acceptable range. Methohexital allowed faster administration of ECT and discharge from the recovery room (3.8 vs. 6.2 minutes and 40.8 vs. 47.0 minutes, respectively). No difference in the post-ECT hemodynamic changes was found between the two treatments. We conclude that, when indicated, sevoflurane could provide a suitable alternative treatment option to methohexital, but some limitations, including shortened seizure duration and potential side effects, should be kept in mind.

Continuous Enteral Feeding and Short Fasting Periods Enhance Perioperative Nutrition in Patients with Burns

Both retrospective and prospective analyses of the effects of various fasting regimens were carried out on the achievement of calculated caloric needs of patients with severe burns. The records of patients who received enteral feedings while undergoing burn debridements were divided into three groups and retrospectively analyzed to determine the effect that duration of fasting had an achievement of caloric needs and on the risks of aspiration. Patients in two other groups were prospectively studied to determine the safety and efficacy of stopping continuous enteral feedings 1 and 4 hours before surgery, respectively. Techniques of airway management and anesthetic induction were left to the discretion of the attending anesthesiologist. In the retrospective analysis, patients in group I, who fasted for 2 hours achieved 28% of their calculated 24-hour caloric goals compared with 11% in those who fasted for 2 to 8 hours (group II) and 6% in those who fasted for more than 8 hours (group III) before surgery (p less than 0.001). In the prospective portion of the study, patients who fasted for 1 hour before anesthesia was induced achieved 30% of their caloric needs, whereas those who fasted for 4 hours achieved 15% of their target nutritional needs (p = 0.0001). No patient had evidence of pulmonary aspiration. We conclude that controlled enteral feedings and shortened preoperative fasting periods can safely enhance nutritional support in patients with burns.

Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

Introduction:Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force. Methods:Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea). Results:Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006. Discussion:The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.

Intubation Biomechanics: Laryngoscope Force and Cervical Spine Motion during Intubation in Cadavers-Cadavers versus Patients, the Effect of Repeated Intubations, and the Effect of Type II Odontoid Fracture on C1-C2 Motion.

Background: The aims of this study are to characterize (1) the cadaver intubation biomechanics, including the effect of repeated intubations, and (2) the relation between intubation force and the motion of an injured cervical segment. Methods: Fourteen cadavers were serially intubated using force-sensing Macintosh and Airtraq laryngoscopes in random order, with simultaneous cervical spine motion recorded with lateral fluoroscopy. Motion of the C1-C2 segment was measured in the intact and injured state (type II odontoid fracture). Injured C1-C2 motion was proportionately corrected for changes in intubation forces that occurred with repeated intubations. Results: Cadaver intubation biomechanics were comparable with those of patients in all parameters other than C2-C5 extension. In cadavers, intubation force (set 2/set 1 force ratio = 0.61; 95% CI, 0.46 to 0.81; P = 0.002) and Oc-C5 extension (set 2 − set 1 difference = −6.1 degrees; 95% CI, −11.4 to −0.9; P = 0.025) decreased with repeated intubations. In cadavers, C1-C2 extension did not differ (1) between intact and injured states; or (2) in the injured state, between laryngoscopes (with and without force correction). With force correction, in the injured state, C1-C2 subluxation was greater with the Airtraq (mean difference 2.8 mm; 95% CI, 0.7 to 4.9 mm; P = 0.004). Conclusions: With limitations, cadavers may be clinically relevant models of intubation biomechanics and cervical spine motion. In the setting of a type II odontoid fracture, C1-C2 motion during intubation with either the Macintosh or the Airtraq does not appear to greatly exceed physiologic values or to have a high likelihood of hyperextension or direct cord compression.

Operating room management: the role of the anesthesiologist.

Operating room management structures and interrelationships both within the operating suite and with other departments in the hospital can be extremely complex. Several different professional and support groups are represented that often have infrastructures of their own that may compete or conflict with the operating rooms management hierarchy. Often, there really is little actual management of the operating suite as an entity. Because the units must interact effectively to provide a high level of patient care, it is important that areas of conflict be resolved. Many problems can be averted by implementation of specific policies and procedures, after appropriate action by the medical staff outlining operating room goals and objectives, and the establishment of realistic lines of authority and communication. More important than the actual structure of the management components in developing an efficient and successful operating room is the ability of key management personnel to understand the dynamics of people and situations as they evolve. Management must also continually monitor and objectively evaluate the system so that areas of deficiency of conflict may be identified and policies or procedures adapted to adequately meet the changing needs of staff and patients. Anesthesiologists are in unique positions to deal with many of these problems and should play an active role in their resolution. As physicians and consultants, we have an understanding of the burden faced by surgeons relative to patient care. Because the majority of our working time is spent in the operating room, we have an opportunity to develop an effective working relationship with nursing staff.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum potassium concentrations following succinylcholine in patients undergoing beta-adrenoceptor blocking therapy

Efflux of serum potassium following succinylcholine was compared in surgical patients undergoing low-dose, long-term beta 1-adrenoceptor or beta 1,2-adrenoceptor blocking therapy and in those receiving neither of these therapies. There were no significant differences in serum potassium concentration prior to, and over a study period of, 2 hours following succinylcholine administration among the three groups of patients.

Heightened awareness of the thrombosis potential of drug-eluting stents may save lives

To the Editor: Head et als [1] well researched review of the paradox associated with the life-saving benefits of the drug-eluting stent (DES) versus the potential complications of the prothrombotic state of surgery is well-timed. In March 2007, we quickly became aware of the particular hazards that may be associated with stopping anticoagulant therapy in a patient with a 21-month-old DES—we do not know the specific brand of DES. The patient, a 64-year-old man scheduled to undergo excision and sentinel node biopsy for melanoma, was instructed to “stop Plavix one week, and aspirin 5 days prior to surgery.” He was “the-first-case-ofthe-day” and surgery was uneventful. In the Second stage Post Anesthesia Recovery Unit our patient complained of nausea and chest pain and exhibited diaphoresis and tachycardia. Electrocardiogram revealed an ST-elevation acute myocardial infarction (STEMI). Emergent coronary angiography showed that his proximal left anterior descending DES was occluded with thrombus. We later determined that the patients original cardiologist had recommended that antiplatelet therapy be continued indefinitely. Neither the surgeon nor we were made aware of this by the patient prior to this surgery. Careful review of the Head et al. article and associated references identifies 7 case reports in which thrombosis occurred in DES following cessation of antiplatelet therapy and surgery [1-4]. Our case was the first of its kind presented at our weekly Morbidity and Mortality conference. In these 8 reports, one patient died and 7 survived (Table 1). On the other hand, we have seen many patients with DES undergo surgery uneventfully, so we can only hypothesize that these cases represent the numerator in an equation whose denominator is currently indeterminable. Since the Food and Drug Adminitration in April of 2003 granted approval for the DES, more than 800,000 stents have been placed through 2005 [5]. This population represents the universe from which the denominator will be determined. We suspect that more events will occur as the population of stented patients grows older and requires additional surgery.