John G. Brock-Utne

Morbid Obesity and Tracheal Intubation

The tracheas of obese patients may be more difficult to intubate than those of normal-weight patients. We studied 100 morbidly obese patients (body mass index >40 kg/m2) to identify which factors complicate direct laryngoscopy and tracheal intubation. Preoperative measurements (height, weight, neck circumference, width of mouth opening, sternomental distance, and thyromental distance) and Mallampati score were recorded. The view during direct laryngoscopy was graded, and the number of attempts at tracheal intubation was recorded. Neither absolute obesity nor body mass index was associated with intubation difficulties. Large neck circumference and high Mallampati score were the only predictors of potential intubation problems. Because in all but one patient the trachea was intubated successfully by direct laryngoscopy, the neck circumference that requires an intervention such as fiberoptic bronchoscopy to establish an airway remains unknown. We conclude that obesity alone is not predictive of tracheal intubation difficulties.

Anesthetic concerns for robot-assisted laparoscopy in an infant.

A 2-mo-old infant with biliary atresia was scheduled for laparoscopic Kasai with robot assistance. Before surgery, a practice trial maneuvering the cumbersome robotic equipment was performed to ensure rapid access to the patient in case of emergency. IV access, tracheal intubation, and arterial line placement followed inhaled anesthesia induction with sevoflurane. Robotic setup took 53 min and severely limited patient access. No adverse events occurred during the procedure requiring the removal of the robotic equipment, and the patient was discharged after a stable postoperative recovery. Advance preparation is required to maximize patient safety during robotic surgery.

The Effect of Cricoid Pressure on Preventing Gastric Insufflation in Infants and Children

BackgroundThe use of cricoid pressure for the possible prevention of regurgitation of gastric contents during Induction of anesthesia in both adults and children has been recommended. However, equally important is the technique in possibly preventing insufflation of gas into the stomach. This study was designed to determine the efficacy of cricoid pressure application in preventing gastric gas insufflation in pediatric patients and to determine the airway pressure at which gas entered the stomach (pop-off point). MethodsFifty-nine patients, 2 weeks to 8 yr of age, physical status 1–4, scheduled for elective surgery, received an inhalational induction of anesthesia with halothane, N2O, and O2. A single observer used a stethoscope to auscultate over the upper abdomen for any air entry. In study I (without paralysis), the proximal airway pressure was slowly Increased by gradually closing the pop-off valve on the anesthesia machine until gas was heard entering the stomach (pop-off point) or until the peak Inspiratory pressure (PIP) reached 40 cm H2O. Thereafter, the pressurization procedure was repeated three times, altering the application and removal of cricoid pressure. The same patients were then paralyzed (study II), and the stomach evacuated before commencing an identical pressurization sequence with and without cricoid pressure. ResultsAppropriately applied cricoid pressure was 100% effective In preventing gas insufflation into the stomach of all children up to 40 cm H2O PIP with and without paralysis. In addition, paralysis significantly decreased the median pop-off point in any given patient. ConclusionsAppropriate application of cricoid pressure prevents gastric gas insufflation during airway management via mask up to 40 cm H2O PIP in infants and children. An additional benefit of cricoid pressure occurs In paralyzed patients in whom gastric insufflation occurs at lower Inflation pressures.

Intracerebral hemorrhage in a primate model: Effect on regional cerebral blood flow ☆

The dynamic changes in regional cerebral blood flow (rCBF), induced by a developing intracerebral hematoma, were studied in eight anesthetized monkeys. Hematomas were generated by allowing femoral arterial blood to enter the caudate nucleus via a stereotactically implanted needle. Intracranial pressure peaked at 51 +/- 8 mmHg at 3 minutes after the ictus, and remained high throughout the 3-hour procedure. Cerebral blood flow was significantly reduced in all brain regions for 1 hour after the ictus. The lowest rCBF values were recorded in the immediate clot penumbra and were below threshold levels for ischemic neuronal damage for 90 minutes after the hemorrhage.

Continuous, Noninvasive, and Localized Microvascular Tissue Oximetry Using Visible Light Spectroscopy

Background: The authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes. Methods: In pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40–96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60–99%), and ischemia (occlusion, compression, ventricular fibrillation). Results: In pigs, normoxic StO2 was 71 ± 4% (mean ± SD), without differences between sites, and decreased during hypoxemia (muscle, 11 ± 6%; P < 0.001) and ischemia (colon, 31 ± 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% ± 4%, 40 subjects; buccal, 77% ± 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at −1.3 ± 0.2%/s and decreased to zero in 3–9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference (Δ < 30% during normoxia or hypoxemia vs. Δ > 35% during ischemia). Conclusions: VLS oximetry provides a continuous, noninvasive, and localized measurement of the StO2, sensitive to hypoxemia, regional, and global ischemia. The reproducible and narrow StO2 normal range for oral/enteric mucosa supports use of this site as an accessible and reliable reference point for the VLS monitoring of systemic flow.

Tourniquet release: Systemic and metabolic effects

The pneumatic tourniquet produces ischemic changes in limbs. The effects of tourniquet release on systemic blood pressure and metabolic parameters were studied in 11 adult patients undergoing total knee replacement under general anesthesia. Mean arterial pressure (MAP) decreased rapidly after the release of the tourniquet, becoming significant at 3 min and remaining significantly depressed up to 15 min post release. Arterial pH, PaO2, PaCO2, lactate acid, and potassium changed significantly after the release, but normalized within 30 min. These results are notably different from a previous study in a similar patient population undergoing knee replacement under epidural anesthesia. Compared to patients under epidural anesthesia, patients receiving general anesthesia with mechanical ventilation are unable to compensate for the metabolic load caused by the tourniquet release, as the latter group are unable to alter their ventilatory rate. In elderly patients with decreased cardio‐pulmonary reserve, this may be of clinical importance.

Asystole, after anesthesia induction with a fentanyl, propofol, and succinylcholine sequence

A 42-yr-old woman with a long-standing history of severe rheumatoid arthritis presented for bilateral foot reconstruction of pronounced degenerative bony changes. A detailed medical history revealed, in addition to severe rheumatoid arthritis involving primarily the joints of the hands and feet, a sporadic gastroesophageal reflux problem manifested by dyspepsia. Her rheumatoid arthritis had been severe enough to warrant chronic corticosteroid therapy, and thus she suffered from mild Cushing’s syndrome. She had successfully tolerated numerous general anesthetics in the past, including two uneventful general anesthetics for orthopedic hand procedures in the 5 mo before this admission. These prior anesthetics had included the administration of fentanyl and succinylcholine without untoward effects. Medications on admission included routine doses of flibuprofen, hydroxychloriquine, misoprostol, nizatidine, metoclopramide, triazolam, and prednisone (5 mg/ day). The patient also received weekly intramuscular injections of methotrexate. She had no known medical allergies or drug intolerances. The patient was found to be a physically active person without evidence of cardiac, respiratory, renal, hepatic, or neurologic symptomatology. Physical examination revealed a pleasant, well-

Is cricoid pressure necessary

SIR — I enjoyed reading Dr Brock-Utne’s recent editorial ‘Is cricoid pressure necessary?’ in which he succinctly summarized several of the well-known polemics related to cricoid pressure (1). However, I was disappointed that he concluded the editorial by recommending that we perpetuate this empirically derived, scientifically unproven and outdated manoeuvre until evidence to the contrary is forthcoming. Instead of ‘Waiting for Godot’, clinicians have wisely turned to their vast experience and up to 50% have abandoned the use of cricoid pressure. In light of the rarity of regurgitation at induction of anaesthesia even in those at greater risk, combined with the problems outlined in the editorial, it is extremely unlikely that this manoeuvre will ever achieve scientific endorsement.

A cost analysis of the laryngeal mask airway for elective surgery in adult outpatients.

Background : Since the introduction of the laryngeal mask airway (LMA) into the United States in 1991, the device has become widely used in anesthesia practice. The purpose of this economic analysis was to use existing data to evaluate the costs of the LMA relative to three other common airway management techniques and to identify the variables that had the greatest effect on cost efficiency. Methods : We evaluated four airway management techniques for healthy adults receiving an isoflurane-nitrous oxide-oxygen anesthetic for elective outpatient surgery : (1) LMA with spontaneous ventilation ; (2) face mask with spontaneous ventilation ; (3) tracheal intubation after succinylcholine with subsequent spontaneous ventilation ; and (4) tracheal intubation after nondepolarizing neuromuscular blockade and controlled ventilation. We analyzed published clinical studies of the LMA and obtained cost data from Stanford University Medical Center. The best available estimates of the independent variables were incorporated into a baseline case. For each airway technique we derived cost equations that excluded costs common to all four techniques. Results : Relative to airway management with an LMA, calculated values for the baseline analysis included additional isoflurane costs for use of a face mask (

Preoperative marijuana inhalation--an airway concern.

0.12/min) and for tracheal intubation with (