Samuel K. Appavu

Canister tip orientation and residual volume have significant impact on the dose of benzocaine delivered by hurricaine® spray

Delivered quantities of 20% benzocaine spray (Hurricaine; Beutlich L.P. Pharmaceuticals, Waukegan, IL) are estimated by counting the number of sprays or the spraying time. Because Hurricaine spray supplies a continuous (albeit nonmetered) stream of benzocaine, neither method addresses delivered dose. We hypothesized that dose per time is a function of canister content and orientation. Thirty full canisters of Hurricaine were placed into three equal orientations (upright, inverted, or horizontal). Extrapolating from a full canister, four different estimates of benzocaine residual volume were determined before spraying out the contents (80%, 60%, 40%, and 20% full). Each canister was then sprayed for 10-s intervals, and the quantity delivered was calculated and compared statistically. Upright canisters 100% full emitted more benzocaine than canisters with residual volume 20% full (190 +/- 10 vs 172 +/- 10 mg/s). Inverted canisters emitted significantly less benzocaine from 100% full to residual volume 20% full (188 +/- 14 vs 70 +/- 10 mg/s). Oriented horizontally, two full canisters emitted <76 mg/s benzocaine, contrasted with the remaining eight in that group (186 +/- 20 mg/s). We conclude that the benzocaine (Hurricaine) sprayed in milligrams per second depends on canister content and orientation. When residual volumes diminish, there is a reduction in spraying volume per time. This diminution occurs progressively from larger to smaller residual volumes with canisters oriented horizontally, inverted, or upright. Arbitrary documentation of spraying time bears no relationship to dose delivered. Perhaps affixing an atomization device to a graduated syringe filled with benzocaine will help increase accuracy and precision in dosing.

SAFETY OF TRIPLE LUMEN CATHETERS IN THE CRITICALLY ILL

The authors performed this prospective study to determine the infection rate of triple lumen catheters (TLC) in their surgical intensive care unit (SICU) patient population. Patients who required a central venous line for the first time while in their SICU were studied. Those with preexisting catheter infections, bacteremias, and TLC reinsertions were excluded. TLC was placed through the internal jugular or the subclavian vein and all peripheral lines were removed. The distal port was used for parenteral nutrition and the other two ports were used for fluids and medications. Dressings were changed daily and blood cultures were obtained through each port of the TLC. At the time of catheter removal, blood, catheter tip, and the subcutaneous tract were cultured. Duration of catheterization was recorded. Eighty-six catheters were studied. The mean duration of catheterization was 6.2 days and the range was two to 23 days. Six of 86 (6.9%) catheter tip cultures were positive and the remaining 80 (93.1%) were negative. Two positive tips (2.3%) had negative blood cultures for two catheter infections (CIs). The remaining four catheters (4.6%) had associated bacteremias for four catheter sepsis (CS). The two catheter infections occurred among catheters indwelling for 10 days or less while the four cases of catheter sepsis occurred among catheters indwelling longer than 10 days. In conclusion, triple lumen catheters can be safely left in place for up to 10 days with minimal risk for bacteremia.

Race to seal secretion leak past endotracheal tube cuff: back to the basics.

www.ccmjournal.org 681 Endotracheal intubation is a life-saving measure in the critically ill patient, yet the presence of an endotracheal tube (ETT) in the airway for more than a few hours may produce many undesirable effects. ETT interferes with normal mucociliary transport and cough reflex (1). Trauma to the larynx has the potential for serious complications. A round ETT with its nonanatomical curvature passing through the pentagonal rima glottidis causes pressure on the posterior aspects of the larynx and the cricoid cartilage. This pressure, distributed over small areas on both arytenoids can be in the hundreds of mm Hg leading to mucosal ischemia, the size of which correlates with the size of the ETT (2). Factors that determine the magnitude of laryngeal injury, which may progress to laryngeal stenosis, include the duration of intubation, the tube material, tube movement, and reintubation (3). Tracheal complications of intubation are even more serious. They include tracheal mucosal injury, cartilage damage, stenosis, and tracheoesophageal fistula. These complications have become less common recently as the result of cuff pressure monitoring and the use of high-volume low-pressure (HVLP) ETT cuffs. However, formation of biofilm on the inner surface of ETT (4) and leakage of pooled infected oropharyngeal secretions past the ETT cuff into the bronchopulmonary areas are major problems. Leakage of infected oropharyngeal secretions across inflated ETT cuff into the distal tracheobroncheal tree is regarded as the major cause of ventilator-associated pneumonia (VAP) (5, 6). Dobrin and Canfield (7) showed in animal experiments that increase in ETT cuff pressure close to systolic blood pressure resulted in a synchronous increase in tracheal mucosal pressure and a decrease in tracheal wall temperature, indicating decreased tracheal blood flow. When the cuff pressure was dropped to zero, the temperature returned to the previous value (7). A cuff pressure between 20 and 30 cm H 2 O will protect the tracheal mucosa from ischemic damage and will generally maintain adequate seal to prevent air leak from mechanical ventilation. Because leakage of infected subglottic secretion is the major cause of VAP, many innovations have been developed to address this problem. They include the following:

Succinylcholine Cannot Relieve an Airway Obstruction Caused by Pharyngeal and Laryngeal Edema

In their case report, Ibarra et al. (1) describe a patient with pharyngeal and laryngeal edema that they attribute to traumatic asphyxia. Although we agree that traumatic asphyxia may change the structural contour of upper airway, we disagree with the authors on three issues. First, the authors elected to induce their patient with class IV Mallampati airway using succinylcholine and thiopental when airway obstruction developed after failed attempts at direct awake laryngoscopy. Although the authors report resolution of airway obstruction and achievement of good ventilation after the administration of IV anesthesia, yet this technique is not at all the best approach for securing an obstructed airway. Succinylcholine cannot relieve an airway obstruction if, indeed, it was caused by pharyngeal and laryngeal edema. If the ventilation and visualization of the larynx were satisfactory after the induction of anesthesia, why did the tracheal intubation attempt fail and immediate cricothyroidotomy become necessary? Second, the report of arterial blood gas result is incorrect. The Henderson-Hasselbalch equation for bicarbonate buffer system may be used to exclude the possibility of an incorrect blood gas report. According to this equation, it is impossible to have a pH, of 7.24, Pace, of 24 mm Hg, and HCO,of 15.8 mEq/L. For the pH, to be 7.24, either the bicarbonate should be lower (9.93 mEq/L), the Pace, should be higher (38.16 mm Hg), or both. Third, the authors fail to explain their rationale for the transfusion of 8 U of packed red blood cells, 8 U of fresh-frozen plasma, 5 U of platelets, and 2 L of lactated Ringer’s solution. A decreasing hemoglobin level (from 10.5 to 8 g/dL) and hypotension do not constitute adequate indication for this massive transfusion of blood products.