Influence of Gas Composition on Recurrence of Atelectasis after a Reexpansion Maneuver during General Anesthesia

Background: Atelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver.

Methods: A consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2 O. FI sub O2 was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (V with dot A/Q with dot) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique.

Results: In group 1 (FIO2 = 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (V with dot A/Q with dot < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < V with dot A/Q with dot < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2 = 1.0). Comparing the values before and 40 min after recruitment, all parameters of V with dot A/Q with dot were unchanged. In both groups, Crs increased from 57.1/55.0 ml *symbol* cmH2 O sup -1 (group 1/group 2) before to 70.1/67.4 ml *symbol* cmH2 O sup -1 after the recruitment maneuver. Crs showed as low decrease thereafter (40 min after recruitment: 61.4/60.0 ml *symbol* cmH2 O sup -1), with no difference between the two groups.     

An interface to display special physiologic signals on patient monitors

Objective. The objective of this study was to develop an interface to allow special physiologic signals (e.g., in a research setting) to be displayed on the invasive pressure channel of conventional clinical monitors. The interface accepts single-ended high-level signals for display using the pressure channel of patient monitors, which use strain-gauge transducers employing direct current (DC) excitation.Methods. By studying the electronic circuitry common to most clinical invasive pressure measurement systems (Wheatstone bridge, differential input instrumentation amplifier) it was possible to develop an interface to convert high-level single-ended signals into the low-level differential signal needed for input to an invasive pressure channel.Results and Conclusions. The device is useful when it is desired to display signals from special transducers on regular patient monitors. Schematic diagrams and sample results are provided.     

Effects of Nd:YAG laser irradiation on ventricular myocardium in dogs using an artificial sapphire tip contact laser catheter]

To apply Nd:YAG laser irradiation through a new sapphire tip contact laser method to catheter ablation in treatment of tachy-arrhythmias, effects of laser irradiation on ventricular myocardium were investigated in 10 mongrel dogs. Nd:YAG lase (1064nm) discharges were delivered to different sites on the endomyocardium at power of 5, 10, 15, 20 or 25w with duration of 3, 5, or 10 seconds (sec.) respectively in closed beating hearts. Histopathologically, the lesion irradiated was clearly demarcated from the normal myocardium by the construction band necrosis zone. The depth of injured myocardium was less than 2mm with 3 sec. irradiations, with 5 sec. from 1 mm to 4 mm in proportion to power increase, with 10 sec. from 3mm to 8 mm in proportion to the power from 5w to 15w and could not be measured in cases of more than 20w irradiations. Although with every irradiation duration, the depth of injury increased in proportion to the power increase. With the same total energy, a longer time of irradiation produced deeper injury than a shorter time. This method makes it easier to keep the laser positioned to target than bare laser, and is suitable for use in catheter ablation.     

The epidemiology and clinical features of anaphylactic and anaphylactoid reactions in the perioperative period in Japan]

In an attempt to review the Japanese epidemiology of the anaphylactic and/or anaphylactoid reactions in the perioperative period, we investigated 105 cases with clinical features of anaphylactic and/or anaphylactoid reaction, which are reported in the Japanese anesthesiology-related journals from 1952 to 1990. Eighty-nine percent of the cases were reported during the last decade. There were 66 males and 34 females. The majority of the patients were below 60 years of age, and most of the patients were in their teens and fifties. Ninety percent of the patients had no past history of drug-induced allergy nor tendencies of atopy. Ninety-four percent of the patients recovered completely without any sequelae, and 0.95 percent of them recovered with serious complications. Deaths occurred in 4.67% of the patients. Most frequent clinical signs were cardiovascular (91.4%) and cutaneous (84.8%) manifestations. Respiratory, signs appeared in 41% of the patients. Patients are frequently unconscious and covered with drapes, and early signs and symptoms of anaphylaxis can be masked. In 25% of the patients cardiovascular collapse, including cardiac arrest and undetected blood pressure, appeared as the first noticeable sign. Causative drugs were confirmed immunologically in 5.7% of the patients. In other cases, causative drugs were presumed based on clinical course. Causative drugs and presumed causative drugs were varied, including blood and blood products (24 cases), intravenous anesthetics (19 cases), local anesthetics (15 cases), and muscle relaxants (9 cases), which were used generally in the perioperative period.     

Difficult or Impossible Ventilation after Sufentanil-induced Anesthesia Is Caused Primarily by Vocal Cord Closure

Introduction: Opioid-induced rigidity often makes bag-mask ventilation difficult or impossible during induction of anesthesia. Difficult ventilation may result from chest wall rigidity, upper airway closure, or both. This study further defines the contribution of vocal cord closure to this phenomenon.

Methods: With institutional review board approval, 30 patients undergoing elective cardiac surgery participated in the study. Morphine (0.1 mg/kg) and scopolamine (6 micro gram/kg) given intramuscularly provided sedation along with intravenous midazolam as needed. Lidocaine 10% spray provided topical anesthesia of the oropharynx. A fiberoptic bronchoscope positioned in the airway photographed the glottis before induction of anesthesia. A second photograph was obtained after induction with 3 micro gram/kg sufentanil administered during a period of 2 min. A mechanical ventilator provided 10 ml/kg breaths at 10/min via mask and oral airway with jaw thrust. A side-stream spirometer captured objective pulmonary compliance data. Subjective airway compliance was scored. Pancuronium (0.1 mg/kg) provided muscle relaxation. One minute after the muscle relaxant was given, a third photograph was taken and compliance measurements and scores were repeated. Photographs were scored in a random, blinded manner by one investigator. Wilcoxon signed rank tests compared groups, with Bonferroni correction. Differences were considered significant at P <0.05.

Results: Twenty-eight of 30 patients exhibited decreased pulmonary compliance and closed vocal cords after opioid induction. Two patients with neither objective nor subjective changes in pulmonary compliance had open vocal cords after opioid administration. Both subjective and objective compliances increased from severely compromised values after narcotic-induced anesthesia to normal values (P = 0.000002) after patients received a relaxant. Photo scores document open cords before induction, progressing to closed cords after the opioid (P = 0.00002), and opening again after a relaxant was administered (P = 0.00005).     

Nonoperative treatment ofacromioclavicular joint injuries

Nonoperative treatment is generally the choice for Type I and II acromioclavicular (AC) joint injuries. The situation issomewhat more controversial when Type III AC dislocations are considered, particularly with respect to athletes and heavy laborers. A number of recent studies have supported conservative treatment in these groups. There is general consensus as to the need for surgical intervention for Type IV, V, and VI AC injuries. Integral to any form of management, nonoperative or operative, is a rehabilitation program that addresses range of motion, strength, and neuromuscular control. We describe our program, which is divided into four phases: (1) Pain control and immediate protected range of motion and isometric exercises; (2) strengthening exercises using isotonic contractions and proprioceptive neuromuscular facilitation (PNF) exercises; (3) Unrestricted functional participation with the goal of increasing strength, power, endurance, and neuromuscular control; and (4) return to activity with sport specific functional drills. An athlete is ready to return to competitive sports once the following criteria are met: full range of motion (ROM), no pain or tenderness, satisfactory clinical exam, and demonstration of adequate strength on isokinetic testing. The unique considerations in a throwing athlete with an AC injury are also addressed. The primary goal of the nonoperative treatment protocol is to return the athlete to full activities as quickly and as safely as possible.