Jay S. Finch

Acute acid aspiration lung injury in the rat: biphasic pathogenesis.

The Purpose of this stud?/ was to develop a reproducible model of acute acid aspiration-induced lung injury in the rat to explore the pathophysiology of aspiration pneumonitis. A biphasic injury pattern was observed with injury peaks at 1 hr and 4 hr. Histologic studies at 4 hr revealed significant increases in neutrophils in the alveolar interstitial space. These studies suggest that acid aspiration results in a biphasic acute injury. We hypothesize that the first phase results from a direct physiochemical process or is mediated via afferent (capsaicin sensitive) nerves or both. The second phase, occurring 2–3 hr later, is mediated by neutrophils and is consistent with an acute inflammatory response.

Compared effects of selected colloids on extravascular lung water in dogs after oleic acid-induced lung injury and severe hemorrhage

While the hemodynamic effects of hydroxyethyl starch (HES) have been reported, the effect of this material upon extravascular lung water (EVLW) has not been investigated. Twenty mongrel dogs were subjected to both an oleic acid-induced lung injury and a 2-h period of hemorrhagic shock (MAP = 40 mm Hg). After reinfusion of shed blood, 5 dogs in each of 4 groups were given either 0.5 L of lactated Ringers solution or 0.5 L of 5% albumin, 6% dextran 75, or 6% HES. Lactated Ringers solution was then given in sufficient quantity to keep the wedge pressure (WP) at 12–15 mm Hg and Pao2, P(A-a)O2, cardiac index (CI) and oxygen delivery were determined. EVLW was measured by thermal-green dye double-indicator technique with an Edwards Lung Water Computer (American Edwards Laboratories, Santa Ana, CA). Mean baseline EVLW was 6.9 ± 0.3 ml/kg. Mean EVLW rose to 11.5 ± 1.9 ml/kg after oleic acid. One h after reinfusion, EVLW increased to 40.5 ± .4 ml/kg in the dogs given only lactated Ringers solution and to 39.5 ± 1.5 ml/kg in the dextran group. EVLW was 25.5 ± 3 ml/kg in the HES dogs, and 29.5 ± 2 ml/kg in the group given albumin. Differences between albumin and lactated Ringers solution and between the HES and lactated Ringers groups were significant (p < 0.02 and p < 0.05). Measurements of oxygen, ventilation, CI, and oxygen delivery were not significantly different between the albumin and HES subjects.

Helium-oxygen mixtures in airway obstruction due to thyroid carcinoma.

The management of a patient with severe airway obstruction secondary to a thyroid mass is reported. When breathing room air the patient appeared in severe respiratory distress but when inspiring 22 per cent oxygen in helium she reported almost instantaneous relief and there was a marked decrease in respiratory rate, and increase in tidal volume and arterial oxygen tension. This improvement was to be expected because in situations where turbulent flow predominates a decrease in the density of inspired gases will result in an increase inflow rates. Contrary to established dogma a marked improvement was sustained when the patient was breathing 50per cent oxygen in helium. The concentraton of oxygen in helium was adjusted to obtain subjective relief for the patient in conjunction with adequate oxygenation.RésuméLa conduite devant une obstruction des voies aériennes secondaire à une masse thyroidienne est décrite. Quand la patiente respirait de l’air il apparaissait une détresse respiratoire sévère cependant lorsqu’elle inspirait un mélange de 22 pour cent doxygène et helium elle notait presqu’ instantanément un soulagement avec une diminu-tion marquée de la fréquence respiratoire et une augmen-tation de volume courant et de la tension oxygine artérielle. Cette amélioration était prévisible car pour des situations où le flot turbulant prédomine une diminu-tion de la densité des gaz inspirés provoquera une augmentation du flot. Contrairement au dogme dijd établi une amélioration marquée était soutenue lorsque la patiente respirait un melange de 50 pour cent oxygène et helium. La concentration d’oxygène et helium étail ajustée afin d’obtenir un soulagement subjectif et une oxygénation adequate.

Changes in arterial oxygen saturation in cigarette smokers following general anaesthesia

The effect of cigarette smoking on postoperative arterial oxygen saturation was evaluated in 45 adult patients using pulse oximetry. Patients were divided into a smoking group (n = 20) and a non-smoking group (n = 25) based on current smoking habits up until the time of surgery. The two groups were similar with respect to sex, ASA physical status, surgical procedure, duration of anaesthesia, narcotic and anaesthetic use and recovery characteristics. The non-smoking group was, however, significantly (P < 0.05) older than the smoking group. Postoperative oxygen saturation (SaO2) decreased (P < 0.001) during transport of both groups of patients from the Operating Room to the Recovery Room; a decrease which was significantly greater in the smoking group. The severity of hypoxaemia was also significantly greater in the smoking group than in the non-smoking group. This study suggests that cigarette smoking contributes to postoperative arterial oxygen desaturation following general anaesthesia and that supplemental oxygen should be administered to these patients during postoperative transport.RésuméA l’aide d’un saturomètre digital, nous avons évalué l’effet du tabagisme sur la saturation artérielle en oxygène (SaO2) post-opératoire. Vingtcinq fumeurs de cigarette constituaient un groupe tandis que l’autre groupe était composé de vingt non-fumeurs. Les deux groupes étaient comparables quant au sexe, la classe ASA, le type d’intervention, la durée et le type d’anesthésie, les morphiniques utilisés et la récupération en salle de réveil. Toutefois, les non-fumeurs étaient plus agés que les fumeurs (P < 0,05). Chez les deux groupes, la SaO2 diminuait (P < 0,001) pendant le transport entre la salle d’opération et la salle de réveil quoique de façon significativement plus marquée chez les fumeurs. Le degré d’hypoxémie atteint était aussi plus sérieux chez les fumeurs. Il semble donc que la consommation de cigarettes contribue à l’hypoxémie post-opératoire observé après une anesthésie générate et que les fumeurs devraient respirer un mélange enrichi d’oxygène pendant leur transport vers la salle de réveil.

Evaluation of a hands-on workshop as a teaching tool for critical care medicine.

Many medical students have difficulty correlating the principles of cardiorespiratory physiology with the practice of critical care medicine. We developed a workshop to make this transition easier. After a computer- administered preworkshop test, groups of four students intubated a dog, and inserted arterial, peripheral, and pulmonary artery catheters. After baseline cardiorespiratory variables were measured, noncardiogenic pulmonary edema was created by administration of oleic acid via the right atrial port of the pulmonary artery catheter. Measurements were repeated after equilibration and again during the application of 5, 10, and 15 cm H2O of positive end-expiratory pressure. Monitoring techniques and calculation of physiologic variables and their significance were stressed; emphasis was also placed on the interrelationship between respiratory and cardiovascular manipulations. The educational validity of this workshop was confirmed by a significant improvement in the mean score of a post- workshop test over the mean preworkshop test score.

Use of PEEP in acute respiratory distress syndrome in dogs.

This study evaluates the effectiveness of combining mechanical ventilation and 5 cm H2O positive end-expiratory pressure (PEEP) at the onset of adult respiratory distress syndrome (ARDS) in dogs. Five cm H2O PEEP applied at the onset of ARDS in oleic acid injured dogs resulted in a decrease in cardiac output (CO). This decrease was accompanied by beneficial effects including a relatively stable Sao2 and Pao2. Control group dogs (receiving mechanical ventilation only) showed a less dramatic change in CO, but demonstrated a dramatic drop in saturation, compromising oxygen transport to the tissues. Thus, despite decrease in CO experienced by the PEEP group, oxygen extraction at the tissue level remained high.

Changes in Arterial Oxygen Saturation in Cigarette Smokers Following General Anaesthesia

The effect of cigarette smoking on postoperative arterial oxygen saturation was evaluated in 45 adult patients using pulse oximetry. Patients were divided into a smoking group (n = 20) and a non-smoking group (n = 25) based on current smoking habits up until the time of surgery. The two groups were similar with respect to sex, ASA physical status, surgical procedure, duration of anaesthesia, narcotic and anaesthetic use and recovery characteristics. The non-smoking group was, however, significantly (P less than 0.05) older than the smoking group. Postoperative oxygen saturation (SaO2) decreased (P less than 0.001) during transport of both groups of patients from the Operating Room to the Recovery Room; a decrease which was significantly greater in the smoking group. The severity of hypoxaemia was also significantly greater in the smoking group than in the non-smoking group. This study suggests that cigarette smoking contributes to postoperative arterial oxygen desaturation following general anaesthesia and that supplemental oxygen should be administered to these patients during postoperative transport.