Sait Tarhan

EFFECTS OF INCREASED EXPIRATORY PRESSURE ON BLOOD GAS TENSIONS AND PULMONARY SHUNTING DURING THORACOTOMY WITH USE OF THE CARLENS CATHETER

Summary and ConclusionsBlood gases and acid-base status of fourteen patients undergoing thoracic surgery were studied. All patients were intubated with the Carlens catheter. A large degree of pulmonary shunting and corresponding hypoxaemia was often seen during collapse of one lung. Attempts to prevent the mediastinal shift and to reverse atelectasis in the dependent lung with increased expiratory pressure further decreased arterial oxygen tension in most patients. The mechanism involved in this adverse effect is most likely an increase of shunting through the collapsed non-dependent lung. However, effects of decreased cardiac output on these parameters cannot be excluded from the present study.Increased expiratory pressure appears to reverse collapse of air spaces, but its effect on Pao2 was not seen until after release of the pressure. This type of ventilation does not seem to be effective in correcting the hypoxaemia that may accompany the use of the Carlens catheter during thoracic surgery.RésuméOn a étudié les gaz sanguins et ľéquilibre acide-base de 14 malades soumis à la chirurgie thoracique. Tous les malades ont été intubés par le tube Carlens. On a souvent observé durant le collapsus ďun poumon un degré important de “shunt” pulmonaire et ďhypoxémie correspondante. Des tentatives pour préVenir le déplacement médiastinal et pour renverser ľatélectasie dans le poumon contrô1é a ľaide ďune pression expiratoire augmentée a diminué davantage le tension ďoxygène art6riel chez la plupart des malades. Le mécanisme impliqué dans cet effet contraire est probablement une augmentation du “shunt” à travers le poumon collabé. Cependant, ďaprès cette étude, les effets ďun débit cardiaque diminué sur ces paramètres ne peuvent pas être exclus.Une pression expiratoire augmentée semble renverser le collapsus des alvéoles, mais son effet sur la Pao2 n’a été observe qu’après cessation de la pression. Ce genre de ventilation ne semble pas efficace pour corriger ľhypoxémié qui peut accompagner ľemploi du tube Carlens durant la chirurgie thoracique.

Dobutamine for Inotropic Support during Emergence from Cardiopulmonary Bypass

Dobutamine, a recently introduced derivative of dopamine, is reported to retain inotropic properties with less pronounced chronotropic and arrhythmogenic effects than isoproterenol. The drug was evaluated in two doses, 5 μg/kg/min and 10 μg/kg/ min, in two groups of ten patients each, during emergence from cardiopulmonary bypass. A third group of five patients was studied similarly with isoproterenol, 0.02 μg/kg/min. Cardiac index increased 16 and 28 per cent with the two doses of dobutamine, respectively, and 9 per cent with isoproterenol. Heart rate, in contrast, increased 6 and 15 per cent with dobutamine (not significant) and 44 per cent with isoproterenol (significant). Dobutamine seemed to be associated with fewer arrhythmias than isoproterenol. It is concluded that dobutamine, 5–10 μg/kg/min, is suitable for use during emergence from cardiopulmonary bypass and may possess advantages over isoproterenol.

Hemodynamic Effects of Isoflurane and Halothane in Patients with Coronary Artery Disease

In 12 patients undergoing saphenous vein coronary artery bypass operations cardiovascular hemodynamics were studied in the awake state (control) and during anesthesia with isoflurane (inspired concentration, 1.24%, 7 patients) or with halothane (inspired concentration, 0.77%, 5 patients). Isoflurane anesthesia was accompanied by decreases of 19% in the cardiac in- dex (&OV0422;), 19% in mean arterial pressureand 16% in heart rate (HR). Only the change inwas statistically significant. Halothane anesthesia was accompanied by decreases in &OV0422; (28%)(22%), and HR (10%). The changes in &OV0422; andwere significant. HR did not change significantly following the induction of anesthesia with either agent. The decrease inwas similar with both agents, and, in this regard, neither agent was clearly superior for patients with occlusive coronary artery disease.

Principles of thoracic anesthesia.

The authors review fundamentals of respiratory physiology as they relate to surgery and use these principles as a basis to discuss the preanesthetic, anesthetic, and postoperative management of patients undergoing surgery of the chest.

The effect of dead-space rebreathing on postoperative atelectasis.

YPOXEMIA is a common finding after H general anesthesia.’ Shunting resulting from miliary atelectasis may exist in the absence of detectable physical signs or positive roentgenographic chest findings.’.3 After operation, patients often breathe without sighing, and a constant tidal volume has been associated with the development of atelectasis.384 To prevent or reverse the process, periodic hyperinflation of the lungs, accomplished either mechanically or as a response to an increased inspired C02 tension, has been recommended. The addition of an artificial dead space has been the means most often used to increase the inspired concentration of C02 and to produce an increase in tidal volume and minute ventilation. Hyperventilation then, theoretically, should open collapsed alveoli and prevent ate1ectasis.s Nevertheless, reports on the effectiveness of this measure have been inconc l~s ive .3~~~~ In an effort to evaluate the therapeutic usefulness of rebreathing in postoperative patients, we studied the effect of added dead space on tidal volume, minute ventilation, blood gases, and shunting.

Hemodynamic effects of morphine during and early after cardiac operations.

Hemodynamics and blood gases were measured before and 15 minutes after small (10 mg/70 kg) doses of intravenously administered morphine in two groups of patients having open heart surgery. In one group, the study was undertaken after median sternotomy but before perfusion. The other group had been in the intensive care unit for approximately 1 hour. No changes were found in either group in cardiac index, atrial pressures, arterial pressure, or blood gas variables. However, mean systemic vascular resistance decreased from 41.5 to 35.4 after morphine was given post- operatively. Hence, hemodynamically, morphine is a safe drug if given in small doses for pain relief and sedation early after open heart surgery.

Anesthetic aspects of cardiac surgery: a review of clinical management.

The anesthesiologists responsibilities in the care of patients undergoing cardiac surgery extend well beyond the administration of anesthesia. These responsibilities include a knowledge of the pathophysiologic nature of each lesion, the effects of drugs and anesthetic technics on the circulation, and resuscitation and life-support technics. An understanding of the mechanisms underlying cardiac performance, and their alteration by disease states and by drugs, is fundamental.

Whole-body metabolism during and after abdominal surgery

SummaryOxygen, acid-base components, electrolytes, and energy-producing metabolites were measured in arterial and mixed venous blood before, during, and for three days after abdominal operations in 11 patients. A respiratory alkalosis without a metabolic component was present throughout most of the study interval. Predictably, arteriovenous differences were not found for any electrolyte or metabolite. Arterial and venous oxygen tensions were satisfactory throughout anaesthesia, but the postoperative Pao2 indicated considerable persisting atelectasis. Arterial concentrations of non-esterified fatty acids and ketone bodies were increased before anaesthesia and throughout the operation. Blood sugar increased during the operation and remained above normal postoperatively, probably from intravenous solutions. Mean concentrations of immunoreactive insulin remained in the normal range in spite of this increase in blood sugar. Fat metabolism appeared to predominate, and ketosis occurred in the presence of increased blood sugar. Lactate and pyruvate levels increased steadily throughout the operation and decreased postoperatively.Careful maintenance of arterial oxygen tension and of the circulation during and after anaesthesia for general surgery results in little change in acid-base balance and electrolytes. The changes in blood levels of energy-producing metabolites are moderate and usually reverse themselves. Duration of operation or type of surgery had little influence on the variables studied.RésuméAvant ľopération, durant ľopération, et durant trois jours après des opérations abdominales chez onze malades, nous avons mesuré, dans le sang artériel et dans un mélange de sang veineux ľoxygène, ľéquilibre acide-base, les électrolytes et les métabolites énergétiques. Presqu’à toutes les phases de cette étude, nous avons observé une alcalose respiratoire sans participation métabolique. Tel que prévu, nous n’avons pas trouvé de différences artérioveineuses pour aucun des électrolytes ou des métabolites. Les concentrations artérielles ďacides gras non estérifiés et de corps cétogènes étaient augmentées avant ľanesthésie et durant ľopération. Au cours de ľopération, la glycémie a augmenté et, après ľoperation, elle est demeurée au-dessus de la normale, probablement à cause des solutés donnés par voie endoveineuse. Les concentrations moyennes ďinsuline immunoréactive sont demeurées à un niveau normal en dépit de cette hyperglycémie. Le métabolisme des graisses a semblé prédominer et ľacétone est apparue en présence ďhyperglycémie. Les taux de lactate et de pyruvate ont augmenté de façon régulière au cours de ľopération et ils ont diminué dans les suites opératoires.Un soigneux maintien de la tension en oxygène du sang artériel et de la circulation au cours et après ľanesthésie pour la chirurgie générale a été suivi de peu de changements sur ľéquilibre acide-base et sur les électrolytes. Les changements sur le taux des métabolites énergétiques sanguins sont faibles et, ďhabitude, se rétablissent. La durée de ľopération et la sorte de chirurgie n’influencent que très peu les paramètres étudiés.