Sallie J. Teasdale

Pulmonary atelectasis and other respiratory complications after cardiopulmonary bypass and investigation of aetiological factors

SummaryRadiological evidence of pulmonary complications and possible aetiological factors were investigated in 50 consecutive patients after heart operations with cardiopulmonary bypass.Atelectasis was the most frequent pulmonary complication except for small pleural effusions, with an incidence of 64 per cent. Several types of atelectasis frequently co-existed, with a predominance of the less extensive plate and sub-segmental forms. The incidence of atelectasis was the same on each side and the site of atelectasis was basal in three quarters of the patients.Preoperative clinical and catheter data were unrelated to the incidence of atelectasis.There was a significant positive correlation between a short cardiopulmonary bypass time and plate atelectasis, between a large fluid load after bypass and segmental atelectasis, between re-operation for bleeding and subsegmentai atelectasis and between post-operative gastric dilation and atelectasis.The type of operation, the use of the intra-aortic balloon and the length of postoperative respiratory ventilation were unrelated to the incidence of atelectasis.The mechanism of development of atelectasis is discussed.RésuméLes manifestations radiologiques des complications respiratoires après chirurgie à coeur ouvert, ainsi que les facteurs étiologiques possibles de ces complications, ont fait l’objet d’ une étude chez 50 malades consécutifs.L’atélectasie s’est avérée la complication la plus fréquente (après les petites effusions pleurales) avec une incidence de 64 pourcent. Plusieurs types d’atélectasie ont fréquemment été observés en même temps chez un même individu. Les formes les moins importantes (atélectasie discoïde et atélectasie sous-segmentaire) ont été rencontrées les plus souvent. L’atélectasie se retrouvait le plus souvent aux bases (¾ des cas) et elle se situait aussi fréquemment à droite qu’à gauche. On retrouvait plus souvent la forme discoïde d’atélectasie chez les malades ayant eu des circulations extracorporelles de courte durée; il y avait corrélation significative entre la forme segmentaire et une balance liquidienne positive importante en fin de C.E.C., entre l’atélectasie de type sous-segmentaire et les interventions pour contrôle d’hémostase; il y avait de même corrélation significative entre l’incidence d’atélectasie et la présence de dilatation gastrique.Par ailleurs, l’on n’a pu établir de corrélation entre l’incidence d’atélectasie et les données cliniques et hémodynamiques pré-opératoires, la durée de C.E.C, ou l’emploi de contrepulsation intra-aortique.Le travail discute du mécanisme de production de l’atélectasie.

Ancrod anticoagulation for cardiopulmonary bypass in heparin-induced thrombocytopenia and thrombosis

Heparin-induced thrombocytopenia and thrombosis was diagnosed in a 50-year-old man undergoing a repeat heart operation after heparinization led to microemboli and an eventual left transmetatarsal amputation. A third heart operation was aborted when anticoagulation with low molecular weight heparin produced intraoperative thrombi. The patient was referred to Toronto where ancrod (Arvin) was used to lower plasma fibrinogen level, allowing successful repair of a ventricular septal defect using cardiopulmonary bypass support. The patient made an uneventful recovery.

Effects of anaesthetic induction on myocardial function and metabolism: a comparison of fentanyl, sufentanil and alfentanil

Anaesthetic induction may induce myocardial ischaemia. A prospective randomized trial was instituted to compare the effect on ventricular function and myocardial metabolism of induction with fentanyl (FEN) or its analogues sufentanil (SUF) or alfentanil (ALF) in 96 patients undergoing elective coronary artery bypass grafting (CABG). Haemodynamic, metabolic (coronary sinus oxygen and lactate extraction) and gated ventrìculo graphic measurements were made awake pre-induction (PRE), after induction (IND) and after intubation (INT). Induction was performed with FEN 75 μg · kg-1 SUF 15 μg · kg-1 or ALF 125 μg · kg-1 and metocurine. Fentanyl induction was associated with the greatest stability of mean arterial pressure (MAP), cardiac performance, and systolic function without associated myocardial lactate production. SUF produced the greatest depression of systolic function (p < 0.05) but without haemodynamic instability or myocardial lactate production in all but one patient. Induction with ALF produced the greatest reduction in MAP (p < 0.05) associated with the greatest decrease in diastolic compliance (p < 0.05) and 50 per cent incidence of myocardial lactate production (p < 0.05) with no significant change in coronary blood flow or myocardial oxygen consumption.Résuméľinduction de ľanesthésie peut induire de ľischémie myocardique. Une étude prospective randomisée a été conduite afin de comparer ľeffet sur la fonction ventriculaire et le métabolisme myocardique de ľinduction avec le fentanyl (FEN) ou son analogue sufentanil (SUF) ou ľalfentanil(ALF) chez 96 patients devant subir une chirurgie de pontage aorto coronarien élective. Des mesures hémodynamiques, métaboliques (extraction de lactate ďoxyène du sinus coronaire) ainsi que des mesures de la fonction ventriculaire par des méthodes nucléaires étaient faites avant ľinduction (PRE), aprés ľinduction (IND) et après ľintubation (INT). ľinduction était faite avec du fentanyl 75 μg · kg-1, sufentanil 15 μg · kg-1 et fentanil 125 μg · kg-1 associé à la métocurine. ľinduction avec le fentanyl a amené la plus grande stabilité de la pression artérielle moyenne (MAP), la performance cardiaque, et la fonction systolique sans production de lactate par le myocarde. Le sufentanil a produit la plus grande dépression de la fonction systolique (p < 0.05) sans instabilité hémodynamique ou production de lactate par le myocarde chez tous les patients sauf un. ľinduction avec ľalfentanil a produit la plus grande réduction de la pression artérielle moyenne (p < 0.05) associé avec la plus grande diminution de la compliance diastolique (p < 0.05) et 50 pour cent ďincidence de production de lactate par le mvocarde (p < 0.05) sans changement significatif dans le flot sanguin coronarien ou dans la consommation ďoxygène du myocarde.

Anaesthesia and amiodarone

Two recent reports support and one report disputes the existence of dangerous interactions between the new benzofuran antiarrhythmic amiodarone and the anaesthetic state.We have reviewed our experience with 17 anaesthetics administered to 16 patients taking amiodarone. Haemo-dynamics and serum amiodarone levels were evaluated where available. Twelve cases involved cardio-pul-monary bypass; of these, three patients died. There were no deaths in the non-cardio-pulmonary bypass group. The charts of 30 patients with poor left ventricular function, who were not receiving amiodarone but who were undergoing coronary artery bypass surgery, were reviewed to establish a comparison group.Interactions were manifested in three forms: (1) nodal rhythm and/or complete heart block developed in ten of 15 patients (one patient had a preoperative pacemaker inserted for the sick sinus syndrome), (2) poor cardiac output requiring intra-aortic balloon pump augmentation developed in six of 12 cardio-pulmonary bypass patients, or, (3) a state of alpha adrenergic blockade leading to a low systemic vascular resistance despite alpha agonist therapy developed in two of 16 patients.We conclude that dangerous, fatal interactions may occur in patients taking amiodarone who undergo general anaesthesia with cardio-pulmonary bypass. Anaesthesia for non-cardiac surgery may be associated with haemodynamically significant bradyarrhythmias. We recommend aggressive invasive monitoring, including pulmonary artery catheterization and consideration of an atrio-ventricular pacemaker in high risk patients.RésuméDeux rapports récents supportent alors qu’un autre refute l’existence d’interactions dangeureuses entre le nouvel antiarrhythmique benzofuran (amiodarone) et l’anesthésie générale.On a revu notre expérience avec dix sept anesthésies ad-ministrées à 16 patients recevants l’amiodarone. L’état hémodynamique et le taux d’amiodarone sérique ont été évalué lorsque disponible. Une circulation extracorporelle a été utilisé chez douze patients, trois de ceux-là sont morts. Aucun décès n’est survenu chez les patients n’ayant pas subit de circulation extracorporelle.Les interactions médicamenteuses ce sont manifestées sous trois formes: 1) rythme nodal et/ou bloc AV complet chez dix des quinze patients (un patient avait déjà dans la période pré-opératoire un pacemaker installé pour un syndrome d’une maladie du sinus); 2) un débit cardiaque has réquérant un ballon intra-aortique chez six des douze patients qui ont subi une circulation extra-corporelle; ou, 3) un en état de blocage adrénergique alpha démontré par une résistance vasculaire systémique diminuée malgré l’administration de médicament alpha agoniste chez deux des seize patients.On conclut que des intéractions dangereuses et parfois fatales peuvent survenir chez des patients recevant l’amiodarone et devant subir sous anesthésie générate une circulation extracorporelle. L’anesthésie pour chirurgie non cardiaque peut etre associée avec des bradyarrhythmies hémodynamiquement significative. On recommande une surveillance hémodynamique agressive et invasive incluant l’insertion d’un cathéter dans l’artère pulmonaire et la considération d’un pacemaker atrio-ventriculaire chez les patients à risque.

Systolic time interval changes after aorto-coronary bypass

ConclusionPre-operative assessment of PEP/LVET ratio was as reliable as invasively measured ejection fraction in separating patients with normal ventricular performance from those with abnormal indices.Our study demonstrates significant impairment of ventricular performance following aorto-coronary bypass procedures. The duration of this dysfunction is between two and five days following operation and is maximal in the first 48 hours. Meaningful interpretation of systolic time interval changes requires measurement of pre-load and after-load. Changes in these variables account for at least some of the increase in PEP/LVET ratio noted in our study. On the basis of a shortened QS2I these patients are thought to exhibit increased adrenergic activity for the entire period of their hospitalization.RésuméLe rapport PEP/LVET (Pre-Ejection Period/Left Ventricular Ejection Time) se compare favorablement à la mesure de la fraction ď éjection — une technique invasive — lorsque ľon veut déterminer si un malade présente une fonction ventriculaire normale ou anormale.Notre étude a mis en évidence une dysfonction ventriculaire gauche significative après chirurgie aorto-coronarienne. Cette dysfonction dure de deux àcinq jours et elle se manifeste àson maximum au cours des premières 48 heures.Ľinterprétation des changements observés dans la mesure des intervalles systoliques doit être faite à la lumière des modifications de la pré et de la post-charge; leur mesure est donc nécessaire. Les modifications de ces paramètres sont en partie responsables de ľaugmentation du rapport PEP/LVET observé chez nos malades.Le raccourcissement des intervalles systoliques noté chez nos patients est attribuable à ľaugmentation de ľactivité adrénergique, observée tout au long de ľhospitalisation.

Aorto-coronary bypass in a patient with sickle cell trait

SummaryA triple aorto-coronary bypass was performed in a patient with sickle cell trait. Partial exchange transfusion with normal packed erythrocytes was used in preparation of the patient for extracorporeal circulation, hypothermia and cardioplegic arrest.RéSUMéLes auteurs rapportent un cas de pontage aortocoronarian triple chez un patient atteint de drépanocytose latente. De tels patients porteurs du gène hétérozygote de ľanémie falciforme supportent en général bien ľanesthésie et la chirurgie si ľon évite les situations ďacidose, ľhypoxémie, la stase vasculaire et les épisodes hypotensifs. En préparation à la chirurgie, ils ont soumis leur malade à des transfusions ďéchange (six culots) afin ďabaisser son taux ďhémoglobine S. Ľintervention s’est ensuite déroulée sans problème sous circulation extra-corporelle avec une hypothermie à 27° C et emploi de cardioplégie.

Functional and Metabolic Effects of Anoxic Cardiac Arrest

Abstract Myocardial changes were studied in 12 dogs and 5 patients to determine whether anoxic, normothermic cardiac arrest, a simple, effective adjunct in open-heart surgery, is detrimental to cardiac function. After 30 minutes of aortic occlusion the dogs showed uniform depression of left ventricular function with profound metabolic acidosis and elevation of lactate of the coronary sinus blood. Five patients who had 21 to 45 minutes of anoxic cardioplegia also showed marked respiratory acidosis, elevation of the lactate/pyruvate ratio, and a progressive rise in lactate of the coronary sinus blood. The effects of anoxia on the human heart are comparable to those observed in the dog. We believe that anoxic cardioplegia of 45 minutes is tolerated by patients but that coronary perfusion should be employed after that length of time.

Con: Perioperative continuous monitoring of mixed venous oxygen saturation should not be routine in high-risk cardiac surgery

M OST CLINICIANS accept that invasive hemodynamic monitoring facilitates diagnosis and treatment of complex cardiovascular disorders, and would use a pulmonary artery catheter (PAC) in the management of patients during high-risk cardiac surgery. Perioperative mixed venous oxygen saturation (SSO,) monitoring via a fiberoptic PAC oximeter seems a small additional step to take in these patients, but this step cannot yet be justified. The increasing cost of health care demands the critical evaluation of all new monitoring technologies and places us more and more in the unfamiliar position of an epidemiologist assessing screening techniques. The problem in question should be common and important, with an accepted backup test, and it should have a well-defined transition from a latent to an overt phase, with evidence that early detection will reduce morbidity or mortality. The test should have an acceptable sensitivity and specificity, and the costs of testing must be balanced against competing health care priorities. Just as laboratory screening has in its time been intuitively felt to be a good thing, without need of rigorous proof, there is a similar danger of uncritical acceptance of new patient monitoring technology. The incorporation of continuous SVO, measurement as an option with PAC use has produced interesting physiological insights, and thus has made the transition to “a major advance,” without fulfilling any of the previous criteria. The authors believe that its usefulness is still unproven in any area of patient care, and that anecdotal reports of mishap detection with its use are insufficient reason for its adoption. The problem is that cardiac output (CO), a measurement of total flow, does not reflect adequacy of tissue perfusion. Just as arterial CO, tension is the parameter that determines the adequacy of minute ventilation in relation to metabolic rate, SSO, was considered to be the parameter by which to assess the adequacy of tissue oxygen supply, and thus indirectly the adequacy of CO, in relation to demand. The validity of SSO, monitoring as an indirect correlate of CO is based on certain assumptions, in particular the body’s ability to maintain a constant oxygen consumption (q02) by compensating for decreases in delivery (DO,) through increased 0, extraction. Oxygen consumption equals the product of CO and arteriovenous oxygen difference:

A Comparison of Nitroglycerin and Nitroprusside: II. The Effects of Volume Loading

The treatment of postoperative hypertension with nitroglycerin or nitroprusside reduces cardiac filling, and volume loading is required to maintain hemodynamic and metabolic stability. Postoperative hypertension (mean arterial pressure greater than 95 mm Hg) developed in 33 patients who were randomized to an initial infusion of nitroglycerin or nitroprusside in a crossover trial. Volume loading (a rapid infusion of 250 to 500 ml of colloid to raise the left atrial pressure 2 to 4 mm Hg) was instituted prior to hypertension and again following the crossover trial during the infusion of nitroglycerin (11 patients) and nitroprusside (13 patients). Volume loading increased left ventricular end-diastolic volume index (LVEDVI) as documented by nuclear ventriculography, cardiac index (CI), and left ventricular stroke work index (LVSWI). Although CI was higher (p less than 0.01) with nitroprusside at any level of LVEDVI, myocardial performance (the relation between LVSWI and LVEDVI) was not different. Diastolic compliance (the relation between left atrial pressure and LVEDVI) was increased (p less than 0.01) with nitroglycerin. Myocardial metabolism was assessed by calculating myocardial lactate flux (MVL), the product of myocardial lactate extraction and coronary sinus blood flow by the thermodilution technique. Volume loading increased MVL during nitroglycerin therapy and decreased (p less than 0.01) MVL during nitroprusside therapy. Volume loading restored preload and increased CI with both nitroglycerin and nitroprusside. Only nitroglycerin improved myocardial lactate utilization. Nitroglycerin is the preferred vasodilator when ischemia is suspected after coronary bypass operations.

Postoperative Hypertension: A Comparison of Diltiazem, Nifedipine, and Nitroprusside

In previous studies, the treatment of postoperative hypertension with sodium nitroprusside induced ischemic metabolism without a decrease in coronary sinus blood flow. In contrast, the calcium antagonists diltiazem and nifedipine reduce blood pressure and may improve myocardial metabolism. A prospective randomized trial was performed in 62 patients, in whom hypertension developed (mean arterial pressure greater than 95 mm Hg) after coronary bypass procedures, to compare diltiazem (n = 22), nifedipine (n = 20), and nitroprusside (n = 20). All three agents reduced blood pressure equally (p less than 0.0001, by analysis of variance). Heart rate decreased with diltiazem (p = 0.006) but increased with nifedipine and nitroprusside (p less than 0.05). Left ventricular diastolic function (the relation between left atrial pressure and left ventricular end-diastolic volume) was not changed with the three drugs. Systolic function (the relation between systolic blood pressure and left ventricular end-systolic volume) was depressed with diltiazem (p = 0.05 by analysis of covariance) and nifedipine (p = 0.05) but not with nitroprusside. Myocardial performance (the relation between left ventricular stroke work index and end-diastolic volume) was depressed most by diltiazem (p = 0.001 by analysis of covariance), and to a lesser extent with nifedipine (p = 0.03), but not with nitroprusside. Myocardial lactate flux in response to the stress of atrial pacing decreased with nitroprusside but not with diltiazem or nifedipine (p = 0.03 by analysis of variance). Diltiazem and nifedipine are effective agents for treating postoperative hypertension after coronary artery bypass operations.