Cardiovascular and respiratory effects of ketamine in the neonatal lamb.

To determine the cardiovascular and respiratory effects of intravenous ketamine in the neonatal lamb we studied six unpremedicated chronic neonatal lamb preparations. Each lamb was anaesthetized with ketamine 15 mg [corrected] X kg-1, allowed to recover and then anaesthetized with ketamine 30 mg [corrected] X kg-1. Mean arterial pressure, mean pulmonary artery pressure, mean left atrial pressure, pulmonary bloodflow, heart rate, respiratory rate and arterial blood gases were measured before and at one, two, four, six, eight and ten minutes after the administration of each dose of ketamine. Pulmonary vascular resistance, systemic vascular resistance and the ratio of pulmonary to systemic vascular resistance were also determined. After the administration of either dose of ketamine, only respiratory rate changed significantly (p less than or equal to 0.05), reaching a maximum after two minutes. This change was not associated with any arterial blood gas abnormalities. We conclude that in the presence of adequate ventilation, ketamine produces no significant cardiovascular effects in neonatal lambs.

Myocardial preservation: effect of venous drainage.

We compared the effect of three methods of venous drainage on myocardial temperature, coronary blood flow as determined with radioactive microspheres, myocardial metabolites (lactate, adenosine triphosphate [ATP], and glycogen), and left ventricular function before, during, and after cardiopulmonary bypass with hypothermic, hyperkalemic cardioplegic arrest. Venous drainage was established in the 6 dogs in Group 1 using a Sarns 51F cavoatrial catheter, in the 7 dogs in Group 2 using two USCI 32F vena caval catheters with tourniquets, and in the 7 dogs in Group 3 using two USCI 32F vena caval catheters without tourniquets. The lowest myocardial temperature was achieved in Group 1 (7.26 degrees +/- 0.45 degrees C compared with 10.45 degrees +/- 0.56 degrees C in Group 2 and 9.78 degrees +/- 0.43 degrees C in Group 3) (p less than 0.001). Myocardial rewarming to 20 degrees C was not significantly different among the groups. Myocardial ATP and lactate levels were similar in all three groups. Myocardial glycogen levels were maintained during ischemia in Group 1 (1,010 +/- 76 mg/dl compared with 686 +/- 39 mg/dl in Group 2) (p less than 0.005). Myocardial blood flow was similar in all groups during the preischemic periods, but during reperfusion a markedly decreased flow was seen in all areas of the myocardium in Group 1 compared with Group 2 (p less than 0.004). Left ventricular function, as measured by the maximum rate of rise of left ventricular pressure, stroke work, and pressure/volume curves, was similar in all groups. We interpret the postischemic blood flow data, glycogen levels, and ventricular compliance differences to suggest that the dogs in Group 1 had less ischemia.

Comparison of flow differences among venous cannulas.

1. Double caval cannulas with snares provide maximum venous decompression, especially of the superior vena cava. Decompression of the right side of the heart is passive and in the heart being perfused requires venting of the right atrium by release of tapes or atrial suction. 2. Double caval cannulas without snares provide good and consistent venous and atrial decompression. The ventricle is decompressed well except when the perfused heart is in the circumflex position. 3. A large single cannula (e.g., USCI 40F) can decompress both the venous system and right side of the heart, although venous and atrial drainage are much less efficient when the heart is in the circumflex position. 4. The Sarns 51F cavoatrial cannula decompressed the venous system as efficiently as the double caval cannulas. In fact, decompression of the atrium and ventricle were consistently much better with the cavoatrial cannula than with any of the other methods. 5. Efficient venous and myocardial decompression using the 51F cavoatrial cannula requires the atrial drainage ports to be positioned in the upper middle section of the atrium. Clinically, the cannula position is correct when both the single and double marking bands on the cannula are outside the atrium.

Effect of venting on myocardial protection by hypothermic cardioplegic arrest.

UNLABELLED: Myocardial rewarming between cardioplegic (CP) infusions is in part attributable to blood circulating through the heart from collateral channels. This experiment was performed to determine if the type of left ventricular (LV) venting affects myocardial temperature (temp) or alters myocardial protection. Twelve dogs underwent cardiopulmonary bypass (CPB) at 37 degrees C and were subjected to 100 min of cardioplegic arrest by intermittent coronary infusion of 300 ml 0-4 degrees C CP solution. Arterial, central venous, left atrial, and LV pressures; cardiac output; systemic, septal (S), right ventricular (RV), and LV temp; myocardial ATP and glycogen were measured; LV pressure/volume curves and LV dp/dt were calculated. Group A (6 dogs) had an LV vent during CPB, and Group B (6 dogs) had the aorta vented via the CP line. CP infusion lowered LV temp to 8 degrees C in Group A vs 13 degrees C in Group B (P less than 0.000002); S temp was lowered to 7 degrees C in Group A vs 11 C in Group B (P less than 0.00007); and RV temp was lowered to 16 degrees C in Groups A and B. Ten minutes after CP, LV and S temp increased to 20-21 degrees C in Groups A and B, and RV temp to 24-25 degrees C in Groups A and B. Twenty minutes after CP all temperatures were the same. Hemodynamics and myocardial metabolic studies were similar in the two groups. CONCLUSIONS: Hearts vented via the LV cooled to a lower temperature vs those vented via the aorta. Venting did not affect myocardial rewarming, myocardial metabolites, or ventricular function.

Comparison of roller pump versus pressurized bag administration of potassium cardioplegic solution.

We sought to determine the relative efficacy of administering cardioplegia by the pressurized bag versus roller pump technique. Fourteen dogs were placed on cardiopulmonary bypass at 30 degrees C and subjected to 2 hours of cardioplegic arrest. Group 1 (7 dogs) was administered cardioplegic solution from a plastic bag under pressure into the ascending aorta every 20 minutes for the 2-hour period, and Group 2 (7 dogs) was given cardioplegia by means of a roller pump. Myocardial temperature decreased in Group 1 to 13.4 degrees C following administration of the cardioplegic solution, and to 13.1 degrees C in Group 2 (not significant). These temperatures were reached in 3.0 minutes in Group 1 and 1.9 minutes in Group 2 (p less than 0.03). Aortic root pressures during cardioplegic infusion were 31 +/- 2 mm Hg in Group 1 versus 46 +/- 2 mm Hg in Group 2 (p less than 0.01). No significant differences between groups were noted in myocardial distribution of cardioplegia, myocardial blood flow or metabolism, or left ventricular hemodynamics. We conclude that both methods of administering cardioplegia lowered myocardial temperature adequately and protected the myocardium for a period of 2 hours in these normal hearts. The roller pump method facilitated faster cooling and produced significantly higher aortic perfusion pressures, however, which may be important in hearts with coronary stenosis.

Does lower systemic temperature enhance cardioplegic myocardial protection?

This study was performed to determine if systemic temperature affects the rate of cooling and rewarming of the myocardium between infusions of cold potassium cardioplegic solution and if it alters the degree of myocardial protection. Twenty-one dogs underwent cardiopulmonary bypass and 3 hours of ischemic arrest produced by infusing 0 degrees to 4 degrees C potassium cardioplegic solution every 20 minutes. The animals were perfused at different systemic temperatures--Group A, 23 degrees C; Group B, 30 degrees, C; and Group C, 37 degrees C. Myocardial temperature decreased to 11 degrees C in Groups A and B as compared with 13 degrees C in Group C immediately after infusion of the potassium cardioplegic solution (p < 0.0007). Myocardial temperature increased to 19 degrees, 21 degrees, and 26 degrees C in Groups A, B, and C (p < 0.000005) 20 minutes after infusion. Myocardial adenosine triphosphate (ATP) concentration significantly decreased, from 6.69 to 3.56 mumoles/gm (p < 0.0003) in Group B and from 4.99 to 2.80 (p < 0.005) in Group C at the end of 3 hours of cardioplegic arrest. Myocardial glycogen levels also significantly decreased, from 1.156 to 446 mg% (p < 0.003) in Group B and from 811 to 439 mg% (p < 0.04) in Group C. Myocardial ATP and glycogen did not decrease significantly in Group A during the period of arrest. Myocardial lactate values increased more in Groups B and C during the arrest period than in Group A. 12.6 versus 6.5 mumoles/gm (p < 0.03). Moderate systemic hypothermia, therefore, appears to enhance the myocardial protection of potassium cardioplegia.

Effects of systemic hypothermia on myocardial metabolism and coronary blood flow in the fibrillating heart.

Ventricular fibrillation during normothermic cardiopulmonary bypass is deleterious to the myocardium. This study was undertaken to determine if moderate systemic hypothermia would protect the myocardium during ventricular fibrillation. Fourteen mongrel dogs were subjected to 1 hour, 15 minutes of total cardiopulmonary bypass. Ventricular fibrillation was induced by a continuous electrical alternating current applied at the beginning of bypass and lasting for 1 hour. Six animals were maintained at normothermia (Group I), and eight were cooled to 30 degrees C. for 1 hour (Group II). The hypothermic group (Group II) demonstrated lower myocardial oxygen consumption and metabolism, decreased coronary blood flow, and less myocardial lactate production during ventricular fibrillation than did Group I. It is concluded that hypothermia does offer some protection, although not complete, against the deleterious effects of ventricular fibrillation described previously.

Effects of aortic balloon pumping during cardiopulmonary bypass on myocardial perfusion, metabolism, and contractility.

This study was undertaken to determine if the production of pulsatile flow by the intra-aortic balloon pump during cardiopulmonary bypass has any beneficial effect on coronary flow, regional myocardial flow, myocardial metabolism, and left ventricular function. Thirty-six conditioned dogs were subjected to one hour of total normothermic cardiopulmonary bypass. They were divided into the following five groups: (1) controls, beating heart and femoral inflow; (2) balloon, beating heart, and femoral inflow; (3) balloon, beating heart, and aortic inflow; (4) control, fibrillating heart and femoral inflow; and (5) balloon, fibrillating heart, and femoral inflow. Total coronary flow, left ventricular flow, coronary sinus flow, and the endocardial-to-epicardial flow ratio increased in group 3. This increase in flow may have been in part due to increased resistance to flow in the descending aorta by the balloon. No differences in flow were noted in the other groups, all of which were perfused via the femoral artery. No significant differences in myocardial metabolism or left ventricular contractility could be demonstrated between balloon-treated and control groups in these normal hearts.

Experimental evaluation of reexpansion pulmonary edema.

Reexpansion pulmonary edema following pneumothorax is clinically uncommon but occasionally life threatening. This study documents the functional and anatomical abnormalities that occur when a collapsed lung is reexpanded. Right pneumothorax was created through open tube thoracostomy in 30 goats. The animals were divided into six groups by duration of pneumothorax (24, 48, or 72 hours) and technique of reexpansion (waterseal vs 10 cm H2O suction). Arterial blood gases and alveolar-arterial oxygen tension difference (A-aDO2) were analyzed before pneumothorax and after reexpansion. Each lung was reexpanded for 2 hours, chest roentgenograms were obtained, and both lungs were removed. The left lung served as the control. Both lungs were checked for surfactant activity and pulmonary extravascular water volume (PEWY). Light and electron microscopy were also performed. Anatomical and functional changes were present in the reexpanded lung after relief of pneumothorax. Both increased time of collapse and suction reexpansion tended to correlate with increased PEWV, decreased surfactant and arterial PO2, and increased A-aDO2.

Is a left ventricular vent necessary during cardiopulmonary bypass?

This study evaluated the coronary flow and the internal diameter, pressure, and metabolism of the left ventricle using four different cardiopulmonary bypass techniques. Conditioned dogs underwent a 30-minute stabilizing period on cardiopulmonary bypass with a beating, empty heart (normothermia and a flow of 80 ml/kg/min). They were then fibrillated and subjected to four experiments: Group A (7 dogs)--left ventricular vent, caval tapes open; group B (7 dogs)--left ventricular vent, caval tapes closed; group C (7 dogs)--no vent, caval tapes open; group D (4 dogs)--no vent, caval tapes closed. There was no major difference in any of these variables among Groups A and B (both ventricles vented). Group D (no vent, tapes closed) had significantly increased wall tension, decreased coronary flow, decreased subendocardiac flow, and ischemia. In contrast, Group C dogs (no vent, tapes open) had only a slight increase in left ventricular diameter and pressure, with no change from Group A and B dogs in coronary flow, lactate extraction, hydrogen ion production, or potassium difference. Therefore, venting the fibrillating ventricle, either with or without snaring of the caval tapes, is probably the best method to use during the distal anastomosis in a coronary artery bypass operation. However, if a vent is not used, the caval tapes should be left open to allow complete diversion of the venous blood and decompression of the left ventricle.

Prophylactic antibiotics in the treatment of penetrating chest wounds. A prospective double-blind study.

Considerable controversy exists as to whether or not antibiotics should be administered "prophylactically" to patients with penetrating chest trauma. No prospective study of this problem has been reported. Therefore, 75 patients with isolated, penetrating chest injury were randomized prospectively in a double-blind study. Group A patients (38 patients) were given 300 mg. of clindamycin phosphate every 6 hours, beginning with admission and lasting until 1 day following chest tube removal or for 5 days, whichever was shorter. Group B patients (37 patients) were given a placebo on the same schedule. The patients' hospital course, fever, white blood count, culture data, and roentgenograms were recorded serially. Clindamycin-treated patients had a significantly lower incidence of radiographic pneumonia, less fever, and a lower incidence of positive pleural and wound cultures. They acquired empyema less frequently, required fewer operations, and had a shorter period of hospitalization. Antibiotics may be useful, therefore, as adjunctive therapy in the management of penetrating chest trauma.

Effects of methylprednisolone on coronary blood flow and myocardial metabolism during cardiopulmonary bypass.

Corticosteroids frequently are used during cardiopulmonary bypass (CPB) to enhance total body perfusion and myocardial preservation. The mechanisms by which steroids might provide protection to the myocardium have not been clearly defined, however. Therefore this study was performed to measure the effects of methylprednisolone (M-P) on coronary flow and distribution, and on myocardial metabolism and contractility. Twenty-three dogs underwent 1 hour of total CPB, 80 cc/kg/minute at normothermia with beating hearts. Alternate animals received M-P, 30 mg/kg. Myocardial blood flow (microspheres technique), myocardial tissue lactate and adenosine triphosphate, lactate extraction, coronary sinus flow (CSF), and coronary vascular resistance (CVR) were measured before, during, and 60 minutes after bypass. LV dp/dt and cardiac output (CO) were measured before and after bypass. Total coronary flow was significantly higher in the M-P group after 10 and 30 minutes of bypass (93 vs 56 ml/100 gm/minute, p less than 0.05, and 96 vs 71 ml/100 gm/minute, p less than 0.05). Right ventricular flow was higher in the M-P group at 10 and 30 minutes of bypass (98 vs 66 ml/100 gm/minute, p less than 0.05, and 90 vs 78 ml/100 gm/minute). Left ventricular flow was higher in the M-P group at 10 minutes of bypass (79 vs 52 ml/100 gm/minute, p less than 0.08). Septal flow also was higher in the treated group at 10 minutes of bypass (64 vs 49 ml/100 gm/minute) and at 30 minutes of bypass (92 vs 67 ml/100 gm/minute, p less than 0.05). CVR after 10 minutes of bypass was lower in the steroid group (88 mm Hg/ml/100 gm/minute vs 1.39 in the control group, p less than 0.03). It is concluded that M-P increases coronary blood flow and decreases CVR in the empty beating heart during normothermic CPB without altering myocardial metabolism or contractility.20

Effects of ventricular fibrillation on coronary blood flow and myocardial metabolism.

Ventricular fibrillation is frequently induced during cardiac surgery to quiet the operative field. The reported effects of fibrillation on the myocardium vary considerably. In an attempt to better define these effects, we subjected 28 dogs to one hour of total normothermic bypass. Myocardial blood flow, lactate, adenosine triphosphate (ATP), oxygen consumption, and left ventricular fibrillation was induced in 5 dogs and continuous electrical fibrillation in 7 dogs. These groups were compared to two respective control groups with beating hearts of 8 animals each. Coronary sinus flow, total coronary blood flow, left ventricular flow, myocardial oxygen consumption, and myocardial tissue lactate increased significantly in the fibrillating hearts. Left ventricular dp/dt decreased with fibrillation, but not significantly. It is concluded that the metabolic demands of ventricular fibrillation exceed the increase in coronary blood flow, when compared to demands of the beating heart, and that decreased left ventricular performance may result.

Effects of morphine and halothane anesthesia on coronary blood flow.

This study was undertaken to determine the relative effects of morphine and halothane anesthesia on coronary blood flow. Right heart bypass was instituted in 20 dogs by draining the vena cava blood into a cardiotomy reservoir and returning it to the main pulmonary artery. Coronary sinus drainage was measured by a right ventricular cannula. Group I (10 dogs) was sequentially given 0.5, 1, 1.5, 2.0, and 2.5% halothane. Group II (10 dogs) was given 1, 2, 3, 4, and 5 mg per kilogram of morphine intravenously. Arterial pressure, coronary sinus blood flow, cardiac output, arterial pH, PCO2, and PO2 were determined and repeated at each dose level of anesthesia and compared to the control values. Morphine significantly increased coronary flow at 3, 4, and 5 mg/kg without pressure adjustment and at 2 mg/kg after pressure adjustment. Coronary flow with halothane was unchanged from control values except for a decrease at 2.5%. Coronary flow was significantly greater with 3, 4, and 5 mg/kg of morphine than with 1.0 and 1.5% halothane.

Hemodynamics within a canine femoral arteriovenous fistula.

Blood flow and pressures around a canine femoral arteriovenous fistula, constructed from an autogenous carotid artery, were measured to determine the pressure-flow relationships within the fistula, as well as to determine the presence or absence of retrograde flow in the distal artery and vein. The findings indicate that retrograde arterial flow occurs only when the proximal femoral artery is occluded and, even then, the contribution to fistula flow is small and well below control femoral arterial flow. Retrograde distal venous flow is negligible. Pressure within the fistula is high at the arterial end but is rapidly dissipated across the loop fistula to equal systemic venous pressure on the venous side. Modest distal venous hypertension accompanies this type of fistula. For these reasons, a loop-type, arteriovenous fistula is preferable to other types of fistulas for most clinical surgical indications.