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Biomedical subjects

A S Keats

Publications and source records attributed to A S Keats.

At least 19 recordsLinked to original sources
PubMed1991

Steal-prone coronary anatomy and myocardial ischemia associated with four primary anesthetic agents in humans.

To examine the relationship between myocardial ischemia in patients with steal-prone coronary anatomy and the administration of isoflurane anesthesia, we reviewed coronary angiograms of 955 patients who had participated in a randomized trial of the use of one of four primary anesthetics for coronary artery bypass operations. Steal-prone anatomy was found in 31.8% of patients who had received enflurane; 40.0%, halothane; 32.6%, isoflurane; and 31.7%, sufentanil. Detected by greater than or equal to 0.1 mV ST segment displacement, ischemia during anesthesia occurred in 290 (30.4%) of all patients with no difference in the incidence among the four primary anesthetics (27.5%-32.9%). Patients with steal-prone anatomy did not suffer more ischemia than patients who needed coronary artery bypass surgery but with other varieties of coronary anatomy. In patients with steal-prone coronary anatomy, the incidence of myocardial ischemia by primary anesthetic was 24.0% with enflurane, 34.4% with halothane, 32.1% with isoflurane, and 38.2% with sufentanil. Systolic blood pressure less than 90 mm Hg during anesthesia occurred in 416 (45.6%) patients and was twice as common during administration of volatile anesthetics than during that of sufentanil. Hypotension did not increase ischemia frequency in patients with steal-prone anatomy with use of any of the four primary anesthetics including isoflurane. Ischemia was temporally related to hypotension in only 9 patients (0.9%). In none of the 42 patients who had steal-prone anatomy and hypotension during isoflurane anesthesia was ischemia temporally related to hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics↗
PubMed1991

Benefits of a glucose-containing priming solution for cardiopulmonary bypass.

Benefits from the use of glucose-containing intravenous and priming solutions during coronary artery bypass operation have not been documented, but an increased risk of postoperative neurologic deficit by hyperglycemia has been suggested. To determine benefits, 107 patients undergoing coronary artery bypass operation were managed identically except that one group (n = 54) received 5% dextrose in lactated Ringer's solution (D5LR) as the sole intravenous and priming solution during operation and a second group (n = 53) received the same solution without glucose (LR). During cardiopulmonary bypass, the D5LR group required significantly less additional crystalloid to maintain safe oxygenator levels and flow (1.8 +/- 3.3 vs 15.8 +/- 20.9 mL.kg-1.h-1) and produced more urine (3.5 +/- 3.2 vs 1.2 +/- 1.4 mL.kg-1.h-1). By 24 h after operation, fluid balance in the LR group was approximately 2 L more positive than in the D5LR group. Five days after operation, the D5LR group weighed less than preoperatively (-0.8 +/- 2.6 kg), whereas the LR group gained weight (+1.0 +/- 2.8 kg). We conclude that use of glucose-containing solutions during coronary artery bypass operation benefits patients by decreasing perioperative fluid requirements and postoperative fluid retention. Because embolism is the cause of most postoperative neurologic deficits, any increased risk by hyperglycemia is small.

Blood Glucose↗
PubMed1990

Low activated coagulation time during cardiopulmonary bypass does not increase postoperative bleeding.

The activated coagulation time (ACT) is widely used to monitor adequacy of anticoagulation during cardiopulmonary bypass despite absence of data establishing an ACT below which adverse outcomes occur. For anticoagulation before cardiopulmonary bypass, we administered a single dose of heparin (300 U/kg) to 193 patients and measured ACT and heparin levels at intervals after administration. No additional heparin was administered to any patient. Clot formation in the cardiopulmonary bypass circuit and excessive postoperative chest tube drainage were considered outcomes indicating inadequate anticoagulation. Cardiopulmonary bypass averaged 59 +/- 23 minutes (range, 30 to 138 minutes). Activated coagulation time values at every sampling period were normally distributed. In 51 patients (26.4%) ACT values were less than 400 seconds, including 4 less than 300 seconds, at some sampling time after heparinization. Patients with low ACT values did not bleed more postoperatively than those with high ACT values, nor was bleeding related to heparin level. No clots were found in any perfusion circuit. We conclude that a minimum ACT value for adequacy of heparinization is not yet defined but that it is less than 400 seconds.

Blood Coagulation↗
PubMed1990

Role of perfusion pressure and flow in major organ dysfunction after cardiopulmonary bypass.

The role of perfusion pressure and flow during cardiopulmonary bypass with moderate hypothermia and hemodilution in the development of new postoperative renal or clinically apparent cerebral dysfunction was examined in 504 adults. Cardiopulmonary bypass flow was targeted at greater than 40 mL.kg-1.min-1 and pressure at greater than 50 mm Hg. Flows and pressures less than target occurred in 21.6% and 97.1% of patients, respectively. Fifteen patients (3.0%) suffered new renal and 13 (2.6%) new central nervous system dysfunction. Low pressure or flow during cardiopulmonary bypass, expressed in absolute values or in intensity-duration units, were not predictors of either adverse outcome. Multivariate analysis identified use of postoperative intraaortic balloon counterpulsation (p less than 10(-6], excessive blood loss in the ICU (p less than 10(-4], need for vasopressors before cardiopulmonary bypass (p less than 10(-4], postoperative myocardial infarction (p less than 10(-3], emergency reoperation (p less than 0.002), excessive postoperative transfusion (p less than 0.02), and chronic renal disease (p less than 0.03) as independent predictors of postoperative renal dysfunction. Independent predictors of postoperative central nervous system dysfunction were cardiopulmonary resuscitation in the intensive care unit (p less than 10(-6], intracardiac thrombus or valve calcification (p less than 0.02), and chronic renal disease (p less than 0.03). Age greater than 65 years (40.7% of patients) did not predict either outcome. We conclude that failure of the native circulation during periods other than cardiopulmonary bypass rather than the flows and pressures considered here is the major cause of renal and clinically apparent central nervous system dysfunction after cardiac operations.

Adult↗
PubMed1990

Incidence of perioperative myocardial ischemia detected by different electrocardiographic systems.

To determine the extent to which different electrocardiographic systems account for differences in reported incidence of perioperative myocardial ischemia, the authors simultaneously recorded in 109 patients undergoing coronary artery bypass grafting (CABG) the V5 or modified CM5 lead on five ECG systems by means of a specially constructed common V5 lead. The systems included a Spacelabs Alpha 14 Model Series 3200 ECG Cardule at bandwidths of 0.05-125 Hz and 0.5-30 Hz (a typical operating room monitor), a Marquette Electronics MAC II ECG at 0.05-40 Hz and 0.05-100 Hz (a standard ECG), and a Del Mar Holter recorder at 0.1-100 Hz. Relative ST-segment position and incidence of new ischemia compared to the preoperative ECG were determined in 109 sets of preinduction traces and 877 sets of intraoperative traces. ST-segment position on the three recording systems conforming with the American Heart Association (AHA) low-frequency response recommendations (0.05 Hz) were similar. Compared to the standard ECG, ST-segment position on the Spacelabs at 0.5-30 Hz was consistently more negative. Displacement on the Holter was consistently less negative and less positive. By the 0.1-mV displacement criterion for diagnosis of myocardial ischemia on any one ECG system, 16.5% of patients on arrival and 32.1% of patients intraoperatively suffered new myocardial ischemia. Based on the operating room monitor, arrival and intraoperative ischemia were present in 15.6 and 27.5% of patients, respectively. Ischemia at the same periods was less frequent by the standard ECG system (5.5 and 12.8%, respectively) and least frequent by the Holter recorder (4.6 and 8.3%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1989

Randomized trial of primary anesthetic agents on outcome of coronary artery bypass operations.

To examine the role of primary anesthetic agent on outcome of coronary artery bypass grafting operations, 1,012 patients were prospectively randomized to receive enflurane (257), halothane (253), isoflurane (248), or sufentanil (254). Except for administration of the primary anesthetic, anesthesia management was standardized for all patients. The randomized groups did not differ in demographic characteristics, extent of coronary artery disease, chronic antianginal therapy, hemodynamic characteristics including new myocardial ischemia at arrival to the operating room, and surgical characteristics that might influence the rate of postoperative myocardial infarction or death. From anesthetic induction to start of cardiopulmonary bypass, new ST segment depression appeared in 310 (30.4%) patients and was not different among primary anesthetic groups (28.0-33.5%). Similarly, the incidence of postoperative myocardial infarction (3.6-4.7%) and death (1.2-2.4%) was not different. Although intraoperative hypotension was twice as common in patients receiving any volatile anesthetic and hypertension twice as common with sufentanil, tachycardia (greater than or equal to 110 bpm) was not related to any primary anesthetic (4.3-9.1%) and was the only hemodynamic abnormality significantly related to intraoperative ischemia. The strongest predictor of intraoperative ischemia was ischemia on arrival to the operating room. The authors postulate that approximately 90% of new myocardial ischemia observed during anesthesia is the manifestation of silent ischemia observed in patients before operation and only 10% is related to anesthetic management. They conclude that, despite differences in the hemodynamic consequences of the primary anesthetics studied, none of the primary anesthetics influenced outcome and the primary role of the anesthesiologist in management of these patients is control of heart rate.

Adult↗
PubMed1988

Does chronic treatment with calcium entry blocking drugs reduce perioperative myocardial ischemia?

To examine the role of chronic calcium entry blocking drug administration on perioperative myocardial ischemia and, specifically, the frequency of hemodynamically unrelated ischemia, the authors studied 444 patients undergoing coronary artery bypass operations. Before induction of anesthesia, 119 patients who chronically took calcium entry blocking drugs received nifedipine 20 mg or diltiazem 60 mg orally, 74 received calcium entry and beta adrenergic blocking drugs, 71 received beta blocking drugs only, and 180 received neither. New ischemia occurred in 208 (46.8%) patients; 55 at arrival to the operating room, 86 only after induction, and 67 separately during both periods. Two-thirds of all ischemia was not related to extremes of heart rate or blood pressure; this type was not less frequent in patients receiving calcium entry blocking drugs. Ischemia did occur less frequently in the two patient groups receiving beta adrenergic blocking drugs (34% vs. 53%), a result of less tachycardia both on arrival (3.4% vs. 15.4%) and during anesthesia, when peak heart rate exceeded 109 bpm in only one of 145 beta-blocked patients compared to 29 of 299 not receiving beta blocking drugs. While ischemia appeared during anesthesia in 34.5% of all patients, its incidence was doubled (63%) when heart rate was greater than or equal to 110 bpm. At lower heart rates, the incidence of ischemia did not differ among groups. With respect to all types of ischemia, patients receiving calcium entry blocking drugs only were indistinguishable from those receiving no antianginal therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1988

The overstated risk of preoperative hypokalemia.

To examine the relation between preoperative hypokalemia and frequency of intraoperative arrhythmias, Holter monitoring was employed in 447 patients undergoing major cardiac or vascular operations, the group at greatest risk for life-threatening arrhythmias. Based on serum potassium levels measured immediately before surgery, 57% of patients were normokalemic (greater than or equal to 3.6 mEq/L), 34% hypokalemic (3.1-3.5 mEq/L), and 9% severely hypokalemic (less than or equal to 3.0 mEq/L). No arrhythmia occurred at any time in 63% of patients and minor arrhythmias (premature atrial and occasional premature ventricular contractions) occurred in 16%. Frequent or complex ventricular ectopy appeared before and during operation in 92 patients (21%) but was not related to preoperative potassium level or history of long-term diuretic therapy. Frequent and complex ventricular arrhythmias were more common in patients with a history of long-term digoxin therapy or congestive heart failure. Even among these patients, hypokalemia or diuretic therapy did not increase the incidence or severity of ectopy. These data fail to support the common practice of delaying operation for acute potassium replacement in patients whose preoperative serum potassium is less than normal, even in the presence of cardiovascular disease.

Adult↗
PubMed1987

Venous admixture to radial artery blood samples during cardiopulmonary bypass.

The possibility that venous blood could be withdrawn through a radial artery cannula when venous pressure is high was examined in 30 patients during cardiopulmonary bypass for coronary artery bypass operation. Progressive desaturation of radial artery blood occurred when venous pressure was equal to arterial pressure. Desaturation not only increased with duration of venous obstruction but also occurred immediately if the arterial tree was emptied after occlusion. We believe that these observations result from the transcapillary aspiration of deep venous blood and may produce a potential source of error in measuring arterial oxygen tension during cardiopulmonary resuscitation, cardiac tamponade, and profound right heart failure, as well as cardiopulmonary bypass.

Arm↗
PubMed1986

Addition of papaverine to cardioplegia does not reduce myocardial necrosis.

In a randomized, double-blind prospective study involving 495 patients, we investigated whether the addition of papaverine, 60 mg, to our existing regimen of cold cardioplegia would reduce myocardial necrosis during elective coronary artery bypass operations. Twenty-one (4.2%) patients sustained acute postoperative myocardial infarctions (MI), and 7 (1.4%) died during hospitalization. Neither MI nor death was related to papaverine supplementation. Among 469 patients without postoperative MI, levels of the myocardial-specific isoenzyme of creatine phosphokinase measured 10 hours after aortic cross-clamping were related to ischemic cross-clamp time, but not to papaverine supplementation of cardioplegia. At declamping after completion of distal anastomoses, ventricular fibrillation was more common after cardioplegia without papaverine (32% versus 9%). No other differences between the two groups were found in intraoperative and postoperative hemodynamics, difficulty of weaning from bypass, or postoperative volume requirements. We identified three risk factors for postoperative MI: ECG evidence of new ischemia prior to bypass, unusual technical difficulty with distal anastomoses for the surgeon, and prolonged time of ischemia. We conclude that addition of papaverine to our cardioplegia regimen did not affect outcome or nonspecific myocardial necrosis.

Clinical Trials as Topic↗
PubMed1986

Low ceiling respiratory depression by ciramadol.

Ciramadol, an agonist-antagonist analgesic of lesser milligram potency than morphine, given intravenously at 30 mg/70 kg produced respiratory depression equivalent to that observed with morphine 10 mg/70 kg. Respiratory depression was measured in terms of drug induced displacement of the carbon dioxide response curve of healthy volunteers. In contrast to the progressive respiratory depression by each 10 mg/70 kg increment of morphine, further doses of ciramadol up to 90 mg/70 kg failed to increase respiratory depression. The ceiling of respiratory depression by ciramadol was half the ceiling previously demonstrated for nalbuphine and dezocine. Ceiling respiratory depression may be a general characteristic of agonist-antagonist type analgesics in contrast to pure agonist analgesics.

Benzylamines↗