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Biomedical subjects

G L Hicks

Publications and source records attributed to G L Hicks.

At least 37 records · Page 2Linked to original sources
PubMed1992

Freezing preservation of the mammalian cardiac explant. VI. Effect of thawing rate on functional recovery.

This study investigated the effect of thawing rate on the preservation of frozen isolated rat hearts. The hearts were flushed with a hyperosmotic cardioplegic solution, CP-14/EtOH (1.15 Osm/kg), frozen at a rate of 0.18 degree C/hr for 6 h to -3.2 degrees C. Thereafter, the hearts were thawed at rates ranging from 0.08 to 1.1 degrees C/min for 1 to 14 min until the heart temperature reached -2.1 degrees C, the melting point (MP) of the flush solution; then they were held at -1 degree C for 11 to 24 min so that the total thaw time was 25 min. Post-thaw function was assessed by working reperfusion and expressed as percentage of unstored control function. Cardiac output (CO) and other hemodynamic performance showed biphasic responses to the thaw rate. At 0.08 degree C/min rate, CO recovered to 29.1 +/- 4.1 ml/min (40.8 +/- 5.8% of control). Thawing at 0.13 degree C/min enhanced the recovery of CO to 60.5 +/- 4.9%. Between 0.13 and 0.34 degree C/min, recovery was statistically insignificant. Faster thawing at 0.59 and 1.1 degrees C/min caused progressively less recovery. Overall, 0.13 degree C/min offered the highest recovery. In conclusion, function in slowly frozen heart is intimately affected by the thawing rate; there was an optimal intermediate thawing rate and both too slow and too fast thawing were detrimental.

Animals↗
PubMed1992

Coronary artery bypass graft surgery in older women and men.

OBJECTIVE: To compare women and men younger than 70 years of age and 70 years or older undergoing coronary artery bypass surgery. DESIGN: Retrospective chart review, case-control series. SETTING: University medical center. PATIENTS: All women (n = 465) having first-time isolated coronary artery bypass surgery between 1983 and 1988, and 465 men matched for age and year of surgery. Predominantly white; 33% were 70 years or older. MEASURES: Medical record data: demographics, preoperative comorbidities, perioperative and postoperative complications, mortality, length of stay. RESULTS: Preoperatively, women 70 years of age or older had a higher incidence of congestive heart failure, renal disease and hypertension, and a lower incidence of smoking history compared with women less than 70 years old. Men 70 years or older had a higher incidence of congestive heart failure and renal disease, and a lower incidence of smoking history compared with men less than 70 years old. There was no difference in mortality between older and younger women, whereas the mortality rate for older men was higher than that for younger men. There were fewer differences between women younger than 70 and those 70 years or older in incidence of postoperative complications than between men of those same age groups. Among patients 70 years or older, incidence of postoperative congestive heart failure was greater in women than in men. There were no other differences between women and men younger than 70 and those 70 years or older in incidence of postoperative complications. Controlling for the influence of postoperative complications, age was related to length of stay for women and men. CONCLUSIONS: Older women were at no greater risk of mortality or the occurrence of postoperative complications compared with younger women or older men. A functional component influencing recovery and length of hospital stay needs to be considered to provide optimal nursing care after surgery.

Adult↗
PubMed1992

Homologous blood transfusion as a risk factor for postoperative infection after coronary artery bypass graft operations.

Homologous transfusions are immunosuppressive and associated with a higher risk of postoperative infection. In this retrospective analysis, we studied 238 consecutive patients who underwent first-time coronary operations by a single surgeon in 1988 to 1989 and collected clinical and laboratory data relevant to postoperative infections including pulmonary, urinary, and wound sites. Culture-proved postoperative infections occurred in 16 of the 238 patients (6.7%), with only 3 (1.3%) being deep sternal wound infections. Seven of 16 (44%) of the infections were away from the wound sites, suggesting that nonsurgical variables contributed to at least some infections. Factors significantly associated with an increased risk of postoperative infection by univariate analysis included female sex, diabetes mellitus, and transfusion dose. Infections occurred in 3.9% of patients receiving up to 2 units of red cells and whole blood, 6.9% receiving 3 to 5 units, and 22% of those receiving 6 units or more. Multiple linear and logistic regression analysis showed that transfusion dose was the most significant predictor of infection, days of fever, days of antibiotic therapy, and length of hospital stay. Homologous transfusion is associated (in a dose-dependent fashion) with a threefold to eightfold increased risk of postoperative infection in patients undergoing coronary artery operations. This increased risk of infection may be due to transfusion-induced immunosuppression of the patient.

Aged↗
PubMed1991

Mitral valve replacement in idiopathic hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome is an eosinophil-mediated tissue injury causing multiple organ failure. Cardiac manifestations include subendocardial fibrosis, thrombus leading to peripheral emboli, restrictive cardiomyopathy, and valvar dysfunction. This article describes a patient with the syndrome and reviews surgical experience with valve replacement and long-term prognosis.

Adult↗
PubMed1991

Freezing preservation of adult mammalian heart at high subzero temperatures.

The present study adapted the overwintering strategy employed by freeze-tolerant amphibians and reptiles to freeze-preserve the isolated rat heart. The heart was flushed with a cardioplegic solution and supercooled to -1.2 and -3 degrees C. Then freezing was induced by inoculation of ice crystal. The viability of the heart explant was assessed after reanimation by the isolated working heart perfusion. There was no recovery of function in hearts flushed with solution containing 0.28 mM CaCl2. Lowering the concentration of CaCl2 to 0.15 mM, however, rendered good functional return. Furthermore, inclusion of 50 mM glycerol in the flush solution dramatically improved functional preservation. Under the best conditions defined here, the recoveries of aortic flow, coronary flow, cardiac output, systolic pressure, and work in hearts stored at -1.2 degrees C for 3 h were 72.8 +/- 6.8, 87.2 +/- 4.2, 77.6 +/- 5.4, 83.4 +/- 2.8, and 66.6 +/- 5.9% (mean +/- SEM, n = 8) of the unstored control levels, respectively. The myocardial ice content was 18.6 +/- 5.4% (n = 5) of tissue water. Prolonging the storage time to 5 h increased the ice content to 45.3 +/- 8.1% and reduced the recovery of cardiac output to 23 +/- 11% of the control value (mean +/- SEM, n = 5). Hearts frozen at -3 degrees C for 1.5 h showed 29.4 +/- 8.7% (n = 3) of control cardiac output during reperfusion. This novel approach may provide an opportunity to advance our knowledge about freezing preservation of not only the heart but other solid organs as well.

Animals↗
PubMed1991

Metabolic and functional cardiac impairment after reperfusion with persantine.

The effect of dipyridamole (DYP) on postischemic myocardial function and metabolism was studied using the isolated rabbit heart model. Twenty-one isolated rabbit heart preparations were divided into two groups: KH (control N = 10) were reperfused after 24 min normothermic hyperkalemic arrest with modified Krebs-Henseleit buffer (KH) while DYP (N = 11) were reperfused with KH and 5 X 10(-6) M DYP. Hearts were analyzed for myocardial function (DP, developed pressure, +dp/dt, -dp/dt) and metabolic function (ATP, CrP, ADP, AMP, purines, and lactate levels). Data analysis revealed significant reperfusion depression in DYP myocardial function compared with KH (P less than 0.05): DP (42 +/- 6 vs 89 +/- 7 mm Hg), +dp/dt (390 +/- 21.6 vs 1227 +/- 48.4), and -dp/dt (280 +/- 20.1 vs 677 +/- 19.8). Comparison of DYP to KH metabolic parameters was also significantly different (P less than 0.05): ATP (5.8 +/- 0.7 vs 9.5 +/- 1.4), ADP (2.1 +/- 0.2 vs 3.2 +/- 0.6), CrP (9.6 +/- 0.3 vs 17.2 +/- 1.3). Tissue purines (adenosine and inosine) were significantly elevated (P less than 0.01) in the DYP group, while coronary sinus purines and lactate loss were similar. Thus, the data suggest that DYP, present during postischemic reperfusion, depresses myocardial function by inhibiting adenosine phosphorylation, thereby decreasing the generation of high-energy phosphates without increased substrate loss or ischemia.

Adenosine Triphosphate↗
PubMed1990

Optimal osmolality for cold storage of the cardiac explant.

Cell swelling is a major problem of cardiac preservation. This study evaluated the effect of storage solution osmolality on long-term preservation of cardiac function. Isolated rat hearts were flushed and stored in solutions of 260 to 350 mOsm/kg water at 0 degrees C for 9 hr. Cardiac performance was assessed using the isolated working heart reperfusion. Function of fresh unstored hearts served as the control. The stored hearts had normal heart rate after reperfusion. Other hemodynamic functions recovered to various levels of the control value and showed biphasic responses to solution osmolality. Hearts stored in hyposmotic (260 and 270 mOsm) and hyperosmotic (310, 330, and 350 mOsm) solutions performed poorly. Those stored in 280 to 290 mOsm solutions showed superior recovery in cardiac function. Among all parameters, coronary flow correlated linearly with aortic flow, cardiac output, systolic pressure, work, oxygen consumption, and coronary vascular resistance. Solutions of 280, 290, and 310 mOsm caused 6 to 9% increases in tissue water (TW) over the control hearts during 9 hr storage, whereas 350 mOsm solution maintained TW at the control level. After reperfusion, all stored hearts gained water (25 to 38%) compared to hearts with no reperfusion. Postreperfusion myocardial ATP content was only 70-79% of control level and did not correlate to function recovery. In conclusion, (1) the optimal osmolality of our preservation fluid is 280 to 290 mOsm and moderate or severe hyperosmolality is detrimental to cardiac function, and (2) preservation of coronary function may be crucial to future improvement of storage solution.

Adenine Nucleotides↗
PubMed1988

The Lillehei-Kaster aortic valve prosthesis. Long-term results in 273 patients with 1253 patient-years of follow-up.

The Lillehei-Kaster aortic valve prosthesis was inserted in 313 patients between August 1975 and December 1984. Aortic valve replacement alone was done in 193 patients. Additional procedures included coronary artery bypass grafting in 62 patients, mitral valve replacement in 22, mitral valvuloplasty in 8, and miscellaneous procedures in 28. The 273 patients discharged from the hospital are the basis of this report. They have been followed up for 1253 patient-years. The range of follow-up is 1 to 11 years, and the mean is 4.6 years. The 5-year survival rate for all patients was 68%, whereas for aortic valve replacement alone it was 76%. The incidences of embolism, thrombosis, bleeding, periprosthetic leak, valve infection, and reoperation per 100 patient-years were 1.5, 0.2, 2.0, 0.8, 0.7, and 1.3, respectively. The 5-year rates of freedom from embolism, thrombosis, bleeding, periprosthetic leak, valve infection, reoperation, and any valve-related complication were 94%, 99%, 91%, 96%, 97%, 94%, and 76%, respectively. Four of 16 patients who required reoperation had a properly functioning valve whose effective orifice area was too small for the cardiac output. Each of these valves was of the smaller size. There were no instances of mechanical valve failure. The Lillehei-Kaster aortic valve prosthesis is an excellent aortic valve substitute in the larger sizes. It has an extraordinary record for mechanical durability and an excellent resistance to thromboembolism in patients receiving proper anticoagulation. The incidence of perivalvular leak and infection is similar to that of other prosthetic valves. However, it is not to be recommended in the smaller sizes because of an unfavorable ratio of effective orifice area to tissue diameter.

Adolescent↗
PubMed1987

Verapamil crystalloid cardioplegia: an experimental evaluation of dose-response relationships.

Calcium channel blockers have been advocated as agents which enhance myocardial protection during ischemia and reperfusion. Unfortunately, while cellular integrity is preserved, myocardial function is depressed as a result of the negative inotropic effects of these agents. In order to assess the efficacy of verapamil cardioplegia, 25 isolated perfused rabbit hearts were studied. A model of normothermic ischemic arrest was utilized, employing either verapamil-free crystalloid cardioplegia or cardioplegia containing verapamil in concentrations of 0.5, 1.0, or 5.0 mg/liter. All three verapamil-treated groups demonstrated increased postischemic left ventricular developed pressure and improved postischemic compliance when compared with the untreated group (P less than 0.05). However, myocardial function was significantly depressed at 15 min of reperfusion in the 1.0 and 5.0 mg/liter verapamil-treated groups when compared with the 0.5 ml/liter group (P less than 0.05). These data suggest that the addition of verapamil to crystalloid cardioplegia results in enhanced myocardial function while minimizing the early reperfusion depression associated with higher dose therapy.

Animals↗
PubMed1987

Argon ion laser atheroablation: influence of plaque composition.

This study quantifies the relationship between exposure time, depth of penetration, extent of lateral and deep cellular disruption (LCD and DCD, respectively), and the intrinsic resistance of different grades of atherosclerotic plaque. Argon ion laser atheroablation (AILA) was accomplished via a 200-micro quartz fiber using 2.0 and 5.0 watts of power for standard exposure times in fibrofatty, calcified, and complicated cadaveric human aortic plaque. Gross and histologic analyses revealed the following information: 1. The extent of LCD and DCD increased minimally with longer exposure times, irrespective of plaque grade or laser wattage. 2. At both levels of power, the average rate penetration was slower in calcified than in fibrofatty plaque (p<0.01). 3. Increasingly the laser power increased the rate of penetration per unit of energy. 4. The rate of penetration was quite variable, even among plaques of the same grade, depending on the calcium composition of each sample. In summary, AILA was found to be significantly affected by plaque composition, whereas energy efficiency and accuracy could be maximized by increasing the laser wattage.

Journal Article↗
PubMed1986

Verapamil-potassium cardioplegia: a two-year experience with 470 patients.

This prospective clinical study in cardiac surgery involves a 2-year experience with verapamil-potassium cardioplegia in 470 patients. Protective benefits, associated with calcium channel blockers during cellular ischemia, have increased their utilization in cardioplegic solutions during open-heart surgery. Analysis of the group includes preoperative, intraoperative, and postoperative variables. Preoperative data encompasses age, previous myocardial infarctions, ejection fraction, cardiac index, and risk factors. Analysis of operative data includes the type of operation performed, anesthetic agents, amount of cardioplegia solution, total peripheral resistance, fluid requirements, cross-clamp time and arrhythmias during reperfusion. In this study, verapamil proved to be a safe and effective additive to standard potassium cardioplegia. Beneficial hemodynamic actions with myocardial preservative and antiarrhythmic effects were demonstrated. Although the "perfect solution" to myocardial preservation remains unknown, because of favorable experimental data and successful clinical trials, the continued use of verapamil-potassium cardioplegia appears justified.

Journal Article↗
PubMed1986

Aortic arch dissection with an aberrant right subclavian artery: surgical treatment.

Acute dissection of the aortic arch with an aberrant subclavian artery is a rare finding. This report documents the successful treatment of this unusual problem. A 56-year-old man, brought into the emergency room with severe epigastric, chest, and interscapular pain, was treated medically until stabilized. Operation was then recommended and accepted; whereupon, dissection and control of the arch vessels, including the aberrant right subclavian artery, was accomplished. At follow-up, 3 months after discharge, the patient is active, without pain, and his blood pressure is well controlled.

Journal Article↗
PubMed1985

Platelet inhibitors and hydroxyethyl starch: safe and cost-effective interventions in coronary artery surgery.

This study evaluated the cost-effectiveness and clinical safety of utilizing hetastarch in pump prime solutions and for colloid replacement postoperatively in conjunction with the platelet inhibitors, aspirin and Persantine (dipyridamole). Sixty-four adult patients undergoing a coronary artery bypass operation were divided into two groups. Group 1 (N = 32) received only Persantine (75 mg three times a day) on the day prior to operation. Group 2 (N = 32) received the same Persantine dose plus aspirin (325 mg). In both groups, aspirin and Persantine were continued postoperatively and hetastarch was used as the colloid of choice. All patients were evaluated for blood loss, coagulation profiles, cost of blood and colloid replacement, and clinical course. Group 2 patients demonstrated significantly greater blood loss (p less than 0.05) but the same postoperative coagulation profiles as Group 1. The transfusion requirement (3.6 units versus 1.3 units) and cost basis ($252 versus $91) for patient care were higher in Group 2. Hetastarch had no effect on blood loss and was not associated with any adverse clinical reactions. Annual institutional savings based on utilization of hetastarch were calculated at $33,500 to $40,500 per 500 patients. We conclude that preoperative administration of aspirin (325 mg) is associated with increased perioperative blood loss and higher patient costs, two variables not demonstrable with Persantine only. Use of hetastarch combined with postoperative platelet inhibition was clinically safe and was a cost-effective method of colloid replacement.

Aspirin↗
PubMed1985

Verapamil potassium cardioplegia and cardiac conduction.

This clinical study analyzes the effect of potassium cardioplegic solution containing verapamil hydrochloride (1 mg/L) on cardiac conduction after release of the aortic cross-clamp and throughout recovery. Fifty consecutive patients undergoing open-heart operation were studied as a unit for postoperative conduction abnormalities. They were also analyzed in groups based on spontaneous ventricular conversion to regular rhythm (54%) and the need for single DC cardioversion (32%), or multiple DC cardioversions (14%). Results showed that spontaneous ventricular conversion had no relationship to aortic cross-clamp time and that DC cardioversion using 10 Ws had no detrimental effects on the myocardium or incidence of conduction abnormalities. The need for transient intraoperative pacing was lowest with spontaneous ventricular conversion, but not statistically different from single or multiple DC cardioversions. Only 3 patients (6%) required pacing in the intensive care unit. The incidence of postoperative atrial and ventricular arrhythmias was similar in all groups, and no deaths or episodes of malignant ventricular arrhythmias occurred. This study concludes that verapamil potassium cardioplegia is associated with excellent myocardial protection and a high incidence of transient intraoperative dysfunction of the atrioventricular node (70%) but a low incidence of postoperative pacing. Benign postoperative arrhythmias occur, but at hospital discharge, few conduction abnormalities (10%) persist.

Arrhythmias, Cardiac↗
PubMed1985

Preservation of myocardial function with mannitol reperfusate.

Reperfusion of the globally ischemic myocardium with mannitol has been shown to preserve myocardial function. However, it remains unclear whether the mechanism of mannitol protection relates to its hyperosmolar or free radical scavenging properties. Three groups of isolated, perfused rabbit hearts underwent 45 min of normothermic ischemia without cardioplegia in an experimental paradigm analogous to the clinical situation of coronary artery thrombosis with subsequent reperfusion. Six hearts were reperfused with an isosmolar solution, eight hearts were reperfused with a mannitol-containing solution (20 mOsm/liter), and five hearts were reperfused with a solution containing additional sodium chloride (10 meq/liter, 20 mOsm/liter) to control for the hyperosmotic effects of mannitol. Left ventricular developed pressure, its derivative dP/dt, and diastolic compliance were all significantly improved in the mannitol-reperfused hearts when compared with the hypertonic saline and control groups (p less than .05). There were no intergroup differences in myocardial edema formation, oxygen consumption, or lactate production. These data indicate that mannitol reperfusion offers significant myocardial protection independent of hyperosmolar properties. Free radical scavenging activity appears to be the most credible explanation for these observations, although confirmation of this mechanism awaits further biochemical and cellular investigation.

Animals↗
PubMed1984

Calcium channel blockers: an intraoperative and postoperative trial in women.

This study analyzes the effects of intraoperative and postoperative calcium channel blockers on myocardial protection, postoperative arrhythmias, perioperative infarctions, and survival. Thirty-nine women undergoing consecutive coronary artery bypass operations were placed either in a control group (N = 23), in which standard cold potassium cardioplegia was used, or in a verapamil-nifedipine group (N = 16), in which verapamil (1 mg per liter) was added to the standard cardioplegic solution and nifedipine was instituted postoperatively. The verapamil-nifedipine group showed a significant reduction in postoperative levels of creatine phosphokinase (p less than 0.05). Levels of aspartate aminotransferase were also reduced (74 IU/L) compared with those for the control group (114 IU/L). In the control group, there were 3 early deaths secondary to abrupt ventricular fibrillation, but no patient in the verapamil-nifedipine group died or had serious early ventricular arrhythmias. Late hemodynamic variables were similar in both groups. We conclude that calcium channel blockers enhance myocardial protection during ischemic arrest and may diminish the incidence of fatal early postoperative ventricular arrhythmias in women undergoing coronary revascularization.

Arrhythmias, Cardiac↗