Biomedical subjects
Publications and source records attributed to G L Hicks.
An eight-year experience (11 patients) with the Knodt rod compression system for sternal reclosure is presented. The system provides a simple, rapid, and safe method for sternal fixation after dehiscence.
This study compares myocardial protection using nonoxygenated clear cardioplegia with oxygen-carrying solutions of blood (PO2, 100 mm Hg) and fluorocarbon (FC-47 perfluorotributylamine, PO2, 500 mm Hg), all containing 25 mEq/L of potassium chloride. Three groups of dogs, each consisting of 5 animals, were placed on cardiopulmonary bypass, and the aorta of each dog was cross-clamped for 45 minutes. Hemodynamic and biochemical variables were measured at baseline and during recovery. Levels of the myocardial isoenzyme of creatine phosphokinase (CPK-MB) in the coronary sinus were significantly lower in the fluorocarbon cardioplegia group at 15 minutes of aortic cross-clamping (p less than 0.01), while both the fluorocarbon and blood cardioplegia groups demonstrated lower CPK-MB levels at 45 minutes (p less than 0.001 and p less than 0.05, respectively), compared with the clear cardioplegia group. The blood and fluorocarbon groups had improved mean aortic blood pressure (p less than 0.02 and p less than 0.05, respectively) and left ventricular pressure. At 45 minutes of reperfusion and recovery, all hemodynamic and enzymatic variables were similar in each group. We conclude that oxygenated solutions better protect the myocardial cell, but that further work is needed to determine the most effective oxygen level for maximum protection with cardioplegia.
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Fifteen adult dogs were equally divided into three groups: group 1 (control) received no medication before or after cardiopulmonary bypass (CPB), group 2 was administered glucose-insulin-potassium (GIK) according to Maroko's protocol before, during, and after CPB, whereas group 3 was treated with methylprednisolone (30 mg/kg) 30 minutes prior to and near the end of CPB. Moderately severe subendocardial hemorrhage was present in 80% of group 1, 50% of group 2, and only 20% of group 3 ventricles. Endocardial viability ratios after CPB were greater than 0.75 in 20% of group 1, 80% of group 2, and 100% of group 3 animals. Both GIK and steroids improved subendocardial perfusion after anoxic arrest and CPB compared with controls. However, steroid-treated dogs exhibited less endocardial hemorrhage, improved contractility, and more rapid return to baseline conditions than either GIK or control animals. These data suggests that steroids could be considered whenever normothermic anoxic cardiac arrest is used for cardiac operations.
Controversy continues about the oxygenator preferable for cardiopulmonary bypass (CPB). This prospective study was undertaken in 52 patients undergoing coronary bypass surgery. Oxygenators were alternated each case between model Q-100, Bentley Laboratories Inc, Irvine, Calif, and Travenol Membrane Oxygenator (TMO), Travenol Laboratories Inc, Deerfield, Ill. The Q-100 group required higher CPB O2 flows, but PO2 levels during CPB were similar for both groups. Heparin sodium dosage and activated clotting, bleeding, prothrombin, and partial thromboplastin times were identical in both groups. Blood loss and platelet reduction after CPB were also similar. Postoperative complications in the Q-100 group included one myocardial infarction, and one neurological problem. The TMO group had no myocardial infarction and one neurological problem. The membrane oxygenator took nine minutes longer to set up and was $63 more expensive to purchase. Blood trauma during CPB was less with the membrane oxygenator (lower plasma hemoglobin level), but we conclude that both oxygenators performing adequately during clinical use in open heart surgery.
Intraluminal wire reinforcement of symptomatic aortic aneurysms in extremely poor risk patients was performed. Hospital mortality was 12.5% with actuarial survival of 74 and 33% at one and five years, respectively. There was improved survival and decreased incidence of rupture compared with untreated patients. Thus, aneurysm wiring is a feasible alternative in treating poor risk patients with extensive aortic disease.
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Midmyocardial and subendocardial pH monitoring was used as an indirect method for continuous evaluation of regional canine myocardial ischemia. Left ventricular midmyocardial pH (pHm) at 4 mm. depth was monitored in 10 dogs, under resting conditions, by means of a 5 mm. Beckman pH probe. pHm was 6.96 +/- 0.03, recorded at myocardial temperatures of 35 to 37 degrees C. Ischemia was then produced by snare occlusion of the proximal left main coronary artery for 2 minutes. pHm decreased to 6.87 +/- 0.03 (p less than 0.01) at 1 minute and 6.80 +/- 0.04 (p less than 0.005) in 2 minutes. When flow was restored, pHm returned toward normal within 2 minutes (pH 6.86 +/- 0.03) and at 5 minutes had returned to control values (pH 6.93 +/- 0.03). In another 5 dogs under similar conditions, pHm at 4 mm. and subendocardial pH (pHe at 8 mm.) were measured. Baseline pHm (6.97 +/- 0.01) and pHe (6.84 +/- 0.02) levels were significantly different (p less than 0.0005). After 2 minutes of ischemia, pHm was 6.82 +/- 0.03, whereas pHe decreased to 6.78 +/- 0.04 (p less than 0.1). Five minutes after snare release, pHe remained at 6.73 +/- 0.07; pHm (6.93 +/- 0.03) returned to control values. Both pHm (6.93 +/- 0.02) and pHe (6.84 +/- 0.09) levels were normal 15 minutes after release of the snare. The midmyocardium and subendocardium have different pH levels which can be monitored. Ischemia produces different pH patterns in these layers. pHm returns to control values within 5 minutes after 2 minutes of ischemia, whereas pHe remains depressed for at least 5 minutes. pH monitoring provides an accurate and simple method for on-line evaluation of endocardial ischemia.
Abdominal aortic aneurysm resections were performed on 298 patients between January, 1966 and December, 1973. The results were compared with 186 resections previously reported between 1955-1965. Hospital mortality rates for elective resections were 13% in 1955-1965, 8.4% in 1966-1973, and 4.2% in the 113 patients treated during the last 3 years. Urgent resections for intact aneurysms, previously associated with a 36% mortality, resulted in a 6% mortality rate in 1966-1973. The emergency resection mortality rate for ruptured aneurysm, originally 69%, was reduced to a present day over-all mortality of 55%, and 42% for the last 3 years. Calculated actuarial survival at 5 years was 65% for urgent (intact), 60% for elective and 40% for emergency (ruptured) groups. Atherosclerosis remains the major deterrent to long-term survival with myocardial infarction and stroke causing 43% of deaths occurring within 5 years. Improved survival appeared secondary to better operative technique, postoperative patient monitoring, increased surgical experience, and more elective resections of smaller, asymptomatic aneurysms than in 1955-1965. With present day low mortality rates, elective resection should be recommended in all patients without significant medical contraindications.
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Isolated rat hearts perfused with hyperosmotic Krebs-Henseleit buffer containing 60 mmol/L NaCl lose 10% of their tissue water. Perfusion of the rat hearts with Krebs-Henseleit buffer containing polyethylene glycol 8000 caused a concentration-dependent reduction in tissue water. In a study of the effect of different cryoprotectants on cardiac preservation, isolated rat hearts were flushed with a cardioplegic solution (CP-14), or CP-14 with either 50 mmol/L glycerol (CP-15), or 5% polyethylene glycol (CP-16) and frozen at -1.4 degrees C for 5 hours. Thawed hearts were reperfused in working mode to assess function. There was no recovery in CP-14 hearts. Hearts treated with CP-15 recovered 39.3% +/- 2.9% (mean +/- SEM) of control cardiac output. CP-16 boosted the recovery of cardiac output to 54.4% +/- 5.7% (p less than 0.05 vs CP-15). Glycerol significantly reduced tissue ice content; PEG further decreased the ice content to 31.7% +/- 0.6%, which was distinctively lower than that in CP-14 (44.7% +/- 1.1%) and in CP-15 hearts (34.6% +/- 1.1%). Tissue water content of CP-14 and CP-15 hearts was similar (3.83 and 3.87 gm H2O/gm dry weight). Polyethylene glycol reduced the tissue water content to 3.24 +/- 0.04 gm H2O/gm dry (p less than 0.01 vs CP-14 and CP-15 by ANOVA). Thus both glycerol and polyethylene glycol offered cryoprotection to the heart explant by reducing tissue ice formation. Polyethylene glycol was superior to glycerol by dehydrating myocardial tissue and further minimizing freezing damage.
This study compared the capabilities of 4 storage solutions in protecting the cardiac explant. Isolated rat heart was flushed with and stored in one of the storage solutions at 0 degrees C for 7 hours. The recovery of function was assessed using the working heart perfusion. Cardiac output returned to 34 +/- 6, 59 +/- 3 76 +/- 5, and 75 +/- 8% (mean +/- SE) of the control level in hearts stored in Euro-Collins, St. Thomas' Hospital cardioplegic, a modified University of Wisconsin (MUW) solutions, and a solution developed by us (CP-8), respectively. Therefore, MUW and CP-8 were superior to the other two solutions. During post-storage reperfusion, the coronary flow correlated directly with the aortic flow (r = 0.98), suggesting that preservation of coronary perfusion may be crucial to the recovery of function. There was also a good correlation between myocardial ATP levels and the cardiac output (r = 0.81). Thus, measurements towards the enhancement of ATP preservation and regeneration may be beneficial to the stored cardiac explant.
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The purpose of this study was to investigate the effects of a personal control intervention in the form of self-administered versus nurse-administered pain medication after cardiac surgery, and its interaction with patients' desire for control, patients' perception of pain intensity, disruption in daily activities, emotional responses, and use of pain medication over time. Subjects were 64 adults undergoing coronary artery bypass or valve replacement surgery. Instruments included the Krantz Health Opinion Survey; a 7-point measure of discomfort scale to assess pain intensity, disruption in daily activities due to pain, and emotional upset due to pain; a shortened form of the Sickness Impact Profile; and the Bi-polar Profile of Mood States. No main effects were found between experimental and control groups on any of the dependent measures nor were interaction effects found between individuals' measured desire for control and the personal control intervention. A time by group interaction was found in reports of pain intensity, p less than .05, with subjects in the experimental group reporting higher levels of pain intensity than subjects in the control group in the early postoperative period.
A patient is presented in whom endotracheal intubation was impossible secondary to an obstructing substernal goiter and laryngeal spasm. Cardiopulmonary bypass was utilized to provide safe induction of anesthesia and intubation so that the substernal goiter could be removed. Other alternative methods in anesthetic management are discussed.