Relation of myocardial protection to cardioplegic solution pH: modulation by calcium and magnesium

Beneficial Effects of Aminophylline on Ischemia-Reperfusion in Isolated Rabbit Heart

Eighteen rabbit hearts were arrested for 3 hours with cardioplegic solution at 4°C, followed by reperfusion with oxygenated perfusion solution at 37°C for 2 hours. Six control hearts received no drug during arrest or reperfusion (group 1). Six hearts received 3 mg·L−1 aminophylline during the arrest period (group 2). Six hearts received 3 mg·L−1 aminophylline during the reperfusion period (group 3). Effects of aminophylline were evaluated in terms of the pressure-volume relationship, coronary flow, myocardial oxygen extraction, and lactate release before cardioplegic arrest and after 1 and 2 hours of reperfusion. End-diastolic pressure at constant volume after 2 hours of reperfusion was 19 ± 2.63 mm Hg in group 1, 14 ± 1.7 mm Hg in group 2, and 19 ± 2.55 mm Hg in group 3 (p < 0.05 for group 2 versus groups 1 and 3). End-systolic pressure at constant volume after 2 hours of reperfusion was 81 ± 3.55 mm Hg in group 1, 90 ± 2.95 mm Hg in group 2, and 84 ± 3.47 mm Hg in group 3 (p < 0.05 for group 2 versus groups 1 and 3). Oxygen extraction was significantly higher and release of lactate was significantly lower in group 2 compared to groups 1 and 3. The results indicate that aminophylline administration during cardioplegic arrest improved systolic and diastolic function and had a beneficial effect on metabolic recovery.

Clinical assessment of prolonged myocardial preservation for patients with a severely dilated heart

BACKGROUND

The purpose of this study was to compare the myocardial protective effect of histidine-tryptophan-potassium and glucose-insulin-potassium cardioplegic solutions in patients with a dilated heart (left ventricular diastolic diameter > 55 mm, left ventricular systolic diameter > 45 mm) associated with prolonged cross-clamp time (longer than 200 minutes).

METHODS

We selected 20 patients with dilated hearts due to severe aortic regurgitation. Glucose-insulin-potassium cardioplegia was used in 11 patients and histidine-tryptophan-potassium cardioplegia was used in 9 patients.

RESULTS

After operation, the cardiac index was significantly increased in the histidine-tryptophan-potassium group (p < 0.05). Postoperative percent fractional shortening was 13.4% +/- 3.1% in the glucose-insulin-potassium group and 23.6% +/- 2.6% in the histidine-tryptophan-potassium group (p < 0.05). Creatine kinase levels were significantly lower in the histidine-tryptophan-potassium group than that in the glucose-insulin-potassium group (p < 0.05). The incidence of ventricular arrhythmia (higher than Lown's grade 2) was lower in the histidine-tryptophan-potassium group.

CONCLUSIONS

These data support the superiority of the histidine-tryptophan-potassium method over the glucose-insulin-potassium method for protection of the dilated heart during prolonged ischemia in open heart operations.

Transient reperfusion with acidic solution affects postischemic functional recovery: studies in the isolated working rat heart

This isolated working rat heart study was designed to investigate the effect of duration of reperfusion and degree of acidity of the reperfusate on myocardial protection. The experimental time course was as follows: 20 minutes of perfusion with the heart working, 3 minutes of infusion with the St. Thomas' Hospital cardioplegic solution followed by global ischemia for 33 minutes at 37 degrees C, and 20 minutes of Langendorff reperfusion followed by 20 minutes of working perfusion. During the initial 3 minutes of Langendorff reperfusion, the pH of the reperfusate was changed to 5.6, 6.8, and 7.5 by addition of sodium hydroxide into Krebs-Henseleit nonbicarbonate HEPES buffer. A respiratory acidic reperfusate was used for the initial 0.5, 1, 2, 3, 5, and 15 minutes during reperfusion. The results were as follows: (1) Reperfusion with a mildly acidic solution (i.e., pH 6.8) yielded better recovery than reperfusion with solutions having pH levels of 5.8 or 7.5. (2) Reperfusion for less than 3 minutes with a reperfusate having a pH level of 6.8 provided better recovery, although reperfusion for longer than 3 minutes exacerbated reperfusion injury. In conclusion, the effects of reperfusion with acidic solution were influenced by degree and duration with biphasic response characteristics.

Forty-hour preservation of the rabbit heart: optimal osmolarity, [Mg2+], and pH of a modified UW solution

The University of Wisconsin solution modified with 2,3-butanedione monoxime and calcium experimentally extends the limits of ischemic preservation of the heart. This study evaluates other characteristics of this modified solution that may further enhance preservation: osmolarity, Mg2+ concentration ([Mg2+]), and pH. Rabbit hearts were flushed with the modified University of Wisconsin solution and stored for 40 hours at 4 degrees C. Maximal left ventricular developed pressure (LVDP), left ventricular end-diastolic volume (LVEDV), maximum rate of increase of left ventricular pressure (dP/dt), heart rate, and coronary flow were measured during 60 minutes of isolated crystalloid reperfusion with an isovolumic left ventricular balloon at constant end-diastolic pressure. Creatine kinase release and myocardial adenine nucleotide content were measured at completion of reperfusion. Solution osmolarity was tested at 357, 327, 297, and 277 mOsm/L by reducing K+, Na+, and lactobionate concentrations. [Mg2+] was assessed at 5 and 16 mmol/L. Solution pH was studied at 7.0, 7.4, and 7.8. A control group of hearts was flushed and immediately reperfused to establish baseline function. Hearts stored in either hypertonic (357 mOsm/L) or hypotonic (277 mOsm/L) solutions functioned poorly, reaching 58% and 50% of control LVDP (p < 0.001), 49% (p < 0.01), and 58% (p = not significant) of LVEDV, 56% and 49% of +dP/dt (p < 0.001), respectively, and released substantially more creatine kinase (p < 0.001 versus control).(ABSTRACT TRUNCATED AT 250 WORDS)

New whole blood analyzers and their impact on cardiac and critical care

Miniaturized whole blood biosensors, patient-focused hospitals, and rising expectations of patients and physicians are shifting laboratory diagnostics to the point of care. Expanding transplantation and intensive care are increasing the need for rapid test results. Whole blood analysis improves accuracy, eliminates centrifugation, reduces response time, and conserves blood volume. Several hand-held, and over 20 portable or transportable whole blood instruments are now available. Criteria for instrument evaluation include test menus, point-of-care features, analysis time, on-site performance, and information integration. Whole blood analyzers measure several vital indicators (pO2, pCO2, pH, hematocrit, K+, Ca2+, Na+, Cl-, glucose, and lactate) simultaneously in less than 2 min with less than 200 microliters of whole blood. Other in vitro tests are available (Mg2+, osmolality, CO2 content, urea nitrogen, beta-hydroxybutyrate, hemoglobin, coagulation) or under development (HCO3- phosphorus). Some can be monitored in vivo (O2 saturation, pO2, pCO2, pH, glucose) or ex vivo. The clinical impact is demonstrated by ionized calcium, now established in importance for cardiac and neurologic problems, and ionized magnesium, a promising new measurement. The hybrid laboratory (a composite of conventional clinical laboratory and patient-focused testing), performance maps, and quality paths facilitate implementation of new whole blood analyzers for optimal support of cardiac and critical care, and improved patient outcomes (prospects).