Effects of vacuum-assisted closure therapy on inguinal wound edge microvascular blood flow

Vacuum-assisted closure (VAC) therapy has been shown to facilitate wound healing. Data on the mechanisms are scarce, although beneficial effects on blood flow and granulation tissue formation have been presented. In the current study, laser Doppler was used to measure microvascular blood flow to an inguinal wound in pigs during VAC therapy (-50 to -200 mmHg), including consideration of the different tissue types and the distance from the wound edge. VAC treatment induced an increase in microvascular blood flow a few centimeters from the wound edge. The increase in blood flow occurred closer to the wound edge in muscular as compared to subcutaneous tissue (1.5 cm and 3 cm, at -75 mmHg). In the immediate proximity to the wound edge, blood flow was decreased. This hypoperfused zone was increased with decreasing pressure and was especially prominent in subcutaneous as compared to muscular tissue (0-1.9 cm vs. 0-1.0 cm, at -100 mmHg). When VAC therapy was terminated, blood flow increased multifold, which may be due to reactive hyperemia. In conclusion, VAC therapy affects microvascular blood flow to the wound edge and may thereby promote wound healing. A low negative pressure during treatment may be beneficial, especially in soft tissue, to minimize possible ischemic effects. Intermittent VAC therapy may further increase blood flow.

Effects of vacuum-assisted closure on central hemodynamics in a sternotomy wound model

Several authors have reported promising results with vacuum-assisted closure therapy in poststernotomy mediastinitis. The aim of this study was to investigate the hemodynamic outcome following the application of six negative pressures on an open sternotomy wound. Six 70-kg pigs underwent median sternotomy followed by vacuum-assisted closure therapy. Six negative pressures (-50, -75, -100, -125, -150, and -175mmHg) were applied to each pig for 30min each while hemodynamic parameters were measured. An increase in cardiac output was observed at -75mmHg when compared to the other five pressures: -50mmHg (P<0.05; CI 0.12-1.13l/min), -100mmHg (P<0.001; CI 0.34-1.32l/min), -125mmHg (P<0.001; CI 0.51-1.52l/min), -150mmHg (P<0.001; CI 0.50-1.47l/min), and -175mmHg (P<0.05; CI 0.13-1.17l/min). A decrease in systemic vascular resistance was observed at -75mmHg when compared to -125mmHg (P<0.01; CI 108-552dyn.s/cm(5)) and -150mmHg (P<0.01; CI 90-543dyn.s/cm(5)), but not compared to the other pressures. No change (P=ns) was observed in heart frequency, mean arterial pressure or central venous pressure. Our data demonstrates that vacuum-assisted closure therapy of -50 to -175mmHg does not impair the central hemodynamics in a porcine sternotomy model.

Effects of a topical enamel matrix derivative on skin wound healing

Enamel matrix derivative, obtained from developing porcine teeth, is composed mainly of amelogenin proteins and used topically in periodontal surgery for advanced periodontitis to regenerate lost connective tissues. The primary objective of this study was to investigate the effects of enamel matrix derivative on skin wound healing. Secondly, in vitro effects of enamel matrix derivative on dermal fibroblasts and microvascular endothelial cells were examined. Full-thickness, circular 2-cm skin wounds in white 16-week-old rabbits were treated thrice weekly with enamel matrix derivative (30 mg/ml) in the vehicle propylene glycol alginate or with vehicle alone. Enamel matrix derivative treatment increased the amount of granulation tissue and accelerated time to complete epithelialization by 3 days (p < 0.001) compared to vehicle treatment. In cultured fibroblasts, vascular endothelial growth factor levels in conditioned media were increased more than fivefold (p < 0.001) with enamel matrix derivative treatment (0.1mg/ml) over control, measured by specific enzyme-linked immunosorbent assay. Enamel matrix derivative also increased release of matrix metalloproteinase-2 more than threefold from fibroblasts (p < 0.001) and from endothelial cells (p < 0.001). Thus, enamel matrix derivative significantly accelerated wound closure in rabbits, possibly by increasing levels of growth factors and proteinases important for granulation tissue formation and remodeling.

Deep sternal wound infection: a sternal-sparing technique with vacuum-assisted closure therapy

BACKGROUND

Vacuum-assisted closure therapy is a novel treatment employed to aid wound healing in different areas of the body and recently also in sternotomy wounds. Aggressive vacuum-assisted closure treatment of the sternum in postoperative deep wound infection enhances sternal preservation and the rate of possible rewiring.

METHODS

The records of 40 consecutive patients with deep sternal wound infection were reviewed. Sternal bone sparing was achieved by using layers of paraffin gauze (Jelonet; Smith and Nephew Medical, Hull, UK) at the bottom of the wound in order to cover and protect visible parts of the right ventricle, lung tissue, and grafts from the sternal edges. Two separate layers of polyurethane foam (KCI, Copenhagen, Denmark) were placed so as to fit between the sternal edges and subcutaneously. A continuous negative pressure of 125 mm Hg was applied and subsequent revision was made exclusively in nongranulation areas.

RESULTS

There were no deaths during the 90 days of follow-up. Three late deaths unrelated to the infection and three subcutaneous fistulas occurred during the total follow-up period (3 to 41 months). The median duration of the vacuum-assisted closure therapy was 10 days (range, 3 to 34). The series represents a total of 474 days with the vacuum-assisted closure device without serious adverse events.

CONCLUSIONS

In our opinion this modified vacuum-assisted closure therapy is a safe and reproducible option to bridge patients with postoperative deep sternal wound infection to complete healing. Reconstruction of the sternum was achieved in all patients without the use of muscle or omental flap surgery.

Ischemic heart disease induce upregulation of endothelin receptor mRNA in human coronary arteries

Endothelin has been implicated in the pathogenesis of ischemic heart disease and congestive heart failure. The aims were to quantify endothelin type A (ETA) and type B (ETB) receptor mRNA levels in human coronary arteries from patients with ischemic heart disease, congestive heart failure and controls using real-time polymerase chain reaction (real-time PCR). In addition, the suitability of organ culture as a model mimicking endothelin receptor changes in cardiovascular disease was evaluated by in vitro pharmacology and real-time PCR. Endothelin ETA and ETB receptor mRNA levels were significantly higher in arteries from patients with ischemic heart disease (0.23+/-0.04 and 0.35+/-0.06) as compared to congestive heart failure (0.09+/-0.02 and 0.07+/-0.01) and controls (0.08+/-0.02 and 0.08+/-0.01). After organ culture, the endothelin ETB receptor mRNA levels were elevated, and the sarafotoxin 6c-induced vasoconstriction was more efficacious. Increased endothelin receptor activity may contribute to the increased vascular tone and development of atherosclerotic disease in ischemic heart disease in man.

Selective mediastinal tamponade to control coagulopathic bleeding

End-stage congestive heart failure in combination with major cardiac surgery may cause severe postoperative bleeding due to coagulopathy. Bleeding diathesis can be very difficult to control despite careful surgical hemostasis and aggressive medical treatment. We describe a technique that involves the use of negative pressure in the mediastinum to control severe postoperative bleeding after cardiac surgery.

Endothelin receptors in endothelium-denuded human coronary artery bypass grafts and coronary arteries

BACKGROUND

Coronary artery bypass graft (CABG) surgery is hampered by deleterious vasospasm in the vessel wall, especially in vein grafts. Endothelin (ET) is a strong vasoconstrictor that can be observed in increasing concentrations during CABG surgery.

METHODS

Endothelin-induced vasoconstriction was evaluated in isolated, endothelium-denuded vessel segments of the human saphenous vein (SV), left internal mammary artery (LIMA), and coronary arteries. The ET(A) and ET(B) receptor mRNA levels were quantified by real-time polymerase chain reaction (PCR) analysis.

RESULTS

The ET(A) and ET(B) receptor mRNA levels were significantly higher in the SV than in the LIMA and the coronary arteries. ET-1 induced a more efficacious contraction in the SV and LIMA as compared with in the coronary arteries. The ET(B) receptor agonist, Sarafotoxin 6c (S6c) stimulated constriction of the LIMA and SV, while inactive in the coronary arteries. The concentration-response curve for S6c was biphasic, suggesting activation of ET(A) receptors at high concentrations as this response could be inhibited by FR139317 (10 micromol/L), and ET(B) at low concentrations as this response could be inhibited by BQ788 (0.1 micromol/L).

CONCLUSIONS

Endothelin-induced vasoconstriction is mediated by ET(A) receptors alone in coronary arteries, while a combination of ET(A) and ET(B) receptors are of importance in SV and LIMA. Expression of contractile ET(B) receptors may be a pharmacologic disadvantage that contributes to the vasospasm during CABG surgery. The lower levels of ET(A) and ET(B) receptor mRNA in the LIMA and coronary arteries as compared with in the SV may provide one explanation for the better long- and short-term patency of LIMA as compared with SV grafts.

Vacuum-assisted closure therapy guided by C-reactive protein level in patients with deep sternal wound infection

BACKGROUND

Deep sternal wound infection is a serious and potentially lethal complication of cardiac surgery when performed through a median sternotomy. We describe the outcome of a new treatment strategy with C-reactive protein level-guided vacuum-assisted closure used at our department.

METHODS

Data from 16 consecutive adult patients who had deep sternal wound infections after cardiac surgery were reviewed. Patients with superficial infection or sterile dehiscence were not included. All patients with postoperative deep sternal wound infections were treated with first-line vacuum-assisted closure therapy, followed by direct surgical closure. A purpose-built vacuum-assisted closure system consisting of polyurethane foam pieces and a special pump unit was used. The foam was placed in the wound after debridement of foreign material and necrotic tissue. The wound was covered with adhesive drape and connected to the pump unit, which was programmed to create a continuous negative pressure of 125 mm Hg in the wound cavity. Intravenous antibiotics were given according to tissue-culture results. The patients were immediately extubated after the operation. When ingrowth of granulation tissue was observed in all parts of the wound and the plasma C-reactive protein level showed a steady decline to 30 to 70 mg/L or less without confounding factors, such as tissue injuries or concomitant infections, the sternotomy was rewired, and the wound was closed.

RESULTS

All patients were alive and free from deep sternal wound infection 3 months after the operation. The median vacuum-assisted closure treatment time until surgical closure was 9 days (range, 3-34 days), and the median C-reactive protein level at closure was 45 mg/L (range, 20-173 mg/L). The median hospital stay was 22 days (range, 12-120 days).

CONCLUSIONS

Early vacuum-assisted closure treatment, followed by surgical closure guided by the plasma C-reactive protein level, is a reliable and easily applied new strategy in patients with postoperative deep sternal wound infection.

Effects of dopamine in lung-transplanted pigs at 32 degrees C

BACKGROUND

We have used hypothermia successfully in patients with acute respiratory failure after lung transplantation. However, we have observed that dopamine may cause a substantial decrease in mean arterial pressure (MAP) in hypothermic subjects. Furthermore, a dopamine-induced increase in pulmonary vascular resistance (PVR) has been reported in the literature, and this could aggravate the increase in PVR which is often seen both in the early postoperative phase after lung transplantation, and during hypothermia. We thus hypothesized that dopamine would decrease MAP and increase PVR in hypothermic lung-transplanted subjects.

METHODS

Left single lung transplantation combined with right pneumonectomy was performed in 6 pigs anesthetized with ketamine and midazolam and muscle relaxed with pancuronium. After an observation period of 24 h, the effect of dopamine infused at 5 and 12 microg x kg(-1) x min(-1) was studied in normothermia (38 degrees C) and after cooling by cold-water immersion to 32 degrees C.

RESULTS

Systemic vascular resistance index (SVRI) increased and cardiac index (CI) decreased in hypothermia. Dopamine decreased SVRI and increased CI, both in normothermia and at 32 degrees C. MAP decreased during infusion of dopamine in hypothermia. Dopamine had no effect on the pulmonary vascular resistance index (PVRI).

CONCLUSION

The results suggest that dopamine may be used to increase cardiac output after lung transplantation in moderate hypothermia as well as in normothermia, but one should be aware that dopamine may cause a substantial decrease in blood pressure, depending on the prevailing hemodynamic conditions at the start of its administration.

Vascular function in the cadaver up to six hours after cardiac arrest

BACKGROUND

The aim of the study was to evaluate how well vascular function is retained in a cadaver kept in a room with a temperature of 21 degrees C.

METHODS

The aorta and pulmonary artery of rats were investigated in organ baths as fresh controls and after 1, 2, 3, or 6 hours' storage in the cadaver. Six-hour-old cadaver aortas were transplanted and investigated after 24 hours and 60 days.

RESULTS

After 3 hours' storage there was no significant decrease in smooth muscle contractile function in either aorta or pulmonary artery. After 6 hours' storage both the aorta and the pulmonary artery demonstrated a significant decrease in smooth muscle contractile function, 30% (p < 0.05) and 44% (p < 0.001), respectively, compared to fresh controls. Storing the aorta for 2 hours and the pulmonary artery for 6 hours caused no significant decrease in endothelium-dependent relaxing function. In aorta segments investigated after 3 and 6 hours there was a significant decrease in endothelium-dependent relaxation, 12% (p < 0.05) and 29% (p < 0.001), respectively. Six-hour-old cadaver aortas transplanted and investigated after 24 hours or 60 days demonstrated no significant changes in endothelium-dependent relaxation and smooth muscle function compared to fresh controls.

CONCLUSION

The pulmonary artery can tolerate 3 hours of warm ischemia in the nonheart-beating cadaver without loss of endothelium-dependent relaxation and smooth muscle function. The dysfunction seen in 6-hour-old cadaver aortas was normalized after transplantation and 24 hours of reperfusion.

Cardiovascular effects of induced hypothermia after lung transplantation

BACKGROUND

Induced hypothermia may be used to reduce metabolism in acute respiratory failure. Hypothermia is accompanied by an increase in pulmonary vascular resistance, as also seen in the early period after lung transplantation. It was our concern that the combination of the two would lead to an increased workload on the right ventricle.

METHODS

To test this hypothesis we induced hypothermia to 32 degrees C in two groups of pigs. In one group we performed left single-lung transplantation combined with right pulmectomy (TRANSP group); in the other group, only right pulmectomy was performed (PULMEC group).

RESULTS

During hypothermia, there was a significant increase in both groups in pulmonary vascular resistance (TRANSP group, 77%, p<0.05; PULMEC group, 54%, p<0.05) and a significant decrease in cardiac output (TRANSP group, 41%, p<0.05; PULMEC group, 34% p<0.05). Mean pulmonary artery pressure was unchanged, and the work done by the right ventricle was reduced (TRANSP group, 39%, p<0.05; PULMEC group, 31%).

CONCLUSIONS

Induced hypothermia to 32 degrees C after lung transplantation resulted in a significant decrease in the work done by the right ventricle despite a significant increase in pulmonary vascular resistance.

Function of adult pig hearts after 2 and 12 hours of cold cardioplegic preservation

BACKGROUND

Most cardioplegic solutions have been developed using the classic Langendorf heart perfusion model, which only allows a short experimental follow-up. Our aim was to investigate hearts after prolonged storage by using a physiologic model including prolonged perfusion with normal, fresh blood.

METHODS

Sixteen hearts from 60-kg pigs were preserved with dextran-enriched (dextran-40, 35 g/L) St. Thomas' solution for 2 or 12 hours after which they were continuously reperfused for 12 hours with normal blood, supplied by a support pig. A flexible balloon, fixed to an artificial valve apparatus connected to a circuit system, was inserted in the left ventricle for obtaining measurements of hemodynamic performance.

RESULTS

During the first 3 to 4 hours of reperfusion there was no significant difference in left ventricular developed pressure, cardiac output, minute work output, or oxygen consumption between the two groups. After this time left ventricular developed pressure (p < 0.001), cardiac output (p < 0.01), minute work output (p < 0.01), and oxygen consumption were significantly lower in the 12-hour group. Coronary flow was higher (p < 0.01) and coronary vascular resistance lower (p < 0.01) during the first 5 to 6 hours of reperfusion in the 12-hour group. After 12 hours of reperfusion coronary vascular resistance was significantly higher (p < 0.01) in the 12-hour group.

CONCLUSIONS

High-degree and long-lasting coronary hyperemia at the beginning of reperfusion can be a sign of unsatisfactory preservation of the heart. This investigation shows the importance of reperfusion with normal blood and a long follow-up period after postischemic reperfusion when studying the effect of cardioplegic solutions.

Effect of flush-perfusion on vascular endothelial and smooth muscle function

BACKGROUND

The aim of this study was to investigate how much perfusion pressure an artery can tolerate without significant loss of endothelium-dependent relaxation (EDR) and vascular contractility.

METHODS

The abdominal aortas of 396 Sprague-Dawley rats were used. One hundred twenty aortas were flush-perfused for 1 or 5 minutes with cold St. Thomas' Hospital cardioplegic (STHC) solution or with the same solution but modified by the addition of 3.5% dextran 40. Three perfusion pressures were tested: 50, 100, and 150 mm Hg. Two hundred eighty vessels were subjected to pressures of 50, 150, or 300 mm Hg using saline or STHC solution at 22 degrees C or STHC solution at 4 degrees C, for 10 or 60 seconds. The vessels were investigated in organ baths. Contractility was tested with the thromboxane analogue U-46619, acetylcholine was used to investigate EDR, and papaverine to elicit endothelium-independent relaxation.

RESULTS

Flush-perfusion with cold STHC solution for 5 minutes at a perfusion pressure of 50 or 100 mm Hg affected neither contractility nor EDR. Vessels exposed to a flush-perfusion pressure of 150 mm Hg for 1 or 5 minutes lost 39% (p < 0.001) and 53% (p < 0.001) of their contractility, respectively. Flush-perfusion at 150 mm Hg for 1 minute did not affect EDR, whereas 5 minutes' perfusion caused a reduction of 7% (p < 0.05). A repetition of these experiments using STHC solution with 3.5% dextran 40 added gave no significantly different results. The impairment in contractility and EDR seen after perfusion at 150 mm Hg for 5 minutes disappeared after transplantation and reperfusion for 7 days. The vessels could be distended with saline or STHC solution at a pressure of 150 mm Hg without affecting contractility at 22 degrees C. At 4 degrees C, however, this pressure was harmful to contractility. Distention at a pressure of 300 mm Hg almost abolished contractility and 7 days after transplantation there had not yet been any recovery of contractility, but 30 days after transplantation the grafts had regained their normal contractility.

CONCLUSIONS

Cold STHC solution, with or without dextran 40, can be used with a perfusion pressure of 100 but not 150 mm Hg without impairing EDR or vascular smooth muscle function.

Contradictory effects of dopamine at 32 degrees C in pigs anesthetized with ketamine

BACKGROUND

In critically ill patients who were surface cooled to 33 +/- 2 degrees C, we have observed that dopamine sometimes causes a substantial decrease in blood pressure. The present study was designed to compare the effects of dopamine in normothermia to those seen after surface cooling to 32 degrees C.

METHODS

Seven pigs with a mean body weight of 21 kg were anesthetized with ketamine and muscle relaxation was induced with pancuronium. They were mechanically ventilated and given dopamine infusions (5 and 12 micrograms.kg-1.min-1)in normothermia and after surface cooling by cold water immersion to a central blood temperature of 32.0 degrees C (range 31.6-32.6 degrees C).

RESULTS

In normothermia, dopamine at a dose of 5 micrograms.kg-1.min-1 increased mean arterial blood pressure (MAP) by 16% (P < 0.01) and cardiac output (CO) by 9% (P = 0.051); at 12 micrograms.kg-1.min-1 dopamine increased MAP by 26% (P < 0.01) and CO by 18% (P < 0.01). In hypothermia, MAP and CO did not change at an administration rate of 5 micrograms.kg-1.min-1; at 12 micrograms.kg-1.min-1 CO was unchanged but MAP was significantly reduced by 15% (P < 0.01).

CONCLUSION

Dopamine increased CO and MAP in normothermia but not at 32 degrees C, where there was even a significant reduction of MAP in this porcine model.

Successful transplantation of lungs topically cooled in the non-heart-beating donor for 6 hours

BACKGROUND

The aim of this study was to transplant lungs that had been topically cooled in the non-heart-beating donor for 6 hours, using the most challenging evaluation method possible, namely single-lung transplantation followed by immediate contralateral pneumonectomy.

METHODS

Domestic pigs were used (6 donors and 6 recipients) with a mean body weight of 59 +/- 3 kg. Ventricular fibrillation was induced, and after 1 minute, cardiac massage was started and heparin (5 mg/kg body weight) was given via a central venous catheter. Cardiac massage was continued for 10 minutes, during which the pig was ventilated with 50% oxygen. The pleural cavities were opened and the tracheal tube disconnected from the ventilator, with the result that both lungs deflated. Saline slush was placed in both pleural cavities so that it completely covered the lungs. Within 40 minutes the lung core temperature was less than 10 degrees C, and it was kept around 8 degrees C for 6 hours by adjusting the amounts of ice slush. The left lung was then harvested and transplanted into a prepared recipient, followed by right pneumonectomy within 46 +/- 4 minutes, thus making the recipient pig 100% dependent on the transplanted cadaver lung.

RESULTS

The mean ischemic time for the cadaver lungs was 8 hours and 2 minutes (range, 7 hours and 25 minutes to 8 hours and 59 minutes). All animals remained in excellent condition throughout the 24-hour observation period, with arterial oxygen tensions of approximately 225 mm Hg, or 30 kPa (inspired oxygen fraction, 0.5).

CONCLUSIONS

Lungs from non-heart-beating donors may be used for transplantation if heparinization and topical cooling can be initiated within minutes of irreversible cardiac arrest.

Addition of calcium to Euro-Collins solution is essential for 24-hour preservation of the vasculature

BACKGROUND

Genuine Euro-Collins solution is calcium free. The aim of this study was to investigate whether the addition of calcium would improve its capacity to preserve the vasculature.

METHODS

The infrarenal aorta of Sprague-Dawley rats was investigated in organ baths: as fresh controls, after 24 hours of cold (4 degrees C) storage in Euro-Collins solution, or in Euro-Collins solution with the addition of calcium in amounts ranging from 0.05 to 1.5 mmol/L. The thromboxane analogue U-46619 was used to investigate contractility. Endothelium-dependent relaxation was tested by cumulative addition of acetylcholine. Papaverine was used to elicit endothelium-independent relaxation. Investigation by transmission electron microscopy was also performed.

RESULTS

Storage of rat aorta for 24 hours in genuine Euro-Collins solution almost abolished smooth muscle function, and severe edema was found in the endothelial cells. However, if calcium was added, the rat aorta could be stored for 24 hours without affecting smooth muscle function, and endothelium-dependent relaxation was only slightly reduced. Furthermore, only slight edema could be demonstrated in the endothelial cells.

CONCLUSIONS

If calcium is added to Euro-Collins solution in amounts ranging from 0.4 to 1.5 mmol/L, it allows good preservation of rat aorta for 24 hours. Without calcium, this solution destroys both the function and morphology of the vessels.

Inhaled nitric oxide reveals and attenuates endothelial dysfunction after lung transplantation

BACKGROUND

Maintaining endothelial function within transplanted organs may be critical to successful preservation. In this study we have evaluated the relationship between the effect of inhalation of nitric oxide and the degree of endothelial dysfunction after lung transplantation.

METHODS

A left lung, which had been preserved for 24 hours, was transplanted and a right pneumonectomy was performed in 5 pigs. After a 24-hour observation period the pigs inhaled 5, 20, and 80 ppm nitric oxide, and pulmonary vascular resistance was recorded continuously. From the same donors preserved pulmonary arteries from the contralateral lung were studied simultaneously in organ baths. Acetylcholine chloride was used to elicit endothelium-dependent relaxation in vessel segments contracted with the thromboxane A2 analogue U-46619.

RESULTS

Maximal endothelium-dependent relaxation decreased in the preserved lungs and correlated to the pulmonary vascular resistance in the simultaneously transplanted lungs. Inhalation of nitric oxide in the pigs that had received transplants caused the pulmonary vessels to dilate in proportion to the endothelial dysfunction.

CONCLUSIONS

Preservation of lung for transplantation induces an endothelial dysfunction, and the degree of the decrease in pulmonary vascular resistance caused by nitric oxide inhalation may be an indication of the degree of this endothelial damage. The vasodilation caused by inhaled nitric oxide increases as the endothelial function deteriorates.

Effect of temperature in long-term preservation of vascular endothelial and smooth muscle function

BACKGROUND

In clinical transplantation the donor organ is perfused with a cold preservation solution to obtain quick core cooling and a suitable environment for the tissue cells. Without good preservation of the vasculature, progressive deterioration of the blood flow during reperfusion may ultimately lead to the no-reflow phenomenon, even though the function of the other cells in the organ may be adequately preserved. The aim of this study was to find the optimal storage temperature for preservation of the vasculature.

METHODS

The infrarenal aorta of 126 Sprague-Dawley rats were studied in organ baths: as fresh controls, after 36 hours of storage at 0.5 degrees C, 4 degrees C, 8.5 degrees C, and 22 degrees C in University of Wisconsin solution, and after 36-hour storage followed by transplantation and a lapse of 2 hours, 24 hours, and 7 days. The thromboxane analogue U-46619 was used to test contractility. Acetylcholine was used to elicit endothelium-dependent relaxation (EDR), and papaverine to elicit endothelium-independent relaxation.

RESULTS

Storing the vessels at 0.5 degree C proved best regarding preservation of contractility, with a nonsignificant decrease, whereas storage at 4 degrees C and 8.5 degrees C resulted in a significant decrease after 36 hours. The contractility did not recover within 24 hours of in vivo reperfusion, but full recovery was seen after 7 days. Regardless of the preservation temperature used, a significant impairment in EDR was seen after 36 hours of storage. Two hours after transplantation, vessels stored at 4 degrees C and 8.5 degrees C showed no significant impairment in EDR, whereas those stored at 0.5 degrees C demonstrated a significant loss of EDR. After 24 hours and after 7 days, EDR was normal in all groups.

CONCLUSIONS

Endothelium-dependent relaxing factor function is best preserved at 4 degrees C and 8.5 degrees C, whereas preservation of vascular smooth muscle function is best preserved at 0.5 degrees C.

Importance of calcium in long-term preservation of the vasculature

BACKGROUND

The aim was to investigate the effect of calcium in organ preservation solutions with respect to 36-hour preservation of vascular smooth muscle function and endothelium-dependent relaxation.

METHODS

The infrarenal aortas of 60 Sprague-Dawley rats were studied in organ baths as fresh controls and after 36 hours of cold (4 degrees C) storage in different preservation solutions with and without calcium. The thromboxane A2 analogue U-46619 was used to study contractility. Endothelium-dependent relaxation was tested by the cumulative addition of acetylcholine. Papaverine hydrochloride was used to elicit endothelium-independent relaxation.

RESULTS

Krebs solution was the only solution able to fully preserve contractility. Krebs solution without calcium gave poor preservation. After the addition of 1.5 mmol/L of calcium to University of Wisconsin solution and to Perfadex, both these solutions became fully able to preserve contractility. None of the solutions (with or without calcium) were fully able to preserve endothelium-dependent relaxation, although University of Wisconsin solution gave good preservation and Perfadex, fair preservation. Euro-Collins solution and K+ (124 mmol/L)-enriched Krebs solution were not able to preserve smooth muscle function or endothelium-dependent relaxation.

CONCLUSIONS

Calcium is essential for long-term preservation of vascular smooth muscle function but not for long-term preservation of endothelium-dependent relaxation.

Inhalation of nitric oxide after lung transplantation

BACKGROUND

Pulmonary hypertension is a postoperative complication that may adversely affect the outcome of lung transplantation. The effect of nitric oxide (NO) inhalation on pulmonary hemodynamic indices after lung transplantation was studied and compared with findings in control pigs.

METHODS

Varying concentrations of NO were inhaled by 5 pigs after left lung transplantation and right pneumonectomy and by 5 controls after right pneumonectomy at an inspired oxygen fraction of 0.21 and 0.5. Hemodynamic data were recorded continuously, and fast circulatory courses were analyzed.

RESULTS

Inhalation of NO reduced pulmonary vascular resistance and mean pulmonary arterial pressure in all pigs, but the decrease was pronounced and dose dependent only at an inspired oxygen fraction of 0.21 in the pigs that had transplantation. These were the only pigs that became hypoxic. With the termination of NO, there was a dose-independent rebound pulmonary vasoconstriction in the controls, especially at an inspired oxygen fraction of 0.21, but not in the pigs that had transplantation. This response was transient and could be blunted with a higher inspired oxygen fraction.

CONCLUSION

Inhalation of NO reduced pulmonary vascular resistance in the transplanted lung and may be useful in the treatment of pulmonary hypertension after lung transplantation. The rebound pulmonary vasoconstriction with the termination of NO inhalation stresses the need to be aware of this effect and to wean NO carefully in clinical situations. This study showed oxygen dependency, which has to be taken into consideration in dose-response studies involving NO inhalation.

Perfadex is superior to Euro-Collins solution regarding 24-hour preservation of vascular function

BACKGROUND

The aim of this study was to compare Perfadex with Euro-Collins solution regarding 24-hour preservation of endothelium-dependent relaxation and vascular smooth muscle function.

METHODS

The infrarenal aorta of 72 isogenic rats was studied in organ baths as fresh controls, after 24 hours of cold (4 degrees C) storage, and after 24-hour storage followed by transplantation and examination after 7 or 30 days. The thromboxane A2 analogue U-46619 was used to test contractility. Acetylcholine chloride was used to elicit endothelium-dependent relaxation and papaverine hydrochloride, to elicit endothelium-independent relaxation.

RESULTS

With both solutions, all grafts were patent after 7 and 30 days. Vessels preserved in Euro-Collins solution for 24 hours lost 95% (p < 0.001) of their contractility compared with fresh controls; 7 days after transplantation, they had regained 40% of initial contractility, and after 30 days, there was no significant decrease in contractility. Vessels preserved in Perfadex manifested no significant decrease in contractility at any time. Endothelium-dependent relaxation could not be evaluated in vessels stored for 24 hours in Euro-Collins solution because they had lost almost all contractility; 7 days after transplantation, endothelium-dependent relaxation was reduced by 65% (p < 0.001), but at 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation. Vessels preserved in Perfadex for 24 hours lost 17% (p < 0.05) of endothelium-dependent relaxation, but 7 and 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation.

CONCLUSIONS

Perfadex, but not Euro-Collins solution, has the capacity to preserve vascular function after 24 hours of storage followed by in vivo reperfusion.

Long-term preservation of vascular endothelium and smooth muscle

This study was performed in organ baths on 400 ring segments of infrarenal aorta taken from 40 Sprague-Dawley rats that had been randomized into five groups. Contractility was tested with the thromboxane analogue U-46619. Acetylcholine was used to elicit endothelium-dependent relaxing factor (EDRF). The results obtained from vessels preserved at 4 degrees C for 6, 12, 24, and 36 hours were compared with those from autologous vessels studied immediately after harvesting. Vessels preserved in Euro-Collins solution showed a 46% (p < 0.01) decrease in contractility after 12 hours of storage; after 24 hours only weak contractions could be elicited, and after 36 hours they had lost their ability to contract. The EDRF function was slightly reduced after 12 hours and could not be investigated after 24 and 36 hours. With the University of Wisconsin solution (UW) and the low-potassium-dextran-glucose solution Perfadex no decrease in contractility was seen in the first 24 hours, but at 36 hours the vessels preserved in UW had lost 40% (p < 0.01) and those preserved in Perfadex 30% (p < 0.05) of their contractility. The EDRF function was significantly reduced by about 15% after 6, 12, and 24 hours in both the UW and the Perfadex groups. At 36 hours, vessels stored in Perfadex had lost 41% (p < 0.001) and those stored in UW 17% (p < 0.01) of their EDRF function.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of topical cooling in lung preservation: is a reappraisal due?

The aim of the present study was to test the efficacy of topical cooling as the only viable lung preservation method using the most challenging evaluation method, namely single-lung transplantation followed by immediate contralateral pneumonectomy. Ten domestic pigs (5 donors and 5 recipients) with a mean body weight of 57 kg (range, 53 to 59 kg) were used. After we administered systemic heparin (4 mg/kg), the lungs were harvested and placed in an atelectatic state under cold (8 degrees to 9 degrees C) low-potassium-dextran solution for 12 hours. Left lung transplantation was then done in the recipient pig followed by right pneumonectomy, thus making the recipient 100% dependent on the transplanted donor lung. No operative mortality or morbidity occurred. All animals were in excellent condition throughout the 24-hour observation period. They had normal blood gases which did not differ significantly from the preoperative blood gases obtained from the 5 recipients before transplantation (ie, when they had their own two lungs). A moderate increase (p < 0.05) in pulmonary vascular resistance was seen as compared with sham-operated animals. To conclude, topical cooling to 8 degrees C provides excellent lung preservation for 12 hours in pigs. If similar results can be obtained with other species, the currently accepted 6-hour limit for safe clinical lung preservation may be extended to 12 hours. It seems also warranted to critically reconsider which factors, apart from cooling alone, actually contribute favorably to 12-hour lung preservation.

Endothelium-dependent relaxation after short-term preservation of vascular grafts

As the integrity of graft endothelium seems to be essential to successful long-term patency in coronary operations, its preservation demands the utmost care. The aim of the present study was to investigate the effects of currently used solutions on endothelium-dependent relaxation after short-term storage of vessels at room temperature or at 4 degrees C. The infrarenal rat aorta was selected for study because its use enabled standardization of the investigation, which was performed in organ baths on 672 vessel segments from 112 Sprague-Dawley rats. Stable vasoconstriction was obtained with the thromboxane analogue U-46619. Acetylcholine was used to elicit endothelium-dependent relaxation. The results obtained for vessels preserved for 2 hours were compared with those for autologous vessels studied immediately after harvesting. Vessel contractility was unaffected by the preservation solutions, except in the Ringer's acetate group, where it was reduced by 50% (p < 0.05). Endothelium-independent relaxation, tested with papaverine, was unaffected in all groups. Ringer's lactate, Krebs solution, and Perfadex (a low-potassium-dextran-glucose solution) did not significantly affect endothelium-dependent relaxation either at room temperature or at 4 degrees C, although a tendency to impaired relaxation was seen in these three groups after cold storage. Standard Ringer's solution and fresh heparinized blood each significantly reduced endothelium-dependent relaxation in vessels stored at room temperature (p < 0.05), but not in those stored at 4 degrees C. Endothelium-dependent relaxation was significantly reduced after storage in normal saline solution (p < 0.05) and in Ringer's acetate (p < 0.01), both at room temperature and at 4 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Safe lung preservation for twenty-four hours with Perfadex

The function of six porcine left lung allografts was studied after pulmonary (140 mL/kg) and bronchial (50 mL/kg) artery perfusion with Perfadex (Kabi Pharmacia, Uppsala, Sweden) at room temperature, followed by 24-hour storage of the lungs in an atelectatic state in 6 degrees to 8 degrees C Perfadex, which is a low-potassium-dextran solution. Left lung transplantation was done followed by right pneumonectomy, thereby making all the animals 100% dependent for their survival on the transplanted lungs. The pigs (mean weight = 56 kg, range = 51 to 58 kg, n = 18; 6 donors, 6 recipients, and 6 sham operated) were ventilated with a volume-controlled ventilator (20 breaths/min, 500 mL tidal volume, 8 cm H2O positive end-expiratory pressure, inspired oxygen fraction = 0.5). All the transplanted animals were in good condition throughout the 24-hour observation period with arterial oxygen tensions around 25 kPa (188 mm Hg) and arterial carbon dioxide tensions around 5 kPa (38 mm Hg). The mean pulmonary arterial pressure was around 30 mm Hg, and the pulmonary vascular resistance around 500 dyn.s.cm-5; neither showed any tendency to change with time. After 24 hours the inspired oxygen fraction was increased to 1.0 and the arterial oxygen tension increased to 43.3 +/- 5 kPa (325 +/- 38 mm Hg) (mean +/- standard error of the mean; n = 6). A sham operation (bilateral thoracotomy, right pneumonectomy) was done in 6 pigs, which were followed up for 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)