Rupert Koller

The vacuum-assisted closure system for the treatment of deep sternal wound infections after cardiac surgery.

BACKGROUND The VAC system (vacuum-assisted wound closure) is a noninvasive active therapy to promote healing in difficult wounds that fail to respond to established treatment modalities. The system is based on the application of negative pressure by controlled suction to the wound surface. The method was introduced into clinical practice in 1996. Since then, numerous studies proved the effectiveness of the VAC System on microcirculation and the promotion of granulation tissue proliferation. METHODS Eleven patients (5 men, 6 women) with a median age of 64.4 years (range 50 to 78 years) with sternal wound infection after cardiac surgery (coronary artery bypass grafting = 5, aortic valve replacement = 5, ascending aortic replacement = 1) were fitted with the VAC system by the time of initial surgical debridement. RESULTS Complete healing was achieved in all patients. The VAC system was removed after a mean of 9.3 days (range 4 to 15 days), when systemic signs of infection resolved and quantitative cultures were negative. In 6 patients (54.5%), the VAC system was used as a bridge to reconstructive surgery with a pectoralis muscle flap, and in the remaining 5 patients (45.5%), primary wound closure could be achieved. Intensive care unit stay ranged from 1 to 4 days (median 1 day). Duration of hospital stay varied from 13 to 45 days (median 30 days). In-hospital mortality was 0%, and 30-day survival was 100%. CONCLUSIONS The VAC system can be considered as an effective and safe adjunct to conventional and established treatment modalities for the therapy of sternal wound infections after cardiac surgery.

Functional and morphometric evaluation of end-to-side neurorrhaphy for muscle reinnervation.

This study was undertaken to quantify the effect of motor collateral sprouting in an end-to-side repair model allowing end organ contact. Besides documentation of the functional outcome of muscle reinnervation by end-to-side neurorrhaphy, this experimental work was performed to determine possible downgrading effects to the donor nerve at end organ level. In 24 female New Zealand White rabbits, the motor nerve branch to the rectus femoris muscle of the right hindlimb was dissected, cut, and sutured end-to-side to the motor branch to the vastus medialis muscle after creating an epineural window. The 24 rabbits were divided into two groups of 12 each, with the second group receiving additional crush injury of the vastus branch. After a period of 8 months, maximum tetanic tension in the reinnervated rectus femoris and the vastus medialis muscles was determined. The contralateral healthy side served as control. The reinnervated rectus femoris muscle showed an average maximum tetanic force of 24.9 N (control 26.2 N, p = 0.7827), and the donor vastus medialis muscle 11.0 N (control 7.3 N, p = 0.0223). There were no statistically significant differences between the two experimental groups (p = 0.9914). The average number of regenerated myelinated nerve fibers in the rectus femoris motor branch was 1185 ± 342 (control, 806 ± 166), and the mean diameter was 4.6 ± 0.6 &mgr;m (control, 9.4 ± 1.0 &mgr;m). In the motor branch to the vastus medialis muscle, the mean fiber number proximal to the coaptation site was 1227 (±441), and decreased distal to the coaptation site to 795 (±270). The average difference of axon counts in the donor nerve proximal to distal regarding the repair site was 483.7 ± 264.2. In the contralateral motor branch to the vastus medialis muscle, 540 (±175) myelinated nerve fibers were counted. In nearly all cross-section specimens of the motor branch to the vastus medialis muscle, altered nerve fibers could be identified in one fascicle distal and proximal to the repair site. The results show a relevant functional reinnervation by end-to-side neurorrhaphy without functional impairment of the donor muscle. It seems to be evident that most axons in the attached segment were derived from collateral sprouts. Nonetheless, the present study confirms that end-to-side neurorrhaphy is a reliable method of reconstruction for damaged nerves, which should be applied clinically in a more extended manner. (Plast. Reconstr. Surg. 106: 383, 2000.)

Prognostic factors in adenocarcinoma of the cardia

BACKGROUND The optimal extent of resection for adenocarcinomas of the gastroesophageal junction is controversial. This study was conducted to examine whether the extent of resection is an independent prognostic factor in cardia cancer. METHODS The records and survival data of 125 patients who underwent resection for cancer of the cardia were retrospectively analyzed. Multiple regression was used to evaluate prognostic factors in patients who underwent proximal gastric resection (PR) or total gastrectomy (TG) for cancer of the cardia. RESULTS Seventy-five patients underwent PR and 50 TG. The 5-year survival was 40% for tumors confined to the esophageal wall (T1, T2), and 13% in more advanced cases (T1, T2; P = 0.0001). Twenty-two percent of the patients with tumor-free margins, 10% of those with microscopic residual tumor, and none with macroscopic residual tumor survived longer than 5 years (P = 0.0001 for any residual tumor versus no residual tumor). Lymph node involvement (P = 0.002) and stage (P = 0.0001) were also significant in the univariate analysis. Five-year survival was 18% after TG, and 17% after PR (P = NS). CONCLUSION Multiple regression identified residual tumor and penetration depth as independent predictors of survival (P = 0.0002, and P = 0.0001, respectively). After correction for these factors, none of the following variables were of additional significance: extent of resection (TG versus PR), lymph node involvement, age, or Laurens classification. In 19 of 20 cases with microscopic incomplete resection, it was the oral margin that was positive. We conclude that the extent of resection (TG versus PR) does not influence survival in adenocarcinoma of the gastroesophageal junction.

Role of a muscle target organ on the regeneration of motor nerve fibres in long nerve grafts : A synopsis of experimental and clinical data

The importance of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts is still a subject of controversial discussion. In the last few years we published uniform results of experimental series in sheep and rabbits in which we investigated the biology of nerve fibre regeneration in long nerve autografts without connection to a target organ. Surprisingly, we found excellent regeneration of myelinated nerve fibres without the influence of a target organ through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end. In the sheep series the additional contact with a muscle target organ for 6 months had a variable effect on the fibre population in the distal end of the nerve graft. The results of our planimetric analyses of nerve biopsies in patients with facial paralysis, who were treated by cross-face nerve grafting and free muscle transplantation, are extremely divergent from the results of our experimental series. Instead of an increase, we found a decrease in number of regenerating nerve fibres arriving at the distal end of the cross-face nerve graft down to 20%. Species-specific differences in the biology of nerve regeneration are discussed, together with their implications for the complex clinical situation of nerve grafting with or without the influence of a target organ.

Primary or delayed closure for the treatment of poststernotomy wound infections

ObjectiveThe methods of primary versus delayed wound closure for the treatment of sternal wound infections after cardiac surgery were retrospectively compared. MethodsFrom January 2001 to March 2003, 132 patients (median age 66 years, male to female ratio 88:44) with sternal wound infection after cardiac surgery were treated at our department. After thorough debridement, 35 patients received preconditioning of the wound before implementation of definitive therapy; the remainder (97 patients) were treated with immediate closure. ResultsFrom the 35 patients with preconditioning, 19 patients proceeded to delayed primary closure, whereas the remaining 14 patients were referred to plastic reconstruction with a pectoralis muscle flap. Primary success rate in this group was 100%.In the immediate primary closure group, 33 patients experienced 1 or more therapy failures, resulting in a recurrence rate of 39%. Fifteen patients received a pectoralis muscle flap as definite treatment modality. ConclusionsImmediate primary closure is associated with a high rate of local infection recurrence. Surgical debridement and conditioning of the wound until resolution of infections with delayed primary closure or plastic reconstruction is suggested as the more appropriate treatment modality, with promising results.

The axillary vein central venous catheter in severely burned patients

In severely burned patients the approach to the central vein is often difficult due to concomitant edema, but also due to the fact that the skin area, where commonly used approaches are performed, is burned as well, whereas the axillary region is often not involved. In order to perform an axillary approach to the central vein as an alternative to the commonly used approaches in patients, an anatomical dissection in fresh human cadavers was carried out. Considering the anatomical landmarks which were found during dissection of the axillary region, the axillary approach to the central vein was used in 35 patients in our intensive burn care unit with unaffected axillary skin. In three cases the only complication observed was an occasional puncture of the axillary artery without major hematoma. The infection rate of the catheters was similar to the commonly used puncture sites. This approach to the central venous line in severely burned patients can be recommended.

Long-term results of nervous tissue alterations caused by epineurial electrode application: an experimental study in rat sciatic nerve.

In order to evaluate the long‐term effects of epineurial electrode application for functional electrical stimulation (FES) the left sciatic nerve of seven rats was exposed. Four ring‐shaped stainless steel wire electrodes were sutured to the epineurium of each nerve in the same manner as performed clinically for carrousel stimulation in man. The nerves were reexposed 1 year after implantation and the stimulation threshold to obtain a tetanic contraction in the lower limb was determined for each electrode. Afterwards the animals were sacrificed. The electrodes were excised and cross sections of the sciatic nerve directly at the site of the electrodes, 2‐mm proximal and 2‐mm distal to them were harvested for hisfologic and planimetric assessment of nerve lesions. The area of damaged neural tissue was expressed as a percentage of the total cross‐sectional area within the perineural sheath. The sciatic nerves of the right side served as controls. The values for the stimulation thresholds ranged between 0.1 and 1.0 mA (mean 0.43 mA). By morphometric examination five of seven nerves were seen altered, the altered areas captured between 1% and 4.8% of the total cross‐sectional area of the nerves within the perineural sheath. Besides two specimens, all altered nerve segments exhibited distinct signs of nerve fiber regeneration. The clinical implications of the results for long‐term electrical stimulation, such as phrenic pacing, are discussed.

Ipsilateral and cross-over elongation of the motor nerve by nerve grafting: an experimental study in sheep.

In difficult reconstructions, ipsilateral or cross-over nerve grafting is sometimes necessary to achieve reinnervation and motor function. This experimental study in sheep was to answer the question of limitation of elongation of a motor nerve by grafting, the question of the optimal time for suturing the nerve graft to the muscle nerve, and the question of the successful application of this surgical technique in extremities. In 18 sheep, the vastus nerve was elongated by a saphenous nerve graft as long as possible up to 30 cm (step 1). In 10 animals the nerve graft was applied ipsilaterally, and in 8 animals it was used as a cross-over nerve graft to the contralateral limb. The time between nerve grafting and connection of the distal end of the nerve graft to the freshly cut rectus nerve supplying the rectus femoris muscle (step 2) was variable: 0, 3, 6, 9, and 12 months. In all animals, the final experiments (step 3) were performed 6 months after the last operation (step 2). Muscle force measurements in the rectus femoris muscle and quantitative analysis of the number and diameter of myelinated nerve fibers in cross sections of the nerve biopsies at different levels showed that elongation of a motor nerve by nerve grafting is principally not limited. The functional results were rather inhomogeneous and therefore unpredictable (ipsilateral group: maximum tetanic tension = 27 to 172 N; cross-over group: 0 to 227.5 N). Nevertheless, crossover nerve grafting is recommended for selected cases even in extremities. There was no correlation between the time interval between the two operations and the functional or morphologic results, although better functional results were obtained when the distal nerve suture (step 2) was performed some months after nerve grafting (step 1). A clear correlation was found only between the number of regenerated axons in the rectus nerve behind the second suture line and the muscle function.

Experimental development of an electrically stimulated biological skeletal muscle ventricle for chronic aortic counterpulsation

OBJECTIVE The chronic shortage of donor organs for cardiac transplantation and the high costs for mechanical assist devices demand the development of alternative cardiac assist devices for the treatment of severe heart failure. Cardiac assistance by stimulated skeletal muscles is currently investigated as such a possible alternative. The goal of the presented study was to construct a newly designed biological skeletal muscle ventricle and to evaluate its possible hemodynamic efficacy in an acute sheep model. METHODS A total of 14 adult sheep were used for acute experiments. The entire thoracic aorta including the aortic root was excised from a donor sheep. An aorto-pericardial pouch conduit (APPC) was created by enlarging the aortic circumference in its middle section with two strips of pericardium. This biological conduit was anastomosed in parallel to the descending aorta of a recipient sheep, using the aortic root as an inflow valve to the conduit. Stimulation electrodes were applicated to the thoracodorsal nerve and the latissimus dorsi muscle was detached from the trunk and wrapped around the pouch. ECG-triggered functional electrical stimulation was applied during cardiac diastole to simulate aortic counterpulsation. Stimulation was performed during various hemodynamic conditions. RESULTS A standardised surgical procedure suitable for long term studies was established during six experiments. An APPC, with 70-80 mm filling volume, was found to be of optimal size. In another eight experiments, hemodynamic measurements were performed. Under stable hemodynamic conditions the stimulation of the biological skeletal muscle ventricle induced a significant increase of mean arterial pressure by 14% and mean diastolic pressure by 26%. During pharmacologically induced periods of cardiac failure, the stimulation of the APPC increased mean arterial pressure by 13% and mean diastolic pressure by 19%. In all eight experiments, the diastolic peak pressure reached supra-systolic values during stimulation. CONCLUSIONS The results demonstrate the hemodynamic efficacy of this newly designed biological skeletal muscle ventricle as an aortic counterpulsation device. Chronic experiments using a preconditioned fatigue-resistant muscle will further help to evaluate its possible clinical significance.

The use of allogeneic cultivated keratinocytes for the early coverage of deep dermal burns - indications, results and problems.

Since 1995, keratinocytes are grown into cultures and used as allografts for the coverage of deep dermal defects in our burn unit. Donor skin samples are mostly acquired from other burn patients. In addition, special methods of skin preservation allow us the use of skin, which has been taken in redundancy for split thickness skin grafting from nonburned patients.Thirty five patients with deep partial thickness burns in the face were treated since 1996 according to the following concept: Dermabrasion or tangential excision was performed before the 5th day following trauma. If viable dermis was present, the wounds were covered with sheets of allogeneic cultivated keratinocytes. In cases of deeper defects, autologous skin grafts were applied. In 23 cases, epithelialisation was achieved within 10 days, in 8 patients, a prolonged duration until complete healing was observed. In 5 faces, coverage of residual defects with skin grafts was necessary. The mentioned problems of wound healing occurred from infection, incomplete excision of burn eschar and a depth of the wound which was retrospectively seen too deep for the treatment with keratinocytes. At follow up, patients were examined clinically and functionally with Freys faciometer®, which is an instrument for quantification of mimic movements. In cases of uncomplicated healing, a nearly complete restitution was found.Other indications include deep dermal burns in children and the coverage of early excised wounds in adults, with a reasonable amount of viable dermis remaining, both resulting in a significant reduction of donor-site morbidity. In severely burned adults with limited donor sites, it offers the possibility of immediate definite coverage of large areas.