Brian T. Bethea

Application of haptic feedback to robotic surgery.

Robotic surgical systems have greatly contributed to the advancement of minimally invasive endoscopic surgery. However, current robotic systems do not provide tactile or haptic feedback to the operating surgeon. Under certain circumstances, particularly with the manipulation of delicate tissues and suture materials, this may prove to be a significant irritation. We hypothesize that haptic feedback, in the form of sensory substitution, facilitates the performance of surgical knot tying. This preliminary study describes evidence that visual sensory substitution permits the surgeon to apply more consistent, precise, and greater tensions to fine suture materials without breakage during robot-assisted knot tying.

Aortic Root Replacement in 372 Marfan Patients: Evolution of Operative Repair Over 30 Years

BACKGROUND We reviewed the evolution of practice and late results of aortic root replacement (ARR) in Marfan syndrome patients at our institution. METHODS A retrospective clinical review of Marfan patients undergoing ARR at our institution was performed. Follow-up data were obtained from hospital and office records and from telephone contact with patients or their physicians. RESULTS Between September 1976 and September 2006, 372 Marfan syndrome patients underwent ARR: 269 had a Bentall composite graft, 85 had valve-sparing ARR, 16 had ARR with homografts, and 2 had ARR with porcine xenografts. In the first 24 years of the study, 85% received a Bentall graft; during the last 8 years, 61% had a valve-sparing procedure. There was no operative or hospital mortality among the 327 patients who underwent elective repair; there were 2 deaths among the 45 patients (4.4%) who underwent emergent or urgent operative repair. There were 74 late deaths (70 Bentalls, 2 homograft, and 2 valve-sparing ARRs). The most frequent causes of late death were dissection or rupture of the residual aorta (10 of 74) and arrhythmia (9 of 74). Of the 85 patients who had a valve-sparing procedure, 40 had a David II remodeling operation; there was 1 late death in this group, and 5 patients required late aortic valve replacement for aortic insufficiency. A David I reimplantation procedure using the De Paulis Valsalva graft has been used exclusively since May 2002. All 44 patients in this last group have 0 to 1+ aortic insufficiency. CONCLUSIONS Prophylactic surgical replacement of the ascending aorta in patients with Marfan syndrome has low operative risk and can prevent aortic catastrophe in most patients. Valve-sparing procedures, particularly using the reimplantation technique with the Valsalva graft, show promise but have not yet proven as durable as the Bentall.

Analysis of Suture Manipulation Forces for Teleoperation with Force Feedback

Despite many successes with teleoperated robotic surgical systems, some surgeons feel that the lack of haptic (force or tactile) feedback is detrimental in applications requiring fine suture manipulation. In this paper, we study the difference between applied suture forces in three knot tying exercises: hand ties, instrument ties (using needle drivers), and robot ties (using the da Vinci? Surgical System from Intuitive Surgical, Inc.). Both instrument and robot-assisted ties differ from hand ties in accuracy of applied force. However, only the robot ties differ from hand ties in repeatability of applied force. Furthermore, comparison between attendings and residents revealed statistically significant differences in the forces used during hand ties, although attendings and residents perform similarly when comparing instrument and robot ties to hand ties. These results indicate that resolved force feedback would improve robot-assisted performance during complex surgical tasks such as knot tying with fine suture.

Pharmacological preconditioning ameliorates neurological injury in a model of spinal cord ischemia

BACKGROUND Pharmacological openers of mitochondrial ATP-sensitive potassium (mitoKATP) channels have been shown to mimic ischemic preconditioning (IPC) in both the brain and myocardium. We hypothesized that similar endogenous mechanisms exist in the spinal cord and that diazoxide, a potent mitoKATP opener, could reduce neurologic injury after aortic cross-clamping in a model of spinal cord ischemia. METHODS The infra-renal aorta was cross-clamped in 45 male New Zealand white rabbits for 20 minutes. Control animals received no pretreatment. Diazoxide-treated animals were dosed (5 mg/kg) 15 minutes before cross-clamp. A third group underwent 5 minutes of IPC 30 minutes before cross-clamp. Two groups received KATP antagonists, 5-hydroxydecanoic acid (5-HD, 20 mg/kg) or glibenclamide (1.0 mg/kg), before diazoxide administration. Systemic hypotension was induced in a final group with excess isoflurane. Tarlov Scoring was used to assess neurologic function at 24 and 48 hours, after which, the spinal cords were procured for histopathological analysis. RESULTS Tarlov scoring demonstrated marked improvement in the Diazoxide group compared with control at 24 hours (p < 0.02) and 48 hours (p < 0.009). Moreover, no further neurologic injury occurred in this group at 7 days. IPC-treated animals showed neurologic improvement but were not significantly different from controls. Further, administration of glibenclamide was effective in antagonizing diazoxides protective effect. CONCLUSIONS Administration of diazoxide resulted in significant improvement in neurologic outcome in this model. This protective effect improved outcome at both early and late time points. Further, the antagonistic effect of glibenclamide implicates diazoxides ATP-dependent potassium channel agonism as the mechanism of protection. Overall, this study suggests that diazoxide may be useful in the prevention of neurologic injury after thoracic aneurysm surgery.

Effect of sensory substitution on suture manipulation forces for surgical teleoperation.

Bilateral telemanipulation, which applies haptic feedback to the operator, is not yet available in most commercial robot-assisted surgical systems. We have shown in previous work that the lack of haptic (force or tactile) feedback is detrimental in applications requiring fine suture manipulation. In this paper, we study the effect of substituting direct haptic feedback with visual and auditory cues. Using the da Vinci robot from Intuitive Surgical, we observed the difference between applied forces during a knot tying procedure for four different sensory feedback substitution scenarios: no feedback, auditory feedback, visual feedback, and a combination of auditory and visual feedback. Our results indicate that visual feedback, which provides continuous force information, would improve robot-assisted performance during complex surgical tasks such as knot tying with fine sutures. Discrete auditory feedback gives additional useful support to the surgeon.

Surgery for aortic root aneurysm in children: a 21-Year experience in 50 patients

BACKGROUND Ascending aortic aneurysms are unusual in children and have received little attention to develop guidelines for management. This study reviewed our experience with 50 children who have undergone aortic root replacement for ascending aortic aneurysm. METHODS A retrospective clinical review was conducted using hospital charts and office records. Patients or their physicians were contacted for follow-up and recent echocardiograms were obtained and reviewed. RESULTS There was no operative or hospital mortality. Twenty-six children had aortic root replacement with a composite graft, 10 patients had replacement with a homograft aortic root, and 14 patients had a David II valve-sparing procedure. Factors related to late morbidity and mortality were analyzed. Long-term results were excellent in the 26 children receiving a composite graft. Twenty-three of these children were New York Heart Association class I (19) or II (4) at study closure. There were 3 late deaths (11, 16, and 17 years postoperative). Seven of 10 children receiving a homograft aortic root are long-term survivors and all 14 children having a valve-sparing procedure are alive. Generally, late results with the David II remodeling procedure have been good although 3 patients developed late aortic insufficiency and two required valve replacement. CONCLUSIONS Aortic root replacement in children with aneurysms has low operative risk and good long-term results. Composite grafts in particular carry a low risk of endocarditis, thromboembolism, and hemorrhagic events. Homografts are suitable for small patients but lack durability. Late results with the David II remodeling valve-sparing procedure in children have been compromised by late root dilatation.

Impact of 24 h continuous hypothermic perfusion on heart preservation by assessment of oxidative stress.

Abstract:  Introduction:  Despite investigating numerous solutions, additives, and techniques over the last two decades, extending donor heart preservation beyond 4–6 h has not been achieved. Hypothermic heart preservation (HP) induces oxidative stress (OS) with reactive oxygen species (ROS) production, causing DNA cleavage and impairing repair. Quantification of cardiomyocyte concentrations of DNA damage by‐products (8‐oxoG) and mismatch repair enzymes (MYH, OGG‐1, MSH2) reflects the severity of OS. If increased repair enzyme production is insufficient to repair injury, cell death occurs and functional outcomes are impacted. We investigated continuous hypothermic perfusion (CHP), a new form of HP, and the mechanism of injury associated with hypothermic storage, by assessing functional outcome and OS after allotransplantation of canine hearts.

Pulmonary resection following lung transplantation

BACKGROUND The morbidity of lung transplantation is higher than other solid organ transplants. Little is known about the outcomes of patients who require pulmonary resection following lung transplantation. We reviewed our experience to evaluate and discern any variables affecting outcome of pulmonary resections performed following lung transplantation. METHODS A retrospective review of the lung transplant database was performed. Data are presented as mean +/- standard error (median). RESULTS A total of 136 lung transplants (80 single lung transplants [SLT], 55 bilateral lung transplants [BLT], and 3 heart-lung transplants [HLT]) were performed from August 1995 to February 2002. Twelve pulmonary resections, 7 lobectomies, and 5 wedge resections were performed on 11 patients. The indication for lobectomy was infection in 5 of 7 lobectomies (3 fungal, 2 bacterial), mass in 1 of 7, and infarction in 1 of 7. The indication for wedge resection was native lung hyperinflation in 4 of 5 wedge resections and mass in 1 of 5. The native lung was resected in 3 of 7 lobectomies and 4 of 5 wedge resections. An allograft lobectomy was performed following 1 SLT and 3 BLT and a wedge resection was performed after 1 SLT. The mean time to pulmonary resection was 12.4 +/- 3.9 (9.1) months. Survival postresection was 17.2 +/- 5.8 (8.3) months and 5 of 11 patients are still alive. There were no bronchial stump leaks following lobectomy. CONCLUSIONS Major pulmonary resections can safely be performed following lung transplant. We recommend early intervention to optimize outcomes.