1,721,541 research outputs found
Hand-assisted advanced laparoscopic procedures. Placement of the hand assist device is essential
No full textWe read with interest the article by De Maria et al. [2]
on hand-assisted laparoscopic bypass. The authors
concluded that hand-assisted laparoscopic bypass did
not improve clinical outcome and was associated with
increased costs compared to open gastric bypass for the
surgical treatment of obesity.
The highest incidence of ventral hernias can be
found in patients with aortic aneurysms. In a retrospective study,we analyzed intermediate-term results of
hand-assisted laparosocopic (HALS) aortic aneurysm
surgery. Because of the well-known problems with alterations in connective tissue metabolism in these patients,we wanted to evaluate whether the minimal
invasive approach caused a reduction in the incidence of
ventral hernias.
A total of 182 aneurysm patients were operated on
using hand-assisted laparoscopy with a hand-assist device inserted through a small midline incision like the
one described by de Maria et al. [2]. In 48 cases,a
ventral hernia developed at the site where the hand-assist device had been inserted. The proportion of these
cases (18.7%) is still lower than the 30% incidence of
ventral hernias in aneurysm patients reported in the
literature,but the benefit of minimal invasive access is
certainly lost because a substantial number of patients
require reoperation due to abdominal wall problems.
For our HALS patients with a low transverse Pfannenstiel incision or a miniaccess in the left lower flank
region like the one performed for laparoscopic sigmoid
resection,wound-related problems could be detected in
less than 2% (Fig. 1).
This can probably be explained in part by the routine
use of self-retaining retractors with subsequent transient
skin and muscle ischemia. Therefore,we changed our
protocol and the whole aortic HALS case was performed under pneumoperitoneum [4,5]. The miniincision for the hand-assist device must be placed
strategically in a way that wound-related problems are
reduced and the patient can have the benefit of a total
laparoscopic procedure. It is well-known from open
surgery that any kind of incision in the upper abdomen
can compromise ventilatory function,causes more pain
even compared to a thoracotomy,and has an increased
incidence of ventral hernias.
As in HALS donor nephrectomies,as well as in our
aortic cases,the minilaparotomy for the HALS device
has to be placed in the lower abdomen. All aspects of the
operation are performed under pneumoperitoneum,including suturing of an aortic anastomosis without the
need for self-retaining retractors.
HALS is a technique that facilitates and accelerates
complex laparoscopic operations,reduces the conversion rate to open surgery when total laparoscopic procedures are performed,and is superior to any
miniincision surgery in which a midline laparotomy is
require
General Clauses for SAT-Based Proof Search in Intuitionistic Propositional Logic
No full textIn recent years some papers have addressed the problem of the validity in Intuitionistic Propositional Logic (IPL) using the approach proposed by Claessen and Ros & eacute;n based on reduction to Satisfiability Modulo Theories. This approach depends on an initial preprocessing phase that reduces the input formula in the intuitionistic language to an equivalent sequent in the language of clauses. In this paper we present general clauses, an extension of the clauses used by Claessen and Ros & eacute;n, that allow us to define a natural relationship between the semantics of the extended clauses and Kripke semantics. We present a decision procedure for general clauses and we show how to encode intuitionistic formulas in the language of general clauses so to decide IPL. The experimental results show that our implementation in general outperforms the state-of-the-art provers for IPL. In principle general clauses can be used as a target language for other non-classical logics with Kripke semantics, so that our decision procedure can be used to decide them
Duality between Unprovability and Provability in Forward Refutation-search for Intuitionistic Propositional Logic
No full textThe inverse method is a saturation-based theorem-proving technique; it relies on a forward proof-search strategy and can be applied to cut-free calculi enjoying the subformula property. Here, we apply this method to derive the unprovability of a goal formula G in Intuitionistic Propositional Logic. To this aim we design a forward calculus FRJ(G) for Intuitionistic unprovability, which is appropriate for constructively ascertaining the unprovability of a formula G by providing a concise countermodel for it; in particular, we prove that the generated countermodels have minimal height. Moreover, we clarify the role of the saturated database obtained as result of a failed proof-search in FRJ(G) by showing how to extract from such a database a derivation witnessing the Intuitionistic validity of the goal
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