Alex Karatassas

Hypothermia induced by laparoscopic insufflation. A randomized study in a pig model.

Hypothermia is a common postsurgical problem, yet information documenting the impact of laparoscopy on perioperative heat balance is scarce. This paper quantifies the changes in core temperature over a 3-h period of high-flow CO2 insufflation in a randomized, controlled trial of six pigs. Each animal was anesthetized and studied on three occasions under standardized conditions, acting as its own control via insufflation with no gas compared with insufflation by cold gas and warmed gas.Insufflation of CO2 gas at high-flow rates over a prolonged period of time results in a significant fall in core temperature. The provision of warmed rather than cold insufflated gas confers no protection against changes in core temperature during laparoscopic surgery due to the small amount of heat required to warm the gas to body temperature. A much greater effect is the latent heat required to saturate the insufflated gas. Most of the hypothermic effect is due to this, and could be minimized by humidifying the flow.

Safety of 96-hour incision-site continuous infusion of ropivacaine for postoperative analgesia after bowel cancer resection

The aim of this study was to examine the safety of ropivacaine given to patients as a continuous infusion [0.2% (2 mg/mL), 5 mL/h for 96 hours] into a right lateral transverse incision using a portable elastomeric infusion pump after colon cancer resection. Blood samples were collected throughout the infusion and up to 12 hours after infusion and were analyzed by high-performance liquid chromatography (HPLC) for total and unbound ropivacaine concentrations in plasma. Alpha1 acid glycoprotein (AAG) concentrations were measured at 0 and 48 hours to assess possible changes in ropivacaine protein binding after surgery. Postoperative pain control was assessed using 12 hour visual analog scale (VAS) scores. Patient-controlled analgesia (PCA) using fentanyl was freely available in parallel for breakthrough pain, with usage and consumption compared with a historical cohort. The mean ± SD Cmax total plasma ropivacaine concentration (n = 5) from 12 hours to the end of the infusion was 4.5 ± 2.6 mg/L, comparable with the previously published threshold for CNS toxicity in the most sensitive patient studied (3.4 mg/L). However, the corresponding maximum unbound ropivacaine concentration (ie, the pharmacologically active moiety) of 0.07 ± 0.01 mg/L ranged from four- to sevenfold below the reported toxicity threshold (0.34 mg/L). The apparently greater safety margin seen with unbound ropivacaine may have resulted from a significant increase (mean 63%, P < 0.05) in AAG concentrations measured at 48 hours after surgery. This reduction resulted from the known AAG reaction after surgical intervention, resulting in a reducing unbound ropivacaine fraction throughout the 96 hour infusion in all patients. Mean subjective 12 hour pain scale scores at rest and on movement showed large variability between patients. No signs or symptoms of ropivacaine toxicity were observed or reported on questioning. In this limited sample, extending the infusion period from the presently approved 48 hours to 96 hours seems to be a safe alternative and/or adjunct to standard opiate analgesia after colorectal surgery using a right lateral transverse incision, hence reducing the incidence of opiate adverse effects and enhancing recovery. Unbound ropivacaine concentrations suggest there is scope for testing elevated doses to enhance efficacy further.

Effect of preoperative two‐dimensional animation information on perioperative anxiety and knowledge retention in patients undergoing bowel surgery: a randomized pilot study

The use of multimedia information provided preoperatively can potentially reduce anxiety in patients and improve the hospital experience. However, the use of two‐dimensional (2D) animation (cartoon) to provide information to patients undergoing colorectal surgery has not been investigated. This study investigated the effect of preoperative 2D information on anxiety and knowledge retention in patients undergoing bowel surgery.

A randomized double-blind clinical trial of a continuous 96-hour levobupivacaine infiltration after open or laparoscopic colorectal surgery for postoperative pain management--including clinically important changes in protein binding.

Background: Continuous local anesthetic infiltration has been used for pain management after open colorectal surgery. However, its application to patients undergoing laparoscopic colorectal surgery has not been examined. The aim of this prospective, randomized, double-blind, placebo-controlled clinical trial was to study the use of a commercial infiltration device in patients undergoing open or laparoscopic colorectal surgery, along with plasma concentrations of levobupivacaine, its acute-phase binding protein (alpha-1 acid glycoprotein, AAG), and the stress marker, cortisol. Methods: Eligible patients were randomized (2:1) to receive a continuous infiltration of either levobupivacaine or placebo using a commercial device (ON-Q PainBuster) inserted in the preperitoneal layer at the end of surgery. Blood was sampled for determination of levobupivacaine and AAG and cortisol concentrations. Other outcomes measured were pain scores, morbidity and mortality, time to bowel movement, mobilization, and length of hospitalization. Results: In patients having open surgery, the levobupivacaine treatment showed a trend toward reduced total opioid consumption. No patients reported adverse effects attributable to levobupivacaine, despite 11 patients having concentrations at some time(s) during the 96-hour infiltration of up to 5.5 mg/L exceeding a putative toxicity threshold of 2.7 mg/L. AAG concentrations measured postsurgery increased by a mean of 55% (P < 0.001) at 48 hours. Cortisol concentrations also increased significantly by a mean of 191% at 1 hour. Conclusions: Continuous local anesthetic infiltration may be more beneficial in open surgery. The threshold for adverse effects from highly bound local anesthetic drugs established in healthy volunteers is of limited usefulness in clinical scenarios in which AAG concentration increases in response to surgical stress. Hence, there is scope to adopt higher doses to enhance therapeutic benefit.

Regional blood flow as a determinant of drug absorption description of an animal model

Factors that influence recommended dosage guidelines for intramuscularly and subcutaneously injected drugs include a spectrum of variables, including therapeutic objective(s), the drugs therapeutic index, the inclusion of concomitant vasoconstrictors, and so on. However, little account is taken of the likely influence of regional blood flow at the injection site. This may vary according to the site of injection, the age and medical condition of the patient with the potential to markedly affect the rate of drug absorption and the resultant therapeutic and toxicity outcomes. An animal model is described for simultaneously quantifying the drugs pharmacokinetic profile and the regional blood flow (using technetium99 elution) at sites of differing vascularity so that the potential relationship can be ascertained. An application to lignocaine absorption is provided, however, the model would be applicable to a range of drug applications and could serve as a means of investigating differences both within a drug class (e.g., members with differing lipophilicity) as well as across drug classes (e.g., local anesthetics, opiates, insulin preparations, etc.).

Developing a mesh-tissue integration index and mesh registry database: the next step in the evolution of hernia repair: Perspectives

The use of mesh in incisional hernia repair has been paramount in reducing recurrence rates when compared with suture closure only. Factors influencing early efficacy of hernia repair include adequate closure of the defect, the size and strength (weight) of mesh, and type and security of fixation. Long-term efficacy is dependent on tissue incorporation into the mesh scaffold. The degree of meshtissue ingrowth affects recurrence rate and tissue flexibility, which relates to functional outcome and resistance to mesh infection. There is a ‘Goldilocks’ state to be achieved in mesh-tissue integration (MTI) which is key to an adequate, durable and functional repair. Excessive tissue response results in dense fibrosis, mesh shrinkage, seromas and chronic pain. Inadequate response can result in infection and recurrence (Fig. 1). Numerous intrinsic and extrinsic factors are known to affect MTI. Hydrophilic mesh is favourable as it allows rapid tissue ingrowth. Microporous filaments (>10 μm) allow white blood cells to infiltrate, and macropore (>1.5 mm) components allow penetration of blood vessels and avoid coalescing of fibrotic capsule, resulting in a flexible and functional repair. Preserving macroporosity by ensuring technical factors during mesh placement, such as avoiding overstretching or folding of the mesh, is important. Patient factors such as tissue vascularity and systemic conditions determined by diabetes, smoking, obesity, steroids and genetics, influence tissue integration. Theoretically, adjuncts such as growth factors, fibrin and autologous leucocyte platelet-rich fibrin may enhance MTI. There are over 150 mesh products available that have Food and Drug Administration (United States) and/or Therapeutic Goods Administration (Australia) approval. There is no requirement for manufacturers to provide MTI data. By only reporting the compositional safety profile of meshes, surgeons choose a mesh based primarily on its physical characteristics and technical ease of insertion. While there are a number of papers about tissue response to mesh, the lack of evidence around MTI precludes adopting a more holistic and tailored approach to hernia surgery. Tailoring surgery to optimize outcomes in hernia repair requires a greater understanding of the biological response elicited by any given mesh and how this response may be manipulated. Broadening this understanding will challenge existing assumptions about how mesh products help achieve successful outcomes. We propose developing a standardized, numerical MTI index for meshes placed in the subrectus and intraperitoneal position. The purpose is to assist surgeons in selecting a mesh according to its tissue ingrowth characteristics, matched to the individual patient to achieve an optimal outcome. Devising an MTI index will involve measuring the rate and extent of tissue ingrowth in an animal model based on macroscopic (including visual integration, mesh shrinkage, number of adhesions and T-Peel testing), microscopic (including cell population, and proportion of immune cells, growth cells and mature collagen) and biologic (protein quantification of vascular endothelial growth factor, transforming growth factor-beta and platelet-derived growth factors) assessments at 1, 4, 8, 12 and 24 weeks post-surgery. By examining a number of time points, we can assess the rate of tissue ingrowth, which is lacking from published data. The index will range from 1 to 5. Meshes with an index of 1 will have poor tissue integration while those with an index of 5 will have excellent vascularized tissue ingrowth and adequate fixation within 4 weeks of insertion. A fibrosis sub-index (F) will define meshes according to foreign body reaction. The fibrosis sub-index will range from 1 to 5, with 5 indicating negligible amounts of giant cell infiltration and 1 indicating an excessive foreign body reaction. A mesh with an F-index of 5 will be flexible with minimal shrinkage, whilst a mesh with an F-index of 1 may have a high incidence of rigidity and marked shrinkage. For meshes placed intraperitoneally, an adhesion sub-index (A) will be calculated adapted from previous studies. The adhesion index will range from 1 to 5, with 5 indicating minimal or no adhesions and 1 indicating dense adhesions. Accordingly, the preferred mesh will display an MTI index of 5, an F-index of 5 and an A-index of 5, equating to a fully incorporated and fixed mesh within 4 weeks, with excellent flexibility and no shrinkage, rigidity or adhesions. The indices will require validation. It is simplistic to believe that indices based on animal studies will translate to predictable patient outcomes considering the diversity and complexity of patients. To fully appreciate the significance of MTI, a longitudinal database that records mesh indices and patient characteristics against outcomes is pivotal in progressing hernia management towards a truly holistic and tailored approach (Fig. 1). A well-designed and resourced database will allow systematic assessment and refinement of the use of mesh products in hernia surgery. It may then be possible to understand not only the predictors of successful outcomes but also the factors associated with failures. This in turn may allow surgeons to assess the role of adjuvant growth factors in subpopulations of patients to improve MTI or indeed adjuvant agents to downregulate excessive tissue response to mesh. Incisional hernia surgery is undergoing a conceptual shift from a ‘mechanical approach’ (e.g. component separation, huge mesh overlap) to a ‘biological approach’. A biological paradigm is multifaceted. It may involve preoperative optimization of the patient by use of botulinum toxin for muscle relaxation and appropriate selection of mesh, with growth factor adjuncts, with the aim to reduce

Single port component separation: endoscopic external oblique release for complex ventral hernia repair

BackgroundComponent separation (CS) is a technique which mobilizes flaps of innervated, vascularized tissue, enabling closure of large ventral hernia defects using autologous tissue. Disadvantages include extensive tissue dissection when creating these myofascial advancement flaps, with potential consequences of significant post-operative skin and wound complications. This study examines the benefit of a novel, ultra-minimally invasive single port anterior CS technique.MethodsThis was a prospective study of 16 external oblique (EO) releases performed in 9 patients and 4 releases performed in 3 fresh frozen cadavers. All patients presented with recurrent complex ventral hernias, and were administered preoperative Botulinum Toxin A to their lateral oblique muscles to facilitate defect closure. At the time of elective laparoscopic repair, patients underwent single port endoscopic EO release using a single 20-mm incision on each side of the abdomen. Measurements were taken using real-time ultrasound. Postoperatively, patients underwent serial examination and abdominal CT assessment.ResultsSingle port endoscopic EO release achieved a maximum of 50-mm myofascial advancement per side (measured at the umbilicus). No complications involving wound infection, hematoma, or laxity/bulge have been noted. All patients proceeded to laparoscopic or laparoscopic-open-laparoscopic intraperitoneal mesh repair of their hernia, with no hernia recurrences to date.ConclusionsSingle port endoscopic EO release holds potential as an adjunct in the repair of large ventral hernia defects. It is easy to perform, is safe and efficient, and entails minimal disruption of tissue planes and preserves abdominal wall perforating vessels. It requires only one port-sized incision on each side of the abdomen, thus minimizing potential for complications. Further detailed quantification of advancement gains and morbidity from this technique is warranted, both with and without prior administration of Botulinum Toxin A to facilitate closure.

Day case hernia repair: weak evidence or practice gap?: Day case hernia repair

Analysis of a private insurers administrative data set revealed significant variation in the length of hospital stay following hernia surgery.

Pain or gain: new innovations and trends in hernia repair

follow-up was short in our series, there were already three patients who reported recurrent disease between 6 and 12 months, none, however, requiring surgery. Recurrence rates of up to 65% are reported with significant proportion of patients requiring further interventions. As a result, the risk involved in a short-term gain must be small and the benefits significant in order to justify the temporizing measure. This highlights the importance of appropriate patient selection in treating Dupuytren’s with PNF. It was pointed out at a meeting of the American Society of Surgery of the Hand by Keith Denkler MD who was discussing PNF that there is ‘no one operation for Dupuytren’s’ and that several smaller procedures may be the treatment of choice in many situations. This comment may soon extend to incorporate the use of clostridial collagenases currently being trailed with apparent success, but no published results to discuss. It is important to note that PNF can be repeated, and its previous use does not preclude in itself the use of any other procedure available. In the U.K., increasing popularity and demand for PNF has led to publication of official guidelines for its use. This review of the evidence by the National Institute for Clinical Excellence is summarized in Table 1. As yet, there is no Australian equivalent of this. With PNF gaining increasing popularity among the patient population, it is important to understand the technique and its place in the treatment of Dupuytren’s disease. With easy access to information via the Internet, an increasing number of patients present asking for this procedure. Many patients elect to travel overseas in order to avoid more invasive surgical procedures in the belief that PNF is not offered in Australia. Percutaneous needle fasciotomy is a safe and effective technique for treatment of Dupuytren’s disease in the appropriately selected patient. Patients undergoing PNF treatment need to be informed of the potential complications and the risk of early recurrence to allow them to make a decision on which treatment modality is best for them. We believe that needle fasciotomy (PNF) is a useful technique that can be used in these well-selected patients, and should be included in the armamentarium of the surgeon treating Dupuytren’s contracture.