Simulation: a teaching tool for liver transplantation anesthesiology.

Anesthesia for liver transplantation (ALT) requires extensive preparation and rapid recognition of changing clinical conditions. Owing to the proliferation of transplant centers, greater number of anesthesia providers need training in specific skills required to treat these patients. These cases are no longer limited to few transplant centers; therefore, reduction of cases in individual centers has created a need for simulation training to prepare and supplement clinical experience. We have developed an ALT simulation course for senior anesthesia residents which combines didactic sessions with live-patient-based and mannequin-based simulation. Outcomes have been measured using pre- and post-simulation course quizzes as well as a survey given at the end of the month-long ALT rotation. Twenty-four senior anesthesiology residents (n = 24) have completed the ALT simulation course. Residents had an average score of 75% ± 10% on the pre-simulation quiz, which increased to 92% ± 6.5% on the post-simulation quiz (p < 0.001). Furthermore, survey scores indicated that residents noted that the course provided an improvement in their preparedness, confidence, anticipation, and understanding of the importance of communication skills in the care of this patient population. The ALT simulation course provided a standardized in-depth exposure to clinical issues involved in the perioperative care of liver transplant patients.

The role of ultrasonography in determining central venous patency in patients undergoing bowel transplantation.

Ultrasonography (US) is an attractive alternative for invasive studies to evaluate venous patency. However, little data exist concerning the usefulness of US in patients undergoing bowel transplantation. Twenty-five adult patients with bowel transplantation were retrospectively identified with both US and contrast venography (VG) performed preoperatively. The median age was 43 yr, and the median duration of total parenteral nutrition was 36 months. The vessels were evaluated as positive with ≥ 50% stenosis. Among the internal jugular veins and the subclavian veins examined with US (96% of the all sites) and with VG (69%), 66 venous sites were available for comparison. VG confirmed positive in 42% (28/66), while US found positive in 27% (18/66); US had three false positives and 13 false negatives, giving the sensitivity of 54% (95% confidence interval [CI], 34-72) and the specificity of 92% (CI, 77-98). The positive and the negative likelihood ratios weighted by prevalence (42%) were 5 (CI, 1.7-14.3) and 0.37 (CI, 0.23-0.60), respectively. In addition, VG confirmed stenosis in 32% of the right and 50% of the left brachiocephalic veins and 41% of the superior vena cava. US is not a reliable method for assessing the upper body venous system of patients undergoing bowel transplantation.

Cirrhosis is not a contraindication to laparoscopic cholecystectomy: results and practical recommendations.

BACKGROUND: Gallstones appear more frequently in patients with cirrhosis and open cholecystectomy in this patient population is associated with higher morbidity and mortality. The aim of the present study was to evaluate experience with laparoscopic cholecystectomy in patients with cirrhosis and to provide recommendations for management. METHODS: Retrospective review of laparoscopic cholecystectomy in patients with cirrhosis from March 1999 to May 2008 was performed. Peri-operative characteristics and subgroup analysis were performed in patients with Child-Pugh's classes A, B and C cirrhosis. RESULTS: A total of 68 patients were reviewed in this study. In all, 69% of the patients were Child's class A. The most common indication for cholecystectomy was chronic/symptomatic cholelithiasis (68%). Compared with patients with Child's class B and C, laparoscopic cholecystectomy in patients with Child's class A was associated with significantly decreased operative time (P= 0.01), blood loss (P= 0.001), conversion to open cholecystectomy (P= 0.001) and length of hospital stay (P= 0.001). CONCLUSIONS: Laparoscopic cholecystectomy in patients with cirrhosis is feasible with no mortality and low morbidity, especially in patients with Child's class A cirrhosis.

Noninvasive monitoring of cerebral perfusion pressure in patients with acute liver failure using transcranial doppler ultrasonography.

Elevated intracranial pressure (ICP) leads to loss of cerebral perfusion, cerebral herniation, and irreversible brain damage in patients with acute liver failure (ALF). Conventional techniques for monitoring ICP can be complicated by hemorrhage and infection. Transcranial doppler ultrasonography (TCD) is a noninvasive device which can continuously measure cerebral blood flow velocity, producing a velocity-time waveform that indirectly monitors changes in cerebral hemodynamics, including ICP. The primary goal of this study was to determine whether TCD waveform features could be used to differentiate ALF patients with respect to ICP or, equally important, cerebral perfusion pressure (CPP) levels. A retrospective study of 16 ALF subjects with simultaneous TCD, ICP, and CPP measurements yielded a total of 209 coupled ICP-CPP-TCD observations. The TCD waveforms were digitally scanned and seven points corresponding to a simplified linear waveform were identified. TCD waveform features including velocity, pulsatility index, resistive index, fraction of the cycle in systole, slopes, and angles associated with changes in the slope in each region, were calculated from the simplified waveform data. Paired ICP-TCD observations were divided into three groups (ICP < 20 mmHg, n = 102; 20 < or = ICP < 30 mmHg, n = 74; and ICP > or = 30 mmHg, n = 33). Paired CPP-TCD observations were also divided into three groups (CPP > or = 80 mmHg, n = 42; 80 > CPP > or = 60 mmHg, n = 111; and CPP < 60 mmHg, n = 56). Stepwise linear discriminant analysis was used to identify TCD waveform features that discriminate between ICP groups and CPP groups. Four primary features were found to discriminate between ICP groups: the blood velocity at the start of the Windkessel effect, the slope of the Windkessel upstroke, the angle between the end systolic downstroke and start diastolic upstroke, and the fraction of time spent in systole. Likewise, 4 features were found to discriminate between the CPP groups: the slope of the Windkessel upstroke, the slope of the Windkessel downstroke, the slope of the diastolic downstroke, and the angle between the end systolic downstroke and start diastolic upstroke. The TCD waveform captures the cerebral hemodynamic state and can be used to predict dynamic changes in ICP or CPP in patients with ALF. The mean TCD waveforms for corresponding, correctly classified ICP and CPP groups are remarkably similar. However, this approach to predicting intracranial hypertension and CPP needs to be further refined and developed before clinical application is feasible.

Intracranial pressure observations in a canine model of acute liver failure supported by a bioartificial liver support system.

Life-threatening, severely elevated intracranial pressure (ICP) is a common feature of acute liver failure (ALF). Perfusion with a bioartificial liver may serve to mitigate rising ICP. A retrospective analysis of ICP measurements in a canine ALF model prospectively supported with a bioartificial liver support system (BLSS) is presented. Animals are divided into two groups based upon care provided: (i) standard medical care (n = 6); and (ii) standard medical care plus BLSS support (n = 9). Nonparametric analysis with respect to ICP, arterial NH(3), lactate, and supportive-care parameters found BLSS-supported animals evidenced significantly less metabolic acidosis than unsupported animals. Analysis of variance/linear regression for direct dependence of ICP on arterial NH(3), lactate, and supportive care parameters irrespective of care found ICP was uncorrelated with any measured factor (P > 0.06 for all factors). Lack of correlation of ICP with the considered parameters indicates that none of these factors are predictive of the extent of ICP elevation in the D-galactosamine canine model. Blood chemistry and supportive care factors that are correlated with and predictive of ICP elevation remain to be identified.

Cerebral hemodynamic and metabolic profiles in fulminant hepatic failure: relationship to outcome.

The purpose of this retrospective study was to examine the potential role of cerebral hemodynamic and metabolic factors in the outcome of patients with fulminant hepatic failure (FHF). Based on the literature, a hypothetical model was proposed in which physiologic changes progress sequentially in five phases, as defined by intracranial pressure (ICP) and cerebral blood flow (CBF) measurements. Seventy-six cerebral physiologic profiles were obtained in 26 patients (2 to 5 studies each) within 6 days of FHF diagnosis. ICP was continuously measured by an extradural fiber optic monitor. Global CBF estimates were obtained by xenon clearance techniques. Jugular venous and peripheral artery catheters permitted calculation of cerebral arteriovenous oxygen differences (AVDO2), from which cerebral metabolic rate for oxygen (CMRO2) was derived. A depressed CMRO2 was found in all patients. There was no evidence of cerebral ischemia as indicated by elevated AVDO2s. Instead, over 65% of the patients revealed cerebral hyperemia. Eight of the 26 patients underwent orthotopic liver transplantation-all recovered neurologically, including 6 with elevated ICPs. Of the 18 patients receiving medical treatment only, all 7 with increased ICP died in contrast to 9 survivors whose ICP remained normal (P < 0.004). Hyperemia, per se, was not related to outcome, although it occurred more frequently at the time of ICP elevations. Six patients were studied during brain death. All 6 revealed malignant intracranial hypertension, preceded by hyperemia. In conclusion, the above findings are consistent with the hypothetical model proposed. Prospective longitudinal studies are recommended to determine the precise evolution of the pathophysiologic changes.

Analysis of vascular access in intestinal transplant recipients using the Miami classification from the VIIIth International Small Bowel Transplant Symposium.

BACKGROUND: Loss of vascular access in patients with intestinal failure is considered an indication for intestinal transplantation. Such patients often have one or more occluded vein sites. Venous access could be classified according to the number of occluded vessels, to facilitate pre- and postoperative management. METHODS: At the VIIIth International Small Bowel Transplant Symposium in September 2003, a new classification of vascular access in patients who were candidates for bowel transplant was proposed. The classification was then applied to stratify all patients that underwent intestinal transplantation at the University of Miami between 1998 and 2003. Data were collected on Doppler ultrasonography, angiography, and vein angioplasty in such patients. RESULTS: A total of 106 cases in 91 patients were included in the study. Based on Doppler ultrasound results, 51.9% of patients fell into class I (no thrombosed vessels), 21.7% were in class II (one occluded vessel, or positive risk factors for thrombosis), 24.5% were in class III (multiple thrombosed vessels), and 1.9% were in class IV (all vessels thrombosed). Fifteen percent of the patients required preoperative angiography to better evaluate venous access. Most of the patients that required angiography were in class III or IV, and 53.3% of patients requiring angiography needed additional venous angioplasty to achieve access. CONCLUSIONS: All patients that are referred for intestinal transplantation should undergo preliminary mapping of their venous access by Doppler ultrasound and then be assigned to a vascular access class. Those patients with multiple thrombosed vessels (class III and above) should be strongly considered for additional angiographic evaluation.

Transesophageal echocardiography-guided placement of internal jugular percutaneous venovenous bypass cannula in orthotopic liver transplantation.

Venovenous bypass has improved patient survival and decreased morbidity and mortality in the field of orthotopic liver transplantation. The standard at many transplant centers is the use of the internal jugular percutaneous venovenous bypass cannulae (PVVBC) for venous return to the patient. Placement of these large (18F) PVVBC may lead to several complications and requires confirmation before use. Use of transesophageal echocardiography, an effective and rapid method to guide placement of the PVVBC and minimize potential complications associated with insertion of the device, is described.

D-galactosamine based canine acute liver failure model.

BACKGROUND: Appropriate preclinical evaluation of a bioartificial liver assist device (BAL) demands a large animal model, as presented here, that demonstrates many of the clinical features of acute liver failure and that is suitable for clinical qualitative and quantitative evaluation of the BAL. A lethal canine liver failure model of acute hepatic failure that removes many of the artifacts evidenced in prior canine models is presented. METHODS: Six male hounds, 24-30 kg, under isoflurane anesthesia, were administered 1.5 g/kg D-galactosamine intravenously. Canine supportive care followed a well-defined management protocol that was guided by electrolyte and invasive monitoring consisting of arterial pressure, central venous pressure, extradural intracranial pressure (ICP), pulmonary artery pressure, and end-tidal CO2. The animals were treated until death-equivalent, defined as inability to sustain systolic blood pressure >80 mmHg for 20 minutes despite maximal fluids and 20 microg/kg/min dopamine infusion. RESULTS: The mean survival time was 43.7+/-4.6 hours (mean+/-SE). All animals showed evidence of progressive liver failure characterized by increasing liver enzymes (aspartate transaminase from 26 to 5977 IU/L; alanine transaminase from 32 to 9740 IU/L), bilirubin (0.25 to 1.30 mg/dl), ammonia (19.8 to 85.3 micromol/L), and coagulopathy (prothrombin time from 8.7 to 46 s). Increased lability and elevations in intracranial pressures were observed. All animals were refractory to maintenance of cerebral perfusion pressure even with only moderately elevated intracranial pressure. Severe neurologic obtundation, seen in 2 of 6 animals, was associated with elevations of ICP above 50 mmHg. Post-mortem liver histology showed evidence of massive hepatic necrosis. Postmortem blood and ascites microbial growth was consistent with possible translocation of intestinal microbes. CONCLUSIONS: The improved lethal canine liver failure model presented here reproduces many of the clinical features of acute liver failure. The model may prove useful for qualitative and quantitative evaluation of BALs.