Endoscopic full-thickness resection of polyps involving the appendiceal orifice: a multicenter international experience

BACKGROUND

Endoscopic resection of lesions involving the appendiceal orifice remains a challenge. We aimed to report outcomes with the full-thickness resection device (FTRD) for the resection of appendiceal lesions and identify factors associated with the occurrence of appendicitis.

METHODS

This was a retrospective study at 18 tertiary-care centers (USA 12, Canada 1, Europe 5) between November 2016 and August 2020. Consecutive patients who underwent resection of an appendiceal orifice lesion using the FTRD were included. The primary outcome was the rate of R0 resection in neoplastic lesions, defined as negative lateral and deep margins on post-resection histologic evaluation. Secondary outcomes included the rates of: technical success (en bloc resection), clinical success (technical success without need for further surgical intervention), post-resection appendicitis, and polyp recurrence.

RESULTS

66 patients (32 women; mean age 64) underwent resection of colonic lesions involving the appendiceal orifice (mean [standard deviation] size, 14.5 (6.2) mm), with 40 (61 %) being deep, extending into the appendiceal lumen. Technical success was achieved in 59/66 patients (89 %), of which, 56 were found to be neoplastic lesions on post-resection pathology. Clinical success was achieved in 53/66 (80 %). R0 resection was achieved in 52/56 (93 %). Of the 58 patients in whom EFTR was completed who had no prior history of appendectomy, appendicitis was reported in 10 (17 %), with six (60 %) requiring surgical appendectomy. Follow-up colonoscopy was completed in 41 patients, with evidence of recurrence in five (12 %).

CONCLUSIONS

The FTRD is a promising non-surgical alternative for resecting appendiceal lesions, but appendicitis occurs in 1/6 cases.

Endoscopic ultrasound-directed transgastric ERCP (EDGE): a retrospective multicenter study

BACKGROUND

Endoscopic ultrasound-directed transgastric endoscopic retrograde cholangiopancreatography (ERCP; EDGE) is an alternative to enteroscopy- and laparoscopy-assisted ERCP in patients with Roux-en-Y gastric bypass anatomy. Although short-term results are promising, the long-term outcomes are not known. The aims of this study were: (1) to determine the rates of long-term adverse events after EDGE, with a focus on rates of persistent gastrogastric or jejunogastric fistula; (2) to identify predictors of persistent fistula; (3) to assess the outcomes of endoscopic closure when persistent fistula is encountered.

METHODS

This was a multicenter retrospective study involving 13 centers between February 2015 and March 2019. Adverse events were defined according to the ASGE lexicon. Persistent fistula was defined as an upper gastrointestinal series or esophagogastroduodenoscopy showing evidence of fistula.

RESULTS

178 patients (mean age 58 years, 79 % women) underwent EDGE. Technical success was achieved in 98 % of cases (175/178), with a mean procedure time of 92 minutes. Periprocedural adverse events occurred in 28 patients (15.7 %; mild 10.1 %, moderate 3.4 %, severe 2.2 %). The four severe adverse events were managed laparoscopically. Persistent fistula was diagnosed in 10 % of those sent for objective testing (9/90). Following identification of a fistula, 5 /9 patients underwent endoscopic closure procedures, which were successful in all cases.

CONCLUSIONS

The EDGE procedure is associated with high clinical success rates and an acceptable risk profile. Persistent fistulas after lumen-apposing stent removal are uncommon, but objective testing is recommended to identify their presence. When persistent fistulas are identified, endoscopic treatment is warranted, and should be successful in closing the fistula.

Percutaneous transcystic cholangioscopy-assisted rendezvous ERCP in a hostile abdomen

Video 1Percutaneous transcystic cholangioscopy-assisted rendezvous ERCP in a hostile abdomen.

Correction to: Anatomical Configuration of the Stomach Post-Endoscopic Sleeve Gastroplasty (ESG)-What Are the Sutures Doing?

The name of author Vivek Kumbhari was misspelled in the original article.

Dysphagia predicts greater weight regain after Roux-en-Y gastric bypass: a longitudinal case-matched study

BACKGROUND

Weight regain (WR) after gastric bypass is thought to be multifactorial in etiology with behavioral, neurohormonal, and anatomic features playing a role. A significant proportion of patients complain of dysphagia after Roux-en-Y gastric bypass (RYGB) and may have difficulty tolerating solid foods. Our observations suggest that this subgroup of patients compensate for esophageal symptoms by increasing their intake of calorie-dense liquid and soft foods, which can precipitate WR.

OBJECTIVES

We hypothesize that dysphagia predisposes to greater WR than seen in individuals without swallowing symptoms.

SETTING

Single tertiary care referral center.

METHODS

This was a matched-cohort study analysis of prospectively collected data on RYGB patients. All individuals who underwent high-resolution manometry after RYGB were enrolled. Controls were identified via a retrospective analysis of a prospective institutional database. Patients who developed dysphagia were matched with controls, from a subset of 450 eligible controls. Each patient with dysphagia was matched with 4 control patients based on age, body mass index, and time since surgery. WR was defined as an increase of ≥15% from nadir. Χ² and t test (or Wilcoxon rank sum, if applicable) were used for bivariable analysis. Multiple logistic and linear regression were used for multivariable calculations.

RESULTS

Forty-nine patients with dysphagia were included. After matching, there were 196 RYGB controls that did not have swallowing or esophageal symptoms. Controls had similar baseline demographic characteristics and initial weight loss compared with dysphagia cases. WR was common in both groups; however, total WR in those with dysphagia was greater than controls (15.7 versus 11.4 kg, respectively; P = .02). In addition, percent WR in those with dysphagia exceeded that seen in controls (mean 37% versus 25%, P = .003), and more individuals regained 15% of nadir weight (55% of dysphagia cases versus 38% of controls, P = .03) when adjusting for baseline body mass index, age at surgery, and race. Dietary histories suggested that, among those with dysphagia, patients with partial or complete conversion to soft or liquid calories had greater WR than those who adhered to the solid food diet.

CONCLUSIONS

Dysphagia is a risk factor for WR post-RYGB. This is likely due to increased intake of soft or liquid foods that are tolerable in these patients but lead to a positive energy balance and accelerated WR. More than half of patients with dysphagia after RYGB regain significant weight. Screening for and aggressively managing dysphagia in patients before or after RYGB may be warranted to prevent significant WR.

The EDGI new take on EDGE: EUS-directed transgastric intervention (EDGI), other than ERCP, for Roux-en-Y gastric bypass anatomy: a multicenter study

Background and study aims  Indications for accessing the duodenum, and/or excluded stomach in Roux-en-Y gastric bypass (RYGB) patients extend beyond diagnosis and treatment of pancreaticobiliary maladies. Given the high technical and clinical success of EUS-directed transgastric ERCP (EDGE) in RYGB anatomy, we adopted this transgastric (anterograde) approach to evaluate and treat luminal and extraluminal pathology in and around the excluded gut in RYGB patients. EUS-directed transgastric intervention ("EDGI"), other than ERCP, is the terminology we have chosen to describe this heterogenous group of transgastric diagnostic and/or interventional endoscopic procedures (transgastric interventions) performed via a lumen-apposing mental stent (LAMS) in select patients with RYGB. Patients and methods  A multicenter (n = 4), retrospective study of RYGB patients with suspected luminal or extraluminal pathology, in or around the duodenum and/or excluded stomach, underwent EDGI using LAMS between December 2015 and January 2019. Results  A total of 14 patients (78.6 % women; mean age, 55.7 + 12.4 years) underwent EDGI via LAMS. Technical and clinical success rates of EDGI were 100 %. The most common transgastric interventions were diagnostic EUS of extraluminal pathology (n = 6, 42.7 %) and endoscopic biopsy of gastroduodenal luminal abnormalities (n = 5, 35.7 %). Two moderate-severity adverse events due to LAMS maldeployment occurred during EUS-JG creation (14.3 %), and each instance was successfully rescued with a bridging stent. Conclusions  A variety of gastroduodenal luminal and extraluminal disorders in RYGB patients can be effectively diagnosed and managed using EDGI via LAMS.

Effect of an External Abdominal Compression Device on Polyp Detection during Colonoscopy

AIM:

ColoWrap is an external abdominal compression device applied during colonoscopy to reduce looping and procedure time. It is unclear if a shorter procedure duration or increased abdominal pressure impacts polyp detection. We determined if use of ColoWrap affected adenoma detection rate (ADR) or detection of sessile serrated polyps (SSP) compared to sham.

MATERIALS AND METHODS:

At a single center, participants aged 40–80 were randomized to have ColoWrap or a sham device applied to the lower abdomen. Baseline characteristics, procedural factors, location of polyps, ADR and SSP detection rate (SSPDR) were compared between the groups. Multivariable logistic regression was performed to assess whether ColoWrap was associated with detection of adenomas and SSP.

RESULTS:

Of 350 participants, 175 were assigned to each arm. Overall, there were no significant differences in ADR (43% vs 40%, p = 0.52) or SSPDR (8% vs 6%, p = 0.53) between ColoWrap and sham. In sub-group analysis, there were increased odds of adenoma detection with ColoWrap in women (OR: 2.32, 95%CI: 1.21, 4.46), participants > 60 years (OR: 2.95, 95%CI: 1.43, 6.07) and those with a BMI 30–40 (OR: 3.50, 95%CI: 1.00, 12.23). Use of ColoWrap also increased ADR in the left colon (splenic flexure to rectum) (29% vs 22%; p = 0.03) and increased SSPDR in the cecum/ascending colon (6% vs 2%; p = 0.02) compared to sham.

CONCLUSION:

Use of ColoWrap during colonoscopy did not negatively impact ADR or SSPDR, and there was an apparent improvement in polyp detection in certain colon locations and patient sub-groups. These results should be interpreted with caution due to the small sample size.

Esophageal dilation with either bougie or balloon technique as a treatment for eosinophilic esophagitis: a systematic review and meta-analysis

BACKGROUND AND AIMS

Esophageal dilation is a now recognized to be an important therapeutic modality in eosinophilic esophagitis (EoE). We aimed to evaluate the safety of esophageal dilation in EoE, especially regarding perforation risk, and to examine perforation risk by dilator type.

METHODS

We conducted a systematic review of the published literature from January 1, 1950 to June 30, 2016 using PubMed, EMBASE, and Web of Science. Studies were included if they described patients with EoE who underwent elective esophageal dilation and also reported the presence or absence of at least 1 adverse event (eg, perforation, bleeding, pain, or hospitalization). We used random-effects meta-analysis to estimate the frequency of each adverse event.

RESULTS

Of 923 identified articles, 37 met inclusion criteria and represented 2034 dilations in 977 patients. On meta-analysis, postprocedure hospitalization occurred in .689% of dilations (95% confidence interval [CI], 0%-1.42%), clinically significant GI hemorrhage in .028% (95% CI, 0%-.217%), and clinically significant chest pain in 3.64% (95% CI, 1.73%-5.55%). Nine perforations were documented, at a rate of .033% (95% CI, 0%-.226%) per procedure after meta-analysis. None of the perforations resulted in surgical intervention or mortality. Most (5/9) were reported before 2009 (rate, .41% [95% CI, 0%-2.75%]); from 2009 forward the rate was .030% (95% CI, 0%-.225%). Dilation method was described in 30 studies (1957 dilations), in which 4 perforations were detected. The estimated perforation rate for bougies was .022% (95% CI, 0%-.347%) and for balloons was .059% (95% CI, 0%-.374%).

CONCLUSIONS

Perforation from esophageal dilation in EoE is rare, and there is no evidence of a significant difference in perforation risk related to dilator type. Esophageal dilation should be considered a safe procedure in EoE.

Control of inflammation decreases the need for subsequent esophageal dilation in patients with eosinophilic esophagitis

It is unknown if successful control of esophageal inflammation in eosinophilic esophagitis (EoE) decreases the need for subsequent esophageal dilation. We aimed to determine whether histologic response to topical steroid treatment decreases the likelihood and frequency of subsequent esophageal dilation. We conducted a retrospective cohort study. Patients with an incident diagnosis of EoE were included if they had an initial esophageal dilation, received topical steroids, and had a subsequent endoscopy with biopsies. The number of dilations performed in each group was determined, and histologic responders (<15 eos/hpf) were compared to nonresponders. The 55 EoE patients included (27 responders and 28 nonresponders) underwent a mean of 3.0 dilations over a median follow-up of 19 months. Responders required fewer dilations than nonresponders (1.6 vs. 4.6, P = 0.03), after adjusting for potential confounders. Despite undergoing significantly fewer dilations, responders achieved a similar increase in esophageal diameter with dilation (4.9 vs. 5.0 mm; P = 0.92). In EoE patients undergoing esophageal dilation at baseline, control of inflammation with topical steroids was associated with a 65% decrease in the number of subsequent dilations to maintain the same esophageal caliber. This suggests that inflammation control is an important goal in patients with fibrostenotic changes of EoE.

Diminishing Effectiveness of Long-Term Maintenance Topical Steroid Therapy in PPI Non-Responsive Eosinophilic Esophagitis

OBJECTIVES

While topical corticosteroids are first-line therapy for eosinophilic esophagitis (EoE), the data regarding long-term effectiveness are lacking. We aimed to determine long-term histologic and endoscopic outcomes of maintenance therapy in EoE steroid responders.

METHODS

We performed a retrospective study of adults with EoE at UNC Hospitals who had initial histologic response (<15 eos/hpf) after 8 weeks of topical steroids, and maintained on therapy. Endoscopic and the histologic data were recorded at baseline and follow-up endoscopies. Multivariable logistic regression was performed to assess loss of treatment response by steroid dose at recurrence, and Kaplan-Meier analysis to calculate durability of disease remission.

RESULTS

Of 55 EoE patients with initial response to swallowed/topical fluticasone or budesonide over a median 11.7 months, 33 had at least two follow-up EGDs. Of these patients, 61% had histologic loss of response and worse endoscopic findings. There was no difference in baseline steroid dose (P=0.55) between the groups, but those maintained on their initial dose had lower odds (OR: 0.10; 95% CI: 0.01, 0.90) of loss of response compared to those who had subsequent dose reduction. On survival analysis, 50% had loss of response to steroids by 18.5 months and 75% by 29.6 months.

CONCLUSIONS

In adult EoE steroid responders, loss of treatment response is common, and is associated with a steroid dose reduction. Routinely lowering doses for maintenance steroids may provide inferior outcomes.

Cost Utility Analysis of Topical Steroids Compared With Dietary Elimination for Treatment of Eosinophilic Esophagitis

BACKGROUND & AIMS

Topical corticosteroids or dietary elimination are recommended as first-line therapies for eosinophilic esophagitis, but data to directly compare these therapies are scant. We performed a cost utility comparison of topical corticosteroids and the 6-food elimination diet (SFED) in treatment of eosinophilic esophagitis, from the payer perspective.

METHODS

We used a modified Markov model based on current clinical guidelines, in which transition between states depended on histologic response simulated at the individual cohort-member level. Simulation parameters were defined by systematic review and meta-analysis to determine the base-case estimates and bounds of uncertainty for sensitivity analysis. Meta-regression models included adjustment for differences in study and cohort characteristics.

RESULTS

In the base-case scenario, topical fluticasone was about as effective as SFED but more expensive at a 5-year time horizon ($9261.58 vs $5719.72 per person). SFED was more effective and less expensive than topical fluticasone and topical budesonide in the base-case scenario. Probabilistic sensitivity analysis revealed little uncertainty in relative treatment effectiveness. There was somewhat greater uncertainty in the relative cost of treatments; most simulations found SFED to be less expensive.

CONCLUSIONS

In a cost utility analysis comparing topical corticosteroids and SFED for first-line treatment of eosinophilic esophagitis, the therapies were similar in effectiveness. SFED was on average less expensive, and more cost effective in most simulations, than topical budesonide and topical fluticasone, from a payer perspective and not accounting for patient-level costs or quality of life.

Cleavage of E-Cadherin Contributes to Defective Barrier Function in Neosquamous Epithelium

BACKGROUND

After ablation of Barrett's esophagus (BE), the esophagus heals with neosquamous epithelium (NSE). Despite normal endoscopic appearance, NSE exhibits defective barrier function with similarities to defects noted in the distal esophageal epithelium in patients with gastroesophageal reflux disease (GERD).

AIM

To determine whether patients with NSE, unlike patients with healthy esophageal epithelium, have C-terminal fragments (CTFs) of e-cad detectable on tissue biopsy. Secondly, to determine whether patients with NSE have elevated levels of N-terminal fragments (NTFs) of e-cad in the serum.

METHODS

Fifteen patients with ablated long-segment BE, who had healing with formation of NSE, were enrolled in this pilot study. Western blots for CTFs and NTFs were performed on biopsies of NSE. Venous blood was obtained to assess levels of NTFs. Endoscopic distal esophageal biopsies from patients without esophageal disease served as tissue controls. Control blood samples were obtained from healthy subjects.

RESULTS

Blots of NSE were successful in 14/15 patients, and all 14 (100 %) had a 35-kD CTF of e-cad, while CTFs were absent in healthy control tissues. Despite CTFs in NSE, serum NTFs of e-cad in NSE were similar to controls, p > 0.05. However, unlike healthy controls, blots of NSE also showed NTFs with molecular weights of 70-90 kD.

CONCLUSIONS

Cleavage of e-cad, as evidenced by the presence of CTFs and NTFs on biopsy, contributes to defective barrier function in NSE. However, unlike findings reported in GERD patients, serum NTFs are not elevated in NSE patients. This difference may reflect poor absorption with tissue entrapment of NTFs in previously ablated areas with poorly perfused NSE.

Renal safety of intravenous gadolinium-enhanced magnetic resonance imaging in patients awaiting liver transplantation

Renal dysfunction in cirrhosis carries a high morbidity and mortality. Given the potential risk of contrast-induced nephropathy associated with iodinated intravenous contrast used in computed tomography (CT), alternate contrast modalities for abdominal imaging in liver transplant candidates need to be examined. The purpose of this study was to examine the renal safety of magnetic resonance imaging (MRI) with gadolinium in patients awaiting liver transplantation. The study involved a retrospective analysis of 352 patients of abdominal MRI with low-dose gadobenate dimeglumine (MultiHance) (0.05 mmol/kg) in patients with cirrhosis and without renal replacement therapy at a single center during the period from 2007 to 2013. For each case, serum creatinine before and within a few days after the MRI were compared. In addition, the patients were analyzed for the development of nephrogenic systemic fibrosis (NSF), a reported complication of gadolinium in chronic kidney disease. The pre-MRI serum creatinine values ranged from 0.36 to 4.86 mg/dL, with 70 patients (20%) having values ≥ 1.5 mg/dL. A comparison of the pre- and post-MRI serum creatinine values did not demonstrate a clinically significant difference (mean change = 0.017 mg/dL; P = 0.38), including those patients with a pre-MRI serum creatinine ≥ 1.5 mg/dL. In addition, no cases of NSF were noted. In conclusion, our findings suggest that MRI with low-dose gadobenate dimeglumine (MultiHance) is a nonnephrotoxic imaging modality in liver transplant candidates, and its use can be cautiously expanded to liver transplant candidates with concomitant renal insufficiency.

Do We Know What Causes Eosinophilic Esophagitis? A Mechanistic Update

The mechanisms underlying eosinophilic esophagitis (EoE) have been intensely investigated, and significant advances have been made in understanding the pathogenesis of EoE. EoE is defined as a chronic immune/antigen-mediated disease, characterized clinically by symptoms of esophageal dysfunction and histologically by an esophageal eosinophilic infiltrate. In this paper, we will review the current knowledge of EoE pathophysiology based on both animal and human data and discuss possible etiologic mechanisms from the genetic and environmental perspectives. EoE is a Th2-predominant inflammatory process triggered by allergens. Proinflammatory cytokines and chemokines recruit eosinophils and other effector cells, such as mast cells, into the esophageal epithelium, where they cause direct damage and promote esophageal remodeling. The genetic expression profile of EoE has been described, and several single nucleotide polymorphisms have been identified and associated with EoE. While this genetic contribution is important, it is difficult to postulate that EoE is primarily a genetic disease. Given the rapid epidemiologic changes in the incidence and prevalence of EoE over the past two decades, environmental factors may be the driving force. While it is not known what causes EoE in an individual patient at a specific time, the current hypothesis is that there is a complex interaction between genetic factors and environmental exposures that remains to be elucidated.

Epidemiology of Barrett's Esophagus and Esophageal Adenocarcinoma

Barrett's esophagus (BE) is the precursor to esophageal adenocarcinoma (EAC), a disease with increasing burden in the Western world, especially in white men. Risk factors for BE include obesity, tobacco smoking, and gastroesophageal reflux disease (GERD). EAC is the most common form of esophageal cancer in the United States. Risk factors include GERD, tobacco smoking, and obesity, whereas nonsteroidal antiinflammatory drugs and statins may be protective. Factors predicting progression from nondysplastic BE to EAC include dysplastic changes on esophageal histology and length of the involved BE segment. Biomarkers have shown promise, but none are approved for clinical use.

Limiting brain and lung damage after coronary artery bypass grafting: an alternative to conventional coronary artery bypass graft

The development of coronary artery bypass graft (CABG) for the treatment of coronary heart disease has resulted in reduced morbidity and mortality compared with medical therapy. Even with the rapid development of improved percutaneous interventions, CABG remains an important approach for treating patients with advanced coronary heart disease. However, recent studies and commentary reporting an alarmingly high incidence of subtle, cognitive decline following CABG have generated questions about whether these adverse outcomes could be lessened. Even after considerable study, there is no consensus as to the cause of brain and lung injury after CABG and cardiopulmonary bypass, nor an agreed upon, mechanistic approach to study its prevention. The potential causes of these adverse outcomes and a simple approach are described, involving the use of the cannulae, biventricular pulsatile flow pump, and a blood substitute to optimize the perfusion of brain and alveolar cells, minimize systemic microembolization, and limit post-CABG cognitive decline.

Testing neonate-infant membrane oxygenators with the University of Texas neonatal pulsatile cardiopulmonary bypass system in vitro

Neurologic complications are already well documented after cardiopulmonary bypass (CPB) procedures in neonates and infants. Physiologic pulsatile flow CPB systems may be the alternative to the currently used steady-flow CPB circuits. In addition to the pulsatile pump, a membrane oxygenator should be chosen carefully, because only a few membrane oxygenators are suitable for physiologic pulsatile flow. We have tested four different types of neonate-infant membrane oxygenators for physiologic pulsatility with The University of Texas neonate-infant pulsatile CPB system in vitro. Evaluation criteria were based on mean ejection time, extracorporeal circuit (ECC) pressure, and upstroke of dp/dt. The results suggested that the Capiox 308 hollow-fibre membrane oxygenator produced the best physiologic pulsatile waveform according to the ejection time, ECC pressure, and the upstroke of dp/dt. The Minimax Plus and Masterflo Infant hollow-fibre membrane oxygenators also produced adequate pulsatile flow. Only the Variable Prime Cobe Membrane Lung (VPCML) Plus flat-sheet membrane oxygenator failed to reach the criteria for physiologic pulsatility. Depending on the oxygenator used, the lowest priming volume of the infant CPB circuit was 415 ml and the highest 520 ml.

The type of aortic cannula and membrane oxygenator affect the pulsatile waveform morphology produced by a neonate-infant cardiopulmonary bypass system in vivo

Although the debate still continues over the effectiveness of pulsatile versus nonpulsatile perfusion, it has been clearly proven that there are several significant physiological benefits of pulsatile perfusion during cardiopulmonary bypass (CPB) compared to nonpulsatile perfusion. However, the components of the extracorporeal circuit have not been fully investigated regarding the quality of the pulsatility. In addition, most of these results have been gathered from adult patients, not from neonates and infants. We have designed and tested a neonate-infant pulsatile CPB system using 2 different types of 10 Fr aortic cannulas and membrane oxygenators in 3 kg piglets to evaluate the effects of these components on the pulsatile waveform produced by the system. In terms of the methods, Group 1 (Capiox 308 hollow-fiber membrane oxygenator and DLP aortic cannula with a very short 10 Fr tip [n = 2]) was subjected to a 2 h period of normothermic pulsatile CPB with a pump flow rate of 150 ml/kg/min. Data were obtained at 5, 30, 60, 90, and 120 min of CPB. In Group 2 (Capiox 308 hollow-fiber membrane oxygenator and Elecath aortic cannula with a very long 10 Fr tip [n = 7]) and Group 3 (cobe VPCML Plus flat sheet membrane oxygenator and DLP aortic cannula with a very short 10 Fr tip [n = 7]), the subjects' nasopharyngeal temperatures were reduced to 18 degrees C followed by 1 h of deep hypothermic circulatory arrest (DHCA) and then 40 min rewarming. Data were obtained during normothermic CPB in the pre- and post-DHCA periods. The criteria of pulsatility evaluations were based upon pulse pressure (between 30 and 40 mm Hg), aortic dp/dt (greater than 1000 mm Hg/s), and ejection time (less than 250 ms). The results showed that Group 1 produced flow which was significantly more pulsatile than that of the other 2 groups. Although the same oxygenator was used for Group 2, the quality of the pulsatile flow decreased when using a different aortic cannula. Group 3 did not meet any of the criteria for physiologic pulsatility. In conclusion these data suggest that in addition to a pulsatile pump, the aortic cannula and the membrane oxygenator must be chosen carefully to achieve physiologic pulsatile flow during CPB.

Error associated with the choice of an aortic cannula in measuring regional cerebral blood flow with microspheres during pulsatile CPB in a neonatal piglet model

The effectiveness of an infant pulsatile cardiopulmonary bypass (CPB) system on maintaining regional cerebral blood flow (CBF) using two different types of aortic cannulae in 3 kg piglets has been investigated. The University of Texas Neonatal Pulsatile Pump was used with either a DLP (Group I, n = 6) or an Elecath (Group II, n = 7) 10Fr aortic cannula. In all the subjects, nasopharyngeal temperature was reduced to 18 degrees C, followed by 1 hr of deep hypothermic circulatory arrest (DHCA), then 45 min of rewarming. During cooling and rewarming, alpha-stat blood gas management was used. The radionuclide labeled microsphere technique was used to determine blood flows in the cerebellum, basal ganglia, brainstem, right and left hemispheres, as well as global CBF (ml/100 g/min). When the DLP aortic cannula was used, regional and global CBF appeared to be higher pre- and post DHCA. In both groups regional CBF was significantly decreased following DHCA. Although better pulsatile flow was attained using the DLP cannula and this may have resulted in higher regional CBF, these results must be interpreted in light of the large standard deviations noted when this cannula was chosen for the studies. These results demonstrate the importance of choosing an appropriate aortic cannula for measuring regional CBF with a pulsatile neonate-infant CPB system.

Enhancement of brain p0(2) during cardiopulmonary bypass using a hyperosmolar oxygen carrying solution

During the past decade a new syndrome has been recognized: cerebral hypoxia secondary to cardiopulmonary bypass, resulting in impairment of cognitive memory. The incidence of the syndrome appears to be no less that 30% in patients over 65 years of age undergoing cardiac surgery. There are several factors contributing to hypoxia produced by cardiopulmonary bypass. One of these factors is crystalloid pump prime and replacement solutions devoid of (1) oxygen carrying capacity and (2) devoid of protein and its colloid osmotic pressure. This shortcoming of cardiopulmonary crystalloid solutions is partially responsible for two of the three major pathologic effects of cardiopulmonary bypass: (1) hypoxia (2) interstitial fluid accumulation (anasarca, water-logging, edema). This report describes an oxygen carrying hyperosmolar solution which enhances brain p0(2) and diminishes interstitial fluid accumulation. This blood substitute consists of perfluorcarbons and saccharides, but could consist of a hemoglobin variant plus hyperosmolar ingredients other than saccharides. The advantage of a perfluorochemical is its ability to access small channels and to be centrifuged off the patient post-operatively with a cell saver. The advantage of saccharides is that they can be metabolized by the patient for energy, and they produce a moderate diuresis coming off bypass.

Regional blood flow during pulsatile cardiopulmonary bypass and after circulatory arrest in an infant model

BACKGROUND

Pulsatile perfusion systems have been proposed as a means of improving end-organ perfusion during and after cardiopulmonary bypass. Few attempts have been made to study this issue in an infant model.

METHODS

Neonatal piglets were subjected to nonpulsatile (n = 6) or pulsatile (n = 7) cardiopulmonary bypass and 60 minutes of circulatory arrest. Cerebral, renal, and myocardial blood flow measurements were obtained at baseline, on bypass before and after circulatory arrest, and after bypass.

RESULTS

Cerebral blood flow did not differ between groups at any time and was diminished equally in both groups after circulatory arrest. Renal blood flow was diminished in both groups during bypass but was significantly better in the pulsatile group than in the nonpulsatile group prior to, but not after, circulatory arrest. Myocardial blood flow was maintained at or above baseline in the pulsatile group throughout the study, but in the nonpulsatile group, it was significantly lower than baseline during CPB prior to circulatory arrest and lower compared with baseline and with the pulsatile group 60 minutes after CPB.

CONCLUSIONS

Pulsatile bypass does not improve recovery of cerebral blood flow after circulatory arrest, may improve renal perfusion during bypass but does not improve its recovery after ischemia, and may have beneficial effects on myocardial blood flow during bypass and after ischemia compared with nonpulsatile bypass in this infant model.

Changes in brain pH, PO2, PCO2, cerebral blood flow, and blood gases induced by a hyperosmolar oxyreplete hemosubstitute during cardiopulmonary bypass

Eleven goats (mean weight, 69 +/- 16 kg) underwent 5 hrs of normothermic nonpulsatile cardiopulmonary bypass (CPB) using as priming fluid either a Ringer's based crystalloid priming solution (CP, n = 5) of a hyperosmolar oxyreplete hemosubstitute (HS, n = 6). The HS contained 20% w/v perfluorocarbon (perfluorodecalin), its osmolarity was 800-900 mOsm/1, and the administered dose of perfluorocarbon was 30-50 ml/kg. Otherwise, the experimental procedure was identical for both groups. PaCO2 was maintained above 35 mmHg and blood flow rate at 65 ml/kg. Brain tissue pH, PO2, and PCO2, cerebral blood flow (CBF), arterial and venous blood gases, and other systemic variables were monitored. During CPB, PVO2 and brain tissue PO2 were increased significantly in the HS group. The CBF per kilogram of weight also was significantly higher in the HS group. Metabolic acidosis developed in both groups and, surprisingly, brain tissue pH and pHV were lower in the HS group. The mean values of PVCO2 and brain tissue PCO2 indicate that brain tissue hypercapnia also occurred in both groups. The HS provided long-term stability and compatibility with electrolytes, and did not cause major complications or allergic reactions during CPB. Perfluorocarbon based HSs improve tissue oxygenation, eliminate the risk of infection due to homologous transfusions, do not require blood type matching, have a shelf life longer than that of blood, and, therefore, they can be an important factor in diminishing the incidence of complications after CPB.

A single pulsatile pump for total biventricular cardiac support using patient lung ventilation

An extracorporeal pulsatile heart pump has been modified to render biventricular cardiac support while maintaining automatic volume balance between the left and right sides. The device consists of two independent fluid circuits, externally valved and compressed by a common pusher plate configuration. Because the pusher plate compresses both circuits simultaneously, the volume-heavy side is unloaded via larger stroke volumes until the two sides achieve a balanced stroke volume. The process is automatic from beat-to-beat and is not dependent upon external pressure or flow transducers to maintain equilibrium. Two in vivo studies in pigs weighing 25 kg have demonstrated the feasibility of the concept, with physiologic aortic and pulmonary artery flow during 2 hr of ac-induced ventricular fibrillation and oscillatory ventilator support via left atrium-to-aorta and right atrium-to-pulmonary artery cannulation. Efforts to scale up to human adult size requirements have resulted in in vitro outputs of up to 7.0 L/min in each circuit.

Design and performance of a physiologic pulsatile flow neonate-infant cardiopulmonary bypass system

The authors have designed an alternative infant cardiopulmonary bypass (CPB) system using the University of Texas neonatal pulsatile pump, which produces physiologic pulsatile flow and allows a low priming volume. This system has been tested with normothermic CPB (n = 8), and deep hypothermic circulatory arrest (n = 14) in 3 kg piglets. Data obtained during these studies suggest that this system can produce flow characteristics that approximate normal physiologic values. Unlike other pulsatile pumps, this pump can produce a very small stroke volume, ranging from 0.5 to 7.1 ml with a pump rate of 120 beats/min. These stroke volumes correspond to our target value of 1 ml/kg body weight. This system is designed to cause minimal hemodilution and minimal exposure of blood to foreign surface areas. The pump does not produce negative pressure, and therefore the venous reservoir is not essential, and only a cardiotomy reservoir is required. Conclusions after in vivo testing are, first, that physiologic pulsatile flow can be achieved readily with this system using a 10 Fr aortic cannula in 3 kg piglets; and second, that a significant reduction in priming volume and hemodilution can be obtained using this system.

Design of a physiologic pulsatile flow cardiopulmonary bypass system for neonates and infants

Cardiopulmonary bypass surgical techniques that allow a surgeon to operate on the infant's heart use an extracorporeal circuit consisting of a pump, oxygenator, arterial and venous reservoirs, cannulae, an arterial filter, and tubing. The extracorporeal technique currently used in infants and neonates is sometimes associated with neurologic damage. We are developing a modified cardiopulmonary bypass system for neonates that has been tested in vitro and in one animal in vivo. Unlike other extracorporeal circuits which use steady flow, this system utilizes pulsatile flow, a low prime volume (500 ml) and a closed circuit. During in vitro experiments, the pseudo patient's mean arterial pressure was kept constant at 40 mmHg and the extracorporeal circuit pressure did not exceed a mean pressure of 200 mmHg. In our single in vivo experiment, the primary objective was to determine whether physiologic pulsatility with a 10 F (3.3 mm) aortic cannula could be achieved. The results suggest that this is possible.

Monitoring of blood gases during prolonged experimental cardiopulmonary bypass and their relationship to brain pH, PO2, and PCO2

Eight adult goats under went 5 hr of normothermic cardiopulmonary bypass (CPB) with pulsatile (n = 3) and nonpulsatile flow (n = 5). PaCO2 was maintained at 30-40 mmHg and blood flow rate at 50 ml/min/kg. Brain tissue pH, PO2, and PCO2, arterial and venous blood gases, and other systemic variables were monitored. No significant differences in brain electrochemistry between pulsatile and nonpulsatile perfusion were observed owing to the large variability of the results and the small number of experiments. The overall data for brain tissue pH, PO2, and PCO2 were analyzed and compared to the results of arterial and venous pH, PO2, and PCO2. Brain acidosis developed at the onset of bypass, and the values for brain tissue pH dissociated from those of blood pH, suggesting that hemodilution and the initial body response to CPB are involved in its development. Brain hypercapnia also developed during CPB, the values of brain tissue PCO2 dissociated from those of blood PCO2, and brain hypercapnia appears to be secondary to brain acidosis. Brain tissue PO2 closely followed the values of PvO2, suggesting that PvO2 can be an indicator of brain tissue PO2 during normothermic CPB and must be monitored during the procedure. Brain tissue acidosis is evidently related to neurologic dysfunction after CPB, and must be addressed. Replacement of the priming solution with whole blood or artificial blood, reduction of the priming volume, and application of vigorous pulsatile flow appear feasible interventions to mitigate brain tissue acidosis during CPB.

Hemodialysis: evidence of enhanced molecular clearance and ultrafiltration volume by using pulsatile flow

We describe several in vitro experiments showing evidence that pulsatile flow hemodialysis enhances ultrafiltration volume and molecular clearance as compared with steady flow hemodialysis. A new pulsatile pump and a conventional roller pump were compared using different hollow fiber dialyzers and a simulated blood solution containing urea, aspartame and vitamin B-12 at different flow rates and configurations. Ultrafiltration volume and concentration of urea, aspartame and B-12 were measured and molecular clearance (K) calculated. Ultrafiltration volume markedly increased with pulsatile flow. After 10 min K for urea with pulsatile flow was higher in all experiments even when ultrafiltration was prevented. Clearance of aspartame and B-12 also increased with pulsatile flow. We propose three mechanisms by which pulsatile flow is more efficient than steady flow hemodialysis: greater fluid energy, avoidance of molecular channeling and avoidance of membrane layering. We hypothesize that using pulsatile flow in hemodialysis can significantly shorten the duration of dialysis sessions for most of the patients, and consequently reduce the duration of the procedure and its cost.

Achievement of physiologic pulsatile flow on cardiopulmonary bypass with a 24 French cannula

In 1990, the NIH formally recognized the need for investigation of the problem of damaging the effects of cardiopulmonary bypass, issuing RFA HL-90-12-H, which emphasized production of neurologic defects in the very young and the elderly. The authors were at that time involved in comparison of pulsatile flow to steady flow cardiopulmonary bypass in large ungulates. The world literature recognizes five damaging effects of steady flow cardiopulmonary bypass that can be mitigated by pulsatile flow: metabolic acidosis, interstitial fluid accumulation, elevated systemic vascular resistance, arteriovenous shunting, and impaired brain oxygenation. To maximize the beneficial effect of pulsatile flow, however, it is necessary that its morphology be physiologic. It has been stated in the past that this goal may not be possible using standard size aortic cannulas. The purpose of this publication is to describe a method by which this feat has been achieved in 150 pound ungulates undergoing prolonged cardiopulmonary bypass.

Tubing spallation in extracorporeal circuits. An in vitro study using an electronic particle counter

The roller pump is the most common pumping device used in extracorporeal circulation (ECC). The interaction between the roller and tubing causes tubing spallation. Spallation has been associated with complications in ECC. Previous spallation studies present mixed results, including a decrease in the number of circulating particles. The objective of this work is to perform an in vitro study of tubing spallation which elucidates the causes of the particle sequestration, and the effect of tubing material, blood flow rate and duration of the procedure upon spallation. A sampling method minimizing background counts was devised. Silicone and PVC tubing were tested under normal and tight occlusion pressure at typical cardiopulmonary bypass and hemodialysis flow rates, for circulating times up to 4 h. Occlusion pressure and flow rate highly influenced the amount of spallation produced. Particle sequestration was noted and aggregation of the plastic particles was demonstrated. We conclude that, at least in vitro, aggregation causes the decrease in the particle counts and the misleading results obtained in most spallation studies using a Coulter counter.

Comparison of a steady flow pump to a preload responsive pulsatile pump in left atrial-to-aorta bypass in canines

A unique preload responsive pulsatile pump was compared to a centrifugal pump in total cardiac support in 25-kg canines (n = 6, each group) in the left atrial-to-aorta mode during 5 h of ventricular fibrillation. With steady flow, there was immediate drop in output from 2.1 +/- 1.0 L/min to 1.4 +/- 0.3 L/min, followed by further reduction to 0.9 +/- 0.2 L/min during 5 h of ventricular fibrillation. With a pulsatile pump, there was no significant reduction from control of 2.4 +/- 0.6 L/min and no decline during 5 h of ventricular fibrillation. With steady flow, systemic vascular resistance (SVR) rose significantly from 1,762 dyne-s-cm-5 immediately on pump to 3,013 dyne-s-cm-5 at 5 h. With physiologic pulsatile flow, significant elevation of SVR did not occur. When stressed, due to diminished left atrial return, the centrifugal pump displayed line chatter and streaks of microbubbles, whereas the pulsatile pump did not. Crystalloid volume replacement with the centrifugal pump was 6.5 +/- 1.9 L, and with the preload responsive pulsatile pump, 5.6 +/- 1.3 L. It is concluded that in the left atrial-to-aorta mode during 5 h of ventricular fibrillation and with comparable volume replacement, total cardiac support of canines is associated with lower SVR with physiologic pulsatile flow and is not accompanied by line chatter and cavitation with this preload responsive pump.

Preload-responsive, pulsatile-flow, externally valved pump: cardiopulmonary bypass

Currently two pumps are used for cardiopulmonary bypass, the roller pump and the centrifugal or vortex pump. Both are steady-flow pumps. The procedure of cardiopulmonary bypass possesses a finite morbidity and mortality. The degree to which steady flow is responsible for this morbidity and mortality remains to be clarified, but investigators have established the fact that a physiologic degree of pulsatile flow must be achieved before its beneficial results, such as normal systemic resistance and absence of lactate production, can be demonstrated. Availability of a satisfactory pulsatile pump for cardiopulmonary bypass has been a problem in the past but the pump presented here may satisfy this need. It produces physiologic pulsatility with rate dependent ejection time equal to or less than that of humans (413 microseconds minus 1.7 times heart rate), and it is preload-responsive, varying its pumping rate and output with filling pressure. The pump is externally valved to minimize hemolysis, which has been demonstrated in two laboratory studies to be significantly less than with the roller pump. It produces pulsatile flow through membrane oxygenators. The pump is thought to have potential for several clinical applications in addition to (1) pulsatile-flow cardiopulmonary bypass, including (2) left, right, or combined transthoracic QRS synchronized ventricular assist, (3) femoral vein to femoral artery QRS synchronized left ventricular assist, (4) adult or infant ECMO, (5) pulsatile flow hemodialysis. In the latter, spallation and embolization of hemodialysis tubing particles should not be a problem as has proved to be the case with the present hemodialysis pump.

Difference in degree of A-V block and QS2 abbreviation of ouabain digoxin and digitoxin in cats

Six trained domestic cats received a spectrum of polar to nonpolar cardiac glycosides: ouabain, digoxin or digitoxin with medication free intervals of four weeks. Significant (P less than 0.01) rate reduction (-19 +/- 8%) and prolongation of PR interval (+13 +/- 5%) occurred with ouabain and with digoxin (-18 +/- 5% and +13 +/- 3%) but not with digitoxin (-6 +/- 4% and +6 +/- 5%). However, rate corrected QS2 abbreviation was greater with digitoxin (-13 +/- 3%) than with ouabain (-8 +/- 3%) or digoxin (-10 +/- 5%). The findings indicate that in cats the polar cardiac glycosides ouabain and digoxin produce greater prolongation of A-V conduction while the nonpolar glycoside digitoxin produces greater abbreviation of QS2. Previously this finding was reported by the authors in guinea-pigs and in rabbits and has since been reported in intact rats, dogs, and in man by other authors. Investigators using nonintact subjects have not been able to demonstrate the finding. The differences may have clinical significance and suggest new insight into structural/activity relationships within the cardiac glycoside family.

Clinical implications of differences in pharmacodynamic action of polar and nonpolar cardiac glycosides

The principal effects of cardiac glycosides probably can be classified as parasympathomimetic or sympathomimetic. Data from animals and from man suggest that polar cardiac glycosides, such as ouabain and digoxin, possess greater parasympathomimetic (vagal) cardiac effect for a given amount of sympathomimetic (positive inotropic) cardiac effect than do less polar cardiac glycosides, such as digitoxin. Polar glycosides therefore offer some advantage in uncomplicated paroxysmal atrial tachycardia and in uncomplicated atrial flutter and atrial fibrillation when the principal desired effect is reduction in the number of atrial impulses reaching the ventricles or conversion to normal sinus rhythm. Non-polar glycosides offer an advantage when positive inotropicity is desired but when there is some degree of atrioventricular block or when inappropriate sinus bradycardia or anorexia, nausea, or vomiting are present. Ecotopic impulse formation when due to cardiac glycosides is a toxic manifestation of excessive sympathomimetic effect, but is aggravated by vagal-induced sinus bradycardia, so that both parasympathomimetic and sympathomimetic capability of cardiac glycosides must be considered when dealing with myocardial electrical instability.

Pharmacodynamic distinctions between ouabain, digoxin and digitoxin

Current pharmacologic texts recognize no significant pharmacodynamic differences between the various cardiac glycosides. To reconsider this concept, a special recording device was constructed so that electrocardiograms and phonocardiograms could be obtained in small mammals without anesthesia or premedication, and a spectrum of cardiac glycosides was studied. Utilizing guinea-pigs, cardiac rate reduction of 20% was sought and achieved with 0.07 mg/kg ouabain, 0.34 mg/kg digoxin and 1.12 mg/kg digitoxin. With comparable rate reduction, digitoxin produced significantly greater shortening of electro-mechanical systole than did ouabain or digoxin (P less than 0.05). Other authors have shown that cardiac glycosides produce slowing of cardiac rate prior to onset of positive inotropic effect. Therefore it is probable that for a given amount of vagal effect (sinoatrial slowing) digitoxin possesses greater positive inotropic effect (abbreviation of electromechanical systole) in guinea-pigs than do ouabain or digoxin. A review of the literature suggests that the same holds true for humans.