Transnasal Humidified Rapid Insufflation Ventilatory Exchange in Endoscopic Esophageal Surgery

OBJECTIVES

Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) describes apneic oxygenation using humidified high flow nasal-cannula oxygen. Although it has been described as a sole mode of oxygenation in endoscopic laryngotracheal surgery, its use in endoscopic esophageal surgery under general anesthesia with neuromuscular paralysis has not previously been described. The objective of this study is to assess the safety and efficacy of THRIVE in esophagology.

METHODS

We conducted a retrospective review of adult patients undergoing esophageal procedures under general anesthesia who were oxygenated using THRIVE at two academic institutions. Demographic, clinical, and anesthesiologic data were collected and analyzed.

RESULTS

14 cases performed from March 2021 to March 2022 met inclusion criteria. 13/14 (92.9%) of patients were able to maintain oxygenation throughout the entirety of their procedure. The mean apneic time was 17.9 minutes with a maximum of 32 minutes. One patient required "rescue" intubation due to failure to maintain oxygenation. Excluding the sole THRIVE failure, the median SpO2 at the conclusion of surgery was 99% (range 94-100%). A linear regression model yielded an increase in EtCO2 of 0.95 mmHg/min or 0.127 kPa/min. SpO2 was negatively associated with both tobacco pack-year smoking history (R2 = 0.343, P = .014) and BMI (R2 = 0.238, P = .038).

CONCLUSION

THRIVE is a feasible, safe, and efficacious means of apneic oxygenation for patients undergoing esophageal endoscopic surgery under general anesthesia with neuromuscular paralysis, which may be particularly beneficial in patients with airway stenosis, as post-intubation changes can have severe clinical implications for this patient population. Obese patients and tobacco smokers may be at increased risk of oxygen desaturation when using THRIVE.

Low Pressure Low Frequency Jet Ventilation: Techniques, Safety and Complications

OBJECTIVE

Manual jet ventilation is a specialized oxygenation and ventilation technique that is not available in all facilities due to lack of technical familiarity and fear of complications. The objective is to review our center's 15 year experience with low pressure low frequency jet ventilation (LPLFJV).

METHODS

Retrospective review of procedures utilizing LPLFJV from 2005 to 2019 were performed collecting patient demographic, surgery type and complications. Fisher exact test, Chi square, and t-test were used to determine statistical significance.

RESULTS

Four hundred fifty-seven patients underwent a total of 891 microlaryngeal surgeries-279 cases for voice disorders, 179 for lesions, and 433 for airway stenosis. The peak jet pressure for all cases did not exceed 20 psi and average peak pressure for the last 100 procedures in this case series was 14.9 ± 4.6 psi. The average lowest oxygen saturation for all cases was 95% ± 0.6%. Brief intubation was required in 154 cases (17%). Surgical duration was significantly longer for cases requiring intubation P < .001. The need for intubation was not associated with smoking or cardiopulmonary disease, but was strongly associated with body mass index (BMI). Intubation rates were 7% for normal weight (BMI < 25, N = 216), 13% for overweight (BMI 25-30, N = 282), 24% for obese (BMI 30-40, N = 342), and 37% for morbidly obese (BMI > 40, N = 52) patients. Three patients developed respiratory distress in the recovery unit and 2 patients required intubation.

CONCLUSION

LPLFJV assisted by intermittent endotracheal intubation is an exceedingly safe and effective intraoperative oxygenation and ventilationmodality for a broad variety of laryngeal procedure.

Using NSQIP Data to Reduce Institutional Postoperative Pneumonia Rates in Non-ICU Patients: A Plan-Do-Study-Act Approach

BACKGROUND

The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) is a program designed to measure and improve surgical care quality. In 2015, the study institution formed a multidisciplinary team to address the poor adult postoperative pneumonia performance (worst decile).

STUDY DESIGN

The study institution is a 450+ bed tertiary care center that performs 12,000+ surgical procedures annually. From January 2016 to December 2019, the institution abstracted surgical cases and assigned postoperative pneumonia as a complication per the NSQIP operations manual. Using a plan-do-study-act approach, a multidisciplinary postoperative pneumonia prevention team implemented initiatives regarding incentive spirometry education, anesthetic optimization, early mobility, and oral care. The team measured the initiatives' success by analyzing semiannual reports (SAR) provided by the ACS NSQIP and regional adjusted percentile rankings provided by the Georgia Surgical Quality Collaborative (GSQC).

RESULTS

The 2015 SAR postoperative pneumonia rate was 4.20% (odds ratio [OR] 3.86, confidence interval [CI] 2.92-5.11). After project initiation, the postoperative pneumonia rates decreased for all NSQIP cases, from 2.51% (OR 2.67, CI 1.89-3.77) in 2016 to 2.08% (OR 2.61, CI 1.82-3.74) in 2017, to 0.85% (OR 1.10, CI 0.69-1.75) in 2018, and then increased slightly to 1.14% (OR 1.27, CI 0.84-1.92) in 2019. The institution's adjusted percentile regional rank of participating regional ACS NSQIP hospitals' postoperative pneumonia rate improved from 14/14 (July 2015-June 2016) to 6/14 (July 2018-June 2019).

CONCLUSIONS

The multidisciplinary postoperative pneumonia prevention team successfully decreased the postoperative pneumonia rate, therefore improving surgical patients' outcomes. Furthermore, this quality improvement project also saved valuable revenue for the hospital.

Endothelin-1 contributes to the progression of renal injury in sickle cell disease via reactive oxygen species

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) is increased in patients with sickle cell disease and may contribute to the development of sickle cell nephropathy. The current study was designed to determine whether ET-1 acting via the ETA receptor contributes to renal injury in a mouse model of sickle cell disease.

EXPERIMENTAL APPROACH

Adult, humanized HbSS (homozygous for sickle Hb) mice had increased ET-1 mRNA expression in both the cortex and the glomeruli compared with mice heterozygous for sickle and Hb A (HbAS controls). In the renal cortex, ETA receptor mRNA expression was also elevated in HbSS (sickle) mice although ETB receptor mRNA expression was unchanged. Ligand binding assays confirmed that sickle mice had increased ETA receptors in the renal vascular tissue when compared with control mice.

KEY RESULTS

In response to PKC stimulation, reactive oxygen species production by isolated glomeruli from HbSS sickle mice was increased compared with that from HbSA controls, an effect that was prevented by 1 week in vivo treatment with the selective ETA antagonist, ABT-627. Protein and nephrin excretion were both elevated in sickle mice, effects that were also significantly attenuated by ABT-627. Finally, ETA receptor antagonism caused a significant reduction in mRNA expression of NADPH oxidase subunits, which may contribute to nephropathy in sickle cell disease.

CONCLUSIONS AND IMPLICATIONS

These data support a novel role for ET-1 in the progression of sickle nephropathy, specifically via the ETA receptor, and suggest a potential role for ETA receptor antagonism in a treatment strategy.

Updated Mechanisms of Sickle Cell Disease-Associated Chronic pain

Sickle cell disease (SCD), a hemoglobinopathy, causes sickling of red blood cells, resulting in vessel blockage, stroke, anemia, inflammation, and extreme pain. A vast majority of SCD patients experience pain on a chronic basis, and many turn to opioids to provide limited relief. The side effects that come with chronic opioid use push for research into understanding the specific mechanisms of SCD-associated chronic pain. Current advances in SCD-associated pain have focused on alterations in the pain pathway including nociceptor sensitization and endogenous pain inducers. This article reviews the underlying pathophysiology of SCD, potential pain mechanisms, current treatments and their mechanism of action, and future directions of SCD-associated pain management. The information provided could help propel research in SCD-associated chronic pain and uncover novel treatment options for clinicians.

Receptor-mediated delivery of engineered nucleases for genome modification

Engineered nucleases, which incise the genome at predetermined sites, have a number of laboratory and clinical applications. There is, however, a need for better methods for controlled intracellular delivery of nucleases. Here, we demonstrate a method for ligand-mediated delivery of zinc finger nucleases (ZFN) proteins using transferrin receptor-mediated endocytosis. Uptake is rapid and efficient in established mammalian cell lines and in primary cells, including mouse and human hematopoietic stem-progenitor cell populations. In contrast to cDNA expression, ZFN protein levels decline rapidly following internalization, affording better temporal control of nuclease activity. We show that transferrin-mediated ZFN uptake leads to site-specific in situ cleavage of the target locus. Additionally, despite the much shorter duration of ZFN activity, the efficiency of gene correction approaches that seen with cDNA-mediated expression. The approach is flexible and general, with the potential for extension to other targeting ligands and nuclease architectures.

Attenuation of hematoma size and neurological injury with curcumin following intracerebral hemorrhage in mice

OBJECT

Intracerebral hemorrhage (ICH) is associated with significant morbidity and mortality. Acute hematoma enlargement is an important predictor of neurological injury and poor clinical prognosis; but neurosurgical clot evacuation may not be feasible in all patients and treatment options remain largely supportive. Thus, novel therapeutic approaches to promote hematoma resolution are needed. In the present study, the authors investigated whether the curry spice curcumin limited neurovascular injury following ICH in mice.

METHODS

Intracerebral hemorrhage was induced in adult male CD-1 mice by intracerebral administration of collagenase or autologous blood. Clinically relevant doses of curcumin (75-300 mg/kg) were administered up to 6 hours after ICH, and hematoma volume, inflammatory gene expression, blood-brain barrier permeability, and brain edema were assessed over the first 72 hours. Neurological assessments were performed to correlate neurovascular protection with functional outcomes.

RESULTS

Curcumin increased hematoma resolution at 72 hours post-ICH. This effect was associated with a significant reduction in the expression of the proinflammatory mediators, tumor necrosis factor-α, interleukin-6, and interleukin-1β. Curcumin also reduced disruption of the blood-brain barrier and attenuated the formation of vasogenic edema following ICH. Consistent with the reduction in neuroinflammation and neurovascular injury, curcumin significantly improved neurological outcome scores after ICH.

CONCLUSIONS

Curcumin promoted hematoma resolution and limited neurological injury following ICH. These data may indicate clinical utility for curcumin as an adjunct therapy to reduce brain injury and improve patient outcome.

A new sickling variant 'Hb S-Wake β[(Glu6Val-Asn139 Ser)]' found in a compound heterozygote with Hb S β(Glu6Val) coinherited with homozygous α-thalassemia-2: phenotype and molecular characteristics

We report the case of a 14-year-old African-American boy who was diagnosed with sickle cell disease. Laboratory tests showed that the patient was a compound heterozygote for a novel Hb variant with a double mutation detected on β(S) allele, Hb S βGlu6Val, and βAsn139Ser substitution, i.e. a β-chain variant named 'Hb S-Wake'. The patient also carried a single Hb S mutation in trans allele, leading to Hb SS-Wake disease. He had coinherited homozygous α(+)-thalassemia (-α(3.7)/-α(3.7)) simultaneously which resulted in multiple globin gene abnormalities.

Curcumin attenuates cerebral edema following traumatic brain injury in mice: a possible role for aquaporin-4?

Traumatic brain injury is a devastating neurological injury associated with significant morbidity and mortality. Medical therapies to limit cerebral edema, a cause of increased intracranial hypertension and poor clinical outcome, are largely ineffective, emphasizing the need for novel therapeutic approaches. In the present study, pre-treatment with curcumin (75, 150 mg/kg) or 30 min post-treatment with 300 mg/kg significantly reduced brain water content and improved neurological outcome following a moderate controlled cortical impact in mice. The protective effect of curcumin was associated with a significant attenuation in the acute pericontusional expression of interleukin-1beta, a pro-inflammatory cytokine, after injury. Curcumin also reversed the induction of aquaporin-4, an astrocytic water channel implicated in the development of cellular edema following head trauma. Notably, curcumin blocked IL-1beta-induced aquaporin-4 expression in cultured astrocytes, an effect mediated, at least in part, by reduced activation of the p50 and p65 subunits of nuclear factor kappaB. Consistent with this notion, curcumin preferentially attenuated phosphorylated p65 immunoreactivity in pericontusional astrocytes and decreased the expression of glial fibrillary acidic protein, a reactive astrocyte marker. As a whole, these data suggest clinically achievable concentrations of curcumin reduce glial activation and cerebral edema following neurotrauma, a finding which warrants further investigation.

Anesthesia drugs, immunity, and long-term outcome

PURPOSE OF REVIEW

We provide an overview of the immunological effects of commonly used anesthetic drugs and highlight their potential impact on long-term outcome after surgery.

RECENT FINDINGS

Clinical trials provide preliminary evidence that the perioperative process can influence long-term patient outcome. Immunology may begin to elucidate the biology of this safety concern and open new therapeutic opportunities. In this context, awareness of the immunological properties of drugs administered in the perioperative period may assist in their deliberate use to modulate this risk. Statins, beta-blockers, and clonidine can potentially improve long-term cardiac risk. Volatile anesthetics appear to suppress effector functions of both the innate and adaptive immunity, assist tumor growth in animal models, and facilitate aggregation of certain neurodegenerative disease proteins. Local anesthetics block neurons, but are also potent antiinflammatory drugs. Morphine has recognized immunosuppressive functions, which the newer, synthetic opioids don't seem to share. The cholinergic nervous system has antiinflammatory control functions that are largely unexploited.

SUMMARY

Long-term outcome after surgery is a new safety concern in perioperative care. We are faced with enormous challenges in healthcare and research. As providers, tailoring an anesthetic plan to patients' needs will become increasingly critical, and immunology should help in this pursuit.

The diabetic surgical patient

PURPOSE OF REVIEW

This review summarizes the current progress in disease classification, pathophysiology and management of diabetes mellitus with a special focus on treatment modalities and recommendations for the practicing anesthesiologist.

RECENT FINDINGS

The revised classification of diabetes mellitus emphasizes disease cause and eliminates any reference to age-of-onset and insulin therapy. Hyperglycemia has emerged as an important marker of outcome in the operating room. Intensive insulin therapy promises to reduce health risk in the surgical and critical care setting. Perioperative beta-blocker and statin therapy are likely to reduce cardiac morbidity and mortality in diabetic patients. Promotility therapy (with metoclopromide) intended to reduce the aspiration risk of diabetic gastroparesis is likely over-utilized and may only be indicated for diabetics with poor glucose control and high hemoglobin A1c levels.

SUMMARY

According to World Health Organization projections, anesthesiologists can expect to care for more diabetic patients than ever before. Diabetes and its associated complications present unique challenges to the perioperative physician. As biomedical research continues to unravel the genetic, cellular and molecular mechanisms of this complex metabolic disease, our specialty must be prominently involved in the design and testing of innovative treatments to protect the diabetic patient from the risks of surgery and anesthesia.

Long-term Outcome After Anesthesia and Surgery: Remarks on the Biology of a Newly Emerging Principle in Perioperative Care

There is a strong possibility that the risk from anesthesia and surgery carries over from the immediate perioperative period to more remote time points. This extended risk seems to influence the progression, severity, and complication rate of certain chronic illnesses, such as vascular heart disease and some of the malignancies, although other disease processes might be affected as well. With the recognition that the perioperative process could be responsible for later adverse events comes the need to reassess existing patient safety models, because some of the risk could be preventable. To confront these challenges, it is necessary to understand the underlying biology of this association, and immunology should be particularly helpful in this pursuit. It will be of special importance to integrate our knowledge of the host immune response to anesthesia and surgery with the recent revelations on the role of immunity in the progression of many of the chronic diseases. Additionally, we need to examine how genetic diversity or acquired defects alter the immune response to tissue injury and infection so that we can improve risk stratification and preemptive therapies. In the meantime, we must strive to improve short- and long-term outcomes by expanding our efforts to reduce disease activity preoperatively, to control the surgical stress response and infection rate, and to use tissue-preserving surgical techniques. Long-term patient safety after anesthesia and surgery is not a specialty-by-specialty endeavor; it requires a highly collaborative, institutional, and national effort to foster innovative research and health care process improvements.

Fas-associated death-domain protein inhibits TNF-α mediated NF-κB activation in cardiomyocytes

Fas-associated death-domain protein (FADD) is an adaptor molecule that links death receptors to caspase-8 in many cell types including cardiomyocytes (CMs). Although FADD has previously been reported to play an important role in CM apoptosis, the effect of FADD on CM NF-κB signaling, which is a proinflammatory pathway, has not been delineated. To investigate the role of FADD in CM NF-κB activation, we utilized adenoviral gene transfer of wild-type FADD and a truncation mutant that lacks the death-effector domain (FADD-DED) in rat CMs in vitro TNF-α activated NF-κB in CMs as demonstrated by phosphorylation and degradation of inhibitory-κB (IκB)-α-enhanced nuclear p65 and NF-κB DNA-binding activity as well as increased mRNA for the NF-κB-dependent adhesion molecule VCAM-1 (19 ± 4.1-fold) as measured by quantitative RT-PCR. Gene transfer of FADD inhibited TNF-α-induced IκB-α phosphorylation, decreased p65 nuclear translocation and NF-κB DNA-binding activity, and reduced VCAM-1 transcript levels by 53–65%. Interestingly, FADD-DED exhibited a similar but weaker inhibitory effect on NF-κB activation. The effects of FADD on NF-κB were cell-type specific. FADD expression also inhibited TNF-α-mediated NF-κB activation in human endothelial cells but not in rat pulmonary artery smooth muscle cells. In contrast, FADD expression actually activated NF-κB in human embryonic kidney (HEK)-293 cells. In CMs, FADD inhibited NF-κB activation as well as phosphorylation of IκB-α and IκB kinase (IKK)-β in response to cytokine stimulation or expression of the upstream kinases NF-κB-inducing kinase and IKK-β. These data demonstrate that FADD inhibits NF-κB activation in CMs, and this inhibition likely occurs at the level of phosphorylation and activation of IKK-β.

Endothelial IKK beta signaling is required for monocyte adhesion under laminar flow conditions

Endothelial activation induces expression of pro-inflammatory molecules that are thought to play an important role in atherogenesis through enhanced vascular monocyte recruitment. Many pro-inflammatory endothelial signals are transcriptionally regulated by members of the NF- kappa B family. The serine-threonine kinase, IKK beta, can mediate NF- kappa B activation although several alternative pathways exist. To test whether IKK beta is necessary for cytokine activation of human vascular endothelium and endothelial recruitment of human monocytes under laminar flow, we constructed a recombinant adenoviral vector carrying a dominant negative mutant of IKK beta (Ad.dnIKK beta) to transduce human umbilical vein endothelial cells (HUVEC) in vitro. We found that dnIKK beta expression effectively blocked NF-kappa B activation as assessed by nuclear translocation of NF-kappa B, I kappa B degradation, and NF-kappa B dependent reporter expression, without affecting activation of the other relevant signaling pathways, SAPK/JNK and p38. Furthermore, overexpression of dnIKK beta in TNF-alpha-stimulated HUVEC blocked induction of the surface adhesion molecules E-selectin, ICAM-1, and VCAM-1. Under simulated physiologic flow conditions, both firm adhesion and rolling of human peripheral monocytes on dnIKK beta-transduced endothelial monolayers were markedly inhibited. We conclude that IKK beta is necessary for the cytokine-induced inflammatory phenotype of human endothelium and endothelial recruitment of human monocytes under flow.

Cardiomyopathy in zebrafish due to mutation in an alternatively spliced exon of titin

The zebrafish embryo is transparent and can tolerate absence of blood flow because its oxygen is delivered by diffusion rather than by the cardiovascular system. It is therefore possible to attribute cardiac failure directly to particular genes by ruling out the possibility that it is due to a secondary effect of hypoxia. We focus here on pickwickm171 (pikm171), a recessive lethal mutation discovered in a large-scale genetic screen. There are three other alleles in the pik complementation group with this phenotype (pikm242, pikm740, pikm186; ref. 3) and one allele (pikmVO62H) with additional skeletal paralysis. The pik heart develops normally but is poorly contractile from the first beat. Aside from the edema that inevitably accompanies cardiac dysfunction, development is normal during the first three days. We show by positional cloning that the 'causative' mutation is in an alternatively-spliced exon of the gene (ttn) encoding Titin. Titin is the biggest known protein and spans the half-sarcomere from Z-disc to M-line in heart and skeletal muscle. It has been proposed to provide a scaffold for the assembly of thick and thin filaments and to provide elastic recoil engendered by stretch during diastole. We found that nascent myofibrils form in pik mutants, but normal sarcomeres are absent. Mutant cells transplanted to wildtype hearts remain thin and bulge outwards as individual cell aneurysms without affecting nearby wildtype cardiomyocytes, indicating that the contractile deficiency is cell-autonomous. Absence of Titin function thus results in blockage of sarcomere assembly and causes a functional disorder resembling human dilated cardiomyopathies, one form of which is described in another paper in this issue.

Mutations affecting the formation and function of the cardiovascular system in the zebrafish embryo

As part of a large-scale mutagenesis screen of the zebrafish genome, we have identified 58 mutations that affect the formation and function of the cardiovascular system. The cardiovascular system is particularly amenable for screening in the transparent zebrafish embryo because the heart and blood vessels are prominent and their function easily examined. We have classified the mutations affecting the heart into those that affect primarily either morphogenesis or function. Nine mutations clearly disrupt the formation of the heart. cloche deletes the endocardium. In cloche mutants, the myocardial layer forms in the absence of the endocardium but is dysmorphic and exhibits a weak contractility. Two loci, miles apart and bonnie and clyde, play a critical role in the fusion of the bilateral tubular primordia. Three mutations lead to an abnormally large heart and one to the formation of a diminutive, dysmorphic heart. We have found no mutation that deletes the myocardial cells altogether, but one, pandora, appears to eliminate the ventricle selectively. Seven mutations interfere with vascular integrity, as indicated by hemorrhage at particular sites. In terms of cardiac function, one large group exhibits a weak beat. In this group, five loci affect both chambers and seven a specific chamber (the atrium or ventricle). For example, the weak atrium mutation exhibits an atrium that becomes silent but has a normally beating ventricle. Seven mutations affect the rhythm of the heart causing, for example, a slow rate, a fibrillating pattern or an apparent block to conduction. In several other mutants, regurgitation of blood flow from ventricle to atrium is the most prominent abnormality, due either to the absence of valves or to poor coordination between the chambers with regard to the timing of contraction. The mutations identified in this screen point to discrete and critical steps in the formation and function of the heart and vasculature.

Central and regional hemodynamic effects of oral enoximone in congestive heart failure: a double-blind, placebo-controlled study

Twelve patients with congestive heart failure underwent a double-blind, placebo-controlled study for the purpose of examining the central and regional hemodynamic effects of first-dose (1 and 2 mg/kg) oral enoximone, a new phosphodiesterase III inhibitor. Enoximone augmented cardiac output, generally through a positive chronotropic response. Indices of left ventricular contractility, specifically stroke volume, delta P/delta t, fractional shortening rate, and the duration of the preejection period, were only modestly enhanced by enoximone. At 2 mg/kg, systemic vascular resistance fell below baseline values without affecting systemic blood pressure; these parameters were not altered by the 1 mg/kg dose. Both pulmonary artery pressure and pulmonary vascular resistance dropped below baseline and below placebo control for the 2 mg/kg dose. Enoximone at 2 mg/kg lowered right and left heart filling pressures below baseline. Examination of regional hemodynamic responses to both doses demonstrated a reduction in limb vascular resistance and an increase in limb blood flow proportional to the concomitant increase in cardiac output. Renal and hepatic-splanchnic blood flow and vascular resistances were not altered by enoximone. First-dose oral enoximone (1 and 2 mg/kg) alters hemodynamics in heart failure by predominant vasodilatation, particularly of limb-musculoskeletal and pulmonary vascular beds, some positive chronotropism, and modest positive inotropism.

Diastolic time in congestive heart failure

Diastolic perfusion time is an important determinant of coronary blood flow and subendocardial perfusion. It has been proposed that subendocardial ischemia may exacerbate and perpetuate left ventricular dysfunction in congestive heart failure. Diastolic perfusion time in relation to heart rate was analyzed in 29 digitalized (group 1) and 12 nondigitalized patients (group 2) with heart failure and in 58 normal control subjects. In group 1 there was a strong negative exponential correlation (r = -0.85) and in group 2 a strong negative logarithmic correlation (r = -0.95) between heart rate and diastolic time; both regressions differed significantly from normal control. There was a 9% increase of diastolic time at a heart rate of 60 bpm in group 1 and a 7% increase in group 2 (both p less than 0.05) compared with normal subjects. The curves intersected the regression line of normal subjects at a heart rate of 98 bpm in group 1 and 93 bpm in group 2. At 120 bpm there was a 10% decrease in diastolic time for both groups with heart failure (both p less than 0.05). Changes in diastolic perfusion time relative to heart rate are more pronounced in congestive heart failure such that at faster heart rates this relationship may further impede subendocardial blood flow.

A preliminary report of the effects of orally administered enoximone on regional hemodynamics in congestive heart failure

Twelve patients with moderately severe congestive heart failure underwent the simultaneous determination of central and regional hemodynamics after administration of placebo and enoximone. The regions examined hemodynamically included renal, hepatic-splanchnic and upper limb. Enoximone was studied in 2 doses, 1 and 2 mg/kg, and administered in a double-blind, placebo-controlled, crossover design. At these doses enoximone elicited a significantly greater increase in cardiac output and a greater decrease in systemic vascular resistance than placebo. Systemic blood pressure was not significantly altered. Enoximone did not significantly change the flow or resistance of renal or hepatic-splanchnic vascular beds. Limb vascular resistance decreased modestly after enoximone with a significant augmentation (+12% to 17%) of limb blood flow compared with placebo. The initial oral administration of the 1 and 2 mg/kg doses of enoximone improved central hemodynamic parameters with apparent preferential reduction of limb vascular resistance and augmentation of blood flow to the limb region (peripheral musculoskeletal system).

An analysis of the determinants of exercise performance in congestive heart failure

Twenty-nine patients with chronic congestive heart failure underwent symptom-limited maximal exercise to define the determinants and predictors of exercise capacity in this condition. Clinically, the combination of age, cardiothoracic ratio, and left ventricular displacement was moderately predictive of exercise capacity (R2 = 0.44, p = 0.004). Noninvasive and angiographic measurements of ventricular performance failed to predict maximal exercise duration. Resting systemic and pulmonary arteriolar resistances correlated modestly with maximal effort tolerance (supine: R2 = 0.25, p = 0.02; upright: R2 = 0.38, p = 0.002). At a predetermined level of submaximal exercise, changes in heart rate and pulmonary arteriolar resistance plus the absolute value of systemic arteriolar resistance correlated moderately with exercise duration (R2 = 0.44, p = 0.003). For all parameters examined, exercise capacity was most reliably determined during the transition from submaximal to maximal exercise through the combination of changes in heart rate and stroke volume and the exercise end point value of systemic arteriolar resistance (R2 = 0.87, p = 0.0001). Exercise capacity in chronic cardiac failure appears to be best explained by the patient's ability to increase heart rate and stroke volume beyond a set submaximal stage of exercise. Excessive vascular resistances may further restrain cardiac performance and the delivery of blood to exercising structures during exhaustive exercise.