John Whittle

Individualised oxygen delivery targeted haemodynamic therapy in high-risk surgical patients: a multicentre, randomised, double-blind, controlled, mechanistic trial

BACKGROUND Morbidity after major surgery is associated with low oxygen delivery. Haemodynamic therapy aimed at increasing oxygen delivery in an effort to reduce oxygen debt, tissue injury, and morbidity, is controversial. The most appropriate target for this strategy is unclear and might have several off-target effects, including loss of neural (parasympathetic)-mediated cellular protection. We hypothesised that individualised oxygen delivery targeted haemodynamic therapy (goal-directed therapy) in high-risk surgical patients would reduce postoperative morbidity, while secondarily addressing whether goal-directed therapy affected parasympathetic function. METHODS In this multicentre, randomised, double-blind, controlled trial, adult patients undergoing major elective surgery were allocated by computer-generated randomisation to a postoperative protocol (fluid, with and without dobutamine) targeted to achieve their individual preoperative oxygen delivery value (goal-directed therapy) or standardised care (control). Patients and staff were masked to the intervention. The primary outcome was absolute risk reduction (ARR) in morbidity (defined by Clavien-Dindo grade II or more) on postoperative day 2. We also assessed a secondary outcome focused on parasympathetic function, using time-domain heart rate variability measures. Analyses were done on an intention-to-treat basis. The trial was registered with Controlled Clinical Trials (number ISRCTN76894700). FINDINGS We enrolled 204 patients between May 20, 2010, and Feb 12, 2014. Intention-to-treat analysis of the 187 (92%) patients who completed the trial intervention period showed that early morbidity was similar between goal-directed therapy (44 [46%] of 95 patients) and control groups (49 [53%] of 92 patients) (ARR -7%, 95% CI -22 to 7; p=0·30). Prespecified secondary analysis showed that 123 (66%) of 187 patients achieved preoperative oxygen delivery (irrespective of intervention). These patients sustained less morbidity (ARR 19%, 95% CI 3-34; p=0·016), including less infectious complications. Goal-directed therapy reduced parasympathetic activity postoperatively (relative risk 1·33, 95% CI 1·01-1·74). INTERPRETATION Achievement of preoperative oxygen delivery values in the postoperative phase was associated with less morbidity, but this was not affected by the use of an oxygen delivery targeted strategy. Reduced parasympathetic activity after goal-directed therapy was associated with the failure of this intervention to reduce postoperative morbidity. FUNDING Academy of Medical Sciences and Health Foundation Clinician Scientist Award.

Preoperative Anthropometric Analysis of the Cleft Child's Face: A Comparison between Groups

This study examines the facial surfaces of different groups of cleft babies aged up to eleven months, prior to any corrective surgery, with the aim of identifying and assessing differences in their facial morphology. Measurements of standard anthropometric landmarks were made on plaster casts taken pre-operatively of the faces of babies presenting for surgical correction of lip and palate deformities. Periorbital and mid face measurements show no difference between control and cleft groups. The nasal base is shown to be wider in infants with cleft lip on both cleft and non-cleft sides. Upper lip measurements indicate shortening, lateral deviation and superolateral rotation. A diagrammatic model is proposed to illustrate facial anatomy in control and cleft individuals. Modifications to the technique are proposed. Further study in this field is suggested, in order to produce a comprehensive database of facial morphological changes in the cleft and non-cleft populations both pre-operatively and over time, with a view to producing a potential redefinition of the cleft syndrome based on anthropometric principles.

Molecular Mechanisms Linking Autonomic Dysfunction and Impaired Cardiac Contractility in Critical Illness.

Objectives:Molecular mechanisms linking autonomic dysfunction with poorer clinical outcomes in critical illness remain unclear. We hypothesized that baroreflex dysfunction alone is sufficient to cause cardiac impairment through neurohormonal activation of (nicotinamide adenine dinucleotide phosphate oxidase dependent) oxidative stress resulting in increased expression of G-protein–coupled receptor kinase 2, a key negative regulator of cardiac function. Design:Laboratory/clinical investigations. Setting:University laboratory/medical centers. Subjects:Adult rats; wild-type/nicotinamide adenine dinucleotide phosphate oxidase subunit-2–deficient mice; elective surgical patients. Interventions:Cardiac performance was assessed by transthoracic echocardiography following experimental baroreflex dysfunction (sino-aortic denervation) in rats and mice. Immunoblots assessed G-protein–coupled receptor recycling proteins expression in rodent cardiomyocytes and patient mononuclear leukocytes. In surgical patients, heart rate recovery after cardiopulmonary exercise testing, time/frequency measures of parasympathetic variables were related to the presence/absence of baroreflex dysfunction (defined by spontaneous baroreflex sensitivity of <6 ms mm Hg–1). The associations of baroreflex dysfunction with intraoperative cardiac function and outcomes were assessed. Measurements and Main Results:Experimental baroreflex dysfunction in rats and mice resulted in impaired cardiac contractility and upregulation of G-protein–coupled receptor kinase 2 expression. In mice, genetic deficiency of gp91 nicotinamide adenine dinucleotide phosphate oxidase subunit-2 prevented upregulation of G-protein–coupled receptor kinase 2 expression in conditions of baroreflex dysfunction and preserved cardiac function. Baroreflex dysfunction was present in 81 of 249 patients (32.5%) and was characterized by lower parasympathetic tone and increased G-protein–coupled receptor kinase 2 expression in mononuclear leukocytes. Baroreflex dysfunction in patients was also associated with impaired intraoperative cardiac contractility. Critical illness and mortality were more frequent in surgical patients with baroreflex dysfunction (relative risk, 1.66 [95% CI, 1.16–2.39]; p = 0.006). Conclusions:Reduced baroreflex sensitivity is associated with nicotinamide adenine dinucleotide phosphate oxidase subunit-2–mediated upregulation of G-protein–coupled receptor kinase 2 expression in cardiomyocytes and impaired cardiac contractility. Autonomic dysfunction predisposes patients to the development of critical illness and increases mortality.

Biomarkers to guide perioperative management

Stratifying preoperative risk and guiding perioperative therapy objectively has acquired critical importance, given robust data demonstrating that morbidity following non-cardiac surgery confers substantially increased risk of death, even beyond hospital discharge. The development of useful perioperative biomarkers depends fundamentally on both prospective morbidity data that enable the identification of higher risk patients as well as the translational understanding of pathophysiological mechanisms underlying postoperative organ dysfunction, the development of which may be specific to the perioperative environment. The emergence of cardiac insufficiency, rather than cardiac ischaemia, as the dominant factor associated with excess risk of prolonged postoperative morbidity has promoted the application of biomarkers used commonly in cardiovascular medicine. Several novel, organ specific biomarkers offer potential perioperative application. Nevertheless, common tests/biomarkers that are widely available do provide valuable, objective information that is perhaps under-utilised perioperatively. Despite significant challenges, perioperative medicine presents exciting—arguably unique—opportunities for novel biomarker development.

Baroreflex impairment and morbidity after major surgery.

BACKGROUND Baroreflex dysfunction is a common feature of established cardiometabolic diseases that are most frequently associated with the development of critical illness. Laboratory models show that baroreflex dysfunction impairs cardiac contractility and cardiovascular performance, thereby increasing the risk of morbidity after trauma and sepsis. We hypothesized that baroreflex dysfunction contributes to excess postoperative morbidity after major surgery as a consequence of the inability to achieve adequate perioperative tissue oxygen delivery. METHODS In a randomized controlled trial of goal-directed haemodynamic therapy (GDT) in higher-risk surgical patients, baroreflex function was assessed using the spontaneous baroreflex sensitivity (BRS) method via an arterial line placed before surgery, using a validated sequence method technique (one beat lag). The BRS was calculated during the 6 h postoperative GDT intervention. Analyses of BRS were done by investigators blinded to clinical outcomes. The primary outcome was the association between postoperative baroreflex dysfunction (BRS <6 mm Hg s(-1), a negative prognostic threshold in cardiovascular pathology) and early postoperative morbidity. The relationship between baroreflex dysfunction and postoperative attainment of preoperative indexed oxygen delivery was also assessed. RESULTS Patients with postoperative baroreflex dysfunction were more likely to sustain infectious {relative risk (RR) 1.75 [95% confidence interval (CI): 1.07-2.85], P=0.02} and cardiovascular morbidity [RR 2.39 (95% CI: 1.22-4.71), P=0.008]. Prolonged hospital stay was more likely in patients with baroreflex dysfunction [unadjusted hazard ratio 1.62 (95% CI: 1.14-2.32), log-rank P=0.004]. Postoperative O2 delivery was 36% (95% CI: 7-65) lower in patients with baroreflex dysfunction in those not randomly assigned to GDT (P=0.02). CONCLUSIONS Baroreflex dysfunction is associated with excess morbidity, impaired cardiovascular performance, and delayed hospital discharge, suggesting a mechanistic role for autonomic dysfunction in determining perioperative outcome. CLINICAL TRIAL REGISTRATION ISCRTN76894700.

Sympathetic autonomic dysfunction and impaired cardiovascular performance in higher risk surgical patients: implications for perioperative sympatholysis

Objective Recent perioperative trials have highlighted the urgent need for a better understanding of why sympatholytic drugs intended to reduce myocardial injury are paradoxically associated with harm (stroke, myocardial infarction). We hypothesised that following a standardised autonomic challenge, a subset of patients may demonstrate excessive sympathetic activation which is associated with exercise-induced ischaemia and impaired cardiac output. Methods Heart rate rise during unloaded pedalling (zero workload) prior to the onset of cardiopulmonary exercise testing (CPET) was measured in 2 observation cohorts of elective surgical patients. The primary outcome was exercise-evoked, ECG-defined ischaemia (>1 mm depression; lead II) associated with an exaggerated increase in heart rate (EHRR ≥12 bpm based on prognostic data for all-cause cardiac death in preceding epidemiological studies). Secondary outcomes included cardiopulmonary performance (oxygen pulse (surrogate for left ventricular stroke volume), peak oxygen consumption (VO2peak), anaerobic threshold (AT)) and perioperative heart rate. Results EHRR was present in 40.4–42.7% in both centres (n=232, n=586 patients). Patients with EHRR had higher heart rates perioperatively (p<0.05). Significant ST segment depression during CPET was more common in EHRR patients (relative risk 1.7 (95% CI 1.3 to 2.1); p<0.001). EHRR was associated with 11% (95%CI 7% to 15%) lower predicted oxygen pulse (p<0.0001), consistent with impaired left ventricular function. Conclusions EHRR is common and associated with ECG-defined ischaemia and impaired cardiac performance. Perioperative sympatholysis may further detrimentally affect cardiac output in patients with this phenotype.

Vagal determinants of exercise capacity

Indirect measures of cardiac vagal activity are strongly associated with exercise capacity, yet a causal relationship has not been established. Here we show that in rats, genetic silencing of the largest population of brainstem vagal preganglionic neurons residing in the brainstems dorsal vagal motor nucleus dramatically impairs exercise capacity, while optogenetic recruitment of the same neuronal population enhances cardiac contractility and prolongs exercise endurance. These data provide direct experimental evidence that parasympathetic vagal drive generated by a defined CNS circuit determines the ability to exercise. Decreased activity and/or gradual loss of the identified neuronal cell group provides a neurophysiological basis for the progressive decline of exercise capacity with aging and in diverse disease states.

Autonomic regulation of systemic inflammation in humans: A multi-center, blinded observational cohort study.

OBJECTIVE Experimental animal models demonstrate that autonomic activity regulates systemic inflammation. By contrast, human studies are limited in number and exclusively use heart rate variability (HRV) as an index of cardiac autonomic regulation. HRV measures are primarily dependent on, and need to be corrected for, heart rate. Thus, independent autonomic measures are required to confirm HRV-based findings. Here, the authors sought to replicate the findings of preceding HRV-based studies by using HRV-independent, exercise-evoked sympathetic and parasympathetic measures of cardiac autonomic regulation to examine the relationship between autonomic function and systemic inflammation. METHODS Sympathetic function was assessed by measuring heart rate changes during unloaded pedaling prior to onset of exercise, divided into quartiles; an anticipatory heart rate (AHRR) rise during this period is evoked by mental stress in many individuals. Parasympathetic function was assessed by heart rate recovery (HRR) 60s after finishing cardiopulmonary exercise testing, divided into quartiles. Parasympathetic dysfunction was defined by delayed heart rate recovery (HRR) ≤12.beats.min-1, a threshold value associated with higher cardiovascular morbidity/mortality in the general population. Systemic inflammation was primarily assessed by neutrophil-lymphocyte ratio (NLR), where a ratio >4 is prognostic across several inflammatory diseases and correlates strongly with elevated plasma levels of pro-inflammatory cytokines. High-sensitivity C-reactive protein (hsCRP) was also measured. RESULTS In 1624 subjects (65±14y; 67.9% male), lower HRR (impaired vagal activity) was associated with progressively higher NLR (p=0.004 for trend across quartiles). Delayed HRR, recorded in 646/1624 (39.6%) subjects, was associated with neutrophil-lymphocyte ratio >4 (relative risk: 1.43 (95%CI: 1.18-1.74); P=0.0003). Similar results were found for hsCRP (p=0.045). By contrast, AHRR was not associated with NLR (relative risk: 1.24 (95%CI: 0.94-1.65); P=0.14). CONCLUSIONS Delayed HRR, a robust measure of parasympathetic dysfunction, is independently associated with leukocyte ratios indicative of systemic inflammation. These results further support a role for parasympathetic modulation of systemic inflammation in humans.

Subclinical cardiopulmonary dysfunction in stage 3 chronic kidney disease.

Objective Reduced exercise capacity is well documented in end-stage chronic kidney disease (CKD), preceded by changes in cardiac morphology in CKD stage 3. However, it is unknown whether subclinical cardiopulmonary dysfunction occurs in CKD stage 3 independently of heart failure. Methods Prospective observational cross-sectional study of exercise capacity assessed by cardiopulmonary exercise testing in 993 preoperative patients. Primary outcome was peak oxygen consumption (VO2peak). Anaerobic threshold (AT), oxygen pulse and exercise-evoked measures of autonomic function were analysed, controlling for CKD stage 3, age, gender, diabetes mellitus and hypertension. Results CKD stage 3 was present in 93/993 (9.97%) patients. Diabetes mellitus (RR 2.49 (95% CI 1.59 to 3.89); p<0.001), and hypertension (RR 3.20 (95% CI 2.04 to 5.03); p<0.001)) were more common in CKD stage 3. Cardiac failure (RR 0.83 (95% CI 0.30 to 2.24); p=0.70) and ischaemic heart disease (RR 1.40 (95% CI 0.97 to 2.02); p=0.09) were not more common in CKD stage 3. Patients with CKD stage 3 had lower predicted VO2peak (mean difference: 6% (95% CI 1% to 11%); p=0.02), lower peak heart rate (mean difference:9 bpm (95% CI 3 to 14); p=0.03)), lower AT (mean difference: 1.1 mL/min/kg (95% CI 0.4 to 1.7); p<0.001) and impaired heart rate recovery (mean difference: 4 bpm (95% CI 1 to 7); p<0.001)). Conclusions Subclinical cardiopulmonary dysfunction in CKD stage 3 is common. This study suggests that maladaptive cardiovascular/autonomic dysfunction may be established in CKD stage 3, preceding pathophysiology reported in end-stage CKD.

Pulse pressure and postoperative morbidity in high risk surgical patients.

3 POM-HR Study Investigators: Derriford Hospital, Plymouth Hospitals NHS Trust & Peninsula Schools of Medicine and Dentistry, Plymouth University: Gary Minto, Angela King, Claire Pollak, Claire Williams, Abigail Patrick, Claire West. Royal Bournemouth Hospital: Emma Vickers, Richard Green, Martin Clark. University College London Hospitals NHS Trust: John Whittle, Laura Gallego Paredes, Robert CM Stephens, Amy Jones, James Otto, Anna Lach, Ana Gutierrez del Arroyo, Andrew Toner. Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust: Alexandra Williams, Thomas Owen. Royal Surrey County Hospital: Pradeep Pradhu, Daniel Hull, Laura Montague.