Alterations in spectral characteristics of heart rate variability as a correlate of cardiac autonomic dysfunction after esophagectomy or pulmonary resection

Orthostatic intolerance after acute mild hypovolemia: incidence, pathophysiologic hemodynamics, and heart-rate variability analysis-a prospective observational cohort study

PURPOSE

Early postoperative mobilization can be hindered by orthostatic intolerance (OI). Postoperative OI has multifactorial pathogenesis, possibly involving both postoperative hypovolemia and autonomic dysfunction. We aimed to investigate the effect of mild acute blood loss from blood donation simulating postoperative hypovolemia, on both autonomic function and OI, thus eliminating confounding perioperative factors such as inflammation, residual anesthesia, pain, and opioids.

METHODS

This prospective observational cohort study included 26 blood donors. Continuous electrocardiogram data were collected during mobilization and night sleep, both before and after blood donation. A Valsalva maneuver and a standardized mobilization procedure were performed immediately before and after blood donation, during which cardiovascular and tissue oxygenation variables were continuously measured by LiDCOrapid™ and Massimo Root™, respectively. The incidence of OI, hemodynamic responses during mobilization and Valsalva maneuver, as well as heart rate variability (HRV) responses during mobilization and sleep were compared before and 15 min after blood donation.

RESULTS

Prior to blood donation, no donors experienced OI during mobilization. After blood donation, 6/26 (23%; 95% CI, 9 to 44) donors experienced at least one OI symptom. Three out of 26 donors (12%; 95% CI, 2 to 30) terminated the mobilization procedure prematurely because of severe OI symptoms. Cardiovascular and cerebral tissue oxygenation responses were reduced in patients with severe OI. After blood loss, HRV indices of total autonomic power remained unchanged but increased sympathetic and decreased parasympathetic outflow was observed during mobilization, but also during sleep, indicating a prolonged autonomic effect of hypovolemia.

CONCLUSION

We describe a specific hypovolemic component of postoperative OI, independent of postoperative autonomic dysfunction, inflammation, opioids, and pain.

STUDY REGISTRATION

ClinicalTrials.gov (NCT04499664); registered 5 August 2020.

Association of thoracic epidural analgesia with risk of atrial arrhythmias after pulmonary resection: a retrospective cohort study

PURPOSE

Atrial arrhythmias are common after non-cardiac thoracic surgery. We tested the hypothesis that TEA reduces the risk of new-onset atrial arrhythmias after pulmonary resection.

METHODS

We evaluated patients who had pulmonary resection. New-onset atrial arrhythmias detected before hospital discharge was our primary outcome. Secondary outcomes included other cardiovascular complications, pulmonary complications, time-weighted average pain score over 72 h, and duration of hospitalization. Patients with combination of general anesthesia and TEA were matched on propensity scores with patients given general anesthesia only. The matched groups were compared by use of logistic regression, linear regression, or Cox proportional hazards regression, as appropriate.

RESULTS

Among 1,236 patients who had pulmonary resections, 937 received a combination of general anesthesia and TEA (TEA) and 299 received general anesthesia only (non-TEA). We successfully matched 311 TEA patients with 132 non-TEA patients. We did not find a significant association between TEA and postoperative atrial arrhythmia (odds ratio (95 % CI) of 1.05 (0.50, 2.19), P = 0.9). TEA was not significantly associated with length of hospital stay or postoperative pulmonary complications (odds ratio (95 % CI) of 0.71 (0.22, 2.29), P = 0.47). TEA patients experienced fewer postoperative cardiovascular complications; although the association was not statistically significant (odds ratio (95 % CI) of 0.30 (0.06, 1.45), P = 0.06). Time-weighted average pain scores were similar in the two groups.

CONCLUSION

TEA was not associated with reduced occurrence of postoperative atrial arrhythmia. Although postoperative pulmonary complications were similar with and without TEA, TEA patients tended to experience fewer cardiovascular complications.

Supraventricular arrhythmias after thoracotomy: is there a role for autonomic imbalance?

Supraventricular arrhythmias are common rhythm disturbances following pulmonary surgery. The overall incidence varies between 3.2% and 30% in the literature, while atrial fibrillation is the most common form. These arrhythmias usually have an uneventful clinical course and revert to normal sinus rhythm, usually before patent's discharge from hospital. Their importance lies in the immediate hemodynamic consequences, the potential for systemic embolization and the consequent long-term need for prophylactic drug administration, and the increased cost of hospitalization. Their incidence is probably related to the magnitude of the performed operative procedure, occurring more frequently after pneumonectomy than after lobectomy. Investigators believe that surgical factors (irritation of the atria per se or on the ground of chronic inflammation of aged atria), direct injury to the anatomic structure of the autonomic nervous system in the thoracic cavity, and postthoracotomy pain may contribute independently or in association with each other to the development of these arrhythmias. This review discusses currently available information about the potential mechanisms and risk factors for these rhythm disturbances. The discussion is in particular focused on the role of postoperative pain and its relation to the autonomic imbalance, in an attempt to avoid or minimize discomfort with proper analgesia utilization.

Postoperative atrial fibrillation

Postoperative atrial fibrillation (POAF) is common among surgical patients and associated with a worse outcome. Pathophysiology of POAF is not fully disclosed, and several perioperative factors could be involved. Direct cardiac stimulation from perioperative use of catecholamines or increased sympathetic outflow from volume loss/anaemia/pain may play a role. Metabolic alterations, such as hypo-/hyperglycaemia and electrolyte disturbances, may also contribute to POAF. Moreover, inflammation, both systemic and local, may play a role in its pathogenesis. Strategies to prevent POAF aim at reducing its incidence and ameliorate global outcome of surgical patients. Nonpharmacological prophylaxis includes an adequate control of postoperative pain, the use of thoracic epidural analgesia, optimization of perioperative oxygen delivery, and, possibly, modulation of surgery-associated inflammatory response with immunonutrition and antioxidants. Perioperative potassium and magnesium depletion should be corrected. The impact of those interventions on patients outcome needs to be further investigated.

Influence of thoracic epidural analgesia on cardiovascular autonomic control after thoracic surgery

BACKGROUND

Thoracic epidural analgesia (TEA) is effective in alleviating pain after major thoracoabdominal surgery and may also reduce postoperative mortality and morbidity. This study investigated cardiovascular autonomic control in patients undergoing elective thoracic surgery and its modulation by continuous TEA.

METHODS

Thirty-eight patients were randomly assigned to receive patient-controlled analgesia (PCA group) or thoracic epidural analgesia (TEA group) with doses of bupivacaine (0.25% during operation, 0.125% after operation) and fentanyl (2 microg ml(-1)). Heart rate variability (HRV), baroreflex function and pressure response to nitroglycerine and phenylephrine were assessed before operation, 4 h after the end of surgery (POD 0) and on the first and second postoperative days (POD 1 and POD 2).

RESULTS

Early after surgery, all HRV variables and baroreflex sensitivities were markedly decreased in both groups. In the TEA group, total HRV and its high-frequency components (HF) increased towards preoperative values at POD 1 and POD 2, whereas the ratio of low to high frequencies (LF/HF) was significantly reduced (mean (SD), -44 (15)% at POD 0, -38 (17)% at POD 1, -37 (18%) at POD 2) and associated with blunting of the postoperative increase in heart rate and blood pressure. In the PCA group, the ratio of LF/HF remained unchanged and the decrements in HRV variables persisted until POD 2. In the two groups, baroreflex sensitivities and pressure responses recovered preoperative values at POD 2.

CONCLUSIONS

In contrast with PCA management, TEA using low concentrations of bupivacaine and fentanyl blunted cardiac sympathetic neural drive, resulting in vagal predominance, while HRV variables were better restored after surgery.

Thoracic epidural bupivacaine attenuates supraventricular tachyarrhythmias after pulmonary resection

Supraventricular tachyarrhythmias after pulmonary surgery are well described. Some investigators suggest that tachyarrhythmias after thoracic operations may result from the relative sympathotonic status produced by injury to the cardiac parasympathetic nerves. We examined whether postoperative thoracic sympathetic blockade by thoracic epidural bupivacaine might reduce the tachyarrhythmias after pulmonary resection. Fifty patients with lung cancer were randomized to receive epidural bupivacaine (Group B) or epidural morphine (Group M). Patients in Group B were given 6 to 10 mL of 0.25% bupivacaine epidurally, followed by epidural infusion at 3 to 5 mL/h for 3 days, and patients in Group M were given 2 to 3 mg morphine epidurally, followed by morphine infusion at a rate of 0.2 mg/h. Tachyarrhythmias were diagnosed by using the continuous heart rate trend and arrhythmia trend with a central monitoring system. Postoperative analgesia was not statistically different between groups. However, the incidence of postoperative tachyarrhythmias in Group B was significantly less than in Group M (1 of 23 vs 7 of 25, P = 0.0497, Fisher's exact test). The continuous infusion of thoracic epidural bupivacaine can reduce supraventricular tachyarrhythmias compared with epidural morphine infusion, presumably because of attenuation of the sympathotonic status after pulmonary resection.

IMPLICATIONS

We examined whether postoperative thoracic sympathetic blockade by thoracic epidural bupivacaine after pulmonary resection might reduce the tachyarrhythmias that may result from the relative sympathotonic status produced by injury to the cardiac parasympathetic nerves. The continuous infusion of thoracic epidural bupivacaine was shown to reduce supraventricular tachyarrhythmias.

Pain relief after esophagectomy: Thoracic epidural analgesia is better than parenteral opioids

OBJECTIVE

To compare postoperative pain relief and pulmonary function in patients after thoracoabdominal esophagectomy treated by continuing perioperative thoracic epidural anesthesia or changing to parenteral opioids.

DESIGN

Prospective, randomized study.

SETTING

University teaching hospital.

PARTICIPANTS

Thirty-three patients undergoing thoracoabdominal esophagectomy.

INTERVENTIONS

General anesthesia was combined with thoracic epidural anesthesia during surgery. The patients either continued with thoracic epidural analgesia (n = 18) or were switched to patient-controlled analgesia with intravenous morphine (n = 15) for 5 postoperative days. Pain scores were estimated twice daily, at rest and after mobilization. Peak expiratory flow, forced expiratory volume, and vital capacity were measured the day before surgery, postoperative day 2, and postoperative day 6. Adverse events and complications were recorded.

MEASUREMENTS AND MAIN RESULTS

At rest, there were no differences in pain relief between the groups. Pain scores at mobilization showed a significantly lower value in the epidural group (p < 0.027). No intergroup differences were found regarding pulmonary function, which decreased on postoperative day 2, but was improved on postoperative day 6.

CONCLUSION

Continuation of intraoperative thoracic epidural anesthesia for 5 postoperative days provides better pain relief at mobilization compared with a switch to patient-controlled analgesia with intravenous morphine. There was no intergroup difference in the impact on measures of pulmonary function.

Alterations in autonomic nervous control of heart rate among tourists at 2700 and 3700 m above sea level

OBJECTIVES

Many travelers who are not specially trained for activities at high altitude are at risk of physical problems, including cardiovascular disorders, when exposed to high-altitude environments. In the present study, we investigated how actual acute exposure to altitudes of 2700 and 3700 m affected the autonomic nervous control of heart rate in untrained office workers.

METHODS

Physiological parameters (heart rate, respiratory rate, arterial blood oxygen saturation, and end-expiratory carbon dioxide tension) were measured at sea level, 2700 m, and 3700 m. The power of heart rate variability was quantified by determining the areas of the spectrum in 2 component widths: low frequency (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.5 Hz). The ratio of LF power to HF power (LF:HF), which is considered to be an index of cardiac sympathetic tone, was also assessed.

RESULTS

Both HF and LF heart rate variability decreased according to the elevation of altitude. High- and low-frequency powers at 3700 m were significantly lower than those at sea level (P < .01 for HF, P < .05 for LF). The LF:HF ratio at 2700 m was not significantly different from that at sea level. However, it was significantly increased at 3700 m (P < .01).

CONCLUSIONS

At 2700 and 3700 m, the activity of the autonomic nervous system measured by heart rate variability was decreased in untrained office workers. The sympathetic nervous system was dominant to the parasympathetic at 3700 m. These alterations in the autonomic nervous system might play some role in physical fitness at high altitudes.

Power spectral analysis of cardiovascular variability in critically ill neurosurgical patients

OBJECTIVE

Patients with brain damage exhibit a number of changes in heart rate and cardiovascular control. The aim of this study was to relate changes in autonomic cardiovascular control seen in critically ill neurosurgical patients to the quality of subsequent outcome and survival.

DESIGN

Prospective, longitudinal, outcome study.

SETTING

Intensive care department of a university teaching hospital.

PATIENTS

A total of 29 consecutive neurosurgical patients admitted for > or =2 days to the intensive care department with a Glasgow Coma Scale score < 13 who needed electrocardiographic and invasive arterial monitoring.

INTERVENTIONS

Sampling of the electrocardiogram, respiratory rate, and arterial pressure into a personal computer was carried out for > or =60 mins. Power spectral analysis was then applied to the data by using a fast Fourier transformation. Arterial baroreflex sensitivity was determined as the gain of the transfer function between systolic arterial blood pressure and electrocardiograph R-R interval (RRI) variability. All surviving patients were followed up at 3 months postadmission to measure quality of outcome.

MEASUREMENTS AND MAIN RESULTS

There were reductions in the total power (p < .01) of RRI variability in those who subsequently died compared with those who survived. This was significant for very low frequency (p < .001) and low-frequency (LF) (p < .05) but not high-frequency (HF) bands (p = .11). Blood pressure variability, however, did not change between groups. Baroreflex sensitivity was 8.7+/-2.2 msecs/mm Hg for patients with a good later outcome and 4.4+/-1.5 msecs/mm Hg for patients who subsequently died (p = .03). Patients who recovered to a good quality outcome also had a raised LF/HF ratio in RRI (p = .05).

CONCLUSION

A reduction in the total power variability of RRI and a lowered LF/HF ratio of the RRI are associated with a poor quality recovery or death after neurosurgical illness. A reduction in the baroreflex was specifically associated with death in this patient group.

Differences among heart rate variability measures after anesthesia and cardiac surgery

OBJECTIVE

To determine whether there are differences among measures of heart rate variability (HRV; traditional and nonlinear) after anesthesia and cardiac surgery.

DESIGN

Prospective.

SETTING

University hospital.

PARTICIPANTS

Patients scheduled for cardiac surgery.

INTERVENTIONS

None. Medical management was not varied as part of this study.

MEASUREMENTS AND MAIN RESULTS

HRV was measured in 13 patients from electrocardiograms (ECGs) recorded before anesthesia, during anesthesia but before cardiac surgery, and on the first postoperative day. Anesthesia was induced with moderate-dose fentanyl. For each ECG, HRV was measured from series of 400 heartbeat intervals using standard deviation (SD), approximate entropy (ApEn), and point correlation dimension (PD2). Multivariate repeated-measures analyses of variance on ranks and Spearman correlations were performed. All HRV measures decreased significantly with anesthesia. Postoperatively, ApEn recovered to original values. PD2 and SD did not recover with consciousness and were significantly less than original values. Correlations among ApEn, PD2, and SD were weak.

CONCLUSIONS

Nonlinear measures of HRV differ among themselves after anesthesia and cardiac surgery. The use of multiple nonlinear and traditional measures may improve the effectiveness of using HRV to assess the cardiovascular system.