Peripheral perfusion index stratifies risk in patients with intraoperative anemia: A multicentre cohort study

STUDY OBJECTIVE

Evidence for red blood cell (RBC) transfusion thresholds in the intraoperative setting is limited, and current perioperative recommendations may not correspond with individual intraoperative physiological demands. Hemodynamics relevant for the decision to transfuse may include peripheral perfusion index (PPI). The objective of this prospective study was to assess the associations of PPI and hemoglobin levels with the risk of postoperative morbidity and mortality.

DESIGN

Multicenter cohort study.

SETTING

Bispebjerg and Hvidovre University Hospitals, Copenhagen, Denmark.

PATIENTS

We included 741 patients who underwent acute high risk abdominal surgery or hip fracture surgery.

INTERVENTIONS

No interventions were carried out.

MEASUREMENTS

Principal values collected included measurements of peripheral perfusion index and hemoglobin values.

METHODS

The study was conducted using prospectively obtained data on adults who underwent emergency high-risk surgery. Subjects were categorized into high vs. low subgroups stratified by pre-defined PPI levels (PPI: > 1.5 vs. < 1.5) and Hb levels (Hb: > 9.7 g/dL vs. < 9.7 g/dL). The study assessed mortality and severe postoperative complications within 90 days.

MAIN RESULTS

We included 741 patients. 90-day mortality was 21% (n = 154), frequency of severe postoperative complications was 31% (n = 231). Patients with both low PPI and low Hb had the highest adjusted odds ratio for both 90-day severe postoperative complications (2.95, [1.62-5.45]) and 90-day mortality (3.13, [1.45-7.11]). A comparison of patients with low PPI and low Hb to those with high PPI and low Hb detected significantly higher 90-day mortality risk in the low PPI and low Hb group (OR 8.6, [1.57-162.10]).

CONCLUSION

High PPI in acute surgical patients who also presents with anemia was associated with a significantly better outcome when compared with patients with both low PPI and anemia. PPI should therefore be further investigated as a potential parameter to guide intraoperative RBC transfusion therapy.

Comparing the effects of continuous positive airway pressure via mask or helmet interface on oxygenation and pulmonary complications after major abdominal surgery: a randomized trial

The risk of pulmonary complications is high after major abdominal surgery but may be reduced by prophylactic postoperative noninvasive ventilation using continuous positive airway pressure (CPAP). This study compared the effects of intermittent mask CPAP (ICPAP) and continuous helmet CPAP (HCPAP) on oxygenation and the risk of pulmonary complications following major abdominal surgery. Patients undergoing open abdominal aortic aneurysm repair or pancreaticoduodenectomy were randomized (1:1) to either postoperative ICPAP or HCPAP. Oxygenation was evaluated as the partial pressure of oxygen in arterial blood fraction of inspired oxygen ratio (PaO₂/FIO₂) at 6 h, 12 h, and 18 h postoperatively. Pulmonary complications were defined as X-ray verified pneumonia/atelectasis, clinical signs of pneumonia, or supplementary oxygen beyond postoperative day 3. Patient-reported comfort during CPAP treatment was also evaluated. In total, 96 patients (ICPAP, n = 48; HCPAP, n = 48) were included, and the type of surgical procedure were evenly distributed between the groups. Oxygenation did not differ between the groups by 6 h, 12 h, or 18 h postoperatively (p = 0.1, 0.08, and 0.67, respectively). Nor was there any difference in X-ray verified pneumonia/atelectasis (p = 0.40) or supplementary oxygen beyond postoperative day 3 (p = 0.53). Clinical signs of pneumonia tended to be more frequent in the ICPAP group (p = 0.06), yet the difference was not statistically significant. Comfort scores were similar in both groups (p = 0.43), although a sensation of claustrophobia during treatment was only experienced in the HCPAP group (11% vs. 0%, p = 0.03). Compared with ICPAP, using HCPAP was associated with similar oxygenation (i.e., PaO₂/FIO₂ ratio) and a similar risk of pulmonary complications. However, HCPAP treatment was associated with a higher sensation of claustrophobia.

High-dose preoperative glucocorticoid for prevention of emergence and postoperative delirium in liver resection: A double-blinded randomized clinical trial substudy

BACKGROUND

Emergence delirium (ED) and postoperative delirium (POD) are associated with increased morbidity and mortality and occur in up to one-third of patients undergoing major non-cardiac surgery, where the underlying pathogenesis is multifactorial, including increased inflammation. We aimed to assess the effect of pre-operative high- versus low-dose glucocorticoid on the occurrence of ED and POD.

METHODS

This was a substudy from a randomized, double-blinded clinical trial. Patients ≥18 years, undergoing open liver resection were randomized 1:1 to high-dose (HD, 10 mg/kg methylprednisolone) or low-dose (LD, 8 mg dexamethasone) glucocorticoid and assessed for ED and POD for a maximum of 4 days during hospitalization. The 3-min Diagnostic Interview for CAM-defined delirium (3D-CAM) was used for assessment, 15 and 90 min after arrival in the post-anesthesia care unit (PACU), and subsequently once daily in the ward.

RESULTS

Fifty-three patients were included in this secondary substudy (26 HD-group and 27 LD-group). ED occurred in n = 5 HD versus n = 6 LD patients 15 min after PACU arrival. At 90 min after PACU arrival, 4 patients had ED, all from LD-group, and resulted in significantly longer PACU admission, 273 versus 178 min in ED versus Non-ED patients. During the first 4 days in the ward, n = 5 patients had at least one occurrence of POD, all from LD-group.

CONCLUSIONS

The primary finding of the current substudy was a lower occurrence of ED/POD in the PACU 90 min after arrival and during the first four postoperative days in patients receiving high-dose glucocorticoid compared with patients receiving low-dose glucocorticoid. The two study groups were not evenly balanced concerning known explanatory factors, i.e., age and size of surgery, which calls for larger studies to elucidate the matter.

Managing patients on direct factor Xa inhibitors with rapid thrombelastography

The use of direct factor Xa inhibitors rivaroxaban and apixaban (XABANs) has rapidly increased; however, there is no validated test available to monitor the effect on hemostasis. This study aims to assess how hemostatic management based on the Rapid Thromboelastography (R-TEG) variable activated clotting time (ACT) of XABAN patients with ongoing bleedings or in need for acute surgical intervention, affected patient outcome. A total of 343 XABAN patients were included in the main analysis together with 50 healthy volunteers to validate the reference value for ACT. An ACT >120 s (s) was defined as having XABAN-induced coagulopathy. Sixty-five percent of the XABAN patients presented with R-TEG ACT within the normal reference. Patients with XABAN-induced coagulopathy had a significantly increased risk of severe bleeding. Significantly more patients with extra-cerebral bleeding (ECB) and ACT above 120 s were transfused with five red blood cell (RBC) units or more compared to patients with ACT at 120 s or below (17% vs. 3%, p <.05). Significantly more XABAN-patients with ACT above 120 s received pro-hemostatic intervention with prothrombin complex concentrate (PCC) when compared to those with ACT at 120 s or below (ECB: 2% vs. 8%, p =.03, intracranial hemorrhage: 25% vs. 68%, p <.00). Patients who received PCC had a higher 30- and 90-day mortality compared to the rest of the cohort (16% vs. 6%, p = .02 and 21% vs. 7%, p =.00). Patients with XABAN-induced coagulopathy as evaluated by R-TEG ACT presented with more severe bleeding and higher transfusion requirements when compared to those with ACT in the normal range. This suggests that R-TEG ACT measurement in XABAN patients with active hemorrhage or in need for acute surgery may be of clinical value.

Preoperative high-dose glucocorticoids for early recovery after liver resection: randomized double-blinded trial

BACKGROUND

Glucocorticoids modulate the surgical stress response. Previous studies showed that high-dose preoperative glucocorticoids reduce levels of postoperative inflammatory markers and specific biomarkers of liver damage compared with placebo, and suggested a reduced complication rate and shorter hospital stay after liver surgery. However, there are no studies with a clinical primary outcome or of early recovery outcomes. The aim of this study was to investigate whether a single high dose of preoperative glucocorticoid reduces complications in the immediate postoperative phase after liver surgery.

METHODS

This was a single-centre, double-blinded, parallel-group RCT investigating preoperative methylprednisolone 10 mg/kg (high dose) versus dexamethasone 8 mg (standard-dose postoperative nausea prophylaxis) in patients scheduled for open liver resection. The primary outcome was number of patients with a complication in the postanaesthesia care unit; secondary outcomes included duration of hospital stay, pain and nausea during admission, and 30-day morbidity.

RESULTS

A total of 174 patients (88 in high-dose group, 86 in standard-dose group) were randomized and analysed (mean(s.d.) age 65(12) years, 67.2 per cent men); 31.6 per cent had no serious co-morbidities and 25.3 per cent underwent major liver resection. Complications occurred in the postanaesthesia care unit in 51 patients (58 per cent) in the high-dose group and 58 (67 per cent) in the standard-dose group (risk ratio 0.86, 95 per cent c.i. 0.68 to 1.08; P = 0.213). Median duration of hospital stay was 4 days in both groups (P = 0.160). Thirty-day morbidity and mortality rates were similar in the two groups.

CONCLUSION

A high dose of preoperative glucocorticoids did not reduce acute postoperative complications after open liver resection compared with a standard dose. Registration number: NCT03403517 (http://www.clinicaltrials.gov); EudraCT 2017-002652-81 (https://eudract.ema.europa.eu/).

Effect of pre-operative methylprednisolone on orthostatic hypotension during early mobilization after total hip arthroplasty

BACKGROUND

Orthostatic hypotension (OH) and intolerance (OI) are common after total hip arthroplasty (THA) and may delay early mobilization. The pathology of OH and OI includes a dysregulated post-operative vasopressor response, by a hitherto unknown mechanism. We hypothesized that OI could be related to the inflammatory stress response which is inhibited by steroid administration. Consequently, this study evaluated the effect of a pre-operative high-dose methylprednisolone on OH and OI early after THA.

METHODS

Randomized, double-blind, placebo-controlled study in 59 patients undergoing elective unilateral THA with spinal anesthesia and a standardized multimodal analgesic regime. Patients were allocated (1 : 1) to pre-operative intravenous (IV) methylprednisolone (MP) 125 mg or isotonic saline (C). OH, OI and cardiovascular responses to sitting and standing were evaluated using a standardized mobilization protocol pre-operatively, 6, and 24 h after surgery. Systolic and diastolic arterial pressure and heart rate were measured non-invasively (Nexfin^® ). The systemic inflammation was monitored by the C-reactive protein (CRP) response.

RESULTS

At 6 h post-operatively, 11 (38%) versus 11 (37%) patients had OH in group MP and group C, respectively (RR 1.02 (0.60 to 1.75; P = 1.00)), whereas OI was present in 9 (31%) versus 13 (43%) patients (RR 0.76 (0.42 to 1.36; P = 0.42)), respectively. At 24 h post-operatively, the prevalence of OH and OI did not differ between groups, though CRP levels were significantly reduced in group MP (P < 0.001).

CONCLUSION

Pre-operative administration of 125 mg methylprednisolone IV did not reduce OH or OI compared with placebo despite a reduced inflammatory response.

No Effect of a Bipolar Sealer on Total Blood Loss or Blood Transfusion in Nonseptic Revision Knee Arthroplasty-A Prospective Study With Matched Retrospective Controls

BACKGROUND

Postoperative anemia is frequent after revision of total knee arthroplasty (TKA) with reported transfusion rates up to 83%. Despite increased efforts of reducing blood loss and enhancing fast recovery within the fast-track setup, a considerable transfusion rate is still evident. The aim of this study was therefore to evaluate the effect of a bipolar sealer on blood loss and transfusion in revision TKA.

METHODS

In this single-center prospective cohort study with retrospective controls, 51 patients were enrolled in a fast-track setup for revision TKA without the use of a tourniquet. Twenty-five prospectively enrolled patients received treatment with both a bipolar sealer and electrocautery, whereas 26 patients had received treatment with a conventional electrocautery only in the retrospective group.

RESULTS

No significant differences were found neither for calculated blood loss, with 1397 (standard deviation, ± 452) mL in the bipolar sealer group vs 1452 (SD, ± 530) mL in the control group (P = .66), nor for blood transfusion rates of 53% and 46% (P = .89), respectively. Four controls were readmitted within 90 days follow-up.

CONCLUSION

The use of a bipolar sealer in a TKA revision setting without the use of a tourniquet did not reduce blood loss or blood transfusion rates.

Combined Intra-Articular and Intravenous Tranexamic Acid Reduces Blood Loss in Total Knee Arthroplasty: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

In total knee arthroplasty, both intravenous (IV) and intra-articular (IA) administration of tranexamic acid (TXA) have been shown to reduce blood loss in several randomized controlled trials, although routine use of systemic TXA is considerably more common. However, to our knowledge, the additional benefit of IA administration of TXA when combined with IV administration, without the use of a tourniquet, has not been previously investigated. Thus, the aim of this study was to evaluate whether combined IV and IA administration of TXA reduced total blood loss compared with IV-only administration of TXA.

METHODS

In this randomized, double-blind, placebo-controlled trial, 60 patients scheduled for total knee arthroplasty were randomized to one of two interventions. The TXA IV and IA group received combined administration of TXA consisting of 1 g administered intravenously preoperatively and 3 g diluted in 100 mL of saline solution administered intra-articularly after closure of the capsule. The TXA IV and placebo group received 1 g of TXA administered intravenously only and 100 mL of saline solution administered intra-articularly. IA TXA was administrated through a needle. The primary outcome was the 24-hour calculated blood loss. Secondary outcomes were blood loss on postoperative day 2, thromboembolic complications, and transfusion rate. Blood loss was calculated by hemoglobin differences using the Gross formula.

RESULTS

Data on the primary outcome were available for all 60 included patients. Baseline characteristics were comparable between the allocation groups. The mean 24-hour blood loss (and standard deviation) was 466 ± 313 mL in the TXA IV and IA group compared with 743 ± 358 mL in the TXA IV and placebo group; treatment effect (difference), 277 mL (95% confidence interval [CI], 103 to 451 mL) (p = 0.002). Second-day blood loss was 644 ± 382 mL in the TXA IV and IA group compared with 1017 ± 519 mL in the TXA IV and placebo group; treatment effect, 373 mL (95% CI, 132 to 614 mL) (p = 0.003). No thromboembolic complications were observed within 90 days postoperatively.

CONCLUSIONS

The combined administration of IV and IA TXA resulted in a clinically relevant reduction in blood loss of 37% compared with IV TXA alone both at 24 hours postoperatively and on postoperative day 2. No thromboembolic complications were observed.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Postoperative anemia and early functional outcomes after fast-track hip arthroplasty: a prospective cohort study

BACKGROUND

Postoperative anemia is prevalent in fast-track hip arthroplasty (THA) where patients are mobilized and discharged early, but whether anemia impairs functional recovery after discharge has not been adequately evaluated previously. This study aimed to evaluate whether postoperative anemia influenced recovery of mobility and quality of life (Qol) during the first 2 weeks after discharge from THA.

STUDY DESIGN AND METHODS

This was a prospective observational study in 122 THA patients more than 65 years of age. Mobility and Qol were assessed pre- and postoperatively by the 6-minute walk test (6MWT; primary outcome), the timed up-and-go test, and the FACT-anemia subscale. Twenty-four-hour mobility at home was assessed by activity monitoring on Days 1 to 6 after discharge. Hemoglobin (Hb) at discharge (HbD) and the Hb decrease from preoperatively (ΔHb) were compared to mobility and Qol the first 2 weeks after discharge using bivariate and multivariate linear regression.

RESULTS

Mean (±SD) HbD and ΔHb values were 11.1 (±1.4) and 2.8 (±1.2) g/dL and correlated weakly to 6MWT 2 weeks after discharge (r = 0.23 and r = -0.20 respectively; p < 0.05) but HbD levels were not correlated to other mobility or Qol measures. After adjustment for preoperative patient-related factors, HbD explained 6% (95% confidence interval, 0%-9%; p < 0.05) of the variation in 6MWT recovery.

CONCLUSION

Despite a weak, but significant, correlation between postoperative Hb and the recovery of 6MWT, all other mobility and Qol measures were not influenced by postoperative Hb. Thus, moderate postoperative anemia has limited impact on early postdischarge functional recovery after fast-track THA.

Decreased heart rate variability responses during early postoperative mobilization--an observational study

BACKGROUND

Intact orthostatic blood pressure regulation is essential for early mobilization after surgery. However, postoperative orthostatic hypotension and intolerance (OI) may delay early ambulation. The mechanisms of postoperative OI include impaired vasopressor responses relating to postoperative autonomic dysfunction. Thus, based on a previous study on haemodynamic responses during mobilization before and after elective total hip arthroplasty (THA), we performed secondary analyses of heart rate variability (HRV) and aimed to identify possible abnormal postoperative autonomic responses in relation to postural change.

METHODS

A standardized mobilization protocol before, 6 and 24 h after surgery was performed in 23 patients scheduled for elective THA. Beat-to-beat arterial blood pressure was measured by photoplethysmography and HRV was derived from pulse wave interbeat intervals and analysed in the time and frequency domain as well as by non-linear analysis using sample entropy

RESULTS

Before surgery, arterial pressures and HR increased upon standing, while HRV low (LF) and high frequency (HF) components remained unchanged. At 6 and 24 h after surgery, resting total HRV power, sample entropy and postural responses in arterial pressures decreased compared to preoperative conditions. During standing HF variation increased by 16.7 (95 % CI 8.0-25.0) normalized units (nu) at 6 h and 10.7 (2.0-19.4) nu at 24 h compared to the preoperative evaluation. At 24 h the LF/HF ratio decreased from 1.8 (1.2-2.6) nu when supine to 1.2 (0.8-1.8) nu when standing.

CONCLUSIONS

This study observed postoperative autonomic cardiovascular dysregulation that may contribute to limited HRV responses during early postoperative mobilization.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01089946.

Preoperative anaemia and newly diagnosed cancer 1 year after elective total hip and knee arthroplasty

BACKGROUND

Preoperative anaemia is a well-established risk factor for use of blood transfusions and postoperative morbidity. Consequently, focus on preoperative evaluation of haemoglobin levels is increasing. In this context, iron deficiency anaemia may be a symptom of undiscovered gastrointestinal (GI) cancer requiring further investigation. However, the association between preoperative anaemia and cancer 1 year after elective total hip (THA) and total knee arthroplasty (TKA) is unknown. We evaluated 1-year cancer diagnoses, particularly GI cancers, in anaemic and non-anaemic THA and TKA patients.

STUDY DESIGN AND METHODS

A prospective database on preoperative patient characteristics from six Danish orthopaedic centres was cross-referenced with the Danish Cancer Registry for information on diagnoses of new cancers 1 year after surgery. Crude cancer risk estimates were calculated using chi-square and Fisher's exact test in the total study cohort. Adjusted risk estimates were obtained using propensity scores and the Mantel-Haenzel statistic.

RESULTS

Of 5400 procedures, 731 (13·5%) were in anaemic patients. These were older and had more comorbidity than non-anaemic patients. There were 17 (2·3%) and 79 (1·6%) new cancers in anaemic and non-anaemic patients, respectively (OR: 1·38; 95% CI: 0·81-2·35, P = 0·228). After propensity matching of 661 anaemic and 1305 non-anaemic patients, we found no association between preoperative anaemia and cancer (OR: 0·94; 95% CI: 0·51-1·73, P = 0·837) or with GI cancers specifically (OR: 0·80; 95% CI: 0·25-2·56, P = 0·707).

CONCLUSION

Preoperative anaemia per se may not be related to being diagnosed with cancer 1 year after THA and TKA. The optimal criteria for preoperative referral of anaemic patients to gastroenterologist in elective THA and TKA need further investigation.

Transfusion-related mortality after primary hip arthroplasty--an analysis of mechanisms and confounders

BACKGROUND AND OBJECTIVES

Bleeding and postoperative anaemia after total hip arthroplasty (THA) may trigger transfusion of red blood cells (RBC). However, large observational studies have reported associations between RBC transfusion and increased postoperative morbidity and mortality. As major bleeding or severe postoperative anaemia is intrinsically linked with RBC transfusion, direct causality between transfusion and adverse outcomes remains unclear. This study aimed to identify possible relations between RBC transfusion, severe bleeding or anaemia and mortality in all patients who died <90 days after THA in Denmark in 2008.

MATERIALS AND METHODS

Nationwide review of patient records. Cases of adverse transfusion events, infections following transfusion, severe perioperative bleeding or anaemia and possible causal relations to mortality were identified by two independent reviewers.

RESULTS

Of 6932 THA patients, 45 (0·6%) were transfused within 30 days and died <90 days from surgery. Three patients (7%) died from causes possibly related to either severe anaemia, major bleeding alone or major bleeding with transfusion-related acute lung injury, while five (11%) died from infections occurring after RBC transfusion. Mortality in the remaining 37 patients (82%) was of unknown cause (nine patients) or related to patient or surgical factors (28 patients).

CONCLUSION

Transfusion-related mortality after THA included cases of major perioperative bleeding or severe postoperative anaemia with delayed RBC transfusion in addition to possible complications to RBC transfusion per se. Future studies should account for pretransfusion haemoglobin and perioperative blood loss when evaluating RBC transfusion-associated outcomes after surgery.

[Blood transfusion in major orthopaedic surgery]

Hip and knee surgery is associated with a relatively large bleeding and a need for perioperative transfusion. Postoperative anaemia may delay recovery, but transfusion carries inherent risks. However, only few randomised controlled studies evaluating the effects of different transfusion triggers have been performed in orthopaedic surgery. The majority of these studies suffer from methodological weaknesses and have not been performed in a fast-track setting. Thus, large randomised studies evaluating a restrictive versus a liberal transfusion strategy in a procedure-specific setup are needed.

Transfusion practice in hip arthroplasty--a nationwide study

BACKGROUND AND OBJECTIVES

The optimal transfusion strategy in hip arthroplasty remains controversial despite existing guidelines. The aim of this study was to evaluate the transfusion practice in patients undergoing primary total hip arthroplasty (THA) or revision total hip arthroplasty (RTHA) in Denmark.

MATERIALS AND METHODS

We performed a retrospective cohort study of all patients undergoing THA or RTHA in Denmark in 2008. Primary outcomes were intercentre variation in red blood cell (RBC) transfusion rates and the timing of transfusion related to surgery.

RESULTS

Six thousand nine hundred thirty-two THA patients and 1132 RTHA patients were included for analysis of which 1674 (24%) THA and 689 (61%) RTHA patients received RBC transfusion. Of these, 47% of THA and 73% of RTHA patients received transfusion on the day of surgery. Transfusion rates between centres varied from 7 to 71% and between 26 and 85% in THA and RTHA patients, respectively. Patients receiving RBC transfusion had longer length of stay and for THA patients an increased odds-ratio (5·5) of death within 90 days.

CONCLUSION

Despite established guidelines, RBC transfusion practice in hip arthroplasty remains highly variable between Danish hospitals. The effect of RBC transfusion on outcome after hip arthroplasty should be established in prospective randomized controlled trials.

Goal-directed fluid therapy: stroke volume optimisation and cardiac dimensions in supine healthy humans

BACKGROUND

Based on maximisation of cardiac stroke volume (SV), peri-operative individualised goal-directed fluid therapy improves patient outcome. It remains, however, unknown how fluid therapy by this strategy relates to filling of the heart during supine rest as reference for the anaesthetised patient and whether the heart becomes distended. To answer these questions, this study related SV to the diastolic filling of the heart while varying central blood volume (CBV) between hypo- and hyper-volaemia, simulating bleeding, and fluid loading, respectively, when exposing healthy human subjects to head-up (HUT) and head-down tilt (HDT).

METHODS

Twelve healthy volunteers underwent graded tilt from 20 degrees HDT to 30 degrees HUT. The end-diastolic dimensions of the heart were assessed by transthoracic echocardiography with independent evaluation of SV by Modelflow. The CBV was monitored by thoracic electrical admittance, central venous oxygenation and pressure, and arterial plasma atrial natriuretic peptide. Also, muscle and brain oxygenation were assessed by near infrared spectroscopy (n=7).

RESULTS

The HUT reduced the mentioned indices of CBV, the end-diastolic dimensions of the heart, and SV. Conversely, HDT-enhanced tissue oxygenation and the diastolic filling of the heart, but not SV.

CONCLUSIONS

In healthy supine humans, the heart is provided with a volume that is sufficient to secure a maximal SV without distending the heart. The implication for individualised goal-directed fluid therapy is that when a maximal SV is established for patients, cardiac pre-load is comparable to that of supine healthy subjects.

Preload maintenance and the left ventricular response to prolonged exercise in men

This study examined whether left ventricular function was reduced during 3 h of semi-recumbent ergometer cycling at 70% of maximal oxygen uptake while preload to the heart was maintained via saline infusion. Indices of left ventricular systolic function (end-systolic blood pressure-volume relationship, SBP/ESV) and diastolic filling (ratio of early to late peak filling velocities into the left ventricle, E:A) were calculated during recovery and compared with baseline resting data. During exercise in seven healthy, trained male subjects, an arterial catheter allowed continuous assessment of arterial pressure, stroke volume (SV), cardiac output ( ) and an index of contractility (dP/dt(max)). A venous catheter assessed that central venous pressure (CVP) was maintained throughout rest, exercise and 10 min into recovery. Both systolic blood pressure and heart rate (HR) increased with the onset of exercise (from 132 +/- 5 to 185 +/- 19 mmHg and from 66 +/- 9 to 135 +/- 23 beats min(-1); increases from rest to the end of the first 5 min of exercise in SBP and HR, respectively) but systolic blood pressure did not change from 30 to 180 min of exercise ( approximately 150 mmHg), while heart rate only increased by 8 +/- 9 beats min(-1) (means +/- s.d.; P > 0.05). The attenuated increase in HR compared with other studies suggests that the maintained CVP ( approximately 5 mmHg) helped to prevent cardiovascular drift in this protocol. Stroke volume, and dP/dt(max) were all increased with the onset of exercise (from 85 +/- 8 to 120 +/- 18 ml, from 5.4 +/- 1.3 to 16.5 +/- 3.3 l min(-1) and from 14.4 +/- 4 to 28 +/- 8 mmHg s(-1); values from rest to the end of the first 5 min of exercise for SV, and dP/dt(max), respectively) and were maintained during exercise. There was no difference in the SBP/ESV ratio from pre- to postexercise. Conversely, E:A was reduced from 2.0 +/- 0.4 to 1.6 +/- 0.5 postexercise (P < 0.05), returning to normal values at 24 h postexercise. This change in diastolic filling could not be fully explained (r(2) = 0.39) by an increased heart rate and, with CVP unchanged, it is likely to represent some depression of intrinsic relaxation properties of left ventricular myocytes. Three hours of semi-supine cycling resulted in no evidence of a depression in left ventricular systolic function, while left ventricular diastolic function declined postexercise.

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Exercise challenges cerebral autoregulation (CA) by a large increase in pulse pressure (PP) that may make systolic pressure exceed what is normally considered the upper range of CA. This study examined the relationship between systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) and systolic ( Vs), diastolic ( Vd). and mean ( Vm) middle cerebral artery (MCA) blood flow velocity during mild, moderate, and heavy cycling exercise. Dynamic CA and steady-state changes in MCA V in relation to changes in arterial pressure were evaluated using transfer function analysis. PP increased by 37% and 57% during moderate and heavy exercise, respectively ( P < 0.05), and the pulsatility of MCA V increased markedly. Thus exercise increased MCA Vm and Vs ( P < 0.05) but tended to decrease MCA Vd ( P = 0.06). However, the normalized low-frequency transfer function gain between MAP and MCA Vm and between SBP and MCA Vs remained unchanged from rest to exercise, whereas that between DBP and MCA Vd increased from rest to heavy exercise ( P < 0.05). These findings suggest that during exercise, CA is challenged by a rapid decrease rather than by a rapid increase in blood pressure. However, dynamic CA remains able to modulate blood flow around the exercise-induced increase in MCA Vm, even during high-intensity exercise.