Plasma pro-atrial natriuretic peptide to estimate fluid balance during open and robot-assisted esophagectomy: a prospective observational study

Mid‐regional plasma pro‐atrial natriuretic peptide and stroke volume responsiveness for detecting deviations in central blood volume following major abdominal surgery

Background

A reduced central blood volume is reflected by a decrease in mid‐regional plasma pro‐atrial natriuretic peptide (MR‐proANP), a stable precursor of ANP, and a volume deficit may also be assessed by the stroke volume (SV) response to head‐down tilt (HDT). We determined plasma MR‐proANP during major abdominal procedures and evaluated whether the patients were volume responsive by the end of the surgery, taking the fluid balance and the crystalloid/colloid ratio into account.

Methods

Patients undergoing pancreatic (n = 25), liver (n = 25), or gastroesophageal (n = 38) surgery were included prospectively. Plasma MR‐proANP was determined before and after surgery, and the fluid response was assessed by the SV response to 10^° HDT after the procedure. The fluid strategy was based mainly on lactated Ringer's solution for gastroesophageal procedures, while for pancreas and liver surgery, more human albumin 5% was administered.

Results

Plasma MR‐proANP decreased for patients undergoing gastroesophageal surgery (−9% [95% CI −3.2 to −15.3], p = .004) and 10 patients were fluid responsive by the end of surgery (∆SV > 10% during HDT) with an administered crystalloid/colloid ratio of 3.3 (fluid balance +1389 ± 452 ml). Furthermore, plasma MR‐proANP and fluid balance were correlated (r = .352 [95% CI 0.031–0.674], p < .001). In contrast, plasma MR‐proANP did not change significantly during pancreatic and liver surgery during which the crystalloid/colloid ratio was 1.0 (fluid balance +385 ± 478 ml) and 1.9 (fluid balance +513 ± 381 ml), respectively. For these patients, there was no correlation between plasma MR‐proANP and fluid balance, and no patient was fluid responsive.

Conclusion

Plasma MR‐proANP was reduced in fluid responsive patients by the end of surgery for the patients for whom the fluid strategy was based on more lactated Ringer's solution than human albumin 5%.

Effect of adrenaline on serum mid-regional pro-atrial natriuretic peptide and central blood volume

New Findings

What is the central question in this study?

Atrial natriuretic peptide (ANP) is secreted in response to atrial wall distension and thus allows for evaluation, albeit indirect, of the central blood volume. Adrenaline has chronotropic and inotropic effects. We evaluated whether the chronotropic and inotropic effects of adrenaline were reflected in mid‐regional proANP.

What is the main finding and its importance?

Central blood volume remained stable with infusion of adrenaline and yet mid‐regional proANP increased. Thus, the chronotropic and inotropic state of the heart or adrenaline directly induces release of ANP variants from the myocytes.

Abstract

Atrial natriuretic peptide (ANP) has vasodilatory, natriuretic and diuretic properties. It is secreted in response to atrial wall distension and thereby provides an indirect evaluation of central blood volume (CBV). Adrenaline has chronotropic and inotropic effects that increase cardiac output. In the present study, we evaluated whether these effects were influenced by an increase in CBV and reflected in mid‐regional proANP (MR‐proANP) concentrations in the circulation, a stable proxy marker of bioactive ANP. Changes in CBV were evaluated by thoracic electrical admittance and haemodynamic variables monitored by pulse‐contour analysis during two intervals with graded infusion of adrenaline. Adrenaline infusion increased heart rate (by 33 ± 18%) and stroke volume (by 6 ± 13%), hence cardiac output (by 42 ± 23%; all P < 0.05). The increase in cardiac output did not result from an increase in CBV, because thoracic electrical admittance remained stable (−3 ± 17%; P = 0.230). Serum MR‐proANP concentrations were increased (by 26 ± 25%; P < 0.001) by adrenaline infusion and remained elevated 60 min postinfusion. We conclude that MR‐proANP in the circulation is affected not only by CBV, but also by increased chronotropy/inotropy of the heart, or that adrenaline directly induces release of ANP variants from the myocytes.

Dexmedetomidine does not compromise neuronal viability, synaptic connectivity, learning and memory in a rodent model

Recent animal studies have drawn concerns regarding most commonly used anesthetics and their long-term cytotoxic effects, specifically on the nervous tissue. It is therefore imperative that the search continues for agents that are non-toxic at both the cellular and behavioural level. One such agent appears to be dexmedetomidine (DEX) which has not only been found to be less neurotoxic but has also been shown to protect neurons from cytotoxicity induced by other anesthetic agents. However, DEX's effects on the growth and synaptic connectivity at the individual neuronal level, and the underlying mechanisms have not yet been fully resolved. Here, we tested DEX for its impact on neuronal growth, synapse formation (in vitro) and learning and memory in a rodent model. Rat cortical neurons were exposed to a range of clinically relevant DEX concentrations (0.05-10 µM) and cellular viability, neurite outgrowth, synaptic assembly and mitochondrial morphology were assessed. We discovered that DEX did not affect neuronal viability when used below 10 µM, whereas significant cell death was noted at higher concentrations. Interestingly, in the presence of DEX, neurons exhibited more neurite branching, albeit with no differences in corresponding synaptic puncta formation. When rat pups were injected subcutaneously with DEX 25 µg/kg on postnatal day 7 and again on postnatal day 8, we discovered that this agent did not affect hippocampal-dependent memory in freely behaving animals. Our data demonstrates, for the first time, the non-neurotoxic nature of DEX both in vitro and in vivo in an animal model providing support for its utility as a safer anesthetic agent. Moreover, this study provides the first direct evidence that although DEX is growth permissive, causes mitochondrial fusion and reduces oxygen reactive species production, it does not affect the total number of synaptic connections between the cortical neurons in vitro.

The central blood volume as measured by thoracic electrical impedance and plasma proANP is not compromised by donation of 900 mL of blood in men

OBJECTIVES

To evaluate whether the donation of 900 mL of blood reduces the central blood volume (CBV) assessed by thoracic electrical impedance (TI) and plasma pro-atrial natriuretic peptide (proANP).

BACKGROUND

Donation of 450 mL of blood carries a 1% risk of a vasovagal reaction. Withdrawal of 900 mL of blood decreases cardiac output; however, the effect on CBV remains unknown.

METHODS/MATERIALS

A randomised, single-blinded, placebo-controlled, crossover design was used, where 21 healthy semi-recumbent men donated 2 × 450 mL blood or were sham-phlebotomised. Changes in CBV were estimated by proANP and TI at 1.5 (TI_1.5 ) and 100 (TI₁₀₀ ) kHz, reflecting extracellular volume and (regional) total body water, respectively, and the index value (IDX; 1/T_1.5 -1/TI₁₀₀ ) was used to estimate changes in intracellular (red cell) volume. Systolic, diastolic and mean arterial blood pressure; heart rate; stroke volume; cardiac output; and systemic vascular resistance were monitored. After completion of the study, 1000 mL of isotonic saline was infused.

RESULTS

Changes (mean% ± SD) in TI_1.5 , TI₁₀₀ and IDX were similar after 450 mL (-0.2 ± 1.6%, 0.0 ± 1.1%, -0.4 ± 10.1%) and 900 mL (0.1 ± 1.6%, 0.2 ± 1.5% and -2.0 ± 15.8%) of blood donation compared to after a sham donation of 450 mL (-0.9 ± 1.2%, -0.5 ± 1.5% and -0.1 ± 6.1%) and 900 mL (-1.2 ± 1.5%, -0.6 ± 1.3% and 0.5 ± 9.9%). In addition, changes in plasma proANP were similar after 450 and 900 mL of blood donation (-0.8 ± 6.7% and -7.6 ± 7.9%) as after sham donations (1.3 ± 7.3% and -4.5 ± 5.6%). Monitoring haemodynamic variables revealed that stroke volume decreased after the donation of 900 mL of blood (-12 ± 12 mL) compared to sham donations.

CONCLUSION

During a 900-mL blood loss in semi-recumbent men, CBV measured by TI and plasma proANP is not affected.

Hypervolemia does not cause degradation of the endothelial glycocalyx layer during open hysterectomy performed under sevoflurane or propofol anesthesia

BACKGROUND

Fluid-induced hypervolemia may stimulate the release of natriuretic peptides and cause degradation (shedding) of the endothelial glycocalyx layer. Sevoflurane is believed to protect the glycocalyx, but the importance of using sevoflurane to prevent shedding during routine surgery is unclear.

METHODS

The plasma concentrations of brain natriuretic peptide and two biomarkers of glycocalyx shedding, syndecan-1, and heparan sulfate, were measured in 26 patients randomized to receive general anesthesia with sevoflurane or propofol during open abdominal hysterectomy. The fluid therapy consisted of 25 mL/kg (approximately 2 L) of Ringer´s lactate over 30 minutes. Blood hemoglobin and plasma albumin were used to indicate plasma volume expansion and capillary leakage.

RESULTS

The plasma concentrations of brain natriuretic peptide and shedding products showed low levels throughout the surgery (median brain natriuretic peptide, 21 ng/L; syndecan-1, 12.9 ng/mL; and heparan sulfate, 6.5 µg/mL), but the heparan sulfate concentration increased 2 hours post-operatively (to 17.3 µg/mL, P < .005). No differences were noted between the propofol and sevoflurane groups in any of the measured parameters. Albumin was apparently recruited to the bloodstream during the first 20 minutes, when the intravascular retention of infused fluid was almost 100%. The urine flow was <1 mL/min, despite the vigorous volume loading.

CONCLUSIONS

No relevant elevations of brain natriuretic peptide or degradation products of the glycocalyx layer were observed when hypervolemia was induced during open abdominal hysterectomy performed with sevoflurane or propofol anesthesia. Plasma volume expansion from Ringer´s lactate was pronounced.

Effect of hypotensive hypovolemia and thoracic epidural anesthesia on plasma pro-atrial natriuretic peptide to indicate deviations in central blood volume in pigs: a blinded, randomized controlled trial

Purpose

Changes in plasma pro-atrial natriuretic peptide (proANP) may indicate deviations in the central blood volume (CBV). We evaluated the plasma proANP response to hypotensive hypovolemia under the influence of thoracic epidural anesthesia (TEA) in pigs. We hypothesized that plasma proANP would decrease in response to hypotensive hypovolemia and that TEA would aggravate the proANP response, reflecting a further decrease in CBV.

Design

Randomized, blinded, controlled trial.

Setting

A university-affiliated experimental facility.

Participants

Twenty pigs randomized to administration of saline (placebo) or bupivacaine with morphine (TEA) in the epidural space at Th8-Th10.

Interventions

Relative hypovolemia was established by an inflatable Foley catheter positioned in the inferior caval vein just below the heart (caval obstruction), and hemorrhage-induced hypovolemia was by withdrawal of blood from the femoral artery, both aiming at a mean arterial pressure (MAP) of 50–60 mmHg. Hemodynamic variables and plasma proANP were determined before and after the interventions.

Results

Caval obstruction and withdrawal of blood reduced MAP to 50–60 mmHg. Accordingly, cardiac output, central venous pressure, and mixed venous oxygen saturation decreased (p<0.05). Yet, plasma proANP was stable after both caval obstruction (TEA: 72 [63–78] to 80 pmol/L [72–85], p=0.09 and placebo: 64 [58–76] to 69 pmol/L [57–81], p=0.06) and withdrawal of blood (TEA: 74 [73–83] to 79 pmol/L [77–87], p=0.07 and placebo: 64 [56–77] to 67 pmol/L [58–78], p=0.15).

Conclusion

Plasma proANP was stable in response to relative and hemorrhage-induced hypovolemia to a MAP of 50–60 mmHg, and the response was independent of TEA. The findings suggest that alterations in plasma proANP do not follow deviations in CBV during hypotensive hypovolemia in pigs.

Effect of early versus delayed activation of thoracic epidural anesthesia on plasma pro-atrial natriuretic peptide to indicate deviations in central blood volume during esophagectomy

BACKGROUND AND OBJECTIVES

A side effect to thoracic epidural anesthesia (TEA) is hypotension induced by central hypovolemia. This study addressed whether early activation (EA) versus late activation (LA) of TEA affects plasma pro-atrial natriuretic peptide (proANP) reflecting deviations in the central blood volume (CBV). We hypothesized that EA TEA would reduce plasma proANP, thus reflecting a decrease in CBV.

METHODS

A randomized, controlled, single-blinded trial was conducted. Patients undergoing open esophagectomy were randomized to EA (n=25, after induction of general anesthesia) or LA TEA (n=25, after re-established gastric continuity) with the epidural catheter placed at the interspaces Th7-8 or Th8-9. Plasma proANP was determined repetitively along with hemodynamic variables and administration of fluid/vasopressors as postoperative complications were noted.

RESULTS

With EA TEA, plasma proANP decreased following induction of anesthesia to the end of surgery (13%; 113±68 to 99±49 pmol/L; p=0.026), but that was not the case in the LA group (3%; 97±44 to 94±49 pmol/L; p=0.565) despite equal fluid balance (+1584±582 vs +1560±563 mL; p=0.888). Accordingly, the EA group required excessive treatment with vasopressors to maintain MAP >60 mm Hg during surgery (2.7±2 vs 1.6±1.4 ephedrine boluses; p=0.033 and infusion of phenylephrine for 216±86 vs 58±91 min; p<0.001). Plasma proANP and fluid balance were correlated only for EA patients (r=0.44; 95% CI 0.04 to 0.91; p=0.033).

CONCLUSIONS

EA TEA reduces plasma proANP indicating that CBV becomes affected. Based on a correlation between plasma proANP and fluid balance, a 2000 mL volume surplus of lactated Ringer's solution is required to maintain plasma proANP stable during open esophagectomy.

TRIAL REGISTRATION NUMBER

2014-002036-14 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=2014-002036-14).