Effect of thoracic epidural anaesthesia on ventilation-perfusion distribution and intrathoracic blood volume before and after induction of general anaesthesia

Current Status of Neuraxial and Paravertebral Blocks for Adult Cardiac Surgery

Cardiac surgeries are known to produce moderate to severe pain. Pain management has traditionally been based on intravenous opioids. Poorly controlled pain can result in increased incidence of respiratory complications such as atelectasis and pneumonia leading to prolonged intubation and intensive care unit length of stay and subsequent prolonged hospital stay. Adequate perioperative analgesia improves hemodynamics and immunologic responses, which would result in better outcomes after cardiac surgery. Opioid sparing "Enhanced Recovery After Surgery" protocols are increasingly being incorporated into cardiac surgeries. This will reduce opioid requirements and opioid-related side effects and facilitate fast-tracking of patients. Regional analgesia can be provided by neuraxial blocks, fascial plane blocks, peripheral nerve blocks, or simply by the infiltration of the wound with local anesthetics for cardiac surgery. Neuraxial analgesia is provided through epidural, spinal, and paravertebral routes. Though they are being replaced by peripheral fascial plane blocks, epidural and spinal analgesia are still being used in some centers. In this article, neuraxial forms of analgesia are focused. We sought to review epidural analgesia and its impact in suppressing hemodynamic stress response, reducing pulmonary complications, and development of chronic pain. The relationship between intraoperative heparinization and potential neuraxial hematoma is discussed. Other neuraxial options such as spinal and paravertebral analgesia and their usefulness, benefits, and limitations are also reviewed.

Hypotension Associated with MTS is Aggravated by Early Activation of TEA During Open Esophagectomy

Objective

A mesenteric traction syndrome (MTS) is elicited by prostacyclin (PGI₂)-induced vasodilation and identified by facial flushing, tachycardia, and hypotension during abdominal surgery. We evaluated whether thoracic epidural anesthesia (TEA) influences the incidence of MTS.

Design

Randomized, blinded controlled trial.

Setting

Single-center university hospital.

Participants

Fifty patients undergoing open esophagectomy.

Interventions

Patients were randomized to either early (EA, after induction of general anesthesia) or late activation of TEA (LA, after re-established gastric continuity). Plasma 6-keto-PGF_1α, a stable metabolite of PGI₂ and interleukine-6 (IL6) were measured in plasma during surgery along with hemodynamic variables and MTS graded according to facial flushing together with plasma C-reactive protein on the third post-operative day.

Results

Forty-five patients met the inclusion criteria. Development of MTS tended to be more prevalent with EA (n=13/25 [52%]) than with LA TEA (n=5/20 [25%], p=0.08). For patients who developed MTS, there was a transient increase in plasma 6-keto-PGF_1α by 15 min of surgery and plasma IL6 (p<0.001) as C-reactive protein (P<0.009) increased. EA TEA influenced the amount of phenylephrine needed to maintain mean arterial pressure >60 mmHg in patients who developed MTS (0.16 [0.016–0.019] mg/min vs MTS and LA TEA 0.000 [0.000–0.005] mg/min, p<0.001).

Conclusion

The incidence of MTS is not prevented by TEA in patients undergoing open esophagectomy. On the contrary, the risk of hypotension is increased in patients exposed to TEA during surgery, and the results suggest that it is advantageous to delay activation of TEA. Also, MTS seems to be associated with a systemic inflammatory response, maybe explaining the aggravated post-operative outcome.

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).

Perioperative benefit and outcome of thoracic epidural in esophageal surgery: a clinical review

Surgery for esophageal cancer is a highly stressful and painful procedure, and a significant amount of analgesics may be required to eliminate perioperative pain and blunt the stress response to surgery. Proper management of postoperative pain has invariably been shown to reduce the incidence of postoperative complications and accelerate recovery. Neuraxial analgesic techniques after major thoracic and upper abdominal surgery have long been established to reduce respiratory, cardiovascular, metabolic, inflammatory, and neurohormonal complications.The aim of this review is to evaluate and discuss the relevant clinical benefits and outcome, as well as the possibilities and limits of thoracic epidural anesthesia/analgesia (TEA) in the setting of esophageal resections. A comprehensive search of original articles was conducted investigating relevant literature on MEDLINE, Cochrane reviews, Google Scholar, PubMed, and EMBASE from 1985 to July2017. The relationship between TEA and important endpoints such as the quality of postoperative pain control, postoperative respiratory complications, surgical stress-induced immunosuppression, the overall postoperative morbidity, length of hospital stay, and major outcomes has been explored and reported. TEA has proven to enable patients to mobilize faster, cooperate comfortably with respiratory physiotherapists and achieve satisfactory postoperative lung functions more rapidly. The superior analgesia provided by thoracic epidurals compared to that from parenteral opioids may decrease the incidence of ineffective cough, atelectasis and pulmonary infections, while the associated sympathetic block has been shown to enhance bowel blood flow, prevent reductions in gastric conduit perfusion, and reduce the duration of ileus. Epidural anesthesia/analgesia is still commonly used for major 'open' esophageal surgery, and the recognized advantages in this setting are soundly established, in particular as regards the early recovery from anesthesia, the quality of postoperative pain control, and the significantly shorter duration of postoperative mechanical ventilation. However, this technique requires specific technical skills for an optimal conduction and is not devoid of risks, complications, and failures.

Advantages of Epidural Analgesia on Pulmonary Functions in Liver Transplant Donors

OBJECTIVE

Epidural analgesia (EA) has positive effects on anesthetic requirement, blood loss, postoperative analgesia, and pulmonary function tests (PFTs). The purpose of the present study was to investigate the effect of EA on postoperative PFTs in liver transplant donors (LTDs).

METHODS

In the present study, 66 LTDs were classified as total intravenous anesthesia (TIVA) and TIVA+EA groups. Patient's age, sex, body mass index, induction and maintenance dose of propofol (IDP and MDP), operation duration, forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), FEV₁/FVC ratio, visual analog scale (VAS), atelectasis scores, and lengths of intensive care unit (ICU) and hospital stays were recorded.

RESULTS

In the TIVA+EA group, IPD, MPD, delta-FEV₁ delta-FVC, VAS for all time, atelectasis score and length of hospital stay were significantly lower than in the TIVA group (P < .001 for all). Whereas VAS at the end of the operation was negatively correlated with delta-FEV₁ and delta-FVC (r² = 0.26 P < .001; r² = 0.41 P < .001; respectively), it was positively correlated with atelectasis score and length of ICU stay (r² = 0.49, P < .001; and r² = 0.41, P < .001; respectively). Atelectasis score was positively correlated with length of ICU stay (r² = 0.86, P < .001).

CONCLUSIONS

Reduced anesthetic requirement, better postoperative analgesia, reduced atelectasis score, and preserved PFTs can be provided with the use of EA in LTDs. Positive effects of EA on anesthesia requirement, pain management and pulmonary function are associated with outcomes.

A prospective randomized study of intraoperative thoracic epidural analgesia in off-pump coronary artery bypass surgery

OBJECTIVE

The purpose of this study was to test the hypothesis that general anesthesia (GA) plus thoracic epidural anesthesia (TEA) has no impact on the outcomes of off-pump coronary artery bypass surgery (OPCABs) compared to GA followed by patient-controlled TEA (PCTEA), while GA plus TEA leads to a higher requirement for vasoactive drug use.

METHODS

Sixty-four patients, American Society of Anesthesiologists physical status II and III, who were scheduled for elective OPCABs, were offered an epidural catheter inserted at the T2-3 interspace and then randomized into 1 of 2 groups according to whether TEA was applied intraoperatively. The TEA(perio) group received GA plus TEA, while the TEA(post) group received GA alone. All groups had postoperative PCTEA. The number of requirements for vasoactive drugs and the extubation times were recorded. The analgesic effect was monitored by visual analog scale (VAS) pain scores. Heart rate, blood pressure, and blood gases were also monitored. The data are presented as mean values ± standard deviation, or medians with quartiles.

RESULTS

The proportion of vasoactive drug use was significantly higher in the TEA(perio) group intraoperatively (before or during completion of anastomoses: 59.4 vs. 20.7%, p = 0.004; after completion of anastomoses: 53.1 vs. 17.2%, p = 0.007). There was no statistically significant difference in extubation times or VAS scores between the 2 groups.

CONCLUSIONS

We conclude that GA plus TEA has no impact on the outcomes of OPCABs, while its use leads to a higher requirement for vasoactive drug use. GA followed by PCTEA facilitates the anesthesia administration, while it does not affect the extubation time and the postoperative analgesic effect.

[Nonanalgesic effects of thoracic epidural anesthesia]

Thoracic epidural anesthesia, which has been performed since the 1950s, has progressed from being one analgesic technique among others to its present status as the technique of choice for managing pain after major abdominal and thoracic surgery. In addition to providing effective analgesia, the epidural infusion of local anesthetic agents produces a sympathetic block that offers advantages over other types of pain control, particularly with respect to the cardiovascular, respiratory, and gastrointestinal systems. Thoracic epidural anesthesia provides dynamic pain relief, allowing the patient to resume activity early. It also permits early extubation and is associated with fewer postoperative pulmonary complications, shorter duration of paralytic ileus, and a better response to the stress of anesthesia and surgery. However, meta-analyses have not yet demonstrated that postoperative outcomes are improved. This review describes the nonanalgesic effects of thoracic epidural anesthesia.

Epidural anesthesia and pulmonary function

The epidural administration of local anesthetics can provide anesthesia without the need for respiratory support or mechanical ventilation. Nevertheless, because of the additional effects of epidural anesthesia on motor function and sympathetic innervation, epidural anesthesia does affect lung function. These effects, i.e., a reduction in vital capacity (VC) and forced expiratory volume in 1 s (FEV(1.0)), are negligible under lumbar and low thoracic epidural anesthesia. Going higher up the vertebral column, these effects can increase up to 20% or 30% of baseline. However, compared with postoperative lung function following abdominal or thoracic surgery without epidural anesthesia, these effects are so small that the beneficial effects still lead to an improvement in postoperative lung function. These results can be explained by an improvement in pain therapy and diaphragmatic function, and by early extubation. In chronic obstructive pulmonary disease (COPD) patients, the use of thoracic epidural anesthesia has raised concerns about respiratory insufficiency due to motor blockade, and the risk of bronchial constriction due to sympathetic blockade. However, even in patients with severe asthma, thoracic epidural anesthesia leads to a decrease of about 10% in VC and FEV(1.0) and no increase in bronchial reactivity. Overall, epidural administration of local anesthetics not only provides excellent anesthesia and analgesia but also improves postoperative outcome and reduces postoperative pulmonary complications compared with anesthesia and analgesia without epidural anesthesia.

Thoracic sympathetic block reduces respiratory system compliance

CONTEXT AND OBJECTIVE

Thoracic epidural anesthesia (TEA) following thoracic surgery presents known analgesic and respiratory benefits. However, intraoperative thoracic sympathetic block may trigger airway hyperreactivity. This study weighed up these beneficial and undesirable effects on intraoperative respiratory mechanics.

DESIGN AND SETTING

Randomized, double-blind clinical study at a tertiary public hospital.

METHODS

Nineteen patients scheduled for partial lung resection were distributed using a random number table into groups receiving active TEA (15 ml 0.5% bupivacaine, n = 9) or placebo (15 ml 0.9% saline, n = 10) solutions that also contained 1:200,000 epinephrine and 2 mg morphine. Under general anesthesia, flows and airway and esophageal pressures were recorded. Pressure-volume curves, lower inflection points (LIP), resistance and compliance at 10 ml/kg tidal volume were established for respiratory system, chest wall and lungs. Students t test was performed, including confidence intervals (CI).

RESULTS

Bupivacaine rose 5 +/- 1 dermatomes upwards and 6 +/- 1 downwards. LIP was higher in the bupivacaine group (6.2 +/- 2.3 versus 3.6 +/- 0.6 cmH2O, p = 0.016, CI = -3.4 to -1.8). Respiratory system and lung compliance were higher in the placebo group (respectively 73.3 +/- 10.6 versus 51.9 +/- 15.5, p = 0.003, CI = 19.1 to 23.7; 127.2 +/- 31.7 versus 70.2 +/- 23.1 ml/cmH2O, p < 0.001, CI = 61 to 53). Resistance and chest wall compliance showed no difference.

CONCLUSION

TEA decreased respiratory system compliance by reducing its lung component. Resistance was unaffected. Under TEA, positive end-expiratory pressure and recruitment maneuvers are advisable.

Patterns of changes in arterial PO2 during one-lung ventilation: a comparison between patients with severe pulmonary emphysema and patients with preserved lung function

OBJECTIVES

One-lung ventilation (OLV) during thoracoscopic surgery is associated with a significant decline in arterial PO(2) in patients with severe pulmonary emphysema and patients with preserved lung function. The authors hypothesized that patterns of arterial PO(2) changes are different in these 2 patient groups.

DESIGN

Prospective nonrandomized study.

SETTING

University hospital.

PARTICIPANTS

Twenty-five patients undergoing thoracoscopic interventions: 16 with severe pulmonary emphysema and 9 patients without emphysema.

INTERVENTIONS

Continuous arterial blood gas measurement (PaO(2), PaCO(2), pHa) during OLV of the left lung in left lateral position using the Paratrend 7 blood gas monitoring system (PT7; Pfizer Hospital Products Group, High Wycombe, UK).

MAIN RESULTS

The decrease of PaO(2) was delayed in patients with severe emphysema. Steady state (defined as DeltaPaO(2) <7.5 mmHg/min) was reached after 18 +/- 4 minutes compared with 11 +/- 3 minutes (mean +/- standard deviation) in patients with normal lung function (p = 0.0002). PaO(2) values at steady state were comparable (p = 0.49); the pattern of changes in PaO(2) for the first 15 minutes of left-sided OLV was significantly different between the groups (p = 0.0004). The difference of predicted versus measured PaO(2) at steady state was -48 +/- 160 mmHg for patients with emphysema and -51 +/- 60 mmHg for patients with normal lung function (p = 0.019).

CONCLUSION

During OLV, oxygenation is better preserved for a longer period of time in patients with severe pulmonary emphysema as compared with patients with normal lung function. In contrast to patients without emphysema, prediction of oxygenation during OLV for the individual patient with emphysema is unreliable because of large interindividual differences.

Thoracic epidural anesthesia combined with general anesthesia: the preferred anesthetic technique for thoracic surgery

Thoracic epidural anesthesia (TEA) combined with general anesthesia (GA) as well as total-IV anesthesia (TIVA) are both established anesthetic managements for thoracic surgery. We compared them with respect to hypoxic pulmonary vasoconstriction, shunt fraction and oxygenation during one-lung ventilation. Fifty patients, ASA physical status II-III undergoing pulmonary resection were randomly allocated to two groups. In the TIVA group, anesthesia was maintained with propofol and fentanyl. In the TEA group, anesthesia was maintained with TEA (bupivacaine 0.5%) combined with low-dose concentration 0.3-0.5 vol% of isoflurane (end-tidal). Changing from two-lung ventilation to one-lung ventilation caused a significant increase in cardiac output (CO) in the TIVA group, whereas no change was observed in the TEA group. One-lung ventilation caused significant increases in shunt fraction in both groups which was associated per definition with a significant decrease in PaO(2) in both groups but PaO(2) remained significantly increased in the TEA group (P < 0.05). We conclude that both anesthetic regimens are safe intraoperatively. However, TEA in combination with GA did not impair arterial oxygenation to the same extent as TIVA, which might be a result of the changes in CO. Therefore, patients with preexisting cardiopulmonary disease and impaired oxygenation before one-lung ventilation might benefit from TEA combined with GA.

IMPLICATIONS

Fifty patients underwent lung surgery through the opened chest wall requiring ventilation of only one lung. Patients were randomly assigned to receive either general anesthesia alone or in combination with regional anesthesia via a catheter in the back. Oxygen content in the blood and blood pressure was better maintained in the group receiving the combination of general with regional anesthesia.

PaO2 during anaesthesia and years of smoking predict late postoperative hypoxaemia and complications after upper abdominal surgery in patients without preoperative cardiopulmonary dysfunction

BACKGROUND

The incidence of late postoperative hypoxaemia and complications after upper abdominal surgery is 20-50% among cardiopulmonary healthy patients. Atelectasis development during anaesthesia and surgery is the main hypothesis to explain postoperative hypoxaemia. This study tested the predictive value of PaO2<19 kPa during combined general and thoracic epidural anaesthesia and the preoperative functional residual capacity (FRC) reduction in the 30 degree head tilt-down position for the development of late prolonged postoperative hypoxaemia, PaO2<8.5 kPa for a minimum of 3 out of 4 days, and other complications. Forty patients without cardiopulmonary morbidity, assessed by ECG, spirometry, FRC and diffusion capacity preoperatively, underwent upper abdominal surgery. PaO2 during anaesthesia and preoperative FRC reduction were compared to known risk factors for the development of hypoxaemia and complications: age, pack-years of smoking and duration of operation. The effect of optimizing pulmonary compliance with peroperative positive end-expiratory pressure (PEEP) on postoperative hypoxaemia and complications was evaluated in a blinded and randomized manner.

RESULTS

Late prolonged postoperative hypoxaemia and other complications were found in 37% and 38% of the patients, respectively. Patients with PaO2>19 kPa during anaesthesia with F(I)O2=0.33 exhibited a risk, irrespective of PEEP status, of suffering late prolonged hypoxaemia of 0% (0;23) and patients with PaO2<19 kPa a risk of 52% (32;71), P<0.005. Having smoked more than 20 pack-years was associated with a 47% (19;75) higher incidence of postoperative complications than having smoked less than 20 pack-years, P<0.006.

CONCLUSIONS

PaO2 during anaesthesia and smoked pack-years provide new tools evaluating patients undergoing upper abdominal surgery in order to predict the patients who develop late postoperative hypoxaemia and complications.