Major Liver Surgery and the Anesthesiologist: Towards a Proactive Strategy

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Metadata

Author: Paolo Aseni
Full Title: Major Liver Surgery and the Anesthesiologist: Towards a Proactive Strategy
Category: #articles
Document Tags: hbp part 2
Summary: The text discusses the role of the anesthesiologist in major liver surgery. It emphasizes the importance of a proactive strategy in managing anesthesia during these surgeries. The author, Paolo Aseni, presents insights on optimizing patient care in this context.
URL: https://www.wjgnet.com/2220-3141/full/v13/i2/92751.htm

Highlights

the liver is divided by the falciform ligament into two main lobes—the larger right lobe (75% of the liver mass), and the smaller left lobe (25% of the mass) (View Highlight)
The right lobe includes the quadrate lobe, located between the gallbladder and the fissure for the ligamentum teres hepatis, and the caudate lobe (Spiegel’s lobe), situated between the fissure for the ligamentum venosum Arantii and the inferior vena cava (IVC) (View Highlight)
In 1897, Sir James Cantlie introduced a novel anatomical division of the liver, defining two parts of similar size based on an imaginary line along the middle hepatic vein (MHV). This line extends from the gallbladder fossa to the external border of IVC, dividing the liver into a right lobe (60%) and a left lobe (40%), each independently vascularized from the right and left portal branches. (View Highlight)
Couinaud’s classification divides the liver into eight functional segments (I-VIII), based on the distribution of blood vessels and bile ducts (the segmental pedicle). Each segment is functionally independent and is supplied by the third division branch of the portal vein (PV) (View Highlight)
The hepatic artery (HA) and PV provide the double blood supply to the liver, accounting for 20%-25% of the cardiac output (View Highlight)
The total hepatic blood supply approximates 1500 mL/min: 300 mL from the HA (delivering 50% of the oxygen to the liver) and 1200 mL from the PV flow, which provides the remaining 50% of the oxygen supply (View Highlight)
PV pressure, typically ranging from 5 to 10 mmHg, is higher than the pressure in IVC (View Highlight)
Portal hypertension is defined as a PV pressure > 10 mmHg or a PV-IVC gradient > 4 mmHg (View Highlight)
The caudate lobe possesses its unique venous drainage system (View Highlight)
The liver, whose venous return drains into the right atrium, is extremely sensitive to obstructions in venous outflow (View Highlight)
Prolonged obstruction of hepatic venous outflow leads to an increase in intrahepatic blood volume associated with moderate-to-severe hepatic dysfunction (View Highlight)
liver serves as a significant blood reservoir: during acute hemorrhage, ortho-sympathetic-mediated vasoconstriction can increase circulating blood volume by approximately 25% of the blood loss (View Highlight)
The anatomo-functional unit of the liver is the hepatic lobule, hexagonally shaped and centered around the central vein (a terminal branch of the hepatic vein, also known as the centrolobular vein). Portal spaces (portal triad), containing arterial, portal, and biliary branches, are situated at each corner of the hexagon (View Highlight)
Zone III (pericentral), contiguous with the central vein, is hypo oxygenated and highly susceptible to hemodynamic insults and hypoxia (View Highlight)
Zone III is the primary site for ketogenesis and phase 1 and 2 drug and substance metabolism, including glycuronoconjugation and detoxification processes (View Highlight)
Compared to the traditional open approach, minimally invasive liver resections are associated with reduced blood loss, less postoperative pain, much rare ascitic decompensation, lower incisional hernia rates, faster postoperative recovery, and shorter hospital stays (View Highlight)

New highlights added June 17, 2024 at 3:10 AM

In major liver resections, ensuring a sufficient future liver remnant (FLR) is crucial (View Highlight)
Pre-operative liver volumetry, calculated via computerized tomographic (CT) scan or magnetic resonance imaging (MRI), is mandatory to prevent fatal PHLF. The parenchymal function can be dynamically assessed using indocyanine green (ICG) clearance (View Highlight)
A successful strategy to increase FLR volume involves portal and hepatic vein embolization of the liver portion to be resected, usually performed by interventional radiologists (View Highlight)
In selected cases, a two-stage hepatectomy may be conducted. The first stage involves resecting malignant lesions from the lobe that will be preserved, followed by ligation and sectioning of the main portal branch of the contralateral lobe to induce parenchymal hypertrophy. The second stage entails a planned major liver resection after achieving sufficient hypertrophy. (View Highlight)
ALPPS (Associating Liver Partition and Portal vein ligation for Staged Hepatectomy) - has been proposed[19,20]. This two-stage technique increases the treatment options for otherwise unresectable tumors. In the first stage, the portal branch ipsilateral to the hemiliver to be removed is ligated. Any lesions in the hemiliver to be preserved are resected, and a parenchymal transection along the Cantlie line is performed. Hypertrophy of the lobe to be preserved is usually achieved within about two weeks. The second stage, usually 15 to 20 days later, is undertaken following a CT scan volumetry and is performed when appropriate hypertrophization of the FLR is confirmed. In this second stage, the hemiliver is removed by transecting the artery, the biliary duct, and the hepatic vein. (View Highlight)
Although ALPPS is effective in inducing hypertrophy of the remnant liver, it is associated with high surgical complications and mortality rates (View Highlight)
Anatomic resection is defined as the resection of one or more hepatic segments, sectioning the segmental Glissonian arterial and portal pedicle, and resecting all the dependent parenchyma (View Highlight)
Anatomic resections are associated with shorter surgical times and reduced blood loss compared to non-anatomical resections (View Highlight)
Hepatic resections are classified as minor (involving up to two segments) or major (involving more than two segments) (View Highlight)
In non-anatomical “wedge” resections, the main goal is to preserve liver parenchyma (View Highlight)
Among the surgical maneuvers and manipulations anesthesiologists must be familiar with due to their potential relevant hemodynamic impact are: (1) The surgical “manipulation” of the liver, aiming at the best exposure of the anatomical structures and able to acutely reduce the venous return from the IVC, leading to severe, abrupt arterial hypotension; and (2) selective or total vascular clamping before resection, aimed at reducing bleeding (View Highlight)
Intraoperative ultrasound (US), CUSA Dissector, Ligasure, Argon beam coagulation, and topical hemostatic agents (tissue adhesive and fibrin sealants) are among the innovative surgical hemostatic solutions used to identify vascular structures and reduce surgical bleeding (View Highlight)
The anesthesiologist should be familiar with and master selective (Pringle maneuver) or total vascular exclusion techniques (supra- and infrahepatic clamping of the IVC; aortic clamping), or, in extreme cases, might indicate the use of extracorporeal venovenous bypass to maintain venous return during procedures involving the right atrium or the IVC (usually because of neoplastic atrial or caval thrombi) or in cases of acute juxta-atrial injuries (View Highlight)
Liver surgery, encompassing advanced and complex procedures[17,26], falls into the category of intermediate or high-risk surgical operations, with mortality/major cardiovascular event rates ranging from 1%–3% to ≥ 5% (View Highlight)
Among tools to assess liver function on the rise are the “static” ALBI score[37-41] and the “dynamic” indocyanine green clearance (IGC) (View Highlight)
Methods used to assess residual function after liver resection include: (1) Volumetric assessment (% future liver remnant volume,), with a remnant volume being sufficient if at least 20%–30% of the native volume (or 40% in cases of chemotherapy); and (2) functional assessment, primarily based on IGC clearance, with preoperative R15 (retention rate at 15 minutes) values above 15%-20% indicating a relative surgical contraindication (View Highlight)
A major limitation in using ICG clearance could be serum bilirubin levels > 6 mg/dL, able to introduce a significant bias to the accuracy of the R15 value, leading to an overestimation of the liver function deterioration (View Highlight)
The presence of cirrhosis, if properly assessed, is no longer an absolute contraindication due to advancements in surgical techniques (View Highlight)
Defining the candidate’s frailty and sarcopenia is pivotal, due to the significant impact on both morbidity and mortality (View Highlight)
Functional assessment using the “subjective” definition of metabolic equivalents (METs) or the more objective Duke Activity Status Index (DASI) questionnaire (cutoff score 34) should now be integral to preoperative anesthesiologic evaluation (View Highlight)
Cirrhotic cardiomyopathy, recently redefined, is increasingly diagnosed in liver surgery candidates and warrants particular attention, particularly in cases of moderate-to-severe diastolic dysfunction (View Highlight)
HPS is characterized by varying degrees of hypoxia (mild: PaO2 < 80 mmHg; moderate: PaO2 60-80 mmHg; severe: PaO2 50-60 mmHg; extremely severe: PaO2 < 50 mmHg). It is associated with an increased alveolar-arterial oxygen gradient (> 15 mmHg in room air) due to intrapulmonary vascular dilatation (shunt). Symptoms include dyspnea at rest or upon exertion, with platypnea (dyspnea and desaturation in orthostatic position) and orthodeoxia (reduction of PaO2 from supine to orthostatic position) present in 25%-30% of cases. Screening and further investigation are required for SaO2 < 96% in room air (View Highlight)
PoPH, associated with portal hypertension, is present in 2%-5% of CLD patients and involves anatomic changes in the pulmonary vascular bed and increased circulating pulmonary vasoconstricting agents (e.g., endothelin-1)[58,63,75]. Diagnosis is based on the presence of mean pulmonary pressure (mPAP) > 25 mmHg and pulmonary vascular resistance > 240 dyne/s/cm-5 with central venous pressure (CVP) < 5 mmHg and pulmonary wedge pressure < 15 mmHg (View Highlight)
PoPH is classified as mild (mPAP 25-35 mmHg), moderate (mPAP 35-45 mmHg), or severe (mPAP > 45 mmHg) (View Highlight)
In cases where transthoracic echocardiogram (TTE) estimates systolic pulmonary pressure > 45 to 50 mmHg, consultation with a cardiologist and further investigation with right heart catheterization are mandatory (View Highlight)
Hepatorenal syndrome (HRS, now HRS - AKI), is characterized by intense renal vasoconstriction, requires careful evaluation with hepatologists, and involves treatment with terlipressin and albumin (View Highlight)
Before the development of new AKI criteria[77], HRS was divided into two types, with different prognoses, type 1 having the worst outcome (View Highlight)
Serum creatinine may present interpretative concerns in sarcopenic patients and/or in the hyperbilirubinemic cirrhotic patient, limitations to be considered when assessing preoperative renal function. Often, blood urea nitrogen (BUN) is discrepant with serum creatinine (elevated BUN vs “normal” creatinine), and might provide a more accurate description of renal dysfunction (View Highlight)
The best approach to protect renal function during the perioperative period includes maintaining mean arterial pressure > 65 mmHg, to ensure renal perfusion pressure - and tailoring fluid balance and use of pressors implementing appropriate invasive hemodynamic monitoring (invasive arterial pressure and minimally invasive cardiac output if indicated) (View Highlight)
The use of mannitol and dopamine, although still considered, lacks evidence (View Highlight)
The hemostatic profile of a non-cirrhotic patient undergoing liver surgery is expected to be normal. In cirrhotic patients, however, the profile is not “naturally” anticoagulated , but instead “rebalanced,” with coexisting procoagulant (increased factor VIII and von Willebrand factor, reduced ADAMTS-13, reduced natural anticoagulants like Antithrombin, Protein C, Protein S) and anticoagulant features (reduced synthesis of coagulation factors, hypopiastrinemia, impaired platelet function, hypofibrinogenemia) (View Highlight)
The coagulation profile is often activated (increased d-dimer), with the risk of consumption coagulopathy. Increased fibrinolysis and endogenous heparin-like products may also be observed (View Highlight)
Prolonged PT/INR and aPTT/R do not necessarily imply an increased hemorrhagic risk, but rather an “instability” of the hemostatic balance, which can shift towards a prothrombotic or prohemorrhagic state depending on the type of insult (View Highlight)
In major liver surgery, key objectives of intraoperative anesthesia management include maintaining adequate anesthesia depth and analgesia, core temperature control, cardiometabolic stability (stable circulatory, respiratory, and metabolic profiles), appropriate fluid balance, implementation of active strategies to minimize blood loss (View Highlight)
Evidence suggests that ischemic preconditioning and even “postconditioning” (adaptation to ischemic injury and remodulation of ischemia-reperfusion syndrome) can be facilitated by volatile anesthetics like sevoflurane, isoflurane, and desflurane (View Highlight)
During liver resection surgery, common causes of hemodynamic instability include blood loss during isolation, dissection, and resection, liver mobilization maneuvers (“dislocation”), and compressions or distortions of the IVC, able to impair venous return. Gas embolization, though rare, can occur in cases of very low CVP/extreme hypovolemia during exposure of large venous vessels (View Highlight)
The Pringle maneuver, which involves occlusion of the hepatic vascular pedicle (the portal triad) (inflow occlusion), aims at reducing blood loss, although its effects on morbidity and mortality are unproven at best (but not associated with an increased rate of PHLF) (View Highlight)
The Pringle maneuver may contribute to acute liver injury and could potentially delay regenerative activity. It is associated with a reduction in venous return and CO of about 15%, a change usually well tolerated due to an increase in orthosympathetic tone. Systemic hypotension is uncommon, a modest increase in systolic blood pressure may occur, due to increased systemic vascular resistance (View Highlight)
Clamping can be continuous (15 to 30 min) or intermittent, the latter involving clamping periods of 10 to 15 min followed by declamping periods of 5 to 10 min. During declamping, hepatectomy is usually interrupted, with the section slice compressed with laparotomy patches to ensure hemostasis. With intermittent clamping, a condition akin to preconditioning is created. The duration of clamping should be reduced by about 50% in cirrhotic livers (View Highlight)
selective vascular occlusion includes clamping of the inflow of the resected hemiliver (View Highlight)
total clamping involves occlusion of the infrahepatic and suprahepatic IVC, with a significant blood pressure drop (40 to 50 percent reduction, leading to critical hypotension) and a substantial decrease in venous return and cardiac output (up to 50 percent) with compensatory tachycardia. The duration of clamping can be up to 100 minutes but should be limited to no more than 50 min in CLD patients (View Highlight)
Very rarely, and usually only in extreme emergencies (uncontrolled blood loss), aortic clamping should be considered (View Highlight)
In cases of extended clamping, understanding the systemic cardiovascular consequences through hemodynamic monitoring is vital, making the use of a Swan-Ganz catheter or, if available, transesophageal echocardiography (TEE), crucial (View Highlight)
In liver surgery, minimally invasive monitoring of CO, left heart function, and dynamic parameters can largely address the controversy around maintaining low CVP (< 5 mmHg) during liver dissection, a standard technique to reduce blood loss, debated if used without an appropriate rationale (View Highlight)
CVP monitoring aiming at low values (< 5 mmHg), is now questioned. CVP values can be reduced implementing different strategies (increased diuresis, restrictive fluid management, anti-Trendelenburg position, use of vasodilators, post-induction phlebotomy) but able to induce side effects (View Highlight)
Values of SVV or PPV > 13% (normal < 9%, with a grey zone between 9 and 13%) are more reliable than the absolute value of CVP in maintaining a relative hypovolemic state while keeping CO within normal limits (View Highlight)
In modern anesthesia practice during major abdominal surgery, including liver resection, the restrictive fluid therapy is championed as a mainstay of anesthetic management: At the end of surgery, the best outcomes are associated with even or only slightly positive balance (View Highlight)
attention should be paid to the onset of postoperative metabolic alkalosis, common after major surgery in general and after liver resections, and compensated for by respiratory acidosis (secondary to hypoventilation) (View Highlight)
Open resective surgery historically involves significant postoperative pain. Thoracic epidural blocks (TEB) have become popular, reducing respiratory complications and systemic sympathetic response when appropriately used (View Highlight)
widespread adoption of TEB has been limited by concerns about perioperative hemodynamic instability and risk of spinal hematoma (secondary to possible postoperative hemostatic alterations): recent ERAS guidelines no longer recommend TEB due to the evidence of effective alternatives (View Highlight)
there is growing interest in alternative techniques such as continuous local infiltration with wound catheters, “single shot” subarachnoid analgesia with local anesthetics and intrathecal opioids, and patient-controlled analgesia (View Highlight)