NAVIGATING ANESTHESIA CHALLENGES IN AORTIC ANEURYSM SURGERY

Abdominal aortic aneurysm repair particularly open repair possesses significant challenges for anaesthetist due to high-risk patient with comorbidities. The main objective is to maintain stable vitals during aortic clamping and release, reducing chances of heart, kidney and lung related complications. Preoperative assessment mainly focuses on cardiac evaluation, optimisation of comorbidities. Intraoperatively, invasive monitoring is essential to manage profound physiological changes during clamping and release. Post operative management includes vigilant monitoring of complications and pain management

Case Illustration

This case involves a 74-year-old male patient with a history of incidentally detected saccular infra-renal abdominal aortic aneurysm, with comorbidities including Type II diabetes mellitus, systemic hypertension, prior transurethral resection of bladder tumour (TURBT) for papillary carcinoma (24/06/2025). The patient presented for elective open transperitoneal aneurysmorrhaphy with aorto bi-iliac bypass. The preoperative examination revealed a conscious, oriented, afebrile patient with stable vitals (pulse rate 63/min, blood pressure 130/60 mmHg, SpO2 98% on room air

INTRAOPERTIVE

Preoperative Preparation

• Adequate blood products were reserved
• Patient and attenders were counselled regarding the procedure and its related complications
• Upon received into the theatre, patient was connected to standard ASA monitors including ECG, pulse oximetry, and non-invasive blood pressure. An epidural catheter was placed prior to induction for perioperative analgesia.

Induction and Airway Management

General anesthesia was induced with intravenous propofol (2 mg/kg), fentanyl (2 mcg/kg), and cisatracurium (0.2 mg/kg). The patient was intubated and mechanically ventilated.

Invasive Monitoring and Hemodynamic Management

A central venous catheter and invasive arterial blood pressure line were inserted for real-time hemodynamic monitoring. Noradrenaline and nitro-glycerine infusions were used to manage blood pressure changes during aortic clamping and unclamping.

Intraoperative Course

Anticoagulation was achieved with intravenous heparin, titrated according to ACT. The infrarenal aortic cross-clamp was applied for 2 hours, with one limb reperfused at 2 hours and the other at 2.5 hours.

Blood Product Administration and Postoperative Care

Estimated blood loss was approximately 500 mL, and goal-directed fluid therapy maintained adequate urine output.

Intraoperatively, 1 unit of packed red blood cells and 2 units of fresh frozen plasma were transfused. Following surgery, the patient was transferred to the intensive care unit for elective postoperative ventilation and close monitoring.

Post op

Patient was subsequently extubated next day and discharged after 1 week

DISCUSSION

Aortic cross-clamping induces significant physiological changes due to two primary mechanisms: the application of the clamp, which restricts blood supply to distal organs and its release. The extent and severity of these pathophysiological changes are influenced by several factors, including the site and duration of clamp application, the patient’s physiological reserve, and whether the procedure is elective or emergent.

CARDIOVASCULAR SYSTEM

Clamp application

• Upon application, systemic vascular resistance (SVR) rises sharply, resulting in increased afterload. This leads to an elevation in arterial pressure proximal to the clamp (mean arterial pressure increases by approximately 50%) and reductions in ejection fraction (down to 40%).
• To maintain cardiac output, sympathetic stimulation occurs that enhances heart rate and contractility, as well as increased preload from central venous return. These may cause myocardial ischemia, characterized by diminished coronary perfusion pressure and thus reduced myocardial oxygen supply.
• Concurrently, myocardial oxygen demand escalates due to increased contractility. Consequently, regional myocardial wall motion abnormalities occur in 33% of cases with supra-renal clamping and over 90% with supra-coeliac clamping. Heart failure may also occur.

Measures:

Anaesthetists aim to mitigate afterload by reducing SVR through vasodilatory options such as deepening anesthesia, administering opioids, or using direct vasodilators like glyceryl trinitrate (GTN) or sodium nitroprusside.

Clamp release

• Releasing the clamp precipitates 70-80% decline in SVR and the influx of anaerobic metabolites (including H+, K+, adenosine, ADP, purines, hypoxanthine, and xanthine oxidase). This results in ischemia-reperfusion injury, metabolic lactic acidosis that directly suppresses myocardial function.

Measures:

Strategies to attenuate hemodynamic instability during clamp release include optimizing intravascular volume prior to clamp release, gradual clamp release by the surgical team, and vasoactive medications. Additionally, maintaining normal coagulation by preventing hypothermia and acidosis is essential.

RENAL SYSTEM

• Supra-renal clamping may reduce renal blood flow by up to 95%, predisposing to acute tubular necrosis. Infra-renal clamping impairs renal cortical blood flow, leading to a 67% reduction in glomerular filtration rate and a 48% decrease in renal plasma flow, effects that may persist for up to six months postoperatively.

SPINAL CORD ISCHEMIA

• Spinal cord perfusion pressure (SCPP) is defined as the difference between mean arterial pressure (anterior spinal artery pressure) and the higher of cerebrospinal fluid (CSF) or venous pressure. Cross-clamping diminishes anterior spinal artery pressure, thereby reducing SCPP and heightening ischemia risk.
• Neurological impairment arises not only from hypotension but also from hypoxia and reperfusion injury.

Prevention and Spinal Cord Protection

• Protective techniques involve surgical approaches such as sequential aortic clamping, CSF drainage to preserve SCPP, maintenance of adequate mean arterial pressure, cooling methods.

ABDOMINAL EFFECTS

• Visceral perfusion may be compromised regardless of clamp position. The descending colon is most vulnerable due to inferior mesenteric artery occlusion. Hepatic hypoperfusion can impair lactate clearance. The overall incidence of visceral injury ranges from 1-10%.

PULMONARY INJURY

• Pulmonary complications are frequent following cross-clamping. Inflammatory mediators released upon clamp removal elevate pulmonary vascular resistance, potentially causing pulmonary hypertension, increased vascular permeability, pulmonary oedema, acute lung injury, and the need for extended mechanical ventilation.

CONCLUSION

Aortic cross-clamping, a cornerstone of aortic aneurysm repair surgeries such as those for abdominal or thoracic aortic aneurysms, induces significant physiological disruptions across multiple organ systems. The procedure’s impact—ranging from hemodynamic instability and myocardial ischemia to renal impairment, spinal cord ischemia, visceral hypoperfusion, and pulmonary complications—requires careful perioperative management. Effective communication between the surgical and anesthetic teams is paramount to anticipate and address the dynamic physiological challenges of cross-clamping. By integrating these approaches, clinicians can enhance patient safety and improve outcomes in the complex and high-stakes context of aortic aneurysm repair.

REFERENCES

1. Perioperative Management of Thoracic and Thoracoabdominal Aneurysms BJA Education, Volume 19, Issue 5, May 2019, Pages 136–142. DOI: 10.1016/j.bjae.2019.01.004 https://www.jvascsurg.org/article/S0741-5214%2819%2932500-5/fulltext)
2. Spinal Cord Protection in Aortic Surgery BJA: British Journal of Anaesthesia, Volume 117, Issue suppl_2, August 2016, Pages ii26–ii36. DOI: 10.1093/bja/aew217
3. The Effect of Suprarenal Cross-Clamping on Abdominal Aortic Aneurysm Repair Breckwoldt WL, Mackey WC, Belkin M, et al. Archives of Surgery, Volume 127, Issue 5, May 1992, Pages 520–524. DOI: 10.1001/archsurg.1992.01420050040004 clamping.[](https://jamanetwork.com/journals/jamasurgery/fullarticle/595369)

Pathophysiology of Aortic Cross-Clamping and Unclamping Science Direct. Anesthesiology Clinics, Volume 26, Issue 3, September 2008, Pages 451–469. DOI: 10.1016/j.anclin.2008.07.006

Dr Nirmalraj M
3rd Year PG, DNB Resident,
Department of Anaesthesiology,
Kauvery Hospital Chennai

Dr Hemalatha
Senior Consultant,
Department of Anaesthesiology,
Kauvery Hospital Chennai

Mentor

Dr Jamila
Senior Resident,
Department of Anaesthesiology,
Kauvery Hospital Chennai