How to manage a patient with acute lower gastrointestinal bleeding, hypotension, and tachycardia, with a background of diverticulosis and significant comorbidities?

Management of Acute Lower Gastrointestinal Bleeding with Hemodynamic Instability

This patient requires immediate CT angiography (CTA) to localize the bleeding source, followed by aggressive resuscitation with restrictive transfusion thresholds, and catheter angiography with embolization within 60 minutes if CTA is positive. 1, 2, 3

Immediate Assessment and Stabilization

Calculate the shock index immediately (heart rate ÷ systolic blood pressure). This patient has a shock index of 1.12 (112 ÷ 100), indicating hemodynamic instability (shock index >1). 2, 3

Resuscitation Protocol

• Initiate aggressive fluid resuscitation with crystalloids to restore hemodynamic stability while preparing for diagnostic imaging. 2

• Transfuse packed red blood cells using restrictive thresholds: Given this patient's cardiovascular comorbidity (hypertension) and significant hemoglobin drop (10.2 g/dL from baseline 13 g/dL), use a hemoglobin trigger of 80 g/L (8 g/dL) with a target of ≥100 g/L (10 g/dL). 1, 2, 4

• Correct any coagulopathy: Although this patient's coagulation profile is normal, if INR >1.5, administer prothrombin complex concentrate and vitamin K. If platelets <50,000/µL, transfuse platelets. 1, 2, 4

Diagnostic Algorithm for Hemodynamically Unstable Patients

First-Line Investigation: CT Angiography

Perform CTA immediately as the fastest, least invasive means to localize bleeding before any therapeutic intervention. 1, 2, 3, 4 CTA has a 94% positive rate in hemodynamically unstable patients with lower GI bleeding and provides rapid anatomical localization. 3

Do NOT proceed directly to colonoscopy in this unstable patient (shock index >1). Colonoscopy is explicitly contraindicated as the initial approach when patients remain unstable after resuscitation. 3

If CTA is Positive

Proceed immediately to catheter angiography with embolization within 60 minutes in centers with 24/7 interventional radiology services to maximize success rates. 1, 2, 3 Transcatheter embolization provides time to stabilize the patient and prepare the bowel, both contributing to better surgical outcomes if surgery ultimately becomes necessary. 3

If CTA is Negative

Consider upper GI endoscopy to exclude an upper GI source, as hemodynamic instability with bright red rectal bleeding may indicate a brisk upper GI bleed. 1, 2 Up to 11% of patients presenting with apparent lower GI bleeding ultimately have an upper GI source. 1

Surgical Considerations

Surgery should only be considered after every effort at radiological and endoscopic localization has failed, except under exceptional circumstances. 1, 2, 3 This is critical because:

• Blind segmental resection and emergency subtotal colectomy are associated with rebleeding rates as high as 33% and mortality rates of 33-57%. 1, 3
• Overall operative mortality for emergency surgery for lower GI bleeding is 10%, with mortality for total abdominal colectomy ranging from 27-33%. 1, 3

Indications for emergency surgery include: 1

• Persistent hemodynamic instability despite aggressive resuscitation and transfusion of >6 units of packed red blood cells
• Life-threatening bleeding non-responsive to endoscopic or angiographic intervention
• Hemorrhagic shock unresponsive to resuscitation

Management of Diverticulosis-Related Bleeding

Given this patient's known diverticulosis, diverticular bleeding is the most likely source. 5, 6, 7 Diverticular bleeding typically presents as painless, intermittent, large-volume lower GI bleeding and is the most common cause of lower GI bleeding in the UK. 1, 5

Key management points specific to diverticular bleeding: 5

• Less than 5% of patients with diverticulosis present with diverticular bleeding
• Most cases are self-limiting, but this patient's hemodynamic instability indicates severe bleeding
• When the bleeding site is localized preoperatively, partial colectomy is sufficient; subtotal colectomy is necessary only when localization is not possible

Common Pitfalls to Avoid

Do not perform colonoscopy as the initial investigation in this unstable patient. The British Society of Gastroenterology explicitly recommends against colonoscopy when shock index >1 or patients remain unstable after resuscitation. 3

Do not proceed to emergency laparotomy without attempting localization. Mortality in lower GI bleeding is generally related to comorbidity rather than exsanguination (overall in-hospital mortality 3.4%, but 20% in patients requiring ≥4 units of red cells). 1, 2, 3 Localization allows for targeted intervention with better outcomes.

Do not use liberal transfusion thresholds in patients without active cardiovascular ischemia. Even with this patient's hypertension history, the restrictive threshold of 80 g/L trigger with 100 g/L target is appropriate unless active cardiac ischemia develops. 1, 2

Monitoring and Disposition

Admit to ICU given the presence of: 3

• Orthostatic hypotension (BP 100/60 mmHg sitting)
• Hemoglobin decrease >3 g/dL from baseline
• Persistent hemodynamic instability (tachycardia, hypotension)
• Continuous active bleeding

Monitor continuously for response to resuscitation and prepare for immediate intervention based on CTA findings. 2, 3