From the Guidelines
Furosemide (Lasix) should generally not be administered if systolic blood pressure is below 90 mmHg. This threshold is important because furosemide is a potent diuretic that can cause rapid fluid loss, potentially leading to further blood pressure reduction 1. When administering furosemide, it's essential to monitor blood pressure before and after administration, especially in patients with known hypotension or cardiovascular instability. The European Society of Cardiology guidelines recommend that diuretics should be avoided in patients with signs of hypoperfusion until adequate perfusion is attained 1.
Key Considerations
- The initial approach to congestion management involves i.v. diuretics with the addition of vasodilators for dyspnoea relief if blood pressure allows 1.
- In patients with borderline low blood pressure (90-100 mmHg systolic) but requiring furosemide for urgent volume overload, consider using a lower initial dose (such as 20 mg instead of 40 mg) and closely monitoring the hemodynamic response.
- The dose of furosemide should be limited to the smallest amount to provide adequate clinical effect and modified according to previous renal function and previous dose of diuretics 1.
- In emergency situations where both hypotension and severe pulmonary edema coexist, the risk-benefit assessment should be made by the treating physician, potentially with vasopressor support if furosemide is deemed necessary despite low blood pressure.
Monitoring and Adjustments
- Monitor blood pressure, symptoms, urine output, renal function, and electrolytes during use of i.v. diuretics 1.
- Adjust the dose and duration of diuretics according to patients’ symptoms and clinical status 1.
- Consider using a combination of loop diuretic with either thiazide-type diuretic or spironolactone in patients with diuretic resistance 1.
From the Research
Definition of Hypotension
The definition of hypotension, particularly in relation to the administration of lazix, is crucial. According to various studies, the traditional definition of hypotension as a systolic blood pressure (SBP) less than 90 mmHg may not be universally applicable.
Optimal Systolic Blood Pressure Thresholds
- A study published in 2010 2 found that the optimal definition of hypotension was an SBP of 100 mmHg for patients aged 20-49 years, 120 mmHg for patients aged 50-69 years, and 140 mmHg for patients aged 70 years and older.
- Another study from 2012 3 suggested that the optimal threshold of hypotension was an SBP of 110 mmHg for patients aged 15-49 years and 70 years and older, and 100 mmHg for patients aged 50-69 years.
- A 2007 study 4 proposed that hypotension begins at an SBP of 110 mmHg, as this is the point at which the slope of the mortality curve increases.
- A 2015 study 5 found that the best-performing SBP thresholds for predicting 7-day mortality ranged from 95 to 119 mmHg in the emergency department, 103 to 120 mmHg in the ambulance, and 101 to 115 mmHg in the mobile emergency care units.
- A 2021 study 6 concluded that an SBP of 110 mmHg should be used to define hypotension in adult patients with isolated traumatic brain injuries, as this threshold was associated with improved mortality outcomes.
Implications for Lazix Administration
Based on these studies, it appears that the lowest possible blood pressure at which lazix can be safely administered is around 100-110 mmHg, depending on the patient's age and specific medical condition. However, it is essential to consider individual patient factors and consult with a healthcare professional to determine the optimal blood pressure threshold for lazix administration.