Approach to postoperative hypotension: Clinical sciences

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Introduction0:00–0:31

Postoperative hypotension is one of the most common complications in the immediate period after any operation and is associated with an increased risk of morbidity and mortality.
The most common causes of postoperative hypotension are general anesthesia and inadequate fluid resuscitation. Other causes include life-threatening conditions like respiratory failure, hemorrhage, and cardiovascular events.When assessing a patient with postoperative hypotension, your first step is to perform an ABCDE assessment to determine if the patient is unstable or stable.

Unstable patient0:31–1:32

Remember that all hypotensive patients are considered unstable so your priority is to stabilize their hemodynamic status as quickly as possible.
To do this, initiate acute management like stabilizing the airway, providing supplemental oxygen, establishing IV access, continuously monitoring vitals, and consider starting IV fluid resuscitation and vasopressors right away.
After that, obtain a focused history and physical exam. Be sure to get the information about the type of operation performed; when it was performed; the type of anesthesia and medications used; as well as preoperative disease and physiologic state of the patient; and allergies.
Following the ABCDE, first assess for respiratory distress. In particular, you’ll want to look for causes of respiratory distress like tension pneumothorax, pulmonary embolism, or anaphylaxis.

Respiratory distress1:32–1:58

These conditions may lead to a decrease in left ventricular filling, which can in turn reduce the cardiac output, ultimately resulting in hypotension.
Now, the patient might have a history of underlying lung disease, sustained thoracic trauma, a thoracic procedure, or prolonged ventilatory support, as well as a complication of central line placement.

Tension pneumothorax1:58–3:21

Additionally, the physical exam might reveal absent lung sounds, jugular venous distension with or without tracheal deviation in addition to tachypnea, hypoxia, tachycardia, and altered mental status.
With these findings, you can make a diagnosis of tension pneumothorax. These patients should immediately be treated with needle decompression and chest tube placement.
Here’s a clinical pearl! Physical exam findings are enough to make your diagnosis of tension pneumothorax, as it can be quickly fatal, so you should never delay the treatment to obtain imaging like ultrasound or chest x-ray.
However, if you were to perform them, ultrasound would show absent lung sliding against the rib cage, while a chest x-ray would show a visible visceral pleural edge with absent distal lung markings on the affected side, as well as tracheal deviation and mediastinal shift toward the opposite side.Moving onto the next cause of respiratory distress.

Pulmonary embolism3:21–5:12

History might reveal a hypercoagulable state, such as cancer, previous or current deep vein thrombosis, immobility, trauma like long bone fractures, or any recent major surgery, such as an orthopedic procedure, emergent obstetric operation, or even plastic surgery like liposuction.
On exam, in addition to hypotension, you may find tachycardia, hypoxia, dyspnea, cough, and hemoptysis. If this is the case, consider pulmonary embolism and order an ABG, ECG, and echocardiogram.
ABG will show low PaO2 despite high FiO2, with an elevated alveolar-arterial or A-a gradient indicating ventilation-perfusion or V/Q mismatch, as well as elevated CO2; while ECG can show sinus tachycardia or the S1Q3T3 pattern.
On echocardiogram, you can expect to see right heart strain and distended inferior vena cava. If there’s a large central embolus, it’s called a saddle PE.
Finally, once you stabilize the patient, you need to obtain a CT pulmonary angiography, or CTA, which will show a filling defect in the pulmonary vasculature.
This confirms the diagnosis of pulmonary embolism.Here’s a clinical pearl! If your patient remains unstable, you should just make a presumptive PE diagnosis without confirming with CTA, and start treatment right away.The last of the life-threatening respiratory causes to consider is anaphylaxis.
Usually, patients will have a personal or family history of allergies to drugs, latex, or intravenous contrast. On a physical exam, in addition to hypotension, you might see flushing, lip or tongue swelling, skin rash or hives as well as more serious signs and symptoms like respiratory distress, tachycardia, and altered mental status.

Anaphylaxis5:12–6:41

These findings should get you to consider anaphylaxis. Keep in mind here that anaphylaxis is a clinical diagnosis, but there should be special considerations for obtaining ABG and echocardiogram in a patient with postoperative hypotension and respiratory distress.
ABG is usually normal, while echocardiogram shows a hypercontractile left ventricle and an underfilled right ventricle reflecting systemic vascular vasodilation of anaphylactic shock.
Before we move on, here’s a clinical pearl! There’s many other causes of postoperative distress that, when severe enough, can ultimately lead to hypotension as well!
Two of the most common ones include bronchospasm secondary to general anesthesia, aspiration during intubation or extubation.Alright, let’s move on to hemorrhagic causes of hypotension, which is one of the most serious postoperative complications.
Patients who underwent high risk operations for trauma or cardiovascular disease, emergent surgery while on blood thinners or for obstetric and gynecologic emergencies, surgeries requiring intraoperative transfusions, or patients with liver disease.

Major bleeding/Acute blood loss6:41–8:47

On physical exam, in addition to hypotension, your patient may have tachycardia and tachypnea, as well as altered mental status.
You might see external bleeding around the incision, increasing swelling of the surgical site, and abdominal distension if abdominopelvic surgery was performed.
If you suspect acute blood loss, obtain labs like CBC, paying special attention to platelets; as well as PT/INR, and fibrinogen; blood type and crossmatch in case you need to transfuse; lactate to assess organ perfusion; and sometimes you may check ABG; as well as imaging like ultrasound or chest x-ray.
In labs, CBC may show low hemoglobin and hematocrit, and low platelets; as well as elevated PT/INR; low fibrinogen; and elevated lactate; while ABG may show metabolic acidosis.
When it comes to imaging, ultrasound like E-FAST may help detect the presence of blood as free fluid in the abdomen in keeping with hemoperitoneum, or an enlarging hematoma within the abdominal wall or the internal abdominal musculature like the psoas muscle; while chest x-ray may help find the source of bleeding, such as a hemothorax.
With these findings, the diagnosis of acute blood loss is confirmed. Patients with acute postoperative bleeding leading to hypotension will likely need to go back to the operating room to obtain adequate hemorrhage control.
Next, let’s talk about the life-threatening cardiogenic causes of postoperative hypotension. Surgical procedures can induce physiological stress on the body, so, the risk of unexpected cardiovascular events is generally high.

Cardiogenic causes8:47–10:34

Patients with a history of smoking; diabetes; cardiac diseases like myocardial infarction or heart failure; prior CV procedures like coronary stent placement; or high preoperative ASA classification.
You should also have high clinical suspicion in any patient presenting with chest trauma, as well as those who underwent high-risk procedures like oncologic operations and cardiovascular surgery.
Since we’re considering cardiogenic causes of hypotension, order labs including CBC, CMP, and cardiac enzymes; ECG; and perform a quick bedside echocardiogram.
While CBC may be unremarkable; CMP might show electrolyte abnormalities, especially with potassium and calcium; and cardiac enzymes would be elevated too.
ECG may reveal tachyarrhythmias, ST changes, or new left bundle branch block, but be sure to compare to the patient’s baseline ECG to see if the arrhythmia is new.
Lastly, on echocardiogram, you might see ventricular dysfunction, decreased ejection fraction, dilated heart, distended IVC, pericardial effusion or even valvular dysfunction, which will confirm your diagnosis.
Once you have ruled out the life threatening causes of postoperative hypotension, your next step is to assess for other urgent conditions that may warrant timely interventions.
The general workup includes ABG, CBC, CMP, lactate, and bedside echocardiogram. An important cause of postoperative hypotension is non-hemorrhagic fluid loss.

Other urgent conditions10:34–10:59

You should be concerned for this in a patient with severe vomiting or gastrointestinal fluid losses like increased ostomy output, trauma, or burns, or require diuretic use, you should be concerned for non-hemorrhagic fluid loss causing hypotension.

Non-hemorrhagic fluid loss10:59–12:33

Nausea and vomiting are the most common postoperative complications, and if severe they can cause hemodynamic instability.
On exam, you can expect to find sinus tachycardia; as well as signs of dehydration like dry mucous membranes or decreased urine output; and peripheral or generalized edema in cases of third spacing, and possibly soft tissue edema if the patient has severe burns or crush injury.
Labs can show metabolic alkalosis in GI fluid losses or acidosis in severe burns on ABG; hemoconcentration with elevated hemoglobin and hematocrit; high BUN/creatinine ratio and electrolyte abnormalities like hypernatremia with severe dehydration; as well as low albumin in the setting of third spacing; and elevated lactate levels.
Bedside echocardiogram will likely reveal an underfilled heart and collapsed IVC. This confirms your diagnosis of non-hemorrhagic hypovolemic hypotension.
Another potential cause of hypotension is neuraxial analgesia, such as epidural. In fact, patients often keep neuraxial analgesia postoperatively for ongoing pain, and hypotension is the main complication.
This occurs due to the associated sympathetic blockade leading to arterial and venous vasodilation. The most common physical exam findings include hypotension with bradycardia, while some patients may develop reflex tachycardia.

Neuraxial analgesia12:33–13:33

Laboratory work in these cases will be grossly unremarkable, and echocardiogram may show hypo- or hypercontractility of the heart.
If a patient with neuraxial analgesia develops these findings, consider hypotension as an adverse effect, and quickly stop the infusion.
Then, give IV fluids and, if needed, vasopressors. If hypotension resolves, you can confirm it was an adverse effect of the neuraxial analgesia, and you can resume it at a lower infusion rate.Finally, the last diagnosis to consider is the adrenal crisis.
Patients with a history of adrenal insufficiency or chronic steroid use are at high risk of adrenal crisis even if they were given steroids preoperatively.
Additionally, patients might get an adrenal crisis due to adrenal ischemia or necrosis, which happens with massive blood loss or major trauma; or the disruption of the pituitary-adrenal axis, which can result from sepsis.

Adrenal crisis13:33–15:25

In clinical practice, you should be suspicious of adrenal crisis in any patient with hypotension that is refractory to vasopressors as the lack of cortisol hinders the vasoconstrictive effects of vasopressors.
A physical exam is usually non-specific, so you might find altered mental status and abdominal tenderness. In labs, you will likely see electrolyte abnormalities like hyperkalemia, hyponatremia, and increased urea, but ABG, CBC, and lactate will be normal.
If you are concerned about an adrenal crisis, order a serum cortisol level. A low serum cortisol level will confirm your diagnosis.
However, in emergent settings, do not delay the administration of steroids to obtain diagnostic labs, because an untreated adrenal crisis has a high mortality rate.
Here’s a clinical pearl! In the postoperative setting, the body is in a stress state, so normally serum cortisol should be high.
If instead the serum cortisol is low or even normal in this setting and the patient has refractory hypotension, your patient needs stress dose steroids, meaning an increased dose of exogenous steroids to treat relative adrenal insufficiency.Alright, as a quick recap… Postoperative hypotension is one of the most common complications after surgery and can be caused by both life-threatening and urgent conditions.
You should first evaluate the patient’s respiratory status and assess for tension pneumothorax, pulmonary embolism or anaphylaxis.

Review15:25–16:20

Then, you need to assess for any major bleeding, especially around the incision and the surgical site that can cause hemorrhagic shock.
Next, you should consider cardiac causes of hypotension such as arrhythmias, myocardial infarction, or pericardial effusions.
Once you have ruled out the life-threatening causes, assess for other urgent conditions that may warrant timely interventions, including the patient’s volume status for excessive non-hemorrhagic fluid losses, adverse effect of neuraxial analgesia, and adrenal crisis.
of hypotension such as arrhythmias myocardial infarction or pericardial effusions Once we have ruled out the life-threatening causes assess for other urgent conditions that may warrant timely interventions including the patient's volume status for excessive nonhemorrhagic fluid losses adverse effect of neuraxis analgesia and adrenal crisis