UMEM Educational Pearls - Critical Care

 

Spontaneous Pneumomediastinum

• Spontaneous pneumomediastinum is largely a benign disease typically seen in young males ages 18-21 years
• It is typically caused by activities that increase alveolar pressure such as coughing, sneezing, vomiting, inhalational drug use, and Valsalva maneuver
• The most common symptoms include chest pain and dyspnea; chest pain is usually centrally located, may radiate to the neck, and may be worse with inspiration
• CT scan is the "gold standard"; CXR is a good place to start but it is normal in up to 30% of cases
• The vast majority of patients do not require admission or supplemental O₂
• Advise patients to avoid strenuous activity until after symptom resolution (typically takes about 2 weeks)
• Any patient with a fever, elevated WBC count, hemodynamic instability, severe dysphagia or odynophagia should first be evaluated for infectious mediastinitis or esophageal perforation (spont. pneumomediastinum is a diagnosis of exclusion in these patients)

Invasive Arterial Pressure Monitoring - Complications

In critically ill patients with hemodynamic instability we often place arterial catheters to continuously monitor mean arterial pressure.  Since we frequently use the radial artery for cannulation, it is important to know the complications associated with these catheters.  Scheer et al performed, perhaps, the largest review of complications of peripheral arterial catheters.  The results:

• Radial arterial catheters
  • 19,617 cannulations reviewed
  • temporary occlusions - 19.7%
  • hematoma - 14.4%
  • serious ischemic damage - 0.09%
  • pseudoaneurysm - 0.09%
  • sepsis - 0.13%

Pearl: Although permanent ischemic damage is rare, when placing a radial artery catheter use the non-dominant hand.

Scheer BV, Perel A, Pfeiffer UJ. Clinical review: Complications and risk factors of peripheral arterial catheters used for haemodynamic monitoring in anaesthesia and intensive care medicine. Crit Care 2002;6:198-204.

Pitfalls in pulse oximetry in the critically ill

• Pulse oximeters are calibrated by manufacturers using data collected from healthy volunteers
• In general, pulse oximeters are accurate  within +/- 2% for sats > 70%
• In the critically ill, however, the accuracy of pulse oximetry diminishes when sats drop below 90%
• Also, there may be a significant lag time between a hypoxic event and the actual display of the event - most commonly seen in low flow states, hypotension, mild hypothermia, and when using vasoactive medications
• Prolonged lag times are more common with finger probes
• Pitfall - pulse oximetry does not provide any assessment regarding ventilation (P_aCO₂) or acid-base status (pH) - it is simply an estimate of arterial oxgyen saturation
• Pearl: anemia does not affect the accuracy of pulse oximetry

Mean Arterial Pressure

• Arterial pressure is the input pressure for organ perfusion
• Mean arterial pressure (MAP) is the best physiologic estimate of perfusion pressure
• MAP is less subject to measurement variability than SBP and DBP
• MAP remains relatively constant when measured at different sites throughout the arterial circuit
• MAP of 60 mmHg is considered the autoregulatory threshold below which perfusion becomes compromised
• Goal: maintain MAP > 65 mmHg
• There is no proven value to achieving a MAP higher that 65 mmHg.  In fact, there is some literature to support that if you try and drive the MAP higher, patients do worse

Pulmonary Hypertension Pearls

We are beginning to see more and more patients with pulmonary hypertension (PAH),  many of whom are on continuous IV infusions of new medications.  With that in mind, here are a few pearls:

• The most common causes of rapid deterioration in patients with PAH are: catheter occlusion/pump malfunction, pneumonia, indwelling catheter infection, RV ischemia, PE, and GI bleeding
• Hypotension is usually due to worsening RV failure and less likely to hypovolemia
• If a catheter occlusion or pump failure is found, the drug should be restarted as soon as possible through an alternative access (including peripheral)
• Calcium channel blockers, a prior treatment for PAH, are no longer indicated and should not be given

Adrenal Insufficiency in the Critically Ill

• Adrenal insufficiency (AI) is estimated to occur in up to 30% of critically ill patients
• The most common causes of AI in the critically ill are SIRS and sepsis
• In most cases of critically ill patients, AI is functional (i.e relative) - the adrenal response is insufficient to respond to the degree of stress
• Diagnostic clues include hyponatremia, hyperkalemia, hypoglycemia (rare), and hemodynamic instability despite IVFs and vasopressors
• Although still controversial, most feel that AI is present in critically ill patients with either a basal cortisol < 15 mcg/dl, an increase in < 9 mcg/dl after ACTH stimulation, or a random cortisol < 25 mcg/dl
• IV hydrocortisone, methylprednisolone, and dexamethasone are the 3 glucocorticoids most commonly administered
• Hydrocortisone is usually the preferred agent because it is the synthetic equivalent of cortisol (and has both glucocorticoid and mineralocorticoid activity)

Critical Care Monitoring - End-Tidal CO₂

• End-tidal CO₂ (ETCO₂) monitoring is used to verify ETT placement, monitor procedural sedation, traumatic brain injury, and to estimate prognosis during cardiopulmonary resuscitation
• ETCO₂ concentration typically underestimates P_aCO₂ by 4-5 mmHg in healthy non-intubated patients
• This relationship is less reliable in critically ill patients secondary to shunt, altered alveolar dead space, and inadequate ventilation
• While a low ETCO₂ value is less useful in the critically ill, a high value almost always correlates with an equal or higher P_aCO₂ value
• This can be useful when monitoring conditions such as status asthmaticus, CHF, or increased ICPs in which a high ETCO₂ may signal the need for additional aggressive treatment

Unilateral Pulmonary Edema

• unilateral pulmonary edema is a well recognized and well documented entity
• although there are several causes, the most likely scenarios for EPs are severe mitral valve insufficiency, aortic dissection (with compression of the pulmonary artery), airway obstruction, and heroin use
• even though radiology will read the xray as likely pneumonia, if the story/exam fit with edema then treat as such

Massive hemoptysis

• Massive hemoptysis is defined by most as the expectoration of > 600 ml in 24 hrs
• Chronic lung inflammatory disease and bronchogenic CA are the most common causes in the US
• TB remains the most common cause worldwide
• The bronchial artery causes approximately 90% of cases
• Get a STAT portable and place the patient in the lateral decubitus position toward the affected side (this is theorectical and has not been proven)
• Options for bleeding control can include endobronchial tamponade methods(pulmonary), bronchial artery embolization (interventional radiology), and emergent surgical resection (surgery)
• Bronchial artery embolization is now the most successful non-surgical treatment of massive hemoptysis

Acute Liver Failure

• Acute liver failure (ALF) is defined as the onset of encephalopathy and coagulopathy within 26 weeks of jaundice in a patient without prior history of liver disease
• ALF has an extremely high mortality
• The most common cause of ALF include Tylenol, HSV, autoimmune hepatitis, HBV, and acute fatty liver of pregnancy/HELLP
• Complications EPs are likely to see/manage include hepatic encephalopathy, infection, circulatory dysfunction, bleeding, and seizures
• Fungal infections may be present in one-third of patients with ALF (Candida)
• Non-convulsive seizure activity occurs in a high proportion of patients with ALF and encephalopathy - consider EEG for severly encephalopathic patients and those with a sudden deterioration in neuro status

Stravitz RT, et al. Intensive care of patients with acute liver failure. Crit Care Med 2007;35:2498-2508.

A few days ago Dr. Jump and I had a case of an acute variceal hemorrhage.  Dr. Bond already sent out a great pearl earlier in the year highlighting the importance of octreotide in acute variceal bleeding.  In fact, octreotide alone can result in cessation of hemorrhage in up to 80% of patients.  To add onto Dr. Bond's pearl:

• Don't forget about antibiotics in acute variceal hemorrhage
• These patients have a relatively high incidence of bacteremia, which leads to worse outcomes
• Antibiotics have been shown to decrease infection rates and are associated with decreased rebleeding and the need for transfusions
• A 3rd generation cephalosporin is currently the recommended antibiotic of choice

• Acute chest syndrome (ACS) is the leading cause of death in sickle cell patients
• ACS is defined by the presence of a new infiltrate and one of the following: chest pain, wheezing, fever, tachypnea, or cough
• Early and aggressive therapy is needed to minimize mortality
• Up to 50% of patients develop respiratory failure
• Treatment
  • Broad spectrum antibiotics - including a macrolide
  • Pain control to reduce hypoventilation
  • Early use of blood transfusion to improve O2 carrying capacity
  • Incentive spirometry
  • Bronchodilators if wheezing present
  • Hematology consult

 

• It is traditionally taught that in hypotensive patients the presence of a carotid pulse corresponds to a SBP of 60-70 mmHg, a femoral pulse with a SBP of 70-80 mmHg, and a radial pulse with an SBP of at least 80 mmHg
• These physical exam estimates of BP have been shown to poorly correlate with the patient's actual BP
• Similarly, non-invasive measurements of BP (automated cuff) in patients with hypotension may either overestimate or underestimate SBP by as much as 20 mmHg
• Since physical exam estimates and non-invasive measurements are inaccurate in low-flow states, utilize invasive arterial monitoring
• Radial and femoral artery sites have been found to produce results that are clinically interchangeable

Critical Care Pearls for Traumatic Brain Injury

• Avoid hypotension and hypoxia - SBP < 90 and/or PaO2 < 60 are associated with significant increases in morbidity and mortality
• Hypertonic saline remains controversial - a recent large, controlled trial did not show any early or long-term benefit
• ICP monitoring routinely recommended in patients with GCS < 8 - they have a 60% chance of increased ICP
• Maintain ICP < 20 mmHg and CPP > 60
• Supportive care
  • Elevate the head of bed > 30 degrees, if possible
  • Control fever
  • Provide analgesia and sedation
• Ventilator management - keep PaCO2 between 30-35 mmHg
• Surgery - last resort to controlling increased ICP
  • Decompressive craniotomy
  • Decompressive laparotomy

• Binding of vasopressor agents to their receptors is influenced by pH (and temperature and concentration)
• Acidic conditions have been shown to alter receptor numbers on cell surfaces as well as alter binding affinity
• Overall, pH values > 7.15 do not have an appreciable clinical effects on vasopressors
• At pH values < 7.1 reductions in effectiveness become apparent
• Routine administration of bicarbonate remains controversial
• Aggressively search for and treat the underlying cause of the acidosis

 

Hyperammonemia in the Critically Ill

• Patients with acute hyperammonemia have significant morbidity and mortality 
• Fulminant hepatic failure is the most common cause of acute hyperammonemia in adult ICUs
• Other causes include TPN, GI hemorrhage, steroid use, trauma, multiple myeloma, infection with urease-splitting organisms, and drugs (salicylates, valproate) 
• Cerebral edema, intracranial hypertension, seizures, and herniation are the most significant effects
• Initial management should focus on treating intracranial hypertension - mannitol, hypothermia, N-acetylcysteine have been used
• Lactulose has not been shown to reduce mortality in acute hyperammonemia but is unlikely to be harmful

Clay AS, Hainline BE. Hyperammonemia in the ICU. Chest 2007;132:1368-1378.

[RESENT - STILL FIXING CODE - THESE TEST EMAILS SHOULD CEASE SHORTLY... SORRY FOR THE INCONVENIENCE]

• Abdominal compartment syndrome (ACS) is increasingly identified in the critically ill medical patient population
• ACS is defined as a sustained intra-abdominal pressure > 20 mmHg associated with new organ dysfunction
• Primary organs adversely affected by ACS include cardiac, pulmonary, GI, and renal
• To date, associated mortality rates have ranged from 27% to 50%
• Risk factors for ACS include:
  • massive fluid resuscitation ( >10 L crystalloid in 24 hours)
  • massive transfusion ( > 10 U PRBCs in 24 hours)
  • severe sepsis or septic shock from any cause
  • mechanical ventilation
  • PEEP > 10 cm H20
• Intravesicular (bladder) pressures are currently the standard monitoring modality
• Decompressive laparotomy is the current standard for management of ACS

DIC is the simultaneous occurrence of widespread (micro) vascular thrombosis, leading to compromised blood supply to vital organs Although major bleeding can be seen in some, the more common complication of DIC is organ failure DIC is not a disease itself but secondary to an underlying disorder Sepsis, solid and hematologic malignancies, severe trauma, and obstetrical emergencies (amniotic fluid embolism, abruption) are the most common disorders associated with DIC A prospectively validated scoring system (Toh CH, et al. J Thromb Haemost 2007;5:604-6.) is used for diagnosis and is comprised of platelet count, fibrin split products, PT, and fibrinogen level The key to treating DIC is vigorous treatment of the underlying disorder Platelet transfusion is generally only given for patients with major bleeding (i.e. intracranial) with platelets counts < 50 k

-Reexpansion pulmonary edema represents a potentially life-threatening complication of tube thoracostomy (mortality rate as high as 20 percent) -It usually occurs after rapid reexpansion of a collapsed lung in patients with a pneumothorax -It may also follow evacuation of large volumes of pleural fluid (>1.0 to 1.5 liters) or after removal of an obstructing tumor -The incidence of edema appears to be related to the rapidity of lung reexpansion and to the severity and duration of lung collapse -The clinical manifestations vary from isolated radiographic changes to complete cardiopulmonary collapse -Treatment is supportive, mainly consisting of supplemental oxygen and, if necessary, mechanical ventilation

-Non-invasive ventilation (NIV) is a form of ventilatory support that avoids intubation. -NIV refers to the provision of inspiratory pressure support + PEEP via a nasal or face mask (BiPAP, CPAP). -Strong evidence from randomized trials supports NIV to avoid intubation in patients with acute respiratory failure secondary to COPD exacerbation, acute cardiogenic pulmonary edema, and in immunocompromised patients (AIDS, transplant). -NIV can be considered in asthma exacerbations, pneumonia, and ARDS however the supporting evidence for these conditions is fairly weak. -Contraindications for NIV include respiratory arrest, hemodynamically unstable, unable to protect the airway, excessive secretions, uncooperative/agitated, and recent UGI or airway surgery. -You should expect to see clinical improvement within 1 to 2 hours.