Critical Care

1. Critical Care

2. Overview • Damage Control • Resuscitation from Shock • Traumatic Brain Injury • Pulmonary System and Ventilators • Cardiovascular System • Renal System and Electrolytes • Hematologic System • Gastrointestinal System and Nutrition • Immune System and Infections • Endocrine System • Musculoskeletal System • Preparation for Evacuation

3. Damage Control • Damage Control is the initial control of hemorrhage and contamination followed by intraperitoneal packing and rapid closure. • Definitive re-exploration is then done only after resuscitation to normal physiology in the ICU • May include • Rewarming • Large volume resuscitation • Blood products • Vasoactive drugs • Mechanical ventilation

4. Resuscitation from Shock • Shock: acute state of cardiovascular insufficiency leading to hypoperfusion • Hemorrhagic shock is the most common cause of shock in the trauma patient • Hypoperfusion implies inadequate tissue delivery to the tissues. Oxygen delivery depends on (and resuscitation attempts should address): • Cardiac function • Arterial hemoglobin content • Arterial oxygen saturation

5. Resuscitation from Shock • Resuscitation Goals: • Mean arterial pressure >60mmHg • Urine output >0.5cc/kg/hr • O2 saturation >92% • Achieve these goals with crystalloid (preferred over colloid) at a rate of 500-1000cc every 15-20 minutes as needed • After 3L crystalloid, blood products should be given • Vasoactive agents should be considered only after fluid resuscitation and confirmation of adequate intravascular volume • Prefer dopamine, phenylephrine, norepinephrine • Dobutamine should be used only for cardiac dysfunction

6. Traumatic Brain Injury • Hypoxemia or hypotension can lead to death or poor neurologic damage in the traumatic brain injury patient • Maintain O2 sat >92%, PaO2 > 100, intubate if GCS <8 • Maintain SBP > 100 mmHg, MAP >80 • Need to maintain cerebral perfusion pressure (CPP) between 70-90mmHg • Need to maintain intracranial pressure (ICP) between 5-15mmHg • CPP = MAP - ICP

7. Traumatic Brain Injury • Hypoxemia or hypotension can lead to death or poor neurologic damage in the traumatic brain injury patient • Maintain O2 sat >92%, PaO2 > 100, intubate if GCS <8 • Maintain SBP > 100 mmHg, MAP >80 • Need to maintain cerebral perfusion pressure (CPP) between 70-90mmHg • CPP = MAP - ICP • Need to avoid intracranial hypertension. Maintain intracranial pressure (ICP) between 5-15mmHg

8. Traumatic Brain Injury • Measures to avoid intracranial hypertension • Elevate head of bed to 30◦ • Check serum sodium twice per day and maintain between 145-150 mEq/dL • IV mannitol 0.25-1.0 g/kg every 6-8 hours to keep serum osmolarity optimal (but not in anuric patients) • Control PaCO2 (avoid hypercarbia by therapeutic hyperventilation to keep PaCO2 30-35mmHg) • Avoid hyperthermia • Intraventricular catheter to remove cerebrospinal fluid • May consider barbiturates in extreme cases (benefit unproven) • Craniotomy as a last resort

9. Traumatic Brain I jury • General Considerations • Prophylaxis (H2 blocker, heparin) to prevent stress ulcers and venous thrombosis • Oral care to prevent aspiration • Blood products as needed to correct elevated prothrombin time • Aggressively treat pain, agitation, fever, and shivering to avoid increased cerebral metabolism and oxygen consumption • Hyperglycemia has an adverse effect. Maintain serum glucose betwee 100-150 mg/dL • Seizure prophylaxis with phenytoin or phosphenytoin should be given to patients with penetrating head injuries

10. Pulmonary System and Ventilators • Indications for intubation • Airway obstruction due to trauma, edema, excess secretions • Apnea • Increased work of breathing • Glasgow coma scale <8 • Hypoxia despite supplemental oxygen: SaO2< 90%, PaO2 < 60mmHg • Hypercarbia: PaCO2 >60mmHg • Shock

11. Pulmonary System and Ventilators • Ventilator • Most patients well ventilated by SIMV mode (synchronized intermittent mandatory ventilation) • Oxygenation • Set FiO2 to 1.0 initially and wean down to 0.4 as able • Set PEEP to 5 cm H2O for most patients or can increase if needed (max 15 cm H2O) • Ventilation (controls PaCO2) • Set tidal volume between 6-10 mL/kg (increase if need to lower PaCO2, decrease if need to raise PaCO2) • Set rate between 10-14 breaths (increase if need to lower PaCO2, decrease if need to raise PaCO2)

12. Pulmonary System and Ventilators • ARDS (adult respiratory distress syndrome) defined by: • PaO2/FiO2 ratio <200 • Decline in pulmonary compliance (“stiff lungs”) • Bilateral alveolar infiltrates on chest X-ray withouth clinical evidence of hypervolemia • Ventilation priorities in ARDS • Maintain sedation to prevent agitation and patient/ventilator asynchrony • Keep SaO2 > 90% by increasing FiO2 or PEEP (max 15-18 cm H2O) • Avoid prolonged FiO2 > 60% (oxygen toxicity) • Avoid respiratory acidosis (keep pH > 7.25) • Keep peak inspiratory pressure < 40 cm H2O (decrease tidal volume to 6-8 cc/kg)

13. Cardiovascular System • Causes of cardiovascular instability (the H’s and T’s) • H’s: • Hypoxia • Hemorrhage • Hypovolemia • Hyper- or Hypo- kalemia • H+ (acidosis) • T’s • Tension pneumothorax • Tachyarrhythmia • Thromboembolism • Tamponade • Toxins

14. Cardiovascular System • Four measures of hemodynamic performance • Preload: Best measured by pulmonary capillary wedge pressure (PCWP) but can be estimated by central venous pressure (CVP) • Afterload: Systemic Vascular Resitance (SVR) = [MAP – CVP]/CO*80 • Heart rate: Stroke Volume (SV = CO/HR) • Contractility

15. Cardiovascular System • Myocardial Infarction: uncommon on the battlefield • Suspect if soldier complains of anginal chest pain • Diagnose by ST elevation or depression on EKG, elevation in cardiac enzymes (troponin, CK-MB) • Treatment: • Morphine • Oxygen • Nitroglycerin • Aspirin • B-blocker • Transfer for definitive treatment (revascularization by thrombolytic or catheterization)

16. Renal System and Electrolytes • Manifestations of renal injury/failure: low urine output, electrolyte abnormalities, elevations in BUN or creatinine • Acute renal failure (ARF) defined as oliguria ( < 0.5 cc/kg/hr) and rise in BUN and creatinine • Common causes of ARF: • Hypovolemia • Acute tubular necrosis (ATN) • Crush injury resulting in rhabdomyolysis • Renal or ureteral trauma

17. Renal System and Electrolytes • Treatment algorithm for oliguria or anuria in hemodynamically stable patient • Irrigate or replace Foley catheter • If no signs of fluid overload, give 1-2L saline bolus • Review medication list and discontinue any potential nephrotoxins • Check fractional excretion of sodium (FeNa) • FeNa =(urine sodium * plasma creatinine)/(plasma sodium * urine creatinine) • FeNa < 1.0 indicates hypovolemia, > 2 indicates renal or postrenal insult (ATN, obstructive uropathy, etc) • Consider renal U/S • If ineffective, consider dialysis.

18. Renal System and Electrolytes • Indications for dialysis (Nemonic = AEIOU) • A: acidosis • E: electrolytes • I: ingestions • O: overload (Hypervolemia) • U: uremia

19. Renal System and Electrolytes • Hyperkalemia • Give calcium carbonate to stabilize the cardiac membrane • Agents that lower serum potassium • Sodium bicarbonate • Dextrose • Albuterol • Sodium polystyrene sulfonate • Hypokalemia • Check for hypomagnesemia and correct if present • Give potassium chloride

20. Renal System and Electrolytes • Hypernatremia: Need to replace free water deficit • Free water deficit = 0.6 * weight in kg * [(measured sodium/normal sodium of 140) – 1] • Replace half of the deficit in the first 24 hours, the other half over the next 1-2 days • Hyponatremia: caused by excess of free water or SIADH (syndrome of inappropriate anti-diuretic hormone) • Treatment with either free water restriction if suspect SIADH, otherwise treat by administration of saline • Do not correct faster than 15mEq/L in 24 hours

21. Renal System and Electrolytes • Hypophosphatemia: replete with sodium phosphate or potassium phosphate • Hyperphosphatemia: Usually associated with acute renal failure. Treat with phosphate binders such as sucralfate • Hypomagnesemia: Give magnesium sulfate to achieve serum level of 2.0 mEq/dL

22. Renal System and Electrolytes • Metabolic acidosis: Usually due to lactic acidosis (hypovolemia) or ketoacidosis (diabetic). Do not give sodium bicarbonate for these conditions, treat the underlying cause. • Metabolic alkalosis: Caused by gastric losses (vomiting or NG suction) or excessive diuresis with furosemide. Usually treated with crystalloid.

23. Hematologic System • Coagulopathy • Causes: dilutional, heparin induced thrombocytopenia, disseminated intravascular coagulation, hypothermia, liver failure, thrombocytopenia • Treatment: blood products • Deep venous thrombosis and pulmonary embolism: Prophylaxis important in trauma patients (subcutaneous heparin and/or sequential compression devices)

24. Gastrointestinal System and Nutrition • Stress gastritis: give prophylaxis with H2 blocker or proton pump inhibitor for the following conditions • Burns • Mechanical ventilation • Head injury • Sepsis • Systemic anticoagulation • Acalculouscholecystitis • Suspect if right upper quadrant pain, fever, leukocytosis, liver function test abnormalities, and ultrasound with thickened gallbladder wall and/or pericholecystic fluid • Treatment = IV antibiotics and percutaneous drainage or surgery • Hepatic failure • Suspect if hyperbilirubinemia, hypoalbuminemia, increased prothrombin time, hypoglycemia, obtundation (hepatic encephalopathy) • Give fresh frozen plasma to correct coagulopathy

25. Gastrointestinal System and Nutrition • Early nutritional support important due to catabolism and protein wasting associated with trauma • Enteral feeding superior to parenteral • Caloric requirements = 25-30 kcal/kg/day • Protein requirement 1.0-1.5 g/kg/day • 30-40% of daily caloric intake should come from fat • Problems associated with enteral feedings include aspiration and diarrhea. Prevent by: • Increasing head of bed • Feed into jejunum or duodenum instead of stomach • Check residuals every 4 hours and stop feedings if >200cc • Add fiber and/or give anti-diarrheal medications such as loperamide

26. Immune System and Infections • Differential diagnosis of ICU infection: • Pneumonia • Central venous catheter infection • UTI • Wound or soft tissue infection • Intra-abdominal abscess • Systemic fungal infection • Sinusitis • Acalculouscholecystitis • Pancreatitis • Prophylactic antibiotics: • Should be given for 24-48 hours after penetrating battlefield injury • Should be discontinued after this unless documented infection present

27. Endocrine System • Hyperglycemia: • Must control to prevent hypovolemia due to osmotic diuresis, increased risk of infection, etc. • This is best done with IV infusion of insulin as subcutaneous injections are less reliable in ICU patients • Do not correct faster than 100 mg/dL/hr to avoid to avoid hypokalemia (insulin causes potassium to shift intracellularly). Check K+ frequently and replete as needed

28. Musculoskeletal System • In patients with musculoskeletal injuries, monitor for the following: • Rhabdomyolysis • Compartment syndrome • Vascular ischemia • Regular neurovascular checks essential. Check for: • Pulse, sensation, motor function, warmth, skin color

29. Preparation for Evacuation • Stabilize patient before transport • Secure airway • Ensure blood pressure has been stable for 8 hours • Complete primary and secondary phases of shock resuscitation • Stop bleeding • Ensure definitive surgery not required for next 24 hours