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ANESTHESIA BOARD REVIEW 2023
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indications for OLV - INDICATIONS FOR ONE LUNG VENTILATION Absolute
- Protective Isolation a. Massive Hemorrhage b. Infection
- Control of Ventilation Distribution a. Bronchopleural or bronchopleural cutaneous fistula b. Giant cyst or bullae (risk of rupture with PPV) c. Major bronchial disruption or trauma
- Unilateral Lung Lavage
- VATS Relative (Strong) - Surgical Exposure
- Thoracic aortic aneurysm
- Pneumonectomy
- Upper lobectomy Relative (Weak) - Surgical Exposure
- Esophageal surgery
- Middle and lower lobectomy
- Thoracoscopy under general anesthesia fasting guidelines children - endocrine- diabetes - ...Complications of diabetes mellitus include coronary artery disease, cerebrovascular and peripheral vascular disease, autonomic and sensory neuropathies [cardiovascular and GI effects], and joint stiffness, all of which can affect the anesthetic. TMJ and cervical joint stiffness (due to glycosylation of tissue proteins) should be assessed, as 30% of diabetics have difficult intubations endocrine- diabetes - The most feared complication of diabetes is diabetic ketoacidosis (DKA), which is most commonly precipitated by an infection. DKA should be treated with fluid resuscitation, IV insulin (0.2 U/kg initially, 0.1 U/kg/hr after, goal is to decrease by 75 - 100 mg/dL or 10% per hour), and K+ supplementation (some, but not all, authors recommend bicarbonate if pH is 7.2) Autonomic neuropathy develops in ~ 1/3 of diabetics (50% of those with coexisting hypertension) and may manifest as orthostatic hypotension, reduced HR variability, baseline tachycardia (decreased inhibitory input), deep breathing, and prolonged QT interval. Patients with the above symptoms may be at increased risk for sudden death [Charlson ME et al. JACS 179: 1, 1994], and bradycardia non-responsive to atropine has been described in diabetic surgery patients [Burgos et al. Anesthesiology 70: 591, 1989]
endocrine- diabetes - The gastrointestinal system may be affected as well, and patients with autonomic symptoms (ex. gastroparesis) should be considered at risk for pulmonary aspiration Diabetic patients may also be at increased risk for perioperative nerve injuries [Stoelting p. 439], although this has not been definitively established endocrine- thyroid - Most commonly caused by Graves' disease, most-often in women 20 - 40 years of age (0.2% incidence in parturients). Elective procedures should be deferred until the disease is well-controlled (B-blockers [inhibit peripheral conversion of T4 to T3 in addition to controlling heart rate, goal rate is 85 bpm], antithyroids [methimazole and propylthiouracil, both of which block synthesis of new thyroid hormones but do not affect release of existing hormone. Methimazole works more quickly and has less side effects], +/- iodine [blocks the actual release of thyroid hormone]) endocrine- thyroid - Preoperative evaluation should always include a neck exam, and in some cases, a CT scan. Hyperthyroid patients can be chronically hypovolemic and vasodilated and are prone to an exaggerated hypotensive response during induction of anesthesia, thus pay attention to volume status preoperatively endocrine- thyroid - When selecting (and using) a neuromuscular blocking (or any) drugs, one should be aware of two concerns - first, the potential for muscle weakness (and theoretical possibility of prolonged effect) and second, the potential for tachycardia with reversal Epinephrine and ephedrine should be used with caution endocrine- thyroid (storm) - Hyperthyroid storm (altered mental status, hyperthermia, tachycardia, CHF, shock, and dehydration) can occur intraoperatively but is most common 6 - 18 hours post-operatively and has a mortality rate of 10-75%. Treat with chilled crystalloid and an esmolol infusion [Thome AC and Bedford RF. Anesthesiology 71: 291, 1989]. Consider 100-200 mg cortisol for hypotension, as well as dexamethasone (inhibits T4-T3 conversion). Propylthiouracil (250-500 mg q6h PO or NG) and sodium iodide (1 g IV over 12 h) are often added, and charcoal, hemodialysis, and plasmapheresis have also been tried endocrine- thyroid (post op complications) - Complications of thyroid surgery include damage to laryngeal nerves, tracheal compression, and hypoparathyoidism. The superior laryngeal nerves supply motors to the cricothyroid muscles (only), as well as supraglottic sensation. The recurrent larnyngeals supply all other muscles in the larynx as well as infraglottic sensation. As patients to say "eeeee" in order to assess these muscles. Tracheal compression is often due to hematoma formation.
See patient early to determine need for premedication needs For latex precautions, use latex free gloves, black bag on circuit, latex-free IV setup (clear masks are OK, as are ETT, LMA, and tape) pediatrics - The tongue is relatively larger, thus making a disproportionate contribution to airway obstruction and moving the glottis anteriorly (especially in children with craniofacial abnormalities, NMJ or CNS disease, tumors, hemangiomas, or URIs). Flexion of an infants head may collapse the airway Pediatric patients often have less pulmonary reserve than adults, and require significantly more oxygen intake, thus they are prone to apnea during direct laryngoscopy The larynx in infants is located at C3-4 (as opposed to C4-5 in adults). The infant epiglottis is large but short and narrow, possibly making a direct view of the larynx easier than in an adult. Note that the posterior commisure is relatively cephalad, predisposing the anterior sublaryngeal airway to trauma from the ETT. The narrowest portion of the infant airway is the cricoid cartilage, which can lead to resistance after passing an ETT through the cords pediatrics- tube sizes - Pediatric Endotracheal Tube Size Age Internal Diameter (mm) Depth (cm) Preterm 2.5 6 - 8 Term 3.0 9 - 10 6 months 3-3.5 10 1 - 2 years 4.0 10 - 11 3 - 4 years 4.5 12 - 13 5 - 6 years 5.0 14 - 15 10 years 6.0 16 - 17 pediatrics- CV - Fetal circulation displays 1) increased PVR 2) decreased Qpulm 3) decreased SVR 4) RtoL shunting through foramen ovale. Hypoxemia or acidosis in the newborn can cause a return to fetal circulation Neonatal hearts are relatively non-compliant and thus stroke volume is relatively fixed - they rely entirely on heart rate to manage cardiac output Murmurs, abnormal heart sounds, dysrhythmias, and cardiomegaly are all important when noted in a newborn. EKG, CXR, and echo are therefore often required pediatrics- CV - Normal Physiologic Variables Age BP (mmHg) HR (/min) RR (/min) Hct (%) 1 kg 45/30 120 - 180 40 - 50 2 kg 55/35 110 - 180 40 - 50 3 kg 65/40 100 - 180 40 - 60 45 - 65
Neonate 75/45 100 - 180 35 - 55 45 - 65 6 mo. 85/50 80 - 18 0 30 - 50 30 - 40 (nadir) 1 year 95/55 80 - 130 20 - 30 34 - 42 10 year 110/60 60 - 100 20 35 - 43 Adult 110/60 60 - 100 15 40 - 50 pediatrics- renal - Newborns have decreased GFR, decreased ability to excrete solid material, and decreased ability to concentrate urine (ie conserve water). Adult values of GFR are reached between 12 and 24 months of life Age (weeks) Urine Output (ml/h) 20 5 cc/hr 30 18 cc/hr 40 50 cc/hr This limited renal resorptive function explains the "physiologic" decrease in bicarbonate (and corresponding acidosis) in newborns (pH 7.26-7.29 at birth, 7.37 at 24h, 7.40 at 1 week) Estimated blood volume changes with age - at term, the body is 78% water, and adult proportions are not reached until between 9 and 24 months. Infants have higher plasma chloride and lower bicarbonate (and pH). In the first ten days of life, normal K values may be as high as 6.5 mEq/L. This drops to 3.5-5.5 mEq/L after 2- 3 weeks of life. Water exchange is also negative during the first week of life due to limited intake. Infants are at high risk for both over and under hydration Children pediatrics- heme - At birth, full term infants have 18-20 g/dL of hemoglobin, 75% of which is HgF (which normalizes by 3-6 months). Hgb will naturally decrease as the infant progresses, reaching a nadir as low as 9-10 g/dL (avg 11.2 g/dL) around 2 months of age [Harriet Lane, 16th ed. CV Mosby, 2002]. In premature infants, however, the nadir may be as low as 6-7 g/dL at 3 or 4 months of age Cross matched blood should be available for newborn surgery. Assessment of clotting function should be considered because prothrombin as well as factors II, VII, and X are limited in young livers pediatrics- caudal - Caudal Block Equipment: 22g B-bevel needle (or angiocath) Drugs: 0.25% bupivacaine or 0.2% ropivacaine +/- morphine 25 ucg/kg or hydromorphone 6 ucg/kg Desired level and volume: Sacral Block: 0.5 ml/kg Midthoracic Block: 1.25 ml/kg
Moderately invasive (bowel reanastamosis) 4-8 cc/kg/hr Significantly invasive (NEC) > 10 cc/kg/hr pediatrics- resuscitation meds - Resuscitation Medication in Children Epinephrine = 10-100 ucg/kg for arrest (100 ucg/kg in ETT), 1-4 ucg/kg for hypotension Atropine = 0.01 - 0.02 mg/kg (0.3 mg/kg in ETT) - actual dose 0.1 - 1 mg Adenosine = 0.1 mg/kg (max dose 6 mg) Lidocaine = 1-1.5 mg/kg SCh = 2-3 mg/kg Rocuronium 1 mg/kg Calcium chloride = 10-20 mg/kg (dilute to 10 mg/cc or else veins will sclerose, try to give centrally if possible) Bicarbonate = 1 mEq/kg (dilute to 1 mEq/cc or else veins will sclerose) Naloxone = 0.1 mg/kg DEFIBRILLATION = 2 J/kg (can increase up to 4 J/kg) OB- fetal distress - In order to obtain a fetal EKG, a presenting fetal part must be available for lead placement. Normal HR is 120-160 with 5-25 beats/min of beat-to-beat variability. Note that maternal opiates, atropine, or anesthetic agents can reduce beat- to-beat variability. Two types of decelerations are problematic - late (starting 10- 30 seconds after contraction onset), which represent uteroplacental insufficiency, and variable, due to cord compression but which are usually benign (but are worrisome if lasting > 30 seconds or accompanied by HR < 70) OB- fetal distress - pH: < 7.0: fetal depression 7 - 7.2: acidosis 7.2-7.25: "pre-acidosis"
7.25: normal pO2: never exceeds 60 mm Hg SpO2: should always exceed 30% HR: 120-160 (5-25 beats/min fluctuation, less with opiates, atropine, or anesthetic agents) OB labor - In the first stage of labor, pain travels via sympathetic nerve fibers (going through the inferior hypogastric plexus on the way to the sympathetic chain) that originate from the T10-L1 segments of the spinal cord (referred to the back as well as abdominal wall) Pain for the second stage is transmitted via the pudendal nerve (S2-4) OB epidural - The advantages of epidural analgesia include avoidance of hyperventilation, reduced maternal catecholamines, and the ability to alter the level of analgesia (including a T4 level if necessary for Cesarean section). Prior to initiating epidural analgesia, it is critical that resuscitation equipment be available. Extra-thecal placement is confirmed with 45 mg lidocaine or 7.5 mg bupivacaine (neither of which
should produce a spinal if injected extra-thecally). For intravascular testing, negative aspiration was shown to be relatively reliable in testing a multiorifice epidural catheter, detecting 47 of 48 intravascular cathers in one study [Norris MC et al. Anesth Analg 88: 1076, 1999; FREE Full-text at Anesthesia & Analgesia]. Given the success of negative aspiration, the use of epinephrine for this purpose is discouraged in the pregnant patient, as false positives sometimes occur [Mulroy M and Glosten B. Anesth Analg 86: 923, 1998] and there is a theoretical possibility of reducing uteroplacental perfusion secondary to the alpha-agonist effects, as has been seen in pregnant ewes [Hood DD et al. Anesthesiology 64: 610, 1986] OB epidural - After placement of an epidural, both the fetus and the uterus should be monitored, as intra-thecal (but not epidural?) administration of opiates has been shown to produce uterine hyperactivity and subsequent fetal bradycardia in at least one case report [Friedlander JD et al. Reg Anesth 22: 378, 1997]. Nitroglycerin is an effective uterine relaxant in obstetric emergencies, as has been proven clinically as well as in animal models [Segal S et al. Anesth Analg 86: 304, 1998] OB epidural - In the past, there was concern that premature placement of an epidural would prolong labor or increase the rate of Cesarean section. Most early randomized, controlled trials comparing the early to late epidurals were small and contained significant crossover [Eltzschig HK et al. N Engl J Med 348: 319, 2003]. Sharma's 2004 metaanalysis, which included > 2000 patients, found no difference [Sharma SK et al. Anesthesiology 100: 142, 2004 metaanalysis], as did Segal et al's study of sentinal events (institutions where epidural use quickly increased found no increase in Cesarean section rates) [Segal S et al. Am J Obstet Gynecol 183: 974, 2000]. The debate about the utility of early epidurals was put to rest by Wong's group, who conducted a RCT of 750 nulliparous women, randomized to thecal fentanyl at first instance of pain vs. IV pain medicine at first instance (early group received epidural analgesia at the second request for analgesia but in the late group not until cervical dilatation achieved 4.0 cm or a third request for analgesia was made), the early epidural group offered the following advantages - "The median time from the initiation of analgesia to complete dilatation was significantly shorter after intrathecal analgesia than after systemic analgesia ( minutes vs. 385 minutes, P<0.001), as was the time to vaginal delivery (398 minutes vs. 479 minutes, P<0.001). Pain scores after the first intervention were significantly lower after intrathecal analgesia than after systemic analgesia (2 vs. 6 on a 0-to-10 scale, P<0.001). The incidence of one-minute Apgar scores below 7 was significantly higher after systemic analgesia (24.0 percent vs. 16.7 percent, P=0.01)" [Wong CA et al. N Engl J Med 352: 655, 2005]. Placement of the epidural should NEVER be delayed simply in order to wait for an arbitrary level of cervical dilation [Camann W. NEJM 352: 718, 2005] OB spinal - 25 or 26 ga. pencil point needle is used to reduce the risk of headache. Lidocaine, tetracaine, bupivacaine, and ropivacaine are commonly used. Women are often maintained in a seated position for up to 2 minutes in an effort to disproportionately anesthetize the perineal region. Note that a true "saddle block" would not completely relieve pain because the uterus itself would not be blocked, thus to
[Shnider SM et al. Anesthesiology 50: 524, 1979]), and via hyperventilation [Levinson G et al. Anesthesiology 40: 340, 1974] OB placental gas exchange - The oxygen dissociation curve is left-shifted in the fetus (which encourages uptake of oxygen from maternal supplies), and the average [Hgb] in the fetus is 17 g/dL, thus while fetal pO2 is only ~ 30 mm Hg, oxygen content is almost identical to that of its mother. A healthy fetus can safely tolerate a 50% reduction in oxygen delivery [Wilkening RB and Meschia G. Am J Physiol 244: H749, 1983] CO2 exchange depends on concentration gradients and uterine blood flow. Note that maternal hypocapnea can cause fetal hypoxia and acidosis secondary to vasoconstriction, decreased venous return (hypocapnea is usually the result of hyperventilation and increased thoracic pressure), and left shift of the maternal oxygen dissociation curve (CO2 leads to unloading of O2, hypocapnea leads to retention of O2) OB PIH/Pre eclampsia - Pregnancy Induced Hypertension Pre-Eclampsia BP > 140/ Proteinuria (> 0.5 g/day) Edema Headache HELLP syndrome Hemolysis Elevated liver enzymes Low platelets Eclampsia Seizures Causes of death in PIH CHF MI Coagulopathies Cerebral hemorrhage Seizures severe if SBP > 160 or DBP > 90, proteinuria > 5g/day or evidence of end organ dysfunction OB preeclampsia - The exact disease mechanism is unknown, though it is thought to be caused by excessive placental thromboxane production (in normal pregnancies, thromboxane:prostacyclin are 1:1, whereas in PIH the ratio is 7:1 [Wang Y et al. Am J Obstet Gynecol 167: 946, 1992]). Intense CNS vasosconstriction may be a common underlying pathophysiological aberration in these patients - postmortem exams have revealed areas of hemorrhagic necrosis OB preeclampsia - Magnesium can decrease CNS irritability (raises seizure threshold), decrease activity at the neuromuscular junction (weakness), and relax uterine and
vascular smooth muscle (increased uterine blood flow). Usually given as 4g load over 5 minutes, followed by 1-2 g/hr. Note that magnesium crosses the placenta, however there is minimal correlation between umbilical cord magnesium levels and the incidence of low APGAR scores Therapeutic range is 4-6 mEq/L - in excess, one finds loss of DTRs, skeletal weakness, hypoventilation, and cardiac arrest (IV calcium is the antidote). Because Mg inhibits ACh release and many preeclamptics have decreased plasma cholinesterase levels, NMBDs must be used very carefully in these patients. Sedatives and opiates must also be decreased OB preeclampsia/ Mg - Magnesium Goal = 4-6 mEq/L (1-2 g/h maintenance) Excess: Decreased DTR Weakness Hypoventilation Cardiac Arrrest Antidote: IV calcium Anesthetic Issues: Use NMBD sparingly Exaggerated hypotensive response to regional Reduce doses of sedatives and opiates exaggerated sympathetic response to laryngoscopy airway edema OB placental transfer - DRUGS WHICH DO NOT CROSS THE PLACENTA
- All paralytics
- Glycopyrrolate
- Insulin
- Heparin DRUGS WHICH CROSS THE PLACENTA Potentially Dangerous
- Opiates (morphine, fentanyl if > 1 ucg/kg)
- Benzodiazepines
- Ephedrine (increased metabolism)
- Local anesthetics
- Atropine
- B-blockers Safe
- Propofol
- Thiopental
- Ketamine
- Fentanyl at < 1 ucg/kg
- Epidural opiates (fentanyl, sufentanil)
respiratory - respiratory - respiratory - chronic anemia - 1) Increased cardiac output: The two principal determinants of SVR are vascular tone and viscosity of blood and in isovolemic hemodilution from chronic anemia, the hematocrit decreases and reduces SVR through decreased viscosity of blood. The decrease in SVR then increases stroke volume and therefore cardiac output and blood flow to tissues. Oxygen delivery usually remains constant at a hematocrit between 30 and 45%. Further reductions in hematocrit are accompanied by increases in cardiac output (up to 180%) baseline as hematocrit nears 20%.
- Redistribution of cardiac output: When isovolemic hemodilution occurs in chronic anemia, blood flow is redistributed to the tissues with higher extraction ratios (brain and heart, for example). This blood is redistributed to the coronary circulation in a healthy heart and coronary blood flow can increase up to 600% of baseline. When the heart reaches the point at which it can no longer increase either cardiac output or coronary blood flow, then it is subjected to possible myocardial injury from decreased oxygen delivery.
- Increased oxygen extraction: In times when the hematocrit reaches less than 25%, the oxygen extraction ratio increases in multiple tissue beds, leading to an increase in the total body oxygen extraction ratio and to a decrease in mixed venous oxygen saturation. The brain and heart already have a high extraction ratio and are unable to increase oxygen delivery by this mechanism, but tissues such as the kidney, skeletal muscle, and skin compensate in this manner.
- Changes in oxygen-hemoglobin affinity: The oxyhemoglobin dissociation curve relates the partial pressure of oxygen in the blood to the percent saturation of hemoglobin with oxygen. The P50 at 37 degrees celcius and a pH of 7.4 is 27mmHg. When anemia develops over a long period of time, the oxyhemoglobin dissociation curve is shifted to the right, whereby hemoglobin has a decreased affinity for the oxygen molecule and releases oxygen to the tissues at higher partial pressures. Since this process occurs only after increased 2,3 DPG, it occurs only with chronic anemia and NOT when patients undergo isovolemic hemodilution(see below). prone position - Circulatory ↑ intraabdominal & intrathoracic pressure→ ↓cardiac output, ↓BP IVC obstruction → vertebral venous plexus engorgement → ↑ bleeding, ↑ risk of thrombosis Head low position: venous congestion of face and neck → facial, conjunctival and airway edema Head high position: risk of venous air embolism prone position - Respiratory Cephalad shift of diaphragm, compression abdominal viscera → ↓ FRC, ↑work of breathing, ↑airway pressures
Ventral supports: improved lung volumes, oxygenation, and compliance, esp in obese patients Ventilation and perfusion are more uniform in prone position → ↓ V/Q mismatch → Improved oxygenation prone position - hemodynamic response to prone position ↓Stroke volume, ↓ Cardiac index ↑SVR, ↑PVR HR, PAOP, Right atrial pressure: no change Recommend invasive hemodynamic monitors in patients with precarious cardiovascular status POVL - prone position, nerve injury - Mechanisms ↑ stretch, compression → ischemia Occur despite adequate protection1,12 → other factors? Prone patient Supraorbital, facial, mandibular nerves Brachial plexus and its peripheral components perioperative nerve injury - Neurovascular compromise: •Compression or stretching of intraneural vasa nervorum - neural ischemia •Nerve has a long or superficial course between two points of fixation •Stretching and compression combined - worst •Tissue edema from IV fluid may contribute to neurovascular compression Coexisting medical problems which may contribute to injury: •Diabetes mellitus Uremia •Alcohol abuse Polycythemia vera •Vitamin deficiency Acromegaly •Coagulopathy/ Hypothermia Hypothyroidism perioperative nerve injury, mgmt - • Determine if sensory or motor (sensory is usually transient)
- Avoid stretch and recheck in 5 days
- Contact patient frequently
- If persistent after 5 days- neurology consult Nerve conduction studies EMG If motor, do consult immediately beach chair - Advantages Decreased incidence of brachial plexus injuries vs. lateral decubitus Better surgical exposure Problems
removal of it may not significantly affect pulmonary function. On the other hand, in some patients the diseased lung is the best lung. The best and most current method of estimating split lung function is to perform quantitative V/Q scan. Perfusion scans correlate better with pulmonary function. One can calculate the FEV1 volume of left over lung by knowing percentage of perfusion to left and right lung. For example: Preoperative FEV1 1.5 liters Right Lung Perfusion 30% Left Lung Perfusion 70% The tumor is in the right lung. Following resection of the right lung, we can estimate 1. x .7 = 1.05 liters of the left lung to remain. The minimum acceptable predicted postoperative FEV1 is 800 ml. If the predicted postoperative FEV1 volume is less than 800 milliliters the patient is not a candidate for pneumonectomy. preop thoracic - Step 3: If the patient has predicted post-operative FEV1 value is less than 800 ml, and if the surgeon still feels that he has a resectable lesion with a good prognosis, the next evaluation would be to occlude the pulmonary artery and measure the pulmonary artery pressure at rest and with exercise. If the pulmonary artery pressure is elevated at rest or with exercise, the patient is not a candidate for pneumonectomy. The patient obviously has no capillary bed reserve and is not able to tolerate the loss of vascular bed. He will develop cor pulmonale and the expected 5 year survival will be less than 50%. This can also be done on the operating table by clamping the pulmonary artery and measuring PA pressures preop thoracic - Step 3: If the patient has predicted post-operative FEV1 value is less than 800 ml, and if the surgeon still feels that he has a resectable lesion with a good prognosis, the next evaluation would be to occlude the pulmonary artery and measure the pulmonary artery pressure at rest and with exercise. If the pulmonary artery pressure is elevated at rest or with exercise, the patient is not a candidate for pneumonectomy. The patient obviously has no capillary bed reserve and is not able to tolerate the loss of vascular bed. He will develop cor pulmonale and the expected 5 year survival will be less than 50%. This can also be done on the operating table by clamping the pulmonary artery and measuring PA pressures preop thoracic - Of all the spirometric exams which correlate with pulmonary complications (FVC, MVV, RV/TLC, FEV1%, ppoFEV1%), ppoFEV1 is the most predictive of pulmonary complications [British Thoracic Society. Thorax 56: 98, 2001] ppoFEV1% = preoperative FEV1% x (1 - %functional lung tissue removed/100) Generally, a ppoFEV1% > 40% is low-risk for respiratory complications, and ppoFEV1% < 30% is high risk [Nakahara K et al. Ann Thor Surg 46: 549, 1988, 156 patients]. Note that because of compensatory hyperinflation of the residual lung, eventual FEV1 will exceed ppo FEV1 by 250 mL in lobectomies and 500 mL in pneumonectomies [Zehier B et al. Chest 105: 753, 1995]
preop thoracic - By spirometry, a vital capacity (maximal ins./exp.) of < 50% of predicted or < 2L is predictive of increased risk [Gass GD and Olsen GN. Chest 89: 127, 1986] - according to Barash, "abnormal" vital capacity yields a 10% risk of mortality. FEV1 may be a better indicator than vital capacity - if FEV1 is > 2L, mortality is ~ 10%, whereas for FEV1 < 1L, mortality may increase to > 20% [Lockwood P. Respiration 30: 529, 1973]. Maximum voluntary ventilation < 50%, and RV/TLC > 50% [Mittman C. Am Rev Respir Dis 84: 197, 1961] may also be predictive preop thoracic - Predicted post-operative DLCO is the single strongest predictor of complications and mortality after lung resection [Barash], although it is important to note that DLCO is NOT predictive of long term survival, only perioperative mortality [Wang J et al. J Thorac Cardiovasc Surg 17: 5811, 1999]. Interestingly, ppoDLCO and ppoFEV are poorly correlated, and thus should be assessed independently [Ferguson MK et al. J Thor Cardiovas Surg 109: 275, 1995] ppoDLCO = preoperative DLCO x (1 - %functional lung tissue removed/100) A ppoDLCO < 40% is correlated with increased cardiopulmonary complications. In the National Emphysema Treatment Trial, which included 1218 patients, "high risk" patients (FEV1 < 20% and either ppoDLCO < 20% or homogenous emphysema) showed a 35% risk of death at one year in those who had surgery (as compared to 10% in those who did not) [National Emphysema Treatment Trial Research Group. NEJM 348: 2059, 2003] preop thoracic - Patients with a VO2 max < 10 mL/kg/min are at very high risk [Bechard D et al. Ann Thorac Surg 44: 344, 1987; Bollinger CT et al. Chest 108: 341, 1995], and 15 mL/kg/min may be a reasonable cutoff [Miller's Anesthesia, 7th ed. 2009. p 1821] preop thoracic - In the past a PA catheter was advanced into the lung section of interest, and used to occlude blood flow - if mean PAP increased to more than 40 mm Hg, or if PaO2 < 60 mm Hg or PaCO2 > 45 mm Hg, postoperative respiratory failure or cor pulmonale was likely. A study of 20 patients, however, showed that PA clamping led to an increased PA pressure in only 50% of patients, but 70% had a decreased RVEF [Lewis JW et al. J Thorac Cardiovasc Surg 108: 169, 1994]. Thus, PA occlusion/clamping tests may miss a significant number of patients who suffer adverse RV consequences when the pulmonary vasculature is disrupted, and because of the usefulness of split function studies and other tests, are rarely performed anymore
