Acute withdrawal syndrome related to the administration of analgesic and sedative medications in adult intensive care unit patients.

OBJECTIVES: To estimate the frequency of acute withdrawal syndrome related to the administration of analgesic and sedative medications in mechanically ventilated adult intensive care unit (ICU) patients; to identify associated clinical factors. DESIGN: Retrospective review of medical records. SETTING: An adult trauma/surgical ICU in an urban Level I trauma center. PATIENTS: Twenty-eight mechanically ventilated adult trauma/ surgical ICU patients requiring >7 days of ICU care. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Daily doses of all opioid, sedative, hypnotic, and major tranquilizer drugs administered to each patient were measured, as was duration of ICU stay, duration of mechanical ventilation, and duration of the administration of analgesic, sedative, and neuromuscular blocking agents (NMBAs) for each patient. All opioids and benzodiazepines were converted to their respective fentanyl and lorazepam equivalent units based on potency and bioavailability. Calculation of the weaning rate for each patient during tapering from opioid and benzodiazepine medications was performed. The presence or absence of acute withdrawal syndrome was identified for each patient. Nine (32.1%) patients developed acute withdrawal syndrome potentially related to the administration of analgesic or sedative medications. Patients in the withdrawal group received significantly higher mean daily (p = .049) and peak (p = .032) doses of fentanyl equivalents, as well as higher mean daily lorazepam equivalents (p = .049) compared with patients not experiencing withdrawal. Patients in the withdrawal group were also significantly more likely to have received neuromuscular blocking agents (p = .004) or propofol (p =.026) for >1 day during ICU admission compared with patients not experiencing withdrawal. Duration of mechanical ventilation (p = .049), benzodiazepine therapy (p = .048), and propofol therapy (p = .049) was also significantly longer in the group experiencing withdrawal. Withdrawal patients received a significantly lower mean daily dose of haloperidol (p = .026). There was a significant association between the development of withdrawal syndrome and the presence of ARDS (p = .017). Finally, the slopes of the lines representing opioid and benzodiazepine drug weaning were more steep for the withdrawal group, although these results did not achieve statistical significance. CONCLUSIONS: These results suggest that mechanically ventilated adult patients with extended ICU care (> or =7 days) who receive large doses of analgesic and sedative medications are at risk for acute withdrawal syndromes during drug weaning. The association between ARDS and withdrawal syndrome, combined with the observation that withdrawal syndromes were also associated with the use of neuromuscular blocking agents and prolonged mechanical ventilation, suggests that patients with ARDS may be more likely to receive high doses of analgesic and sedative medications, and are therefore at increased risk for withdrawal syndrome.

Factors affecting perioperative pulmonary function in acute respiratory failure.

To determine the magnitude, duration, and associated factors of perioperative changes in pulmonary function, we retrospectively reviewed the medical records of 145 patients who required preoperative mechanical ventilation for acute respiratory failure before undergoing 200 surgical procedures. Patients were grouped into five pulmonary diagnostic categories: (1) adult respiratory distress syndrome (ARDS) (n = 49); (2) pneumonia (n = 20); (3) atelectasis (n = 65); (4) congestive heart failure (n = 11); and (5) acute ventilatory failure (n = 55). Sixty patients underwent intra-abdominal surgery, 135 patients required surgery on the periphery, and five patients had a thoracotomy. For all patients, PaO2/FIO2 declined significantly from 321 mm Hg (mean) preoperatively to 258 mm Hg intraoperatively, and shunt fraction (Qs/QT) increased from 0.16 to 0.23 without a significant change in PaCO2. The magnitude of the increase in Qs/QT did not differ among pulmonary diagnostic groups. Preoperatively, patients undergoing laparotomy had lower PaO2/FIO2 (278 vs 340) and higher Qs/QT (0.19 vs 0.14) than patients requiring surgery on the periphery. Intraoperatively, Qs/QT increased more during abdominal procedures than during peripheral procedures. Intraoperative hypoxemia (PaO2/FIO2 less than 80 mm Hg) occurred during 13 procedures. Hypoxemic patients had a mean increase in Qs/QT of 0.20 (0.25 preoperatively to 0.45 intraoperatively), and a significant increase in PaCO2 from 38 mm Hg to 45 mm Hg intraoperatively). In general, these patients had ARDS (n = 10), sepsis (n = 10), a laparotomy (n = 9), and intraoperative mechanical ventilation via the Ohio Anesthesia ventilator (n = 8), a commonly used operating room ventilator. Their preoperative peak airway pressure (54 cm H2O) and minute ventilation (20 L/min) requirements exceeded the capabilities of the Ohio Anesthesia ventilator and likely contributed to impaired gas exchange intraoperatively. Within the first several hours postoperatively, PaO2/FIO2 recovered to preoperative levels in all patients, even in those who had severe intraoperative hypoxemia develop and who underwent laparotomy. We conclude that most patients with acute respiratory failure receiving preoperative mechanical ventilation experienced mild-to-moderate deterioration in intraoperative pulmonary oxygen exchange that rapidly returned to preoperative levels after surgery. We recommend that necessary surgery not be postponed by concern that pulmonary function will be worsened by surgery and anesthesia.

Prospective evaluation of radial and femoral artery catheterization sites in critically ill adults.

Prospective evaluation of 178 radial (RAD) and 114 femoral (FEM) artery catheters inserted in 231 critically ill adults in 2 ICUs was performed. FEM catheter duration (5.8 days) was greater than RAD (3.9 days, p less than .001). Most catheters were removed when no longer needed. Complication rates of RAD (7.5%) and FEM catheters (6.9%) were similar. Digital ischemia was the most common complication (3.5%) yet no digital necrosis occurred. Peripheral vascular disease (PVD), greater age, and greater catheter duration were not associated with more complications. Difficult percutaneous and surgical cutdown insertion of RAD catheters was associated with much greater complication rates. In conclusion, FEM and RAD artery catheters have acceptably low complication rates of 7%. Percutaneous FEM catheterization is recommended as a safe alternative to difficult RAD cannulation.

Lung volumes, mechanics, and oxygenation during spontaneous positive-pressure ventilation: the advantage of CPAP over EPAP.

To determine if continuous positive airway pressure (CPAP) or expiratory positive airway pressure (EPAP) is superior for achieving or maintaining effective lung volume in spontaneously breathing critically ill patients in acute respiratory failure, the authors measured functional residual capacity (FRC), airway and esophageal pressures, and arterial oxygen tensions when CPAP and EPAP were 5 and 10 cm H2O. Arterial oxygenation, FRC, and transpulmonary pressure at end-expiration were greatest when CPAP was 10 cm H2O. Lung compliance did not change. The authors conclude that CPAP at 10 cm H2O is the more effective technique, either because it allows relaxation of chest wall musculature on expiration, or because EPAP at 10 cm H2O increases chest wall muscle tone.

Extubation from ambient or expiratory positive airway pressure in adults.

End-expiratory pressure is often used to improve arterial oxygenation and prevent atelectasis in intubated spontaneously breathing patients. To compare the effect of extubation from low levels of expiratory positive airway pressure (EPAP) of extubation from ambient airway pressure, functional residual capacity (FRC) and arterial blood oxygen tension (Pao2) were measured in 12 spontaneously breathing patients during three conditions in the peri-extubation period: 1) intubated at 5 cm H2O EPAP (EPAP 5); 2) intubated at ambient airway pressure (EPAP 0); and 3) within one hour after extubation. During EPAP 5, mean +/- SE values for FRC (1864 +/- 230 ml) and Pao2 (114 +/- 8 torr) were the same as those obtained after extubation (FRC = 1794 +/- 159 ml, Pao2 = 117 +/- 5 torr). However, both FRC (1600 +/- 186 ml) and Pao2 (106 +/- 8 torr) were lower during EPAP 0 than after extubation or EPAP 5 (P less than 0.01-0.05). The magnitude of increase in FRC and Pao2 on extubation from EPAP 0 varied inversely with the patient's lung thorax compliance (r = -0.84, P less than 0.005). It was concluded that a period of EPAP 0 is not necessary in the weaning period, and that it may be deleterious in patients with compromised lung thorax mechanics.

Changes in venous admixture with alterations of inspired oxygen concentration.

To assess the change in venous admixture during breathing of 100 per cent oxygen (FIO2 1.0), shunt fraction (Qs/Qt) was calculated at a maintenance FIO2 (FIO2m:0.27--0.70) and at FIO2 1.0 in 40 studies of 34 patients with acute respiratory failure. At FIO2 1.0 Qs/Qt increased in 26 studies, but did not increase in 14 studies. Patients in whom Qs/Qt increased during breathing of oxygen and mild respiratory failure, as indicated by low Qs/Qt values at FI02m and a low incidence of diffuse parenchymal infiltrates on chest roentgenograms. All patients who had recently had cardiovascular surgical procedures were in this group. Respiratory failure was more severe in those in whom Qs/Qt decreased with oxygen, as indicated by high Qs/Qt values at FIO2m, evidence of diffuse pulmonary disease by roentgenography, and signs of adult respiratory distress syndrome. The authors conclude that changes in Qs/Qt in response to FIO2 1.0 in acute respiratory failure are related to the severity of respiratory insufficiency.

Incidence and outcome of posttraumatic respiratory failure.

From 1972 through 1975, a total of 6,196 patients were admitted to San Francisco General Hospital Trauma Service, of whom 908 required admission to an intensive care unit and 390 required mechanical ventilation. Duration of mechanical ventilation was one week or less for 76%, two weeks or less for 90%, and four weeks or less for 97%. Survival in patients ventilated seven days or less was 64%, in patients ventilated 8 to 14 days it was 55%, and in patients ventilated 15 to 30 days it was 55%. The mortality for ventilated patients aged 20 to 49 years was 23% while for ventilated patients older than age 60 it was 53%. The average age of ventilated patients was 43. Use of controlled-pressure soft-cuff endotracheal tubes has eliminated tracheal-esophageal fistula and tracheal stenosis as causes of morbidity and mortality. Appropriate ventilator alarms have minimized fatalities due to mechanical equipment failure. Complications related to positive pressure ventilation, such as pneumothorax and subcutaneous emphysema, still occur in 12% to 18% of patients. In our patients who survived the acute respiratory distress syndrome, recovery of lung function was universal, and permanent disability was less than 1%.

Ventilator-related extra-alveolar air in adults.

Extra-alveolar air (EAA) developed in 38 patients during mechanical ventilation. High ventilatory pressures and destructive lung disease predispose to EAA. Pneumoretroperitoneum and pneumoperitoneum are more common forms of ventilator-induced EAA in adults than generally realized; an associated pneumomediastinum was always identified when one of the two disorders above resulted from ventilation. Retroperitoneal air was located laterally along the liver and in the flanks, and changed little with change in patient position. Early detection of EAA may allow life-saving changes in therapy to be implemented.

Shunt, lung volume and perfusion during short periods of ventilation with oxygen.

Twenty patients requiring ventilation for acute respiratory failure were studied to determine whether intrapulmonary shunt fraction (Qs/Qt) measured at an inspired oxygen concentration (FIO2) of 1.0 differs from Qs/Qt measured at the clinically indicated FIO2 and, if so, the mechanism by which this occurs. Qs/Qt increased from 15.5 +/- 1.8 per cent (mean +/- SE) at the clinically indicated inspired oxygen fraction (FIO2 0.3-0.6) to 21.7 +/- 2.1 per cent after 20 minutes at FIO2 1.0. Functional residual capacity (FRC) decreased by 6 +/- 6 per cent and total compliance (CT) by 10 +/- 6 per cent. Mean pulmonary arterial pressure fell from 21 +/- 2 to 17 +/- 2 mm Hg, whereas pulmonary capillary wedge pressure (PCWP) and cardiac output remained unchanged. Mixed venous oxygen tension increased from 37 +/- 1 to 45 +/- 2 mm Hg with 100 per cent oxygen. At 90 per cent oxygen, Qs/Qt increased from the value at low FIO2, but FRC and CT did not change. Simultaneous application of 100 per cent oxygen and a positive end-expiratory pressure (6 cm H2O) increased FRC, CT and Qs/Qt. Patients with increased PCWP showed smaller increases in Qs/Qt with 100 per cent oxygen. These findings suggest two mechanisms responsible for the increase in Qs/Qt: 1) redistribution of blood flow to nonventilated areas, resulting from the vasodilating effect of an increased oxygen tension in the vessels of hypoxic lung segments; 2) resorption atelectasis. Of the total change in Qs/Qt observed during ventilation with oxygen, 63 per cent was calculated to be due to factors other than a decrease in FRC. (Key words: Ventilation, positive end-expiratory pressure; Oxygen, pulmonary shunt and; Lung, compliance; Lung, shunts.)

Errors in data derived from pulmonary artery blood gas values.

Blood gas values were obtained from Swan-Ganz pulmonary artery catheters in 25 patients with acute pulmonary failure, with the objective of evaluating the possibility of contamination with "arterialized" blood and examining the mechanism by which this might happen. Blood oxygen content increased significantly from the main to a segmental pulmonary artery, proportional to the withdrawal rate of the sample. At 3 ml/min, distal contents ranged from 100 to 116% of proximal values (p less than 0.01). At 23 ml/min the range was 100-140% of proximal values (p less than 0.001). Sampling of blood from a Swan-Ganz catheter in the usual position for "wedge" pressure measurement, but with a balloon deflated, may lead to large errors in calculation of cardiac output by the Fick method and in calculation of intrapulmonary shunt fraction.

Control of respiratory therapy in flail chest.

Pulmonary mechanics and oxygenation were measured in 24 consecutive patients with posttraumatic flail chest requiring continuous mechanical ventilation. The mean duration of mechanical ventilation was fourteen days. Mortality was 38% for all patients, 29% if deaths from head injury are excluded. Pneumonia occurred in 4 patients (17%) and pneumothorax in 1 (4%). Vital capacity and maximal inspiratory force measurements were useful in assessing chest wall stabilization. Total lung compliance correlated negatively with fatal outcome from respiratory failure. The alveolar-arterial oxygen gradient was not useful in assessing chest wall stabilization.