Capacity to give surgical consent does not imply capacity to give anesthesia consent: implications for anesthesiologists.

There is precedent in medicine for recognizing and accepting intact decisional capacity and the subsequent ability to provide valid consent in one treatment domain, while simultaneously recognizing that the patient lacks decisional capacity in other domains. As such, obtaining consent for anesthesia for a surgical procedure is a separate entity from obtaining consent for the surgery itself. Anesthesia for surgery and the surgical procedure itself are separate treatment domains and as such require separate consents. Anesthesiologists should understand the independence of these functionally linked consent processes and be vigilant with respect to the informed consent process. The cases reported in this article show that capacity for surgical consent may be inadequate for consent to anesthesia because anesthesia involves more abstract concepts requiring a higher cognitive state than surgery, thus requiring a higher state of cognitive capacity for understanding.

Unrecognized drug-drug interactions: a cause of intraoperative cardiac arrest?

Many physicians overlook, or are unaware of, most drug-drug interactions. In our patient, the local anesthetic used for an axillary block may have been the precipitating drug in a cascade of drug-drug interactions that resulted in a cardiac arrest. The combination of multiple preoperative drug-drug interactions prevented the return of a stable native cardiac rhythm for almost 24 h. The mechanisms of interactions of these frequently used drugs are described, and the reader is guided to sources that identify and simplify the understanding of potentially dangerous drug-drug interactions.

Outcomes of cardiopulmonary resuscitation and predictors of survival in patients undergoing coronary angiography including percutaneous coronary interventions.

We studied the outcome of cardiopulmonary resuscitation (CPR) in patients undergoing coronary angiography (CA) and/or percutaneous coronary interventions (PCI). Of 51,985 CA and PCI patients treated between January 1, 1990, and December 31, 2000, 114 required CPR. Records were reviewed for relationships between patient characteristics and various procedures and short-term survival. Long-term survival was compared with that of a matched cohort of patients who did not have an arrest during catheterization and a matched cohort from the general Minnesota population. Over the 11-year period, the overall incidence of CPR was 21.9 per 10,000 procedures. This rate decreased from 33.9 per 10,000 before 1995 to 13.1 per 10,000 after 1995. Overall survival to hospital discharge after CPR was 56.1%. Survival to discharge was less frequent with a history of congestive heart failure, previous coronary artery bypass graft surgery, hemodynamic instability during the procedure, and with prolonged or emergent catheterizations. Pulseless electrical activity (versus asystole or ventricular fibrillation) indicated very poor short-term survival. Interestingly, short-term survival was not related to the extent of coronary artery disease. Long-term survival of patients who survived cardiac arrest was comparable to that of those who did not have arrest during catheterization. In conclusion, the incidence of periprocedural CPR during diagnostic or interventional coronary procedures decreased after 1995. Patients who received CPR in the cardiac catheterization lab have a remarkably frequent survival to hospital discharge rate. Long-term survival of these patients is only minimally reduced.

Long-haul air travel before major surgery: a prescription for thromboembolism?

OBJECTIVE: To investigate the Incidence of postoperative venous thromboembolism (VTE) in patients who had flown long distances before major surgery. PATIENTS AND METHODS: Using the Mayo Clinic computerized patient database, we Identified patients who had flown more than 5000 km before major surgery (travelers) and had experienced an episode of clinically significant VTE within 28 days after surgery. Individual medical records were reviewed for the diagnosis of VTE, pertinent risk factors, and outcome. We compared the Incidence of VTE in travelers to the incidence of VTE in patients from North America (nontravelers) undergoing similar surgical procedures. RESULTS: Eleven patients met our criteria for long-haul air travel and clinically significant VTE within 28 days after surgery. Compared with nontravelers undergoing similar surgical procedures, long-haul travelers had a higher Incidence of VTE (4.9% vs 0.15%; P < .001). Compared with nontravelers who developed VTE, travelers were younger (P = .006), developed VTE earlier in the postoperative course (P = .01), had higher American Society of Anesthesiologists physical status classification (P = .02), and had higher prevalence of smoking (P = .007). Of the 11 travelers with VTE, 10 were of Middle Eastern origin. CONCLUSION: Prolonged air travel before major surgery significantly increases the risk of perioperative VTE. Such patients should receive more Intensive VTE prophylactic measures during the flight and throughout the perioperative period.

Neostigmine-induced prolonged neuromuscular blockade in a patient with atypical pseudocholinesterase.

A patient with unrecognized atypical pseudocholinesterase was given succinylcholine and then vecuronium before neuromuscular monitoring was instituted. Subsequently, when neostigmine and glycopyrrolate were given to reverse what was thought to be a nondepolarizing block, the patient became further relaxed, and his trachea could not be extubated for more than 10 hours. In this report, we discuss drug interactions, phase II block, and the importance of timely neuromuscular monitoring.

Myocardial stunning during abdominal hysterectomy in a healthy woman.

We report a case of myocardial stunning in a healthy patient. During gynecologic surgery, two brief episodes of asystole occurred. Following resuscitation there was a short period of severe hypertension and tachycardia. Electrocardiographic changes and elevations in troponin T and creatine-kinase-MB were observed. Angiography revealed normal coronary arteries and multiple areas of hypokinesis. Within 2 weeks, all abnormal values had returned to normal and the patient underwent an uneventful surgery.

Echocardiographic and hemodynamic evaluation of cardiovascular performance during laparoscopy of morbidly obese patients.

BACKGROUND: The effects of morbid obesity, pneumoperitoneum (PP) and body position on cardiac function during laparoscopy were studied. METHODS: Transesophageal echocardiography (TEE) was performed on 10 obese patients (body mass index, BMI, 48.1+/-1.8 kg/m2) and 10 normal weight patients (BMI = 22.6+/-0.8 kg/m2) in supine, Trendelenburg and reverse Trendelenburg positions before and after PP. Left ventricular end-systolic wall stress (LVESWS) was calculated from invasive blood pressure (BP) values and LV dimensions obtained by TEE. Diastolic filling was assessed by mitral valve and pulmonary vein flow velocities. RESULTS: LVESWS was higher in obese patients both at baseline (46.0+/-4.0 x 10(3) dyn/cm2) and with PP (69.3+/-8.2 x 10(3) dyn/cm2), than normal weight subjects (31.9+/-3.7 x 10(3) dyn/cm2 and 45.7+/-5.9 x 10(3) dyn/cm2; P <0.05 obese vs normal weight patients at baseline). Systolic BP was not different between groups at baseline (normal weight 111+/-4 mmHg, obese 119+/-3 mmHg), but increased significantly with PP only in obese patients (normal weight 129+/-6 mmHg, obese 157+/-8 mmHg; P <0.05). Postural changes during PP had no impact on cardiac function in either obese or normal weight subjects. CONCLUSIONS: Anesthetized obese patients undergoing laparoscopy have higher LVESWS before pneumoperitoneum (due to increased end-systolic left ventricular dimensions) and during pneumoperitoneum (due to more pronounced increases in blood pressure). Since LVESWS is a determinant of myocardial oxygen demand, more aggressive control of blood pressure (ventricular afterload) in MO patients may be warranted to optimize the myocardial oxygen requirements.

Inadvertent positive end-expiratory pressure caused by a malfunctioning ventilator relief valve.

IMPLICATIONS: During anesthesia, a nurse draped several gas hoses over the ventilator relief valve on the back of the anesthesia machine, causing a malfunction. Unintended positive end-expiratory pressure was administered to the patient. Causes of this mishap, anesthesia machine design, and nonanesthesiologist familiarity with anesthesia machine components and their function, are discussed.

The effects of tidal volume and respiratory rate on oxygenation and respiratory mechanics during laparoscopy in morbidly obese patients.

UNLABELLED: Morbidly obese (MO) patients undergoing laparoscopy have lower PaO(2) compared with normal-weight (NW) patients. We hypothesized that increases in tidal volume (V(T)) or respiratory rate (RR) would improve oxygenation. All measurements were performed at: 1) baseline: V(T) 600-700 mL and 10 breaths/min, 2) double V(T): V(T) 1200-1400 mL and 10 breaths/min, and 3) double rate: V(T) 600-700 mL and 20 breaths/min. We calculated static respiratory system compliance (Cst,rs) and inspiratory resistance (RI,rs). End-tidal CO(2) was measured with a mass spectrometer, and PaO(2) and PaCO(2) with a continuous blood gas monitor. Supine anesthetized MO patients had 29% lower Cst,rs than the NW patients (P < 0.05). Positioning patients head-up or head-down before pneumoperitoneum did not significantly affect Cst,rs in either group (P = 0.8). Doubling the V(T), but not RR, increased Cst,rs in both groups. Pneumoperitoneum caused large decreases in Cst,rs in both groups (both P < 0.001). During pneumoperitoneum, changing the body position, V(T), or RR did not further affect Cst,rs in either group (P > 0.7). Before pneumoperitoneum, RI,rs was higher in the MO patients compared with the NW patients regardless of body position (P = 0.01). Doubling either RR or V(T) before pneumoperitoneum did not change RI,rs in either group. After pneumoperitoneum, RI,rs increased in both the head-down and head-up positions (P < 0.05), but not in the supine position. Regardless of the conditions studied, alveolar-arterial difference in oxygen tension was always significantly higher in MO patients (P < 0.05). The alveolar-arterial difference in oxygen tension was not affected by body position, pneumoperitoneum, or the mode of ventilation. Arterial oxygenation during laparoscopy was affected only by body weight and could not be improved by increasing either the V(T) or RR. IMPLICATIONS: Morbid obesity decreases arterial oxygenation and respiratory system compliance. During laparoscopy, arterial oxygenation is affected only by the patient's body weight. Increases in tidal volume or respiratory rate do not improve arterial oxygenation.