Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Propofol versus propofol-ketamine sedation for retrobulbar nerve block: comparison of sedation quality, intraocular pressure changes, and recovery profiles

We compared sedation quality, intraocular pressure (IOP) changes, and recovery profiles in patients who received propofol or propofol-ketamine sedation during placement of the retrobulbar nerve block (RBB). Seventy elderly patients undergoing cataract extraction according to a prospective, randomized, double-blinded protocol were preoperatively evaluated with a Mini-Mental State examination and baseline IOP. A hypnotic dose was provided with either propofol (Group P) or a propofol-ketamine (Group PK) combination. The IOP measurement was repeated, and the surgeon initiated the RBB. Supplemental study drug was given if needed. The level of sedation was considered acceptable if the patient exhibited minimal or no movement and grimacing with needle insertion. Patients were evaluated in terms of quality of sedation, cardiopulmonary stability, and recovery profile. Compared with patients in Group P, patients in Group PK had a significantly faster onset of acceptable sedation (Group P 235 +/- 137 s versus Group PK 164 +/- 67 s) and required significantly less supplemental sedation (Group P 1.1 +/- 1.9 mL versus Group PK 0.15 +/- 0.3 mL). Additionally, none of the Group PK patients required ventilatory assistance, but two patients in Group P required assisted mask ventilation. In conclusion, the addition of ketamine (13.2 +/- 3.3 mg) to propofol (44 +/- 11 mg) decreased the hypnotic requirement and improved the quality of sedation without prolonging recovery.

IMPLICATIONS

Anesthesiologists frequently perform retrobulbar blocks while simultaneously providing sedation. Using ketamine to supplement propofol sedation provided a faster onset and improved the quality of sedation during the retrobulbar block procedure.

Hemodynamic effects of methylprednisolone in patients undergoing cardiac operation and early extubation

BACKGROUND

Whether or not methylprednisolone is beneficial during cardiac operation remains controversial. This study examines the effects of the drug on complement activation and hemodynamics in patients undergoing cardiac operation and early extubation.

METHODS

Patients undergoing cardiac operation were randomized to receive either intravenous methylprednisolone (group MP) or intravenous placebo (group NS). Complement 3a (C3a) levels and hemodynamic parameters were obtained perioperatively. Extubation was accomplished at the earliest clinically appropriate time.

RESULTS

Both groups exhibited equivalent increases in C3a levels after exposure to bypass. Group MP exhibited increased cardiac index, decreased systemic vascular resistance, and increased shunt flow when compared to group NS. More group MP patients required hemodynamic support and group MP patients had prolonged extubation times.

CONCLUSIONS

Methylprednisolone was unable to attenuate complement activation and led to hemodynamic alterations (primarily vasodilation) that may hinder early extubation in patients after cardiac operations.

Subdural cannulation and local anesthetic injection as a complication of an intended epidural anesthetic

We report a 52-year-old woman scheduled for laparotomy with combined epidural-general anesthesia who experienced abnormal responses to local anesthetic injections administered via the epidural catheter. The catheter subsequently was found to be in the subdural space. A review of the literature is provided.

Somatosensory evoked potential monitoring used to compare the effect of three asymmetric sternal retractors on brachial plexus function

We compared the effect of three different asymmetric sternal retractors on brachial plexus dysfunction using intraoperative somatosensory evoked potentials (SSEPs). We studied 60 patients undergoing coronary bypass and internal mammary harvest. Assessment of brachial plexus function was performed pre- and postoperatively. Patients were assigned the use of a Pittman (MN Scientific Instruments Inc., Minneapolis, MN), Rultract (Rultract Inc., Cleveland, OH), or Delacroix-Chevalier (Delacroix-Chevalier, Paris, France) asymmetric sternal retractor for internal mammary exposure. SSEP changes from baseline during asymmetric retractor use and removal were determined, and average changes were compared among the retractor groups. Patient demographics and baseline SSEP values were similar. Fewer patients in the Delacroix-Chevalier group had decreases in SSEP amplitudes after retractor placement. Of the patients in the Rultract and Pittman groups, 45% and 25%, respectively, had amplitude decreases of >50%, compared with only 5% of the Delacroix-Chevalier patients. Three patients in both the Pittman and Rultract groups and one patient in the Delacroix-Chevalier group suffered brachial plexus symptoms postoperatively. We conclude that the Delacroix-Chevalier retractor is associated with less neurophysiologic evidence of brachial plexus dysfunction during asymmetric sternal retraction compared with either the Pittman or Rultract sternal retractors.

IMPLICATIONS

We used somatosensory evoked potentials to assess the effect of several different asymmetric sternal retractors on brachial plexus dysfunction and to determine which produced the least evidence of nerve damage during surgical exposure of the internal mammary artery.

Pulmonary effects of methylprednisolone in patients undergoing coronary artery bypass grafting and early tracheal extubation

Numerous clinical studies suggest that methylprednisolone may facilitate early tracheal extubation after cardiac surgery, yet no investigation has rigorously examined the use of the drug in this setting. In this prospective, randomized, double-blind, placebo-controlled study, we examined the pulmonary effects of methylprednisolone in patients undergoing coronary artery bypass grafting (CABG) and early tracheal extubation. Sixty patients undergoing elective CABG and early tracheal extubation were randomized into two groups. Group MP patients received i.v. methylprednisolone (30 mg/kg during sternotomy and 30 mg/kg during initiation of cardiopulmonary bypass) and Group NS patients received i.v. placebo at the same two times. Perioperative management was standardized. Alveolar-arterial (A-a) oxygen gradient, lung compliance, shunt, and dead space were determined four times perioperatively. Postoperative tracheal extubation was accomplished at the earliest appropriate time. Both groups exhibited significant postoperative increases in A-a oxygen gradient and shunt (P < 0.000001 for each group) and significant postoperative decreases in dynamic lung compliance (P < 0.000001 for each group). Patients in Group MP exhibited significantly larger increases in postoperative A-a oxygen gradient (P = 0.001) and shunt (P = 0.001) compared with patients in Group NS. Postoperative alterations in dynamic lung compliance, static lung compliance, and dead space were not statistically significant between the groups. The time to postoperative tracheal extubation was prolonged in Group MP patients compared with Group NS patients (769 +/- 294 vs 604 +/- 315 min, respectively; P = 0.05). Methylprednisolone was associated with larger increases in postoperative A-a oxygen gradient and shunt, was unable to prevent postoperative decreases in lung compliance, and prolonged extubation time, which indicate that use of the drug may hinder early tracheal extubation in patients after cardiac surgery.

IMPLICATIONS

Traditionally, methylprednisolone has been administered to patients undergoing cardiac surgery to decrease postoperative pulmonary dysfunction. This study revealed that the drug is associated with larger increases in postoperative alveolar-arterial oxygen gradient and shunt and prolonged tracheal extubation time in patients undergoing coronary artery bypass grafting, which indicate that use of the drug may hinder early tracheal extubation.

Intrathecal morphine for coronary artery bypass grafting and early extubation

Aggressive control of pain during the immediate postoperative period after cardiac surgery with early tracheal extubation may decrease morbidity and mortality. This prospective, randomized, double-blinded, placebo-controlled clinical study examined the use of intrathecal morphine in patients undergoing cardiac surgery and its influence on early tracheal extubation and postoperative analgesic requirements. Patients were randomized to receive either 10 micrograms/kg of intrathecal morphine (n = 19) or intrathecal placebo (n = 21). Perioperative anesthetic management was standardized (intravenous (IV) fentanyl, 20 micrograms/kg, and IV midazolam, 10 mg) and included postoperative patient-controlled morphine analgesia. Of the patients who were tracheally extubated during the immediate postoperative period, the mean time from intensive care unit arrival to extubation was significantly prolonged in patients who received intrathecal morphine (10.9 h) when compared to patients who received intrathecal placebo (7.6 h). Three patients who received intrathecal morphine had extubation substantially delayed because of prolonged ventilatory depression. Although mean postoperative IV morphine use for 48 h was less in patients who received intrathecal morphine (42.8 mg) when compared to patients who received intrathecal placebo (55.0 mg), the difference between groups was not statistically significant. In conclusion, intrathecal morphine offers promise as a useful adjunct in controlling postoperative pain in patients after cardiac surgery. However, the optimal dose of intrathecal morphine in this setting, along with the optimal intraoperative baseline anesthetic that will provide significant analgesia, yet not delay extubation in the immediate postoperative period, remains to be elucidated.

Hands-up positioning during asymmetric sternal retraction for internal mammary artery harvest: a possible method to reduce brachial plexus injury

This study compares the hands-up (HU) with the arms at side (AAS) position to determine whether one is beneficial in reducing brachial plexus stress during asymmetric sternal retraction. Eighty patients undergoing cardiac surgery were assigned to either Group 1 (AAS) or Group 2 (HU). Perioperative neurologic evaluations of the brachial plexus were performed and somatosensory evoked potentials (SSEPs) were collected during internal mammary artery harvest using asymmetric sternal retraction. Demographic data, SSEP changes, and postoperative brachial plexus symptoms were compared between groups. SSEP amplitude decreased in 95% of all patients during retractor placement with substantial decreases (> 50%) observed on the left side in 50% of the AAS and 35% of the HU patients. Amplitude recovery was normally seen in both groups after asymmetric retractor removal. Similar changes were noted, to a lesser degree, on the right side. During asymmetric sternal retraction, HU positioning offered minimal benefit in reducing brachial plexus stress as measured by SSEP. Three of the seven AAS patients who reported brachial plexus symptoms had an ulnar nerve distribution of injury. However, none of the four patients with plexus symptoms in the HU group had ulnar nerve problems, suggesting that the higher incidence of postoperative symptoms observed with AAS positioning may occur from ulnar nerve compression.

Recovery after propofol with and without intraoperative fentanyl in patients undergoing ambulatory gynecologic laparoscopy

This prospective, randomized double-blind study was conducted to examine the effect of intraoperative opioid (fentanyl) supplementation on postoperative analgesia, emesis, and recovery in ambulatory patients receiving propofol-nitrous oxide anesthesia. Eighty patients undergoing ambulatory gynecologic laparoscopy participated. Confounding variables that could influence the incidence of postoperative emesis were controlled. Patients received either fentanyl 100 micrograms (Group I) or ketorolac 60 mg (Group II) intravenously (IV) at the time of anesthetic induction. No further analgesic supplements were given intraoperatively. Anesthesia was induced with propofol and maintained with propofol-nitrous oxide. Atracurium was used for muscle relaxation and reversed with neostigmine and glycopyrrolate. Postoperative pain during early recovery was treated with IV fentanyl 25-50 micrograms (Group I) or IV ketorolac 15-30 mg (Group II). Subsequent breakthrough pain in both groups was treated with IV fentanyl 25 micrograms increments as needed (rescue analgesia). Eighty-four percent of patients in Group I required analgesics during early recovery versus 56% of patients in Group II (P < 0.05). Maintenance dose of propofol was significantly lower in Group I (129 +/- 35 micrograms.kg-1.min-1 than in Group II (170 +/- 63 micrograms.kg-1.min-1. Immediate recovery (emergence) in the two groups was comparable, despite different propofol requirements. Although the incidence of emetic sequelae in the postanesthesia care unit was not significantly different between the two treatment groups, a significantly larger number of patients in Group I (fentanyl group) had emetic sequelae that required therapeutic intervention (Group I 29% versus Group II 10%). Patients in Group I also took a significantly longer time to ambulate and meet criteria for home discharge. These results indicate that, in patients undergoing ambulatory gynecologic laparoscopy, the practice of administering a small dose of fentanyl at the time of anesthetic induction reduces maintenance propofol requirement, but fails to provide effective postoperative analgesia. Fentanyl administration at anesthetic induction increased the need for rescue antiemetics. The relative severity of emetic sequelae could have contributed to delay in ambulation and discharge.

Large-dose intrathecal morphine for coronary artery bypass grafting

Aggressive control of pain during the immediate postoperative period after cardiac surgery, associated with decreased blood catecholamine levels, may decrease morbidity and mortality. This study investigated the use of large-dose intrathecal morphine for cardiac surgery and its effect on postoperative analgesic requirements and blood catecholamine levels. Patients were randomized to receive either 4.0 mg of intrathecal morphine (Group MS) or intrathecal saline placebo (Group NS). Perioperative care was standardized and included postoperative patient-controlled analgesia. Arterial blood samples were obtained perioperatively to ascertain catecholamine levels. Patients in Group MS required significantly less postoperative intravenous morphine than patients in Group NS. Although perioperative norepinephrine and epinephrine levels in Group MS patients tended to be lower than Group NS patients, the differences were not statistically significant. In conclusion, large-dose intrathecal morphine initiates reliable postoperative analgesia but does not reliably attenuate the stress response during and after cardiac surgery.

Central hemodynamic changes associated with pregnancy in a long-term cardiac transplant recipient

We present a case of pregnancy in a woman who had undergone cardiac transplantation and was monitored by "surveillance" biopsy at intervals during the entire course of pregnancy and the immediate postpartum period. Exercise reserve remained normal during these periods despite angiographic evidence of coronary disease and episodes of rejection. Central hemodynamic changes were similar to those expected during normal pregnancy. Hemodynamic stability was maintained during epidural anesthesia for labor and subsequent cesarean section.

A demonstration of validity for certification by the American Board of Anesthesiology

PURPOSE

To investigate the validity of the certification process of the American Board of Anesthesiology. Specifically, does board certification in anesthesiology identify physicians judged to be clinically superior by evaluators who are not part of the certification process?

METHOD

All 154 U.S. anesthesiology program directors (or faculty members they chose to represent them), unaware of the study's intent, were asked whether they would permit each of their residents completing training in 1991 to administer three increasingly complex anesthetic regimens to the directors themselves. This clinical skills rating was compared with the residents' performances in the certification process in 1992. A list of personal characteristics was also provided to the directors so they could identify reasons for less-than-optimal clinical skills ratings. A total of 1,310 residents participated in the certification process in 1992.

RESULTS

A total of 146 programs responded. The directors would have accepted anesthetic care for all three increasingly complex operations from 828 (63.2%) of their own residents; for only the two less complex procedures, from 262 (20%); and for only the least complex procedure, from 127 (9.7%). In addition, 93 residents (7.1%) would not have been accepted to administer anesthesia to their directors for any of these operations. Certification success rates for these groups were 74.6%, 53.8%, 44.9%, and 49%, respectively (p < .00001). The personal characteristics believed important to the practice of anesthesiology were strongly linked to the clinical skills ratings; these included motivation, adaptability, clinical judgment, manual dexterity, several work habits, response to criticism, and handling of stressful situations.

CONCLUSION

These data support validity for certification in anesthesiology and identify characteristics considered necessary for high-quality practice of the specialty.

A model to predict survival at time of postcardiotomy intraaortic balloon pump insertion

To facilitate timely application of new forms of cardiac support to patients at highest risk after cardiotomy despite conventional support with the intraaortic balloon pump, an accurate prediction of survival must be available at the time of weaning from cardiopulmonary bypass. We, therefore, acquired 240 demographic, disease, and perioperative characteristics of 322 patients (mortality rate, 48.4%) who required IABP support to separate from bypass. Four variables available before or within 10 minutes of the first attempt at weaning from bypass significantly predicted mortality by stepwise logistic regression: complete heart block as demonstrated by need for temporary pacing at weaning (p < 0.001), advanced age (p < 0.002), preoperative blood urea nitrogen concentration (p = 0.036), and female sex (p = 0.048). An equation generated by the logistic model predicted a 72.2% survival rate in the 25% of patients at least risk (actual survival rate, 71.6%); in the 25% at greatest risk, death was predicted in 73.0%, and the actual mortality rate was 74.1%. The equation was then prospectively applied to 330 intraaortic balloon pump-supported patients managed at another institution. The overall mortality rate there was 41.2%; in the 25% at least risk, predicted survival rate was 70.5% (actual survival rate, 77.1%), and in the 25% at greatest risk, predicted mortality rate was 75.7% (actual mortality rate, 62.7%). Thus, retrospectively at one institution and prospectively at another, the equation generated by this model based only on data available at the time of weaning from bypass was able to define one subgroup of patients 2.6 to 2.7 times as likely to die as another subgroup from within similar cohorts.(ABSTRACT TRUNCATED AT 250 WORDS)

Steal-prone coronary anatomy and myocardial ischemia associated with four primary anesthetic agents in humans

To examine the relationship between myocardial ischemia in patients with steal-prone coronary anatomy and the administration of isoflurane anesthesia, we reviewed coronary angiograms of 955 patients who had participated in a randomized trial of the use of one of four primary anesthetics for coronary artery bypass operations. Steal-prone anatomy was found in 31.8% of patients who had received enflurane; 40.0%, halothane; 32.6%, isoflurane; and 31.7%, sufentanil. Detected by greater than or equal to 0.1 mV ST segment displacement, ischemia during anesthesia occurred in 290 (30.4%) of all patients with no difference in the incidence among the four primary anesthetics (27.5%-32.9%). Patients with steal-prone anatomy did not suffer more ischemia than patients who needed coronary artery bypass surgery but with other varieties of coronary anatomy. In patients with steal-prone coronary anatomy, the incidence of myocardial ischemia by primary anesthetic was 24.0% with enflurane, 34.4% with halothane, 32.1% with isoflurane, and 38.2% with sufentanil. Systolic blood pressure less than 90 mm Hg during anesthesia occurred in 416 (45.6%) patients and was twice as common during administration of volatile anesthetics than during that of sufentanil. Hypotension did not increase ischemia frequency in patients with steal-prone anatomy with use of any of the four primary anesthetics including isoflurane. Ischemia was temporally related to hypotension in only 9 patients (0.9%). In none of the 42 patients who had steal-prone anatomy and hypotension during isoflurane anesthesia was ischemia temporally related to hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of perfusion pressure and flow in major organ dysfunction after cardiopulmonary bypass

The role of perfusion pressure and flow during cardiopulmonary bypass with moderate hypothermia and hemodilution in the development of new postoperative renal or clinically apparent cerebral dysfunction was examined in 504 adults. Cardiopulmonary bypass flow was targeted at greater than 40 mL.kg-1.min-1 and pressure at greater than 50 mm Hg. Flows and pressures less than target occurred in 21.6% and 97.1% of patients, respectively. Fifteen patients (3.0%) suffered new renal and 13 (2.6%) new central nervous system dysfunction. Low pressure or flow during cardiopulmonary bypass, expressed in absolute values or in intensity-duration units, were not predictors of either adverse outcome. Multivariate analysis identified use of postoperative intraaortic balloon counterpulsation (p less than 10(-6], excessive blood loss in the ICU (p less than 10(-4], need for vasopressors before cardiopulmonary bypass (p less than 10(-4], postoperative myocardial infarction (p less than 10(-3], emergency reoperation (p less than 0.002), excessive postoperative transfusion (p less than 0.02), and chronic renal disease (p less than 0.03) as independent predictors of postoperative renal dysfunction. Independent predictors of postoperative central nervous system dysfunction were cardiopulmonary resuscitation in the intensive care unit (p less than 10(-6], intracardiac thrombus or valve calcification (p less than 0.02), and chronic renal disease (p less than 0.03). Age greater than 65 years (40.7% of patients) did not predict either outcome. We conclude that failure of the native circulation during periods other than cardiopulmonary bypass rather than the flows and pressures considered here is the major cause of renal and clinically apparent central nervous system dysfunction after cardiac operations.

Incidence of perioperative myocardial ischemia detected by different electrocardiographic systems

To determine the extent to which different electrocardiographic systems account for differences in reported incidence of perioperative myocardial ischemia, the authors simultaneously recorded in 109 patients undergoing coronary artery bypass grafting (CABG) the V5 or modified CM5 lead on five ECG systems by means of a specially constructed common V5 lead. The systems included a Spacelabs Alpha 14 Model Series 3200 ECG Cardule at bandwidths of 0.05-125 Hz and 0.5-30 Hz (a typical operating room monitor), a Marquette Electronics MAC II ECG at 0.05-40 Hz and 0.05-100 Hz (a standard ECG), and a Del Mar Holter recorder at 0.1-100 Hz. Relative ST-segment position and incidence of new ischemia compared to the preoperative ECG were determined in 109 sets of preinduction traces and 877 sets of intraoperative traces. ST-segment position on the three recording systems conforming with the American Heart Association (AHA) low-frequency response recommendations (0.05 Hz) were similar. Compared to the standard ECG, ST-segment position on the Spacelabs at 0.5-30 Hz was consistently more negative. Displacement on the Holter was consistently less negative and less positive. By the 0.1-mV displacement criterion for diagnosis of myocardial ischemia on any one ECG system, 16.5% of patients on arrival and 32.1% of patients intraoperatively suffered new myocardial ischemia. Based on the operating room monitor, arrival and intraoperative ischemia were present in 15.6 and 27.5% of patients, respectively. Ischemia at the same periods was less frequent by the standard ECG system (5.5 and 12.8%, respectively) and least frequent by the Holter recorder (4.6 and 8.3%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Stable rightward shifts of the oxyhemoglobin dissociation curve induced by encapsulation of inositol hexaphosphate in red blood cells using electroporation

Rightward shifts of 50-100% of the P50 values in the oxygen dissociation curve of intracellular hemoglobin are obtained after encapsulation of inositol hexaphosphate in mouse and dog red blood cells (RBC) by electroporation. Life spans of mouse RBC-myo-inositol hexaphosphate in circulation are unchanged from the normal RBC values.

Thiopental sodium by single bolus dose compared to infusion for cerebral protection during cardiopulmonary bypass

The authors previously demonstrated that thiopental sodium infused throughout cardiopulmonary bypass (CPB) considerably reduced persistent but not transient neuropsychiatric complications after open-chamber cardiac operations. Based on the probability that emboli released at the time of aortic declamping cause most postoperative central nervous system (CNS) dysfunction, this study was designed to test whether administration of a single bolus dose of thiopental before aortic declamping provided cerebral protection equal to that of infusion throughout bypass as well as a decrease in unwanted side effects. One hundred adult patients undergoing open-chamber cardiac operations with CPB received either thiopental sodium by infusion throughout CPB (n = 52) or thiopental sodium 15 mg/kg by bolus before aortic declamping (n = 48). In 90% of the patients, thiopental sodium 15 mg/kg produced electroencephalographic (EEG) burst suppression, with more than 60 seconds between bursts. Postoperative CNS dysfunction occurred in 3 (6%) of the infusion group patients (thiopental sodium 36 +/- 10 mg/kg) and 2 (4%) of the bolus group patients (thiopental sodium 16 +/- 2 mg/kg). CNS dysfunction persisting to the tenth postoperative day occurred in only one patient, who was in the infusion group. Requirements for inotropic support on separation from CPB did not differ between groups, but average time to extubation was 2.7 hours shorter in the bolus group. The authors conclude that thiopental sodium 15 mg/kg given as a single bolus immediately before aortic declamping without the need for EEG monitoring provided the same brain protection as larger doses given by infusion titrated to burst suppression, but it did not reduce the need for inotropic support during separation from CPB.

Randomized trial of primary anesthetic agents on outcome of coronary artery bypass operations

To examine the role of primary anesthetic agent on outcome of coronary artery bypass grafting operations, 1,012 patients were prospectively randomized to receive enflurane (257), halothane (253), isoflurane (248), or sufentanil (254). Except for administration of the primary anesthetic, anesthesia management was standardized for all patients. The randomized groups did not differ in demographic characteristics, extent of coronary artery disease, chronic antianginal therapy, hemodynamic characteristics including new myocardial ischemia at arrival to the operating room, and surgical characteristics that might influence the rate of postoperative myocardial infarction or death. From anesthetic induction to start of cardiopulmonary bypass, new ST segment depression appeared in 310 (30.4%) patients and was not different among primary anesthetic groups (28.0-33.5%). Similarly, the incidence of postoperative myocardial infarction (3.6-4.7%) and death (1.2-2.4%) was not different. Although intraoperative hypotension was twice as common in patients receiving any volatile anesthetic and hypertension twice as common with sufentanil, tachycardia (greater than or equal to 110 bpm) was not related to any primary anesthetic (4.3-9.1%) and was the only hemodynamic abnormality significantly related to intraoperative ischemia. The strongest predictor of intraoperative ischemia was ischemia on arrival to the operating room. The authors postulate that approximately 90% of new myocardial ischemia observed during anesthesia is the manifestation of silent ischemia observed in patients before operation and only 10% is related to anesthetic management. They conclude that, despite differences in the hemodynamic consequences of the primary anesthetics studied, none of the primary anesthetics influenced outcome and the primary role of the anesthesiologist in management of these patients is control of heart rate.

Does chronic treatment with calcium entry blocking drugs reduce perioperative myocardial ischemia?

To examine the role of chronic calcium entry blocking drug administration on perioperative myocardial ischemia and, specifically, the frequency of hemodynamically unrelated ischemia, the authors studied 444 patients undergoing coronary artery bypass operations. Before induction of anesthesia, 119 patients who chronically took calcium entry blocking drugs received nifedipine 20 mg or diltiazem 60 mg orally, 74 received calcium entry and beta adrenergic blocking drugs, 71 received beta blocking drugs only, and 180 received neither. New ischemia occurred in 208 (46.8%) patients; 55 at arrival to the operating room, 86 only after induction, and 67 separately during both periods. Two-thirds of all ischemia was not related to extremes of heart rate or blood pressure; this type was not less frequent in patients receiving calcium entry blocking drugs. Ischemia did occur less frequently in the two patient groups receiving beta adrenergic blocking drugs (34% vs. 53%), a result of less tachycardia both on arrival (3.4% vs. 15.4%) and during anesthesia, when peak heart rate exceeded 109 bpm in only one of 145 beta-blocked patients compared to 29 of 299 not receiving beta blocking drugs. While ischemia appeared during anesthesia in 34.5% of all patients, its incidence was doubled (63%) when heart rate was greater than or equal to 110 bpm. At lower heart rates, the incidence of ischemia did not differ among groups. With respect to all types of ischemia, patients receiving calcium entry blocking drugs only were indistinguishable from those receiving no antianginal therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

The overstated risk of preoperative hypokalemia

To examine the relation between preoperative hypokalemia and frequency of intraoperative arrhythmias, Holter monitoring was employed in 447 patients undergoing major cardiac or vascular operations, the group at greatest risk for life-threatening arrhythmias. Based on serum potassium levels measured immediately before surgery, 57% of patients were normokalemic (greater than or equal to 3.6 mEq/L), 34% hypokalemic (3.1-3.5 mEq/L), and 9% severely hypokalemic (less than or equal to 3.0 mEq/L). No arrhythmia occurred at any time in 63% of patients and minor arrhythmias (premature atrial and occasional premature ventricular contractions) occurred in 16%. Frequent or complex ventricular ectopy appeared before and during operation in 92 patients (21%) but was not related to preoperative potassium level or history of long-term diuretic therapy. Frequent and complex ventricular arrhythmias were more common in patients with a history of long-term digoxin therapy or congestive heart failure. Even among these patients, hypokalemia or diuretic therapy did not increase the incidence or severity of ectopy. These data fail to support the common practice of delaying operation for acute potassium replacement in patients whose preoperative serum potassium is less than normal, even in the presence of cardiovascular disease.

Venous admixture to radial artery blood samples during cardiopulmonary bypass

The possibility that venous blood could be withdrawn through a radial artery cannula when venous pressure is high was examined in 30 patients during cardiopulmonary bypass for coronary artery bypass operation. Progressive desaturation of radial artery blood occurred when venous pressure was equal to arterial pressure. Desaturation not only increased with duration of venous obstruction but also occurred immediately if the arterial tree was emptied after occlusion. We believe that these observations result from the transcapillary aspiration of deep venous blood and may produce a potential source of error in measuring arterial oxygen tension during cardiopulmonary resuscitation, cardiac tamponade, and profound right heart failure, as well as cardiopulmonary bypass.

Protecting the brachial plexus during median sternotomy

Injury to the brachial plexus was prospectively assessed in 335 patients undergoing median sternotomy for cardiac operation. All patients were placed in the hand-up position (elbows elevated, arms abducted 90 degrees, and elbows flexed) after right internal jugular vein cannulation (23 cannulation attempts were bilateral). Twenty-eight patients had new upper extremity complaints after the operation, of whom 16 (4.8%) had symptoms considered related to injury of the brachial plexus: one with generalized weakness of the left arm, six with localized weakness, pain, or paresthesia plus objective hypesthesia or weakness, and nine with paresthesias but no objective signs. Four injuries were right sided, four left sided, and eight bilateral. At the time of discharge, 15 of 16 were symptom free and the patient with generalized weakness was rapidly improving. Postoperative plexopathy was not related to degree of sternal retraction, dissection of the internal mammary artery, or cannulation of the internal jugular vein. We believe the low incidence and benign course of brachial plexus problems in these patients resulted from careful sternal retraction and use of the hands-up position. Finally, our data do not support internal jugular cannulation as a major cause of plexus injuries after median sternotomy.

Addition of papaverine to cardioplegia does not reduce myocardial necrosis

In a randomized, double-blind prospective study involving 495 patients, we investigated whether the addition of papaverine, 60 mg, to our existing regimen of cold cardioplegia would reduce myocardial necrosis during elective coronary artery bypass operations. Twenty-one (4.2%) patients sustained acute postoperative myocardial infarctions (MI), and 7 (1.4%) died during hospitalization. Neither MI nor death was related to papaverine supplementation. Among 469 patients without postoperative MI, levels of the myocardial-specific isoenzyme of creatine phosphokinase measured 10 hours after aortic cross-clamping were related to ischemic cross-clamp time, but not to papaverine supplementation of cardioplegia. At declamping after completion of distal anastomoses, ventricular fibrillation was more common after cardioplegia without papaverine (32% versus 9%). No other differences between the two groups were found in intraoperative and postoperative hemodynamics, difficulty of weaning from bypass, or postoperative volume requirements. We identified three risk factors for postoperative MI: ECG evidence of new ischemia prior to bypass, unusual technical difficulty with distal anastomoses for the surgeon, and prolonged time of ischemia. We conclude that addition of papaverine to our cardioplegia regimen did not affect outcome or nonspecific myocardial necrosis.

Neuropsychiatric complications after cardiopulmonary bypass: cerebral protection by a barbiturate

The authors prospectively investigated the ability of thiopental to decrease neuropsychiatric complications as a consequence of open-ventricle operations requiring cardiopulmonary bypass. Eighty-nine randomly assigned patients received sufficient thiopental to maintain electroencephalographic silence throughout the period from before atrial cannulation to termination of bypass. These patients received an average of 39.5 mg/kg of thiopental, while 93 control patients received only fentanyl. On the first postoperative day, five thiopental (5.6%) and eight control (8.6%) patients exhibited clinical neuropsychiatric abnormalities. By the tenth postoperative day, all neuropsychiatric dysfunction had resolved in the thiopental group but persisted in seven (7.5%) control patients (P less than 0.025). The incidence of complications was significantly related to calcification of replaced valves, aortic valve replacement, advanced age, and prolonged bypass, but not to low blood pressure during perfusion. The authors believe their data are consistent with embolism as the most important cause of sensory-motor neurologic dysfunction following cardiopulmonary bypass. The data also provide evidence that thiopental in sufficient dosage can reduce the clinical consequences of these events. This is the first demonstration of cerebral protection by a barbiturate in humans.

Does perioperative myocardial ischemia lead to postoperative myocardial infarction?

To determine if a relationship exists between perioperative myocardial ischemia (ST segment depression greater than or equal to 0.1 mV) and postoperative myocardial infarction (PMI), nonparticipating observers recorded all ECG, hemodynamic, and other events between arrival of patients in the operating room and onset of cardiopulmonary bypass during 1,023 elective coronary artery bypass operations (CABG). The roles of preoperative patient characteristics, quality of the operation limited by disease as rated by the surgeon and duration of ischemic cardiac arrest as risk factors for PMI also were quantified. ECG ischemia occurred in 36.9% of all patients, with almost half the episodes occurring before induction of anesthesia. PMI was almost three times as frequent in patients with ischemia (6.9% vs. 2.5%) and was independent of when ischemia occurred. Ischemia was related significantly to tachycardia but not hypertension nor hypotension and was frequent in the absence of any hemodynamic abnormalities. The anesthesiologist whose patients had the highest rate of tachycardia and ischemia had the highest rate of PMI. Although neither single nor multiple preoperative patient characteristics related to PMI, suboptimal quality of operation and prolonged ischemic cardiac arrest increased the likelihood of PMI independent of the occurrence of myocardial ischemia. The authors conclude that perioperative myocardial ischemia is common in patients undergoing CABG, occurs randomly as well as in response to hemodynamic abnormalities, and is one of three independent risk factors the authors identified as related to PMI. PMI is unrelated to preoperative patient characteristics such as ejection fraction and left main coronary artery disease, and its frequency will relate primarily to perioperative management rather than patient selection.

Heart block after coronary artery bypass--effect of chronic administration of calcium-entry blockers and beta-blockers

We evaluated risk of heart block after cardiopulmonary by-pass (CPB) in patients with normal conduction undergoing coronary artery bypass grafting who chronically received calcium-entry blockers, beta-blockers, or combined therapy. Before CPB, calcium-entry blockers alone produced an increase in P-R intervals but no change in heart rate; calcium-entry blocker effects were undetectable after CPB, beta-Blockers alone or with calcium-entry blockers produced lower heart rates and longer P-R intervals throughout the entire perioperative period when compared to no therapy (control) or calcium-entry blockers alone. Complete heart block did not occur; one control patient had transient second degree block after CPB. First degree block appeared transiently in 5% of the patients after anesthetic induction and in 15% on emergence from CPB, but was unrelated to drug therapy. We conclude that chronic calcium-entry blocker therapy has minimal effects on conduction perioperatively; beta-blocker effects persist for up to 10 hr after CPB; and the risk of heart block with either drug or combination is low and should not be a factor in their continued administration preoperatively.

On the safety of radial artery cannulation

The frequency of complications following radial artery cannulation for monitoring purposes was determined in 1,699 cardiovascular surgical patients and in 83 patients in whom cannulation was performed in another artery after failure at the radial site. Patients were examined and radial artery flow determined by a Doppler technique 1 day and 7 days after decannulation. Although partial or complete radial artery occlusion after decannulation occurred in more than 25% of the patients, no ischemic damage to the hand or disability occurred in any patient. Neither duration of cannulation nor the size or material of the cannulas were determinants of abnormal flow. Abnormal flow was significantly related to female sex, the presence of hematoma, and to the use of extracorporeal circulation. The radial arteries of 16 patients whose results of Allen's test were abnormal were cannulated and no abnormal flow or ischemia followed. In 22 patients, the ulnar artery was cannulated after multiple punctures of the ipsilateral radial artery and no ischemia followed. We conclude that in the absence of peripheral vascular disease, the Allen's test is not a predictor of ischemia of the hand during or after radial artery cannulation, that when decreased or absent radial artery flow follows cannulation it is of no clinical consequence, and that radial artery cannulation is a low-risk high-benefit monitoring technique that deserves wide clinical use.

Etiologic factors in neuropsychiatric complications associated with cardiopulmonary bypass

A prospective study of 204 patients undergoing operations requiring cardiopulmonary bypass was undertaken to determine the incidence and etiologic factors leading to postperfusion cerebral dysfunction and to determine whether pretreatment with thiopental, 15 mg/kg, would reduce the incidence. Patients were randomly assigned to a control (diazepam) or study (thiopental) group and were treated identically except for the drug administered. Patients were examined neurologically on the 1st and 4th postoperative day and a psychometric test was administered on the 4th day. Although fewer neuropsychiatric complications were present in patients given thiopental, the difference was not significant. The overall incidence of cerebral dysfunction attributable to cardiopulmonary bypass alone was 16.2% for transient and 6.4% for persistent dysfunction (present at the 10th postoperative day). The incidence of postoperative cerebral dysfunction was more than twice as high in patients undergoing intracardiac than in patients having extracardiac operations and more than 4 times as high in patients more than 60 years of age than in younger patients. Perfusion pressure less than 50 torr with hematocrit less than 30% was not related to development of postoperative cerebral dysfunction. The data suggest that air or particulate emboli originating within the heart or aorta are the major causes of postbypass cerebral dysfunction.

Preoperative propranolol therapy and aortocoronary bypass operation

The relationship between long-term propranolol hydrochloride therapy and subsequent coronary bypass operation was prospectively investigated in 119 patients who were grouped three ways: propranolol therapy continued in full dosage to operation (group A), propranolol therapy discontinued or tapered 24 to 72 hours preoperatively (group B), and no preoperative propranolol therapy (control group). During preoperative hospitalization, one patient in each group A and the control group suffered an increase in anginal symptoms compared with 15 patients in group B, three of whom also had new ventricular arrhythmias. During anesthesia up to the period of cardiopulmonary bypass, 26% of group A patients showed signs of ischemia (eg, ST segment deviation or ventricular arrhythmias) as compared with 51% of the control group and 70% of group B. Hypotension and bradycardia were not more common in group A patients. No differences among groups were noted in case of emergence from bypass, need for cardiac stimulants, or mortality.

Failure of general anesthesia to potentiate propranolol activity

To determine whether halothane and morphine, commonly used during anesthesia for cardiac operations, potentiate the beta blocking activity of propanolol, hemodynamic changes induced by five incremental doses of propranolol (10, 20, 50, 120, 200 microgram/kg) were measured during halothane, 1 per cent, in oxygen, and morphine, 4 mg/kg. Against a background of contant beta stimulation by infusion of isoproterenol, 0.1 microgram/kg/min, and vagal blockade by atropine, 3 mg, propranolol produced significant dose-related decreases in heart rate, cardiac index, stroke volume index, and left ventricular dp/dtmax and significant increases in mean aortic pressure, systemic vascular resistance, and pulmonary capillary wedge pressure. Compared with basal anesthesia with pentobarbital, 15 mg/kg, neither morphine nor halothane increased sensitivity to any measured effect of propranolol expressed as the slope of the log dose-response relationship. It is concluded that the beta blocking activity of propranolol is not potentiated by morphine and halothane anesthesia but, rather, their effects are additive.