Electronic Ordering System Improves Postoperative Pain Management After Total Knee or Hip Arthroplasty.

OBJECTIVES: The authors investigated the impact of computerized provider order entry (CPOE) on the delivery times of analgesia and subsequent patient outcomes. We hypothesized that patients would report less pain and use less pain medications compared with the previous paper-based system. METHODS: Two groups of patients after a total hip (THA) or knee arthroplasty (TKA) were retrospectively compared: one comprising 106 patients when the paper-based ordering system was in effect (conventional group), and one comprising 96 patients after CPOE was installed (electronic group). All patients received a regional anaesthetic at surgery (combined spinal-epidural). TKA patients also received a single-injection femoral nerve block. After transfer to the postoperative anaesthesia care unit (PACU), a patient-controlled epidural analgesia (PCEA) infusion was initiated. The following data was collected from the PACU record: time to initiation of analgesia, visual analog scale (VAS) pain scores at initiation of analgesia and hourly for the first postoperative day (POD), volume of pain medication used, length of stay (LOS) in the PACU and the hospital. RESULTS: The time to initiation of analgesia from arrival in the PACU was significantly lower in the electronic group compared to the conventional group (24.5 ± 28.3 minutes vs. 51.1 ± 26.2 minutes; mean ± SD, p < 0.001), as were VAS pain scores (0.82 ± 1.08 vs. 1.5 ± 1.52, p < 0.001) and the volume of PCEA needed to control pain (27.9 ± 20.2 ml vs. 34.8 ± 20.3 ml, p = 0.001) at 4 hours postoperatively. PACU LOS and hospital LOS did not significantly differ in the two groups. CONCLUSIONS: After implementation of CPOE, patients received their postoperative analgesia faster, had less pain, and required less medication.

The one year incidence of postoperative myocardial infarction in an orthopedic population.

The diagnosis of a postoperative myocardial infarction (PMI) is important in the orthopedic population because these events can be associated with significant cardiac morbidity. Plasma troponin I (cTnI) analysis has markedly increased our ability to detect myocardial damage. Using cTnI analysis for evidence of a PMI, we prospectively assessed all of our patients for (1) the 1-year incidence of PMI, (2) the clinical consequences of a PMI in relation to the level of the cTnI release, and (3) 6-month follow-up for cardiac complications. During a 12-month period, patients at risk for perioperative myocardial ischemia were assessed for a PMI by serum cTnI levels and daily serial ECGs. Patients with cTnI levels above the reference level (> or = 0.4 ng/ml) were also assessed for new cardiac regional wall motion abnormalities with an echocardiogram and 6-month postdischarge adverse cardiac events. Of the 758 patients who were assessed for a PMI, 49 patients had detectable cTnI levels (> or = 0.4 ng/ml); the incidence of a PMI was 0.6% of all surgical cases and 6.5% of those patients were at risk for a cardiac event. A PMI was more common after hip arthroplasty than other orthopedic procedures. Twenty-three patients had a cTnI level >3.0 ng/ml, and 74% these patients (17/23) had anginal symptoms and/or ischemic ECG changes. Nine of these patients (9/23) had new postoperative echocardiographic changes, five (5/23) required emergency transfer to a cardiac care unit, and 10 (10/23) had postoperative cardiac complications. In contrast, 15 patients with levels of cTnI <3.0 ng/ml and without ischemic ECG changes and/or anginal symptoms had no postoperative cardiac complications. Fourteen patients (14/47) had cardiac complications 6 months after discharge, including four cardiac deaths, one fatal stroke, and four patients with unstable anginal episodes that required a change in medical management, and six patients required coronary revascularization. Orthopedic surgical patients with cTnI level <3 ng/ml and without symptoms or ECG changes suggestive of myocardial ischemia (15/49) may have different risks than those with higher-level cTn1.

Are postoperative complications more common with single-stage bilateral (SBTKR) than with unilateral knee arthroplasty: guidelines for patients scheduled for SBTKR.

A significant number of patients with degenerative arthritis of the knee require bilateral knee arthroplasty. Single-stage bilateral total knee arthroplasty (SBTKR) has been associated with increased patient morbidity and mortality. At our institution, the following steps have been taken to minimize the risks to patients undergoing this procedure: regional anesthesia and analgesia, invasive monitoring, postoperative observation in an intensive care unit setting, and aggressive management of hemodynamic aberrations. We reviewed the medical records of 462 sequential total knee arthroplasty patients, consisting of 169 SBTKR and 293 unilateral total knee arthroplasty (UTKR) cases. A total of 122 patients from each group were matched for age, weight, and a history of ischemic heart disease and hypertension. Patients for SBTKR exhibited a significantly higher incidence of fat embolism syndrome and cardiac arrhythmias than UTKR patients. There were no deaths in either group and the incidence of other serious postoperative complications was low and similar between the two groups. Elderly patients (approximately 75 years old) had more postoperative complications. With aggressive clinical management SBTKR can be safely performed in selected patients. Guidelines for the selection of these patients are presented.

The efficacy of antifibrinolytics in the reduction of blood loss during complex adult reconstructive spine surgery.

STUDY DESIGN: Controlled study to assess the efficacy of aprotinin and Amicar in reducing blood loss during complex spinal fusions. OBJECTIVES: To compare blood loss and the clotting profile with a thromboelastogram in patients with spinal deformities undergoing sequential anterior and posterior spinal fusions treated intraoperatively with either aprotinin or Amicar. SUMMARY OF BACKGROUND DATA: Spinal fusion for correction of adult spinal deformities is associated with large blood losses despite the implementation of multiple factors to reduce this blood loss. The antifibrinolytics aprotinin and Amicar have both been shown to reduce blood loss in other surgical procedures with the potential for large blood loss. Hence, we compared their efficacy for reducing blood loss in complex spinal fusions. METHODS: Sixty patients for elective sequential anteroposterior thoracolumbosacral fusions were randomly assigned to three groups: control, aprotinin, and Amicar. Patients were assessed for blood loss, transfusion requirements, postoperative complications, and coagulation profile using a thromboelastogram. RESULTS: The study demonstrated a significant reduction in total blood loss (aprotinin 3628 mL, Amicar 4056 mL, control 5181 mL) and transfusion requirements using the half-dose aprotinin regimen compared with Amicar or control. Aprotinin also preserved the thromboelastogram mean clot formation time, clot strength, and clotting index compared with Amicar or control. CONCLUSIONS: For complex spinal operations with large blood losses, the half-dose aprotinin regimen will reduce blood loss and the need for blood components and may have a role in reducing postoperative lung injury.

Evidence of lung injury during reconstructive surgery for adult spinal deformities with pulmonary artery pressure monitoring.

STUDY DESIGN: Observational analyses of 55 adult patients who underwent elective sequential anterior-posterior thoracolumbosacral surgical corrections for spinal deformities were used to evaluate the efficacy of pulmonary artery catheter monitoring. OBJECTIVE: To demonstrate that during complex reconstructive surgery for spinal deformities, pulmonary artery catheter monitoring identifies a subset of patients with pulmonary injury and is essential in their management. SUMMARY OF BACKGROUND DATA: Patients who undergo sequential anterior-posterior thoracolumbosacral surgical corrections for spinal deformities experience significant perioperative morbidity. Although the value of pulmonary artery catheter monitoring is controversial, its use in these procedures may help identify potential physiologic complications and improve surgical outcome. METHODS: All patients were monitored with a pulmonary artery catheter during surgery until at least postoperative day 1. Outcome measurements included blood loss, vertebral levels fused, operative time, postoperative respiratory complications, and days in intensive care. RESULTS: Eight (8/55; 14.5%) patients according to pulmonary artery catheter monitoring demonstrated elevated pulmonary vascular resistance and noncardiac pulmonary edema. These patients had longer operative procedures with greater blood loss and had more postoperative respiratory complications. They were treated appropriately in intensive care and discharged without further complications. CONCLUSION: Pulmonary artery catheter monitoring of patients who undergo complex spinal fusion facilitates the identification of patients with pulmonary injury and is essential in the management of these patients in the postoperative period. It may, also, be a marker for embolic injury to the lung.

Troponin I as a diagnostic marker of a perioperative myocardial infarction in the orthopedic population.

STUDY OBJECTIVE: To assess the utility of troponin I, the only molecular marker of myocardial injury not expressed in regenerating muscle, in diagnosing perioperative myocardial infarction (MI) in the setting of orthopedic surgery where false elevations in creatine kinase MB isoenzymes (CKMB) are known to occur. DESIGN: Prospective study. SETTING: University-affiliated hospital. PATIENTS: 85 patients with risk factors for coronary artery disease (CAD) who were scheduled for orthopedic surgery, including total knee arthroplasty, 34; total hip arthroplasty, 36; posterior spine fusion, 7; and other orthopedic operations, 8. INTERVENTIONS: Patients were observed in the postanesthesia care unit for at least 24 hours where they had an electrocardiogram (ECG) performed, and blood drawn to rule out MI. MEASUREMENTS: Blood samples for measurement of creatine kinase MB isoenzymes (CKMB) and troponin I were drawn at 8-hour intervals for up to 24 hours. MAIN RESULTS: Five (5/85) patients had elevated levels of both CKMB and troponin I postoperatively. New ECG abnormalities were present in all but one patient who had an old anterolateral MI. Troponin I peaked within 16 hours except in one patient where it continued to increase. That female patient developed cardiogenic pulmonary edema. All the others did well clinically. Six patients (6/85) had a positive CKMB index, and a negative troponin I level. None had ECG changes, except for one in whom subsequent cardiac catheterization showed insignificant CAD. They all did well clinically. All patients with an elevated troponin I level had a positive CKMB index. CONCLUSIONS: Troponin I is as sensitive a marker of MI as CKMB in the orthopedic population, but it has a higher specificity in the perioperative setting. Troponin I can be helpful in properly identifying the source of CKMB elevation postoperatively when this elevation is questionable.

COX-2 specific inhibitors offer improved advantages over traditional NSAIDs.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed medications worldwide and are often the first choice of treatment for acute myalgias, orthopedic injuries, postoperative pain, chronic rheumatoid arthritis, and osteoarthritis. The mechanism through which NSAIDs provide analgesia and suppress inflammation is the inhibition of the enzyme cyclooxygenase, resulting in decreased prostaglandin synthesis. The suppression of prostaglandin synthesis can also produce gastric and renal toxicity, as well as impair normal platelet function. Thus, NSAIDs are associated with potentially harmful side effects. Cyclooxygenase exists in two isoenzymatic forms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Cyclooxygenase-1 appears to be constitutively expressed in many tissues and produces prostaglandins, which regulate normal cellular functions. However, COX-2 activity is induced by proinflammatory cytokines and produces prostaglandins that mediate the inflammatory response and pain signaling transmission. Traditional nonspecific NSAIDs inhibit both COX-1 and COX-2, and in doing so, not only decrease inflammation and pain, but also promote gastrointestinal tract damage and bleeding. The potential clinical benefit of COX-2 inhibitors is significant due to the number of patients chronically treated with NSAIDs and the three- to ten-fold higher risk of gastrointestinal injury and death associated with traditional NSAIDs. Recently, a class of anti-inflammatory medications has been developed that primarily inhibits COX-2 while sparing the enzymatic activity of COX-1 at therapeutic dosages. Two medications that predominantly inhibit only COX-2, rofecoxib and celecoxib, are currently available by prescription in the United States.

Postoperative prophylactic administration of beta-adrenergic blockers in patients at risk for myocardial ischemia.

UNLABELLED: Perioperative myocardial ischemia (MI) is associated with postoperative cardiac morbidity. Postoperative sympatholysis may reduce the incidence of MI. This study evaluated such a reduction postoperatively with the administration of prophylactic beta-blockers in patients undergoing elective total knee arthroplasty with epidural anesthesia and postoperative epidural analgesia. One hundred seven patients were preoperatively randomized into two groups, control and beta-blockers, who received postoperative esmolol infusions on the day of surgery and metoprolol for the next 48 h to maintain a heart rate less than 80 bpm. Patients were followed for ST segment depression by using a Holter monitor and adverse cardiac outcomes. Postoperative electrocardiographic ischemia was significantly more prevalent in the control group compared with the beta-blocker group during esmolol blockade (0 of 52 vs 4 of 55; P = 0.04) and tended to be more common in the control group the next two days (8 of 55 vs 3 of 52; P = 0.135). In addition, the number of ischemic events (control, 50; beta-blockers, 16) and total ischemic time (control, 709 min; beta-blocker, 236 min) were also significantly different from the control group. Myocardial infarctions and cardiac events were more common in the control group, but these differences were not significant. Our results suggest that the use of prophylactic beta-blocker therapy may reduce the incidence of postoperative MI. IMPLICATIONS: Prophylactic beta adrenergic blockade administered after elective total knee arthroplasty was associated with a reduced prevalence and duration of postoperative myocardial ischemia detected with Holter monitoring.

The use of metoprolol and glycopyrrolate to prevent hypotensive/bradycardic events during shoulder arthroscopy in the sitting position under interscalene block.

UNLABELLED: Sudden profound hypotensive and/or bradycardic events (HBE) have been reported in >20% of patients undergoing shoulder arthroscopy in the sitting position under interscalene block anesthesia. Retrospective studies suggest that the administration of beta-blockers is safe and may decrease the incidence of these episodes. We performed a randomized, prospective study to evaluate prophylaxis of these events. One hundred fifty patients were randomized to one of three groups (placebo; prophylactic metoprolol to achieve a heart rate <60 bpm or a maximal dose of 10 mg; or prophylactic glycopyrrolate to achieve a heart rate >100 bpm or a maximal dose of 6 microg/kg) immediately after the administration of the interscalene block. Blood pressure control was achieved with IV enalaprilat as needed. The incidence of HBE was 28% in the placebo group versus 5% in the metoprolol group (P = 0.004). The rate of 22% in the glycopyrrolate group was not significantly different from placebo. Preoperative heart rate and arterial blood pressure, intraoperative sedation score, IV fluids, and enalaprilat use were similar in those patients who had a HBE compared with those who did not. Many aspects of this clinical setting are similar to tilttable testing for patients with recurrent vasovagal syncope, in which beta-adrenergic blockade with metoprolol has also been shown to be effective. We conclude that the Bezold-Jarisch reflex is the most likely mechanism for these events. IMPLICATIONS: Episodes of acute hypotension and bradycardia occur during shoulder arthroscopy in the sitting position under interscalene block. In this study, we demonstrate that metoprolol, but not glycopyrrolate, markedly decreases the incidence of these episodes when given prophylactically immediately after the administration of the block.

Right ventricular function during revision total hip arthroplasty.

Total hip arthroplasty (THA) is associated with pulmonary embolization of cement-bone marrow debris leading to cardiopulmonary complications including cardiac arrest. These complications are more prevalent during revision THA. This report assessed right ventricular function using a right ventricular ejection fraction pulmonary artery catheter (RVEF) and transesophageal echocardiography (TEE) in 18 patients undergoing revision THA. During femoral prosthesis insertion, all patients exhibited hemodynamic changes, but most of these were small and clinically insignificant. Four patients demonstrated a decrease in RVEF > or = 10% and an increase in mean pulmonary artery pressure > or = 10 mm Hg, requiring physician intervention. Two of these patients exhibited signs of pulmonary embolization postoperatively. All patients studied by TEE had detectable intracardiac emboli during femoral arthroplasty. The acute decreases in RVEF and increases in mean pulmonary artery pressures during hip arthroplasty, suggest a role for the embolization of bone marrow debris in the development of the "bone cement implantation syndrome."

Evaluation of brachial plexus anesthesia for upper extremity surgery.

BACKGROUND AND OBJECTIVES: Brachial plexus anesthesia is the preferred anesthetic at the authors' institution for upper extremity surgery. The article is a prospective observational evaluation of brachial plexus anesthesia for surgical success of the block and immediate and postoperative complications. METHODS: Patients for upper extremity surgery (n = 508) received either an interscalene block (n = 266) or an axillary block (n = 242). Surgical anesthesia was achieved in 97% of the patients receiving an interscalene block and 93% receiving an axillary block. RESULTS: For the interscalene block, a proximal paresthesia (shoulder) was as reliable as a more distal paresthesia (forearm, hand) for shoulder surgery. For performance of the axillary block, the transarterial approach was more successful than a single paresthesia for surgical anesthesia (96% versus 80%). Major immediate complications were infrequent, with only one mild seizure in the axillary block group and evidence of intravascular injection in only two of the patients in the interscalene block group. Many of the patients had mild paresthesias on the first day after the operation, 9% for the interscalene block and 19% for the axillary block. The incidence of postoperative neuropraxias decreased significantly by 2 weeks (interscalene block 3%, axillary block 5%), with only one patient in each group still experiencing symptoms beyond 4 weeks. In the interscalene block group, postoperative neuropraxias were associated with the site of paresthesia used for performance of the block and the use of bupivacaine. CONCLUSION: Both interscalene and axillary blocks are safe and effective techniques for upper extremity surgery.

Intraoperative hemodynamic changes are not good indicators of myocardial ischemia.

Intraoperative myocardial ischemia is associated with an increased risk of a perioperative myocardial infarction (PMI) in patients undergoing coronary artery bypass graft surgery. If reversible physiologic variables could be identified that are indicators of myocardial ischemia, treatment might be instituted early to prevent cardiac morbidity. In patients undergoing elective coronary artery bypass graft surgery, we evaluated the relationship between several premorbid patient characteristics, selected hemodynamic variables, intraoperative myocardial ischemia, and a PMI. In addition we evaluated these selected hemodynamic variables as intraoperative indicators of myocardial ischemia. The following variables were evaluated: heart rate, > 80 beats/min; systolic arterial blood pressure, > 160 mm Hg; systolic arterial blood pressure, < 80 mm Hg; mean arterial blood pressure, < 60 mm Hg; pulmonary artery diastolic pressure, > 18 mm Hg; a 5 mm Hg increase in pulmonary artery diastolic pressure; rate pressure product, > 12,000 beats/min.mm Hg; and a pressure rate quotient, < 1.0 mm Hg/beats/min. The premorbid patient characteristics selected were previous myocardial infarction, recent myocardial infarction (within 1 wk of surgery), type and number of coronary lesions, beta-blocker therapy, and calcium blocker therapy. One hundred consecutive (n = 100) patients for elective coronary artery bypass graft surgery were studied prospectively before the initiation of cardiopulmonary bypass (CPB). Patients were monitored with a Hewlett Packard computer ST segment analyzer using leads II and V5. Ischemia was defined as the new onset of ST segment deviation of > or = 1 mm from the baseline electrocardiogram (ECG) (preinduction) for at least 2 min.(ABSTRACT TRUNCATED AT 250 WORDS)

The pressure rate quotient is not an indicator of myocardial ischemia in humans. An echocardiographic evaluation.

BACKGROUND: The pressure rate quotient (PRQ; mean arterial pressure/heart rate [MAP/HR]) less than one (PRQ < 1) has been proposed as a simple, clinically available hemodynamic index of myocardial ischemia. Recent investigations using electrocardiography (ECG) detection of myocardial ischemia have not found this index reliable. We prospectively compared PRQ < 1 to detection of myocardial ischemia via transesophageal echocardiography (TEE) and ECG in patients undergoing elective coronary artery bypass graft. METHODS: Forty-six of 50 patients admitted into the study had acceptable data acquisition. Calibrated ECG leads II and V5 were recorded with a computerized ST-segment analyzer. Hemodynamic data were stored at 2-min intervals. After tracheal intubation, a 5.0-MHz TEE probe was inserted. Electrocardiography-detected ischemia was defined as new onset ST-segment deviation (> or = 1 mm) lasting for > 1 min. Transesophageal echocardiography determination of ischemia was worsening of wall motion > or = 1 grade and lasting > 1 min. PRQ < 1 was compared to ECG and/or TEE as a predictor or indicator of myocardial ischemia. RESULTS: Electrocardiography ischemia occurred during 230 intervals in 10 patients, and in only 41 of 230 (18%) was PRQ < 1. Transesophageal echocardiography-defined ischemia occurred during 592 intervals in 9 patients, and in 119 of 592 (20%) PRQ < 1. Compared to ECG and TEE, PRQ < 1 had a low sensitivity (21%) and poor positive predictive value (25%). CONCLUSIONS: Pressure rate quotient < 1 is an unreliable indicator and predictor of myocardial ischemia when evaluated by ECG, TEE, and the combination of these modalities in patients undergoing coronary artery bypass graft surgery.

The effect of calcium on pulmonary vascular resistance and right ventricular function.

Calcium chloride is frequently administered to patients immediately after separation from cardiopulmonary bypass to improve the contractile state of the myocardium. Animal studies suggest that calcium chloride may produce increases in pulmonary vascular resistance, which can precipitate right ventricular failure. In an attempt to determine the effect of calcium chloride administration after cardiopulmonary bypass on right ventricular function, this study was designed to evaluate patients with normal and elevated pulmonary vascular resistance. Fifty patients scheduled for elective cardiac surgery were prospectively studied for changes in ionized calcium levels before and after bypass. The impact of calcium administration on right ventricular function was assessed by a pulmonary artery catheter modified for the measurement of right ventricular ejection fraction. In all patients the level of ionized calcium decreased during bypass from a mean of 4.91 to 4.29 mg.dl-1. However, the infusion of calcium chloride (10 mg.kg-1) after bypass resulted in increasing the ionized calcium levels to prebypass levels. Administration of calcium chloride after bypass to patients with normal right ventricular function resulted in a transient increase in both cardiac output and right ventricular ejection fraction without any change in pulmonary vascular resistance. Eight patients with both elevated pulmonary vascular resistance and depressed right ventricular function were evaluated to determine the effect of calcium chloride after bypass on pulmonary vascular resistance and right ventricular ejection fraction. Administration of calcium chloride (10 mg.dl-1) to these patients did not result in any significant increase in pulmonary vascular resistance or depression of right ventricular performance. More important, in these patients, right ventricular ejection fraction and cardiac output were significantly increased after calcium chloride administration. In summary, the results of this study fail to demonstrate any increase in pulmonary vascular resistance or deterioration of right ventricular function with the administration of calcium chloride (10 mg.kg-1) after bypass in patients with elevated pulmonary vascular resistance.

Is the pressure rate quotient a predictor or indicator of myocardial ischemia as measured by ST-segment changes in patients undergoing coronary artery bypass surgery?

Perioperative myocardial ischemia is associated with an increased risk of perioperative myocardial infarction (PMI). Several attempts have been made to define intraoperative hemodynamic predictors of myocardial ischemia. In a canine preparation with coronary stenosis, a pressure rate quotient (PRQ = mean arterial pressure/heart rate) less than one (PRQ less than 1) indicated subendocardial myocardial ischemia. The authors tested this hypothesis in patients undergoing elective coronary artery bypass graft operation (CABG), using electrocardiogram (ECG) ST-segment changes (leads II/V5) to diagnose myocardial ischemia. Sixty (n = 60) patients having CABG surgery were prospectively studied before initiation of cardiopulmonary bypass. Calibrated ECG leads II and V5 (diagnostic mode) were monitored continuously and recorded with the use of a Hewlett-Packard computer ST-segment analyzer. In addition, arterial and pulmonary artery pressures were monitored. Ischemia was defined as new-onset ST deviation (greater than or equal to 1 mm from the baseline ECG). ECG and hemodynamic data were stored at 2-min intervals for subsequent computer analysis. Serial creatinine phosphokinase (CPK) X MB (%) determinations and 12-lead ECGs were collected for the initial 3 postoperative days. Of the 3,463 intervals (2 min) available for study, 3,322 (96%) were satisfactorily recorded for 60 patients. Ischemia occurred during 65 intervals in 9 patients (9 of 60), of which only 34% (22 of 65) were associated with a PRQ less than 1 (P less than 0.01). In contrast, there were 466 intervals during which PRQ was less than 1, but without ECG evidence of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence of events in natural infection of Pekin duck embryos with duck hepatitis B virus.

The major mode of natural infection of duck hepatitis B virus (DHBV) in Pekin ducks is vertical transmission, with 95 to 100% of the embryos from DHBV-infected dams eventually becoming infected. Maternally transmitted virus is present in large quantities in the yolk of unincubated eggs and is taken up by the embryo during early development. Synthesis of DHBV DNA in the embryo begins at about 6 days of incubation and coincides with the formation of the liver. DHBV DNA synthesis is incomplete, however, until 8 to 10 days of incubation, as shown by comparing the electrophoretic patterns of DHBV-specific nucleic acid species from embryonic livers at successive stages of development. From 8 days of incubation and continuing throughout embryonic development, subviral particles, which resemble viral replication intermediates isolated from infected livers of post-hatch ducklings, appear in the circulation. These particles contain a polymerase activity that utilizes an RNA template to synthesize viral DNA. Our results suggest that certain host functions, which appear during embryonic development, may be required for DHBV replication and assembly. It is possible that in mammals a similar developmental process occurs. The failure to find human hepatitis B virus in the circulation of most babies, born to hepatitis B virus carrier women, in the first few weeks after birth may reflect such a process.

Naturally occurring infection of Pekin duck embryos by duck hepatitis B virus.

We tested the hypothesis that duck hepatitis B virus (DHBV) is a naturally occurring congenital infection of Pekin duck embryos. Of 219 embryos, 5-25 days after being laid, sera from 30 were found to be positive for endogenous DNA polymerase activity characteristic of hepatitis B-related viruses. The presence of the duck virus was confirmed by hybridization with cloned DHBV DNA. Viral DNA was also found in the livers of embryos incubated for 12 or 18 days. Electrophoretically different forms of DHBV DNA were identified in liver extracts that were not present in serum. These additional liver forms probably represent viral replication intermediates. These observations suggest that the vertical route is a major pathway of DHBV transmission and that viral replication may be initiated by the 12th day of embryonic life.

Changes in nucleosomal core histone variants during chicken development and maturation.

The nucleosomal core histones H2A, H2B, and H3 of the chicken can be resolved by polyacrylamide gel electrophoresis in the presence of nonionic detergents into two primary structure variants each, which occur in different relative amounts in various adult tissues. Quantitative analysis of the histone components throughout embryonic development and posthatching maturation of the chicken revealed that the proportions of the three pairs of variants change independently. Thus, the two H2A variants occur in similar proportions throughout embryonic development and in all adult tissues. In contrast, only one variant each of H2B and H3 is detectable at the earliest stages (primitive streak). The second variant of these histones becomes detectable and increases gradually during somite formation (2-12 days of incubation) to reach a plateau at a level of about 3 and 10% of total H2B and H3 histones, respectively. After hatching, the relative amounts of the minor H2B and H3 variants remain at embryonic levels in those tissues which maintain a high mitotic activity such as blood-forming tissues, but increase with different kinetics in tissues which essentially stop cell division in adults (e.g., liver, kidney, etc.). However, while H2B.2 remains a very minor component in all tissues, H3.3 increases at a relatively high rate for more than a year to become the predominant H3 variant in the liver and kidney of older chickens. The changes in chicken core histone variant proportions appear to be related to changes in growth rate rather than cell differentiation. The extensive change of H3 variant proportions in nondividing adult tissues is most likely due to replication-independent incorporation of H3.3 into nucleosomes.