[Finger pain and personality changes after chemotherapy initiation via a central venous port system in a 67-year-old female patient]. / Fingerschmerz und Wesensveränderungen nach Chemotherapieeinleitung über einen Portkatheter bei einer 67-jährigen Patientin.

Central venous port systems are an integral part of chemotherapy. Early recognition and management of arterial malposition are crucial to prevent further complications. A 67-year-old female with breast cancer underwent central venous port implantation for adjuvant chemotherapy. After administration of the first chemotherapy the patient developed acute bihemispheric cerebral infarction and myocardial ischemia due to arterio-arterial emboli with a toxic encephalopathic component. After systemic lysis and surgical removal of the central venous port system, the patient showed a complete recovery.

[Comments on the guidelines (2018) of the European Society of Cardiology (ESC) and the European Society of Hypertension (ESH) on the management of arterial hypertension]. / Kommentar zu den Leitlinien (2018) der Europäischen Gesellschaft für Kardiologie (ESC) und der Europäischen Gesellschaft für Hypertonie (ESH) für das Management der arteriellen Hypertonie.

Arterial hypertension represents one of the most frequent chronic diseases that can lead to complications, such as stroke, dementia, heart attack, heart failure and renal failure. By 2025 the number of hypertensive patients will increase to approximately 1.6 billion people worldwide. The new guidelines of the European Society of Cardiology (ESC) and the European Society of Hypertension (ESH) on the management of arterial hypertension replace the guidelines of the ESC/ESH from 2013. The 2018 guidelines of the ESC/ESH were adopted by the German Cardiac Society and the German Hypertension League. In these comments national characteristics are worked out and the essential new aspects of the guidelines are critically discussed. These include, for example, the definition of hypertension, the importance of out of office blood pressure measurements, revised blood pressure targets, the modified algorithm for drug treatment and the relevance of device-based hypertension treatments. Important aspects for the management of hypertensive emergencies are also presented.

A tertiary hospital audit of the use of medical imaging in the 24 h preceding death.

This study aims to investigate the number, modality and indication for imaging studies performed on acute hospital inpatients in the 24 h prior to death. Data were obtained from retrospective analysis of deceased patients from a university affiliated tertiary hospital over a 2-year period and it was found that around one in five inpatients received medical imaging in the last 24 h of their life (364 of 1855, 19.6%).

Ideal care and the realities of practice: interdisciplinary relationships in the management of advanced cancer patients in Australian emergency departments.

PURPOSE: Over the course of their illness, a person with cancer is likely to see a number of different healthcare professionals, including those in the emergency department (ED). There is limited research examining the interaction and communication between the involved healthcare professionals when such a patient presents to the ED. This study aimed to explore the views and experiences of interdisciplinary interactions of healthcare professionals caring for patients with advanced cancer who present to the ED. METHODS: Focus groups and semistructured interviews were conducted with clinical staff working in ED, oncology and community and hospital-based palliative care services. Interviews and focus groups were recorded and transcribed verbatim. Thematic analysis was undertaken by three researchers independently. These themes were then discussed by the wider team and consensus reached on themes and subthemes. RESULTS: Eighty-three healthcare professionals participated in focus groups, and 11 were interviewed. The over-arching theme to emerge was one of a conflict between ideal care and the realities of practice, particularly arising where clinicians from different services were required to work together to provide care. This idea was further understood through a series of subthemes including communication, decision-making and understanding of other services. CONCLUSIONS: Participants articulated agreed upon ideals of optimal care for advanced cancer patients across all three services, however there was frequently discord between these ideals and the actual care provided. Service demands and the day-to-day stressors of practice appeared to influence people's actions and engender conflict.

Care of the dying cancer patient in the emergency department: findings from a National survey of Australian emergency department clinicians.

BACKGROUND: Patients with cancer are presenting to emergency departments (ED) for end-of-life care with increasing frequency. Little is known about this experience for patients and ED clinicians in Australia. AIMS: To assess the barriers and enablers regarding end-of-life care for cancer patients as perceived by Australian ED clinicians. METHODS: There were 4501 Australian ED clinicians invited through their professional colleges to complete an online survey, using multiple-choice and free-text responses. RESULTS: A total of 681 ED clinicians responded, most (84.2%) felt comfortable providing care to the dying and found it to be rewarding (70.9%). Although 83.8% found caring for the dying a reasonable demand on their role as clinician, 83.8% also agreed that the ED is not the right place to die. Respondents demonstrated a wide range of views regarding caring for this patient group in ED through free-text responses. In addition, 64.5% reported that futile treatment is frequently provided in the ED; the main reasons reported were that limitations of care were not clearly documented, or discussed with the patient or their family. Almost all (94.6%) agreed that advance care plans assist in caring for dying patients in the ED. CONCLUSIONS: Our findings provide important new insights into a growing area of care for ED. Barriers and enablers to optimal care of the dying patient in ED were identified, and especially the reported high occurrence of futile care, likely a result of these barriers, is detrimental to both optimal patient care and allocation of valuable healthcare resources.

Variations of accessory thoracic muscles identified in the ethnically diverse whole-body donation population in Northern California.

Accessory thoracic muscles in humans are relatively common and it is important to draw awareness to their variable presentations and potential clinical implications owing to their close association with the axilla. Here we report four cases of accessory thoracic muscle variations identified in the ethnically diverse whole- -body donation population in Northern California (4 out of 48 donors, 8.3%). Of these, combined presentations of thoracic accessory muscles were observed in two of the donors, one involving bilateral axillary arches and a pectoralis quartus on the left and the other a unilateral axillary arch on the left and bilateral pairs of pectoral fascicles. In the former, the proximal ends of the left axillary arch and pectoralis quartus joined to form a common aponeurosis which inserted onto the deep tendon of the pectoralis major; in the latter, the pectoral fascicles originated from the surface of the ribs and inserted into the deep surface of the pectoralis major muscle. In the other two donors, unilateral axillary arches were observed. Our observations illustrate that accessory thoracic muscles, in isolated as well as combined forms, are commonplace in the general population. We also describe the proposed embryonic origins of these accessory muscles, which may reflect their frequent occurrence, and potential clinical implications of these muscles, as discussed in literature.

Australian resident doctors want more palliative medicine education: a survey of attitudes and perceived needs.

Most expected deaths occur in acute hospitals, and medical staff providing end-of-life care are generally not palliative medicine specialists. Through a voluntary self-administered survey, this study explored resident doctors' attitudes to palliative medicine and their perceived educational needs. Fifty-two resident doctors participated (response rate 39%), mostly acknowledging the importance of palliative medicine to their practice and emphasising that further postgraduate education is necessary.

Aortic arch repair: let it beat!

Objective aortic arch repair (AAR) on the beating heart may reduce cross-clamping times and offer improved postoperative cardiac function.Methods A single-center review of all patients (n = 24) who underwent surgical AAR during biventricular repair between 01/2006 and 01/2008 was done. All patients were operated on under cardiopulmonary bypass (CPB) with antegrade cerebral perfusion (ACP). During AAR, 13 patients (group 1) received cardioplegic arrest, and were compared to 11 patients (group 2) who underwent a beating-heart modification with selective myocardial perfusion. Seventeen patients had additional intracardiac lesions and underwent simultaneous correction during the procedure.Results Durations of CPB, AAR and ACP did not differ statistically between groups. Cardioplegic arrest time was significantly lower in group 1 (34 ± 13 vs. 76 ± 11 min, p = 0.02) and resulted in a subsequent reduction of myocardial ischemic damage as borne out by lower postoperative levels of troponin T and CK-MB (2.5 ± 0.7 vs. 7.1 ± 1.4 ng/mL, p = 0.02; 68.7 ± 11.5 vs. 149.1 ± 27.2 U/l, p = 0.03). We observed an enhanced patient recovery with shorter inotropic and ventilatory support times (p < 0.05).Conclusion Pediatric aortic arch correction on a CPB beating heart with selective myocardial perfusion is technically feasible and safe. The reduction of the myocardial ischemic time is effective and results in less myocardial damage.

[Risk factor "smoking" : smoking cessation in patients with cardiovascular diseases]. / Risikofaktor "Rauchen" : Wege aus der Nikotinsucht bei Patienten mit kardiovaskulären Erkrankungen.

Smoking is the most frequent cause of avoidable premature death. Annually, almost 6 million people die due to nicotine consumption. Comparing modifiable cardiovascular risk factors, smoking has the strongest impact on cardiovascular mortality. More than 50% of all premature myocardial infarctions are related to nicotine consumption. Even in patients with known coronary disease receiving optimal medical therapy, there is a remarkable additional preventive effect of smoking cessation detectable. Therefore, smoking cessation is an essential component of primary and secondary prevention strategies. Smoking cessation programs applying a combination of behavior therapy and supporting medical treatment have been demonstrated to be the most effective.

The effect of feeding adequate or deficient vitamin B6 or folic acid to breeders on methionine metabolism in 18-day-old chick embryos.

Three isotopic tracers ([2,3,3-2H3]-L-serine, [2H11]-L-betaine, and [1-13C]-L-methionine) were administered by amnion injection into 18-day-old chick embryos to investigate the kinetics of methionine metabolism. The embryos utilized were from eggs collected from 34-week-old Cobb 500 broiler breeders that were fed either a control diet containing folic acid (1.25 mg/kg diet) and pyridoxine HCl (5 mg/kg diet) or diets devoid of supplemental pyridoxine or folic acid. Intermediate metabolites of methionine metabolism and polyamines were analyzed in 18-day-old chick embryos. There were no differences in hepatic [2H2] methionine or [2H3] cysteine enrichments or in physiological concentrations of sulfur amino acids for chick embryos from breeders fed the control diet and embryos from breeders fed diets containing no pyridoxine or folic acid. Supplementation of B6 or folic acid did not affect the production of methionine and cysteine in chick embryos. However, breeders fed the control diet with both folic acid and pyridoxine supplementation produced embryos with a two-fold reduction of hepatic homocysteine and increased spermine compared with embryos from breeders fed diets containing no supplemental pyridoxine or folic acid (P < 0.05). Hepatic S-adenosylmethionine for embryos from breeders fed no supplemental B6 was half the concentration compared with embryos from breeders fed the control diet. Embryos from breeders fed the control diet were utilized to determine the proportion of homocysteine going through remethylation and transsulfuration and also to determine the pathway of remethylation. Sixty-five percent of the methyl groups used for homocysteine remethylation from control embryos was via the MFMT pathway. Alternatively, 61% of homocysteine from control embryos was remethylated via the MFMT and the BHMT reactions and 39% of homocysteine was catabolized to cysteine via the transsulfuration pathway. These data show that in embryos, intermediate metabolites of methionine and polyamines increase in concentration when pyridoxine levels are provided in deficient concentrations to the breeder hen. In addition, this research demonstrates that folic acid deficient embryos conserve methionine, rather than catabolize it to cysteine.

Review: Physiological growth trend of current meat broilers and dietary protein and energy management approaches for sustainable broiler production.

The food production system needs to be sustainable including poultry sector to feed the increasing global population. An accepted economical and environmental approach of broiler production is to produce larger broilers faster while using less feed. Broiler production is aimed at producing consumable meat and meat products. The global broiler meat market has evolved over the years with increasing selection pressure shifted toward attaining yield characteristics for increased cut-up parts such as breast and thighs. There is a shift toward a big bird market in the U.S. with approximately 70% of the broiler meat produced from large birds (>2.72 kg). Genetic selection of broilers for quantitative traits such as growth rate and lean muscle mass without increasing the fat mass has altered broiler physiological homeostasis to adapt toward the larger rates of muscle protein turnover. Physiological stresses created due to selection pressures in broilers have produced several muscle myopathies including an emerging one called woody breast myopathy. The sustainable broiler production practice may require humane consideration of raising broilers in less stressful grow-out regimes that will have minimal impact on broiler metabolic health. Another sustainability approach of broiler production toward feed efficiency lies on understanding dietary formulation approach of amino acids and energy that promote optimal nutrient utilization and minimal nutrient output to environment while also fulfilling the growth demands and body composition changes associated with increased protein gain in current meat broilers brought by the genetic progress.

[Limitation of operability. What does the internist need to know?]. / Einschränkung der Operationsfähigkeit. Was muss der Internist wissen?

The number of elderly people that are critically ill and are send for surgery is rising rapidly. As co-morbidities such as heart disease have huge impact on the perioperative risk, identification of specific risk factors should guide the pre- and perioperative management. Several risk scores and the guidelines published by the European Society of Cardiology recently are currently available and are reviewed in the current manuscript. Evaluation of the medical history of the individual patient and functional tests are the basis for further decisions. Patients that are suffering from co-morbidities or reduced physical fitness are identified as risk patients. Patients without risk factors can be sent for surgery without additional evaluation. In moderate risk patients medication should be optimized prior to surgery. Except emergency surgery cases critical illness should be identified and treated before surgery is initiated. Depending on the number of potential risk factors non-invasive cardiac stress tests are recommended. Depending on the results also coronary angiography/-angioplasty should be performed. Acute coronary syndromes or unstable angina should preferentially be treated prior to surgery.

Psychological health in central hypersomnias: the French Harmony study.

BACKGROUND: A large observational French study of central hypersomnia, including narcolepsy with cataplexy (C+), without cataplexy (C-) and idiopathic hypersomnia (IH), was conducted to clarify the relationships between the severity of the condition, psychological health and treatment response. METHODS: 601 consecutive patients over 15 years of age suffering from central hypersomnia were recruited on excessive daytime sleepiness, polysomnography and Multiple Sleep Latency Test (MSLT) results. 517 (47.6% men, 52.4% women) were finally included: 82.0% C+, 13.2% C- and 4.8% IH. Face to face standardised clinical interviews plus questionnaires (Epworth Sleepiness Scale (ESS), short version Beck Depression Inventory (S-BDI), Pittsburgh Sleep Quality Index (PSQI) and 36-item Short Form Health Survey (SF-36)) were performed. Patients affected with a different diagnosis and with and without depressive symptoms were compared. RESULTS: Mean ESS and body mass index were higher in C+ compared with C-/IH patients. Half of the patients (44.9%) had no depressive symptoms while 26.3% had mild, 23.2% moderate and 5.6% severe depressive symptoms. C+ patients had higher S-BDI and PSQI and lower SF-36 scores than C-/IH patients. Depressed patients had higher ESS scores than non-depressed patients, with no difference in age, gender, duration of disease or MSLT parameters. Finally, C+ patients treated with anticataplectic drugs (38.7%) had higher S-BDI and lower SF-36 scores than C+ patients treated with stimulants alone. CONCLUSION: Our data confirmed the high frequency of depressive symptoms and the major impact of central hypersomnias on health related quality of life, especially in patients with cataplexy. We recommend a more thorough assessment of mood impairment in central hypersomnias, especially in narcolepsy-cataplexy.

Non-cellulosic polysaccharide content in feed ingredients and ileal and total tract non-cellulosic polysaccharide digestibility in 21- and 42-day-old broilers fed diets with and without added composite enzymes.

An initial study profiled non-cellulosic polysaccharide (NCP) levels in feed ingredient samples-corn, soybean meal (SBM), whole soybean, and distillers dried grains with solubles (DDGS). A separate NCP digestibility assay was performed in broilers at day 21 (grower phase) and day 42 (finisher phase) fed corn-soy based diets with and without composite enzymes (phytases, multi-carbohydrases, and proteases). Negative control (NC), NC + composite enzymes (NC+E), and positive control (PC) diets were tested. Negative control and NC + E diets were isocaloric, 3,020 kcal/kg ME at grower phase and 3,026 kcal/kg ME at finisher phase. Positive control diet was formulated to meet the Cobb standard nutrient specifications. Diets, pooled digesta, and excreta samples from all treatment diets were collected from 21- and 42-day-old birds and NCP content analyzed as soluble NCP (S-NCP) and insoluble NCP (I-NCP) fractions. Digestibility coefficient (DC) values were determined for all dietary treatments for both the feeding periods. Results from the ingredient analysis showed NCP levels of ∼7 to 10% in corn samples, ∼8 to 11% in SBM samples, ∼11 to 14% (including pectin level) in whole soybean, and ∼12 to 17% in DDGS samples, suggesting variation (P < 0.05) in NCP levels existed within ingredient samples. Digestibility assays showed that enzyme treated (NC + E) diet improved DC values at day 21 from 6 to 10 units and 6 to 9 units for ileal and total tract collection, respectively, for I-NCP fraction (P < 0.05) compared to DC values for NC or PC diets. The ileal DC values at day 42 were not different between treatment diets (∼0.6) but total tract DC values improved 9 to 11 units for broilers fed NC + E diet compared to NC or PC diets. Higher DC values for S-NCP were observed for all treatments for both feeding periods (∼0.7-ileal and ∼0.8-total tract) compared to DC values for I-NCP. Overall, the use of supplemental enzymes in corn-soy-based diets showed improvement in total NCP digestion.

Lung injury edema in dogs. Influence of sympathetic ablation.

Increased vascular permeability characterizes lung injury pulmonary edema and renders fluid balance in the injured lung especially sensitive to changes in hydrostatic pressure. Pulmonary edema is often associated with increased sympathetic nervous system activity which can lead to pulmonary venoconstriction. This postcapillary venoconstriction could raise microvascular pressure and might therefore increase edema in the injured lung. We produced lung injury edema in dogs with oleic acid and directly measured small (less than 2 mm) pulmonary vein pressure. We found that the small pulmonary vein pressure was increased from 9.8 +/- 0.5 mmHg to 12.6 +/- 0.5 mmHg (n = 10) by oleic acid injury edema. The increase was not due to a rise in left atrial pressure since the small pulmonary vein-left atrial pressure gradient also increased. To test if this increase in the postcapillary pressure gradient was sympathetically mediated, we either unilaterally ablated the stellate ganglion or produced unilateral alpha adrenergic blockade with phenoxybenzamine before giving oleic acid. Both of these "antisympathetic" interventions prevented the increase in pulmonary vein pressure caused by oleic acid edema in the protected lung but not in the intact contralateral lung. These interventions produced a 30 +/- 6.8% reduction in the amount of edema caused by oleic acid. Restoring the increase in small vein pressure by inflating a balloon in the left atrium of dogs with bilateral stellate ganglion ablations abolished the reduction in edema produced by antisympathetic treatment. However, the decrease in edema was not significantly correlated with the reduction in pulmonary vein pressure. Thus, the mechanism of the effects of these antisympathetic interventions remains unclear. We conclude that lung injury edema causes sympathetically mediated pulmonary venoconstriction and that antisympathetic interventions significantly reduce lung injury edema and microvascular pressure.

Effects of hypermetabolism on ventilation and chemosensitivity.

Muscular exercise is associated with hypermetabolism and increased hypoxic ventilatory response (HVR). In order to dissociate mechanical and metabolic factors, the effect of hypermetabolism on hypoxic ventilatory response was evaluated at rest. Carbohydrate and protein feeding increases metabolic rate, and their effects on chemosensitivity, ventilation, and blood pH were evaluated in six normal subjects 2 h and 3 h after calorically equal test meals (1,000 cal). After carbohydrate, base-line oxygen consumption (Vo(2)) increased from 237+/-11.3 ml/min (SEM) to 302+/-19.4 (P < 0.001) and 303+/-18.5 (P < 0.001) at 2 h and 3 h, respectively. Hypoxic ventilatory response, measured as shape parameter A, increased from a control of 144+/-11.8 to 330+/-61.0 (P < 0.01) at 2 h and 286+/-57.0 (P < 0.05) at 3 h. These changes were associated with a mild metabolic acidosis as pH decreased from a control of 7.402+/-0.004 to 7.371+/-0.009 (P < 0.005) at 2 h and 7.377+/-0.008 (P < 0.005) at 3 h. After protein, Vo(2) increased from 241+/-6.7 to 265+/-6.2 (P < 0.02) and 270+/-5.4 (P < 0.001), an overall increase less than that which occurred after carbohydrate (P < 0.01). Hypoxic ventilatory response increased from 105+/-14.5 to 198+/-24.3 (P < 0.02) at 2 h and 219+/-17.3 (P < 0.01) at 3 h, which was not different from the increase with carbohydrate. After protein, no acidosis occurred. Thus, after protein, HVR increased despite the absence of a systemic acidosis. We conclude that both carbohydrate and protein feedings are associated with resting hypermetabolism and increased HVR compared with the fasting state. For both meals, increased metabolic rate was correlated with increased hypoxic response.

Hypoxia-induced increases in pulmonary transvascular protein escape in rats. Modulation by glucocorticoids.

Pulmonary edema after ascent to altitude is well recognized but its pathogenesis is poorly understood. To determine whether altitude exposure increases lung vascular permeability, we exposed rats to a simulated altitude of approximately 14,500 feet (barometric pressure [Pb] 450 Torr) and measured the pulmonary transvascular escape of radiolabeled 125I-albumin corrected for lung blood content with 51Cr-tagged red blood cells (protein leak index = PLI). Exposures of 24 and 48 h caused significant increases in PLI (2.30 +/- 0.08 and 2.40 +/- 0.06) compared with normoxic controls (1.76 +/- 0.06), but brief hypoxic exposures of 1-13 h produced no increase in PLI, despite comparable increases in pulmonary artery pressure. There were associated increases in gravimetric estimates of lung water in the altitude-exposed groups and perivascular edema cuffs on histologic examination. Normobaric hypoxia (48 h; fractional inspired oxygen concentration [FIO2] = 15%) also increased lung transvascular protein escape and lung water. Dexamethasone has been used to prevent and treat altitude-induced illnesses, but its mechanism of action is unclear. Dexamethasone (0.5 or 0.05 mg/kg per 12 h) started 12 h before and continued during 48 h of altitude exposure prevented the hypoxia-induced increases in transvascular protein escape and lung water. Hemodynamic measurements (mean pulmonary artery pressure and cardiac output) were unaffected by dexamethasone, suggesting that its effect was not due to a reduction in pulmonary artery pressure or flow. The role of endogenous glucocorticoid activity was assessed in adrenalectomized rats that showed augmented hypoxia-induced increases in transvascular protein escape, which were prevented by exogenous glucocorticoid replacement. In summary, subacute hypoxic exposures increased pulmonary transvascular protein escape and lung water in rats. Dexamethasone prevented these changes independent of reductions of mean pulmonary artery pressure or flow, whereas adrenalectomy increased pulmonary vascular permeability and edema at altitude. Increases in vascular permeability in hypoxia could contribute to the development of high-altitude pulmonary edema and endogenous glucocorticoids may have an important influence on pulmonary vascular permeability in hypoxia.

The red cell mass--arterial oxygen relationship in normal man. Application to patients with chronic obstructive airway disease.

The normal relationship between red cell mass measured, with (51)chromium-labeled red cells, and arterial oxygen saturation (Sa(O2)) over the range from 97.3 to 83.4% was examined by studying 73 normal men residing at sea level and altitudes of 1600 and 3100 m. A simple, linear relationship between Sa(O2) and red cell mass was found over the entire range (r = - 0.7524, P < 0.001). In contrast, a correlation between red cell mass and arterial O(2) tension was found only over the lower half of the range of O(2) tensions where Sa(O2) was also decreased (r = - 0.7731, P < 0.005). This suggested that O(2) saturation rather than tension is the more important determinant of the erythropoietic response to chronic hypoxia. If this response is regulated by tissue O(2) tension, then it will be influenced by O(2) transport, which, in turn, is a function of blood flow and arterial O(2) content, and hence Sa(O2). In nine patients with chronic obstructive airway disease the relationship between red cell mass and Sa(O2) was also determined and was found to be steeper than in the normal subjects (P < 0.05).

Hereditary aspects of decreased hypoxic response.

Decreased ventilatory responses to hypoxia and hypercapnia have been demonstrated in a variety of disorders; however, the etiology of these decreased drives remains virtually unknown. Recent observations have suggested a familial influence on hypoxic and hypercapnic ventilatory response, but it is unclear whether this influence is the result of hereditary or environmental influences. Therefore we measured the ventilatory response to isocapnic hypoxia (HVR) and hyperoxic hypercapnia in 12 pairs of identical and 12 pairs of nonidentical twins. Significant correlation (P less than 0.01) was found for HVR within identical twin pairs but not within nonidentical twin pairs. Identical twins resembled each other more closely with respect to HVR than was the case for nonidentical twins (P less than 0.0125). This was independent of body size, blood PCO2, or pH. No such correlation could be found for ventilatory response to hyperoxic hypercapnia. It is concluded that hereditary influences affect HVR and it is speculated that such influences may play a role in clinical conditions characterized by decreased hypoxic ventilatory responses.

Bradycardia during sleep apnea. Characteristics and mechanism.

To determine the characteristics of and mechanisms causing the bradycardia during sleep apnea (SA), both patients with SA and normals were studied. Evaluation of six consecutive SA patients demonstrated that bradycardia occurred during 95% of all apneas (central, obstructive, and mixed) and became marked with increased apnea length (P less than 0.01) and increased oxyhemoglobin desaturation (P less than 0.01). Heart rate slowed 9.5 beats per minute (bpm) during apneas of 10-19 s in duration, 11.4 bpm during 20-39s apneas, and 16.6 bpm during 40-59-s apneas. Sleep stage had no effect unexplained by apnea length or degree of desaturation. Oxygen administration to four SA patients completely prevented the bradycardia although apneas lengthened (P less than 0.05) in three. Sleeping normal subjects did not develop bradycardia during hypoxic hyperpnea but, instead, HR increased with hypoxia in all sleep stages, although the increase in HR was not as great as that which occurred while awake. Breath holding in awake normals did not result in bradycardia during hyperoxia (SaO2 = 99%), but was consistently (P less than 0.01) associated with heart rate slowing during room air breath-holds (-6 bpm) at SaO2 = 93%, with more striking slowing (-20 bpm) during hypoxic breath-holds (P less than 0.01) at SaO2 = 78%. Breath holding during hyperoxic hypercapnia had no significant effect on rate. Breath holding in awake SA subjects demonstrated similar findings. We conclude that the bradycardia of SA is a consistent feature of apnea and results from the combined effect of cessation of breathing plus hypoxemia.