Optimal lymph node dissection for gastric cancer: a narrative review

The management of gastric cancer has long been debated, particularly the extent of lymph node (LN) dissection required during curative surgery. LN invasion stands out as the most critical prognostic factor in gastric cancer. Historically, Japanese academic societies were the pioneers in defining a classification system for regional gastric LN stations, numbering them from 1 to 16. This classification was later used to differentiate between different types of LN dissection, such as D1, D2 and D3. However, these definitions were often considered too complex to be universally adopted, resulting in wide variations in recommendations from one country to another and making it difficult to compare published studies. In addition, the optimal extent of LN dissection remains uncertain, with initially recommended dissections being extensive but associated with significant morbidity without a clear survival benefit. The aim of this review is to make a case for extending LN dissection based on the existing literature, which includes a comprehensive examination of the current definitions of lymphadenectomy and an analysis of the results of all randomised controlled trials evaluating morbidity, mortality and long-term survival associated with different types of LN dissection. Finally, we provide a summary of the various recommendations issued by organizations such as the Japanese Gastric Research Association, the National Comprehensive Cancer Network, the European Society for Medical Oncology, and the French National Thesaurus of Digestive Oncology.

Iatrogenic ureteral injury during colorectal surgery has a significant impact on patient outcomes: a French multicentric retrospective cohort study

AIM

The long-term urological sequelae after iatrogenic ureteral injury (IUI) during colorectal surgery are not clearly known. The aims of this work were to report the incidence of IUI and to analyse the long-term consequences of urological late complications and their impact on oncological results of IUI occurring during colorectal surgery through a French multicentric experience (GRECCAR group).

METHOD

All the patients who presented with IUI during colorectal surgery between 2010 and 2019 were retrospectively included. Patients with ureteral involvement needing en bloc resection, delayed ureteral stricture or noncolorectal surgery were not considered.

RESULTS

A total of 202 patients (93 men, mean age 63 ± 14 years) were identified in 29 centres, corresponding to 0.32% of colorectal surgeries (n = 63 562). Index colorectal surgery was mainly oncological (n = 130, 64%). IUI was diagnosed postoperatively in 112 patients (55%) after a mean delay of 11 ± 9 days. Intraoperative diagnosis of IUI was significantly associated with shorter length of stay (21 ± 22 days vs. 34 ± 22 days, p < 0.0001), lower rates of postoperative hydronephrosis (2% vs. 10%, p = 0.04), anastomotic complication (7% vs. 22.5%, p = 0.002) and thromboembolic event (0% vs. 6%, p = 0.02) than postoperative diagnosis of IUI. Delayed chemotherapy because of IUI was reported in 27% of patients. At the end of the follow-up [3 ± 2.6 years (1 month-13 years)], 72 patients presented with urological sequalae (36%). Six patients (3%) required a nephrectomy.

CONCLUSION

IUI during colorectal surgery has few consequences for the patients if recognized early. Long-term urological sequelae can occur in a third of patients. IUI may affect oncological outcomes in colorectal surgery by delaying adjuvant chemotherapy, especially when the ureteral injury is not diagnosed peroperatively.

Emergencies in obstetric anaesthesia: a narrative review

We conducted a narrative review in six areas of obstetric emergencies: category-1 caesarean section; difficult and failed airway; massive obstetric haemorrhage; hypertensive crisis; emergencies related to neuraxial anaesthesia; and maternal cardiac arrest. These areas represent significant research published within the last five years, with emphasis on large multicentre randomised trials, national or international practice guidelines and recommendations from major professional societies. Key topics discussed: prevention and management of failed neuraxial technique; role of high-flow nasal oxygenation and choice of neuromuscular drug in obstetric patients; prevention of accidental awareness during general anaesthesia; management of the difficult and failed obstetric airway; current perspectives on the use of tranexamic acid, fibrinogen concentrate and cell salvage; guidance on neuraxial placement in a thrombocytopenic obstetric patient; management of neuraxial drug errors, local anaesthetic systemic toxicity and unusually prolonged neuraxial block regression; and extracorporeal membrane oxygenation use in maternal cardiac arrest.

Impact of adherence goal awareness intervention on PDC in various settings: Does awareness help modify medication-taking behavior?

Background

Interventions to improve medication adherence in chronic conditions have shown limited success or sustainability. Previous data revealed that phone calls to patients regarding adherence goal awareness resulted in significant improvement in proportion of days covered (PDC).

Objectives

The objective of this study was to explore specific pharmacist adherence interventions via phone in various practice settings.

Methods

A prospective, randomized controlled study was conducted with patients who belonged to university-associated health care settings [ambulatory care, chain store, small health plan, and federally qualified health center (FQHC)]. At each site, patients with at least one chronic medication and a calculated PDC < 0.80 were randomized into control (n=115) and intervention (n=126) groups. Control groups (C) received usual pharmacy communication while intervention groups (X) were specifically called by a pharmacist to be informed of PDC goals and their commitment to adherence. PDC values were calculated 3 to 12 months for both groups the time of intervention, then compared with each patient's respective baseline/pre-PDC.

Results

Data from a total of 241 patients were pooled to examine change in PDC. There was no significant difference between groups in baseline criteria or PDC. Comparing within groups, there were significant correlations between Pre- and Post-PDCs for the intervention group (X = 0.32 p < 0.05) alone. There were significant improvements from initial PDC to those calculated at the time of Post-intervention PDC within both groups, (C = 0.18 ± 0.28 p < 0.05) and (X = 0.16 ± 0.24, p < 0.05). Approximately 44% of all sampled patients reached their adherence goals (PDC ≥ 0.80) after 3–9 months.

Conclusions

Results suggested that patient adherence behavior may improve after any call made by pharmacy staff. This communication and attention from the pharmacy may be enough for patients to consider their medication-taking habits without the need for discussing specific goals and importance of adherence.

A review of the Turned-down Onto Pericapsular-tissue Hemisectioned Amputated Toe (TOPHAT) flap for wound coverage during ray amputations of the toes

INTRODUCTION

Exposure of the adjacent Metatarsal-Phalangeal Joint (MTPJ) commonly occurs after application of Topical Negative Pressure Wound Therapy (TNPWT) for a ray amputation wound. This is due to mechanical soft tissue erosion or trauma to the adjacent digital artery from direct pressure effect. This results in toe gangrene requiring a ray amputation and ultimately a larger wound bed. We describe the use of the Turned-down Onto Pericapsular-tissue Hemisectioned Amputated Toe (TOPHAT) flap - a filleted toe flap to protect the adjacent MTPJ capsule combined with a novel Negative Pressure Wound Therapy with instillation and dwell-time (NPWTi-d) dressing technique. The flap protects the adjacent joint capsule and reduces the wound burden whilst allowing the wound to benefit from TNPWT, thereby accelerating wound healing.

MATERIAL AND METHODS

A retrospective review was conducted of patients with toe gangrene requiring ray amputation that underwent the TOPHAT flap on in our institution from 2019 and 2020. Complications such as wound dehiscence, hematoma, flap necrosis and secondary infection were recorded. Other outcomes recorded were time taken to final skin grafting and time taken for complete wound epithelialization.

RESULTS

9 patients underwent treatment with the TOPHAT flap. 2 patients had flap necrosis. 7 patients progressed to definitive skin coverage with skin grafting. One patient subsequently had progressive arterial disease despite successful skin grafting and required above knee amputation. The mean time to final skin grafting and complete wound epithelialization was 49.5 days and 107.5 days respectively. All patients were satisfied with the outcomes and were able to return to their pre-morbid function.

CONCLUSIONS

The TOPHAT flap has a consistent vascular supply that provides durable soft tissue coverage. It is a robust and easily reproducible technique to accelerate wound healing after ray amputations even in patients with peripheral vascular disease.

Are colorectal cancer patients at risk for COVID-19 infection during the postoperative period? The Covid-GRECCAR study

INTRODUCTION

During the COVID-19 pandemic, cancer patients have been regarded as having a high risk of severe events if they are infected with SARS-CoV-2, particularly those under medical or surgical treatment. The aim of this study was to assess the posttreatment risk of infection by SARS-CoV-2 in a population of patients operated on for colorectal cancer 3 months before the COVID-19 outbreak and who after hospitalization returned to an environment where the virus was circulating.

MATERIALS AND METHODS

This French, multicenter cohort study included consecutive patients undergoing elective surgery for colorectal cancer between January 1 and March 31, 2020, at 19 GRECCAR hospitals. The outcome was the rate of COVID-19 infection in this group of patients who were followed until June 15, 2020.

RESULTS

This study included 448 patients, 262 male (58.5%) and 186 female (41.5%), who underwent surgery for colon cancer (n = 290, 64.7%), rectal cancer (n = 155, 34.6%), or anal cancer (n = 3, 0.7%). The median age was 68 years (19-95). Comorbidities were present in nearly half of the patients, 52% were at least overweight, and the median BMI was 25 (12-42). At the end of the study, 448 were alive. Six patients (1.3%) developed COVID-19 infection; among them, 3 were hospitalized in the conventional ward, and none of them died.

CONCLUSION

The results are reassuring, with only a 1.3% infection rate and no deaths related to COVID-19. We believe that we can operate on colorectal cancer patients without additional mortality from COVID-19, applying all measures aimed at reducing the risk of infection.

The incidence of dry chlorhexidine gluconate transfer from skin to surgical gloves: a simulation and in vitro study

BACKGROUND

To prevent alcohol-based chlorhexidine from reaching the cerebrospinal fluid, it is recommended that the antiseptic solution be allowed to dry before skin palpation or puncture. However, no guidelines specify a drying time interval. Manufacturers recommend 3 min of air drying, based upon the isopropyl alcohol component. Therefore, to fill this knowledge gap, we designed a simulation study to investigate the incidence of primary chlorhexidine transfer from skin to gloves following three drying time intervals. We also investigated the incidence of secondary chlorhexidine transfer from gloves to another surface following one drying time interval.

METHODS

An alcohol-based chlorhexidine antiseptic solution with dye, ChloraPrep®, was applied to the skin of the lumbar region of 20 volunteers. Cotton-tipped applicators wrapped in material from gloves were taken from the application area at 3, 4, 5, and 10 min following application. Transfer of chlorhexidine from skin to gloves, and gloves to another medium, was assessed through a chemical assay that produced a color change when chlorhexidine was present on the sample.

RESULTS

The incidence of primary chlorhexidine transfer from skin to gloves at 3, 4 and 10 min following application was 99.5%, 99.4%, and 99.6%, respectively. The incidence of secondary chlorhexidine transfer from gloves to another surface was 68.9%.

CONCLUSION

Gloves are routinely contaminated with chlorhexidine during central neuraxial blockade. The high incidence of secondary transfer in our simulation suggests a pathway by which chlorhexidine may gain access to the neuraxial space.

Colon sparing resection versus extended colectomy for left-sided obstructing colon cancer with caecal ischaemia or perforation: a nationwide study from the French Surgical Association

AIM

It is not known whether patients with obstructive left colon cancer (OLCC) with caecal ischaemia or diastatic perforation (defined as a blowout of the caecal wall related to colonic overdistension) should undergo a (sub)total colectomy (STC) or an ileo-caecal resection with double-barrelled ileo-colostomy. We aimed to compare the results of these two strategies.

METHOD

From 2000 to 2015, 1220 patients with OLCC underwent surgery by clinicians who were members of the French Surgical Association. Of these cases, 201 (16%) were found to have caecal ischaemia or diastatic perforation intra-operatively: 174 patients (87%) underwent a STC (extended colectomy group) and 27 (13%) an ileo-caecal resection with double-end stoma (colon-sparing group). Outcomes were compared retrospectively.

RESULTS

In the extended colectomy group, 95 patients (55%) had primary anastomosis and 79 (45%) had a STC with an end ileostomy. In the colon-sparing group, 10 patients (37%) had simultaneous resection of their primary tumour with segmental colectomy and an anastomosis which was protected by a double-barrelled ileo-colostomy. The demographic data for the two groups were comparable. Median operative time was longer in the STC group (P = 0.0044). There was a decrease in postoperative mortality (7% vs 12%, P = 0.75) and overall morbidity (56% vs 67%, P = 0.37) including surgical (30% vs 40%, P = 0.29) and severe complications (17% vs 27%, P = 0.29) in the colon-sparing group, although these differences did not reach statistical significance. Cumulative morbidity included all surgical stages and the rate of permanent stoma was 66% and 37%, respectively, with no significant difference between the two groups. Overall survival and disease-free survival were similar between the two groups.

CONCLUSION

The colon-sparing strategy may represent a valid and safe alternative to STC in OLCC patients with caecal ischaemia or diastatic perforation.

Peripartum management of a parturient with type 1C (clearance) von Willebrand disease

Peripartum replacement of factor VIII and von Willebrand factor is not usually required in type 1 von Willebrand disease, as the levels of endogenous factors tend to increase to within the normal range as a physiological change of pregnancy. However, there is wide heterogeneity of genotypes and phenotypes associated with type 1 von Willebrand disease. Here, we describe the anesthetic management of a parturient with type 1C von Willebrand disease, a subtype characterized by decreased plasma von Willebrand factor survival.

Thirty-day mortality after emergency surgery for obstructing colon cancer: survey and dedicated score from the French Surgical Association

AIM

The aim was to define risk factors for postoperative mortality in patients undergoing emergency surgery for obstructing colon cancer (OCC) and to propose a dedicated score.

METHOD

From 2000 to 2015, 2325 patients were treated for OCC in French surgical centres by members of the French National Surgical Association. A multivariate analysis was performed for variables with P value ≤ 0.20 in the univariate analysis for 30-day mortality. Predictive performance was assessed by the area under the receiver operating characteristic curve.

RESULTS

A total of 1983 patients were included. Thirty-day postoperative mortality was 7%. Multivariate analysis found five significant independent risk factors: age ≥ 75 (P = 0.013), American Society of Anesthesiologists (ASA) score ≥ III (P = 0.027), pulmonary comorbidity (P = 0.0002), right-sided cancer (P = 0.047) and haemodynamic failure (P < 0.0001). The odds ratio for risk of postoperative death was 3.42 with one factor, 5.80 with two factors, 15.73 with three factors, 29.23 with four factors and 77.25 with five factors. The discriminating capacity in predicting 30-day postoperative mortality was 0.80.

CONCLUSION

Thirty-day postoperative mortality after emergency surgery for OCC is correlated with age, ASA score, pulmonary comorbidity, site of tumour and haemodynamic failure, with a specific score ranging from 0 to 5.

Sepsis in pregnancy and the puerperium

Sepsis remains a leading cause of maternal morbidity and mortality. Recognition and treatment of maternal sepsis are often delayed due to the physiological adaptations of pregnancy and vague or absent signs and symptoms during its initial presentation. Over the past decade, our understanding of sepsis has evolved and maternal early warning systems have been developed in an effort to help providers promptly identify and stratify parturients who are at risk. In addition, new consensus definitions and care bundles have recently been published by the World Health Organization and the Surviving Sepsis Campaign to facilitate earlier recognition and timely management of sepsis. In this narrative review, we summarize the available evidence about sepsis and provide an overview of the research efforts focused on maternal sepsis to date. Controversies and challenges surrounding the anesthetic management of parturients with sepsis or at risk of developing sepsis during pregnancy or the puerperium will be highlighted.

Colonic prolapse after intersphincteric resection for very low rectal cancer: a report of 12 cases

BACKGROUND

There are no published data concerning management of patients with exteriorized colonic prolapse (CP) after intersphincteric rectal resection (ISR) and side-to-end coloanal manual anastomosis (CAA) for very low rectal cancer. The aim of the present study was to report our experience in 12 consecutive cases of CP following ISR with CAA.

METHODS

From 2006 to 2014, all patients with very low rectal cancer who developed CP after ISR and CAA were reviewed. Demographic and surgical data, prolapse symptoms and treatment were recorded. Postoperative morbidity, functional outcomes and results after prolapse surgery were recorded.

RESULTS

Twelve out of 143 patients (8 %) who underwent ISR with side-to-end CAA for low rectal cancer presented CP: 7/107 ISR (7 %) with partial resection of the internal anal sphincter (IAS) and 5/36 ISR (14 %) with subtotal or total resection of the IAS (NS). CP was diagnosed after a median of 6 months (range 2-72 months) after ISR. All patients with CP suffered from pain and fecal incontinence. Median Wexner fecal incontinence score before surgery was 16.5 (range 12-20). Three patients refused reoperation. Nine patients underwent transanal surgery with prolapse resection (including colonic stump and side-to-end anastomosis) and new end-to-end CAA (with posterior myorraphy in 4 cases). After a median follow-up of 30 months (range 8-87 months), 3/9 patients (33 %) had CP recurrence: One with very poor function was treated by abdominoperineal resection and definitive stoma. The 2 others were successfully reoperated on transanally. Median Wexner fecal incontinence score after CP surgery was 9 (range 0-20). No CP recurrence was noted for the 6 other patients, and function improved in all cases. Thus, at the end of follow-up, 8/9 patients (89 %) had no recurrence after surgery.

CONCLUSIONS

We believe surgery must be attempted in these patients who develop CP after ISR with CAA for very low rectal cancer in order to improve function and symptoms. A transanal approach with CP resection and new end-to-end anastomosis appeared to be safe and effective. Larger studies are needed to confirm our results.

Acquired alexithymia following damage to the anterior insula

Alexithymia is a subclinical condition characterized by impaired awareness of one's emotional states, which has profound effects on mental health and social interaction. Despite the clinical significance of this condition, the neurocognitive impairment(s) that lead to alexithymia remain unclear. Recent theoretical models suggest that impaired anterior insula (AI) functioning might be involved in alexithymia, but conclusive evidence for this hypothesis is lacking. We measured alexithymia levels in a large sample of brain-injured patients (N=129) and non-brain-injured control participants (N=33), to determine whether alexithymia can be acquired after pronounced damage to the AI. Alexithymia levels were first analysed as a function of group, with patients separated into four groups based on AI damage: patients with >15% damage to AI, patients with <15% damage to AI, patients with no damage to AI, and healthy controls. An ANOVA revealed that alexithymia levels varied across groups (p=0.009), with >15% AI damage causing higher alexithymia relative to all other groups (all p<0.01). Next, a multiple linear regression model was fit with the degree of damage to AI, the degree of damage to a related region (the anterior cingulate cortex, ACC), and the degree of damage to the whole brain as predictor variables, and alexithymia as the dependent variable. Critically, increased AI damage predicted increased alexithymia after controlling for the other two regressors (ACC damage; total lesion volume). Collectively, our results suggest that pronounced AI damage causes increased levels of alexithymia, providing critical evidence that this region supports emotional awareness.

What happens after R1 resection in patients undergoing laparoscopic total mesorectal excision for rectal cancer? A study in 333 consecutive patients

AIM

There are no studies on the respective influence of microscopic involvement at the circumferential (R1c) and the distal margin (R1d) of the surgical specimen on oncological results after laparoscopic mesorectal excision.

METHOD

We studied 333 consecutive patients undergoing laparoscopic mesorectal excision for cancer. An R1 resection was defined a by a circumferential and/or distal margin of 1 mm or less.

RESULTS

Forty (12%) patients had an R1 resection including R1c [n = 28 (70%)], R1d [n = 7 (18%)] or both [n = 5 (12%)]. After a mean of 28 (0-97) months, comparisons of R1 with R0 resection were as follows: mortality 10% and 4% (NS), overall recurrence 48% and 19% (P < 0.001), 2-year disease-free survival rate 51% and 76% (P < 0.001) and overall survival (OS) rate 91% and 96% (NS). For R1c patients mortality was 14% (4% for R0; P = 0.026), overall recurrence 46% (19% for R0; P = 0.028) and 2-year OS 88% (96% for R0; P = 0.025). No significant differences were found between R1d and R0. The metastatic recurrence rate was greater in R1c then R0 (29% vs 12%; P = 0.036) but not for R1d (14% vs 12%; NS). Locoregional recurrence rates of R1c (7%) and R1d (0%) were similar to R0 (4%).

CONCLUSION

This study shows that the poorer prognosis observed after R1 resection for rectal cancer is due to circumferential rather than distal involvement. This is mainly related to a higher rate of metastatic recurrence.

Risk factors for circumferential R1 resection after neoadjuvant radiochemotherapy and laparoscopic total mesorectal excision: a study in 233 consecutive patients with mid or low rectal cancer

PURPOSE

This study aimed to identify risk factors for circumferential R1 resection (R1c) after neoadjuvant radiochemotherapy (RCT) and laparoscopic total mesorectal excision (TME) for mid or low rectal cancer. Better knowledge of pre- or intraoperative risk factors could possibly help for the management of these patients.

METHODS

Between 2005 and 2013, 233 consecutive patients undergoing laparoscopic TME for low or mid rectal cancer after RCT were included. R1c resection was defined as a circumferential margin ≤ 1 mm. Univariate and multivariate analyses were performed to identify independent risk factors for R1c.

RESULTS

Twenty-five patients had R1c resection (11%). In univariate analysis, low rectal cancer, anterior tumour, T4 on pretherapeutic magnetic resonance imaging (MRI), T4 and/or N+ on post-RCT MRI and operative time > 240 min were associated with a significantly increased risk of R1c resection. In multivariate analysis, only T4 on post-RCT MRI (odds ratio (OR) = 6.02 [1.06-33]; p = 0.043) and operative time >240 min. (OR = 5.4 [1.01-28.9]; p = 0.049) were identified as independent risk factors for R1c resection. The risk of R1c resection was 3% (n = 3/88), 10% (n = 5/51) or 38% (n = 3/8) when 0, 1 or 2 risk factors were present in the same patient, respectively.

CONCLUSION

Patients with T4 on MRI after RCT and/or operative time >240 min. seems to be at higher risk for R1c resection. In a pragmatic approach, we consider that systematic second MRI after RCT could help the surgeon, especially in area where circumferential margin is too short, in order to reduce this risk of R1 resection.

OCT-based arterial elastography: robust estimation exploiting tissue biomechanics

We present a novel multi-resolution variational framework for vascular optical coherence elastography (OCE). This method exploits prior information about arterial wall biomechanics to produce robust estimates of tissue velocity and strain, reducing the sensitivity of conventional tracking methods to both noise- and strain-induced signal decorrelation. The velocity and strain estimation performance of this new estimator is demonstrated in simulated OCT image sequences and in benchtop OCT scanning of a vascular tissue sample.

Thalamic lesions dissociate breathing inhibition by hypoxia and adenosine in fetal sheep

The effects of diencephalic lesions on respiratory responses to intra-arterially infused adenosine (ADO) were determined in chronically catheterized fetal sheep (>0.8 term). These studies were designed to test the hypothesis that the inhibitory effects of ADO on fetal breathing, like those of hypoxia, are mediated by the parafascicular nuclear complex (Pf) of the posteromedial thalamus. ADO inhibited breathing [control (C): 26 +/- 2.6, ADO: 4 +/- 1 min/h] in normal fetuses and in a fetus with a lesion that virtually destroyed the thalamus but left intact most of Pf. Neuronal lesions in the diencephalon, produced by injecting ibotenic acid, abolished the inhibitory effects of ADO on breathing (C: 31 +/- 5.1, ADO: 30 +/- 4.5 min/h) when the lesions encompassed Pf or the sector immediately rostral to Pf that retained the capacity to regulate hypoxic inhibition. Smaller lesions created by the insertion of needles also eliminated the depressant effects of ADO when disruptions were within Pf or a rostral component of the thalamic cortical activating system. It is concluded that 1) a medial thalamic sector is critically involved in ADO-induced apnea and 2) ADO-dependent and ADO-independent mechanisms mediate hypoxic inhibition.

Metabolic and cardiorespiratory responses to hypoxia in fetal sheep: adenosine receptor blockade

8-Phenyltheophylline (PT), a potent and specific inhibitor of adenosine receptors, was infused intra-arterially into unanesthetized fetal sheep to determine the role of adenosine in hypoxic inhibition of fetal breathing. PT in normoxic fetuses increased heart rate and the incidence of low-voltage electrocortical activity, rapid eye movements (REM), and breathing. Mean breath amplitude increased by 44%. Hypoxia (preductal arterial PO2 = 14 Torr) induced a metabolic acidemia, a transient bradycardia, and hypertension while virtually eliminating REM and breathing. PT administration during hypoxia enhanced the metabolic acidemia, blocked the bradycardia and hypertension, increased the incidence of REM and breathing, and elevated mean breath amplitude. The results indicate that 1) adenosine is involved in fetal glycolytic and cardiovascular responses to hypoxia, 2) activation of central adenosine receptors mediates about one-half the inhibitory effects of hypoxia on REM and breathing, and 3) the depression of breathing may critically depend on a hypoxia-induced reduction in phasic REM sleep.

Adenosine modulates corticotropin and cortisol release during hypoxia in fetal sheep

OBJECTIVE

This study was designed to determine the role of adenosine in the hypoxic release of corticotropin in fetal sheep.

STUDY DESIGN

The adenosine receptor antagonist 8-phenyltheophylline or the vehicle was infused intra-arterially to chronically catheterized fetal sheep (>0.8 term) during an hour of fetal hypoxemia (Pa O 2 congruent with 14 mm Hg). Control studies were also performed in which 8-phenyltheophylline or the vehicle was administered to normoxic fetuses.

RESULTS

8-Phenyltheophylline abolished hypoxia-induced bradycardia and hypertension and produced a nearly 5-fold greater rise in fetal plasma concentrations of corticotropin and approximately a 3-fold greater increase in plasma cortisol levels. During normoxia 8-phenyltheophylline increased plasma cortisol concentrations by 2-fold without altering corticotropin levels, mean arterial blood pressure, or heart rate.

CONCLUSION

Adenosine blunts fetal corticotropin release during hypoxia, which in turn reduces cortisol secretion. At lower corticotropin concentrations, adenosine also appears to dampen the cortisol response through direct effects on the adrenals.

Thalamic locus mediates hypoxic inhibition of breathing in fetal sheep

The effects of lesions rostral to the brain stem on breathing responses to hypoxia were determined in chronically catheterized fetal sheep (>0.8 term). These studies were designed to test the hypothesis that the diencephalon is involved in hypoxic inhibition of fetal breathing. As in normal fetuses, hypoxia inhibited breathing with transection rostral to the thalamus or transection resulting in virtual destruction of the thalamus but sparing most of the parafascicular nuclear complex. Neuronal lesions were produced in the fetal diencephalon by injecting ibotenic acid through cannulas implanted in the brain. Hypoxic inhibition of breathing was abolished when the lesions encompassed the parafascicular nuclear complex but was retained when the lesions spared the parafascicular nuclear region or when the vehicle alone was injected. A new locus has been identified immediately rostral to the midbrain, which is crucial to hypoxic inhibition of fetal breathing. This thalamic sector involves the parafascicular nuclear complex and may link central O2-sensing cells to motoneurons that inhibit breathing.

Rapid tolerance and crosstolerance to motor impairment effects of benzodiazepines, barbiturates, and ethanol

Motor impairment (tilt-plane test) test was used to assess the phenomenon of rapid tolerance and crosstolerance to benzodiazepines, barbiturates, and ethanol. The motor impairment responses to benzodiazepines (chlordiazepoxide and diazepam) and to various barbiturates (pentobarbital, phenobarbital, and barbital) were significantly reduced on day 2 in rats that had been treated on day 1 with benzodiazepines and barbiturates, respectively, compared to the control group treated with saline on day 1. Benzodiazepine treatment on day 1 resulted in rapid crosstolerance to the motor impairment effects of ethanol on day 2. Benzodiazepine treatment, however, did not result in rapid crosstolerance to the three barbiturates (pentobarbital, barbital, and phenobarbital) tested. In contrast to the lack of rapid crosstolerance to barbiturates after treatment with benzodiazepines, barbiturate treatment clearly conferred rapid crosstolerance to benzodiazepines and to ethanol. This asymmetry of rapid crosstolerance raises the possibility that benzodiazepines and barbiturates invoke tolerance by mechanisms that are not wholly identical. Therefore, tolerance to the broad range of actions of barbiturates would include crosstolerance to the effects of benzodiazepines, whereas tolerance to benzodiazepines would include only a weak or partial crosstolerance to some of the effects of barbiturates.

Fetal cardiovascular and breathing responses to an adenosine A2a receptor agonist in sheep

CGS-21680 (CGS), a highly selective adenosine A2a receptor agonist, may excite the fetal carotid bodies. This study was designed to determine 1) whether CGS stimulates fetal breathing and 2) whether sinoaortic denervation abolishes CGS-induced tachycardia. In eight intact fetuses (> 0.8 term), intra-arterial CGS infusion (6 micrograms.min-1.kg estimated fetal wt-1) increased mean arterial PCO2 by 3-7 Torr, reduced fetal arterial PO2 by 2-5 Torr, and produced a mild metabolic acidemia. Heart rate increased from 154 +/- 7 (control) to 249 +/- 12 beats/min, but mean arterial pressure was not significantly affected. CGS initially increased the frequency, amplitude, and incidence of fetal breathing, but this hyperpnea was followed by prolonged respiratory depression that was not reversed with blockade of adenosine A1 receptors. Denervation of both carotid bodies together with interruption of the vagi abolished the hyperpnea without altering the respiratory depression or the maximum rise in heart rate. We conclude that CGS induces 1) tachycardia by a mechanism independent of the peripheral arterial chemoreceptors, 2) hyperpnea by stimulating peripheral adenosine A2a receptors, and 3) respiratory depression by activating central A2a receptors.

Effect of NMDA antagonists on development of rapid tolerance to various barbiturates

We recently reported that the noncompetitive antagonists, (+)-MK-801 and ketamine, block the development of rapid tolerance to ethanol. We now show that pretreatment with these NMDA antagonists also blocks rapid tolerance to the various barbiturates (pentobarbital, barbital, and phenobarbital) examined. Tolerance to pentobarbital occurred under three difference conditions: (a) in groups of rats that were tested at repeated times on day 1 (intoxicated practice or testing group), (b) in groups of rats that were not tested on the apparatus but handled at the same times on day 1 (dummy testing or associative learning group), and (c) in groups of rats that were not subjected to testing at all on day 1 (nontesting). However, NMDA antagonists blocked intoxicated practice and associative tolerance, but not tolerance produced in the nontesting group. In the last experiment NMDA antagonist failed to block tolerance (unlearned) when animals were treated in the animal quarters and tested in a different room (i.e., in the laboratory). These findings suggest that NMDA antagonists affect barbiturate tolerance in a manner similar to their effect on ethanol tolerance.