David G Bishop

Predicting spinal hypotension during Caesarean section

Hypotension under spinal anaesthesia for Caesarean section remains a common problem, with attendant maternal and foetal morbidity. This review examines some of the issues surrounding the prediction of spinal hypotension, including concerns about current evidence, the debate on the mechanism of hypotension and the utility of prediction in this group of patients. It then covers some of the more conventional and established preoperative predictors of hypotension. Particular attention is paid to the assessment of autonomic function and some of the novel methods being used as predictors of severe maternal hypotension. The implications of autonomic dysfunction and areas for future research are discussed.

Heart rate variability as a predictor of hypotension following spinal for elective caesarean section: a prospective observational study

Post‐spinal hypotension remains a common and clinically‐important problem during caesarean section, and accurate pre‐operative prediction of this complication might enhance clinical management. We conducted a prospective, single‐centre, observational study of heart rate variability in 102 patients undergoing elective caesarean section in a South African regional hospital. We performed Holter recording for ≥ 5 min in the hour preceding spinal anaesthesia. The low‐frequency/high‐frequency ratio component of heart rate variability was compared, using a logistic regression model, with baseline heart rate and body mass index (BMI) as a predictor of hypotension (defined as systolic arterial pressure < 90 mmHg) occurring from the time of spinal insertion until 15 min after delivery of the baby. We also assessed clinically relevant cut‐point estimations for low‐frequency/high‐frequency ratio. Low‐frequency/high‐frequency ratio predicted hypotension (p = 0.046; OR 1.478, 95%CI 1.008‐1.014), with an optimal cut‐point estimation of 2.0; this threshold predicted hypotension better than previously determined thresholds (p = 0.003; c‐statistic 0.645). Baseline heart rate (p = 0.20; OR 1.022, 95%CI 0.988‐1.057) and BMI (p = 0.60; OR 1.017, 95%CI 0.954‐1.085) did not predict hypotension. Heart rate variability analysis is a potentially useful clinical tool for the prediction of hypotension. Future studies should consider a low‐frequency/high‐frequency ratio threshold of 2.0 for prospective validation.

Vasoconstrictor clysis in burn surgery and its impact on outcomes: Systematic review and meta-analysis

AIM Clysis is the subcutaneous or subdermal injection of a vasopressor containing fluid, with or without local anaesthetic agent, and has been used to limit blood loss in patients undergoing surgical burn management. In this systematic review and meta-analysis we aimed to determine the impact of clysis of a vasoconstrictor on burn patient outcomes. METHODS We conducted a systematic review to identify trials investigating clysis in burn patients undergoing debridement and/or skin grafting. For each eligible trial we aimed to extract the outcomes of perioperative blood loss, blood transfusion, duration of surgery, graft success and healing time, inflammatory response, sepsis, mortality, duration of hospital stay, catecholamine levels and cardiovascular effects in both the short (<72h) and long term (30 days) after surgery. RESULTS From 443 citations, we selected 39 for full-text evaluation, and identified 10 eligible trials. Due to a lack of reporting on outcomes of interest, meta-analysis could only be conducted for the outcome of red blood cell (RBC) units transfused per patient. Patients receiving clysis (n=222) were transfused 1.89 less units (95% CI -2.12 to -1.66) as compared to those not receiving clysis, although this was associated with a high degree of heterogeneity (I(2)=88%). CONCLUSION Few studies have adequately evaluated the impact of clysis in burn surgery on patient important outcomes such mortality, duration of surgery and graft success. These results suggest clysis may reduce the need for blood transfusion but additional high quality research is required.

Heart rate variability predicts 30-day all-cause mortality in intensive care units

Background: Autonomic nervous function, as quantified by heart rate variability (HRV), has shown promise in predicting clinically important outcomes in the critical care setting; however, there is debate concerning its utility. HRV analysis was assessed as a practical tool for outcome prediction in two South African hospitals and compared with Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring. Method: In a dual centre, prospective, observational cohort study of patients admitted to the intensive care units (ICU) of two hospitals in KwaZulu-Natal, South Africa frequency domain HRV parameters were explored as predictors of: all-cause mortality at 30 days after admission; ICU stay duration; the need for invasive ventilation; the need for inotrope/vasopressor therapy; and the need for renal replacement therapy. The predictive ability of HRV parameters against the APACHE II score for the study outcomes was also compared. Results: A total of 55 patients were included in the study. Very low frequency power (VLF) was shown to predict 30-day mortality in ICU (odds ratio 0.6; 95% confidence interval 0.396–0.911). When compared with APACHE II, VLF remained a significant predictor of outcome, suggesting that it adds a unique component of prediction. No HRV parameters were predictive for the other secondary outcomes. Conclusion: This study found that VLF independently predicted all-cause mortality at 30 days after ICU admission. VLF provided additional predictive ability above that of the APACHE II score. As suggested by this exploratory analysis larger multi-centre studies seem warranted.

National priorities for perioperative research in South Africa

BACKGROUND Perioperative research is currently unco-ordinated in South Africa (SA), with no clear research agenda. OBJECTIVE To determine the top ten national research priorities for perioperative research in SA. METHODS A Delphi technique was used to establish consensus on the top ten research priorities. RESULTS The top ten research priorities were as follows: (i) establishment of a national database of (a) critical care outcomes, and (b) critical care resources; (ii) a randomised controlled trial of preoperative B-type natriuretic peptide-guided medical therapy to decrease major adverse cardiac events following non-cardiac surgery; (iii) a national prospective observational study of the outcomes associated with paediatric surgical cases; (iv) a national observational study of maternal and fetal outcomes following operative delivery in SA; (v) a stepped-wedge trial of an enhanced recovery after surgery programme for (a) surgery, (b) obstetrics, (c) emergency surgery, and (d) trauma surgery; (vi) a stepped-wedge trial of a surgical safety checklist on patient outcomes in SA; (vii) a prospective observational study of perioperative outcomes after surgery in district general hospitals in SA; (viii) short-course interventions to improve anaesthetic skills in rural doctors; (ix) studies of the efficacy of simulation training to improve (a) patient outcomes, (b) team dynamics, and (c) leadership; and (x) development and validation of a risk stratification tool for SA surgery based on the South African Surgical Outcomes Study (SASOS) data. CONCLUSIONS These research priorities provide the structure for an intermediate-term research agenda.

The appropriateness of preoperative blood testing: A retrospective evaluation and cost analysis

BACKGROUND Inappropriate preoperative blood testing can negatively contribute to healthcare costs. OBJECTIVE To determine the extent and cost implications of inappropriate preoperative blood testing in adult patients booked for orthopaedic, general or trauma surgical procedures at a regional hospital in KwaZulu-Natal Province, South Africa (SA). METHODS We undertook a retrospective observational study using routine clinical data collected from eligible patient charts. The appropriateness of preoperative blood tests was evaluated against locally published guidelines on testing for elective and non-elective surgery. The cost of the relevant blood tests was determined using the National Health Laboratory Service 2014 State Pricing List. RESULTS A total of 320 eligible patient charts were reviewed over a 4-week period. Preoperative blood testing was performed in 318 patients. There was poor compliance with current departmental guidelines, with an estimated over-expenditure of ZAR81,019. Non-compliance was particularly prevalent in younger patients, patients graded as American Society of Anesthesiologists 1 and 2, and low-risk surgery groups. CONCLUSION Inappropriate preoperative blood-testing is common in our hospital, particularly in low-risk patients. This is associated with an increase in healthcare costs, and highlights the need for SA doctors to become more cost-conscious in their approach to blood testing practices.

Difficult airways: a reliable “Plan B”

Abstract Percutaneous transtracheal jet ventilation (PTJV) is an accepted method of rescue ventilation following unsuccessful attempts to secure the airway through conventional methods. Pre-emptive use of PTJV in the difficult airway has also been described as using either a specifically designed jet ventilation catheter, or other cannulae, such as a central venous catheter (CVC). We report on the insertion of a single-lumen CVC to establish a means for PTJV or oxygen insufflation prior to induction of general anaesthesia in an 18-year-old man. He had an anticipated difficult airway and potentially difficult rescue airway access, having been booked for biopsy of neck masses and formal tracheostomy.

Perioperative ARDS and lung injury: for anaesthesia and beyond

Postoperative pulmonary complications are common and may be associated with significant cost. Acute respiratory distress syndrome (ARDS), a life-threatening respiratory disease process characterised by hypoxaemia and reduced lung compliance, is one of the more serious pulmonary complications. The development of ARDS or the related entity of lung injury is associated with prolonged hospitalisation, ventilation, and time spent in intensive care, and profoundly increases the risk of mortality and significant morbidity. Patients with, or at risk of ARDS and lung injury, must be identified, optimised and managed with sound intraoperative principles (particularly ventilation and fluid management) – with the specific aim of limiting harm. This review will focus on the diagnosis, pathophysiology, prevention and management of ARDS and lung injury in the perioperative period.

Maternal critical care in resource-limited settings. Narrative review

Maternal critical care reflects interdisciplinary care in any hospital area according to the severity of illness of the pregnant woman. The admission rate to intensive care units is below 1% (0.08-0.76%) of deliveries in high-income countries, and ranges from 0.13% to 4.6% in low- and middle-income countries. Mortality in these patients is high and varies from 0% to 4.9% of admissions in high-income countries, and from 2% to 43.6% in low- and middle-income countries. Obstetric haemorrhage, sepsis, preeclampsia, human immunodeficiency virus complications and tropical diseases are the main reasons for intensive care unit admission in low middle-income countries. Bedside assessment tools, such as early warning scores, may help to identify critically ill patients and those at risk of deterioration. There is a lack of uniformity in definitions, identification and treatment of critically ill pregnant patients, especially in resource-limited settings. Our aims were to (i) propose a more practical definition of maternal critical care, (ii) discuss maternal mortality in the setting of limited accessibility of critical care units, (iii) provide some accessible tools to improve identification of obstetric patients who may become critically ill, and (iv) confront challenges in providing maternal critical care in resource-limited settings. To improve maternal critical care, training programmes should embrace modern technological educational aids and incorporate new tools and technologies that assist prediction of critical illness in the pregnant patient. The goal must be improved outcomes following early interventions, early initiation of resuscitation, and early transfer to an appropriate level of care, whenever possible.

Preoperative predictors of thrombocytopenia in Caesarean delivery: is routine platelet count testing necessary?

Abstract Background: Peri-partum thrombocytopenia significantly impacts anaesthetic technique and increases the risk of perioperative bleeding. However, as less than 5% of normal pregnancies have significant thrombocytopenia, routine platelet testing incurs great cost for a relatively low yield. Determining whether clinical predictors, in particular HIV status, are associated with thrombocytopenia may assist clinicians in rationalising preoperative testing. Methods: This was a prospective, observational, single-centre study at a South African regional hospital. We evaluated five variables as candidate predictors for mild preoperative thrombocytopenia (< 150 000/μl) in patients scheduled for both elective and emergency Caesarean delivery: HIV status, pre-eclampsia, urgency of surgery, renal impairment and liver failure. As a sub-analysis we compared the incidence of moderate thrombocytopenia (< 100 000/μl) in HIV-positive patients, with HIV-negative patients. Results: We recruited 1 015 patients to this study. The incidence of mild thrombocytopenia was 10.3% (105/1 015). Only pre-eclampsia was predictive of mild thrombocytopenia (odds ratio 3.51; p < 0.01; 95% confidence interval 2.12–5.82). The incidence of moderate thrombocytopenia was not influenced by HIV status (occurring in 1.5% of HIV-positive patients versus 1.8% in HIV-negative patients; p = 0.716). Conclusions: In this study of predominantly asymptomatic patients scheduled for Caesarean delivery, only pre-eclampsia was predictive of mild thrombocytopenia. In sub-analysis HIV status was not independently associated with moderate thrombocytopenia. All asymptomatic patients, including those who were HIV positive, had platelet counts > 70 000/μl.