Infrared thermographic assessment of spinal anaesthesia-related cutaneous temperature changes during caesarean section.

INTRODUCTION: Assessment of adequacy of spinal anaesthesia, prior to obstetric surgery is extremely important but can be problematic because currently available clinical assessment methods are indirect and subjective. As the sympathectomy associated with spinal anaesthesia is known to cause vasodilation and heat redistribution, we sought to assess whether spinal anaesthesia led to significant and consistent cutaneous temperature changes as measured by infrared thermography. METHODS: Following ethics committee approval, this observational study was conducted in a tertiary level obstetric centre. Participants included women undergoing elective caesarean section under spinal anaesthesia. Following consent, a Flir T540 infrared camera captured thermographic images over the feet, patella, buttock, iliac crests, xiphisternum and axilla. Temperature was measured prior to spinal needle insertion (T0) and following clinical assessment when the block was deemed adequate. RESULTS: Thirty patients were included. Baseline temperature varied considerable by site. Spinal anaesthesia altered skin temperature in all areas of interest: right and left hallux (mean of differences (MD) +4.0°C and 5.2°C respectively, P <0.0001), right and left plantar (MD +6.1°C and 6.8°C respectively, P <0.0001), patella (MD -0.33°C, P=0.0445), buttock (MD -0.5°C, P=0.009), iliac crest (MD -0.7°C, P=0.0004), xiphisternum (MD -0.95°C, P <0.0001) and axilla (MD -0.71°C, P=0.0002). CONCLUSIONS: Following spinal anaesthesia thermographic imaging identified different patterns of skin temperature changes, with pronounced temperature increases measured in the feet and cooling of a lesser amplitude in the thoracic and lumbar dermatomes. Infrared thermography has the potential to provide objective measurement of sympathectomy.

Accuracy of cricothyroid membrane identification using ultrasound and palpation techniques in obese obstetric patients: an observational study.

BACKGROUND: During performance of emergency front of neck access, the final step in management algorithms for the 'can't intubate, can't oxygenate' scenario, accurate identification of the cricothyroid membrane is crucial. Accurate identification using palpation techniques is low, with highest failure rates occurring in obese females. METHODS: This prospective observational study recruited 28 obese obstetric patients. The cricothyroid membrane was identified using ultrasound, marked with an ultraviolet pen and covered with a dressing. The candidate was asked to perform cricothyroid membrane identification using landmark technique (group L) followed by ultrasound (group U). The primary outcome was the distance between the actual and estimated cricothyroid membrane midpoint. Secondary outcomes were the proportion of accurate assessments, time taken, and subjective ease of identification using a visual analogue score. RESULTS: Distance from the cricothyroid membrane midpoint was shorter in group U than Group L (2.5 mm vs 5.5 mm, P=0.002). The proportion of correctly identified cricothyroid membranes was greater in group U than group L (71% vs 39%, P=0.015). Time required for identification was shorter in group L than group U (16.9 s vs 23.5 s, P=0.001). Visual analogue scores for ease of identification were lower in group U than group L (2.4 cm vs 4.2 cm, P=0.013). CONCLUSIONS: Ultrasound-guided cricothyroid membrane localisation was significantly more accurate but slower than the landmark technique in obese obstetric patients. As such, we recommend the use of pre-procedural identification of the cricothyroid membrane in this patient population and formal training of anaesthetists in airway ultrasound.

Anaesthetic management of an emergency caesarean section in a complex immunologically compromised patient with pre-eclampsia and multifactorial thrombocytopaenia.

A 35-year-old gravida 3, para 0 woman required an emergency caesarean section for pre-eclampsia with severe features including a platelet count of 7 × 109.l-1. The patient's thrombocytopaenia was an acute on chronic presentation. In addition to pre-eclampsia, the patient had a complex background history which included autoimmune lymphoproliferative syndrome, the manifestations of which include autoimmune cytopaenias and recurrent infections. The patient also had common variable immune deficiency and acquired C1-esterase inhibitor deficiency which may cause life-threatening angioedema, including of the airway. In this report, we describe the potential anaesthetic challenges posed by this pre-eclamptic, immunologically compromised patient with severe thrombocytopaenia and the potential for difficult airway, and how these were addressed in a safe and timely manner. Specifically, we highlight the important considerations when performing a general anaesthetic in this unique combination of circumstances. Although the patient's conditions are rare, this case demonstrates that early multidisciplinary team input can help successfully guide the management of medically complex pregnant patients.

Emergency cricothyroidotomy: an observational study to estimate optimal incision position and length.

BACKGROUND: A vertical incision is recommended for cricothyroidotomy when the anatomy is impalpable, but no evidence-based guideline exists regarding optimum site or length. The Difficult Airway Society guidelines, which are based on expert opinion, recommend an 80-100 mm vertical caudad to cephalad incision in the extended neck position. However, the guidelines do not advise the incision commencement point. We sought to determine the minimum incision length and commencement point above the suprasternal notch required to ensure that the cricothyroid membrane would be accessible within its margins. METHODS: We measured using ultrasound, in 80 subjects (40 males and 40 females) without airway pathology, the distance between the suprasternal notch and the cricothyroid membrane, in the neutral and extended neck positions. We assessed the inclusion of the cricothyroid membrane within theoretical incisions of 0-100 mm in length made at 10 mm intervals above the suprasternal notch. RESULTS: In the 80 subjects, the distance ranged from 27 to 105 mm. Movement of the cricothyroid membrane on transition from the neutral to extended neck position varied from 15 mm caudad to 27 mm cephalad. The minimum incision required in the extended position was 70 mm in males and 80 mm in females, commencing 30 mm above the suprasternal notch. CONCLUSIONS: An 80 mm incision commencing 30 mm above the suprasternal notch would include all cricothyroid membrane locations in the extended position in patients without airway pathology, which is in keeping with the Difficult Airway Society guidelines recommended incision length.

Anaesthetic management for caesarean section of a parturient with a known difficult airway and closed spinal dysraphism.

Many anaesthetists consider patients with existing neurological deficits, untreated spinal pathology or those having undergone major spinal intervention to be precluded from undergoing neuraxial anaesthesia. While this is partly rooted in fears of litigation there is also a lack of consensus of the best practice in the anaesthetic management of these patients. We present our management of a parturient who attended our institution, having a number of anaesthetic complexities including a known difficult airway, spinal fusion and persistent spinal cord tethering. She successfully underwent delivery under neuraxial blockade for the delivery of her fourth child. We believe that by undergoing a thorough multidisciplinary clinical evaluation, including the extensive use of neuroimaging and ultrasound, it may be possible to plan and perform safe neuraxial anaesthesia.

Theoretical optimal cricothyroidotomy incision length in female subjects, following identification of the cricothyroid membrane by digital palpation.

BACKGROUND: Misidentification of the cricothyroid membrane is frequent in females, placing them at risk of difficult or failed cricothyroidotomy in the event of failed oxygenation. If anatomy is impalpable, the current guidelines of the Difficult Airway Society, based on expert opinion, recommend an 8-10 cm vertical incision to facilitate access to the cricothyroid membrane. At present no evidence-based guideline exists regarding optimum site or length. We investigated the likelihood of inclusion of the cricothyroid membrane, within hypothetical vertical midline incisions, in a female population. METHODS: We asked clinicians to identify the cricothyroid membrane in both the neutral and extended head positions using palpation, the point identified acting as the theoretical midpoint of a cricothyroidotomy incision. We then identified the cricothyroid membrane using ultrasound. We determined the minimum incision length that would be required to ensure that the cricothyroid membrane lay within its boundaries, if clinician digital palpation was the method of cricothyroid membrane localisation. RESULTS: Ninety female subjects were recruited. Theoretical incisions of 7 and 8 cm were required for successful cricothyroidotomy in the neutral and extended head positions respectively. This was necessary because of the high failure rate of cricothyroid membrane identification (80.9%) and the wide range of error (7.2 cm in a vertical plane). CONCLUSIONS: Based on clinical estimation of the location of the cricothyroid membrane, an incision length of 8 cm, using the clinician's best estimate as its midpoint, would overlie all cricothyroid membrane locations. Our data support the current Difficult Airway Society guidelines for cricothyroidotomy incision length.

Laryngeal handshake technique in locating the cricothyroid membrane: a non-randomised comparative study.

BACKGROUND: Evaluation of the anterior neck anatomy is used to identify the cricothyroid membrane (CTM) before front of neck airway access. This has been traditionally performed using palpation which results in misidentification of the CTM in a high proportion of subjects. The 'laryngeal handshake' is currently advocated by the Difficult Airway Society as the method to identify the CTM. We sought to investigate the accuracy of this technique in females. METHODS: Five clinicians were asked to identify the CTM using the 'laryngeal handshake' technique in a total of 45 anaesthetised females (Group L) and by conventional palpation in 45 controls (Group P). We measured and analysed the distance to actual CTM using ultrasound, the time to identification, and perceived difficulty using a visual analogue scale. RESULTS: Successful identification of the CTM occurred in 28/45 (62%) patients in Group L vs 15/45 (33%) in Group P [P=0.006; mean difference, 29%; 95% confidence interval (CI), 21-39%]. Distance to the CTM (P=0.012) and visual analogue scale (P=0.012) were significantly reduced in Group L. Mean time to CTM identification was greater in Group L at 31 (5.6) s, compared with Group P, which took 18 (5.5) s (P<0.001). The midline was accurately identified more frequently in Group L than in Group P (39/45 vs 28/45, P=0.008). CONCLUSIONS: The 'laryngeal handshake' method of palpation is more accurate but takes longer than conventional palpation technique in locating the CTM and the midline. This is of particular relevance if a vertical incision is required to perform front of neck access when anatomy is indistinct.

Ultrasonographic evaluation of gastric contents in term pregnant women fasted for six hours.

BACKGROUND: Current fasting guidelines suggest six hours are adequate to minimise the aspiration risk after a light meal consumed by pregnant women undergoing elective caesarean section. We assessed gastric contents in non-labouring pregnant women, using ultrasonographic analysis. METHODS: In a prospective study, pregnant women ≥36 weeks' gestation, without conditions likely to influence gastric emptying, underwent ultrasonographic analysis of their gastric antrum, after six hours of fasting following a standardised light meal. The primary outcome was solid food content in the antrum. Other outcomes included fluid in the supine and right lateral positions, antral cross-sectional area and estimated residual gastric fluid volume. Antral grades were classified: grade 0 = absence of fluid in both supine and right lateral positions: grade 1 = fluid present in the right lateral position only: grade 2 = fluid in both positions. RESULTS: Complete data were available in 46/51 (90%) women. No woman had solid food visible. Antral grades 0, 1 and 2 were seen in 6 (13%), 36 (78%) and 4 (9%) women respectively. Eighteen of 48 women (37.5%) had a residual volume greater than 1.5 mL/kg. Of those with a grade 1 antrum, 13/36 (36%) had residual volumes in excess of 1.5 mL/kg. For grade 2, this was 4/4 (100%). CONCLUSIONS: Our cohort of pregnant women fasted for six hours had no solid food visible in the antrum, but many had both qualitative and quantitative ultrasonographic evidence of gastric volumes potentially associated with aspiration risk. This suggests that pregnancy-specific fasting guidelines may be required.

Preferences of Jehovah's Witnesses regarding haematological supports in an obstetric setting: experience of a single university teaching hospital.

BACKGROUND: Jehovah's Witnesses have been shown to be at increased risk of mortality and morbidity as a consequence of obstetric haemorrhage and refusal of blood products. Since 2004, however, Jehovah's Witnesses have been allowed to accept minor fractions of blood at their own discretion. We sought to determine the preferences of pregnant Jehovah's Witnesses regarding haematological supports since this policy change. METHODS: This is a retrospective observational study of consecutive Jehovah's Witnesses attending a university-affiliated tertiary referral centre between 1 January 2007 and 31 December 2013. The main outcome measure was the proportion of women who would be willing to accept blood products and other haematological supports in the event of life-threatening bleeding, should it occur. RESULTS: Seventy-six Jehovah's Witnesses attended for obstetric care during the study period. Major fractions of blood (red cells, plasma or platelets) were acceptable to 7.9% and 50% would accept some minor fractions. Some blood components were acceptable to 70.3% of nulliparous women compared to 48.9% of multiparous women. In women with advance directives some blood components were acceptable to 70.5% compared with 37.5% of those without. Recombinant factor VIIa was acceptable to 53.9%. Black African women had the lowest acceptance of any ethnic group of any blood products. CONCLUSION: The spectrum of acceptance of blood products is wide ranging within our obstetric Jehovah's Witnesses population. Recombinant factors are not universally acceptable despite their identification as non-blood products. A multidisciplinary approach with individualized consent is recommended.

Spinal dysraphisms in the parturient: implications for perioperative anaesthetic care and labour analgesia.

Anaesthetists may encounter parturients with a spectrum of anatomical and functional abnormalities secondary to spinal dysraphisms, which are among the most common neurodevelopmental anomalies. These range from surgically corrected open dysraphisms to previously undiagnosed closed dysraphisms. Both bony and neural structures may be abnormal. In true bony spina bifida, which occurs in up to 50% of the population, failure of fusion of the vertebral arch is seen and neural structures are normal. Ninety percent of such cases are confined to the sacrum. In open dysraphisms, sensory preservation is variable and may be present even in those with grossly impaired motor function. Both epidural and spinal blockade have been described for labour analgesia and operative anaesthesia in selected cases but higher failure and complication rates are reported. Clinical assessment should be performed on an outpatient basis to assess neurological function, evaluate central nervous system shunts and determine latex allergy status. Magnetic resonance imagining is recommended to clarify anatomical abnormalities and to identify levels at which neuraxial techniques can be performed. Of particular concern when performing neuraxial blockade is the possibility of a low-lying spinal cord or conus medullaris and spinal cord tethering. Previous corrective de-tethering surgery frequently does not result in ascent of the conus and re-tethering may be asymptomatic. Ultrasound is not sufficiently validated at the point of care to reliably detect low-lying cords. Epidurals should be performed at anatomically normal levels but spread of local anaesthetic may be impaired by previous surgery.

Evaluation of the effect of intra-operative intravenous fluid on post-operative pain and pulmonary function: a randomized trial comparing 10 and 30 ml kg(-1) of crystalloid.

BACKGROUND: Existing evidence suggests that administration of intravenous fluids has been shown to improve outcomes including pain in gynecological laparoscopic surgery but the optimum fluid dose has not been determined. AIMS: To determine the effect of administration of intravenous fluids on post-operative pain and pulmonary function after gynecological laparoscopy. METHODS: In a prospective randomized double-blinded study 100 ASA 1 and 2 elective patients undergoing gynecological laparoscopy were randomized to receive intravenous compound sodium lactate 10 ml kg(-1) (CSL10-restrictive) or 30 ml kg(-1) (CSL30-liberal) administered intra-operatively. The primary outcome measure was the post-operative pain score at 24, 48 and 72 h, assessed by 0-10 verbal rating scale (VRS). Pulmonary function (FEV1, FVC, PEFR) and oxygen saturation were also measured. RESULTS: Patients who received CSL 30 had lower post-operative pain scores than CSL 10 (ANCOVA-mean difference = 0.47, 95 % CI 0.11-0.83, P = 0.01). Post-operative pain VRS was lower in CSL30 than CSL10 at 48 h (mean difference 0.56, 95 % CI 0.04-1.09, P = 0.036). Patients in CSL30 reported shoulder tip pain less frequently than those in CSL10 (30.4 vs. 43.9 % of assessments, P = 0.03, OR 0.58) but reported wound pain more frequently 39.0 vs. 24.2 %, P = 0.01, OR 2.0). Indices of pulmonary function did not differ between groups at any time. CONCLUSIONS: Liberal compared to restrictive administration of i.v. crystalloid is associated with a clinical modest reduction in pain. Pulmonary dysfunction was not increased with liberal fluid administration.

Anatomical characterisation of the cricothyroid membrane in females of childbearing age using computed tomography.

BACKGROUND: In the event of failure to secure the airway by conventional means, it may be necessary to perform invasive airway access via the cricothyroid membrane. No studies have addressed anatomy of this structure in the obstetric population. We aimed to review the anatomical variation of this structure in a population of childbearing age. METHODS: We searched the radiology database for computed tomography studies of the neck performed in a 13-month period in consecutive patients aged 15-55 years. Studies on 18 females and 22 males were reviewed. Male patients were included for comparison. Data were reconstructed using a high spatial frequency algorithm to optimise spatial resolution. Five parameters were measured: distance from the skin to the membrane, maximum midline height of the membrane in the vertical plane, maximum transverse diameter of the membrane, neck diameter and cartilaginous calcification. RESULTS: The distance (mean range) from skin to the membrane was similar in females and males (16.2 [3-33] vs. 13.9 [3-37] mm, P = 0.42). The vertical height (9.9 [7-17] vs. 11.4 [8-15] mm, P = 0.04) and maximum width of the membrane (14.5 [10-17] mm vs. 12.5 [10-15] mm, P < 0.01) were greater in males. Cartilaginous calcification was low and did not differ between genders. CONCLUSIONS: The cricothyroid membrane is not necessarily a superficial structure and consequently may be difficult to palpate. The smallest dimensions of the membrane indicate that smaller than recommended cricothyroidotomy devices may be required in some patients as the external diameter of commercial trocar devices and tracheal tubes may exceed 7 mm.

Anaesthetic outcomes in obese parturients: the effect of assessment in the high-risk clinic.

BACKGROUND: Obese parturients are at high risk of complications during anaesthesia and early use of epidural analgesia in labour has been recommended for obese patients during labour. AIM: To assess the outcome of anaesthesia outpatient consultation for obese parturients. METHODS: We retrospectively compared outcomes of obese patients antenatally and an obese and non-obese control group over a 1-year period. Outcomes included potential airway problems, anaesthetic for caesarean section, use and success of epidural analgesia and cervical dilation at epidural placement. RESULTS: The proportion of obese patients who had predictable intubation difficulty was low (5%). Epidural use analgesia in labour (69 vs 36 vs 66%, P = 0.148) was similar between groups (obese, obese controls and non-obese controls, respectively). Cervical dilation at the time of epidural insertion in the obese group (2.0, 1.0-3.0 cm) was not different from obese controls (3.0, 1.75-5.75 cm). There was no difference in the number of attempts required to site the epidural between groups or the number of patients that required resiting of the epidural catheter. General anaesthesia was not required in any emergency case in this group. CONCLUSION: The outcomes of obese patients attending the anaesthetic clinic were mixed. Not all patients who were to advised have epidurals did so but those who did requested them in early labour and there was no requirement for general anaesthesia during emergency caesarean section and adverse airway events were avoided in this group.

Care of the migrant obstetric population.

Care of pregnant migrants is a considerable challenge for all health care workers and health systems. Maternal mortality and serious morbidity are both greatly increased among migrants in western countries, particularly in Africans and asylum seekers. While in many instances, migrants are healthier than native populations and have better perinatal outcomes, this is inconsistent and poorer outcomes are described in many groups. The causes of suboptimal outcomes are numerous and are strongly influenced by the health-seeking behaviour of the parturients. Accordingly, improvement in outcome requires a multifaceted approach with a focus on early access to antenatal services and enhanced medical screening and surveillance for detection and optimisation of comorbid conditions. Provision and/or acceptance of analgesia in labour have not been well researched but existing data are sufficient to suggest that some migrant groups do not receive equivalent pain relief during labour. Provision of information and translation services are important components in improvement of standards of care.

Comparison of transversus abdominis plane block vs spinal morphine for pain relief after Caesarean section.

BACKGROUND: Transversus abdominis plane (TAP) block is an alternative to spinal morphine for analgesia after Caesarean section but there are few data on its comparative efficacy. We compared the analgesic efficacy of the TAP block with and without spinal morphine after Caesarean section in a prospective, randomized, double-blinded placebo-controlled trial. METHODS: Eighty patients were randomized to one of four groups to receive (in addition to spinal anaesthesia) either spinal morphine 100 µg (S(M)) or saline (S(S)) and a postoperative bilateral TAP block with either bupivacaine (T(LA)) 2 mg kg(-1) or saline (T(S)). RESULTS: Pain on movement and early morphine consumption were lowest in groups receiving spinal morphine and was not improved by TAP block. The rank order of median pain scores on movement at 6 h was: S(M)T(LA) (20 mm)

Anaesthesia for caesarean section in a patient with Sturge-Weber syndrome following acute neurological deterioration.

Sturge-Weber syndrome consists of facial capillary malformation (port-wine stain) and abnormal blood vessels in the brain or eye. Seizures, developmental delay and intracranial and airway angiomata are principal concerns. We report a 28-year-old primiparous woman at 41 weeks of gestation with Sturge-Weber syndrome who developed unilateral weakness, aphasia, blurred vision and confusion. Preeclampsia was excluded. Neuroimaging showed left sided cerebral oedema and a right parieto-occipital lesion, most likely an angioma. Caesarean section was planned to avoid the risk of angioma rupture during labour. General anesthesia was avoided due to the haemodynamic response to laryngoscopy and reports of seizure-related mortality. Despite the possibility of raised intracranial pressure and precipitation of cerebral herniation, a lumbar epidural block was administered but failed. A subarachnoid block was successfully performed and a healthy infant delivered. The choice of anaesthesia was strongly influenced by detailed radiological investigations and multidisciplinary participation.